In order to extend the shelf life of milk cake, a Pickering emulsion containing antimicrobial peptide MOp2 from Moringa oleifera seeds was applied as preservative to milk cake. In this experiment, the preservative effect of the Pickering emulsion on milk cake was determined by measuring peroxide value, texture properties, total viable count, coliform count, color difference and sensory attributes. The results showed that Escherichia coli was detected in the vacuum packaging group (control) after 28 days of storage, and the count of E. coli exceeded the safety limit after 35 days. The total viable count, peroxide value (POV), and color difference was significantly higher than those of the experimental group coated with the Pickering emulsion. The experimental group remained unspoiled for 42 days. Sensory quality remained stable during the first 35 days of storage, total viable count increased slowly, and E. coli was not detected in the experimental group. Significant differences in texture properties between the two groups were observed starting from the 21th day of storage. Sensory and physicochemical evaluation showed that compared with the control group, the Pickering emulsion prolonged the storage life of milk cake by one week, indicating its good preservative effect.

Spray-dried whey protein powders were produced from whey obtained as a by-product in the production of milk cake and milk fan as ethnic dairy products in Yunnan, and their main components and processing characteristics were analyzed. The results showed that the main components of whey protein powder obtained from the by-product of milk cake were protein 39.0%, fat 6.0%, moisture 4.1%, total ash 7.7%, acidity 23.2 °T, and pH 5.61, and the processing characteristics were 99.52% solubility, less than 3.2% precipitation at different temperatures, and emulsifying activity index (EAI) and emulsion stability index (ESI) both greater than 42.7% at different pH values. The main components in whey protein powder obtained from the by-product of milk fan were protein 72.0%, fat 19.8%, moisture 4.6%, total ash 8.1%, acidity 58.3 °T, and pH 5.20, and its processing characteristics were 98.70% solubility, less than 3.5% precipitation at different temperatures, and EAI and ESI both higher than 50% at different pH values. The sensory scores of yogurts with the two whey protein powders were 70.7 and 72.7 out of 100 points, respectively, indicating that both can be used as an ingredient in yogurt.