Sample Preparation
The obtained shelled walnut kernel was thermally processed according to a previously described method [9]. The moist-heat processing method was as following: five hundred grams of shelled walnut kernel was steamed in boiled water for 15, 20 and 30 min (S15, S20 and S30) at a temperature of 95 ± 1.5 ºC, which were cooled to room temperature, frozen for 24 h at -18 ºC, and lyophilized for 48 h at -55 ºC. The dry heated processing method was as following: five hundred grams of shelled walnut kernel was roasted in an air fryer (HD9252, Philips, Qingdao, Shandong, China) at 95 ± 1.5 ºC for 15, 20 and 30 min (R15, R20 and R30). The raw was as the untreated sample. Total samples were 7 (1 untreated + three moisture heated + three dry heated). The defatted walnut kernel flour (100 mesh screen) by ground processing contained about protein 44.85%±1.21%, oil 15.65%±1.08%, moisture content 5.32±0.53% and ash 3.09±0.51%.