Characteristics of lactic acid bacteria and acetic acid bacteria isolated before and after fermentation of cacao beans from Pidie, Indonesia and detection of the flavour compounds

Abstract

The objectives of this research were to characterise lactic acid bacteria (LAB) and acetic acid bacteria (AAB) which were isolated before and after fermentation of cacao beans, and to detect the flavor compounds in each of these steps. Samples were collected from a farmer in the Pidie District, Aceh Province, Indonesia who supplies the fermented cacao beans for a local chocolate factory located in Pidie Jaya District. The samples were collected before fermentation (F0) and after 5 days fermentation (F5) steps in duplicate. Five LAB and nine AAB were characterised for colony and cell morphology, catalase and oxidase tests, and growth resistance at low pH. The qualitative analysis of flavor compounds of the cacao beans were identified by Gas Chromatography Mass Spectrometry Solid Phase Microextraction (SPME-GCMS). The results showed that all isolates have a negative result on oxidase tests and only one AAB isolate could grow at pH 3. The reduction of phenethylamine during fermentation is desired because it gives off a fishy odor as a result of decarboxylation of amino acids by lactic acid bacteria. The detection of 3-octanyl acetate by its sweet floral fruity odor is expected. It is also interesting to note that a nutty taste and earthy aroma were detected indicating that trimethyl pyrazine and dimethyl pyrazine were present after fermentation even though they were not a major compound.