Encapsulation of adzuki bean vigna angularis hydrolysate by alginate-based beads

Abstract

The aims of this research were to study the effect of different cooking conditions on bioactive compounds and biological activities of cooked adzuki beans and cooking water. The different encapsulation methods to entrap adzuki beans hydrolysate were investigated. The release characteristics of different freeze-dried alginate particles were investigated after in vitro simulated gastrointestinal digestion. The results showed that all cooking conditions (60-min boiling, 10-min autoclaving and 60-min autoclaving) caused a significant reduction in crude protein, TCA-soluble peptides, free amino groups, total phenolic content (TPC) and total flavonoid content (TFC) in cooked adzuki beans (p ≤ 0.05). Meanwhile, cooking resulted in a significant increase in TCA-soluble peptides, free amino group content, TPC and TFC in cooking water. The different cooking conditions affected amino acid composition and phenolic compounds. The 10-min autoclaving was the appropriate condition as it could retain more amino acids and release more bound phenolics. The obtained cooked beans and its cooking water contained higher bioactive compounds and showing higher biological activity compared to other conditions. Thus, mixed cooked beans and its cooking water from 10-min autoclaving, substrate for protein hydrolysis, were hydrolyzed with 7% Flavouryzme at 50OC, pH 6.0 for 6 hours. The obtained beans hydrolysate was entrapped in alginate-based via different encapsulation techniques (calcium alginate beads and sodium alginate particles). Freeze-dried adzuki beans hydrolysate was prepared as the control. The sodium alginate particles had a higher encapsulation efficiency of TPC and TCA-soluble peptides compared to calcium alginate beads. Fourier-transform infrared result confirmed the interaction of functional groups between adzuki beans hydrolysate and alginate structure. A remarkable increase in FRAP, ferrous chelating, ORAC value and ACE-I inhibitory after in vitro GI tract digestion were observed in the particles. Whilst beads exhibited higher ABTS scavenging activity after in vitro GI tract digestion compared to particles. DPP-IV inhibitory activity of particles and beads were not significantly different. This might be because encapsulation technique had a significant effect on the entrapped bioactive compounds and controlled-release characteristic of sample.