en تخصصي Special Original article Original article <div style="text-align: justify;"><span style="font-size:14px;"><span style="font-family:Times New Roman;"><span style="line-height:115%"><b><span lang="EN-ID"><span style="line-height:115%">Background:</span></span></b><span lang="EN-ID"><span style="line-height:115%"> 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.</span></span></span><br> <span style="line-height:115%"><b><span lang="EN-ID"><span style="line-height:115%">Methods:</span></span></b><span lang="EN-ID"><span style="line-height:115%"> 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 (LAB) growth, pH, and titratable acidity. Crude protein and anti-nutritional factors were analysed at the beginning and end of the fermentation.</span></span></span><br> <span style="line-height:115%"><b><span lang="EN-ID"><span style="line-height:115%">Results: </span></span></b><span lang="EN-ID"><span style="line-height:115%">LAB 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.</span></span></span><br> <b><span lang="EN-ID"><span style="line-height:107%">Conclusion:</span></span></b><span lang="EN-ID"><span style="line-height:107%"> 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 LAB growth under vacuum conditions.</span></span><br> <br> <span style="line-height:normal"><b><span lang="EN-ID">DOI:</span></b><span lang="EN-ID"> 10.18502/jfqhc.12.4.20404</span></span></span></span></div> Tempeh, Soybeans, Fermentation, Vacuum, Bacteria, Anaerobic 263 270 http://jfqhc.ssu.ac.ir/browse.php?a_code=A-10-1865-1&slc_lang=en&sid=1 Z. Sabrinatami 0009-0002-5879-8177 No 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 No Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1, Bulaksumur, Yogyakarta 55281, Indonesia T. Utami No 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 mn_cahyanto@ugm.ac.id 0000-0002-1448-876X Yes Department of Food and Agricultural Product Technology, Faculty of Agricultural Technology, Universitas Gadjah Mada, Jl. Flora No. 1, Bulaksumur, Yogyakarta 55281, Indonesia