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The vanilla bean, the fruit of the climbing orchid Vanilla planifolia, is used for the commercial production of vanilla flavour, consisting of vanillin and other numerous flavour compounds. Development of the prized vanilla flavour in harvested green beans is dependent, however, on a curing process. Studies on the botany of vanilla beans revealed that flavour precursors are found in the bean interior, where they are secreted onto the placental region around the seeds. Hydrolytic or other degradative enzymes, which catalyse the release of the flavour precursors to flavour compounds, are localised mostly in the outer fruit wall region. This insight suggests that the objective of killing, the first curing stage carried out by hot water scalding, freezing or by other methods, is to disorganise the bean tissue such that contact is created between substrates and their respective enzymes. Sweating, a subsequent step in curing entailing high temperatures (usually around 45–65° C) and high humidity, provides conditions for enzyme-catalysed production of flavour compounds and also for non-enzymatic oxidative reactions. The objective of the final curing steps, including drying and conditioning are designed to preserve the formed flavour compounds. The postharvest handling of cured vanilla beans is a continuation of the curing process, aimed at preserving quality attributes achieved in the production and curing of vanilla beans. Temperature, humidity, gas composition and type of packaging are some important factors that determine bean quality in storage. Further understanding on the botany, curing and postharvest handling of the vanilla bean may render a full flavour complex and, subsequently, significant economic gains.
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Post Harvest of Cured Vanilla Beans
Daphna Havkin Frenkel and Chaim Frenkel
Department of Plant Biology and Pathology, Rutgers, The State University of New
Jersey, NJ, USA
Abstract. The vanilla bean, the fruit of the climbing orchid Vanilla planifolia is
used for the commercial production of vanilla flavor, consisting of vanillin and other
numerous flavor compounds. Development of the prized vanilla flavor in harvested
green beans is dependent, however, on a curing process. Studies on the botany of
vanilla beans revealed that flavor precursors are found in the bean interior, where
they are secreted onto the placental region around the seeds. Hydrolytic or other
degradative enzymes, which catalyze the release of the flavor precursors to flavor
compounds, are localized mostly in the outer fruit wall region. This insight suggests
that the objective of killing, the first curing stage carried out by hot water scalding,
freezing or by other methods, is to disorganize the bean tissue such that contact is
created between substrates and their respective enzymes. Sweating, a subsequent
step in curing entailing high temperatures (usually around 45º to 65º C) and high
humidity provides conditions for enzyme-catalyzed production of flavor compounds
and also for non-enzymatic oxidative reactions. The objective of the final curing
steps, including drying and conditioning, designed to preserve the formed flavor
compounds. The post harvest handling of cured vanilla beans is a continuation of the
curing process, aimed at preserving quality attribute achieved in the production and
curing of vanilla beans. Temperature, humidity and gas composition and type of
packaging are some important factors that determine bean quality in storage. Further
understanding on the botany, curing and post harvest handling of the vanilla bean
may render a full flavor complex and, subsequently, significant economic gains.
Keywords: vanilla, curing, post harvest handling, storage, vacuum, relative
humidity, temperature
Correspondence to: Daphna Havkin-Frenkel
Biotechnology Center for Agriculture and the Environment
Rutgers, The State University of New Jersey
Foran Hall, Cook College
59 Dudley Road
New-Brunswick, NJ 08901-8520
732-932-9711 Ext.349/366
Fax:732-932-9441
DaphnaHF@Aesop.rutgers.edu
Introduction
Vanilla (Vanilla planifolia Andrews) is a climbing orchid indigenous to Mexico
(Figure 1). Vanilla was introduced to Europe by the Spanish Conquistadores in 1520
but commercial production of vanilla started about 300 hundred years later with the
discovery of hand pollination of the vanilla flower. In the wild, insects carry out the
pollination of vanilla flowers (1). In commerce, vanilla is cultivated in tropical
regions and is propagated by cuttings. The plant requires 3 to 4 years to flower, and
afterward flowers once a year. The pod-like fruit (vanilla bean) is allowed to
develop for 8 to 10 months before harvesting. Worldwide production of vanilla beans
is around 2,000 tons annually (US Department of Commerce).
Vanilla production and business are going thought a series of crises. During 1998-
2003 vanilla was in short supply and from 2004 to today (2006), there has been a
huge surplus. The reason for the vanilla ongoing crises is beyond the scoop of this
paper. However during the shortage period producers used “ short” practices of
curing and in order to keep the price high many shipments of beans were high in
humidity. This caused a series of mold problems. To over come the mold a new
method was introduced called Vacuumed package, which is an anaerobic storage
which in turn created a new problem, especially in Vanilla planifolia.
2
Vanilla beans are harvested green, flavorless and are next subjected to a curing
process for 3 to 6 months, depending on various curing protocols in different
production regions. The objective of the curing process is to develop the prized
vanilla flavor and, in addition, to dry the cured beans for subsequent extraction that
renders the familiar vanilla flavor. Vanilla cultivation, biosynthesis, and economic
aspects are discussed extensively in other reviews (2, 3, 4, 5, 6, 7, 8). We are
providing, however, information on the post harvest handling and storage of cured
vanilla beans. This information is vital to the understanding of the storage process
and for further improvement of this process.
The Curing Process of Vanilla Beans
1. Purpose of Curing.
Vanilla beans are harvested green and are flavorless. During bean development on
the vine, for 8 to 10 months, flavor precursors accumulate in the placental tissue
surrounding the seeds in the inner core of the bean (Figure 2,3). Vanilla flavor
contains at least 250 identified constituents (9, 10) and chief among them is vanillin.
However, flavor precursors, glucovanillin for instance, and enzymes that catalyze
conversion of these constituents to final products are apparently sequestered in
different regions in the vanilla pod. For example, it is estimated, that activity of β-
glucosidase is roughly 10 fold higher in the outer fruit wall than in the inner
placental tissue and the glandular hair cells. This was confirmed also by activity
staining of a cross section of vanilla pod for β-glucosidase (results not shown). These
data, suggest that in intact tissues of green beans hydrolytic enzymes, including β-
glucosidase and perhaps other glycosyl hydrolases, are spatially separated from
glucovanillin or other flavor precursors, which are localized in the fruit interior. The
purpose of the curing process, then, is to create contact between flavor precursors
and the enzymes that catalyze the hydrolysis of these compounds to flavor products.
An additional objective is the drying of cured beans for the preservation of the
formed flavor compounds.
2. Traditional Methods of Curing.
The curing process is comprised of four major stages including Killing, Sweating,
Drying and Conditioning.
Killing. Modern methods of killing are based on the observation that, in the ancient
Mexican method of curing, killing consisted of wilting the beans in the sun until
beans became brown (11). Contemporary methods for killing vanilla beans include:
a. sun killing, b. oven killing, c. hot water killing, d. killing by scratching, and, e.
killing by freezing (1). The stated purpose of the various killing methods is to bring
about the cessation of the vegetative life of the vanilla bean and allows contact
between enzymes and substrates (12; 13). The most practical and most commonly
used killing methods of green beans are exposure to the sun, killing by oven heat, or
hot water killing (2). Hot water killing consists of placing the green beans in wire
baskets and submerging in hot water (60º to 70º C) for 3 minutes. Freezing, by
dipping in liquid nitrogen or by holding beans for a few hours in a freezer (0º to -80º
C), is yet another method of killing (14). Our own experience and those of other
studies (5, 15) indicate, however, that storage of frozen beans must be carried out at
-70º C or below to preserve the viability of enzymes that are involved in the curing
process.
Sweating. After the killing process, beans are allowed to sweat. During this stage,
killed beans develop the characteristic vanilla flavor, aroma and color. During the
sweating stage, beans are held at high humidity and high temperature (45º to 65º C)
for 7 to 10 days (11, 16). The purpose of sweating is to retain enough moisture to
allow enzymes to catalyze various hydrolytic and oxidative processes and allowing,
perhaps, non-enzymatic reactions to occur. At the same time, some moisture is
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permitted to escape to reduce the water content sufficiently to prevent spoilage by
microorganisms.
Drying and Conditioning. At the end of a sweating period, beans are brown in color,
and have developed most of the characteristic flavor and aroma of cured beans.
However, at the end of this stage, beans contain about 60 to 70% moisture and are
traditionally dried for protection against microbial spoilage and to stop any further
enzymatic activity. At the end of the drying process, the moisture content in the
beans reaches 25 to 30% of the bean weight (2).
Drying is the most difficult stage in the curing process to control. Uneven drying
may result from varying bean size, differences in bean moisture content, and from
variable environmental conditions. The latter may include weather conditions during
sun drying or from variations in the relative humidity during sun or air-drying. The
drying stage is apparently critical to the preservation of flavor quality, but prolonged
drying may lead to loss in flavor and in vanillin content. Traditionally, the last stage
of the curing process is the step termed “conditioning”. In scientific terms it is not a
well-defined step, since there is scarcity of literature information on chemical and
physiological changes, occurring during conditioning and instead, there are many
speculations. We propose that the conditioning step is the initial step of the storage
phase of cured beans and should be considered as one aspect of the overall storage
management.
After the drying step, cured beans are placed in shipping containers. This practice is
different from country to country and appears to affect the over all flavor and quality
of the beans. For example, in Madagascar cured beans are traditionally sorted out by
appearance, based mainly on pod length, width, split and deformity. Beans are then
bundled and placed in tin boxed lined with wax papers ( Figure 4). The beans from
Indonesia are packaged in cardboard boxes, lined with polyethylene or waxed paper.
In Tahiti, cured vanilla beans are bundled, neatly packed in tin boxes lined with
waxed paper. The snug fit lid would allow the beans to keep one to two years
without loosing much weight, even though there are much higher in mo isture
content.
Today some ready-to-sell beans are vacuum-packed, in different size bags for
storage or shipment. Vacuum packing entails use of vacuum for removal of
atmospheric gases from plastic bags, where the beans are held. The thickness of the
plastic bags prevent gas and moisture exchange between the bag interior and the
ambient atmosphere. This process preserves the moisture and presumably volatile
flavors in the cured beans. However, there are three important issues to consider,
regarding vacuum packaging. a. Tight seal of the vacuum packing does not allow
volatilization of undesirable compounds, which apparently disappear during the
traditional conditioning and storage of beans. This contributes to off-flavors in
vacuum-packed beans. b. Vacuum packing also creates inside the package an
anaerobic atmosphere, which encourage the growth and activity of anaerobic
microorganisms. The latter may be responsible for some disappearance of flavor and
perhaps formation of undesirable off – flavors in vacuum packed beans. c. The
oxygen-poor atmosphere in vacuum packages prevents non-enzymatic oxidative
reactions, which may also contribute to flavor during conditioning and storage.
Storage of Cured Vanilla Beans
1. Role of post harvest handling in supply chain
The transfer of agricultural commodities, from the farm to the market, is predicated
on the economic viability of each step in the supply chain. Although each step might
be highly effective and beneficial, a weak or failing link in the chain could put the
entire system in jeopardy. From this perspective, post harvest handling is critical
because the role of this phase is to preserve quality, such that it would be received
unimpaired at the market place. This task, however, is often compromised by the
tendency of biological material to undergo degradation resulting in either impaired
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quality and subsequent loss in quantity of harvested crops. For example, guava or
cherimoya (custard apple) are desirable for their unique quality but high perishability
precludes the marketing of these crops. This consideration applies also to cured
vanilla beans, prized for their unique and distinct flavor and aroma, which are
produced in restricted ecological niches and are shipped to distant markets. Thus,
post-harvest handling faces the challenge of preserving and transferring to the market
cured vanilla beans with a complete and desirable flavor and aroma. Failure to
complete this task nullifies the economic investment in vanilla bean production and
curing and, moreover, creation of shortages in the supply of this product. The next
section will deal with factors, which might lead to deterioration in the quality of
cured vanilla beans.
2. Factors affecting the quality of cured beans
At the end of the curing process cured vanilla beans are dried to protect the beans
from spoilage. In the dry state the bean lacks active metabolism and preservation of
the product is based on controlling physical and chemical factors, rather than
metabolic processes, that might influence quality. However, sufficient moisture
content in cured vanilla beans can promote growth and metabolic activity of
microorganisms. The latter might turnover nat ive constituents in cured beans and
alter their composition, including components that contribute to quality. Thus, the
preservation of cured vanilla beans is based on controlling physical and chemical
attributes in the beans and also activity of microorganisms.
Factor affecting the condition of dried vanilla bean:
a. Moisture content.
b. Temperature
c. Relative humidity
d. Gas regime.
e. Mode of bean packing
f. Container type
A. Moisture content. Properly cured Vanilla planifolia beans usually contain
between 18-25% moisture. Beans used for extraction have low moisture content
while garment beans contain higher moisture content. The moisture content is a
major factor in the preservation of cured vanilla beans, since low moisture content is
essential to prevent microbial growth. The water content of properly cured beans
must be sufficiently low to prevent growth and activity of microorganisms, usually
around 25-30 %. Low water in combination with and high phenolic content offer
protection against spoilage in cured beans. However, cured Vanilla tahitensis beans
may resist spoilage even when the moisture content is around 40%. The moisture
content is one of several parameters, which is important for bean quality. It is,
therefore, very important to realize that moisture content as is inter-dependent on
other quality parameters and cannot be considered, by itself, as an index of quality.
Our own data indicates, in addition, that there is large variability (around 25%) in the
moisture content among individual beans of same weight and size, further
complicating this issue. Measurement of moisture content may rely on oven drying,
to remove water and weighing of dry weight residue, Azeotropic (toluene)
distillation and capture and measurement of expelled water in a moisture trap
(AOAC method), and use of non-evasive method, using sensors to directly measure
water in the beans. We believe that direct measurement of water content is more
reliable than indirect methods.
B. Temperature. The ambient temperature in a storage system influences the
relative humidity (RH) of the surrounding atmosphere and, therefore, could
determine moisture exchange between stored beans and the environment. In addition,
temperature influences growth and activity of microorganism, which could alter bean
quality. In vanilla growing regions, characterized by hot and humid conditions,
quality of stored cured beans is, therefore, subject to alteration by excess humidity
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and high temperatures. To prevent moisture exchange with the surrounding, a
common practice in the past consisted of bundling cured beans, wrapping in wax
paper and holding 2-3 stacks of bundled beans in tin containers followed by storage
in a cool place. Although this practice, for the most part appeared beneficial it is,
never the less subject to impact by the prevailing weather.
C. Relative humidity (RH). Relative humidity is a term used to describe the
quantity of water held in a gaseous mixture, usually the atmosphere. RH is expressed
as percentage of water vapor pressure relative to the saturation vapor pressure at a
given temperature. RH is calculated, accordingly, as follows:
% RH = [(P (water) / P* (water)] X 100, where [P (water)] is the water vapor at
given temperature and gas pressure and [P* (water)] is the saturation water pressure
under the same conditions. Psychometer is used for the measurement of water vapor
properties and of heat in the atmosphere.
Figure 5 and y shows the interplay between the tissue moisture content, temperature
and relative humidity. When cured vanilla beans are placed in sealed chambers with
fixed RH, from 7 to 100%, beans show moisture loss or gain, depending on the
ambient RH. Exchange of moisture with the surrounding was rapid for the first 20
days and tapered off afterward. Moreover, rate of water exchange was in proportion
to the prevailing RH and, accordingly, more water migrated from the beans the lower
was the RH. This relationship is described in figure 6, showing clearly that water is
lost from the beans in inverse proportion to the ambient RH, although at a high RH
of 80% there was only small loss in moisture. At a saturation level, 100% RH the
beans actually gained water from the surrounding atmosphere. This information
could be helpful for designing conditions of RH to calibrate the moisture content in
cured beans to a desirable level.
The dynamics of water migration between the tissue and surrounding is dependent
also on factors, which determine water binding by biological matrices. Obviously,
strong binding of water by strongly hydrophilic molecules hinders the migration of
the tissue water to the outside. Thus, exchange of water between the surrounding and
cured beans depends in part on the structure and composition of vanilla beans from
different growing areas.
D. Gas regime. Because cured beans represent non-living material altered gas
composition in the ambient air is not expected to lead to changes in the beans.
However, the post-curing stage, non-enzymatic oxidation (INSIDE VANILLA) is
important for further development of flavor. More important, the gaseous
composition does influence growth and activity of microorganisms. Figure 7 shows
that an increase in the oxygen concentration led to enhanced evolut ion of carbon
dioxide, suggesting biological activity of microorganisms. Importantly, carbon
dioxide evolution was accompanied by accumulation of methanol (figure 8),
resulting apparently form microbial degradation of pectic material in the vanilla pod.
Other volatiles including acetaldehyde and ethanol, are also emitted under oxygen-
poor conditions but production of these volatiles is arrested by oxygen enrichment
(figure 9). These results suggest presence of different populations of
microorganisms, some thrive in aerobic conditions while other are active in oxygen-
poor conditions and each contributes to the bean compositions based on affinity to
the oxygen concentration in the surrounding. Differences in bean-microorganism
relationship are shown also in figures 10 and 11. The data shows that storage in
different gas regimes results in different flavor profiles and, moreover, that the
vanilla species influences activity of microorganisms and subsequent changes in
flavor constituents. It appears also that PNG beans are more resistant to growth and
activity of microorganisms.
Note also that this biological activity is more intensified in Madagascar Vanilla
planifolia beans as compared to Vanilla tahitensis beans form Papua New Guinea,
suggesting differences in the bean-microorganism relations. The reason for this
phenomenon is under investigation. To reduce the load of microorganisms it is
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recommended to wash the beans prior to curing and to maintain subsequent steps
under clean or sanitary conditions.
E. Packing mode of beans. The packing mode of cured vanilla beans bears
consequences mostly on water exchange with the atmosphere and to a lesser degree
on the gaseous composition in stored beans. When the bean mass relative to the
surface area exposed to the environment is large exchange of water with the
surrounding is minimized. For example, cured Tahitian vanilla beans are packed
tightly in bundles and held in tin cracker boxes lined with waxed paper. The snug fit
lid allows the beans to keep one to two years without loosing much moisture and
thus retains weight. Traditional packing in Madagascar and Mexico consisted of
bundling around 50 pods (see figure 4) and placing the bundled in tin or cardboard
boxes. Another practice is keeping cured beans in a loose state in a cardboard box,
around 0.5 m3 lined with wax paper, for beans used for extraction. This practice is
applied to lower grade beans that are not sorted out and packed carefully. Moisture
and gas exchange in this type of packing is freer than in tightly packed beans.
Tightness of packing is not a barrier to gas diffusion, however, and gas composition
in the package interior is expected to approach that of the ambient air. Gas
composition in the package interior could alter by respiratory gas exchange resulting
from biological activity of microorganisms. A new practice is packaging cured
beans under vacuum in sealed plastic films. Size of packaged can vary between 100
g to 10 kg. This type of packaging prevents altogether moisture and gas exchange
with the ambient atmosphere.
F. Container type.
In an early observation Arana (18) found that while aerobic conditions are beneficial
to flavor development in cured beans holding cured beans in oxygen-poor gaseous
environment lead to undesirable flavors. Our own observations are in keeping with
the results of Arana (18). These observations suggest that oxygen-poor environment
or complete anaerobic conditions for prolonged periods are to be avoided, to prevent
off-flavors (termed ‘phenolic’ in the trade) in stored cured beans. In addition to free
access to atmospheric gases a container design need, however, to prevent moisture
loss, because escape of water from the beans leads to weight reduction and loss of
flavor constituents (17). In an extreme case, vacuum packing will prevent moisture
loss but this practice is accompanied with degradation in bean quality. Vanilla
tahitensis beans are an exception, because these beans can tolerate vacuum with out
noticeable change in quality. At the end of the curing beans carry a small load of
mold that produce guaiacol by degrading vanillin under aerobic conditions. It is
desirable to hold these beans in open air for further drying to arrest the activity of the
mold and to vent off the guaiacol, which has a very low odor threshold. Anaerobic
microorganisms, isolated from soil can de-methylate aromatic compounds with O-
methyl substitute (19). By analogy, creating unaerobic conditions in stored beans
will give rise to microbial population capable of de- methylation of vanillin to
protocatechuic aldehyde that also give off undesirable odor. However, new studies
are required to support this supposition.
5. Summary and conclusions
Production and curing of vanilla beans is restricted to warm-zone global regions,
where these processes are carried out by traditional methods. Global market demand
for high and consistent quality of cured beans raises the need to re-examine present
concepts and practices, mostly in the curing and post-curing handling of vanilla
beans. Insights from vanilla botany and physiology argued for picking, sorting and
use of sanitary conditions for achieving quality in the starting material. It also
outlines a rational for various steps in the curing process and, moreover, for a rapid
and efficient curing process. We propose further that the post-curing process, or the
post harvest handling stage, is a continued process in the creation and transfer of
bean quality to the market place. We identified moisture content, temperature, gas
composition of the ambient atmosphere and container type as some critical factors in
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the preservation of vanilla beans. An emerging issue is the effect of microorganism
on quality as influenced also by post harvest conditions. Future technologies in
curing and storage of vanilla beans need to consider these issues. The presented
information could serve as guide for designing storage conditions. For example,
cured beans containing 25% moisture may be held at 80% RH and 20° C and in a
packing state allowing free diffusion of air to prevent anaerobic conditions. We
emphasize, however, that there is a large variability in the behavior of beans from
different growing regions and, subsequently, these guide lines may be used to find
precise conditions for storage of beans from each growing region.
Reference
1.Childers, N.F., Cibes, H.R. and Hernandez-Medina, E.. Vanilla-the orchid of
commerce. In: C.L. Withner (Ed.) The Orchids. A Scientific Survey, Robert E.
Krieger Publishing Company, Malabar, Florida 1959: 477-508.
2. Ranadive, A.S.. Vanilla . Cultivation, curing, chemistry, technology and
commercial products. G. Charalambous (Ed.) Spices, herbs and edible fungi.
Elsevier Science B.V., Amsterdam 1994: 517-576.
3. Ranadive, A.S. Vanilla Cultivation, Vanilla International Congress, 1st Princeton,
NJ, USA, Nov. 11-12, 2003, (2005), Meeting Date 2003, 25-40.
4.Ranadive, A.S; Inside look: Chemistry and Biochemistry of Vanilla Flavorist.
Perfumer & Flavorist 2006: 31:38-42.
5.Dignum, M.J.W., Kerler, J. and Verpoorte, R. Vanilla production: technological,
chemical, and biosynthetic aspects. Food Res. Inter. 2001: 17:199-219
6. Havkin-Frenkel, D., and R. Dorn. Vanilla. In S.J. Risch, C-T. Ho, Eds. Spices,
flavor chemistry and antioxidant properties. ACS Symposium, Series Vol. 660,
American Chemical Society, Washington DC 1997: .29-40.
7. Rao, S.R. and Ravishankar, G.A. Vanilla flavour: production by conventional and
biotechnological routes. J. Sci. Food Agr. 2000:80:289-304.
8.Havkin-Frenkel, D., French, J., Pak, F., Frenkel, C. Inside Vanilla. Perfumer and
Flavorist 2005 :30:36-54.
9. Adedji, J., Hartman, T.G., and Ho, C.T. Flavor characterization of different
varieties of vanilla beans. Perfumer and Flavorist 1993: 18:25-33.
10. Hartman, T.G 2003, Composition of Vanilla Beans from Different Geographical
Regions.Vanilla 2003: First international congress on the future of vanilla and
vanillin, Princeton, NJ, USA 2003.
11. Balls, A.K., and F.E. Arana. The curing of vanilla. Ind. Eng. Chem. 1941:
33:1073-1075.
12. Arana, F.E. 1943. Action of β-glucosidase in the curing of vanilla. Food Res.
1943: 8:343-351.
8
13. Theodose, R. Traditional methods of vanilla preparation and their improvement.
Trop. Sci. 1973 :15:47-57.
14. Ansaldi, G.M., G.G. Marseille, and J.L.P. Aubagne. Process for obtaining natural
vanilla flavor by treatment of green vanilla beans, and the flavor obtained. US Patent
No. 4,956,192 1990.
15. Dignum, M.J.W., J. Kerler, and R. Verpoorte. β-Glucosidase and peroxidase
stability in crude enzyme extracts from green beans of Vanilla planifolia. Andrews
Phytochem. Anal. 2001: 12:174-179.
16. Balls, A.K., and F.E. Arana. Determination and significance of phenols in vanilla
extract. Assoc. Off Agr. Chem. J. 1941: 24:507-512.
17.Frenkel, C., and Havkin-Frenkel, D. The Physics and Chemistry of Vanillin.
Perfumer and Flavorist, 2006: 31:28-36.
18. Arana, F.E. Vanilla investigations. Chemistry of Vanilla. Peurto Rico Agr. Expt.
Sta. Ann. 1940:Rept. 2-14
19. Frazer, A.C., Young, L.Y. A gram-negative anaerobic bacterium that utilizes O-
methyl substituents of aromatic acids. Appl. Environ. Microbiol. 1985: 49:1345-
1347
.
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Figures and tables
Figure 1. Vanilla planifolia plant
10
Figure 2 . Distribution of 4-hydroxybenzaldehye (top) and vanillin (middle panel) in green
and white tissue of vanilla pod. Also shown is cell size in relation to fruit development
(bottom). From Joel et al., 2003.
0
0.5
1
1.5
% of dry
weight
2-4 months 5-6 months 8-9 months
Time after pollination
4-Hydroxybenzaldehyde (BA) in inner core (white)
and outer part (green) of the bean
BA in outer layer (green) BA in inner core (white)
0
5
10
15
% of dry
weight
2-4 months 5-6 months 8-9 months
time after pollination
Vanillin in inner core (white) and outer (green)
parts
vanillin in outer layer (green) vanillin in inner core (white)
0
50
100
150
200
250
300
Micron
2-4 months 5-6 months 8-9 months
Time after pollination (months)
Cell size
11
Figure 4. An example of cured beans in bundles.
60
12
Figure 3 . Cross section (x 20) of freshly cut green vanilla .The figure shows an
inner portion composed of seed (dark bodies). Arrows indicate a white placental
tissue surrounding the seeds. Shown also are specialized hair cells as well as a green
outer fruit region. . Scale bar = 2 mm.
6
Vanillin
Producing
Cells
Black
Seeds
Endocarp
Secreted
matrix
13
Figure 5. Time course change in moisture content of cured vanilla beans held in
different relative humidity.
010 20 30 40 50 60 70 80 90 100
35
40
45
50
55
60
65
Weight of Beans (grams)
Time in Different Relative Humidity (Days)
7.0 %
22.5 %
43.2 %
57.6 %
80.2 %
100.0 %
RH
PNG Vanilla tahitensis cured beans with moisture content around 18%
were used. Around 50 g beans, in duplicates, were placed in sealed jars
containing saturated salt solution to establish the relative humidity
shown in the graph.
14
Figure 6. Rate of change in moisture content in cured vanilla beans held
in different relative humidity.
010 20 30 40 50 60 70 80 90 100
0.0
0.2
0.4
0.6
0.8
1.0
1.2
1.4
r ² = 0.9952
Relative Humidity (%)
Rate of change in Water Content
(g water/ 100 g bean tissue/ day)
The data was derived from values in figure 5. Rates were calculated from values
from day 0 to day 20.
A high correlation coefficient (r2 = 0.9952) indicates tight relat ions between relative
humidity in the surrounding and rate of moisture loss. Note that relative humidity
above 80% lead to moisture gain from the ambient environment.
15
Figure 7 . Carbon dioxide accumulation in head space of vessels containing
Vanilla planifolia from Madagascar (MDG) or Vanilla tahitensis from Papua
New Guinea (PNG).
0
10
20
30
40
50
60
Nitrogen Air Oxygen
PNG
MDG
ml CO2/ Liter Head Space
Gas regime
Beans were held in an atmosphere consisting of nitrogen, air or oxygen. Gas samples
were drawn in duplicates from each vessel at the end of 3 weeks and analyzed by TC
gas chromatogram.
16
Figure 8.
0
10
20
30
40
50
60
mg methanol/ liter head space
Nitrogen Air Oxygen
MDG cured bean
PNG cured bean
Gas regime
17
Figure 9 . Acetaldehyde accumulation in head space of vessels containing
Vanilla planifolia from Madagascar (MDG) or Vanilla tahitensis from Papua
New Guinea (PNG).
0
1
2
3
4
5
6
7
8
9
10
11
12
13
14
mg acetaldehyde/ liter head space
Nitrogen Air Oxygen
MDG cured bean
PNG cured bean
Gas regime
18
Beans were held in an atmosphere consisting of nitrogen, air or oxygen. Gas samples
were drawn in duplicates from each vessel at the end of 3 weeks and analyzed by
FID gas chromatogram.
Figure 10 . Constituents found in Madagascar cured beans held in nitrogen, air
or oxygen for 3 weeks.
0
1
2
3
4
Vanillin Anisic acid Anise alcohol Proaldehyde
Anise aldehyde
Vanillyl p-OH benzoic p-OH Vanillic
alcohol acid benzaldehyde acid
Nitrogen
Air
Oxygen
mg/ gram tissue of cured bean
total mg metabolites
per gram vanil la tissue
7.232
9.074
12.713
Bean were ground and extracted over night in 40% ethanol (1:10 tissue/solvent) at
60° C. The resulting mixture was filtered and analyzed by HPLC. Resulting peaks
were compared against known concentrations o f the shown constituents.
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Figure 11 . Constituents found in Vanilla tahitensis cured beans from Papua
New Guinea held in nitrogen, air or oxygen for 3 weeks.
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Vanillin Anisic acid Anise alcohol Proaldehyde Anise aldehyde
Vanillyl p-OH benzoic p-OH Vanillic
alcohol acid benzaldehyde acid
Nitrogen
Air
Oxygen
mg/ gram tissue of cured bean
total mg metabolites
per gram bean tissue
9.853
10.914
9.190
Bean were ground and extracted over night in 40% ethanol (1:10 tissue/solvent) at
60° C. The resulting mixture was filtered and analyzed by HPLC. Resulting peaks
were compared against known concentrations o f the shown constituents.
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... Killing stops further physiological activity and promotes cell disorganization which, in turn, causes a mixing of flavor and aroma precursors with their respective enzymes [13]. The most common killing methods involve exposure to sunlight, the use of a controlled temperature oven or hot water [14]. The traditional curing process can take 5 weeks to 5 months depending on the production region and processes used [11]. ...
... About 90% of glucovanillin was converted to vanillin in beans cured continuously (non-blanched) at 35°C for 12 d, much higher than in beans that were blanched at 67°C for 3 min and then sweated. The lower percent conversion of glucovanillin to vanillin in beans blanched at 67°C for 3 min and sweated at 45°C for 4 d or at 35°C for 5 d suggests that the blanching treatment drastically reduced β-glucosidase activity [14,18,22,32]. Drying methods may also affect vanillin levels by direct effects on enzyme activities and by sublimation of vanillin. ...
Article
Full-text available
Introduction. During maturation, vanillin is accumulated in green vanilla beans as glucovanillin; it is hydrolyzed to free vanillin by endogenous glucosidases during curing and gives the characteristic flavor of vanilla. The objective of our study was to investigate methods of curing that could greatly reduce the time to complete the process and yield cured beans that retain high concentrations of vanillin and other flavor compounds with high sensory quality rating. Materials and methods. Mature green beans were obtained from a commercial grower (Cairns, Queensland, Australia). One batch of beans was continuously sweated at 35 °C at high relative humidity (RH) for 12 d. Two further batches were blanched in water at 67 °C for 3 min, and then sweated at 45 °C at high RH for 4 d or at 35 °C for 5 d. The beans were sweated until they turned brown. Three methods of drying were evaluated: a heat pump dryer at 40 °C and RH 15%, tunnel dryer at 60 °C and RH 20%, and tunnel dryer at 60 °C and RH 10%. Vanillin was extracted from powdered samples of beans with n-pentane and dichloromethane (1:1 v/v) and assayed by HPLC. Glucovanillin was measured as total vanillin after acid hydrolysis of powdered samples of beans. Results and discussion. About 90% of the glucovanillin was converted to vanillin in non-blanched beans continuously sweated at 35 °C, but there was only 70% conversion in beans blanched at 67 °C for 3 min and sweated at 45 °C for 4 d or at 35 °C for 5 d. The sensory quality of cured beans was assessed by untrained panelists. Profiling showed that the beans sweated continuously at 35 °C had superior aroma compared with beans blanched in hot water and sweated at 45 °C or at 35 °C but the appearance of non-blanched beans was less attractive. Conclusion. The study revealed that a mild hot water blanching treatment followed by sweating at 35-45 °C and rapid drying is required to produce cured beans with excellent appearance and attractive aroma.
... Havkin-Frenkel et al. (2005) concluded that killing beans by freezing is more thorough and uniform than killing by dipping beans in hot water. Havkin-Frenkel & Frenkel (2006) indicate that freezing by dipping beans in liquid nitrogen and storing them at or below )70°C preserved the viability of enzymes that are involved in the curing process. From our study, we conclude that freezing beans at )10°C for 24 h is sufficient to produce fast and severe cell wall damage, cellular membrane collapse, and, finally, a high quantity of vanillin in ethanol extract. ...
... Renadive estimates only a 0.1% vanillyl alcohol content, while we found a 0.5% vanillyl alcohol content in our traditionally obtained extracts. Havkin-Frenkel & Frenkel (2006) studied the effect of the conditions of cured vanilla bean storage in nitrogen, air and oxygen for 3 weeks on the contents of some flavour compounds, including vanillyl alcohol. Beans were ground and extracted over night in 40% ethanol (1:10 tissue ⁄ solvent) at 60°C. ...
Article
Full-text available
The effects on the aroma compositions of ethanol extracts obtained by traditional and enzyme-assisted methods from seven killing conditions used in vanilla pod curing were studied. Two procedures of vanilla pod killing consisted of either freezing pods at −10 °C for 24 h or immersing pods in 80 °C water for 10 s each of three times with 30 s intervals resulted in the highest vanillin values in terms percentage of dry weight of the bean (2.84 and 2.96), 4-hydroxybenzaldehyde (0.18 and 0.20), vanillyl alcohol (0.56 and 0.57) and vanillic acid (0.18 and 0.19 respectively) when traditional vanilla ethanol extraction was used. When this extract was aged for 3 months it showed improvement in flavour compounds. Enzyme-assisted vanilla ethanol extraction showed a higher content of flavour compounds than traditional extract, for example vanillin 4.38% and 2.96% respectively. Only vanillic acid levels were improved after ageing of the enzyme-assisted extracts.
... Hence, farmers either sell green vanilla immediately after harvest or transform it to black vanilla. The traditional curing process takes several weeks and involves a short immersion in hot water, and an extended period of fermentation and sun drying (Havkin-Frenkel and Frenkel 2006). Once black vanilla is sufficiently dry, it can be stored either in wax wrapping paper or in vacuum packages 8 (ibid). ...
Technical Report
Full-text available
The SAVA region in north-eastern Madagascar is the global centre of vanilla production. Here, around 70,000 farmers are estimated to produce 70-80% of all global bourbon vanilla. Yet, little is known about the farming population, their livelihoods, and the impact of vanilla cultivation on biodiversity. This publication presents the results of the Diversity Turn Baseline Survey (DTBS) that was conducted in 2017. The survey provides baseline data on the socio-economic characteristics and living conditions of the local population, and farming of vanilla as well as the most important other crops (n=1,800 households). As international demand for natural vanilla has increased considerably, special emphasis is placed on the vertical integration of vanilla farmers into the global vanilla value chain. This integration is increasingly accomplished through contract farming arrangements between vanilla farmers, collectors and exporters. After a first rise in vanilla prices in 2015, the current vanilla boom took off in 2016 and was still in full swing in 2017. Consequently, the start of the price boom coincides with this survey and its retrospective questions often address the situation in 2016. The large majority of the surveyed households (HHs) in the study region practice vanilla farming (83%). Of these, only 15% conclude formal contracts while the majority of farmers (63%) sell their vanilla in informal spot markets often depending on several middlemen. Our data show that the socio-economic situation of smallholder vanilla farmers has recently improved when considering vanilla prices received, education, access to electricity and ownership of assets. However, under the high vanilla prices, theft and crime are now key constraints for vanilla farmers. In addition to descriptive statistics, this publication compares selected data between male- and female-headed HHs, poor and non-poor HHs, and HHs with- and without contracts. Members of female-headed HHs have significantly lower education, lower labour availability, smaller fields and lower vanilla harvests than male-headed HHs. HHs with contracts possess more assets, are better educated, have higher labour availability, larger vanilla plots, and larger vanilla harvests than HHs without contracts. The DTBS confirms a number of benefits for smallholders who conclude contracts with vanilla exporters or collectors. Among these benefits are the significantly higher vanilla prices even during market peaks. However, the distribution of HHs with or without contracts is skewed indicating entry barriers for certain groups of smallholders. For example, female-headed HHs were significantly less likely to have a contract than male-headed HHs, and it appears that HHs with a contract had already been less poor than HHs without a contract prior to entering contract arrangements.
... Hence, farmers either sell green vanilla immediately after harvest or transform it to black vanilla. The traditional curing process takes several weeks and involves a short immersion in hot water, and an extended period of fermentation and sun drying (Havkin-Frenkel and Frenkel 2006). Once black vanilla is sufficiently dry, it can be stored either in wax wrapping paper or in vacuum packages 8 (ibid). ...
Technical Report
The SAVA Region in north-eastern Madagascar is the global centre of vanilla production. Here, around 70,000 farmers are estimated to produce 70-80% of all global bourbon vanilla. Yet, little is known about the farming population, their livelihoods, and the impact of vanilla cultivation on biodiversity. This publication presents the results of the Diversity Turn Baseline Survey (DTBS) that was conducted in 2017. The survey provides baseline data on the socio-economic characteristics and living conditions of the local population, and farming of vanilla as well as the most important other crops (n=1,800 households). As international demand for natural vanilla has increased considerably, special emphasis is placed on the vertical integration of vanilla farmers into the global vanilla value chain. This integration is increasingly accomplished through contract farming arrangements between vanilla farmers, collectors and exporters. After a first rise in vanilla prices in 2015, the current vanilla boom took off in 2016 and was still in full swing in 2017. Consequently, the start of the price boom coincides with this survey and its retrospective questions often address the situation in 2016. The large majority of the surveyed households (HHs) in the study region practice vanilla farming (83%). Of these, only 15% conclude formal contracts while the majority of farmers (63%) sell their vanilla in informal spot markets often depending on several middlemen. Our data show that the socio-economic situation of smallholder vanilla farmers has recently improved when considering vanilla prices received, education, access to electricity and ownership of assets. However, under the high vanilla prices, theft and crime are now key constraints for vanilla farmers. In addition to descriptive statistics, this publication compares selected data between male- and female-headed HHs, poor and non-poor HHs, and HHs with- and without contracts. Members of female-headed HHs have significantly lower education, lower labour availability, smaller fields and lower vanilla harvests than male-headed HHs. HHs with contracts possess more assets, are better educated, have higher labour availability, larger vanilla plots, and larger vanilla harvests than HHs without contracts. The DTBS confirms a number of benefits for smallholders who conclude contracts with vanilla exporters or collectors. Among these benefits are the significantly higher vanilla prices even during market peaks. However, the distribution of HHs with or without contracts is skewed indicating entry barriers for certain groups of smallholders. For example, female-headed HHs were significantly less likely to have a contract than male-headed HHs, and it appears that HHs with a contract had already been less poor than HHs without a contract prior to entering contract arrangements.
... La vainilla común pertenece a la familia de las orquídeas y recientemente ha sido clasificada dentro de una nueva subfamilia, Vanilloideae (Cameron, 2005); el género Vanilla abarca 110 especies de las cualesúnicamente tres se cultivan: Vanilla planifolia Jackson ex Andrews; Vanilla pompona Schiede y Vanilla tahitensis J. W. Moore (Ramachandra y Ravishankar, 2000;Besse y col., 2004). La vainilla verde carece de sabor y aroma, por lo que es necesario un proceso artesanal (beneficio) para la formación de los compuestos volátiles responsables del aroma (Dignum y col., 2001;Dignum y col., 2002;Ruiz-Terán y col., 2001;Havkin-Frenkel y Frenkel, 2006;Pérez-Silva y col., 2006). El beneficio toma entre 3-6 meses, dependiendo de las regiones y de los países productores (Ramachandra y Ravishankar, 2000), la forma de hacerlo es diferente para cada región del mundo y de acuerdo con algunos investigadores (Odoux, 2000;Ramachandra y Ravishankar, 2000) se divide en cuatro etapas principales: marchitamiento, sudoración, secado y acondicionamiento. ...
Article
Full-text available
In this work, microstructur al changes of the tissues of vanilla were evaluated during the curing, using an Environmental Scanning Electron Microscope (ESEM). The morphometric parameters: area (A), perimeter (P), shape factor (SF) and compactness (C) of each tissue (epicarp, mesocarp and vascular bundle) were quantified by Digital Image Analysis (DIA). Results indicated that curing induces structural disruptions of the vanilla tissues which is more pronounced in the mesocarp. Shape faclor and compactness showed highest values in pods subjected to 10 cycles of sunning-sweating (10 SS) in which the highest concentration of vanillin and the lowest water looses were detected. It is possible to recommend a reduction of curing time from 20-25 SS cycles to 10.
... La vainilla común pertenece a la familia de las orquídeas y recientemente ha sido clasificada dentro de una nueva subfamilia, Vanilloideae (Cameron, 2005); el género Vanilla abarca 110 especies de las cualesúnicamente tres se cultivan: Vanilla planifolia Jackson ex Andrews; Vanilla pompona Schiede y Vanilla tahitensis J. W. Moore (Ramachandra y Ravishankar, 2000;Besse y col., 2004). La vainilla verde carece de sabor y aroma, por lo que es necesario un proceso artesanal (beneficio) para la formación de los compuestos volátiles responsables del aroma (Dignum y col., 2001;Dignum y col., 2002;Ruiz-Terán y col., 2001;Havkin-Frenkel y Frenkel, 2006;Pérez-Silva y col., 2006). El beneficio toma entre 3-6 meses, dependiendo de las regiones y de los países productores (Ramachandra y Ravishankar, 2000), la forma de hacerlo es diferente para cada región del mundo y de acuerdo con algunos investigadores (Odoux, 2000;Ramachandra y Ravishankar, 2000) se divide en cuatro etapas principales: marchitamiento, sudoración, secado y acondicionamiento. ...
Chapter
Vanilla, which originated in Mexico, is a tropical orchid belonging to the family Orchidaceae. The green vanilla pods contain glucosyl precursors of aroma compounds. The aroma is released only after "curing", when the glucovanillin is hydrolyzed by glucosidase in the vanilla pods. This study describes the microstructure of mature green vanilla pods (V. planifolia) from Papantla de Olarte, Veracruz, Mexico. Nine structures were differentiated by stereomicroscopy, and light and environmental scanning electron microscopy: epicarp (EP), outer and mid mesocarp (OM, and MM), vascular bundles (VB), endocarp (EN), placentae (P), trichomes (TC), crystals of calcium oxalate (CR) and seeds (SE). The morphometric parameters of the cells identified in each structure such as area (A), perimeter (P), shape factor (SF) and Feret's diameter (FD) were quantified by digital image analysis (DIA) using light microscopy and thus defined the average size and approximate shape of the cells. Additionally, through the application of DIA to the micrographs captured with the stereomicroscope, five
... La vainilla común pertenece a la familia de las orquídeas y recientemente ha sido clasificada dentro de una nueva subfamilia, Vanilloideae (Cameron, 2005); el género Vanilla abarca 110 especies de las cualesúnicamente tres se cultivan: Vanilla planifolia Jackson ex Andrews; Vanilla pompona Schiede y Vanilla tahitensis J. W. Moore (Ramachandra y Ravishankar, 2000;Besse y col., 2004). La vainilla verde carece de sabor y aroma, por lo que es necesario un proceso artesanal (beneficio) para la formación de los compuestos volátiles responsables del aroma (Dignum y col., 2001;Dignum y col., 2002;Ruiz-Terán y col., 2001;Havkin-Frenkel y Frenkel, 2006;Pérez-Silva y col., 2006). El beneficio toma entre 3-6 meses, dependiendo de las regiones y de los países productores (Ramachandra y Ravishankar, 2000), la forma de hacerlo es diferente para cada región del mundo y de acuerdo con algunos investigadores (Odoux, 2000;Ramachandra y Ravishankar, 2000) se divide en cuatro etapas principales: marchitamiento, sudoración, secado y acondicionamiento. ...
Article
Full-text available
In this work, microstructural changes of the tissues of vanilla were evaluated during the curing, using an Environmental Scanning Electron Microscope (ESEM). The morphometric parameters: area (A), perimeter (P), shape factor (SF) and compactness (C) of each tissue (epicarp, mesocarp and vascular bundle) were quanti�ed by Digital Image Analysis (DIA). Results indicated that curing induces structural disruptions of the vanilla tissues which is more pronounced in the mesocarp. Shape factor and compactness showed highest values in pods subjected to 10 cycles of sunning-sweating (10 SS) in which the highest concentration of vanillin and the lowest water looses were detected. It is possible to recommend a reduction of curing time from 20-25 SS cycles to 10.
... This indicates that freezing and thawing may have caused a more extensive but uniform tissue disruption of the green vanilla beans compared to mechanical bruising. As shown by previous researchers, the greater the level of tissue disruption, the higher the level of vanillin production (Ruiz-Teran et al. 2001;Ovando et al. 2005;Odoux et al. 2006;Havkin-Frenkel and Frenkel 2006;Waliszewski et al. 2007). Table 1 shows the comparison of vanillin content in vanilla beans subjected to mechanical bruising and freezing and thawing, with and without the added enzymes (cellulase, pectinase, and β-glucosidase) after drying, on a dry weight basis. ...
Article
Vanilla is one of the most popular and valuable flavorings worldwide. Natural vanilla is extracted from the cured vanilla pods of Vanilla planifolia. The main aromatic compound in vanilla is vanillin, a phenolic aldehyde, which is produced by enzymatic hydrolysis of glucovanillin during the curing process. Although the amount of glucovanillin in the uncured green bean is present at the level of 10–15%, only an average of about 2% vanillin yield results from the traditional curing process. Therefore, the aim of the experiment was to increase the vanillin yield by obtaining the maximum conversion of glucovanillin. This was obtained by the addition of exogenous cellulase, pectinase, and beta glucosidase enzymes and cellular-damaging techniques on green Tongan vanilla beans to enhance the interaction between glucovanallin substrate and enzymes and successfully achieved vanillin production ranging from 4.25 to 7.00% on a dry weight basis. These techniques may be further refined and translated into industrial curing practices for improvement of natural vanillin yield from vanilla beans.
Chapter
Full-text available
The vanilla plant is an orchid mainly commercialized for the production of vanillin. This compound is considered the second largest natural flavoring source in the world. In recent years, price of vanillin has increased considerably, which has generated the necessity of improving the quality of the plant materials. There are few works related to the isolation, fusion and regeneration of protoplasts in vanilla, not allowing to boost the benefits that this technique can generate for crop breeding. This work presents efficient protocols for protoplast isolation and fusion from leaf and protocorm like bodies (PLBs) of vanilla (Vanilla planifolia and Vanilla pompona) in order to contribute to the genetic improvement of the genus. A three-week pre-treatment in the dark was standardized before placing the explants in an osmotic solution (0.06 M MES, 0.4 M mannitol, pH 5.7) for one hour at 50 r.p.m. This solution was then replaced with different enzymatic solutions for three hours at 25 ± 1 ºC and 50 r.p.m. The isolated protoplasts were filtered (320 mesh), centrifuged (100 xg for 5 min) and re-suspended in a 0.6 M sucrose solution. Subsequently, a washing solution (50% MS salts with 0.03 M MES and 0.2 M mannitol, pH 5.7) was added to separate protoplasts by flotation-centrifugation. Protoplasts` Protoplasts`viability was evaluated with 0.01% Evans blue. Enzymatic solution containing 1% cellulase, 1% pectolyase and 0.5% hemicellulase (pH 5.7) yielded the highest amount of protoplasts from V. planifolia leaf explants (2,9 x10 5 ± 0,7 x10 5 protoplasts/g fresh weight, with a viability of 81%) and from PLBs (2,8 x10 5 ± 0,7 x10 5 protoplasts/g fresh weight, viability 80%). In V. pompona, yields of 2,8 x10 5 ± 0,8 x10 5 protoplasts/g fresh weight from leaf explants (viability 79%) and 2,5 x10 5 ± 0,8 x10 5 protoplasts/g fresh weight from PLBs (viability 79%) were obtained. For electrofusion, a hypoosmolar solution (Eppendorf®, HA, AL) was used, and the alignment and fusion parameters were standardized. The fusion parameters U1 = 8 V, 60 s; A = 170 V, 30 μs, n 3; U2 = 8 V, 60 s generated the highest number of fusion events (8.9%). Highest number of microcalli (plating efficiency 9.4%) was observed on media containing 50% MS salts supplemented with MS vitamins, 1% CaCl2, 1 mg/L benzyladenine, 1 mg/L 2,4-dichlorophenoxyacetic acid, 0.2 M mannitol, 0.03 M 2-(N-morpholino)ethanesulfonic acid, 1 g/L hydrolyzed casein, 20 g/L sucrose, and 6.2 g/L agar as a gelling agent (pH 5.7) in diffuse light (16 hours to 1000 lux).
Article
Full-text available
This review deals with the Vanilla plant: history; botanical description; chemistry of vanilla beans; curing of vanilla beans; commercial extraction of vanilla flavour; standard specifications and uses of vanilla flavour. The production of vanillin by both chemical and biotechnological methods is described. The biotechnological production of vanilla flavour metabolites by plant tissue/cell culture, microbial biotransformation and molecular approaches is also presented, together with a discussion on economic and safety considerations.© 2000 Society of Chemical Industry
Article
This review covers the most recent literature on vanilla research. Besides the curing process, chemistry in green and cured beans, as well as studies on the biosynthetic pathways of the most important aroma compounds are discussed. Despite intensive research on the curing process, the traditional curing procedures are still widely used. The role of enzymes involved in the curing process is not fully understood.The biosynthesis of vanilla aroma compounds is still under investigation. Data obtained from plant cell cultures are not always in accordance with those from the plant. The glycosylation of the compounds in vivo is still a point of study. Alternative routes to vanillin involving microbial biotransformations are outlined.
Article
The extraction method for beta-glucosidase from green vanilla beans has been studied. The effect of storage of green beans and protein extracts on beta-glucosidase and peroxidase activity was investigated: the best method, resulting in the highest enzyme activities, particularly for glucosidase, was through extraction of very fresh green beans in the presence of BisTris propane buffer at pH 8. The best method for storage of the extracts was at -80 degrees C after addition of 15% glycerol, when over 90% of initial activity was still present. Peroxidase activity did not change in frozen beans or in frozen extracts.