Effect of Fermentation by Rhizopus oligosporus or Amylomyces rouxii on In-Vitro Starch and Protein Digestibility of Decorticated Red Sorghum (Sorghum bicolor L. Moench)

Solid substrate fermentation of cooked decorticated red sorghum was carried out by using mould Rhizopus oligosporus or Amylomyces rouxii. This study aims to investigate the growth of mould biomass by determining glucosamine and investigating the effects of fermentation on the changes in proximate composition, pH and total titratable acidity, and in-vitro starch and protein digestibility. Red sorghum was decorticated using a carborundrum discs to remove the bran. Decorticated sorghum was soaked in water (12 h for R. oligosporus and 1 h for A. rouxii fermentation), heated up to 90oC for 30 min, steamed for 30 min, and sterilized at 121oC for 20 min). Fifty g of sterile sorghum was inoculated with R. oligosporus (6.103 spore/g substrate) or A. rouxii spores (2.103spore/g substrate) then incubated at 30oC. Samples were taken at 0, 12, 18, 24, 30, and 36 h for R. oligosporus fermentation and 0, 24, 48, 72, 120, and 168 h for A. rouxii fermentation. The results indicated that glucosamine content of fermented sorghum by R. oligosporus and A. rouxii were 4.49 and 11.72 mg/g dry matter at the end of fermentation, respectively. R. oligosporus hydrolyzed up to 11.4 of initial starch and 63.4 by. A. rouxii. There were more protein and fat losses in R. oligosporus fermentation than A. rouxii. Both fermentations produced acid and lowered pH to about 3.0, but pH went up to 4.0 at the end of R. oligosporus fermentation. Mould fermentation improved in-vitro starch digestibility, in A. rouxii it went up from 31.3 to 37.9 and down again to 11.4 at the end of fermentation. In R. oligosporus fermentation, it went up to 35.4. In-vitro protein digestibility went up from about 35.0 to 37.0 and to 51.8 by R. oligosporus and A. rouxii fermentation, respectively. © 2020. All Rights Reserved.