Qingchun Liu and Xingbo Wu
Vanilla is a relatively new crop south Florida, particularly Miami-Dade County. The focus of this article is to provide information on flower pollination, bean production and process, and vanillin extraction from the bean pods for beginner growers of this specialty crop.
Flowering and pollination
Vanilla vines are ready for bloom around 2-3 years after planting the cuttings, which is triggered by low light intensity and humidity. Vanilla flowers once a year, usually between February and April in south Florida. It is March to April for Vanilla planifolia, the major commercial species. Flowers open in the early morning and are viable for only a day (for most varieties). Vanilla flowers in clusters, also called raceme.
Due to the presence of a rostellum between the stigma and pollinia that prevents auto-pollination and a lack of effective natural pollinators, vanilla flowers need to be hand-pollinated to produce bean pods that are used to produce vanilla extract. For V. planifolia, its flowers are self-compatible when the rostellum is bypassed with a toothpick (https://www.youtube.com/watch?v=AB61HX0QO6s). Pollination is recommended before noon and no more than 9 flowers per raceme to avoid producing small-sized, less valuable beans and overstressing the plants. According to Roland, pollinating the flowers on the sides and bottom of the raceme will encourage them to grow straighter bean pods, while beans that come out of the top of the raceme will grow in a curve (https://vanillery.com/its-the-peak-of-the-vanilla-flowering-season). Bean pods are sensitive to low humidity during the first two months and need 7-8 months to reach maturity for processing. The change of temperature and humidity initiates the ripening process of bean pods. Do not harvest too early, as nothing can cure unripe beans. As the beans ripe, their color changes from green to yellow, and a dark yellow/orange color at the bean tips is the sign of a ripe bean. However, overmatured bean pods will split, which reduces the quality of the bean pods.
Bean processing
Not all species of vanilla have aromatic beans, and only V. planifolia and V. x tahitensis are recognized as the sources for vanilla extract by the FDA in the United States. For mature bean pods, it is not recommended to leave them in the refrigerator for too long, but process them in a timely manner after harvesting (1-2 days). Or you can store the washed beans in a freezer bag in the freezer till you have a large quantity. Processing the bean pods includes 5 steps:
1, Washing: to make them clean.
2, Killing/blanching: to stop the bean growth. For freshly harvested beans, dip them in hot water for 2-5 minutes (63 °C); for frozen beans in a freezer bag (at least 1 day), dip them in hot water for a minute or so to get them hot.
3, Sweating: to encourage the formation of vanillin (the primary component of vanilla extra) inside the pods, place the pods in an airtight container right after killing (to retain humidity) at 45-50 °C for 2-3 days.
4, Drying: to reduce the moisture content in the bean pods by drying them naturally alternating between sun and shade, or keeping pods at 30-32 °C and 30% humidity. Keeping sweated beans under low humidity is critical to prevent mold. Dry the beans slowly until the moisture content lowers to 25-30%, which can take 2-4 weeks. The properly dried beans should be shiny but feel soft.
5, Conditioning/aging: to store the dried bean pods in closed boxes, sometimes lined in wax paper, to allow the flavor to fully develop and stabilize. This process can take several weeks or even months.
Beans can be shipped during the conditioning process. The price of cured bean pods could range from $50 to $600 per kilogram.
Bean grades
There are two grades for cured vanilla beans, A and B, based on their appearance and moisture content. Grade A beans appear dark in color and have higher moisture content, 25-35%. Grade B beans, referred as ‘extract grade’, are thinner and have a moisture content of around 20%. Though beans of both grades are suitable for vanilla extract, beans of grade A are sold on a by-the-bean basis, while beans of grade B are sold by their weight.
Vanilla extract
According to the FDA standard, vanilla extract is the solution in aqueous ethyl alcohol of the sapid and odorous principles extractable from vanilla beans. In vanilla extract, the content of ethyl alcohol is not less than 35 percent by volume, and the content of vanilla constituent is not less than one unit (13.35 oz of vanilla beans) per gallon.
There are procedures available online for homemade vanilla extract, which could take 6 months to a year for optimal flavor development. We are experimenting with a higher temperature during the initial infusion process to shorten the overall time of preparation. We will update this publication with such information when available.
References
Wu, X., Moon, P., Chambers, A., and Crane, J. 2024. Vanilla growing in south Florida. EDIS HS1348. https://doi.org/10.32473/edis-hs1348-2024
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