Raw walnut kernel: A natural source for dietary proteases and bioactive proteins.

Area of Science:

• Food Science
• Biochemistry
• Nutritional Science

Background:

• Walnut kernels are recognized for health benefits, primarily from polyunsaturated fatty acids, phenolics, and phytosterols.
• Limited information exists regarding the specific health benefits and functional properties of walnut proteins.

Purpose of the Study:

• To identify and characterize endogenous proteases in walnut kernels.
• To investigate the role of these proteases in walnut protein digestion.
• To assess the impact of processing methods (soaking, peeling) on walnut protein digestibility.

Main Methods:

• Liquid chromatography tandem mass spectrometry (LC-MS/MS) for protease identification and quantification.
• Enzyme activity assays across a range of pH and temperatures.
• In vitro protein digestibility assays before and after walnut processing.

Main Results:

• Identified six types of proteases, including endopeptidases, aminopeptidases, carboxypeptidases, superoxide dismutases, catalases, and phospholipases.
• Detected optimal protease activity at pH 4.5 and 50°C within a pH range of 2-6.5.
• Demonstrated that soaking and peeling significantly improved in vitro digestibility of walnut proteins.

Conclusions:

• Walnut kernels possess endogenous proteases that contribute to protein digestion.
• Processing methods like soaking and peeling are crucial for enhancing the bioavailability of walnut proteins.