Insight into extruded soy protein isolate for improving hardening of high protein-nutrition bars during storage

Most high-protein nutrition bars (HPNBs) would harden during storage, seriously affecting the acceptability of consumers. In this work, soy protein isolate (SPI), extruded at 50, 75, 100, 125, and 150 ℃, was formulated for HPNBs to investigate whether extrusion protein could relieve hardening and improve quality characteristics of HPNBs during 45 days of storage at 37 ℃. HPNBs prepared with extruded SPI were notably softer. And they had higher sensory scores than HPNBs produced with unextruded SPI during storage (P < 0.05). But there were no significant differences in hardness and total color change with the increase of extrusion temperature after 45 days of storage (P > 0.05). According to the correlation analysis, HPNBs prepared by SPI extruded at 50 ℃ had the best physicochemical properties. This study provides an effective way to relieve the hardening of HPNBs during shelf life or even longer.