What is unrefined, extra virgin cold-pressed avocado oil?

Abstract

Avocado oil is extracted for cosmetic use because of its very high skin penetration and rapid absorption. There are 12 major cultivars of avocado, but the main cultivars grown globally are Hass and Fuerte. Like extra virgin olive oil, cold-pressed avocado oil is unrefined and so retains the flavor and color characteristics of the fruit flesh. The process developed in New Zealand for extraction of avocado oil is based on the mechanical extraction method used for olive oil. Avocado fruit do not ripen while they remain on the tree even once they have reached maximum maturity. If the fruits are not harvested, they can remain on the tree even when the next year's fruit is developing, and can remain on the tree for more than 18 months from flowering. Once harvested, the avocado will begin to ripen. The process for recovering oil from ripe avocados is a mechanical extraction, similar to olive oil extraction, with the additional step of removing the skin and stone (seed). After this, the flesh is ground to a paste and then malaxed for 40-60 minutes at 45-50°C.

Full text

April 2010 inform
198
Marie Wong, Cecilia Requejo-Jackman, and Allan Woolf
The high oil content of the avocado fruit (Persea americana Mill.) has
been known since Aztec times, with the fruit sometimes referred to
as “vegetable butter” or “butter pear.” The plant originated in Central
America, and its cultivation has spread to warm subtropical and temper-
ate climates worldwide. The flesh of an avocado can contain up to 30%
oil (based on fresh weight), but there is very little in the seed (≅2%) or
the skin (≅7%). Avocado oil was originally, and still is, extracted for cos-
metic use because of its very high skin penetration and rapid absorp-
tion. Following pre-drying of the avocado flesh to remove as much water
as possible (≅65% water in avocado flesh), avocado oil for cosmetics
is traditionally extracted with solvents at elevated temperatures. After
extraction, the oil for application in skin care products is usually refined,
bleached, and deodorized, resulting in an odorless yellow oil.
Avocados are primarily grown for the fresh fruit market, either domestic or export. There are
12 major cultivars of avocado, but the main cultivars grown globally are ‘Hass’ and ‘Fuerte.’ The
‘Hass’ cultivar constitutes more than 90% of the avocado crop in New Zealand (NZ) as this cultivar
has excellent yield potential and also suffers less postharvest and handling disorders owing to their
thicker skins. In 2000, two processing companies in NZ began production of extra virgin avocado
oil; they pioneered the process for extracting cold-pressed avocado oil, which is sold as culinary
oil for use on salads and for cooking (Eyres et al., 2001). Like extra virgin olive oil, cold-pressed
avocado oil is unrened and so retains the avor and color characteristics of the fruit esh.
Production levels in NZ vary year to year depending on the season (some trees bear fruit
biennially), weather (wind and storms can damage fruit, which are then not suitable for fresh
fruit export), and export markets. Over the 2008/2009 season, NZ processors produced more than
150,000 liters of extra virgin avocado oil, with production expected to increase in the 2009/2010
season. Extra virgin avocado oil is also being produced in Chile, South Africa, and Kenya. Extra
virgin avocado oil from NZ is exported to Australia, Japan, Southeast Asia, Europe, and North
America by Grove Avocado Oil (Tauranga, NZ) and Olivado (Kerikeri, NZ). Avocados are primar-
ily grown in NZ for fresh fruit export; any fruit not suitable for export is sold on the local market
or to processors (for oil and other processed avocado products). Approximately 3% of the NZ
avocado crop is processed for the oil. Windfall fruit not suitable for the local market is sometimes
bought by oil processors. Fruits that are rotten or exhibit postharvest disorders and are unsuitable
for consumption are not used for oil production.
The process developed in NZ for extraction of avocado oil is based on the mechanical
extraction method used for olive oil. However, before we discuss the extraction process, we
need rst to consider the avocado fruit and its development. It is important to understand the
What is unrefined,
extra virgin
cold-pressed
avocado oil?

April 2010 inform
199
Specialty Oils
pre- and postharvest physiology of avocados, particularly how
their maturity and degree of ripeness impact the optimum time
for oil extraction.
CULTIVATION OF AVOCADO
Avocados are grown in frost-free subtropical regions. Once the
fruit has formed on the tree, it slowly matures (10 months),
increasing in size and oil content. Most avocado-exporting coun-
tries have guidelines for when to harvest the fruit such that they
are considered to be at optimum maturity to ensure they ripen and
develop the desirable avor and texture prole. The maturity of
avocados is easily determined by measuring the dry matter content
of the fruit (e.g., for NZ, the minimum dry matter for export is
24% by fresh weight; for the United States, it is 20.8%). The dry
matter content is highly correlated with the total oil content in the
fruit, hence harvesting at less than the minimum recommended
dry matter content level will result in fruit with less than optimal
oil content. The correlation between dry matter and oil content has
been found to be valid across a number of countries (NZ, Austra-
lia, and United States), with different regions and orchards.
Avocado fruit do not ripen while they remain on the tree even
once they have reached maximum maturity. If the fruits are not
harvested, they can remain on the tree even when the next year’s
fruit is developing, and can remain on the tree for more than 18
months from owering. Once harvested, the avocado will begin
to ripen. This process involves the softening of the esh due to
endogenous pectolytic enzyme activity and, for some varieties,
the coloring of the skin from green to purple-black. The degree
of ripeness of the avocado is primarily determined by measur-
ing the rmness of the fruit. Hence to ensure the oil content in
the avocados is at the maximum for processing,the fruit should
ideally be mature at harvest. This is not the case with immature
fruit blown off the tree in a storm (windfall fruit); this fruit is still
ripened but the oil content in the fruit is less than optimum. Rip-
ening leads to tissue softening, which aids with the extraction of
the oil due to the release of the oil from the parenchyma cells.
Ripening can be promoted by treating the fruit with ethylene (a
information
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April 2010 inform
200
gaseous plant hormone that synchronizes ripening) in controlled-
temperature rooms.
To have optimal oil quality, avocado fruit should not be over-
ripe and also should have minimal rots or other postharvest dis-
orders (such as esh greying due to long storage). The amount of
oil extracted from mature and ripe avocados earlier in the season
has been found to be only approximately 75% of the maximum
available oil in the esh (15% oil by fresh weight) compared to
later in the season when it is possible to extract more than 90%
of the available oil, this being the maximum oil yield (≅25% oil
by fresh weight).
EXTRACTION OF AVOCADO OIL
The process for recovering oil from ripe avocados is a mechani-
cal extraction, similar to olive oil extraction, with the additional
step of removing the skin and stone (seed). After this, the esh is
ground to a paste and then malaxed for 40–60 minutes at 45–50°C.
This is a higher malaxing temperature than used for olive oil
extraction, but it is still considered to be cold-pressed extraction
for avocado oil. The slightly higher temperature aids the extrac-
tion of the oil from the oil-containing cells and does not affect the
quality of the oil. The oil and water phases are separated from the
pulp using a high-speed decanting centrifuge, and then the oil is
separated from the water in nal polishing centrifuges. The pulp
from the decanting centrifuge and waste skin/seeds are returned
to orchards for soil conditioning and mulch, or used as animal
feed.
Avocado oil, if extracted from sound fruit (no rots, physi-
ological disorders, or damage), will result in oil with a very low
percentage of free fatty acids (%FFA) (<0.5% as oleic acid). Also,
the peroxide values (PV) can be very low (<2 meq/kg). Recom-
mended standards for extra virgin avocado oil have proposed a
maximum PV of 4 meq/kg (Table 1).
In sound, ripened fruit, the level of lipolysis that occurs is low,
resulting in low %FFA. The fruit does not need to be processed
immediately after ripening, but long delays should be avoided.
Generally a higher %FFA is due to poor-quality fruit, delays in
processing ripened fruit, or poor manufacturing practices.
PROPERTIES OF AVOCADO OIL
Extra virgin avocado oil from the ‘Hass’ cultivar has a charac-
teristic avor, is high in monounsaturated fatty acids, and has
a high smoke point (≥250°C), making it a good oil for frying.
‘Hass’ cold-pressed avocado oil is a brilliant emerald green when
extracted; the color is attributed to high levels of chlorophylls and
carotenoids extracted into the oil.
Cold-pressed ‘Hass’ avocado oil has been described as having
an avocado avor, with grassy and butter/mushroom-like avors.
Other varieties may produce oils of slightly different avor prole
as has been seen with ‘Fuerte,’ which has been described as having
more mushroom and less avocado avor.
The fatty acid profile is very similar to olive oil, in that
it is very high in oleic acid. A typical avocado oil has 76%
CONTINUED ON PAGE 259

April 2010 inform
201
TABLE 1. Proposed standards for avocado oila
Extra virgin Virgin Pure Blends
General Oil extracted from high-
quality fruit (minimal levels of
rots and physiological disor-
DERS%XTRACTIONTOBECARRIED
out using only mechanical
extraction 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 acceptable, but no chemical
solvents can be used
Oil extracted from sound
fruit with some rots or physi-
OLOGICALDISORDERS%XTRAC-
tion to be carried out using
only mechanical extraction
methods including presses,
decanters, and screw presses
at low temperatures (<50°C).
Addition of water and pro-
CESSINGAIDSEGENZYMESAND
talcum powder) is acceptable,
but no chemical solvents can
be used
&RUITQUALITYNOT
IMPORTANT$ECOLOR-
IZEDANDDEODORIZED
oil with low acidity,
low color, and bland
mAVOR/ILPRODUCED
from good quality
VIRGINAVOCADOOIL
may be just avocado
oil or infused with
natural herb or fruit
mAVORS
Avocado oil is excel-
lent for blending and
complements extra
VIRGINOLIVEmAX-
seed, macadamia,
and pumpkin seed
oils. The specifica-
tion and composition
should match what is
claimed on the label
Organoleptic characteristics*
Odor and taste #HARACTERISTICAVOCADOmAVOR
and sensory assessment shows
at least moderate (above 40
on a 100-point scale) levels of
GRASSYANDMUSHROOMBUTTER
with some smoky
#HARACTERISTICAVOCADOmAVOR
and sensory assessment
shows at some (above 20 on a
100-point scale) levels of
GRASSYANDMUSHROOMBUTTER
with some smoky
Bland or matches
description of infused
mAVOREGLEMON
chili, rosemary, etc.
$EPENDENTONTHE
blend
$EFECTS Minimal to no defects such as
painty and fishy notes below
ANDGLUELIKEBELOWAS
a sensory panel average on a
100-point scale
,OWLEVELSONLYOFDEFECTS
such as painty and fishy notes
below 50 as a sensory panel
average on a 100-point scale
,OWDEFECTSSUCH
as painty and fishy
notes below 50 as
a sensory panel
average on a 100-
point scale
,OWDEFECTSSUCH
as painty and fishy
notes below 50 as
a sensory panel
average on a 100-
point scale
Color )NTENSEANDATTRACTIVEGREEN Green with potential yellow
hue
Pale yellow $EPENDENTONTHE
blend
Free fatty acid
(% as oleic acid)
≤0.5% 0.8–1.0% ≤0.1% As specified
Acid value ≤1% ≤2.0% ≤0.2%
Peroxide value
(meq/kg oil)
≤4.0 <8.0 <0.5
Stability 2 years at ambient tempera-
ture when stored under nitro-
gen and out of the light
18 months at ambient tem-
perature when stored under
nitrogen and out of the light
>2 years at ambient
temperature when
stored under nitro-
gen and out of light
Smoke point ≥250°C ≥200°C ≥250°C
Moisture ≤0.1% ≤0.1% ≤0.1%
Fatty acid composition % (typical values)
0ALMITICACID 10–25
0ALMITOLEICACID 2–8
3TEARICACID 0.1–0.4
/LEICACID 60–80
,INOLEICACID n
,INOLENICACID 0.2–1
Antioxidants (mg/kg)
6ITAMIN% n
Trace metals (mg/kg)
Copper ≤0.05 ≤0.05 ≤0.05 ≤0.05
aReproduced from Woolf et al., 2009.
bThese characteristics are measured with a trained sensory panel with a minimum of 15 hours of experience of tasting olive oil.
Specialty Oils

259inform April 2010, Vol. 21 (4)
CARLOS E.
ASTETE,
Louisiana State
University,
USA—Honored
Student
GERARD G.
DUMANCAS,
Oklahoma State
University,
USA—Honored
Student
JENNIFER E.
LAMBERT,
University
of Alberta,
Canada—
Honored Student
and Peter and
Clare Kalustian
QIN LIU,
University
of Alberta,
Canada—
Honored Student
DEBJANI
MITRA, Iowa
State University,
USA—Honored
Student
AMIR MALAKI
NIK, University
of Guelph,
Canada—
Honored Student
VERA VAN
HOED, Ghent
University,
Belgium—
Honored Student
YU ZHANG, The
University of
Pennsylvania,
USA—Honored
Student and
Manuchehr
Eijadi
YING ZHONG,
Memorial
University of
Newfoundland,
Canada—
Honored Student
intended to help the recipient nance his or her studies.
$1,000 scholarship and a certicate.
Peter and Clare Kalustian Award
The Kalustian Award recognizes outstanding merit and performance
by an AOCS Honored Student. The award is supported by the Kalus-
tian estate.
$1,000 scholarship and a certicate.
Ralph H. Potts Memorial Fellowship Award
LINH D. DO, The University of Oklahoma, USA
$2,000 scholarship, travel stipend, and a plaque.
The Ralph H. Potts Award is presented annually to a
graduate student working in the chemistry of fats and
oils and their derivatives. The award is sponsored by
AkzoNobel to memorialize Ralph Potts, a pioneer in
research on industrial uses of fatty acids. ■
AVOCADO OIL (CONTINUED FROM PAGE 201)
monounsaturates (oleic and palmitoleic acids), 12% polyunsatu-
rates (linoleic and linolenic acids), and 12% saturates (palmitic and
stearic acids); these values are given as percentage of fatty acid/total
fatty acids. The main antioxidant in the oil is α-tocopherol, which
is present at levels of 70–190 mg/kg oil. β-, γ-, and δ-tocopherols
are only present in minor amounts (<10 mg/kg oil). Other nonlipid
components present in the oil include chlorophylls (11–19 mg/kg
oil) and carotenoids (1.0–3.5 mg/kg oil).
The chlorophylls from the esh and the skin contribute to the
characteristic emerald green color of the oil. Depending on the loca-
tion in the mesocarp, the chlorophyll content varies, but the majority
of chlorophyll and carotenoids are present in the greener layers of
esh next to the skin. If avocado skin is included in the pulp during
malaxing, then the likelihood of extracting more pigments is greater.
Chlorophyll does not contribute to oil stability but can be a problem,
as chlorophyll can act as a sensitizer for photo-oxidation to occur.
Therefore, it is important to store the oil away from light.
Carotenoids in avocado fruit have long attracted attention for
their potential anti-carcinogenic effect; these same carotenoids are
subsequently extracted into the oil. The most signicant carotenoid
present in the oil is lutein (0.5–3.3 mg/kg oil). Lutein is benecial
for eye health by reducing the progression of age-related macular
degeneration. The cold-pressed avocado oil also contains high levels
of phytosterols (β-sitosterol being the main sterol present), at 2.23–
4.48 mg/g oil. Based on its fatty acid makeup and the presence of
these phytochemicals, extra virgin cold-pressed avocado oil is con-
sidered to be a healthful oil.
STANDARDS FOR AVOCADO OIL
The impacts of postharvest procedures, preprocessing treatments,
extraction, and storage on the composition, quality, and sensory
characteristics of avocado oil have been investigated over the last
10 years in NZ in collaboration with Australian and Californian
research groups. Standards have been proposed for avocado oil,
including extra virgin, virgin, and pure grades of oil (Table 1). These
standards have been recommended to ensure that avocado oil sold
is of good quality in terms of standard quality indices, composition,
and sensory properties. The standards are unique to avocado oil,
where cold-pressed avocado oil is recovered by mechanical extrac-
tion at temperatures less than 50°C, without solvents; water and
enzymes can be used. These standards are important, as the produc-
tion and culinary consumption of cold-pressed avocado oil, with its
light, distinctive avor, is increasing worldwide.
Marie Wong is senior
lecturer at the Institute
of Food, Nutrition &
Human Health, Massey
University (Auckland,
New Zealand). She can
be contacted via email at M.Wong@massey.ac.nz. Allan Woolf and
Cecilia Requejo-Jackman are with the New Zealand Institute for Plant
& Food Research Limited (Auckland, New Zealand).