Partial substitution of whey protein concentrate by zein in high-protein nutrition bars: An effective method to reduce hardening during storage.

Whey protein concentrate-based high-protein nutrition bars (WPC-based HPN bars) are prone to hardening during storage, which limits their shelf life. In this study, zein was introduced to partially substitute WPC in the WPC-based HPN bars. The result of storage experiment revealed that the hardening of WPC-based HPN bars was significantly reduced with increasing zein content from 0% to 20% (mass ratio, zein:WPC-based HPN bar). Subsequently, the possible anti-hardening mechanism of zein substitution was studied in detail by determining the change in microstructure, patterns, free sulfhydryl group, color, free amino group, and Fourier transform infrared spectra of WPC-based HPN bars during storage. The results showed that zein substitution significantly blocked protein aggregation by inhibiting cross-linking, the Maillard reaction, and protein secondary structure transformation from α-helix to β-sheet, which reduced the hardening of WPC-based HPN bars. This work provides insight into the potential utilization of zein substitution to improve the quality and shelf life of WPC-based HPN bars. PRACTICAL APPLICATION: In the preparation of whey protein concentrate-based high-protein nutrition bars, the introduction of zein to partially replace WPC can effectively reduce the hardening of WPC-based HPN bars during storage by preventing protein aggregation between WPC macromolecules. Therefore, zein could act as an agent to reduce the hardening of WPC-based HPN bars.