Chemical and Nutritional Evaluation of Pumpkin (Cucurbita pepo) Seed Proteins

Chemical and nutritional properties of pumpkin (Curcubita pepo) seed proteins were studied. The seed was processed into defatted flour (CPF) which was further processed into Curcubita protein concentrate (CPC) and Curcubita protein isolate (CPI) by alkaline water/isoelectric precipitation. Chemical properties of the protein products were determined using standard methods of analysis. The amino acid profile was determined by an automated Technicon® liquid chromatography system. Protein digestibility was assessed in-vitro (IVPD) using trypsin-pepsin enzyme method while biological values were determined on the basis of their amino acid profile. Protein efficiency ratio (PER) was estimated according to a standard proposed regression equation. The seed proteins demonstrated high levels of crude protein (CPC=69.98% and CPI=74.15%), vitamin C (CPC=43.46 and CPI=52.36 mg/ml) and vitamin A (CPC=100.56 and CPI= 63.43 I.U/g) with low levels of thiamin and riboflavin. Both proteins showed low and similar (p>0.05) levels of sodium (0.14-0.18%), calcium (0.86-1.02%), magnesium (0.53-0.58%) and phosphorus (0.09-0.11%). Percentage ratios of essential to total amino acids obtained for CPC and CPI (44.24% and 45.50%, respectively) were greater than 36% which is considered adequate for an ideal protein. Protein biological values obtained for CPC and CPI respectively were: 95% and 53% (chemical score), 2.80 and 1.56 (PER} and 70.10% and 51.28% (essential amino acid index). CPC showed a better digestibility than CPI with IVPD value of 56.88%. Threonine and lysine were the most limiting amino acids in both protein products. All anti-nutrients evaluated were low and below allowable limits. In conclusion pumpkin seed proteins showed good biological values and could be used to improve the quality of other plant proteins or as a possible replacement for animal proteins in conventional foods.