PHENYLPROPANOID METABOLISM IN VANILLA-PLANIFOLIA ANDR .5. HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC ANALYSIS OF PHENOLIC GLYCOSIDES AND AGLYCONES IN DEVELOPING FRUITS

Reversed-phase high performance liquid chromatography (HPLC) has been used to study the formation of phenolic flavour compounds in developing fruits of Vanilla planifolia. Flowers of V. planifolia were hand pollinated and fruits were collected at 12 different times (4 to 28 weeks) after pollination at a vanilla plantation in Papantla, Veracruz, Mexico. HPLC-chromatograms of bean extracts were recorded at two wavelengths (254 and 275 nm) and the ratio between the absorbances of these chromatograms was used in combination with retention times to identify phenolics in the relatively complex extracts. Formation of vanillin, the major flavour compound, started around 16 weeks after pollination and reached maximum values around 26 weeks after pollination. Other phenolic vanilla flavour components detected were 4-hydroxybenzaldehyde, 4-hydroxybenzoic acid, vanillyl alcohol and vanillic acid. All these phenolics are stored in bean tissue mainly as glycosides.