Handbook of Vanilla Science and Technology

This method is markedly different in one important aspect from all other curing methods, as there is no artificial killing step involved. Mature green beans are allowed to reach on-the-vine senescence, characterized by yellowing and tip-browning of the beans, before harvesting for further curing. Next, beans are stacked in a cool environment for a few days to complete the browning process. The next stage consists of drying in the morning hours followed by stacking in piles for sweating for the remainder of the day, a process lasting for 15 to 20 days. The drying process is completed by holding cured beans in well aerated shade. In the final conditioning stage, beans are held in cases for 60 to 90 days.

6.9.1.4 Other traditional curing methods

Scarification is used to kill beans in Guadeloupe. One to two millimeter deep scars are made lengthwise into the green vanilla pod, and scarred beans are then wrapped in a blanket and subjected to the hot sun. Sweating and slow drying are similar to the Mexican method (Arana 1945). Childers and Cibes (1948) describe a hot water killing method in Puerto Rico, adopted from the traditional Bourbon process, consisting of immersing green beans in hot water (around 80°C) for 30 seconds. The process is repeated 3 times at 10-second intervals. Drained and blanket-wrapped beans are then placed in the sweating box overnight. Hot water treatment, at 70°C and only 2 dippings, is repeated on the second day and again on the third day at 65°C with only 1 dipping. Two hours sunning every day followed by sweating is repeated for 7 days, at the end of which the beans become ready for slow air or oven drying. In the “Guiana method” beans are killed in the ashes of a wood fire until they begin to shrivel, then wiped and rubbed with olive oil, and air dried (Purseglove et al. 1981). These curing methods are moot issues, however, because bean cultivation in these locations has ceased altogether or is of no commercial significance.

6.9.1.5 Indonesian curing of vanilla bean

Growers in Java and other Indonesian islands carry out essentially the Bourbon curing method. However, in the past the practice lacked in consistency with respect to bean maturity and appropriate use of curing protocols, resulting in varied and often inferior products. This situation has been rectified by the proliferation of professionally-run curing houses, resulting in the production of good quality vanilla. About one-third of the total cured beans sold worldwide come from Indonesia.

6.9.2 Refinement of traditional curing methods

Comparative studies on various commercial curing methods, carried out in Porto Rico by Arana (1944) and Jones and Vincente (1949a), led to the conclusion that all the various killing methods, namely, Mexican sun-killing, Mexican oven-killing, the Bourbon hot water scalding, Guadeloupe scratching, exposure to ethylene, and freezing gave a satisfactory product. However, the Bourbon scalding method was found to be preferential, based on ease of handling, resistance of killed beans to mold growth, finished product appearance, development of fine fragrance, vanillin content, and total phenol value. A related study in India (Muralidharan and Balagopal 1973) concluded that, although the Guiana curing process resulted in good flavor, US importers preferred the color and appearance of cured beans subjected to the Mexican or hot water killing method of vanilla beans. These studies indicate that flavor, although an important attribute, is judged in an overall context of other important features that contribute to quality. Arana (1944) found that sweating and drying of beans, carried out in an electric oven set at 45°C, had lower incidence of mold growth. Moreover, drying was uniform and faster than sun drying, was less cumbersome and resulted in overall superior bean quality. Further studies revealed that sweating of beans at 38°C produced a better product than accelerated drying at 45°C (Rivera and Hageman 1951), suggesting that similar ambient temperature regimes occurring in tropical vanilla growing regions might be exploited for drying and conditioning of cured beans (Rivera and Hageman 1951; Broderick 1956a,b).

6.9.3 Novel curing methods