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© 2009 AOCS Press.
2
Avocado Oil
Allan Woolf1, Marie Wong3, Laurence Eyres2, Tony McGhie1, Cynthia
Lund1, Shane Olsson1, Yan Wang3, Cherie Bulley1, Mindy Wang1, Ellen
Friel4, and Cecilia Requejo-Jackman1
1HortResearch, The Horticulture & Food Research Institute of New Zealand Limited,
Auckland, New Zealand; 2Oil and Fats Group, N.Z. Institute of Chemistry, Auckland, New
Zealand; 3Institute of Food Nutrition and Human Health, Massey University, Albany,
Auckland, New Zealand. and 4 Diageo Baileys Global Supply, Nangor House, Nangor
Road, Dublin 12, Ireland.
73
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© 2009 AOCS Press.
Introduction
Avocado fruit are well-known, with millennia of consumption in the Americas and
an increasing popularity in the rest of the world. roughout history, avocado oil
was renowned for its healing and regenerating properties. Early writings from the
sixteenth century reported the use of the oil obtained from the seed to treat rashes
and scars (Argueta-Villamar et al., 1994). In skin care, the two major advantages of
avocado oil are its marked softening and soothing nature and its notable absorption.
For example, compared with almond, corn, olive, and soybean oils, avocado oil had
the highest skin-penetration rate (Swisher, 1988).
Avocado oil obtained from the esh (fruit), on the other hand, is a relatively new
arrival in culinary circles. e predominant uses of avocado oil are in the cosmetic in-
dustry because of its stability and high level of vitamin E (α-tocopherol). e volume
of avocado oil produced (or traded) is relatively small compared with other oils, with
2000 tonnes/year.
Avocado (Persea americana Mil.) is a subtropical tree which is relatively frost-
sensitive and grows to a height of 5–30 m (Scora et al., 2002). e eshy fruit are
borne yearly from the current seasons wood, and the green fruit ripen only after being
harvested. ey are grown in most countries of the world that are frost-free, and are
generally a “high input” crop requiring good horticultural management.
e bulk of avocado oil is extracted by relatively harsh methods (high tempera-
ture and solvent extraction), typically followed by standard rening steps (rening,
bleaching, and deodorizing). e development in the twenty-rst century was that of
successful cold-pressing of avocado fruit by using technologies similar to those used
to produce extra-virgin olive oil. is successful development was led by New Zea-
land, and its commercialization started in 2000. e demand for information by New
Zealand commercial entities has driven much of the research on cold-pressed avocado
oil, which we have published in various forms (e.g., Ashton et al., 2006; Wong et al.,
2008), and we present additional unpublished material here.
A. Woolf et al.
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© 2009 AOCS Press.
Avocado oil is generally produced from fruit rejected from the fresh-fruit trade—
either domestic or export-oriented— depending on the country. is is signicantly
dierent from olive or palm oils (grown and harvested solely for oil production) or
from other oils produced from processing by-products (e.g., rice- bran oil). e ulti-
mate market of the oil generally dictates the fruit quality required. For the production
of good-quality cold-pressed oil, the fruit must be relatively “sound” with mainly
cosmetic-quality issues or too small for sale. For cosmetic-oil production, one can
use poor-quality rejected fruit (often with rots), although subsequent rening is re-
quired.
e cultivar Hass accounts for over 90% of total production in many large av-
ocado-producing countries including Mexico, Chile and the United States, and this
is also the case in other smaller producer countries (e.g., New Zealand, Spain, and
Australia; Avocadosource, 2006). For this reason, Hass is the most likely cultivar to
be used for avocado oil production. e other important cultivars grown worldwide
in approximate order of priority include Fuerte, Ryan, Pinkerton, and Edranol. How-
ever, one must note that information is lacking on the cultivar diversity of large por-
tions of avocado production, such as in Indonesia (the fourth-largest producer of
avocados).
Overall, limited published information exists on avocado oil, and even less on
cold-pressed avocado oil. Cold-pressed avocado oil (on which this chapter concen-
trates) is a new product with signicant production, commercialization, and market-
ing only occurring in the twenty-rst century. us, we include here information
which is unpublished or not readily accessible. Some of these results are preliminary
in nature, but provide important perspectives and point to research needs or com-
mercial directions.
Applications and Economics
Cosmetic Applications
Although reliable data are not available for production and international trade of oil,
the U.S. volume is said to be around 1000 tonnes. e main use for this trade is the
cosmetics industry, where it is highly valued for its benecial eects on the skin. For
its use in cosmetics, crude avocado oil is further processed (rened, bleached. and
deodorized: RBD). e resulting oil is pale yellow (instead of green) and has little re-
maining avocado odor or taste (Eyres et al., 2001). e rened oil is used in skin- care
products since it is rapidly absorbed by the skin, and has sunscreen properties (Hu-
man, 1987; Swisher, 1988). Avocado oil is claimed to be good for tissue and massage
creams, muscle oils, and other products where lubrication and penetration are essen-
tial, as it is one of the most penetrating oils available for cosmetics and soaps. It also
forms ner emulsions because it reduces surface tension (Poucher, 1974). It is used in
soaps to provide improved lathering, and it forms smoother creams (Human, 1987).
Avocado Oil 75
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Culinary Applications
Cold-pressed avocado oil has chemical properties similar to olive oil. At least 60% of
the fatty acids are monounsaturated, and approximately 10% are polyunsaturated. In
addition, cold-pressed avocado oil contains relatively high levels of pigments (chloro-
phylls and carotenoids) which act as antioxidants. e global trend of high-spending
consumers is toward the consumption of fewer processed products because of contro-
versy about the linkage of some chemicals with human diseases. is is reected in the
increase in the consumption of cold-pressed olive oil in the United Kingdom, where
sales increased from 43% in 2005 to 51% of the total market (Mintel Report 2005
cited by Fletcher, 2006). Cold-pressed avocado oil appeals to the consumer looking
for a delicate buttery avor without the pungent notes of extra-virgin olive oil. In ad-
dition, avocado oil has a high smoke point (over 250°C) which makes it suitable for
shallow pan frying. Currently, the oil retails at approximately US$5 per bottle (250
mL) on the New Zealand market and at a comparable price in Australia. Bulk avo-
cado oil sales are at US$10 per liter and are increasing as U.K. and U.S. users become
aware of the reliable supply (Eyres et al., 2001).
Economics
e business model of the avocado oil industry in almost all countries relies on using
“reject grade” fruit (low-price rated) from commercial packhouses, which have not
met export or local-market quality standards. Generally, the grower does not receive
a large economic benet (in terms of price/kg of fruit). However, the removal of this
“bottom” class of fruit from the local market does result in signicant indirect benets
to growers by increasing the local-market price due to reduced fruit volumes.
Initial technical and market studies by New Zealand entrepreneurs showed that
a premium avocado oil could achieve high market prices. Further research showed
that avocado plantations in the main- producer countries are young and production
volumes are increasing, and thus the volumes of undergrade fruit will consequently
increase substantially (Requejo-Tapia, 1999). In addition, both a study of the market
for edible oils and the changes in consumer preferences for healthier oils show an in-
crease in consumption and a willingness to pay a premium price for alternatives to the
standard oils (Mintel Report 2005 cited by Fletcher, 2006). In the United Kingdom
alone, sales of all edible liquid oils are expected to rise in both value and volume, with
the value of the market rising some 11% by 2010 to just under US$420 million. Avo-
cado oil production is limited and specialized; therefore, it is considered a specialty
oil. is means that avocado oil enjoys a high-value market.
Plant Establishment and Oil-Yield Economics
e approximate cost of establishing an avocado oil processing plant is valued at
US$1 million (Nathan, 2006). e processing equipment should be stainless-steel,
A. Woolf et al.
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state-of-the-art processing and bottling plants to achieve high food-grade quality
standards. Avocado fruit need to be ripened to obtain maximal oil yield; yet they are
highly perishable, with a signicant propensity for rot development as fruit ripen.
is means that a challenge exists in establishing the infrastructure and experience
of handling, storing, and ripening avocados in a predictable and robust manner that
minimizes fruit losses and rots. During processing, the skin and seeds are removed,
and the oil is extracted from the esh. Typical oil yields can vary from 10 to 15% of
total fruit weight, depending on the time of harvest.
Overview of the Cold-pressed Avocado Oil Industry
In the eight years since the rst cold-pressed processing facility was set up in New
Zealand, the avocado oil industry has grown relatively slowly. Numerous reasons may
explain the slow expansion of the avocado oil industry. Firstly, because avocado oil is
a side-industry of the fresh-fruit industry, the volume of fruit available for process-
ing suers signicant annual uctuations. is has occurred in Mexico, for instance
(where high domestic consumption occurs), and extraction plants were mothballed
during some years. In New Zealand annual oil production, gures varied signicantly
because of climate eects on fruit set and thus nal production gures. Secondly, sig-
nicant competition exists for fruit to be used for other processed products, such as
guacamole produced by using either freezing or, more recently, high-pressure process-
ing (San Martín et al., 2002), particularly in the main- producer countries.
If one considers the relative importance of countries by the volume of avocado
traded (Wong et al., 2008), then countries such as Mexico, Chile, and the United
States are the most important. However, also many other countries exist where large
volumes of avocado are grown (e.g., Indonesia and Africa), yet these countries do not
trade signicant quantities. Countries such as these and small islands (e.g., the Pacic
Islands or Haiti) might well contain signicant under-utilized sources of fruit for oil
processing. However, commercial feasibility is often a problem in these situations,
and aid/development money may be required from donors such as the UN, FAO,
and/or commercial partnerships.
Avocados are a high-input crop from a horticultural perspective, and because of
this no orchards were dedicated solely to growing fruit for oil production. However,
such a venture might be economically feasible if one can nd a cultivar that produces
very high oil yields and/or is of particularly high health-value because of higher levels
of healthful phytochemicals (such as tocopherols, sterols, or carotenoids).
Overview of Avocado: Fruit Physiology
and Postharvest Ripening
Avocado Fruit Growth and Harvest
Avocados are one of the few fruits, other than olives, that accumulate signicant
amounts of oil, and in some situations contain even more oil than olives. Avoca-
Avocado Oil 77
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do fruit consist of an exocarp or skin, the esh (mesocarp), and the seed (stone or
pit). Depending on the cultivar, the edible esh makes up 50–80% of the total fruit
weight, while the seed comprises 10–25% (Lewis, 1978). e seed is covered by two
thin seed coats adhering to each other, and the woody seed is made up of two coty-
ledons made of starch-rich parenchyma tissue containing scattered oil droplets (Biale
& Young, 1969).
Avocado-fruit development on the tree involves increased size and lipid content
in the esh tissue, while the moisture content decreases (Appleman, 1969; Hopkirk,
1989; Kikuta & Erickson, 1968; Lawes, 1980; Pearson, 1975). Avocados are unusual
in that cell replication continues during development, whereas most other fruit-de-
velopment patterns involve initial cell division and then, water-driven, increase in size
approaching harvest (Schroeder, 1953). Lipids and water are the two major compo-
nents of a mature avocado. Oil content in commercially mature avocados can range
between 10 and 32% on a esh fresh weight basis, depending on the cultivar and the
time of harvest. For Hass avocados, this can be as high as 30% on a esh fresh weight
basis, depending on the growing region (Kaiser et al., 1992; Requejo-Tapia, 1999).
e total oil content in the fruit increases during fruit development on the tree (Fig.
2.1).
Signicantly, the level of oil and the fatty- acid composition do not change dur-
ing ripening after the fruit are harvested (Luza et al., 1990). Similarly, no changes in
1 Sep
21 Sep
11 Oct
31 Oct
20 Nov
10 Dec
30 Dec
19 Jan
8 Feb
28 Feb
20 Mar
9 Apr
29 Apr
19 May
14
16
18
20
22
24
26
28
30
32
34
36
38
Dry Matter: Te Puke
Total Lipids: Te Puke
Lipid Content or Dry Matter (% fresh weight)
Harvest date
Fig. 2.1. Mean lipid (oil) content and dry matter of Hass avocado fruit harvested over a
commercial season from one New Zealand orchard in 1998–1999. Each point is the aver-
age of four replicates of ve fruits. Vertical bars are the standard errors of the mean.
A. Woolf et al.
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fatty acid composition and concentration were observed at storage temperatures of
0–7°C for 2–6 weeks nor during subsequent ripening (Eaks, 1990; Kikuta & Erick-
son, 1968; Luza et al., 1990). ese results were observed in the two key commercial
cultivars Hass and Fuerte, and likely, similar results would be observed in other culti-
vars.
In the avocado esh, the lipids are stored in two cell types: the parenchyma cells
and in specialized oil cells or idioblasts. Approximately 85% of the total lipids present
in an avocado are present as triglycerides, which occur as droplets or oil bodies scat-
tered in the cytoplasm of the parenchyma cells (Platt-Aloia & omson, 1981). Ul-
trastructural studies showed that the idioblasts are larger than the parenchyma cells;
however, these correspond only to approximately 2% of the cells in the mesocarp. e
fate of the idioblasts in the cold-pressing process has not yet been determined. ey
may be broken down in the extraction process (and are therefore released into the oil),
or remain in the solid phase (pomace), or liquid stream.
Much historical published information on avocado oil content was related to
the use of oil content as a measure of the minimal maturity to harvest avocados (e.g.,
Lee et al., 1983). However, reliable and robust oil extraction is labor- intensive and
expensive to implement on orchards. Because a strong relationship exists between
oil content (as measured by solvent extraction) and dry matter, avocado industries
worldwide base their regulations or recommendations for minimal harvest time on
dry matter (Brown, 1984; Hopkirk, 1989; Lee et al., 1983).
Postharvest Ripening of Avocados
A noteworthy characteristic of avocado fruit is that they do not ripen (soften to an
edible state) while attached to the tree. Once removed from the tree, fruit ripening
generally takes 6–10 days. e timing and variability of ripening are inuenced by
the cultivar, the stage of maturity, and other external factors such as storage time,
temperature, and ethylene exposure. erefore, ripening can be as short as 3–4 days
or as long as 18–21 days. Ethylene treatment (a naturally occurring gaseous plant
hormone) is used as a means of accelerating and synchronizing ripening, and is an
important tool for the sale of “ripe tonight” fruit to consumers (as is carried out for
bananas), but also for those processing avocados for cold-pressed oil.
During ripening, the esh structure degrades as the pectin in the walls of the pa-
renchyma cells solubilizes, causing the esh to soften to a soft melting texture (Redg-
well et al., 1997). For the main commercial cultivar Hass, changes in softening are
accompanied by a distinct skin-color change from green to black/purple (Cox et al.,
2004; Williams, 1977). For the majority of other cultivars (“green skins”), skin-color
changes are more subtle, with a darkening of the green color from more emerald to
darker green. Low-temperature storage of fruit for transport and sale is commonplace
in the fresh-fruit industry. Cool storage at 4 to 8°C for up to about 4 weeks also re-
duces the ripening rate and fruit-to-fruit variability. However, longer storage periods
Avocado Oil 79
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can cause an internal-chilling injury (esh discoloration) and general reduction of
ripe-fruit quality (White et al., 2005).
Tissue Types and Proportions of Hass Avocado Fruit
For Hass avocado, the fruit is made up of approximately 68% of esh, 18% of seed,
and 14% of skin (by fresh weight) (Wong et al., 2008). Fruit size has relatively little
eect on the proportion of the fruit that is made up of esh, and therefore, one can
process all fruit sizes for oil extraction. is is a particularly useful attribute since at
the end of the harvest season many growers “strip pick,” and therefore these harvests
have a wide range of fruit sizes.
Avocado Oil Extraction
As has long been recognized, the release of the oil from the esh of the avocado is not
as easy as observed in other fruit tissue, such as olives. For example, one can observe
oil release in mature olives by simply crushing the fruit (Kiritsakis, 1998); this is
not the case for avocado esh. A demonstration of the relative diculty of extrac-
tion is shown in Fig. 2.2. Small disks of tissue (5-mm diameter by 1-mm thickness)
were extracted by using chloroform/methanol (C/M) with three tissue-preparation
techniques. e rst was simply to agitate the slices for 24 hours on a tissue shaker
in C/M (“Slices”), the second was to grind the tissue in liquid nitrogen in a mortar
and pestle and then vortex the powder in C/M (“Liquid Nitrogen”), and nally, slices
were ground using an overhead blender (Ultra-turrex (Jancke and Kundel, Munich,
Germany) for approximately 30 seconds. Clearly, fruit ripeness has a major eect on
oil extraction, and polytron grinding was the most eective technique.
Avocado oil was rst extracted for use in the cosmetic industry. Since the esh
of the avocado has a relatively high water content, initial attempts to recover the oil
from the esh by using hydraulic pressures or organic solvents required the drying of
the esh prior to extraction (Human, 1987; Montano et al., 1962; Smith & Winter,
1970). Extraction by mechanical means leads to poor oil yields, while the use of
solvents (petroleum ether, ethyl ether, or benzene) results in recoveries of between 60
and 90% of the total oil available. Boiling the esh pulp and freezing it prior to sol-
vent extraction were trialed to enhance extraction. Love (1944) added lime (CaCO3)
to the esh pulp to form a dry cake from which the oil was extracted in one of three
ways: by hydraulic press, by organic solvents, or by water otation. ey reported
more than 80% of total oil recovery using these methods.
e extraction of the oil by centrifugation to obtain oil free of solvent impuri-
ties and suitable for food use was demonstrated in the 1980s (Buenrostro & López-
Munguia, 1986; Swisher, 1988; Werman & Neeman, 1987). Using centrifugation
techniques requires the fruit to be soft (i.e., ripe), but oil yields are signicantly less
than with solvent extraction, ranging from 30 to 80% of total oil (Buenrostro &
A. Woolf et al.
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López-Munguia, 1986; Werman & Neeman, 1987). Wermen & Neeman (1987)
compared solvent extraction and the centrifugation method. Prior to centrifugation,
they also heated the pulp to temperatures of 40–75°C. ey observed dierences in
the composition and quality of oil extracted by centrifugation or by solvents, includ-
ing dierences in fatty acid composition, unsaponiables, chlorophyll content, acid
values, and hydroxyl values. Dierences in fatty acid proles were attributed to the
dierence in the raw materials and to the extraction methods. Extraction by centrifu-
gation resulted in higher chlorophyll concentrations in unrened oils.
Southwell et al. (1990) extracted avocado oil from sun-dried avocado slices by
using a screw-type expeller similar to that used in the extraction of seed oils. ey
compared peeled slices versus unpeeled, and evaluated the eect of heat conditioning
(80°C for 30 minutes) prior to pressing by an expeller. A brown-colored oil was ob-
0 2 4 6 8
8
10
12
14
16
18
20
22
24
Polytron
Liq.Nitrogen
Slices
Total Lipids (% fruit)
Days after harvest
Fig. 2.2. Mean percentage of lipids extracted from Hass avocado fruit immediately after
harvest, and after 2, 4, 6, and 8 days (8 = soft ripe) after harvest. Fruit were ethylene-
treated at 17°C for 48 hours. Each point is the average of six replicates of tissue taken
from three fruits. Samples were extracted using three dierent methods. Vertical bars =
standard errors of the mean (SEM).
Avocado Oil 81
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tained from unpeeled or peeled slices, with extraction yields of claried oil of 50–63%
of total available oil. Ortiz et al. (2004) investigated the use of microwaves to heat
the esh to 95°C to disrupt cell structure. Even using simple manual squeezing of the
pulp yielded 69% of total oil recovery.
Both Buenrostro and López-Munguia (1986) and Werman and Neeman (1987)
extracted avocado oil by the centrifugation technique at 40°C. During the twentieth
century, no commercial plants were set up for the cold-pressed extraction of avo-
cado oil based on the centrifugation method. Historically, consumers have preferred
rened oils for food use, but as the trend toward more “natural” foods has grown,
unrened cold-pressed oils have become more marketable. Soon after 2000, the com-
mercial cold-pressed extraction of avocado oil by centrifugation successfully com-
menced in New Zealand. Two factories started producing natural-green, cold-pressed
avocado oil for culinary food use (Board, 2007; Eyres et al., 2001). Both plants used
an aqueous extraction similar to olive-oil processing, followed by centrifugation at
temperatures below 50°C.
Botha and McCrindle (2003) reported on the use of supercritical uid extraction
for avocado oil recovery. e avocado esh was rst air-dried in an oven (80°C) prior
to grinding; then the oil was extracted with supercritical carbon dioxide. ey were
able to extract >90% of the total available oil. Mostert et al. (2007) showed that the
pre-treatment of the fruit and the grinding method inuenced the degree of extrac-
tion achievable by supercritical carbon dioxide or by hexane solvent extraction.
Because of the relatively high water content of avocado esh (compared with seed
products), the esh is dried to remove the excess water prior to any solvent extraction.
Drying by hot air, freeze drying, or microwave was investigated to determine the ef-
fect on the cellular structure of the esh (Human, 1987; Mostert et al., 2007; Ortiz
et al., 2004). Numerous solvents were used, including petroleum ether, ethyl ether,
benzene, hexane, ethanol/hexane mix, and supercritical carbon dioxide (Love, 1944;
Mostert et al., 2007; Ortiz et al., 2004; Smith & Winter, 1970; Werman & Neeman,
1987). is method of extraction of avocado oil requires considerable capital invest-
ment, and if organic solvents are used, the recovery of these solvents can become
costly. e removal of all traces of solvent from the oil is important, and one should
minimize the loss of solvents into the environment.
Rening
Avocado oil contains high levels of chlorophyll, and, depending on the fruit quality
used for extraction, the oil can be highly colored or can contain high levels of free
fatty acids (FFAs). e early production of avocado oil for cosmetic or food use re-
quired a light-colored, odorless oil; hence, the oil was bleached and rened (Human,
1987). In contrast, Poucher (1974) claimed that the green color of the oil provided a
more natural appeal to cosmetic products.
A. Woolf et al.
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Bleaching is carried out to remove any pigments in the oil, followed by deodor-
izing to remove any pungent odors. Other rening steps may include winterizing to
settle out any high melting- point components or alkali rening if the FFA level is too
high. Standard rening, bleaching, and deodorizing processes used currently for other
edible oils (Anderson, 2005) can be used for these steps, and are not discussed further
here.
Cold-pressed Avocado Oil (Culinary)
Extraction
e current aqueous extraction of avocado oil contradicts all earlier attempts to ex-
tract the oil from the avocado esh. Instead of removing water prior to the recovery
of the oil, water is added to the esh pulp to help with mixing and the release of the
oil from cells. e exact mechanism of oil release from cells is still unknown, but
adequate grinding of the esh is important to disrupt the cells, as is the malaxing
(mixing) step where presumably endogenous enzymes assist with cell-wall breakdown
and subsequent oil release.
e current aqueous-extraction procedures carried out in commercial plants in
New Zealand were described by Wong et al. (2008). e process is based on a con-
tinuous process used commercially for olive-oil processing (Kiritsakis, 1998). Ripe,
whole avocados are washed, followed by a seed/skin removal step. e esh is then
ground to a pulp by using a hammer mill or grinder. Water is sometimes added to
this pulp to achieve a paste of lower viscosity which is then malaxed (mixed) in a
temperature-controlled horizontal tank with a ribbon mixer. During malaxing, oil is
released from cells. Mixing is slow, and emulsion formation was not a problem. e
temperature during malaxing is maintained at 40–50°C. After malaxing, the paste
is pumped to the horizontal decanter operating at 3000–4000 rpm. Often water is
added during pumping, as the paste can be very viscous. In the decanter, the liquid
phase (water and oil) is separated from the solids (pomace). e water and oil are then
passed through polishing disc centrifuges to separate the water from the oil.
During the seed-and–skin-removal stage, approximately 90% of the skin is re-
moved, although dierences exist between producers, depending on the technique
used. e inclusion of 40 or 100% of the available skin resulted in oils with higher
levels of chlorophyll pigments (unpublished). e oils extracted with high skin lev-
els also had dierent sensory characteristics. Near-complete seed removal is typically
achieved, and seeds generally remain intact.
e quality of avocado oil extracted by using the aqueous-extraction method
was very high compared with olive oil. Typical percentage of FFA levels and peroxide
values (PVs) in fresh avocado oil are <0.5% w/w (as oleic acid) and <4 meq/kg of oil,
respectively, while for fresh olive oil the values for FFA and PV are <0.5% w/w and
<10 meq/kg of oil, respectively.
Avocado Oil 83
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© 2009 AOCS Press.
Typical Yields
As discussed earlier, the amount of total oil available in the avocado increases with
maturity. Even though the fruit are generally ripened to the same degree of rmness
over the harvest season, an increase occurs in the oil yield from cold-pressed extrac-
tion as the season progresses. Early in the season (dry matter of 24%), the total oil
content can be lower than 10% w/w, while it rises to 18% in the mid-season, and
up to 25% in the late season.
To assist with oil extraction, numerous additives were investigated, including
salts, enzymes, and pH adjustment. Werman and Neeman (1987) and Bizimana et
al. (1993) found that, by adding water (3:1 or 5:1 water/avocado), adjusting the pH
of the pulp to pH 5.5, and adding NaCl or CaCO3 and CaSO4, they could increase
oil yield by 5–18%; both groups heated the pulp to 75–98°C. Buenrostro and López-
Munguia (1986) added water at a ratio of 4:1 and a number of exogenous enzymes
(cellulose, papain, α-amylase). ey achieved 30–50% of increases in oil yield with
enzyme addition, with α-amylase being the most eective.
In contrast to this earlier research, our research and the methodology used in
New Zealand commercial plants use a water/avocado ratio of 1:3 or less, this being
considerably less water than earlier attempts to extract avocado oil by centrifuga-
tion. With early-season fruit (dry matter of 24–28%), the addition of commercial
enzymes containing various activities (pectinase, hemicellulase, cellulose) improved
oil yields by 5–40%. No signicant increase in oil yield with mid-season fruit was
observed (unpublished). Overall, the addition of exogenous enzymes at the malaxing
stage has not made the signicant increases in oil yield hoped for.
Rening
Avocado oil extracted by using the aqueous-extraction procedure is marketed as a
“naturally” extracted (i.e., little to no chemical usage) culinary oil in the same market
niche as extra-virgin cold-pressed olive oil. A key commercial goal is to retain the
distinctive green color of the oil, as well as the natural avors and aromas. Hence, to
maintain as many natural attributes as possible, the oils are not rened prior to bot-
tling. As occurs with other oils, oxidation can occur if the oil is not handled correctly
or is “abused”. Ideally, the oil is stored in stainless-steel or oxygen-impermeable tanks,
and sparged with nitrogen to remove any free oxygen. e oils are typically stored to
allow for the settling of waxes and high melting-point fatty acids or phospholipids.
e degree of settling required depends on the original fruit used and the growing
region and climate. Dierences in the lipid composition in the oil were noticeable in
oil from fruit from dierent regions and countries. For example, oil extracted from
fruit grown in Queensland, Australia, contains more waxes and high melting-point
fatty acids.
A. Woolf et al.
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© 2009 AOCS Press.
Waste Streams
ree main waste streams are generated during the extraction of avocado oil: (i) seed
and skin, and from the decanter; (ii) pomace (predominantly esh tissue); and (iii)
the water phase. e rst stream is the skin and seeds of the avocado, which make
up approximately 32% of the total fruit weight (Wong et al., 2008). In the past, this
waste stream was dumped or used as landll. However, because of growing environ-
mental concerns, alternative uses for this material (e.g., mulch/fertilizer) are being
investigated. is waste stream generally contains relatively little oil (3% by weight),
even with the small amount of esh tissue that adheres to the skin.
e seed generally is intact, except for late-season fruit where seed germination
has commenced. In addition, the seed is viable, and thus one can use it for horticul-
tural purposes if desired (e.g., seedling rootstocks). However, generally, the seeds are
dumped as they contain minimal oil (<2%; Mazliak, 1965). One could investigate
the seed as a food source, perhaps as stock feed, since it contains high amounts of car-
bohydrates, although one should consider possible toxicity (Werman et al., 1991).
Pomace exiting the horizontal decanter can be surprisingly high in water, de-
pending on the water addition during malaxing. e pomace can contain as little as
20% of solids, depending on the operation of the decanter; it also contains 3–4% by
weight of oil. e solid-phase pomace is generally used as animal feed. e oil loss in
the pomace equates to a loss of 4–5% w/w of the total available oil. e liquid phase
from the decanter is a mixture of oil and water, which is then separated in a series of
two disc centrifuges.
In the nishing disc centrifuges, 98–99% of the oil leaving the decanter in the
liquid phase is recovered. e nal waste stream from the nishing centrifuge is pri-
marily water. e amount of oil lost in this stream depends on the operation and
separation eciency of the centrifuge. Minimizing the loss of oil at this step is impor-
tant for good recoveries, but also important is to ensure that no water is left in the oil.
By ensuring that the oil contains ideally <0.1% of water prior to storage, inevitably a
small loss of oil into the waste water stream will occur. Ideally, one should keep this
oil loss to <5% of the total available oil in the liquid phase exiting the decanter. e
recovery of oil from the water phase can be uneconomic because of the high volumes.
e recovery of as much oil as possible from this wastewater stream is advisable, to
reduce biological oxygen demand (BOD), and to reduce wastewater-disposal costs.
Laboratory-based Extraction
A reliable and reproducible method for determining the oil content in avocado is
needed: for determining the amount of oil available for commercial extraction, for
determining fruit maturity, and for research purposes.
A range of techniques was employed to determine the total lipid content, many
of them relatively time- consuming and expensive (Requejo-Tapia, 1999). e refrac-
Avocado Oil 85
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© 2009 AOCS Press.
tometric index (RI) method developed by Leslie and Christie (1929) in California, by
using Halowax oil #1000 (monochloronaphthalene) as a solvent, was ocially used
for the measurement of the percentage of total lipid in avocado. However, because of
the inconsistency of readings (very temperature-dependent) and equipment costs, this
method was considered inconvenient for growers. In addition, Halowax is a suspected
carcinogen and is no longer available (Lee et al., 1983).
e solvent-extraction technique using petroleum ether 40–60 (nonpolar sol-
vent) is the standard method for extracting the nonpolar triglycerides and neutral fats
in foods for analysis (AOCS Ocial Method Aa 4-38) (AOCS, 2004). is method,
often referred to as the Soxhlet method, can take between 6 and 12 hours, and auto-
mated systems usually only run four to six samples at one time. e sample must be
dried prior to extraction, and this technique is therefore considered too slow for the
industry to be used as a routine test.
An adaptation of the Gerber method originally developed for the dairy industry
showed accuracy in the determination of total lipids (polar and nonpolar) in avoca-
dos (Rosenthal et al., 1985). However, it not only uses a combination of ammable
and dangerous solvents, but also equipment that is not always available in the horti-
cultural industry (Requejo-Tapia, 1999). Several lipid-extraction methods originally
developed for animal products were used for the determination of the total lipid in
avocados with relative success. is is the case with the methods developed by Folch et
al. (1957) and Bligh and Dyer (1959) using chlorofrom/methanol (C/M). However,
a large sample size, large volumes of solvent, a relatively high level of diculty, and
a long time to achieve results are the main inconveniences of these methods. ese
methods are primarily used for “wet” products.
Lewis (1978) compared four methods of analyzing the lipid content of avocados
including the Soxhlet method (using petroleum ether), homogenization with petro-
leum ether, the C/M technique, and the refractometric method (using Halowax oil).
On average, results showed that C/M and the refractometric method gave 5–8%
higher lipid yields than the rst two methods. e researchers concluded that C/M
is suciently polar to release some membrane-bound lipids, probably comprised of
phospholipids and glycolipids, and that the similar results with Halowax oil may have
been due to the prolonged ball milling rather than solvent polarity.
We found that solvent-extraction methods are relatively slow, and although they
are generally reliable as a means of determining the oil content (AOCS, 2004), they
result in the breakdown of other compounds of interest such as pigments like chlo-
rophyll. We therefore sought to develop a protocol using the Accelerated Solvent
Extraction system (ASE®300, Dionex Corporation, Sunnyvale, CA, USA) to extract
a maximal proportion of the available oil reliably, with minimal eects on pigments
and compounds such as sterols.
A. Woolf et al.
86
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© 2009 AOCS Press.
Development of Laboratory Oil Extraction by Using Accelerated
Solvent Extractor (ASE®)
ASE is a relatively new technology that uses pressurized solvent and heat to aid oil
extraction. ASE uses stainless-steel cells, sealed closed with a screw cap and tted with
a cellulose lter. e cells are pressurized with oxygen-free nitrogen gas (N2). Samples
are heated to a designated temperature after pressurizing, and then held under this
pressure and temperature— the “static time”. e solvent is then ushed out of the
cell (using N2), and one can repeat this cycle. During our method development using
the ASE machine, we used avocado tissue ground to a powder after freeze-drying.
Various solvents and extraction combinations were tested. By using methanol, one
could produce a white sediment in the nal collection bottle. Methanol is a polar
solvent that could also extract nonlipid compounds and protein-bound lipids such
as phospholipids and sphingolipids and other waxy compounds. Hexane (nonpolar
solvent) was more suitable for avocado oil extraction because we are primarily inter-
ested in the triglycerides. In addition, hexane is the “industry standard” solvent for oil
extraction using the Soxhlet extraction method (AOCS, 2004). We sought to develop
a method that would achieve oil recovery similar to that of the industry standard Sox-
hlet technique, while minimizing the deterioration of the compounds in the oil.
By using ASE, an increase in extraction temperature from 50 to 120°C improved
oil recovery by 5.5% (Fig. 2.3). However, increasing the temperature also decreased
the quality of the oil, destroying labile compounds such as pigments and antioxi-
dants (data not shown). Destruction of chlorophyll pigments can occur at 60°C and
above, but depends on time and temperature (Kidmose et al., 2002). Furthermore,
temperatures lower than 60°C did not achieve oil recovery as well as the Soxhlet
method. us, we examined increasing the static time from 15 to 40 minutes, and
this increased oil, carotenoid, and chlorophyll recovery (data not shown). We noted
that variable results were obtained if the ground tissue was tightly packed in the cell,
presumably because of poor solvent contact and out-ow. Furthermore, the level of
tissue grinding could also aect the oil recovery. We also examined a range of cycles
and static times, and based on the percentage of oil recovered versus the industry
standard (Soxhlet), and the recovery of pigments and other compounds, we decided
on the following method, which was published by Ashton et al. (2006).
A weighed ground sample of 20 g is placed in a 100-mL stainless-steel closed
cell. Extraction conditions are: a 5-minute pre-heating step, followed by a 100-min-
ute total extraction time at 60°C and 10 MPa. e run is split into ve cycles of 20
minutes with a N2 gas purge cycle of 90 seconds. e oil dissolved in the solvent is
collected in dark-glass bottles which are N2-ushed during and after extraction by
ASE®. Hexane is removed from the resulting solution over 2 hours at 30°C using
a rapid solvent evaporator (RapidVap N2 Evaporation Systems; Labconco® Corp.,
Kansas City, MO) under owing N2 and the oil yield is expressed as percentage of oil
per dry weight of avocado tissue. e resulting oil samples are poured into dark-glass
bottles, ushed with oxygen-free N2, and stored at –80°C until analysis. All extrac-
Avocado Oil 87
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© 2009 AOCS Press.
tions and handling are performed under minimal light (0.001 µmol s¹ m²) by using
100% of hexane (liquid chromatography LiChrosolv®) and oxygen-free N2 (99.99%
of purity).
Factors Affecting Oil Yield and Quality
Factors Affecting Available Oil Yield
Preharvest Factors
Maturity
e most important factor inuencing the availability of avocado oil is the maturity
of the fruit, or time in the harvest season. As noted previously, avocado fruit are un-
usual in that the fruit can remain on the tree for many months after the time at which
the fruit are physiologically mature (i.e., they will ripen when removed from the tree).
Over this period (from 7 to as long as 18 months), some important changes are oc-
curring in the fruit. e one of main importance to oil extraction is an increase in dry
matter, and the change in this is primarily an increase in oil content.
e most signicant factor in examining maturity and oil content in avocado
is the dry-matter content. is measure of maturity is routinely used by industry
worldwide for the commercial harvesting of fresh fruit since it is simple, safe, and can
be carried out by growers and packhouses. is simply involves removing a sample of
esh tissue and drying it to a constant weight, normally either by dehydrator or oven
(65°C) or by using a domestic microwave.
50 60 70 80 90 100 110 120
61
62
63
64
65
66
67
% Oil recovery (dry basis)
Extraction temperature
Fig. 2.3. Eect of temperature (°C) on oil yield from ground, freeze-dried Hass avocado
tissue by using hexane in ASE® with three cycles and a 15-minute static time.
A. Woolf et al.
88
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© 2009 AOCS Press.
A very high correlation is present between dry-matter accumulation and oil con-
tent as reported by Lee et al. (1983) and others in the past. We carried out two ex-
tensive projects examining dry matter and oil content in six main growing regions in
New Zealand, and ve in Australia. Fruit sampling was carried out over two seasons,
from three growers from each region, three to six times through the commercial-
harvest seasons. Dry matter was measured, and total oil content was determined by
ASE® solvent extraction. e remarkably strong correlation (r2 of 0.96) of dry matter
with oil content is demonstrated in Fig. 2.4. Considering the very large dierences in
growing environments, the robustness of correlation shows the physiological signi-
cance of oil content in avocado maturity. A rough “rule of thumb” we found to hold
true in nearly all situations was that one can estimate the total oil content as being
10% less than the dry-matter content.
Dry Matter and Oil Accumulation for Hass
e very signicant changes in dry matter and oil content of avocado esh were in-
troduced previously (Fig. 2.1). While the initial pattern of dry-matter accumulation
is linear in some regions (Fig. 2.5A), dry matter (and oil content) reaches a plateau,
while in others the changes continue in a relatively linear manner (Fig. 2.5B). e
Fig. 2.4. Relationship between the percentage of dry matter and the oil content (percent-
age of fresh-weigh basis) in the esh of Hass avocado grown in New Zealand, Australia,
and California from 2003 to 2006. Each data point is the average of the three replicate
samples over a range of growers and times in the season.
18 20 22 24 26 28 30 32 34 36 38 40 42 44
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
r
2
0.96, P< 0.0001
Y= -8.75937+ 0.92839X
% Oil content
% Dry matter
New Zealand 2003/04
Australia 2004
USA 2004
New Zealand 2004/05
Australia 2005
USA 2005
USA 2006
Avocado Oil 89
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© 2009 AOCS Press.
inuence of climate in the plateau response appears signicant, since this may occur
in one season but not in another (data not shown).
Orchard, Region, Country, and Seasonal Maturity Dierences
Although we are not clear why, or what management practices inuence maturity,
undoubtedly, orchard dierences occur, and these can occur over relatively small dis-
tances. Tree age can also inuence fruit maturity since fruit on trees less than 5 years
old tend to mature earlier (Jim Clark; personal communication, 2001). However, in
this work, we sourced fruit from trees of at least 8–10 years of age.
Fig. 2.5. Percentage of dry matter (DM) of Hass avocados harvested from the Far North (A)
and Te Puke (B) regions in New Zealand during the 2003–2004 and 2004–2005 production
seasons, respectively. Each point is the mean of triplicate samples from 20 fruit. Vertical
bars are standard errors of mean (SEM).
10/09/2003
30/09/2003
20/10/2003
9/11/2003
29/11/2003
19/12/2003
8/01/2004
28/01/2004
17/02/2004
8/03/2004
28/03/2004
17/04/2004
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
% Dm Clark
% Dm Home
% Dm Wilkinson
A
% Oil Clark
% Oil Home
% Oil Wilkinson
10/09/2004
30/09/2004
20/10/2004
9/11/2004
29/11/2004
19/12/2004
8/01/2005
28/01/2005
17/02/2005
9/03/2005
29/03/2005
18/04/2005
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
10/09/2004
30/09/2004
20/10/2004
9/11/2004
29/11/2004
19/12/2004
8/01/2005
28/01/2005
17/02/2005
9/03/2005
29/03/2005
18/04/2005
6
8
10
12
14
16
18
20
22
24
26
28
30
32
34
36
38
40
42
% Dm Bailey
% Dm Lynden
% Dm Ross
% Oil Bailey
% Oil Lynden
% Oil Ross
Harvest date
B
A. Woolf et al.
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© 2009 AOCS Press.
As is well-known, (http://nzavocado.co.nz/ Monitoring Results; Fig. 2.6), the
growing region has a signicant impact on fruit maturity in terms of both timing and
maximal dry matter attained.
A wider interpretation of growing region is, of course, the country in which it is
grown. Clearly, large dierences arise between Australia and New Zealand, and for ex-
ample, California, where temperatures and rainfall dierences can be extreme. ese
can aect tree growth, tree health, irrigation practices, and fruit quality (particularly
the expression of ripe rot, which is higher in wetter growing environments). All of the
above will aect maturity, and thus oil yield.
Fig. 2.6. Dry-matter accumulation in Hass avocado for the years 2002–2007 for three New
Zealand growing regions [Far North, Whangarei, and the Bay of Plenty (Katikati/Te Puke)],
and a regional comparison for the 2007 season. Data and graphs from the New Zealand
Avocado Industry Council (AIC) Website (http://nzavocado.co.nz/Monitoring Results).
1 Apr 1May 1 Jun 1 Jul 1 Aug 1Sep 1 Oct 1 Nov
12
14
16
18
20
22
24
26
28
30
2002
2003
2004
2005
2006
2007
Far North
Dry matter content (%)
1 Apr 1May 1 Jun 1 Jul 1 Aug 1Sep 1 Oct 1 Nov
12
14
16
18
20
22
24
26
28
30
2002
2003
2004
2005
2006
2007
Whangarei
Dry matter content (%)
1 Apr 1May 1 Jun 1 Jul 1 Aug 1Sep 1 Oct 1 Nov
12
14
16
18
20
22
24
26
28
30
2002
2003
2004
2005
2006
2007
Bay of Plenty
Dry matter content (%)
1 Apr 1May 1 Jun 1 Jul 1 Aug 1Sep 1 Oct 1 Nov
12
14
16
18
20
22
24
26
28
30
Far North
Whangarei
Bay of Plenty
Regional comparison 2007
Dry matter content (%)
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We have observed signicant dierences in the dry-matter and oil-accumulation
patterns between seasons, being in some cases more signicant than the grower or
regional dierences, both in terms of the timing of maturity changes.
Dry matter and oil accumulation for other cultivars
Other cultivars which are not as commonly grown as Hass—such as Reed, Fujikawa,
Hayes, and Fuerte—are grown in smaller quantities. ese cultivars are less well-
studied in general, and very little information is available on their oils. In a small
study conducted using fruit from Whangarei and the Far North regions of New Zea-
land, samples from these cultivars were evaluated for dry matter and oil content (by
chemical extraction) during the season. As with Hass, a strong positive relationship
existed between dry matter and oil content, and these characteristics increased as the
fruit matured (Fig. 2.7).
ese cultivars generally mature at dierent times than Hass. For instance, ap-
plying the minimum 24% of dry-matter commercial standard for the harvest of Hass,
Reed, which is used as a pollinator in the eld, and Hayes achieve commercial maturi-
ty in February in New Zealand, a time at which the Hass’ harvest is coming to an end.
Cold-press extraction of Reed avocados produces a very intense golden/yellow oil,
resembling a rened oil and therefore making its marketing as an extra-virgin product
dicult. In New Zealand, cold-pressed oil from Reed is usually rened and used to
produce various avor-infused avocado oils. Fuerte avocados dominated the world
production for many years during the 1950s and 1960s mainly because of the fruit’s
excellent eating quality and relatively high yields (CAC, 1998). However, Fuerte also
presents a number of problems such as alternate bearing and short postharvest life,
and thus has become less dominant, in contrast to increased plantings of Hass. In our
study, dry matter for the Fuerte cultivar was approximately 35% in August in New
Zealand, meaning that this cultivar reached commercial maturity of 24% before Hass
(usually September). Our informal observations of commercially extracted Fuerte oil
avor suggested signicant dierences from those of Hass, and research characterizing
the avor proles of avocado oils from other cultivars than Hass would be useful.
Postharvest Factors
Ripeness
Signicantly, no changes occurred in either the oil content or levels of the various
fatty acids during the ripening of Hass avocados, nor in storage at temperatures of
0°C (chilling injury- inducing), standard storage temperatures (6°C) nor up to 10°C
(Eaks, 1990; Luza et al., 1990). e only signicant change noted was in Fuerte
avocados, where the monoglycerides and FFAs increased during ripening, probably
because of the degradation of triglycerides (Kikuta & Erickson, 1968).
A. Woolf et al.
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© 2009 AOCS Press.
24/06/2003
24/08/2003
24/10/2003
24/12/2003
24/02/2004
24/04/2004
24/06/2004
24/08/2004
24/10/2004
24/12/2004
0
5
10
15
20
25
30
35
40
45
% Dry Matter
Harvest date
Reed
Fujikawa
Hayes
Fuerte
a
24/06/2003
24/08/2003
24/10/2003
24/12/2003
24/02/2004
24/04/2004
24/06/2004
24/08/2004
24/10/2004
24/12/2004
0
5
10
15
20
25
30
35
40
45
Harvest date
% Oil Content
Reed
Fujikawa
Hayes
Fuerte
b
Fig. 2.7. Percentage of dry matter (a) and total oil content (b) (by chemical extraction) of
avocado cultivars grown in the northern regions (Far North and Whangarei) of New Zea-
land during the 2003–2004 season. Error bars = standard error of mean.
A
B
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Factors Affecting Cold-pressed Oil Yield and Quality
e above pre- and postharvest factors clearly inuence the total oil available, but a
range of other factors inuences the yield and quality of cold-pressed avocado oil.
Effect of Maturity (Time in Season) on Cold-pressed Yield
is is perhaps the most problematic area for cold-pressed avocado oil manufacturers,
since a signicant dierence exists between the available yield (i.e., total oil content as
determined by laboratory-based chemical extraction) and the cold-pressed yield.
In the following gure, we demonstrated this by showing an approximation of
the seasonal change in average dry matter (the key measure of the maturity of avocado
fruit), the total oil content (as determined by hexane extraction), and the typical com-
mercial cold-pressed oil yield (Fig. 2.8). Since commercial cold-pressed extraction is
routinely carried out on fruit of the same rmness stage, the dierence in yield is not
due to ripeness dierences. It is unclear why the yield from cold-pressed oils is so low
in early-season fruit (less mature or lower dry matter), but this may possibly be due
to the dierences in the levels of endogenous cell-wall degrading enzymes, which may
dier over the season for fruit of the same ripeness.
Ripening
While information on oil yield with maturity (discussed above) is routinely collected
commercially, other factors are dicult, or very expensive, to examine at a commer-
cial level. us, for the data presented in this and the following section, we carried
out laboratory-based trials by using a hammer mill to grind tissue, and 1- L malaxers
stirred at 30 rpm for 75 minutes at 45°C, with Hass avocados of high maturity (late
season with an average dry matter of 38%). Oil was separated by using a Heraeus
centrifuge at 3000 x g at 40°C.
Hass avocados with three ripening stages were processed: minimal, fully ripe
and overripe, where rmness hand ratings corresponded to 4, 5, and 6, respectively
(White et al., 2005). Cold-pressed oil yield increased with fruit ripeness from 7, to
9, to 11% (g of oil/g of esh fresh weight (FWt), respectively (Table 2.1). However,
with increased fruit ripeness, FFAs also increased, from 0.03 to 0.12% w/w (as oleic
acid).
Fruit Quality
Because fruit must be ripened to maximize oil yield by cold-pressed extraction, a con-
comitant increase in fruit disorders aects oil quality. In avocado, one of the greatest
challenges for fruit grown in wet environments is postharvest rots, which increase
dramatically with ripening (Hopkirk et al., 1994). In addition, a long-term storage of
A. Woolf et al.
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© 2009 AOCS Press.
Sept
Oct
Nov
Dec
Jan
Feb
Mar
Apr
5
10
15
20
25
30
35
40
Dry matter or oil content / % weight / weight of fruit flesh
Oil-Commercial cold pressed
Dry matter
Oil-Total available
Fig. 2.8. Schematic of typical changes in dry matter and oil content over a commercial
harvest and oil- processing season in New Zealand Hass avocados. Fruit in July are physi-
ologically mature (i.e., will ripen after harvest). Dry- matter content, total oil content (i.e.,
maximal available oil as determined by solvent extraction), and commercial cold-pressed
yield are shown.
Table 2.1. Eect of Hass Avocado Fruit Ripeness on Oil Yield (Percentage of Flesh Tissue)
and Percentage of Free Fatty Acids (FFAs). [Data Are Means of Three Extractions ± SEM
(Standard Error of the Mean)]
Ripeness 4 5 6
Oil yield
(g oil/g esh FWt)
7.0 ± 0.84 8.5 ± 0.22 11.04 ± 0.33
% FFA (w/w) 0.029 ± 0.017 0.093 ± 0.021 0.127 ± 0.037
fruit (over 4 weeks) results in physiological disorders, with one of the key expressions
of chilling injury being “diuse esh discoloration” (or esh greying) (White et al.,
2005). Flesh bruising (due to physical damage) is also a common disorder.
In laboratory-based cold-pressed trials, we determined the eect of varying de-
grees of three disorders—body rots, bruising, and esh greying—on oil quality as
determined by FFA. Increased levels of rots, esh bruising, or to some extent esh
greying all resulted in the reduction in oil quality as measured by FFA (Table 2.2).
Avocado Oil 95
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ese experiments demonstrate that increased fruit ripeness increases oil yield
but that disorders also increase (thus decreasing oil quality), and therefore we dem-
onstrated the need to balance oil yield with oil quality. As a best-practice recom-
mendation, oil quality should be maximized by good postharvest handling of fruit to
minimize rots and esh disorders and thus maximize oil quality.
Fruit Storage
In the normal operation of commercial avocado oil processing, fruit are often stored
for 1–2 weeks prior to ripening and subsequent oil extraction. e nature of the
avocado-production season means that during peak-harvest periods the capacity of
the oil-processing facilities may be exceeded, and fruit must be stored for even longer
periods. Fruit storage for longer than 3–4 weeks generally results in reduced fruit
quality due to increases in physiological and pathological disorders (Hopkirk et al.,
1994; Woolf et al., 2004). e commercial recommended storage temperature for
avocados is generally 5–7°C, depending on the time in the season.
We examined the eect of storage duration on the quality of oil extracted under
commercial conditions. Fruit were harvested in November (early/mid-season) at a
dry matter of 26% (24% is the minimal commercial maturity in New Zealand). Fruit
were randomized over a large number of commercial bins (250 kg) to eliminate any
orchard eects. Fruit were placed immediately into cool storage at 6°C, and removed
at weekly intervals for 7 weeks, ethylene-treated (100 µl L-1 for 2 days), and ripened at
20°C to the same rmness level (0.4 kgf ). ree replicate runs (3 × 250 kg of fruit)
were processed under commercial conditions. Measures of fruit quality and rmness
were taken on random samples of 20 fruit/250 kg bin, as described by White et al.
(2005).
As the storage time increased, the amount of ripe rots (body and stem-end rots)
and chilling disorders (esh greying, vascular browning, and stringy vascular tissue)
increased, while esh browning (i.e., bruising) did not change signicantly with stor-
age time (Fig. 2.9). ese disorders resulted in a signicant increase in the proportion
of unsound fruit (fruit with any signicant disorders), from 15 to 80% following 1–7
weeks of cool storage.
Table 2.2. Hass Avocado Oil Quality As Measured by Free Fatty Acids (FFAs w/w; as
Oleic Acid) Immediately Following Extraction from Fruit with a Range of Fruit Disorders
Including Body Rots, Bruising, and Graying. [Data Are Means of Three Extractions ± SEM
(Standard Errors of the Mean)]
Rot level Control 5% 10% 15% 30%
% FFA 0.38 ± 0.02 0.36 ± 0.02 0.42 ± 0.03 0.80 ± 0.04 0.91 ± 0.14
Bruising Control 20%
% FFA 0.77 ± 0.16 1.06 ± 0.48
Graying Control 20%
% FFA 0.77 ± 0.16 0.85 ± 0.09
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e percentage of FFAs in the oil, on the other hand, remained at approximately
0.5% for the duration of the study. Zauberman et al. (1985) showed that the peak of
enzyme activity in avocados occurs during the climacteric rise and the lowest activity
was always exhibited in the soft-ripe fruit stage at which the fruit is used for oil extrac-
tion.
e PV of the oil increased slowly from 0.75 to 1 mEq/kg as storage time in-
creased up to 3 weeks, and then increased sharply reaching a maximum of 2.25 mEq/
kg after 7 weeks of storage (Fig. 2.10). Hypothetically, fruit stored for over 3 weeks
probably did not require long malaxing times, as they were already very ripe-soft after
cool storage. e nature of malaxing operations can introduce oxygen into the paste,
causing oxidation and therefore resulting in increased PVs. e increase in PV with
storage time correlated strongly with the increase in fruit disorders. In addition, these
higher PVs in the oil will also reduce its shelf life. On the basis of this research and
our understanding of the eects of storage duration on fruit physiology and quality,
we recommend that fruit are stored for no longer then 3–4 weeks after harvest prior
to oil extraction.
Processing Conditions
Factors that inuence oil yield during processing are malaxer temperature, malaxing
time, speed of decanter, and operation of the nal polishing centrifuge. At too low
a malaxer temperature, the oil does not easily release from the cells, so temperatures
around 40 to 50°C give the best yields without a signicant reduction in oil quality
(FFA/PV). Oil release from the cells during malaxing requires adequate time, and
this will usually be most strongly inuenced by the time in the season (maturity).
With early-season fruit, the release of oil is much slower; the esh of the avocado does
not break down as easily; hence, a longer malaxing time may be needed. Generally,
malaxing times of 45 to 60 minutes are used. One must operate the decanter such
that an ecient separation of solids and liquid phases occurs and that minimal oil is
left occluded in the pomace. e degree of separation achieved in the nal polishing
centrifuges also will inuence yield. A minimal loss of oil in the wastewater phase is
desired for economic reasons.
Skin (peel) addition during oil processing does not aect oil quality (PV/FFA),
but it will inuence the composition of the oil. Avoid excessive aeration of the pulp
and the oil. Oxidation can occur at any points along the process once the oil is re-
leased from the esh. e oil in the malaxer is exposed to the air during this step;
hence, one can cover and ush the tanks with a continual supply of nitrogen gas to
minimize oxidation. With enclosed centrifuges, oxidation is minimized, but once the
oil is pumped to the storage tanks, one should ush it with nitrogen immediately.
Another precaution during processing is to minimize the exposure of the oil to light.
erefore, covered tanks and enclosed pipe work are recommended. Exposure to light
will promote photooxidation and reduce the quality of the oil.
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0.5 1 2 3 4 5 6 7
0
10
20
30
40
50
60
70
80
90
100
Fruit weeks in storage at 6
o
C
Peroxide value (mEq.kg
-1
)
% Free fatty acids (% as oleic)
% Sound fruit
%
Sound Fruit
Peroxide value
0.00
0.25
0.50
0.75
1.00
1.25
1.50
1.75
2.00
2.25
2.50
% FFA
0 1 2 3 4 5 6 7
0
10
20
30
40
50
60
70
80
90
100
% Incidence of Rots and Disorders
Fruit weeks in storage at 6oC
StemRot
BodyRot
VascularBrowning
FleshGreying
FleshBrowning
StringyVascular
Fig. 2.9. Mean incidence of Hass avocado fruit rots and disorders as a percentage of total
ripe fruit processed in the factory following up to 7 weeks in storage at 6°C. Disorders
were rated on a scale of 0–3 (0 = none to 3 = severe). Error bars represent the standard
error of means (SEM).
Fig. 2.10. Mean incidence of sound Hass avocado fruit as a percentage of total ripe fruit
processed in the oil factory following up to 7 weeks in storage at 6°C. Percentage sound is
shown as the proportion of fruit showing acceptable quality factors. Mean peroxide value
(mEq/kg oil) and percentage of free fatty acid (w/w as oleic acid) in avocado oil obtained
from the same fruit at each storage interval.
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Also important is to ensure that the oil contains <0.1% of water. Any water in
the oil will promote hydrolysis of the fatty acids, and will result in an oil with a higher
than desired FFA content.
Oxidative Stability of Avocado Oil
e presence of light has a strong inuence on the oxidative stability of avocado oil,
as was reported for other vegetable oils (Rahmani & Csallany, 1998). e high level
of chlorophyll present in avocado oil acts as a photosensitizer promoting oxidation,
while the tocopherols and carotenoids present are inhibitors of oxidation. Chlorophyll
is excited by exposure to light, and reacts with lipids to form oxidation intermediates
that can react further to form free radicals and oxidation-breakdown products; this
consequently results in the breakdown of chlorophyll pigments in the oil (Hamilton,
1994). e presence of oxygen also has a signicant inuence on the oxidative stabil-
ity of the avocado oil. Both photooxidation and autooxidation are promoted with the
small increases in oxygen present. Increased temperature has the greatest inuence
on autooxidation reactions. No interaction was found between light and tempera-
ture (unpublished). Hence, in avocado oil under light conditions, photooxidation
dominates, while at high temperatures autooxidation dominates, both reactions being
independent, as also found by Rawls and Vansante (1970).
e presence of tocopherols will inhibit autooxidation by inhibiting the initia-
tion and propagation of free radicals. Tocopherols donate their phenolic hydrogen
to lipid-free radicals present. Carotenoids are considered to be antiphotooxidants by
quenching singlet oxygen, an intermediate in the photooxidation reactions. e con-
tribution of these antioxidants to the protection of avocado oil will depend on the
storage conditions. Tocopherols are more protective at high temperatures and in dark
situations, while carotenoids are protective in light conditions. Research shows that
a reduction in both chlorophylls and carotenoids was found when the oil was stored
under light or dark conditions at similar temperatures (unpublished).
Antioxidants are often added to reduce oxidation and to increase the shelf life of
oils. Ascorbyl palmitate, citric acid, mixed tocopherols, and a combination of tocoph-
erols and citric acid were all tested to see if they could slow the oxidation rate in avo-
cado oil. e oils and the added antioxidants were stored in the dark at 60°C for over
20 days. e resulting PVs of the oils over this period are shown in Fig. 2.11. Ascorbyl
palmitate provided signicant protection against oxidation, citric acid provided some
protection, but the mixed tocopherols added surprisingly little protection. High levels
of tocopherols were reported to have prooxidant properties (Jung & Min, 1991).
To minimize the oxidation of avocado oil during storage, one should eliminate
light and oxygen; hence, one should store the oil in clean, dark-colored-glass bottles
or stainless-steel containers.
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Acyl Lipids
Mono-, di-, and triacylglycerides are all present in the lipid component of avocado
esh (Gaydou et al., 1987; Kaiser et al., 1992), but triacylglycerides by far represent
the largest proportion of the lipids (88%; Kikuta & Erickson, 1968). Also present are
low concentrations of glycol-, sulfo-, and galacto-lipids (Kaiser et al., 1992). Kikuta
and Erickson (1968) reported the lipid breakdown in Fuerte avocados (Table 2.3).
Lozano (1983) also determined the triglyceride composition of the mesocarp esh of
Fuerte avocados.
Fatty Acid Composition During Development and Commercial
Maturity
e main fatty acids in avocado oil are palmitic and stearic acids (saturates), palmito-
leic and oleic acids (monounsaturates), and linolenic and linoleic acids (polyunsatu-
rates). As the fruit grow and mature, the triglyceride content in the esh increases.
e main fatty acid (>50% of all lipids) found to increase during maturation in both
Fuerte and Hass avocados was oleic acid, while linoleic acid decreased dramatically
after the rst 4 months (from 60 to 12%), and linolenic acid decreased from 15%
at the start of the season to less than 2% at full maturity. All the other fatty acids
Time (h)
0 100 200 300 400 500 600
Peroxide Value (meq/kg fat)
0
2
4
6
8
10
12
14
16
18
Control EVAO
EVAO with 100 ppm Ascorbyl Palmitate
EVAO with 100 ppm Citric Acid
EVAO with 100 ppm Mixed Tocopherols
EVAO with 100 ppm Mixed Tocopherols and 100ppm Citric Acid
Fig. 2.11. Eect of antioxidants on the peroxide value of extra virgin avocado oil (EVAO)
stored at 60°C in dark conditions.
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remained at relatively constant levels (palmitic, palmitoleic, and stearic; Eaks, 1990).
Inoue and Tateishi (1995) followed the changes in fatty acid composition during
part of the maturation of Fuerte avocado fruit. ey found oleic acid increased from
37 to 50% of total lipids, palmitic acid remained constant at approximately 22%,
linoleic acid decreased from 14 to 11%, linolenic acid decreased slightly from 0.3 to
0.1%, while palmitoleic acid remained fairly constant at about 10% of total lipids.
Rotovohery et al. (1988) also reported changes in the fatty acid composition during
fruit maturation (Table 2.4). However, one must note that the above results may not
hold true if a signicantly longer sampling period were included. We demonstrated
that over a long harvest season the trends tended to follow an increase then a decrease
in oleic acid, with palmitic and linoleic following the inverse pattern (Fig. 2.12).
ese trends were observed in three growing regions, although only one orchard was
examined in each region.
Fatty Acid Composition in Different Countries
A growing environment can have signicant eects on the fatty acid prole of avo-
cado oil. Table 2.5 shows typical values. However, consider dierences cautiously,
since a rigorous examination of fatty acids was not carried out in all countries, and
these, of course, can also vary with season.
Nonacyl (or Unsaponiable) Components: Tocopher-
ols, Sterols, Plant Pigments, and Phenolics
Oils extracted from plant sources also contain a number of phytochemicals, which
may have important health benets in terms of disease prevention. As well as being
an oil considered to be healthy because of its high concentration of monounsaturated
Table 2.3. Level of Acyl Lipids and Phospholipids in Fuerte Avocado Flesh
(Percentage of Oil)
Class % of Oil
Free fatty acids 0.10
Triglycerides 19.96
Diglycerides 1.29
Monoglycerides 0.78
Phospholipids 0.39
Others* 0.28
Total 22.80
*Other substances extracted in chloroform/methanol (2:1).
Source: Kikuta and Erickson, 1968.
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Table 2.4. Fatty acid Composition (Percentage by Weight) of Fuerte Avocado Mesocarp
During Fruit Development (Grown Under Mediterranean Climate). Stages I, II, III, and IV
= 20, 25, 31, and 36 Weeks After Full Bloom, Respectively
Fatty acid
Stage of development
Stage I
(Mean)
Stage II
(Mean)
Stage III
(Mean)
Stage IV
(Mean)
16:0
16:1
18:0
18:1
18:2
18:3
12.8
2.6
0.9
60.8
12.3
1.1
10.2
1.9
0.6
68.4
10.2
1.1
10.9
2.2
0.5
68.6
10.8
0.9
9.3
1.5
0.6
76.8
8.3
0.6
From Ratovohery et al. (1988).
Fig. 2.12. Individual fatty acid content as a percentage of total fatty acids for Hass avo-
cado fruit harvested from August 1999 to March 2000 from one orchard of three growing
regions in New Zealand. Each point is the average of four replicates of ve fruit. Vertical
bars = SEM.
16 Jul
30 Jul
13 Aug
27 Aug
10 Sep
24 Sep
8 Oct
22 Oct
5 Nov
19 Nov
3 Dec
17 Dec
31 Dec
14 Jan
28 Jan
11 Feb
25 Feb
10 Mar
24 Mar
7 Apr
0
5
10
15
55
60
65
70
75
Fatty acid content
(% of total fatty acids)
Katikati
16 Jul
30 Jul
13 Aug
27 Aug
10 Sep
24 Sep
8 Oct
22 Oct
5 Nov
19 Nov
3 Dec
17 Dec
31 Dec
14 Jan
28 Jan
11 Feb
25 Feb
10 Mar
24 Mar
7 Apr
0
5
10
15
55
60
65
70
75
Te Puke
Harvest date
16 Jul
30 Jul
13 Aug
27 Aug
10 Sep
24 Sep
8 Oct
22 Oct
5 Nov
19 Nov
3 Dec
17 Dec
31 Dec
14 Jan
28 Jan
11 Feb
25 Feb
10 Mar
24 Mar
7 Apr
0
5
10
15
55
60
65
70
75
Far North
18:1 Oleic acid
16:0 Palmitic acid
18:2 Linoleic acid
16:1 Palmitoleic acid
18:3 Linolenic acid
Table 2.5. Fatty Acid Composition of Hass Avocado Oil from Five Countries (Wong et al.,
Unpublished Data)
Fatty acids
(% of total)
New Zealand Australia Chile Mexico California
Range Mean Mean Mean Mean Mean
Palmitic acid (16:0) 9.7–15.2 12.3 21.7 13.1 14.8 14.5
Palmitoleic acid
(16:1) 1.7–8.2 4.1 9.3 3.6 7.9 4.1
Stearic acid (18:0) 0.1–0.4 0.3 0.4 0.4 0.4 0.3
Oleic acid (18:1) 61.7–77.8 71.5 51.8 68.2 66.8 65.3
Linoleic acid (18:2) 7.7–18.9 11.6 16.0 13.2 9.5 15.0
Linolenic acid
(18:3) 0.2–0.9 0.5 0.8 0.8 0.6 0.8
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fatty acids (MUFAs), avocado oil contains relatively high concentrations of other non-
acyl phytochemicals. ese phytochemicals include pigments such as chlorophylls
and carotenoids, which give the oil its distinctive color. Other phytochemicals present
that are thought to contribute to health are the tocopherols, primarily α-tocopherol,
and the high level of sterols (principally sitosterol). Phenolics so far were not found
in high concentrations in avocado oils. A summary of the concentrations of various
phytochemicals found in avocado oil is given in Table 2.6.
Tocopherols and Tocotrienols
α-Tocopherol is the major form of vitamin E found in avocado oil (Table 2.6),
with minimal or just detectable concentrations of β-tocopherol, δ-tocopherol and
γ-tocopherol also present in oil from Hass avocados. Tocotrienols were not reported
in avocado oil. Vitamin E is an essential vitamin which has good antioxidant proper-
ties. e concentration in avocado oil is similar to olive oil (0.1–0.14 mg g-1; Boskou,
2006). Retaining vitamin E assists in extending the shelf life of avocado oil, since
Table 2.6. Typical Concentrations of Phytochemicals Found in Avocado Oil
Pigments Range Approximate mean
Chlorophylls (µg g-1)
Total chlorophylls 11.1–18.5 13.3
Chlorophyll a 2–9.5 4.9
Chlorophyll b 4.2–14.8 5.1
Pheophytin a 1.1
Pheophytin b 2.2
Carotenoids (µg g-1)
Total carotenoids 0.9–3.5 1.9
Lutein 0.5–3.3 1.6
Neoxanthin 0.2
Violaxanthin <0.5
Antheraxanthin <0.5
Tocopherols (mg g-1)
α-Tocopherol 0.07–0.19 0.11
β-Tocopherol <0.01
γ- Tocopherol <0.01
δ- Tocopherol <0.01
Sterols (mg g-1)
Sitosterol 2.23–4.48 3.28
Δ-5-Avenasterol 0.3
Campesterol 0.2
Stigmasterol <0.1
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α-tocopherol scavenges free radicals produced during oxidation reactions and also
terminates the reaction chain. e reduction of oxidation reactions is important to
reduce the formation of hydroperoxides and ultimately the formation of rancid o-
avor compounds (Coppen, 1994). As tocopherols are unstable and light-sensitive,
tocopherol retention is maximized by carrying out oil extraction in low oxygen and
light conditions.
Sterols
Plant sterols are known to lower cholesterol adsorption in humans (Piironen et al.,
2000). Sitosterol is the main plant sterol present in avocado oil. Other sterols also
present but at much lower concentrations are Δ-5-avenasterol, campesterol, and stig-
masterol. Sitosterol was stable in the oil during storage. e concentration of sitos-
terol in avocado oil (average of 3.3 mg g-1 oil with up to 4.5 in some cases; Table 2.6)
is signicantly higher than that in olive oil, which was reported to be approximately
1.62–1.93 mg g-1 of oil (Phillips et al., 2002; Verleyen et al., 2002).
Pigments
e rich color of avocado oil is due to the extraction into the oil of various plant pig-
ments such as substantial amounts of chlorophyll, carotenes, and xanthophylls.
Carotenoids
Carotenoids have strong antioxidant activity, and help in reducing the incidence of
various diseases (Lu et al., 2005) including AMD (age-related macular degeneration).
e carotenoids α-carotene, β-carotene and β-cryptoxanthin have pro-vitamin A ac-
tivity. Lu et al. (2005) reported that lutein alone from avocado did not contribute to
the anticancer eect, but that this was due to the mix of bioactive components present
in the avocado. Carotenoids are also thought to scavenge free radicals formed from
oxidation reactions.
Ashton et al. (2006) reported the decline of individual carotenoids with fruit
ripening. e level of total carotenoids fell to 30% of the original value at harvest in
the pale-green esh. Oil is extracted from ripe avocados, but the level is still relatively
high, even though a loss in the fresh fruit occurs. Research shows that a high level of
pigments is present in the skin of the avocado, and if more skin is included during
extraction, then a higher level of carotenoids can be extracted into the oil. Carotenoid
pigments levels will decrease during storage.
Chlorophylls
Chlorophyll pigments are extracted from the skin and the mesocarp (Ashton et al.,
2006). Chlorophyll pigments contribute signicantly to the phytochemical compo-
A. Woolf et al.
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nents present in avocado oil. eir exact mechanism(s) is unknown, but the consump-
tion of green vegetables was correlated with a reduced risk of cancer (Minguez-Mos-
quera et al., 2008). Our studies showed that increasing the amount of skin included
in the avocado paste during malaxing can result in the extraction of more chlorophyll
into the oil (data not shown). Chlorophyll is a strong photosensitizer, and if exposed
to light will promote photooxidation reactions in the oil. Photooxidation leads to the
oxidation of the lipids and the production of free radicals. Hence, during processing
one should eliminate any light and oxygen, as the chlorophyll pigments are rapidly
lost when exposed to both. Chlorophyll is thought to act as an antioxidant during
the storage of oils in the dark, and therefore is lost during storage (Gutierrez-Rosales
et al., 1992).
Polyphenols
Compared with other oils, relatively little is known about the polyphenolic content of
avocado oil. However, since phenolic compounds are present in avocado fruit, likely
they would be present in avocado oil. e exact nature and concentration of the phe-
nolic compounds present in avocado oil will depend on the avocados and the extrac-
tion conditions, since they are easily modied by oxidation. Phenolic compounds of
avocado were studied as a component of enzymatic browning (Lelyveld et al., 1984),
and are known to be present in mesocarp tissue (Torres et al., 1987; Van Lelyveld et
al., 1984). e main phenolic acids reported following hydrolysis were p-coumaric,
ferulic, and sinapic acids (Torres et al., 1987). Since the extracted compounds were
subjected to hydrolysis, the identities of the parent or native phenolic compounds
present in avocado are not known. e avonoid epicatechin was also in avocado
mesocarp tissue, and is thought to have a role in resistance to fungal pathogens.
In a preliminary study, we investigated the polyphenolic content of avocado oil
extracted with dierent amounts of skin in the malaxer paste under fully commercial
cold-pressed systems. e polyphenolics were extracted from avocado oil by using
the method described by Kalua et al. (2005) for olive oil with some modications.
Briey, hexane was added to an oil sample, and the polpyhenols were extracted with
methanol/water/formic acid. e resulting extracts were analyzed for phenolic com-
pounds by reversed-phase high-performance liquid chromatography (HPLC) by us-
ing a Zorbax SB column with a formic acid/acetronitrile solvent gradient. e results
showed that avocado oils appear to contain four major and numerous minor phenolic
components. e spectra of the two major components had absorption maxima at
280 nm, suggesting that these compounds are probably phenolic compounds, and
the spectra of the other two major compounds had additional absorption maxima
at 350 nm, indicating that they may be avonoids. As yet, these compounds were
not identied, and advanced spectroscopic techniques such as mass spectrometry and
nuclear magnetic resonance (NMR) are required for positive identication. However,
similar to the polyphenolics present in olive oil, the HPLC retention times of these
Avocado Oil 105
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© 2009 AOCS Press.
avocado oil components suggest that they are nonglycosidic phenolic compounds,
and are relatively lipophilic in nature, indicating they may be readily bioavailable
when consumed. Further research is ongoing to identify the phenolic components of
avocado oil.
Flavor and Aroma Compounds
Sensory Analysis
Although healthfulness (perceived or otherwise) of an oil plays a role in consumer-
purchase decisions, ultimately the taste is a key factor. Although chemical analyses
(e.g., PV and FFA) can tell us something of the quality of an oil, sensory analysis
is an essential step in determining the overall oil or food quality. Humans can be
viewed as highly sensitive “instruments” with the ability to perceive compounds such
as 2-methoxy-3-isobutylpyrazine at parts per trillion (Lund et al., 2009). Not only
is sensitivity important in the sensory experience, but so too is the way the sensory
organs interpret the information holistically. Many chemical compounds are in food
products that contribute to this sensory prole.
Nonvolatile compounds, such as polyphenols, can suppress or accentuate the
perception of volatile compounds (Lund et al., 2009). Many nonvolatile and volatile
compounds contribute to avor attributes such as rancid, grassy, cherry, and citrus a-
vors. Sensory assessments are important in delineating between poor and high-quality
oils in terms of negative “o-avors” as well as positive avors. Regulations of olive-oil
quality are premised on the sensory assessment of avor characteristics performed by
trained panels.
In olive oil, many years of research and commercial application of sensory analy-
sis were spent to develop oil- quality standards. In particular, the IOC (International
Olive Council) accredits international sensory panels to verify the “extra-virgin” sta-
tus of olive oils (COI/T.15/NC no./Rev), combined with basic chemical analyses.
To date, no information is published on the description of cold-pressed avocado oil
on which standards might be based. To meet this need, a trained sensory panel was
established at HortResearch in 2003 to describe the sensory attributes of avocado oil.
Although some similarities exist between avocado and olive oils, overall avocado oil is
very dierent. In this section we present the use of descriptive analysis to dene the
avor attributes of avocado oil.
Use of Descriptive Analysis
To develop a prole of avocado oil avor, Generic Descriptive Analysis was used in
sensory analyses. Ten panelists, with some experience of sensory descriptive analysis,
generated descriptors for the avocado oil in a roundtable setting (Lawless & Hey-
mann, 1999). Twenty-one descriptors were pared down to nine of the most salient
reference terms for avocado oil. e panel leader and panelists developed reference
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© 2009 AOCS Press.
standards for each descriptor. Once a reference standard was determined, the panel
then established a value for each of the reference standards by smelling and/or tast-
ing the reference standard while considering the attribute level in avocado oil. Upon
panel consensus, each reference standard and value was set. A standard blue-glass cup
with a watch-glass lid, as used for olive-oil assessment, was also used in avocado oil as-
sessment to aid in warming the samples and masking possible color eects. e bowl-
shaped glass tapers at the top to facilitate the concentration of the headspace volatiles
and the watch-glass lids trap volatiles until the panelist is ready to evaluate the oil.
Oil Samples Examined
A diverse range of avocado oils was examined over 5 years, mostly from oils extracted
in commercial facilities (i.e., using a full commercial process rather than small-scale
laboratory systems). Sensory studies were carried out on: freshly extracted oils; oils
stored in bottles for 1 and 2 years; oils from previously opened bottles (i.e., oxidized);
oils from fruit that had been stored for a range of time (up to 7 weeks); oils from
fruit with a range of rot levels; oils from New Zealand, Mexico, and Australia; oils
extracted from fruit which were ripened, stored, frozen, and then processed; and oils
from dierent processing techniques (such as inclusion of more or less avocado-skin
tissue in the malaxer). e majority of the oils were extracted from Hass avocados.
Attributes were then determined to be positive and negative.
Attributes Identied
Nine distinct attributes were identied. e attributes used to describe avocado oil
by this panel were smoky, grassy, mushroom/butter-like, hoppy, aniseed-like, shy,
painty, glue-like, and greasy/oily. Fishy, painty, and glue-like are considered negative
attributes, although when present in small amounts are not considered oensive. e
panel was initially trained on eight of the nine attributes, as the panel debated what
reference standard was used for oily/greasy. e term “oily/greasyis a broad term,
and narrowing the standard to specic anchor points can challenge the panelists.
Table 2.7 shows the reference standards used for each avor descriptor.
An example of sensorial dierences that were measured is shown in Fig. 2.13.
e trained panelists compared New Zealand- and Mexican-grown Hass avocado
oils. Although the oils were both obtained from Hass avocados, signicant dierences
were noted in the attributes, with the New Zealand oil being higher in grassy, hoppy,
painty, and mushroom/butter-like characteristics, whereas the Mexican oil was signif-
icantly higher in the glue-like characteristic. e sensory assessment indicated that the
quality of New Zealand avocado oil was superior to that of the Mexican oil. However,
these oils were purchased through a retail outlet, and therefore assumptions about
their representative qualities cannot be conclusively attributed to their region. To de-
termine the eect of region, factors such as extraction methods, handling procedures,
Avocado Oil 107
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© 2009 AOCS Press.
and oil shelf life would need to be controlled. However, researchers have assessed the
sensory characteristics of olive oils, and attributed specic sensory proles to regional
inuences (Caporale et al., 2006). Future avocado oil sensory research could involve
determining the regional eects on sensory attributes.
In another study, the sensory assessment of avocado oil processed from fruit with
varying skin amounts showed that avocados pressed with 43% of skin content had
higher intensities of negative attributes, specically painty and shy, than the oil de-
rived from avocados with 11% of skin content at pressing. e 43% of skin-derived
oil was also lowest in grassy characteristics, which is considered a positive attribute in
avocado oil. ese ndings supported the attributes of painty and shy, or grassy, as
being denable markers for negative and positive characteristics, respectively, in the
assessment of avocado oil.
Aroma Compounds
Although sweetness and bitterness are perceived by the tongue, many other key avor
attributes are in fact perceived by the nose as aromas. is detection relies on a avor
compound being volatile— often characterized by a low molecular weight. Aroma
volatiles are transported by air streams to the olfactory epithelium, where they stimu-
late sensory receptors, and hence in oils these are key to avor/acceptability.
Table 2.7. Avocado Oil Sensory Reference Standards Used in Trained-Panel Evaluations
Flavor descriptor Denition Reference standard
Smoky Odor of smoke off burn-
ing wood
Country Squire Smoke Flavor.
Liquid smoke, 3 drops
Grassy Odor of freshly cut grass 25 µg/L cis-3 hexen-1-ol
(Sigma)
Fishy Odor of old, dead sh Vita Pet Goldsh Granules Fish
Food, 20 g
Glue-like Sharp, acrid odor of
PVA<Q> glue
Super Strong PVA, Holdfast NZ
Ltd., 20 g
Hoppy Hoppy, malted odor of
beer
Cascade’s Pale Ale Concen-
trated Beer Starter, 30 mL in
150 mL of warm water
Aniseed Odor of aniseed, the
spice, liquorice-like
Gregg’s Aniseed (whole seeds),
20 g
Painty Odor of very rancid
linseed oil
Undiluted linseed oil, TMK
Packers Ltd. 25 mL
Butter/Mushroom-like Odor of freshly sautéed
mushrooms in butter
Slices (5 mm) of white button
mushrooms (200 g) sautéed
in 25 g of butter for 5 minutes,
medium-high heat
Oily/Greasy Odor of oil from potato
chips
Krispa, salted potato chips,
newly opened bag
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© 2009 AOCS Press.
Fruit’s volatile components can dier depending on a number of variables, in-
cluding the cultivar, fruit quality at extraction, various processing conditions, or ac-
cording to how the oil is stored following extraction.
Although considerable work was done examining the volatile fractions from olive
oils (Angerosa, 2002; Baccouri et al., 2008; Luna et al., 2006; Runcio et al., 2008;
Vichi et al., 2003), only a paucity of published work regarding a similar analysis for
avocado oil is available, especially in the relatively new area of cold-pressed avocado
oil. Here we present some preliminary ndings on a range of cold-pressed Hass avo-
cado oils, including oils that have defects as determined by a trained sensory panel.
Methods
ree avocado oils of diering quality examined in this preliminary work are de-
scribed below. All oils examined were extracted, bottled, and stored in a commercial
facility in the manner outlined above.
High Quality
A “new season” oil, which was extracted and processed within the last 2 months, and
the sample was obtained from an unopened bottle. One could view this as a “best
case” oil.
Fig. 2.13. Sensory evaluation of the attributes of New Zealand and Mexican Hass avocado oils.
0
10
20
30
40
50
60
Smokey
Fishy
Grassy
Glue-LikeHoppy
Painty
Mushroom
NZ
Mexico
Avocado Oil 109
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© 2009 AOCS Press.
Moderate Quality
Oil from the current season was opened and closed over a 2-month period, but stored
at 20°C in the dark. is oil would still be acceptable to the consumer.
Poor Quality
An oil made from fruit with a high level of rots (resulting from a long storage of fruit),
which was bottled and stored sealed at < –25°C for 2 years in the dark. is oil had a
range of o-avors, and was unacceptable from a sensory perspective.
Headspace volatiles were extracted separately from a 1-g sample of each oil, and
analyzed using gas chromatography–mass spectrometry (GC–MS). Volatiles were ex-
tracted for 1 hour at 20°C into a sealed 10-mL vial by using 65 µm of polydimethyl-
siloxane-divinylbenzene solid-phase microextraction (SPME) bers (Supelco).
e SPME bers were thermally desorbed at 220°C at the injector, connected to
a DB-Wax capillary column (J&W Scientic) into the GC (HP6890, Agilent). e
GC oven-temperature program was 30°C for 3 minutes followed by an increase of
3°C/minute to 220°C. Peaks were detected and identied using MS (Leco Pegasus
III).
Results and Discussion
For the high-quality, new-season oil, high levels of the desirable hexanal and E-2-
hexenal, E-2-hexenol, hexanol compounds—associated with fresh and green aromas
(desirable volatiles)—were observed (Fig. 2.14a; Table 2.7). Conversely, the levels of
the undesirable component, acetic acid, were low. is compound is probably as-
sociated with the “glue-like” descriptor (Table 2.7). Small amounts of terpenes were
found in the headspace of the oil, including α- and β-pinene, β-myrcene, cis- and
trans-β ocimene.
e moderate-quality oil (Fig. 2.14b) showed smaller amounts of desirable vola-
tiles (hexanal, E-2-hexenal, and E-2-hexenol) than the high- quality oil. However,
increased amounts of alcohols (propanol and hexanol) were present; these alcohols
were derived from the reduction of aldehydes. ese dierences are consistent with
the eect of the constant opening and closing of the bottle, which could have contrib-
uted to the loss of volatiles and also caused rancidity through exposure to oxygen.
Although the poor-quality oil showed some evidence of desirable compounds,
the prole was dominated by acetic acid, reecting high levels of oil oxidation (Fig.
2.14c).
Moreno et al. (2003) also recorded nding hexanal in oil extracted from micro-
waved avocado pulp, although they recorded other key compounds (octanal, nonanal,
and β-caryophyllene) which we did not identify in our analyses. Such dierences are
likely to be due to dierences in oil extraction or measurement techniques. ey did
not identify acetic acid in any of their oils, suggesting that these oils were not exposed
to oxygen during storage following extraction.
A. Woolf et al.
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© 2009 AOCS Press.
We conclude that the quality of avocado fruit used for processing and the oil-
storage conditions may be responsible for dierences in the volatile levels of avocado
oils. Our results, although preliminary, indicate that GC–MS analysis could prove to
be a useful technique in the identication of positive and negative aroma attributes
associated with avocado oil. Clearly, in-depth research is warranted, examining the
eects of key quality factors, including the eects of fruit rots and time in the bottle
(shelf life). is could then be used to compare and contrast the aroma volatile pat-
terns from avocado oils and olive oils, on which more research was carried out.
Allergic and Toxic Compounds
ree main areas of relevance pertain to this area: latex allergens, noted toxicities, and
persins (dienes).
Latex Allergens
e key allergen recorded in avocado fruit is the hevein-like allergy “latex-fruit re-
sponse,” so named primarily because of the urticaria and anaphylactic reactions to
latex-containing rubber products that were recognized in the 1990s (Abeck et al.,
Fig. 2.14. Gas chromatography–mass spectrometry (GC–MS) traces for three cold-pressed
avocado oils: a) high-quality, new-season oil, b) medium-quality oil (opened for 2 months),
and c) poor-quality oil (extracted from poor-quality, rotten fruit).
hexanal
Acetic acid
E-2-hexenal
propanol
hexanol
E-2-hexenol
alpha-pinene
a
b
c
abc
hexanal
Acetic acid
E-2-hexenal
propanol
hexanol
E-2-hexenol
alpha-pinene
a
b
c
abc
hexanal
Acetic acid
E-2-hexenal
propanol
hexanol
E-2-hexenol
alpha-pinene
a
b
c
hexanal
Acetic acid
E-2-hexenal
propanol
hexanol
E-2-hexenol
alpha-pinene
a
b
c
abc
a: TIC New Season Avocado oil sample 1:1 b: TIC Rotten Avocado Oil 1:1 c: TIC Older Avocado Oil (29/9/04):1
400 600 800 1000 1200 1400
Time (s)
0
2.5e+006
5e+006
7.5e+006
1e+007
1.25e+007
1.5e+007
1.75e+007
2e+007
Avocado Oil 111
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© 2009 AOCS Press.
1994). e avocado allergen (Prs a 1) was isolated and characterized as an IgE-binding
peptide, which is a 32 kDa basic class I endochitinase (Sowka et al., 1998), homolo-
gous to PR-3 proteins (Breiteneder & Ebner, 2000). However, this was questioned
somewhat by Karisola et al. (2005), who after clinical trials found that the isolated
hevein-like domain (HLD) molecules alone, but not when linked to endochitinases,
seemed to be responsible for IgE-mediated latex-fruit syndrome reactions. e latex-
type avocado reaction is similar to that of other fruit, such as banana and chestnut
(Breiteneder & Ebner, 2000).
us, although clearly, protein-based allergenic reactions to fresh avocado fruit
exist, it is unlikely that these compounds cause allergies in avocado oil. is is because
in the production of oil, particular attention is paid to eliminating proteins (present
in solids’ residue), since these proteins are likely to include enzymes that hydrolyze
oils (e.g., lipoxygenases), and thus result in poor quality stored oils (Williams, 2005).
Such proteins are removed at the decanter and oil “polishing” stages, and if not then,
in the subsequent sparging or settling (or “racking”) steps. Furthermore, these aller-
genic proteins are highly labile (Breiteneder & Ebner, 2000).
Dienes and Related Compounds
Specialized idioblast cells are present in avocado-fruit tissue, and contain lipid and lip-
id-soluble compounds. One well-known lipid-soluble compound is persin [(+)-(Z,Z)-
1-acetoxy-2-hydroxy-12,15-heneicosadie-4-one], originally isolated and identied
from avocado leaves. Persin has insecticidal (Rodriguez-Saona et al., 1998) and anti-
fungal activity (Prusky et al., 1991), and is believed to protect unripe avocado fruit
from avocado anthracnose (Colletotrichum gloeosporioides Penz). Recently persin was
found to have in vivo activity in the mammary gland, and induces Bim-dependent
apoptosis in human-breast cancer cells (Butt et al., 2006). e concentration of persin
is known to decrease during ripening, and likely, persin will not be present in avocado
oil manufactured from ripe avocado fruit. Additional persin-related compounds were
isolated from avocado fruit. ese include: a monoene (1-acetoxy-2,4-dihydroxy-
n-heptadeca-16-ene) (Prusky et al., 1991); a triene [(E,Z,Z)-1-acetoxy-2-hydroxy-
4-oxo-heneicosa-5,12,15-triene] (Domergue et al., 2000); isopersin, a geometric
isomer of persin with the same molecular formula (Rodriquez-Saona et al., 1998);
and a series of triols (1,2,4-trihydroxynonadecane; 1,2,4-trihydroxyheptadec-16-ene;
1,2,4-trihydroxyheptadec-16-yne) with toxicity toward human tumor cells, including
human-prostate carcinoma (PC-3) cells (Oberlies et al., 1998).
We sent three oils to the laboratory of Dr. Dov Prusky (Volcani Research Centre,
Israel) for the determination of diene levels. ese cold-pressed avocado oils were ex-
tracted commercially with the inclusion of 11, 43, and 100% of the available avocado
skin. No dienes could be detected (<50 µg of gFWt-1) in any of the oils. is suggests
that dienes and presumably monoenes are unlikely to be signicant factors in cold-
pressed oils from a human health perspective.
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Avocado oil Toxicity and Allergies
We could nd no formal studies into the allergies of avocado oil in humans. No al-
lergies (or toxicity) were recorded to cold-pressed avocado oil at the New Zealand
National Poisons Centre. However, reports were made of the eects of avocado fruit
on animal and humans, as reported in the literature (Carman & Handley, 1999;
Werman et al., 1989). Since cold-pressed avocado oil has been consumed widely by
consumers in New Zealand for 6–8 years, the allergic compounds most likely are not
extracted into the oil.
Health Benets of the Oil and Oil Constituents
Avocado Oil
Because avocado oil was not consumed in signicant quantities historically, and be-
cause the cold-pressed product is relatively new, no formal health tests of avocado oil
were performed. However, here we will point to the key components of avocado oil
that have strong scientic “healthfulness” support.
Monounsaturated Fatty Acids
e lipid content of avocados is made up of 15–20% of saturated fats, 60–70%
of monounsaturates and 10% of polyunsaturates. A diet high in monounsaturated
fatty acids (MUFAs) is recommended for a healthy Mediterranean diet (Birkbeck,
2002). Such a diet has favorable eects on lipoprotein levels, endothelium vasodila-
tion, insulin resistance, metabolic syndrome, antioxidant capacity, and myocardial
and cardiovascular mortality (Serra-Majem et al., 2006). e Mediterranean diet
recommends abundant plant foods, and olive oil as the principal source of dietary
lipids. Because avocado oil has a very similar lipid prole to olive oil, it clearly can be
included as a healthy addition to the Mediterranean diet.
α-Tocopherol
Vitamin E is an essential vitamin and is widely recognized as a powerful antioxidant.
ese antioxidants prevent the formation of damaging free radicals from the body’s
normal oxidation processes, and are associated with the reduction in the incidence
of cardiovascular diseases (Pryor, 2000). e favorable concentration of vitamin E
in cold-pressed avocado oil (70–190 µg/g of oil) is comparable or greater to that in
many olive oils (100–140 µg/g of oil; Boskou, 2006). Based on the Australia and New
Zealand guidelines for nutrient intakes, one teaspoon of avocado oil would provide
approximately one-ninth of the recommended dietary target of vitamin E for men
(NHMRC, 2008). e “softprocessing conditions used in cold-pressed extraction
methods help to retain higher levels of the relatively labile α-tocopherol than extrac-
tion and rening methods that use chemicals and/or heat.
Avocado Oil 113
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Sterols
Avocado fruit contain the highest levels of plant sterols of any fruit (Duester, 2001).
Since plant sterols are soluble in fat, they are extracted with the oil from the avocado.
e main plant sterol present in avocado oil is sitosterol, but other sterols were also
identied in the oil, including Δ-5-avenasterol, campesterol, and stigmasterol. Plant
sterols have a benecial eect on lowering blood-cholesterol levels in humans (Pi-
ironen et al., 2000). Since the consumption of adequate amounts of plant sterols can
reduce the risk of heart disease, they are included in food products such as margarine
spreads (Weststrate & Meijer, 1998). ese products have gained international ac-
ceptance, and have captured space in a competitive market despite their premium
prices.
Plant Pigments
Because of the nature of cold-pressed avocado oil extraction (i.e., the lack of post-
extraction renement), avocado oil contains signicant levels of pigments such as
carotenes, xanthophylls, and substantial amounts of chlorophyll, which are reected
in its rich green color. Since these pigments act as antioxidants, they are believed to
provide protection from diseases (Lu et al., 2005). Of the pigments in avocado oil,
the carotenoid lutein is probably the most important, and this has particular relevance
to eye health, acting in the macular region of the retina. AMD is the leading cause of
loss of vision in the elderly, and these pigments are believed to protect the cells of the
macula from light-induced damage (Koh et al., 2004; Richer et al., 2004). Avocado
oil contains approximately twice as much lutein as olive oil (Criado et al., 2007).
Skin Health
Compared with almond, corn, olive, and soybean oils, avocado oil had the highest
skin-penetration rate (Swisher, 1988). Due to its soothing and moisturizing eects,
avocado oil was added to pharmaceutical creams for the treatment of common skin
conditions such as psoriasis and dandru with results superior to the traditional med-
icated therapy (Huang et al., 2004; Stücker et al., 2001).
Avocado Fruit
Although no formal health trials were carried out on avocado oil itself, because most
of the healthful compounds in avocado fruit are extracted into avocado oil (e.g.,
90% of the carotenoids; Ashton et al., 2006), the ndings relating to avocado fruit
are very likely to apply to avocado oil, particularly cold-pressed avocado oil, which
contains such important phytochemicals as pigments such as lutein. Examples of such
benets include those described by Lu et al. (2005), who found that an extract from
Hass avocados inhibited the growth of cancer cells in vitro.
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Other bioactivities of avocado extracts were also reported. For example, avo-
cado extracts inhibited both nitric oxide and superoxide generation in cell-culture
systems, suggesting that these compounds may have antioxidant activity and possibly
chemopreventative activity against inammation-associated carcinogenesis (Kim et
al., 2000). is activity was associated with persin and the related triene. Avocado
oil produced from high-temperature drying of whole fruit and solvent extraction ap-
pears to contain hepatoxic agents that modify hepatic lipid metabolism (Werman et
al., 1989). A further study reported that avocado-fruit components have substantial
acetyl-CoA carboxylase inhibitory activity, which may help to reduce fat accumula-
tion and obesity. Inhibitory activity was isolated through bioassay-guided fractions,
and was found to be associated with persin and the related triene [(E,Z,Z)-1-acetoxy-
2-hydroxy-4-oxo-heneicosa-5,12,15-triene] (Hashimura et al., 2001). Additionally,
two further persin-related compounds were found to have acetyl-CoA carboxylase
inhibitory activity.
Avocado–soybean unsaponiables (ASUs) were used widely in Europe as a
complementary medicine for osteoarthritis (OA). ASU is claimed to improve the
symptoms of OA, and is promoted as an alternative to the standard nonsteroidal anti-
inammatory drugs (NSAIDs) including paracetamol. A recent meta-analysis of ran-
domized controlled studies concluded that ASUs have some ecacy against OA and
that “ASUs are no worse and no better for treatment of OA than other medications”.
e combined evidence is stronger for knee OA than for hip OA (Chrostensen et al.,
2008). ASU reduced the eects of the pro-inammatory cytokine IL1β by interfering
with the induction of NF-κB-activated elements in in vitro cell-based studies (Gabay
et al., 2008). Further evidence shows that ASU suppresses TNF-α, Cox-2, prosta-
glandin E2, and inducible nitric oxide synthase expression, all consistent with strong
anti-inammatory eects (Au et al., 2007).
ASU is prepared by removing the acyl lipid components from oil by saponi-
cation, followed by the isolation of the lipid-soluble residue by solvent extraction.
Avocado oil is rich in unsaponiable components (2–7%), compared with other oils
such as olive (1%). Relatively little is known about the composition of avocado
unsaponiables (AUs), but they do contain sterols (sitosterol), vitamin E, and a series
of aliphatic compounds containing a furyl nucleus conjugated with mono- or polyun-
saturated chains of 13 to 17 carbon in length (Henrotin et al., 1998). More informa-
tion is required about the composition of ASU, and studies are required to determine
which of the components of AU are responsible for this bioactivity against OA.
Authenticity and Adulteration
Avocado oil is a relatively new product in the culinary arena, and as such has no
formal or even informal standards by which oils are certied, or for that matter were
even described.
Avocado Oil 115
Reprinted with permission from Gourmet and Health-Promoting Specialty Oils Edited
by Robert A. Moreau and Afaf Kamal-Eldin, AOCS Press, Urbana, Illinois. Copyright
© 2009 AOCS Press.
At this point, no anecdotal evidence points to the adulteration of cold-pressed
avocado oil, although some product is labeled as “cold-pressed,” yet has very low col-
oration, indicating a high likelihood of processing such as bleaching. Producers who
are blending avocado oil with other oils do so to broaden the range of cold-pressed
avocado oils available, and clearly state the oils used. is includes a wide range of
avored oils such as chilli, pepper, lemon, lime, garlic or basil-infused. In addition,
oil blends with omega-3 and omega-6 fatty acids were formulated and are available
commercially (e.g., OmegaPlus® Olivado Oil).
No organization exists for avocado oil to carry out the equivalent role of the
International Olive Council (IOC—formerly the IOOC—International Olive Oil
Council), which was a formal entity of the United Nations (IOC, 2006).
We believe that our experience over the last 8 years with cold-pressed avocado
oil puts us in a credible position internationally to make the rst detailed proposed
standard for avocado oil. We have carried out many chemical analyses (of overall oil
quality as well as individual phytochemicals), developed a sensory analysis system,
and carried out many experiments examining a diverse range of factors that inuence
oil quality including avocado pre- and postharvest factors, extraction/processing con-
ditions, and post-bottling conditions (i.e., oil storage). Much of this work was either
published, is in preparation for publication, or was presented in this chapter.
Our standards proposed below (Table 2.8) are guided by the olive-oil standards
of the IOC, although avocado oil has signicant dierences from olive oil.
Summary
Avocado oil is a high-value oil with excellent qualities for both culinary and cosmetic
uses. High-quality cold-pressed avocado oil for culinary consumption is a new prod-
uct, and its production and sales are increasing consistently throughout the world.
e supply of fruit with appropriate quality and price currently limits production,
but the color, subtle avor, and healthfulness of the oil should ensure its increasing
growth.
Acknowledgments
Most of the original work presented here was funded by the Foundation for Research
Science and Technology (contract number C06X0203), and some work was fund-
ed by Horticulture Australia Ltd. (contract AVO3007) and the California Avocado
Commission. e assistance of the Olivado sta (both in New Zealand and in Aus-
tralia) is gratefully acknowledged. We also acknowledge the hard work of our under-
and postgraduate students (Nimma Sherpa, Ofelia Ashton, Angela Yi, and Carlene
Pulfer-Ridings). anks also to Dr. Dov Prusky (Volcani Research Institute, Israel) for
the analysis of oil samples for diene concentrations. anks to Michelle Napier and
Emma Clegg for assistance with literature searching. Finally, thanks to William Laing,
Daryl Rowan, Sol Green, and Anne Gunson for comments on the manuscript.
A. Woolf et al.
116
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by Robert A. Moreau and Afaf Kamal-Eldin, AOCS Press, Urbana, Illinois. Copyright
© 2009 AOCS Press.
Extra virgin Virgin Pure Blends
General Oil extracted from high-
quality fruit (minimal lev-
els of rots and physiologi-
cal disorders). Extraction
to be carried out using
only mechanical extrac-
tion methods including
presses, decanters, and
screw presses at low
temperatures
(<50°C). Addition of
water and processing
aids (e.g., enzymes and
talcum powder) is accept-
able, but no chemical
solvents can be used.
Oil extracted from sound
fruit with some rots or
physiological disorders.
Extraction to be carried
out using only mechani-
cal extraction methods
including presses,
decanters, and screw
presses at low tempera-
tures (<50°C ). Addition
of water and processing
aids (e.g., enzymes and
talcum powder) is accept-
able, but no chemical
solvents can be used.
Fruit quality not impor-
tant. Decolorized and
deodorized oil with low
acidity, low color, and
bland avor. Oil produced
from good-quality virgin
avocado oil; may be just
avocado oil or infused
with natural herb or fruit
avors.
Avocado oil is an excel-
lent oil for blending, and
complements extra-virgin
olive, axseed, macada-
mia and pumpkin-seed
oils. The specication
and composition should
match what is claimed on
the label.
Organoleptic
characteris-
tics*
Odor and taste Characteristic avocado
avor and sensory as-
sessment show at least
moderate (above 40 on a
100-point scale) levels of
grassy and mushroom/
butter with some smoky
Characteristic avocado
avor and sensory as-
sessment show at some
(above 20 on a 100-point
scale) levels of
grassy and mushroom/
butter with some smoky
Bland or matches
description of infused
avor: e.g., lemon, chilli,
rosemary, etc.
Dependent on the blend
Table 2.8. Proposed International Quality Standards for Avocado Oil—Values Are Relevant to Oil Quality at Time of Bottling
Avocado Oil 117
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by Robert A. Moreau and Afaf Kamal-Eldin, AOCS Press, Urbana, Illinois. Copyright
© 2009 AOCS Press.
Extra virgin Virgin Pure Blends
Defects Minimal to no defect
such as painty, and shy
notes below 20 and
glue-like below 35 as a
sensory panel average on
a 100- point scale
Low levels only of defects
such as painty and shy
notes below 50 as a
sensory panel average on
a 100- point scale
Low defects such as
painty and shy notes
below 50 as a sen-
sory panel average on a
100-point scale
Low defects such as
painty and shy notes
below 50 as a sen-
sory panel average on a
100-point scale
Color Intense and attractive
green
Green with potential yel-
low hue
Pale yellow Dependent on the blend
Free fatty acid
(% as oleic
acid)
≤0.5% 0.8–1.0% ≤0.1% As specied
Acid value ≤1% ≤2.0% ≤0.2%
Peroxide value
(mEq/kg oil)
≤4.0 <8.0 <0.5
Stability 2 years at ambient
temperature when stored
under nitrogen and out of
the light
18 months at ambient
temperature when stored
under nitrogen and out of
the light
>2 years at ambient
temperature when stored
under nitrogen and out
of light
Smoke point ≥250°C ≥200°C ≥250°C
Moisture ≤0.1% ≤0.1% ≤ 0.1%
Fatty acid com-
position
% (typical
values)
Palmitic acid
(16:0)
10–25
Table 2.8., cont. Proposed International Quality Standards for Avocado Oil—Values Are Relevant to Oil Quality at Time of Bottling
A. Woolf et al.
118
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by Robert A. Moreau and Afaf Kamal-Eldin, AOCS Press, Urbana, Illinois. Copyright
© 2009 AOCS Press.
Extra virgin Virgin Pure Blends
Palmitoleic
acid (16:1)
2–8
Stearic acid
(18:0)
0.1–0.4
Oleic acid
(18:1)
60–80
Linoleic acid
(18:2)
7–20
Linolenic acid
(18:3)
0.2–1
Antioxidants
(mg/kg)
Vitamin E 70–190
Trace metals
(mg/kg)
Copper ≤0.05 ≤0.05 ≤0.05 ≤0.05
* These characteristics are measured with a trained sensory panel with a minimum of 15 hours of experience of tasting avocado oil.
Table 2.8., cont. Proposed International Quality Standards for Avocado Oil—Values Are Relevant to Oil Quality at Time of Bottling
Avocado Oil 119
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by Robert A. Moreau and Afaf Kamal-Eldin, AOCS Press, Urbana, Illinois. Copyright
© 2009 AOCS Press.
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... Matured ripe avocado fruits were washed, peeled, deseeded and cut into wedges. Extraction of oil from the dried avocado pulp was conducted using the cold press method of oil extraction according to the methods stated in the work of Woolf et al. (2009) with modifications. The avocado wedges were pulverised using a domestic food blender (Binatone model BLG-555, England) at 4000 rpm for 2 min. ...
... These pigment causing compounds can be lost as a result of the mode of extraction, processing method and type of cultivar used. Hence the higher a* value (0.6) of the control sample can be attributed to the process of refining used during the production of the control sample prior to bottling (Woolf et al., 2009). ...
... Results of FFA obtained from this study was similar to that of Alozie et al. (2010), who showed an FFA value of 1.6% for avocado oil but higher than that reported by Ikhuoria and Maliki (2007) who reported a low FFA value of 0.37% in avocado pear. Woolf et al. (2009) stated that the standard FFA value of avocado oil should range between 0.1-1.0%. Though avocado oil with higher FFA values contains more unsaturated fatty acid: a useful indication of the high smoking point of the oil required for deep-fried foods, the oil becomes more susceptible to oxidation, hence exhibiting low oxidative stability (Salesa-Fetu et al., 2010). ...
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... Although avocado is mainly consumed in its fresh form, the production of avocado oil is a growing industry [2]. Avocado oil is a functional oil extracted from the pulp fruit, is recognized from its chemical properties; as the fatty acid profile with a high proportion of unsaturated fatty acids (oleic and linolenic) and a small proportion of saturated acids; and the presence of bioactive phytochemicals such as phytosterols, tocols, carotenoids and polyphenols [3][4][5][6]. Phytosterols in AO have been measured in higher concentrations than sunflower, palm and virgin olive oils [7]. On the other side, eggplant (Solanum melongena L.) is an important source of phytochemicals in countries of the Mediterranean region [8]; it is recognized for its high anthocyanin content [9], polyphenol richness, and its associated high antioxidant activity [10]. ...
... It is the same as virgin olive oil (48.6, 6.2 and 17.8%), but the proportions are similar to that of cottonseed oil (86.8, 8.8 and 2.6%). Otherwise, our data of sterol profile was completely in agreement with profiles measured in 22 commercial avocado oils; the authors [6] referred to β-sitosterol as predominant, followed by 5-avenasterol, campesterol, and stigmasterol in minimum quantities. We found stigmasterol in very low percentages, being surpassed by clerosterol. ...
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... It was reported previously by Alkhalaf et al. [8] that oleic acid was the main fatty acid present in avocado oil. A typical fatty acid profile composed of palmitic (C16:0) 10-25%, oleic (C18:1) 60-80%, linoleic (C18:2) 7-20%, and linolenic (C18:3) 0.2-1% acids of avocado oil was observed by some authors [36,37]. ...
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Chapter
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