Fabrication, characterization and controlled release properties of oat protein gels with percolating structure induced by cold gelation

• Cold-set oat protein isolate gels with percolating structure were fabricated.
• OPI monomers serve as building blocks and provide abundant cross-linking sites.
• The optimized gels showed high mechanical strength comparable to egg white.
• OPI gels can protect enzyme activity and probiotics viability in gastric condition.
• OPI gels have capacity to control release of vitamin in gastrointestinal condition.

Cold-set oat protein isolate (OPI) gels possessing a percolating network structure were successfully prepared using a glucono-δ-lactone (GDL) induced acidification method. The polymer-like percolating structures were established by active OPI monomers as small building block units through abundant cross-linking points. By increasing the GDL concentration, more intra-floc linkages and greater particle volume fractions were created at the supramolecular level, resulting in a dense rough gel wall with superior mechanical properties. In particular, at a 10% GDL content the gel was generated at the OPI isoelectric point (IEP). This OPI gel had a compact network structure with small pores and a thick wall, with an excellent water holding capacity (90%) and comparable mechanical strength (30 kPa) to egg white gel (22–32 kPa). Also, the cold-set OPI gels could resist acidic juice and pepsin digestion, which protected both α-amylase enzyme activity and the viability of probiotics in harsh gastric conditions. The in vitro release experiment demonstrated that OPI gels had the capacity to prevent the premature release of bioactive compounds in simulated gastric fluids, and yet still allowed their gradual release in a simulated intestinal environment where they normally would be absorbed. A convenient and non-toxic method to prepare OPI gels with superior performance has been described. These gels have the potential to act as delivery vehicles for sensitive compounds in food and non-food applications.

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