Comparative biochemical profile of protein-rich products obtained from industrial rapeseed meal

Protein-rich products, prepared from industrial rapeseed meal, have the potential for versatile applications in the food, feed, and nutraceutical industries. The aim of study was to characterize the biochemical composition of two protein-rich products obtained from industrially produced rapeseed meal. Protein isolate (PI) and acid soluble protein (ASP) were prepared by alkaline extraction (pH 12.0) followed by isoelectric precipitation (pH 4.5). Biochemical analyses revealed that PI contained a high protein amount (86.9%), while ASP had 28.8% protein and a relatively high level of non- protein compounds including ash (20.6%) and fiber (30.0%). Results showed that neither protein products contained glucosinolates. They were rich in microelements; the most abundant were Cu (64.3 mg kg^-1) and Fe (133 mg kg^-1) in PI and Mn (39.7 mg kg^-1) and Zn (84.2 mg kg^-1) in ASP. PI and ASP were also a good source of Se (1.1 mg kg^-1and 0.9 mg kg^-1, respectively). Lysine was the most abundant essential amino acid in PI with amino acid score of 100.7% followed by leucine (98.3%) and valine (95.8%). Both protein products were mainly composed of low molecular weight fractions (5 to 33 kDa), but in different ratio. The PI contained two fractions with molecular weights 53 and 235 kDa which were not found in ASP. In conclusion, PI and ASP exhibited different biochemical characteristics which make them suitable for different applications.