Culturas iniciadoras durante o processo fermentativo do cacau

Abstract

The development of resitant Theobroma cocoa hybrid towards Moniliophtora perniciosa mould changes the physiological characteristics of the fruits and consequently influencing the quality of the final product. The inoculation of microorganisms during cocoa fermentation process have been investigated as alternative to improve the quality of chocolate. This study aimed to investigate the effect of yeast inoculation during cocoa fermentation on the volatile compounds profile, chemical parameters (carbohydrates, ethanol and organic acids), concentration of purine alkaloids and sensory quality of chocolates. The eukaryotic microbial community during the spontaneous and inoculated fermentation of PS1319 hybrid was obtained by PCR-DGGE. Both fermentations showed similar profiles, detecting the dominant yeasts Hanseniaspora uvarum, Pichia kluyveri and Saccharomyces cerevisiae. The dynamic behavior of the yeast starter culture (Hanseniaspora uvarum, Pichia kluyveri and Saccharomyces cerevisiae) during the fermentation process was evaluated by qPCR analysis. The population of S. cerevisiae (7.9 log cell/g) and P.kluyveri (5.9 log cell/g) was higher in inoculated fermentation, while the H. uvarum (4.5 log cell/g) remained almost the same. Carbohydrates, ethanol and organic acids were measured from the pulp and beans during the cocoa fermentations. At 72 h, the concentration of carbohydrates was lower than 3 g/kg for both assays. In the inoculated fermentation, the minimum concentration of citric acid (1g/kg) was detected at 72 hours of fermentation, while in the spontaneous fermentation it was achieved at 48 hours of fermentation. The ethanol concentration was twice higher in inoculated fermentation, but did not affect the concentration of acetic acid, which showed similar concentrations (2,9g/Kg) in the both fermentations. The volatile compounds were detected and quantified by GC-FID at the beginning and end of fermentation process. A total of 33 volatile compounds were identified. The purine alkaloids were identified by chromatographic analysis. The relative proportion of theobromine and caffeine was 5.99 in the spontaneous fermentation and 3.82 in the inoculated fermentation. Chocolates were evaluated by acceptance test, check-all-that-apply (CATA) and temporal dominance of sensations (TDS). In the acceptance test, there was no significant (p<0.05) difference between inoculated or not inoculated samples. According to CATA test, chocolates showed the bitter attribute as dominant. While the TDS test related the chocolate produced by yeast inoculation to sweet, astringent and fruity attributes. The bitter and cocoa attributes were dominant throughout the analysis. The inoculation influenced the profile of volatile compounds and sensory attributes of chocolate, especially regarded to the bitter and fruity attributes.