The in vitro digestibility of SPP improved significantly (P < 0.05) by boiling, microwave boiling, drying and autoclaving, among which autoclaving was the most effective method (Table 3). After autoclave treatment, the in vitro digestibility of SPP increased from
52.8% to 99.2%, to give approximately the same digestibility value as obtainable with SPI and WPI. Autoclaving was also the best way to improve the in vitro digestibility of commercial SPI, increasing its digestibility by 7.8%. Drying significantly (P < 0.05) increased SPP in vitro digestibility, but reduced that of commercial SPI by 5.2% and had no effect on WPI. For the boiling process, the in vitro digestibility of SPP increased with increasing heating time. Whereas boiling at 100 8C for 20 min increased the in vitro
digestibility of SPP by 46.1% compared with that of native SPP, boiling same for 1 h further increased in vitro digestibility to 62.2%. On the overall, the effects of heat processing on the in vitro digestibility of SPP were in the order:
autoclaving > microwave boiling > boiling > drying.