Tempeh is an Indonesian traditional food, made from white soybean seeds by fermentation with Rhizopus mold. Soybean seeds content high isoflavone glycosides. Isoflavones can act as phytoestrogen, antioxidant and improves memory. Isoflavone glycosides are poorly absorbed in the human body, but the aglycone isoflavones absorbed quickly. Rhizopus mold hydrolize isoflavone glycosides to be aglycone isoflavones during tempeh production. This research was aimed to know the best room temperature and time of fermentation for making soybean tempeh with high content of isoflavones. After rinsing and boiling, the soybean seeds than fermented with Rhizopus oligosporus. Three conditions were applied: (a) ambient temperature (27-32oC) without air circulation, (b) 27±0.5 oC, and (c) 30±0.5 oC both with air circulations. Inner temperature of tempeh was recorded hourly. Total isoflavones were measured with UV spectrophotometer every 6 hours. Based on this study, fermentation at condition a caused the tempeh too hot and rotted quickly. Fermentation at condition b and c produced tempeh with good quality. Tempeh ripening was reached between 31-32 hours with inner temperature 32-33 ^oC. Fermentation for 72 hours at condition b was chosen because its high total isoflavones content (0.089% w/w), but decrease about 20% compare to soybean seeds (0.112% w/w).

The lack of adequate knowledge of the culinary and sensory properties of most indigenous and wild foods hampers their promotion in human diets and the market. In the present study, 80 Burkinabe volunteers evaluated the sensory appeal and attributes of three selected Senegalia seed species (Zamnè, pseudoZamnè or Kumatiya, and S. erythrocalyx) and their food formulas (traditionally cooked, harvested as green and fresh legumes, and fermented as tempeh) using the 9-point hedonic scale and check-all-that-apply questionnaire. They found that the traditionally cooked Zamnè, pseudoZamnè or Kumatiya, and derived tempeh had good sensory appeal (scoring between 5-7) and subtle alkaline and nutty tastes, which will facilitate their blending in cuisines. Yet, an appreciable number (32%) of the participants, as unaccustomed to tempeh, scored all the tempeh products very low (2.5-3.4), suggesting food neophobia. In contrast, the traditionally cooked seeds of Senegalia erythrocalyx and the green and fresh Zamnè evoked bitter and sour off-tastes, respectively, and were not much appreciated (scoring 4). The present study provides unprecedented insight into consumers’ non-sensory perceptions and the culinary and sensory properties of Senegalia seed foods – which will be essential for their valorization, branding, and marketing.

The increased consumption of high fat-containing foods has been linked to the prevalence of obesity and abnormal metabolic syndromes. Rhizopus oligosporus, a fungus in the family Mucoraceae, is widely used as a starter for homemade tempeh. Although R. oligosporus can prevent the growth of other microorganisms, it grows well with lactic acid bacteria (LAB). Lactobacillus plantarum can produce β-glucosidase, which catalyzes the hydrolysis of glucoside isoflavones into aglycones (with greater bioavailability). Therefore, the development of a soybean-based functional food by the co-inoculation of R. oligosporus and L. plantarum is a promising approach to increase the bioactivity of tempeh. In this study, the ameliorative effect of L. plantarum in soy tempeh on abnormal carbohydrate metabolism in high-fat diet (HFD)-induced hyperglycemic rats was evaluated. The co-incubation of L. plantarum with R. oligosporus during soy tempeh fermentation reduced the homeostatic model assessment of insulin resistance, HbA1c, serum glucose, total cholesterol, triglyceride, free fatty acid, insulin, and low-density lipoprotein contents and significantly increased the high-density lipoprotein content in HFD rats. It also increased the LAB counts as well as the bile acid, cholesterol, triglyceride, and short-chain fatty acid contents in the feces of HFD rats. Our results suggested that the modulation of serum glucose and lipid levels by LAB occurs via alterations in the internal microbiota, leading to the inhibition of cholesterol synthesis and promotion of lipolysis. Tempeh, produced with both L. plantarum and R. oligosporus, may be a beneficial dietary supplement for individuals with abnormal carbohydrate metabolism.