Optimization of Enzymatic Hydrolysis and Fermentation Processing for Set-Type Oat Yogurt with Favorable Acidity and Coagulated Texture

The key role of enzymatic hydrolysis and fermentation in the sensory quality of set yogurt made from whole oats was demonstrated. The optimal process was established by the orthogonal and response surface methodology based on the acidity, textural, and rheological properties. The results indicated that the enzymatic hydrolysis appropriately consisted of liquefaction with 12 U/mL α-amylase at 70 °C and pH 6.5 for 60 min, followed by saccharification with 400 U/mL α-1,4-glucan glucohydrolase at 60 °C and pH 4.5 for 60 min. The <i>Streptococcus thermophilus ST15</i> and <i>Lactobacillus bulgaricus 20249</i> strains were the most efficacious strains, with a 0.1% inoculation for the fermentation at 42 °C for 16 h. So, a soft semisolid oat yogurt formed with an 8% solid-liquid ratio, which exhibited an acidity of 73.17 °T, a cohesiveness ratio of 0.51, and a maximum apparent viscosity of 1902.67 Pa·s. The coagulated texture of the oat yogurt was closely associated with the exopolysaccharide (EPS) yield up to 304.99 mg/L. These findings supported the optimal processing of oat yogurt, especially its correlation with the high capacity of EPS production by strains. It is an innovative and feasible way to improve the properties of set-type oat yogurt, especially the utilization of the whole oat.