Design of glucono‐δ‐lactone‐induced pinto bean protein isolate/κ‐carrageenan mixed gels with various microstructures: fabrication, characterization, and release behavior

Abstract BACKGROUND Protein gels are used for different purposes, such as providing good texture, serving as fat replacers, and enhancing the nutritional and functional characteristics of foods. They can also deliver controlled release agents for sensitive drugs. The objective of this study was to investigate the impact of κ‐carrageenan (kcr) concentration (0, 1.5, 3, and 4.5 mg g−1) on the morphological and physicochemical properties and release behavior of glucono‐δ‐lactone (GDL)‐induced pinto bean protein aggregate (PBA) gels. RESULTS When κ‐carrageenan concentration increased from 0 to 1.5 and 3 mg.g−1, the firmness of the samples increased significantly, by 2.04 and 3.7 fold, respectively (P < 0.05). A compact and homogenous network with considerable strength and maximum water‐holding capacity (97.52 ± 1.17%) was obtained with the addition of 3 mg g−1 κ‐carrageenan to the gel system. Further increasing the κ‐carrageenan concentration to 4.5 mg g−1 produced a coarse gel structure with higher storage modulus (G′), firmness (6.30‐fold), thermal stability, and entrapment efficiency (85.6%). Depending on the κ‐carrageenan concentration, various microstructures from protein continuous phase to κ‐carrageenan continuous phase were observed. The release test indicated that 70.25% of the loaded curcumin was released in the simulated gastrointestinal tract for pure PBA gels. In contrast, for binary gels containing 4.5 mg g−1 κ‐carrageenan, curcumin was protected in the upper gastrointestinal tract, and 64.45% of loaded curcumin was delivered to the colon. CONCLUSION Our study showed that κ‐carrageenan/PBA gels had high entrapment efficiency and could protect curcumin in the upper gastrointestinal tract. The hydrogels are therefore very valuable for colon‐targeting delivery purposes. © 2022 Society of Chemical Industry.