Metabolite Transformation and Enzyme Activities of Hainan Vanilla Beans During Curing to Improve Flavor Formation

Abstract

This paper compares the differences in metabolites of vanilla beans at five different curing stages. Key vanilla flavors, vanillin precursors and main enzymes during the curing process of Hainan vanilla beans were also analyzed. Hundreds of metabolites were detected based on metabolic analyses of a widely targeted metabolome technique, compared with blanched vanilla beans (BVB), sweating vanilla beans (SVB) and drying vanilla beans (DVB), the total peak intensity of cured vanilla beans (CVB) is on the rise. The score plots of principal component analysis indicated that the metabolites were generally similar at the same curing stages, but for the different curing stages, they varied substantially. During processing, vanillin content increased while glucovanillin content decreased, and vanillic acid was present in sweating beans, but its content was reduced in drying beans. Both p-hydroxybenzaldehyde and p-hydroxybenzoic acid showed the maximum contents in cured beans. Ferulic acid was mainly produced in drying beans and reduced in cured beans. p-coumaric acid increased during the curing process. Vanillyl alcohol in drying beans (0.22%) may be formed by the hydrolysis of glucoside, whose conversion into vanillin may explain its decrease during the curing stage. β-Glucosidase enzymatic activity was not detected in blanched and sweating beans, but was observed after drying. Peroxidase activity decreased during curing by 94% in cured beans. Polyphenol oxidase activity was low in earlier stages, whereas cellulase activity in processed beans was higher than in green beans, except for cured beans. This study contributes to revealing the formation of flavor components and the biosynthesis pathway of vanillin.

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)

“…The reduction in the PPO activity could be related to the decrease in the water content and water activity with the progress of the curing cycles. In other works, it has been reported that after blanching at 70 • C/5 min, the beans retained less than 50% of the initial PPO activity of the untreated green beans, and after 36 sunny days they showed more than 80% of the initial PPO activity [1]. Discrepancies with this work could be attributed to the differences in the curing process and vanilla variety.…”

“…During the curing of flavorless green vanilla beans, a complex mixture of more than 200 components is produced, and the beans acquire a dark brown color. Among them, vanillin (4-hydroxy-3-methoxybenzaldehyde) is the main compound responsible for flavor [1]. The curing of vanilla beans is a long, traditional, and uncontrolled process that involves four stages: killing, sweating, sun drying, and conditioning [2].…”

“…Sweating and drying are performed simultaneously in multiple sweating-drying cycles until the beans reach a moisture content of approximately 20-30%. Vanilla killing is traditionally achieved by immersing green beans in hot water for a short time to stop the vegetative phase promoting physical and metabolic changes that release enzymes and substrate necessary for flavor development [1]. Thus, high enzymatic activities are desirable to promote the required biochemical reactions.…”

“…The effect of HHP on β-glucosidase activity [5], as well as the activity of PPO and POD [1], and vanillin concentration at different curing cycles [22] during the traditional curing process of vanilla beans have been investigated; however, to our knowledge, there is no information about PPO, POD activity, TPC, and color change during HHP-assisted curing. This work aimed to evaluate the effect of HHP, as a vanilla killing method, on the activity of PPO and POD, as well as on TPC and color evolution, during different curing cycles (sweating-drying) compared with blanched-treated beans.…”

Vanilla cultivation in Mexico: Typology, characteristics, production, agroindustrial prospective and biotechnological innovations as a sustainability strategy

“…Esto es debido a la ausencia de diversidad genética que permita aumentar la probabilidad de supervivencia con la presencia de genes que respondan de manera favorable a situaciones de estrés que afecte a las plantas morfo-fisiológicamente, derivando en problemas como aborción floral y/o de frutos, cierre estomático, reducción de la tasa fotosintética, inhibición del crecimiento, reducción del área foliar, deshidratación severa, aumento en la susceptibilidad de patógenos y por último necrosis (Borbolla-Pérez et al, 2016). Existen opciones que permiten mejorar la cadena de suministro, por ejemplo, a través del fitomejoramiento (potenciado el aroma y sabor, tamaño y grosor de las vainas, así como la resistencia a Fusarium oxysporum) (Cai et al, 2019;Pérez-Silva et al, 2021;Serrano-Fuentes et al, 2022;Silva et al, 2022). A pesar de ser una opción que ofrece resultados prometedores en cuanto a producción, el problema radica en las condiciones adversas económicamente hablando de los pequeños productores de vainilla, ya que carecen de la infraestructura necesaria y de los fondos necesarios para el establecimiento de biofábricas.…”