Fermentation of Soybean Seeds Using Rhizopus oligosporus for Tempeh Production and Standardization Based on Isoflavones Content

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).

Fermentation of Soybean Seeds Using Rhizopus oligosporus for Tempeh Production and Standardization Based on Isoflavones Content

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 (a) condition caused the tempeh too hot and rotted quickly. Fermentation at (b) and (c) conditions produced tempeh with good quality. Tempeh ripening was reached between 32-32 hours with inner temperature 32-33oC. 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).

Isolation of Penicillium citrinum from Roots of Clerodendron cyrtophyllum and Application in Biosynthesis of Aglycone Isoflavones from Soybean Waste Fermentation

Soybeans offer an abundant source of isoflavones, which confer useful bioactivities when existing in aglycone forms. The conversion of isoflavones into aglycones via fermentation of soybean products is often realized by β-glucosidase, an enzyme produced by fungi. In this study, a filamentous fungus, Clerodendron cyrtophyllum, was isolated from root of Clerodendron cyrtophyllum Turcz, which was able to produce the highest activity of β-glucosidase up to 33.72 U/mL at 144 h during fermentation on Potato Dextrose Broth (PDB). The obtained fungus was grown on isoflavones-rich soybean extract to produce genistein and daidzein, achieving the conversion rate of 98.7%. Genistein and daidzein were isolated and purified by column chromatography using hexane/acetone (29:1/1:1), reaching purities of over 90% of total isoflavones, as identified and determined by TLC, LC-MS/MS, and 1H and 13C NMR spectroscopy. These results imply that the isolated P. citrinum is a potential fungal strain for industrial-scale production of genistein and daidzein from isoflavones-containing soybean extracts. These products may serve as potential raw materials for manufacture of functional foods that are based on aglycones.

Ultrasound- and hemicellulase-assisted extraction increase β-glucosidase activity, the content of isoflavone aglycones and antioxidant potential of soymilk

Soymilk is consumed as such or used in the preparation of tofu, fermented soymilk, and soy yogurt, among others. In this study, hemicellulase-assisted extraction (HAE) and ultrasound-assisted extraction (UAE) were used during soymilk manufacturing. The activity of endogenous β-glicosidases was increased 1.3 and 1.5-fold in soymilk produced upon HAE and UAE, respectively. Likewise, the concentration of isoflavones in the aglycone form increased 1.7 and 2.4 times in samples subjected to HAE and UAE, respectively. UAE, but not HAE, rendered an equimolar conversion from conjugated isoflavones to their respective aglycones. In addition, HAE and UAE showed higher antiradical activity towards ABTS radical cation and peroxyl radical, compared to those of the control. The aglycone isoflavones/conjugated isoflavones (aISO/cISO) ratio correlated with the antiradical activity, thus suggesting that the soybean industry may use this new quality index to indicate the antioxidant potential of products. Food formulations containing soymilk with high aISO/cISO ratio may translate to higher oxidative stability of the final product. Likewise, the higher absorption of aglycone isoflavones compared to that of their conjugated counterparts is well recognized. Therefore, high aISO/cISO ratio of soymilk and/or its products may provide a better antioxidant protection under physiological conditions.

Ultransound- and hemicellulase-assisted extraction increase β-glucosidase activity, the content of isoflavone aglycones and antioxidant potential of soymilk

Soymilk is consumed as such or used in the preparation of tofu, fermented soymilk, and soy yogurt, among others. In this study, hemicellulase-assisted extraction (HAE) and ultrasound-assisted extraction (UAE) were used during soymilk manufacturing. The activity of endogenous β-glicosidases was increased 1.3 and 1.5-fold in soymilk produced upon HAE and UAE, respectively. Likewise, the concentration of isoflavones in the aglycone form increased 1.7 and 2.4 times in samples subjected to HAE and UAE, respectively. UAE, but not HAE, rendered an equimolar conversion from conjugated isoflavones to their respective aglycones. In addition, HAE and UAE showed higher antiradical activity towards ABTS radical cation and peroxyl radical, compared to those of the control. The aglycone isoflavones/conjugated isoflavones (aISO/cISO) ratio correlated with the antiradical activity, thus suggesting that the soybean industry may use this new quality index to indicate the antioxidant potential of products. Food formulations containing soymilk with high aISO/cISO ratio may translate to higher oxidative stability of the final product. Likewise, the higher absorption of aglycone isoflavones compared to that of their conjugated counterparts is well recognized. Therefore, high aISO/cISO ratio of soymilk and/or its products may provide a better antioxidant protection under physiological conditions.