Vanilla flavor production methods: A review

The biosynthesis of vanillin and other vanilla flavor compounds is still not completely understood. A better understanding of the pathways and how they are regulated may lead to better control of the production of the flavor and thus increase the commercial value of the pods. Non-synthetic vanilla flavor consists of over 250 components, with vanillin being the major one in terms of amount in the pod. Synthetic pure vanillin lacks complex flavor notes, and thus cannot replace vanilla in high quality products. Although customers prefer non-synthetic flavors, non-synthetic vanilla extract is approximately 200 times more expensive than its synthetic counterpart. To produce non-synthetic vanillin, fungi are being used for the biotransformation of vanillin precursors into vanillin. All plants contain several fungal endophytes which do not cause any symptoms of diseases; some endophytes are plant-specific and are thought to play a role in the interaction of the plant with its environment. Certain fungal endophytes have been reported to produce secondary metabolites previously thought to be produced by the plant; such fungi, particularly those isolated from pods, may play a role in the biosynthesis of vanillin and vanilla flavor compounds in the plant. This could be in the form of complete pathways, or parts of the vanillin pathway, interacting with the plant's vanilla flavor compounds biosynthesis machinery. Furthermore, studies on a possible role for endophytes may help to elucidate aspects of the vanillin biosynthetic pathway that still are under debate. Terroir effects on flavor, as observed for vanilla pods, may be due to the presence of microorganisms in the rhizosphere or in the plant itself. Based on this analysis, it is proposed that vanilla plant endophytes are studied and investigated for the presence of possible vanillin and vanilla flavor biosynthetic reactions. As a first step, fungal endophytes have been isolated from vanilla pods from Reunion Island and found to be involved with the development of the vanilla flavor.