Comparison of Acid Fermentation under Vacuum and by Conventional Method in Tempeh Production: Microbial and Chemical Changes

Z. Sabrinatami; F.A. Purwandari; T. Utami; M.N.  Cahyanto

doi:10.18502/jfqhc.12.4.20404

Z. Sabrinatami Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1, Bulaksumur, Yogyakarta 55281, Indonesia
F.A. Purwandari Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1, Bulaksumur, Yogyakarta 55281, Indonesia
T. Utami Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1, Bulaksumur, Yogyakarta 55281, Indonesia
M.N. Cahyanto Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1, Bulaksumur, Yogyakarta 55281, Indonesia

DOI: https://doi.org/10.18502/jfqhc.12.4.20404

Keywords: Tempeh, Soybeans, Fermentation, Vacuum, Bacteria, Anaerobic

Abstract

Background: In conventional tempeh processing, water is required at most steps, including the acid fermentation by soaking. In this study, vacuum conditions during acid fermentation were employed instead of soaking soybeans to reduce the water requirement and wastewater generated. This study aimed to evaluate the microbial and chemical changes during acid fermentation under vacuum conditions.

Methods: Tempeh processing started by hydrating peeled soybeans with water, followed by incubation under vacuum at pressure101.3, 60.7, and 19.2 kPa. Samples were taken every 6 h to analyse lactic acid bacteria growth, pH, and titratable acidity. Crude protein and anti-nutritional factors were analysed at the beginning and end of the fermentation.

Results: Lactic acid bacteria grew and reached the stationary phase after 48 h compared 18 h in the conventional methods. The pH of soybeans decreased to below 6.0 after 24 h and 48 h of acid fermentation by the conventional and vacuum methods, respectively. Titratable acidity increased during acid fermentation. Protein, phytic acid, and tannin contents changed significantly during conventional acid fermentation; however these compounds did not change significantly during acid fermentation under vacuum.

Conclusion: Acid fermentation with vacuum methods showed potential for reducing anti-nutrients such as phytic acid and tannins in soybeans. Further optimization is required to improve Lactic Acid Bacteria (LAB) growth under vacuum conditions.