Tuning Chocolate Flavor through Development of Thermotolerant Saccharomyces cerevisiae Starter Cultures with Increased Acetate Ester Production

Abstract

Microbial starter cultures have extensively been used to enhance the consistency and efficiency of industrial fermentations. Despite the advantages of such controlled fermentations, the fermentation involved in the production of chocolate is still a spontaneous process that relies on the natural microbiota at cocoa farms. However, recent studies indicate that certain thermotolerant Saccharomyces cerevisiae cultures can be used as starter cultures for cocoa pulp fermentation. In this study, we investigate the potential of specifically developed starter cultures to modulate chocolate aroma. Specifically, we developed several new S. cerevisiae hybrids that combine thermotolerance and efficient cocoa pulp fermentation with a high production of volatile flavor-active esters. In addition, we investigated the potential of two strains of two non-Saccharomyces species that produce very large amounts of fruity esters (Pichia kluyveri and Cyberlindnera fabianii) to modulate chocolate aroma. Gas chromatography-mass spectrometry (GC-MS) analysis of the cocoa liquor revealed an increased concentration of various flavor-active esters and a decrease in spoilage-related off-flavors in batches inoculated with S. cerevisiae starter cultures and, to a lesser extent, in batches inoculated with P. kluyveri and Cyb. fabianii. Additionally, GC-MS analysis of chocolate samples revealed that while most shortchain esters evaporated during conching, longer and more-fat-soluble ethyl and acetate esters, such as ethyl octanoate, phenylethyl acetate, ethyl phenylacetate, ethyl decanoate, and ethyl dodecanoate, remained almost unaffected. Sensory analysis by an expert panel confirmed significant differences in the aromas of chocolates produced with different starter cultures. Together, these results show that the selection of different yeast cultures opens novel avenues for modulating chocolate flavor.

Genome Sequences of Cyberlindnera fabianii 65, Pichia kudriavzevii 129, and Saccharomyces cerevisiae 131 Isolated from Fermented Masau Fruits in Zimbabwe

“…All three species are found regularly in (fermented) food products (3, 5–14) but also occasionally in clinical sources (15–17). Nevertheless, P. kudriavzevii and S. cerevisiae were given the status of generally recognized as safe by the Food and Drug Administration (FDA) (18).…”

Diversity of Yeasts Involved in Cocoa Fermentation of Six Major Cocoa-Producing Regions in Ivory Coast

“…The high prevailing of these species could be due to ability of these species to withstand the stressful conditions from cocoa fermentation ( . Also, the dominance of these species is an interesting result because most studies, concerning the control of cocoa fermentation by yeasts, reported the use of these three species as appropriate starter cultures (Crafack, et al, 2013. Meersman, et al, 2016.…”

“…Concerning Saccharomyces cerevisiae, Meersman, et al (2016) showed that thermotolerant hybrid strains of Saccharomyces cerevisiae would be able to increase acetate ester production necessary to aroma formation of chocolate. Thus, Saccharomyces cerevisiae strains which prevail in all regions can be exploited in order to identify appropriate starters cultures to cocoa fermentation or others food fermentations.…”

“…In this context, the yeast species as Pichia kudriavzevii, Saccharomyces cerevisiae, Pichia klyuveri and Candida sp., were used as starter to control cocoa fermentation (Crafack, et al, 2013. Mahazar, et al, 2015. Meersman, et al, 2016.…”

PHENOS: a high-throughput and flexible tool for microorganism growth phenotyping on solid media

“…For example, Saccharomyces cerevisiae deletion mutant arrays were announced in 1999 [1] and made it possible to rapidly screen the whole yeast genome for synthetic lethal interactions in Synthetic Genetic Array (SGA) analyses [2, 3]. That same technique was soon expanded to other species like the fission yeast Schizosaccharomyces pombe [3], and the bacterium Escherichia coli [4], Other laboratories were also putting gene expression libraries into E. coli or in S. cerevisiae arrays for high-throughput screening [6, 7],…”