This is only an excerpt of the full article that appeared in P&F Magazine. The full content is not currently available online.
Vanilla bean curing is a traditional process that has been carried out for hundreds of years, originating with the Totonac tribe of Mexico in the early 16th century. A major stimulus to its global proliferation was the development of hand pollination and vegetative propagation in the 1830s. The process is fairly simple, comprising five stages—blanching (or killing), sweating (or fermentation), sun drying/night storage, rack drying and conditioning.
The Biochemistry and Chemistry of Curing
The curing process is a complex and multifaceted sequence of interventions that takes place over a period of about 150 days, turning an unflavored ripe vanilla bean containing ca. 80% water into a cured vanilla pod that is aromatic, dark brown and which contains a water content of 20–30%. The process involves elements of biochemistry, chemistry, wound response, plant senescence and plant microstructure/compartmentation, and as such requires an integrated approach.
In general terms, the major biochemical activities are initiated during the sweating stage. Following the major loss of tissue integrity associated with the senescence process, there is activation of oxido-reductases as well as an increase in hydrolytic reactions. The consequences of these include hydrolysis of phenolic glucosides and subsequent oxidation of the liberated phenols by peroxidase and/or polyphenoloxidase. These same and other oxidative enzymes may also be involved in transformation of polyunsaturated membrane lipids by direct oxidation or indirectly by coupled reactions.