The traditional method of curing vanilla beans has a long history to it, and the process involves a good deal of scientific principle, all of which tends to produce the maximum amount of flavor which can be derived from the beans. Students of chemistry and biochemistry will have a field day learning about the individual phases involved in the traditional vanilla bean curing process, but for the rest of us, it's merely an interesting succession of events which ultimately results in the delightful flavor we love to use in desserts, drinks, and other flavorings.
The most common type of traditional curing is known as the Bourbon Process, so named for its development on the island where the first large-scale vanilla production occurred, the Ile de Bourbon, just off the coast of Madagascar. From beginning to end, the traditional curing process for vanilla beans will generally take between four and six months in order to reach its final completion. There are a number of complex biochemical and chemical reactions which take place during that time frame.
This is especially true during the fermentation phase when the action of endogenous vanilla bean enzymes is triggered, particularly those involving oxidoreductases. The reason it takes so long for all this traditional curing to take place is that it frequently depends on the weather, which provides necessary sunning periods. It's necessary to have that ideal sunny weather so that maximum microbial participation can be relied on for transformation of the beans, and for the generation of the distinctive vanilla flavor.
The blanching phase
This important step revolves around immersing green vanilla beans and hot water which has been heated up to approximately 65°C. The beans must stay in this scalding hot water for about three minutes, and the temperature must be monitored by some kind of thermometer. Typically the heating process will be conducted over a wood fire, and the vanilla beans would be placed into a metal container which holds the water.
During this process, all kinds of debris and any soil which might be clinging to the pods will be cleaned off. It also prevents the growth of any other type of vegetation on the pods, and triggers activation of several different enzymes within the plants. These enzymes are critical for the enhancement of flavor within the bean pods, and they also give the final product its distinctive color.
The fermentation phase
This is sometimes referred to as the sweating phase of the curing process, and it starts with removing the hot green beans from the container where they have been blanching. The beans are then quickly transferred into large wooden boxes which are closed and completely insulated, then covered over by wool blankets, so that minimal heat loss occurs. An alternative to this process is to wrap the beans in blankets or large bundles and stack them on top of each other with more insulating blankets surrounding them.
Now the sweating or fermentation process can take place, and after two days, the beans will turn dark brown and will become extremely supple to the touch. During this two-day period, it's important that the beans be maintained at a temperature around 40°C so that the appropriate sweating and fermentation process can occur.
This is the time frame when most of the flavor develops with the bean pods, as the scientific processes of enzymatic hydrolysis takes place. This is also when lipid oxidation and phenol browning occur, both of which contribute to the ultimate flavor of vanilla, and also cause it to be converted from a green color to a brownish hue.
Benefits of traditional curing
The benefits of the traditional curing process can be stated very succinctly and simply: mature green vanilla beans which have no defining flavor whatsoever, are converted into brown-colored bean pods which are loaded with distinctive and appealing vanilla flavor. All this flavor develops during the processing and curing of the beans, and while curing processes tend to vary from one country to another, they're all still fairly traditional in their approach.
After the scalding step has been carried out, the drained beans must go through a drying out process known as autoclaving, during which they will slowly cool down. Then the beans will go through cycles of sunning and fermentation, during which they are subjected to natural sunshine in the daytime, and then placed in boxes at night so that warmth can be retained.
This phase of alternating sunning and sweating is thought to be the primary factor in the development of characteristic vanilla flavor, attributable to bean-derived enzyme activities. After about 10 days of these alternating cycles of sunning and sweating, the vanilla bean pods will be placed on racks and dried out for an entire month. The best place to accomplish this drying will always be in some location which is exposed to the wind, but still sheltered, so as to drastically reduce any danger of fungal spoilage. In the last step, beans would then be placed in large wood case and allowed to simply rest for about three months, so that further enhancement of the flavor can take place. This protracted and drawn out curing process is one of the main reasons that vanilla beans are so expensive on the international market. Coupled with the high demand for vanilla, this six-month process from beginning to end represents a fairly significant time investment on the part of producers, so it stands to reason that the cost would be significant.
Any attempt to shorten this curing process would undoubtedly result in a compromised flavor, and the vanilla beans would never achieve the kind of distinctive fragrance which has made them so popular in the first place. Therefore, it's safe to say that the real benefit of the traditional curing process is that it literally imbues the vanilla bean pods with all the fantastic flavor that people around the world have come to appreciate from the vanilla plant.