Extraction methods significantly impact physicochemical, amino acid, phytochemical and textural properties of pumpkin seed protein concentrate in Nigeria

Abstract

The increasing interest in sustainable plant-based proteins has driven research into underutilized seeds like pumpkin. This study investigated the colour, functional (bulk density, water and oil absorption capacities, and swelling power), amino acid, phytochemical, and textural properties of defatted pumpkin seed protein concentrate obtained using precipitation (PM), salt solubilization (SM), and aqueous alcohol wash (AM) methods. Analyses were conducted using standard methods. Results showed that protein concentrate varied significantly with the extraction method. AM produced the lightest isolate (L* = 58.25) with reduced redness and yellowness, while PM exhibited superior functional attributes: bulk density 0.69 g/mL, water absorption 2.84 g/g, oil absorption 2.00 g/g and swelling power 4.50 g/g. Amino acid profiling demonstrated that PM possessed higher levels of essential (leucine 7.03 g/100 g and lysine 6.00 g/100 g) and non-essential (glutamic acid 11.99 g/100 g) amino acids, accompanied by enhanced retention of flavonoids (5.15 mg/g), alkaloids (2.10 mg/g), saponins (3.50 mg/g), and tannins (2.85 mg/g), while textural analysis further revealed increased hardness (7.20 N), chewiness (40.10 N-mm), and resilience (0.50). Thus, precipitation extraction yielded protein concentrate with superior functional, textural, and nutritional qualities, highlighting its potential for use in fortified and functional foods.