Microbiological quality of tempeh with different wraps: banana leaf versus plastic.

Tempeh is a traditional Indonesian fermented food widely consumed and became staple food in some Indonesian diet. Commercially, tempeh is available in banana leaf or plastic wraps. The wraps are not only important for fermentation and giving final form of tempeh,  but also potential source of food microbiome. This study aimed to investigate the effect of different packaging materials on the lactic acid bacteria (LAB) quantity and community composition of tempeh from three manufacturers with different production environments. Each tempeh wrapped with banana leaf or plastic during the fermentation process and then LAB from every tempeh sample were quantified using qPCR and plate count method. Terminal Restriction Fragment Length Polymorphism analysis was carried out to assign bacterial community composition from these samples. The LAB population quantity of fresh tempeh from three manufacturers were essentially similar around 10 log CFU/g. However, there is a difference in the proportion of cultured and uncultured bacteria. Principal Coordinate Analyses based on Bray-Curtis similarity matrices showed an apparent clustering pattern for tempeh samples according to tempeh manufacturers. Meanwhile, packaging materials did not significantly influence changes in  bacterial community composition. The result of this work could be used for determination, authentication, and improvement of tempeh quality.

Dominant Enterobacteriaceae in tempeh were primarily originated from soybean.

During tempeh production, boiling was considered as heat treatment that could significantly reduce or eliminate bacterial population in soybean before fungal inoculation. The objective of this study was to enumerate and trace Enterobacteriaceae communities in pre-boiling soybean, post-boiling soybean, and fresh tempeh designated as RTI and EMP. Standard plate count and qRT-PCR were employed to determine the culturable and non-culturable bacteria, while Enterobacterial Repetitive Intragenic Consensus PCR was conducted to determine the intraspecies genomic variations. Fresh tempeh from both RTI and EMP contained approximately 107 and 108 CFU/g of Enterobacteriaceae respectively. The number of bacteria in pre-boiling soybean were 10,000 times lower than in fresh tempeh. Our study showed that most Enterobacteriaceae were severely injured or quiescent during boiling process and quickly recovered up to 109 CFU/g in fresh tempeh. Some Klebsiella isolates found in tempeh were genetically identical to isolates in soybean, but different from those of medical isolates. This study suggested that soybean could be the main origin of Klebsiella in fresh tempeh.