Influence of Turning and Environmental Contamination on the Dynamics of Populations of Lactic Acid and Acetic Acid Bacteria Involved in Spontaneous Cocoa Bean Heap Fermentation in Ghana

Abstract

The influence of turning and environmental contamination on six spontaneous cocoa bean heap fermentations performed in Ghana was studied through a multiphasic approach, encompassing both microbiological (culture-dependent and culture-independent techniques) and metabolite target analyses. A sensory analysis of chocolate made from the fermented, dried beans was performed as well. Only four clusters were found among the isolates of acetic acid bacteria (AAB) identified: Acetobacter pasteurianus, Acetobacter ghanensis, Acetobacter senegalensis, and a potential new Acetobacter lovaniensis-like species. Two main clusters were identified among the lactic acid bacteria (LAB) isolated, namely, Lactobacillus plantarum and Lactobacillus fermentum. No differences in biodiversity of LAB and AAB were seen for fermentations carried out at the farm and factory sites, indicating the cocoa pod surfaces and not the general environment as the main inoculum for spontaneous cocoa bean heap fermentation. Turning of the heaps enhanced aeration and increased the relative population size of AAB and the production of acetic acid. This in turn gave a more sour taste to chocolate made from these beans. Bitterness was reduced through losses of polyphenols and alkaloids upon fermentation and cocoa bean processing.Raw cocoa beans have an astringent, unpleasant flavor and have to be fermented, dried, and roasted to obtain the desired characteristic cocoa flavor (27,30,41,45). Fermentation is hence the first step in cocoa powder and chocolate production. It is carried out spontaneously in heaps, boxes, baskets, or trays in cocoa-producing countries in the equatorial zone, led by the Ivory Coast, Brazil, and Ghana (1, 27). During the last decade, knowledge about the spontaneous cocoa bean fermentation process has been increasing (2,5,26,33,34,37). The microbiota involved in natural cocoa bean fermentation reflects the environmental factors (temperature, pH, and oxygen tension) and the metabolism of substrates of the cocoa bean pulp. This results in production times of significant amounts of ethanol, lactic acid, and acetic acid, representing a succession of yeasts, lactic acid bacteria (LAB), and acetic acid bacteria (AAB) during the cocoa bean fermentation course (2, 5, 36-38).In the last 5 years, the microbiology and biochemistry of Ghanaian cocoa bean heap fermentation processes have been studied in detail (5,18,26,33,34). During early and mid-time spontaneous fermentation of freshly harvested pulp and cocoa beans, piled into a heap, yeasts produce ethanol under anaerobic conditions and cause depectinization of the pulp, enabling the pulp to flow away and air ingress (37, 38). Concerning microaerophilic LAB, citrate-fermenting, acid-tolerant, and ethanol-tolerant Lactobacillus plantarum and Lactobacillus fermentum strains dominate the spontaneous cocoa bean fermentation process (5, 34). Citrate and sugars are converted into acetic acid, lactic acid, and mannitol, enabling a slight increase of the pH of the pulp (5). During the aerobic phase, ...

The impact of yeast starter cultures on the microbial communities and volatile compounds in cocoa fermentation and the resulting sensory attributes of chocolate

“…The closest relatives of the sequenced fragments were determined via GenBank searches for sequences with over 98 % similarity: A = S. cerevisiae; B = P. kluyveri; C = Candida sp. ; D = H. guilliermondii; E = H. uvarum; F = Theobroma cacao fermented grains, and, consequently, the final product (Camu et al 2008). According to previous research, yeasts are essential for the development of chocolate flavor and their inoculation may accelerate and control the fermentation process (Batista et al 2015;Ho et al 2014;Ramos et al 2014).…”

Antimicrobial activity of fermented Theobroma cacao pod husk extract

“…Processing of cocoa on the farms begins with the opening of the fruit (pods) in the field under the trees, where the seeds are separated from the husks. The seeds are then fermented in wooden boxes and sun-dried, to be later processed in the factory (Forsyth and Quesnel, 1957;Kalvatchev et al, 1998;Camu et al, 2008).…”

Cocoa Fermentation from Agnéby-Tiassa: Biochemical Study of Microflora

“…The presence of flora bacterial at the start of fermentation was similar to that observed in many countries [3,38]. According to some authors [2,39,40 which colonized cocoa fermenting mass come from the cocoa pod surface mainly, hands of workers, knives, unwashed baskets used for transport of seeds, and dried mucilage left on et al: Cocoa Fermentation from Agnéby-Tiassa: Biochemical Study of Microflora According to a report [2], observed during fermentation was associated to intense metabolic activity of process, reaching sometimes about 50°C at the end of the process. Overall, ed in cocoa fermentation provided an ecosystem that selected for the successional growth of various species of yeasts, lactic acid bacteria, acetic and pH during cocoa fermentation.…”