Fermentação de cacau: processo conduzido com leveduras selecionadas, diversidade microbiológica e perfil aromático

Abstract

Fermented and dried cocoa beans are the raw material for the production of one of the most consumed foods worldwide: chocolate. For the formation of the essential chemical compounds for the characteristic flavors and aromas of good quality chocolate, seed fermentation is the crucial stage, where such compounds will be formed, as a result of the microbial activity developed throughout the process. A very well-defined microbial succession involving yeasts, lactic and acetic bacteria makes the fermentation medium conducive to the numerous physical and chemical reactions inside the seed, which will be finalized in the subsequent drying and roasting steps. The State of Pará is the largest Brazilian cocoa producer and stands out as a reference in the production of fermented and dried cocoa beans of excellent quality in the national and international market. To understand the role that two yeast species previously isolated and identified in cocoa fermentation in the city of Tomé-Açu play during the process, this study aimed to evaluate the addition of Saccharomyces cerevisiae and Pichia kudriavzevii starter cultures in the microbiological properties physical and chemical over the process time. The cultures of both species were reactivated and after the inoculum production, it was added to the fermentations in loco, where they were evaluated for periods of 7 days, except for the fermentation that received a mixed inoculum (equal proportions of the two species), that lasted 6 days. Over the time of the fermentations, there was a rapid consumption of total reducing sugars, an increase in temperature, a reduction in the contents of phenolic compounds, acidity and an increase in pH in treatments that received inoculations with P. kudriavzevii, in addition to providing fermented and dried cocoa beans with higher amounts of catechin and epicatechin (antioxidant activity), methylxanthines (metabolic activity), low levels of acidity and putrefactive bioactive amines such as cadaverine and putrescine. The formation of phenylethylamine was also observed in these treatments with P. kudriavzevii, showing a microbial synergy with the microbiota naturally found in fermentations. Regarding the volatile compounds identified, the amount of ketones, aldehydes and esters was higher in fermented almonds with the addition of inocula of P. kudriavzevii, which shows the importance of this yeast species in the production of volatile compounds with fruity, floral and sweets flavors. All the findings in this research are strongly linked to the existing microbiota during the fermentation of cocoa. It was possible to identify species of lactic acid bacteria that were never isolated before in cocoa fermentations in the Amazon region, which can be one of the differentials for the production of good quality cocoa beans. It was concluded that the addition of microbial inocula provided good quality fermented and dried cocoa beans, reinforcing the need for more investments in research to help rural producers in the Amazon region to emerge in the competition of the chocolate market.