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4 Harvesting, yield and post-production activities

4 Harvesting, yield and post-production activities

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Vanilla



331



flavour associated with the product. Curing can be defined as the sum total changes that

occur during the primary processing of a given raw material to a desired finished product,

which is ready for market (Jones and Vicente, 1949a). Curing stops the various natural

vegetative processes in the harvested beans and promotes the metabolic reactions involved

in the generation of the aromatic flavouring constituents in the cured material (Arana, 1944).

It can be broadly classified into two: (1) changes that involve a simple loss of water,

achieved through drying, and (2) changes that involve chemical transformation, which is

usually accompanied by hydrolytic and oxidative changes with or without the aid of

enzymes. In vanilla, the latter changes are more critical.

Vanillin (Fig. 20.4a), the main flavouring chemical of vanilla, is present only in trace

amounts in the green mature beans; upon curing, however, vanillin content increases

(Arana, 1943). The chemical compound from which vanillin is derived occurs in the

uncured pods in the form of a glucoside called glucovanillin (Arana, 1945). During the

curing process, this glucoside is hydrolysed to form vanillin and glucose through the action

of a β-glucosidase. The activity of this enzyme changes with the maturity of the vanilla

beans, being negligible in the green beans and highest in the split, blossom-end yellow

beans. Spatially, all of the enzyme is located in the fleshy portion or thick wall of the pods,

where most of the glucovanillin is also concentrated (Arana, 1943). Along the bean length,

40% of glucovanillin has been detected in the blossom end, another 40% in the middle and

the remaining 20% in the stem end. Other flavour constituents such as p-hydroxybenzoic

acid, p-hydroxybenzaldehyde and vanillic acid (Fig. 20.4b–d) are also present in the green

beans in their glycosidic forms and are released through enzymatic hydrolysis during curing

(Ranadive, 1992).

The splitting of vanillin from the glucoside is initiated during the early part of the curing

process, but the full development of flavour and aroma occurs only after a considerable

period of pod preparation and conditioning (Arana, 1943; Jones and Vicente, 1948).

Treatment of cured beans with β-glucosides enhances vanillin content, suggesting incomplete hydrolysis, probably as a result of (a) insufficient amount of native enzyme, (b)

inadequate enzyme–substrate interaction or (c) inactivation of enzymes by oxidized phenols

liberated during curing (Ranadive, 1992). Chemical changes other than enzymatic hydrolysis

may also contribute a great deal to the quality of cured vanilla. Balls and Arana (1941)

suggested the possible role of a peroxidase system in the oxidation of vanillin to quinone

compounds. These substances possess more complex structure with presumably different

aroma that can add to the total flavour of the cured product. Wild-Altamirano (1969)

reported that proteinase activity declines with pod growth while the activities of glucosidase, peroxidase and polyphenoloxidase increase with pod age, being maximum near or at

ripening. The trend in enzyme activities is indicative of the potential role of the various

products derived from catalysed reactions in the full development of the characteristic

flavour and aroma of cured beans.

In general, vanilla curing follows four successive steps: (1) killing or wilting, (2)

‘sweating’, (3) drying and (4) conditioning. Killing or wilting is the initial step in inhibiting

the natural changes in vanilla beans. It is achieved through various techniques, depending

upon the producing country (Arana, 1945; Theodose, 1973). In Mexico and Indonesia, the

most popular method is sun wilting. In this method the beans, which are contained on racks

covered with dark woollen blankets, are simply heated under the sun. Wilting with the use

of an oven maintained at 60ºC is alternatively practised in Mexico. In Madagascar, Réunion

and Comores, beans are killed by dipping in hot water for a few minutes (scalding technique)

(Fig. 20.5). On the island of Guadeloupe, beans are gently scratched on the surface with the

use of a pin embedded in a cork ring prior to sun exposure. Wilting by freezing has been



© 2004, Woodhead Publishing Ltd



Fig. 20.4



Chemical structures of the major flavouring constituents of vanilla.



developed in Puerto Rico for experimental purposes only. In this technique the beans are

refrigerated until frozen and then thawed naturally at room temperature. Some of the

advantages and disadvantages of these types of wilting are presented in Table 20.1.

The successive steps after killing are more or less similar for the different countries

exporting vanilla. ‘Sweating’ or heating is done to develop the proper texture and flexibility.

This is accomplished through either of two ways: (1) daily sun exposure for about six hours,



© 2004, Woodhead Publishing Ltd



Vanilla



Fig. 20.5



333



Implements used in the processing of beans using the hot water treatment.



Table 20.1 Advantages and disadvantages of different methods of wilting vanilla beans

Method of Wilting



Advantages



Sun wilting



Method is simple

High degree of bean splitting

Does not require additional equipment Beans mould easily



Oven wilting



Short period of time for sweating and

drying

Fewer split beans

High vanillin content



Hot-water wilting



Few mouldy beans and medium degree Longer period of drying

of splitting

Low vanillin content and phenol

Easiest and most satisfactory for the

value

inexperienced curer



Scratching



Short period of time for sweating and

drying

Low vanillin and phenol values

Low degree of splitting



High susceptibility to mould

Poor flexibility of the beans in the

stem end

Dependent on the skill and care of

the curer



Freezing



Practically no mould

Sophisticated aroma

Beans are picked at the best stage of

maturity and kept in the refrigerator

until enough beans are accumulated



Medium values for phenol, vanillin

content and percentage splitting



Source: Arana (1944, 1945).



© 2004, Woodhead Publishing Ltd



Disadvantages



High percentage of mouldy beans

Medium phenol value



Fig. 20.6



Sweating of vanilla beans.



with the beans covered with woollen blankets for the remainder of the day (Fig. 20.6) or (2)

incubation in ovens at 45ºC at high relative humidity (Arana, 1944, 1945). The significant

change in colour of the bean to chocolate brown is manifested at this stage (Balls and Arana,

1941). Sweating is terminated when beans become pliable. The next step is slow drying,



© 2004, Woodhead Publishing Ltd



Vanilla



Fig. 20.7



335



Drying of cured beans in open shelves.



which is normally carried out at room temperature (Fig. 20.7). Drying is needed to lower the

moisture content of the beans to a desirable level, usually 15–30% (Jones and Vicente,

1948). Finally, in conditioning the product is kept in closed containers at room temperature

for several months to allow the complete development of aroma (Fig. 20.8). In this last stage

beans are frequently examined for the presence of moulds. At the minimum, conditioning

lasts for three months (Arana, 1944).

An improved curing process using drying tunnels has been developed in Madagascar

(Theodose, 1973). This method relies on hot air, instead of heating by the sun, and produces

homogeneous, good quality beans in large quantities (40 tonnes dry vanilla in one season).

Gillette and Hoffman (1992) present a very good comparison of the curing process

associated with the different types of vanilla beans.

The nature of curing procedures adopted affects the quality of cured beans. Aside from the

influence of method of wilting, Arana (1945) pointed out that non-uniformity in drying,

sweating and drying under the sun, use of dirty blankets and improper ventilation in curing

rooms, all contribute to the susceptibility of beans to mould infection, which in turn lowers

the quality of the product. He further noted that the moisture content of cured beans should

be properly controlled to obtain the full development of the vanilla aroma. The aroma of cured

beans with 50–54% moisture is characteristically fermented; those with 24–27% moisture,

sophisticated and well developed; while those with 31–34% moisture, just desirable.

Factors other than those related to curing protocol are also known to influence the quality

of the final product. Vanilla beans that ripen early in the harvesting season yield higher

quality cured beans than those gathered at mid-season or late in the season (Jones and

Vicente, 1949b). The best cured material comes from pods harvested when the blossom-end

section is yellow. When picked prior to this stage, beans give an undeveloped vanilla

flavour; when beyond, a full but undesirable flavour is obtained (Broderick, 1955a).

Immature beans when processed are also readily attacked by fungi (Arana, 1945).



© 2004, Woodhead Publishing Ltd



Fig. 20.8



Dried beans are placed in plastic bags and conditioned for several months.



Grading

The grading and classification of cured vanilla beans vary depending upon the producing

countries. Mexican beans, for example, are usually graded (from the highest to the lowest

quality product) as ‘prime’, ‘good to prime’, ‘good’, ‘fair’ and ‘ordinary’, while Bourbon

beans are graded as ‘prime’, ‘firsts’, ‘seconds’, ‘thirds’, ’fourths’ and ‘foxy splits’ (Merory,

1960). Classification is commonly based on: bean integrity (either whole, broken or split),

bean length, appearance (particularly colour and surface blemishes), moisture content and

aroma quality (Arana, 1945; Heath and Reineccius, 1986).

Packaging

After sorting, the beans are tied into bundles, usually 70 to 130, weighing between 150 and

500 g (Heath and Reineccius, 1986). These are then packed into cardboard or tin boxes lined

with waxed paper. The beans are now ready for shipment.



© 2004, Woodhead Publishing Ltd



Vanilla



337



Table 20.2 Reported values of major flavour constituents of cured vanilla beans from various

geographical sources

Source



Vanillin



Vanillic acid



p-Hydroxybenzaldehyde



p-Hydroxybenzoic acid



–1



(mg 100 ml )

Mexico

Madagascar

Comores

Java/Indonesia

Uganda

Tonga

West Indies

Costa Rica

Jamaica

Tahiti



18–100

47–216

115–154

63–142

47–186

197–320

20–136

135–161

216–265

54–120



8–23

12–23

8–13

7.7–11

5–10

7.6

15–22

12

4.2

4–5



5–7

6–13.7

9–13

7–10

5–8

10

2–6

14

8.4

4–13



2–7

2–5.6

2–7

2–4

1–6

2.1

2–4

5.2



16–32.8



Sources: Smith (1964), Archer (1989), Ranadive (1992).



20.4.2 Flavour constituents

The flavour famously associated with vanilla results from a complex and varied mixture of

chemical compounds. About 170 volatile constituents, most of which occur below 1 ppm,

have been reported in vanilla by Klimes and Lamparsky (1976). Vanillin serves as the major

flavour backbone, occurring in levels from 1.52 to 2.42% of bean dry weight (Cowley,

1973). Other major components are p-hydroxybenzoic acid, p-hydroxybenzaldehyde,

vanillic acid, p-hydroxybenzyl alcohol (Fig. 20.4e) and vanillyl alcohol (Fig. 20.4f)

(Anwar, 1963; Smith, 1964; Herrmann and Stockli, 1982).

The type and levels of the major flavouring components vary depending upon the species

and geographical source (Table 20.2). Tahiti vanilla stands out among the different types of

beans for exhibiting higher levels of p-hydroxybenzoic acid. Other components present in

V. tahitensis that are not detected in V. planifolia are p-anisic acid, p-anisaldehyde and

piperonal (heliotropin) (Fig. 20.4g–i) (Ranadive, 1992). Vanillons (V. pompona, Guadeloupe

vanilla) contains vanillin, p-hydroxybenzoic acid, vanillic acid, p-hydroxybenzaldehyde, panisic acid, p-anisaldehyde and p-anisyl alcohol (Fig.20.4j), but not piperonal (Ehlers and

Pfister, 1997).

The hydrocarbon profile of the lipidic fraction, which also contributes to flavour, of

different types of beans has also bean investigated by Ramaroson-Raonizafinimanana et al.

(1997). Hydrocarbon content varies between 0.2 and 0.6%. A total of 25 n-alkanes, 17

branched alkanes and 12 alkenes have been identified. Distinction between types of vanilla

is also evident. Vanilla fragrans from Réunion is rich in n-alkanes (46%) and n-1-alkenes

(26%), while V. tahitensis from Tahiti contains predominantly branched alkanes (47% for

3-methylalkanes and 33% for 5-ethylalkanes). Also present in the lipophilic fraction before

saponification in the two vanilla species are three new γ-pyrones: 2-(10-nonadecenyl)-2,3dihydro-6-methyl-4H-pyran-4-one; 2-(12-heneicosenyl)-2,3-dihydro-6-methyl-4H-pyran-4-one,

and 2-(14-tricosenyl)-2,3-dihydro-6-methyl-4H-pyran-4-one (Ramaroson-Raonizafinimanana et al., 1999). γ-Pyrones are intermediates in the synthesis of biologically

important compounds. A review of other flavour components as a function of vanilla species

can be found in Richard (1991).

Werkhoff and Guntert (1997) characterized for the first time in Bourbon vanilla beans 15

esters that are derived from cyclic and acyclic terpene alcohols and aromatic acids. Among

those isolated, pentyl salicylate and citronellyl isobutyrate are considered new natural

compounds.



© 2004, Woodhead Publishing Ltd



Vanilla also contains resins, gums, amino acids and other organic acids, which all

contribute to the distinct flavour characteristics of the cured beans. An enumeration and

discussion of these constituents is provided by Purseglove et al. (1981).



20.5



Uses



There is probably no other spice material or aromatic plant comparable to vanilla in terms of

wide scope of application. The use of vanilla is generally grouped into three: as a ubiquitous

flavouring material, as a critical intermediary in a host of pharmaceutical products, and as a

subtle component of perfumes. As a flavouring agent, vanilla is a popular and most preferred

ingredient in the preparation of ice cream, milk, beverages, candies, confectioneries and

various bakery items. In the pharmaceutical and chemical industries, vanillin serves as an

important intermediate in the manufacture of: L-dopa (the anti-Parkinsonian drug), methyl

dopa (a compound with anti-hypertensive and tranquilizing properties), papaverine (treatment of heart problem), trimethoprim (anti-bacterial agent), hydrazones (2,4-D-like

herbicide), and anti-foaming agent (in lubricating oils) (Rosenbaum, 1974; Hocking, 1997).

Vanilla in perfumery was initially incorporated to complement the scent provided by

tonka extract. It became a perfume ingredient to reckon with when Franỗois Coty, who is

often regarded as the first of the great perfumers of modern times, used it in ‘L’Aimant’

(Groom, 1992). Vanilla subsequently became the principal note of about 23% of all quality

perfumes, e.g. ‘Amouge’, ‘Bois de Isles’, ‘Jicky’, ‘Habanita’.



20.6 Vanilla products

The cured beans are further processed to produce the various vanilla products. This is

commonly accomplished in the importing countries. The different products developed from

vanilla are described below.



20.6.1 Vanilla extract

The major product derived from cured vanilla is an alcoholic essence, which is commercially known as vanilla extract. The vanilla flavour is obtained through solvent extraction

with the use of the best grade of ethanol. Generally, the basic process in the preparation of

vanilla extract involves (1) the reduction of the bean size using a comminuting machine and

(2) the subsequent alcohol extraction of the macerated beans through a series of percolation

techniques (Arana, 1945; Heath and Reineccius, 1986). For best results Merory (1956,

1960) recommends the following protocol. Three consecutive extractions are done with

varying amounts of the menstruum – a maximum of 65% ethanol for the first extraction,

35% for the second and about 15% for the third. Each of these takes place for a minimum of

five days. Extraction is done in a continuous slow flow, the percolate collected in fractions

and later blended to yield the final product. The extract is filtered or centrifuged and the

alcohol content is adjusted to meet market specifications. Vanilla extract is then stored in

stainless steel or glass containers. If the extract is aged for a period of about three to six

months, the delicate and subtle aroma for which vanilla is famous is fully realized.

The nutrient composition of a typical vanilla extract is listed in Table 20.3. Several

factors influence the quality of vanilla extract. These include: (1) method of curing, (2)

blending of different quality beans, (3) degree of maceration, (4) method of extraction,



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Vanilla



339



Table 20.3 Nutrient composition of vanilla extract (with 34.4% ethyl alcohol)

Nutrient



Value per 100 g of edible portion



Proximates

Water (g)

Energy (kcal)

Protein (g)

Total lipid (fat) (g)

Ash (g)

Carbohydrate, by difference (g)



52.58

288

0.06

0.06

0.26

12.65



Minerals

Ca (mg)

Fe (mg)

Mg (mg)

P (mg)

K (mg)

Na (mg)

Zn (mg)

Cu (mg)

Mn (mg)



11

0.12

12

6

148

9

0.11

0.072

0.230



Vitamins

Thiamin (mg)

Riboflavin (mg)

Niacin (mg)

Panthothenic acid (mg)

Vitamin B6 (mg)



0.011

0.095

0.425

0.035

0.026



Lipids

Fatty acids, total saturated (g)

Fatty acids, monounsaturated (g)

Fatty acids, total polyunsaturated (g)



0.010

0.010

0.004



Source: USDA National Nutrient Database for Standard Reference (2002). www.nal.usda.gov.



(5) level of alcohol in the menstruum and (6) appropriate period of ageing (Broderick,

1955b; Merory, 1960; Heath and Reineccius, 1986).



20.6.2 Vanilla oleoresin

Vanilla oleoresin is a dark brown, semi-fluid extract produced from solvent extraction of

macerated beans. It differs from vanilla extract in that the solvent used is completely

removed by evaporation under vacuum and the finer top-notes of the vanilla aroma are lost

or modified by heat treatment (Heath and Reineccius, 1986). Vanilla oleoresin can also be

obtained using CO2 under supercritical conditions, producing products considerably more

superior than those obtained by conventional extraction with organic solvents (Schuetz et

al., 1984). Yield of oleoresin is from 29.9% to 64.8% of bean dry weight (Cowley, 1973).



20.6.3 Vanilla sugar

Also known as powdered vanilla, vanilla sugar is prepared by mixing ground cured beans or

their oleoresin with sugar (Arana, 1945). Minimum sugar content is 30% (Heath and

Reineccius, 1986).



© 2004, Woodhead Publishing Ltd



20.6.4 Vanilla absolute

Preferred in perfumery products, absolute vanilla is obtained by selective solvent extraction,

using initially a non-polar solvent such as benzene followed by a polar solvent such as

ethanol (Heath and Reineccius, 1986).



20.7



Functional properties



Vanillin exhibits in vitro antifungal activity against the yeasts Candida albicans and

Cryptococcus neoformans (Boonchird and Flegel, 1982) Minimal inhibitory concentrations

of vanillin for C. albicans and C. neoformans were found to be 1250 and 738 µg ml–1, while

minimal fungicidal concentrations were 5000 and 1761 µg ml–1, respectively. It is also

reported to inhibit the growth of some food spoilage yeasts (e.g. Saccharomyces cerevisiae,

Zygosaccharomyces rouxii, Z. bailii and Debaryomyces hansenii) in culture media and

some fruit purées (Cerrutti and Alzamora, 1996).

The potential medical importance of vanillin is suggested by the following studies.

Vanillin has been found to possess antimutagenic effects in mice (Imanishi et al., 1990) and

bacteria (Ohta et al., 1988). In yeast, however, it is shown to be co-mutagenic and corecombinogenic (Fahrig, 1996). Vanillin offers protection against X-ray and UV

radiation-induced chromosomal change in V79 Chinese hamster lung cells (Keshava et al.,

1998).

Vanillin also functions as an antioxidant. At concentrations normally added to food

preparations, it offers significant protection against protein oxidation and lipid peroxidation

induced by photosensitization in rat liver mitochondria (Kamat et al., 2000). This study

shows the potential of using this popular flavouring chemical to inhibit oxidative damage to

membranes in mammalian tissues.

Sun et al. (2001) reported the bioactivity of five aromatic compounds extracted from the

leaves and stems of V. fragance against mosquito (Culex pipiens) larvae. Among the isolated

compounds, 4-butoxymethylphenol was the most toxic, exhibiting 100% mortality at

0.2 mg ml–1 within only 3 h of treatment. This was followed by 4-ethoxymethylphenol,

which was also the most abundant component. Vanillin, when given at 2 mg ml–1 for 10 h

exhibited more than 90% mortality The least toxic of the phenolic derivatives was 3,4dihydroxyphenylacetic acid. This compound, together with 4-hydroxy-2-methoxycinnamaldehyde, was isolated from vanilla for the first time. 4-Butoxymethylphenol has not been

reported to occur in natural form.



20.8



Quality issues and adulteration



The quality of cured vanilla beans is the result of confluent factors that run the whole gamut

of raw material production to curing. The agro-climatic conditions during cultivation,

coupled with various degrees of sophistication or non-sophistication of methods employed

in the preparation of harvested beans, can spell the difference in meeting market standards.

Physical attributes such as those enumerated in Section 20.4.1 provide the initial criteria

by which to judge the cured bean and assign it to a particular grade. The quality of vanilla

extract can be determined through chemical analysis, and Winton’s analytical values have

been employed in this regard (Table 20.4; Merory, 1960). The concentration of vanillin is

an important criterion, although organoleptic quality does not entirely depend on it. Various

flavour notes, described as characteristically woody, pruney, resinous, leathery, floral and



© 2004, Woodhead Publishing Ltd



Vanilla



341



Table 20.4 Some analytical values for vanilla extract

Type of analysis

Vanillin, g 100 ml–1 extract

Ash, g 100 ml–1 extract

Soluble ash, g 100 ml–1 extract

Lead number (Winton)

Alkalinity of total ash, N/10 acid 100 ml–1 extract

Alkalinity of soluble ash, N/10 acid 100 ml–1 extract

Total acidity, N/10 alkali 100 ml–1 extract

Acidity other than vanillin, N/10 alkali 100 ml–1 extract



Minimum



Maximum



Average



0.11

0.22

0.179

0.40

30.00

22.0

30.0

14.0



0.35

0.432

0.357

0.74

54.00

40.0

52.0

42.0



0.19

0.319

0.265

0.54

30.0

42.0

30.0



Source: adapted from Merory (1960).



fruity aromatics, also need to be considered (Gillette and Hoffman, 1992). Bourbon vanilla

serves as the standard by which to measure the chemical and sensory quality of other types

of vanilla. Imitation vanilla extract spiked with vanillin is less desirable than the natural

extract because the critical flavour notes are wanting (Fig. 20.9). Extracts of Indonesian



Fig. 20.9 Aroma and flavour sensory profiles of natural and imitation vanilla extracts. (Source:

Gillette and Hoffman, 1992.)



© 2004, Woodhead Publishing Ltd



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