Improvement of cocoa fermentation quality using mixed starter cultures of Saccharomyces cerevisiae, Pichia kluyveri, and Lachancea thermotolerans

Abstract

Cocoa fermentation is an important post-harvest process that significantly affects the quality of cocoa beans and chocolate. Cocoa beans that have not undergone proper fermentation or incomplete fermentation result in undesirable flavors and aromas. This research studied and developed cocoa fermentation technology using a mixed- yeast starter culture. Three strains of aromatic, pectinolytic, and lactic acid- producing yeasts were isolated from spontaneous cocoa fermentation. They were identified as Saccharomyces cerevisiae (DOA-Y58), Pichia kluyveri (DOA-Y55), and Lachancea thermotolerans (DOA-Y81), respectively. In the cocoa fermentation trial, using a mixed culture starter ratio of DOA-Y58: DOA-Y55: DOAY82 at 1: 1: 1 ( % by weight) , it was found that cocoa beans were fully fermented, reaching approximately 84% within 144 hours. Additionally, it was possible to control the amount of natural bacteria that might cause undesirable flavors during fermentation. Analysis of volatile compounds of dried and roasted cocoa beans using headspace solid- phase microextraction ( HS- SPME) combined with gas chromatography-mass spectrometry (GC-MS) revealed that cocoa beans fermented with microbial starter cultures released fruity and floral aromas such as linalool, phenylethyl alcohol, and phenethyl acetate. Meanwhile, spontaneously fermented cocoa had a more acidic aroma. This demonstrates that using a mixed yeast starter culture of three strains plays a role in producing flavors and can be applied to improve cocoa fermentation quality.