Production of oat-based synbiotic beverage by two-stage fermentation with Rhizopus oryzae and Lactobacillus acidophilus

Many studies have reported that oats could effectively reduce the serum cholesterol levels in humans, and the ß-glucan in oat is believed to be responsible for this physiologic effect. Probiotics are live microorganisms that can confer a healthy benefit on the host when administered in adequate amounts. There is an increasing use of these microorganisms in food, aiming to balance intestinal microflora and alleviate dysfunction of the human gastrointestinal tract. However, a number of studies have shown that only 10-30% of these probiotic bacteria could survive after passing through the gastrointestinal (GI) tract. Lactobacillus acidophilus is used as a probiotic bacterium in many probiotic foods. However, L. acidophilus shows poor growth in cereal products due to its poor hydrolytic ability of protein and macromolecule carbohydrates. The aim of the present study was to combine Rhizopus oryzae-fermented oat mash and Lactobacillus acidophilus in an oat-based synbiotic beverage. Several factors, including starter culture concentration, R. oryzae-fermented oat mash and skim milk powder, were investigated. The nutritional contents in R. oryzae-fermented oat flour were just sufficient for survival but not growth of L. acidophilus. Adding sucrose (1% or 2%, w/v) did not improve the proliferation of L. acidophilus; however, L. acidophilus grew quickly when skim milk powder (1% or 2%, w/v) was added. When 5.5% R. oryzae-fermented oat mash with 2% added skim milk powder was used, the viable cell counts reached about 9.0 log cfu/ml at the end of 10 h fermentation. The concentration of ß-glucans (about 781 mg/l) was not significantly lowered during fermentation