Assessment of the impact of enzymatic hydrolysis temperature and time on recovery yield, anthocyanin content, and sensory quality of sterilized purple rice milk

Purple brown rice is a highly nutritious food source, rich in bioactive compounds, particularly anthocyanins - powerful antioxidants that play a crucial role in health protection. The production of sterilized purple rice milk in glass bottles not only provides a convenient, safe product with an extended shelf life but is also environmentally friendly. This study aimed to evaluate the effects of enzymatic hydrolysis temperature (75, 80, and 85℃) and time (5, 15, and 25 minutes) on the physicochemical properties of hydrolysates (soluble solids content, insoluble solids content, reducing sugar content, anthocyanin content, recovery yield, transmittance, and color values L, a*, b*, and Ho), as well as the sensory attributes of sterilized purple rice milk. The results showed that hydrolysis temperature had a significant impact on recovery yield, transmittance, and color values, whereas hydrolysis time clearly influenced soluble solids content, insoluble solids content, reducing sugars, and anthocyanin content. Under optimal conditions (80℃ for 15 minutes), the purple rice hydrolysate achieved a soluble solid content (7.27%), recovery yield (65.6%), reducing sugar content (29.2 mg/L), and anthocyanin content (11.8 mg/L). Furthermore, rice milk produced from this hydrolysate exhibited the highest sensory quality.