Study on the Process Optimization of Quinoa Black Medlar Yogurt and Its Antioxidant Activity

Using quinoa and black medlar as compound additives, the adhesion and sensory scores were used as indicators to investigate the effects of quinoa slurry, black medlar powder, xylitol and lactic acid bacteria inoculation on quinoa black medlar sugar free yogurt. For the influence of quality, orthogonal experiment was carried out on the basis of single factor experiments to optimize the yogurt craft formula, and conduct research on physiochemical indexes, microbiological indexes, lactic acid bacteria counts and antioxidant activities. Results showed that the optimal processing parameters were as follows: Guinoa slurry 25%, black medlar powder 1.0%, xylitol 8%, lactic acid bacteria inoculation 1.0%. The yogurt made under this process had rich aroma of quinoa and black medlar, a sensory score of 93.2 and an adhesion of −2.35 N. At the same time, the physiochemical and microbiological indexes, lactic acid bacteria counts met the corresponding national food safety standard for yogurt. The IC₅₀ of DPPH and hydroxyl radicals in quinoa black medlar yogurt were 6.1 and 8.9 mg/mL, respectively, and the scavenging abilities were higher than those of the control group (35.9 and 40.5 mg/mL). The scavenging ability of DPPH and hydroxyl radical increased in different degrees during storage.