Chemical, antioxidant, functional and thermal properties of rice bran proteins after yeast and natural fermentations

Abstract

Summary The paper focuses on the chemical, antioxidant, functional and thermal properties of rice bran proteins after yeast, natural fermentations and unfermented rice bran. Protein content of yeast‐fermented rice bran protein concentrate (YFRBPC), naturally fermented rice bran protein concentrate (NFRBPC) and unfermented rice protein concentrate (UFRBPC) were 72.50%, 68.92% and 65.73%, respectively, while ash content were 4.72%, 4.61% and 3.04%, respectively. The total amino acids of YFRBPC, NFRBPC and UFRBPC were 123.16, 118.45 and 99.39, respectively. DPPH radical inhibition of YFRBPC, NFRBPC and UFRBPC were 58.62%, 55.29% and 47.14%, respectively, while ferric reducing ability power were 0.73, 0.58 and 0.41 mmol TE per gram, respectively. The highest foam capacity of UFRBPC (57.56%), NFRBPC (64.15%) and YFRBPC (76.00%) was observed at pH 9.0. YFRBPC and NFRBPC were lighter in colour than UFRBPC. YFRBPC had higher denaturation temperature and enthalpy value than NFRBPC and UFRBPC. The β‐sheets structures were more in YFRBPC and NFRBPC than UNFBPC.

Effect of addition of protein concentrates from natural and yeast fermented rice bran on the rheological and technological properties of wheat bread

“…() reported that lower peak viscosity, breakdown, final viscosity and setback values are due to reduction in carbohydrate and variations in protein content. On the other hand, higher RVA values of composite blends containing YFRBPC compared with blends containing NFRBPC could be attributed to high water absorption capacity of YFRBPC than NFRBPC (Chinma et al ., in press). This observation is in line with those of Goel et al .…”

“…On the other hand, the reduction in crust colour scores of composite bread samples could be attributed to thermal nonenzymatic caramelisation and Maillard reactions between reducing sugars and amino acids due to increased protein and lysine contents in composite bread than control bread considering higher protein and lysine contents of NFRBPC and YFRBPC as reported by Chinma et al . (in press). However, darker colours of the crust were pronounced in wheat bread substituted with YFRBPC as revealed by their low scores compared with control and composite bread containing NFRBPC.…”

“…However, darker colours of the crust were pronounced in wheat bread substituted with YFRBPC as revealed by their low scores compared with control and composite bread containing NFRBPC. This could be attributed to higher amino acid content of YFRBPC compared with NFRBPC (Chinma et al ., in press). The crumb and crust texture were more firm and dense and increased slightly with increasing level of NFRBPC and YFRBPC.…”

“…Natural fermented rice bran protein concentrate (NFRBPC) and yeast fermented rice bran protein concentrate (YFRBPC) contains 68.92% and 72.50% protein content, respectively; while the essential amino acids, lysine, threonine and valine were 6.03, 3.78 and 5.59 g/100 g protein, respectively, for NFRBPC; and 6.89, 3.95 and 5.87 g/100 g protein, respectively, for YFRBPC (Chinma et al ., in press). The addition of protein concentrates from fermented rice bran to wheat flour in bread making may complement the protein content and amino acid profile (especially lysine) of wheat flour (11.4% protein with lysine content of 2.4 g/100 g lysine) (Hoseney & Rogers, ).…”

“…The addition of protein concentrates from fermented rice bran to wheat flour in bread making may complement the protein content and amino acid profile (especially lysine) of wheat flour (11.4% protein with lysine content of 2.4 g/100 g lysine) (Hoseney & Rogers, ). Also, higher antioxidant activity, water and oil absorption capacities, lighter colour and higher denaturation temperature of NFRBPC and YFRBPC suggest their potentials as functional ingredients in baked products such as wheat bread (Chinma et al ., in press).…”