Effect of different heating pretreatment methods on physicochemical properties of pressed walnut oils and functional properties of walnut protein isolates

This study applied three heating pretreatment methods, including far infrared heating (FIH), stir-frying heating (SFH), and microwave radiation heating (MRH), to raw materials before the cold-press extraction of walnut oil (WO). The quality characteristics of WO and walnut protein isolate (WPI) were systematically studied. The results showed that different pretreatment methods significantly affected the physicochemical properties, oxidative stability, and antioxidant activity of WO ( p < 0.05). FIH pretreatment notably improved the yield, antioxidant activity, oxidation stability, and total polyphenol content of WO ( p < 0.05). Significant changes were also observed in the flavor profile of WO across the different pretreatment methods. Additionally, the WPI obtained after FIH pretreatment exhibited higher protein solubility (49.28%), water-holding capacity (4.58 g/g), and emulsion stability (94.63 min). These findings indicate that FIH pretreatment is a simple and effective strategy for producing high-quality WO and WPI. The findings provide technical support for enhancing the quality of WO and WPI in the food industry, while offering a theoretical foundation for the comprehensive utilization and value-added processing of walnut resources. • Three heating pretreatment methods (FIH, SFH, MRH) were applied to raw materials before WO extraction. • All heating pretreatment methods improved the physicochemical properties of WO and functional properties WPI. • The highest oil yield (63.48%), antioxidant activity, oxidation stability (2.79 h), and total polyphenol content (68.54 μmol TE/kg) were observed after FIH treatment. • The WPI obtained after FIH pretreatment exhibited the highest protein solubility (49.28%), water-holding capacity (4.58 g/g), and emulsion stability (94.63 min).