PROCESSING AND MANUFACTURING
CURING OF VANILLA BEANS
Quality requirements: The primary quality determinant for cured vanilla beans is the aroma/flavor character. Other factors of significance in quality assessment are the general appearance, flexibility, the length and the vanillin content. The relative importance of these various quality attributes is dependent upon the intended end-use of the cured beans. Traditionally, the appearance, flexibility and size characteristics have been of importance since there is a fairly close relationship between these factors and the aroma/flavor quality. Top-quality beans are long, fleshy, supple, very dark brown to black in color, somewhat oily in appearance, strongly aromatic and free from scars and blemishes. Low-quality beans are usually hard, dry, thin, brown or reddish-brown in color and possess a poor aroma. At one time, the presence of a surface coating of naturally exceeded vanillin crystals (frosting) was regarded as an indicator of good quality. However, this is no real guide and Mexican vanilla, which has the best reputation for quality, rarely "frosts". A high vanillin content is desirable but this value is not directly commensurate with the overall aroma/flavor quality of the bean. Much of the vanilla entering Western markets is used for the preparation of vanilla extract, and for this purpose the appearance of the beans is not of prime importance.
TRADITIONAL CURING METHODS
A number of procedures have been evolved for the curing of vanilla, but they are all characterized by four phases.
A) "KILLING" OR WILTING: This stops further vegetative development in the fresh bean and initiates the onset of enzymatic reactions responsible for the production of the aroma and flavor. Killing is indicated by the development of a brown coloration in the bean.
B) "SWEATING": This involves raising the temperature of the killed beans to promote the desired enzymatic reactions and to provide a first, fairly rapid drying to prevent harmful fermentation. During this operation, the beans acquire a deeper brown coloration and become quite supple, and the development of an aroma become perceptible.
C) DRYING: The third stage entails slow drying at ambient temperature, usually In the shade, until the beans have reached about one third of their original weight.
D) CONDITIONING: In the final stage, known as "conditioning", the beans are stored in closed boxes for a period of three months or longer to permit the full development of the desired aroma and flavor.
Various traditional procedures for curing vanilla beans are known all over the world (Mexican method, Tahitian method, artificial method). But the most important one used in Indian Ocean (Madagascar, Comoros, Reunion) and also in Indonesia is "the Bourbon" method. In Indonesia, from place to place the Bourbon method or the Mexican method or sometime and adaptation of both methods is used accordingly with the various geographic and weather conditions.
THE "BOURBON" METHOD
On arrival at the curing factory, the beans are sorted according to the degree of maturity, size, and into split and unsplit types. Batches of beans, weighing 25 - 30 kg, are loaded into open-work cylindrical baskets which are then plunged into containers full of hot water heated to 60 - 63 degrees Celsius, over a wood fire. Batches of beans which will eventually make up the top three qualities are immersed for 2 - 3 minutes, while smaller and split beans are treated for less than 2 minutes. The warm beans are rapidly drained, wrapped in a dark cotton cloth and are placed in a cloth lined sweating box. After 24 hours, the beans are removed and inspected to separate those which have not been properly killed. The next stage of sun-drying is carried out on a plot of dry, easily drained ground, at some distance from roads to avoid contamination by dust. The killed beans are spread out on dark cloths resting on slatted platforms, constructed from bamboo and raised 70 cm above the ground. After one hour of direct exposure to the sun, the edges of the cloth are flooded over the beans to retain the heat. The cloth-covered beans are then left for a further two hours in the sun before the blanket is rolled up and taken indoors. This procedure is repeated for 6 - 8 days until the beans become quite supple. The third stage involves slow drying in the shade for a period of 2 - 3 months. The beans are spread on racks, mounted on supports and are spaced 12 cm apart in a well-ventilated room. During this slow drying operation, the beans are sorted regularly and those which have dried to the requisite moisture content are immediately removed for conditioning. In some localities in Madagascar and most commonly in Indonesia where the weather is frequently inclement during the sun and indoor-drying periods of curing, ovens set at 45 - 50 degrees Celsius have traditionally been used. Conditioning of the beans is carried out in a similar manner in Madagascar and Mexico and takes about 3 months for completion. The overall curing process for Bourbon vanilla lasts 5 - 8 months. The main harvesting season in Madagascar extends from June to early October.
GRADING AND PACKAGING
After conditioning, the cured beans are given an airing and are restraightened by drawing through the fingers. The beans are then subjected to a final sorting into grades and according to their length, prior to bundling and packaging for shipment. The length of the beans is an important determinant of the price which the whole beans will fetch. Grading system differ somewhat between producing countries, but beans are generally classified into three categories: unsplit beans, split beans and "cuts". The last type has traditionally consisted of beans which have been attacked by mold and have had the infected portion cut away. Very small and broken beans of poor aroma quality are usually combined with the "cuts" from moldy beans. It should be noted, however, that "cuts" do not always consist of entirely of poor quality beans. In Mexico, "cuts" usually comprise 10 - 20 percent of production in a normal year but, in years of good prices, the smaller curing firms would often cut all their beans prior to curing because drying times were shortened. Also, the artificially dried cut beans which have entered the market in recent years are of a good aroma and flavor quality and are produced specifically for extraction.
The vanilla of Madagascar, the Comoros Islands, and Reunion is classified into five main grades of whole and split beans plus and additional category known as "bulk" which is comprised of cuts. The grades of whole and split beans are also sub-divided according to size. The minimum acceptable length for the top five grades in the major producing area of Madagascar is 12 cm while for Nossi-Be and the Comoros Islands it is 10 cm (Frere, 1954). Madagascar beans are first sorted to separate beans below 12 cm in length and then the whole and split beans are classified into grades according to their aroma, moisture content, and appearance. The five main categories for Madagascar whole beans are as follows: "Extra" Whole, supple, unsplit beans, free of blemishes, possessing a uniform chocolate-brown color and an oily luster. The aroma clean and delicate. "1st" Similar to the "extra" grade but not quite so thick and of a lesser appearance. "2nd" Somewhat thinner beans with a chocolate-brown color but with a few skin blemishes. The aroma is good. "3rd" Thinner, more rigid beans with a slightly reddish chocolate-brown color. The aroma is fair. "4th" Rather dry beans with a reddish color and numerous skin blemishes. The aroma is ordinary. Splits are sorted into categories corresponding to those for whole beans. Foxy splits are thin, hard, and dry, short types with a reddish-brown color.