Microencapsulation of red onion peel polyphenols fractions by freeze drying technicality and its application in cake

This work focuses on extraction of biological compounds from red onion peels and its microencapsulation using maltodextrin (MD), soybean protein isolate, and a complex of soybean protein isolate (SPI) and maltodextrin by freeze drying manner. Furthermore, there was a quality evaluation for cake integrated with microencapsulated polyphenols as well as polyphenols stability assessment after baking. Extracts of red onion peel were produced by three methanol concentrations (50, 75, or 100% v/v). A 75% methanolic red onion peel extract (75M) yielded a high total phenolic content, total flavonoid, and antioxidant activity using β‐carotene bleaching and 1,1‐diphenyl‐2‐picrylhydrazyl (DPPH) radical scavenging. (SPI + MD) encapsulates had higher encapsulation efficiency (94.30 ± 1.50%). Cake integrated with microcapsules had improved qualitative properties and increased polyphenol content more than other integrated with extract because of encapsulation protective effect pending baking. Comparatively, cake contained SPI microencapsulates showed higher specific volume, moisture absorption, texture, acceptable color, sensory evaluation, and concentration of polyphenols. PRACTICAL APPLICATIONS: Onion peels are one of the most important onions processing by‐products. The onion peel has a high biological compounds content such as quercetin, phenolics compound, and flavonols. As onion peels extract nature is extremely hygroscopic and sensitive for thermal, it is hard to add them to foodstuffs. The higher polyphenols content of encapsulating incorporated cake were enough to claim for the functionality of polyphenols in the cake. The higher polyphenols content of encapsulating incorporated cake were enough for claiming polyphenols functionality into the cake. (SPI + MD) microcapsules contained high concentrations of red onion peels polyphenols within freeze drying or baking process. Freeze drying is a sufficient technique for add polyphenols into the foodstuffs.