Enzymatic Activity and Its Relationships with the Total Phenolic Content and Color Change in the High Hydrostatic Pressure-Assisted Curing of Vanilla Bean (Vanilla planifolia).

Diverse enzymatic reactions taking place after the killing of green vanilla beans are involved in the flavor and color development of the cured beans. The effects of high hydrostatic pressure (HHP) at 50-400 MPa/5 min and blanching as vanilla killing methods were evaluated on the total phenolic content (TPC), polyphenoloxidase (PPO), and peroxidase (POD) activity and the color change at different curing cycles of sweating-drying (C0-C20) of vanilla beans. The rate constants describing the above parameters during the curing cycles were also obtained. The TPC increased from C1 to C6 compared with the untreated green beans after which it started to decrease. The 400 MPa samples showed the highest rate of phenolic increase. Immediately after the killing (C0), the highest increase in PPO activity was observed at 50 MPa (46%), whereas for POD it was at 400 MPa (25%). Both enzymes showed the maximum activity at C1, after which the activity started to decrease. As expected, the L* color parameter decreased during the entire curing for all treatments. An inverse relationship between the rate of TPC decrease and enzymatic activity loss was found, but the relationship with L* was unclear. HHP appears to be an alternative vanilla killing method; nevertheless, more studies are needed to establish its clear advantages over blanching.

Metabolite transformation and ß-d-glucosidase activity during the high hydrostatic pressure assisted curing of vanilla beans (Vanilla planifolia) to improve phenolic compounds formation.

Current methods for vanilla bean curing are long and reduce the enzymatic activity necessary for flavor development. High hydrostatic pressure (HHP) at 50-600 MPa was used to improve phenolic compounds formation and ß-d-glucosidase activity in vanilla beans compared with scalded beans. Phenolics were analyzed by HPLC and ß-d-glucosidase activity by spectrophotometry. Vanillin was the main phenolic and it was formed by ß-d-glucovanillin hydrolysis and vanillyl alcohol oxidation. HHP improved vanillin content and influenced ß-d-glucosidase activity. At the beginning of the curing the highest increments of vanillin were produced at 400 MPa (up to 15%), while at the end, this was observed at 50 (138%) and 600 MPa (74%). Maximum increment of up to 400% in ß-d-glucosidase activity was observed from 100 to 300 MPa, which was attributed to tissue decompartmentalization, and conformational changes induced by pressure. HHP could be used during vanilla curing to improve vanillin content and ß-d-glucosidase activity.

Comparative metabolomics in vanilla pod and vanilla bean revealing the biosynthesis of vanillin during the curing process of vanilla.

High-performance liquid chromatography-mass spectrometry (LC-MS) was used for comprehensive metabolomic fingerprinting of vanilla fruits prepared from the curing process. In this study, the metabolic changes of vanilla pods and vanilla beans were characterized using MS-based metabolomics to elucidate the biosynthesis of vanillin. The vanilla pods were significantly different from vanilla beans. Seven pathways of vanillin biosynthesis were constructed, namely, glucovanillin, glucose, cresol, capsaicin, vanillyl alcohol, tyrosine, and phenylalanine pathways. Investigations demonstrated that glucose, cresol, capsaicin, and vanillyl alcohol pathway were detected in a wide range of distribution in microbial metabolism. Thus, microorganisms might have participated in vanillin biosynthesis during vanilla curing. Furthermore, the ion strength of glucovanillin was stable, which indicated that glucovanillin only participated in the vanillin biosynthesis during the curing of vanilla.