Pine nuts ( Pinus pinea L.) as a potential novel plant‐based source of functional protein isolates: Optimization of alkali extraction conditions, evaluation of functional properties, and biochemical characterization

Abstract

This study was undertaken with the main objective to investigate the influence of alkali extraction conditions; pH (8–10), time (60–120 min) and solvent-to-sample ratio (1:10–1:30 g/ml) on the purity of Pinus pinea L. nuts protein isolates and their functionalities (solubility and emulsifying activity) using response surface methodology (RSM). The optimal extraction conditions determined for maximum purity, solubility, and emulsifying activity were pH 8, time 108 min, and solvent-to-sample ratio 1:10 g/ml. In-depth investigations were conducted in terms of the functionality of the optimized P. pinea L. protein isolate (OPPPI), its composition, and secondary structure. FTIR spectroscopy and SDS–PAGE analyses revealed β-sheet to be the main secondary structure of OPPPI while 11S globulin, 7S globulin, and 2S albumin were its major components. In addition, OPPPI exhibited appreciable functional properties. Results suggest that pine nuts are a promising source of functional proteins potentially applied in various food applications as food ingredients. Novelty impact statement The global demand for new protein sources is growing exponentially. Pinus pinea L. nuts are a rich source of under-exploited proteins; their protein content of 65.368% when defatted makes them an attractive source for the production of functional protein ingredients. Using response surface methodology, alkaline extraction conditions were optimized, resulting in protein isolates with high purity and appreciable functional properties, further highlighting their potential introduction into the food industry as novel food ingredients.