ANTIOXIDANT ACTIVITY OF SOY PROTEIN HYDROLYSATE AND PEPTIDES

摘要

Oxidation of proteins and lipids in biological systems is harmful and is reported to be linked to several diseases such as atherosclerosis, inflammation, and cancer (1). In food, lipid oxidation produces rancid flavours and toxic undesirable compounds, leading to quality deterioration and shortened shelf life. The problem of lipid oxidation in food products may be exacerbated with the increased use of polyunsaturated fats for health benefits. Polyunsaturated fatty acids such as fish oil and sunflower oil have numerous double bonds that are prone to oxidation. In the presence of oxygen, light and metal ions, hydrogen is abstracted from the lipid resulting in free radicals. These primary lipid oxidation products produce secondary oxidation products like malonaldehyde and tertiary products including hexanal. Lipid free radicals also attack proteins resulting in protein free radicals that react further with amino acids or lipids (2). Aldehydes can also attack proteins resulting in protein cross-linking and toxic products (3). The oxidation of lipids and proteins can be retarded by antioxidants both in vivo and in vitro. Synthetic antioxidants are commonly used in food processing but have come under scrutiny recently due to their potential health hazards (4). Therefore, current research focuses on identifying antioxidants from natural sources that includes plant polyphenols as well as novel peptides from dietary proteins such as zein, fish, egg and milk proteins (5-7). In this study, we report the antioxidant activity of soy protein isolate (SPI) as well as soya hydrolysate produced enzymatically and fractionated into 0-5 and 5-10 kDa fractions in a linoleic acid emulsion as determined by the ferric thiocyanate and thiobarbituric acid reactive substances (TBARS) methods.