Abstract
The fermentation of cocoa pulp is one of the few remaining large-scale spontaneous microbial processes in today's food industry. The microbiota involved in cocoa pulp fermentations is complex and variable, which leads to inconsistent production efficiency and cocoa quality. Despite intensive research in the field, a detailed and comprehensive analysis of the microbiota is still lacking, especially for the expanding Asian production region. Here, we report a large-scale, comprehensive analysis of four spontaneous Malaysian cocoa pulp fermentations across two time points in the harvest season and two fermentation methods. Our results show that the cocoa microbiota consists of a “core” and a “variable” part. The bacterial populations show a remarkable consistency, with only two dominant species, Lactobacillus fermentum and Acetobacter pasteurianus. The fungal diversity is much larger, with four dominant species occurring in all fermentations (“core” yeasts), and a large number of yeasts that only occur in lower numbers and specific fermentations (“variable” yeasts). Despite this diversity, a clear pattern emerges, with early dominance of apiculate yeasts and late dominance of Saccharomyces cerevisiae. Our results provide new insights into the microbial diversity in Malaysian cocoa pulp fermentations and pave the way for the selection of starter cultures to increase efficiency and consistency.
Highlights
The curing of cocoa beans under influence of the cocoa pulp fermentation, the first step in the production of chocolate, is one of the few remaining large-scale spontaneous microbial processes in the food industry
Previous reports indicate that yeasts, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) are the key players of this fermentation process, during which the mucilaginous, sugary pulp that surrounds the beans is liquefied [1,2]
Two fermentations were performed in the beginning of the harvest season [box fermentation 1 (B1) and heap fermentation 1 (H1), October 2011], while the other two fermentations were executed at the end of the harvest season [box fermentation 2 (B2) and heap fermentation 2 (H2), January 2012]
Summary
The curing of cocoa beans under influence of the cocoa pulp fermentation, the first step in the production of chocolate, is one of the few remaining large-scale spontaneous microbial processes in the food industry. Previous reports indicate that yeasts, lactic acid bacteria (LAB) and acetic acid bacteria (AAB) are the key players of this fermentation process, during which the mucilaginous, sugary pulp that surrounds the beans is liquefied [1,2] Together, these microorganisms are responsible for the generation of ethanol, lactic acid, acetic acid and heat during the fermentation and for an increased air penetration as the fermentation proceeds [3,4]. These microorganisms are responsible for the generation of ethanol, lactic acid, acetic acid and heat during the fermentation and for an increased air penetration as the fermentation proceeds [3,4] Despite this general description of cocoa pulp fermentations, there is considerable variation between different fermentations, because the spontaneous nature of cocoa pulp fermentations leads to variations in the active microbiota. Since spontaneously fermented foodstuffs, such as specialized beers, wine and other beverages, still represent a significant part of the production market, the microbiota involved in these fermentations remains a topic of interest [5,6,7,8,9]
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