Role of Bacteria in Tempe Bitter Taste Formation: Microbiological and Molecular Biological Analysis Based on 16S rRNA Gene

Abstract

Tempe is traditional Indonesian food. It has a variety of tastes, sometimes with a hint of bitterness, which may differ in intensity. The cause of bitterness in tempe has never been reported previously. In this study, the aim is to identify whether bacteria play a role in the formation of bitter tastes in tempe. Sensory tests were carried out in order to determine the scores of bitter-taste-intensity in tempe. The sensory test on EMP, WJB, CLR, DRG, and MLB tempe shows that EMP tempe has the highest score (2.3) and WJB has the lowest (1.3). It is revealed that the processing method has no impact on the formation of the bitter taste in tempe. Plating analysis, showed that EMP soaking water contained a higher number of Enterobacteria group bacteria, approximately 10 3-10 4 CFU ml-1 and spore-forming bacteria groups, 10 2 CFU ml-1 , compared to WJB. Similarly, other bacteria groups in fresh EMP tempe was 10 2 CFU g-1 higher than those in fresh WJB tempe. Based on sequencing the16S rRNA gene, the dominant bacteria on PCA media in EMP tempe are Acetobacter indonesiensis, Klebsiella pneumoniae, Bacillus subtilis, and Flavobacterium sp. On the other hand those in WJB tempe were Klebsiella sp., Brevundimonas sp., Bacillus sp., Pseudomonas putida, and Acinetobacter sp. Bacillus, a group of proteolytic bacteria was found 10 5 CFU m-1 higher in the soaking water of EMP compared to WJB. Nevertheless, the types and numbers of fungi were not significantly different between tempe types. Accordingly, it is concluded that the difference in the number and the types of bacteria involved in the tempe production process leads to the difference in the bitter taste intensity in both EMP and WJB tempe.

Effect of Tempeh Supplementation on the Profiles of Human Intestinal Immune System and Gut Microbiota

“…were dominant bacteria found in EMP tempeh, while Klebsiella sp. and Pseudomonas putida were the dominant bacteria in WJB tempeh (Barus et al 2008). A study by Ayu et al (2014) showed that Klebsiella pneumoniae from Indonesian tempeh were genetically different from pathogenic isolates.…”

Klebsiella pneumoniae from Indonesian Tempeh were Genetically Different from that of Pathogenic Isolates

“…Other 12 contaminants such as Brevibacterium epidermidis and Micrococcus luteus known to play a role in the formation of antioxidants in tempeh (Klus and Barz 1995). Furthermore, bacteria in tempeh is also known as one of the factors that play a role in the formation of a bitter taste in tempeh (Barus et al 2008). A diverse array of lactid acid bacteria and yeasts also play important role in Indonesian tempeh production (Efriwati et al 2013).…”

“…The process of tempeh making in Indonesia is still using conventional methods with uncontrolled condition (Barus et al 2008). During the fermentation process, not only fungi involved but also bacteria play important roles in the formation of flavor and nutrition.…”

“…Bacterial growth during tempeh production begins in the process of soybean soaking. During the fermentation process, the producers inadvertently adding bacteria so that the bacteria eventually become an inseparable part of tempeh, and even has an important role in determining the quality of tempeh (Barus et al 2008;Seumahu et al 2013).…”

“…K. pneumoniae isolates from Tempeh. Tempeh EMP and WJB was produced in Bogor, West Java, Indonesia (Barus et al 2008). A 10 g of fresh tempeh was placed into 90 mL of sterile physiological salt 0.85% (w/v) NaCl and homogenized in orbitar shaker (Yih Der) at a speed of 24 x g for one min.…”