Lipid Stability of Soybeans in Grains and Soybeans Processed as Tofu

Soybeans (Glycine max (L.) Merrill) contain bioactive substances. They are a functional, important food associated with reduced risks of chronic and degenerative diseases. This study assesses lipid stability and antioxidant in soy grains and processed soy tofu. The two soybean brands differed in antioxidant activity and total phenolic compounds, which ranged from 188.4 mg EAG.100g-1 and 3.17 to 1.56 umol of ferrous sulfate g-1. Both tofu samples only showed differences in total phenolic compounds, which ranged from 9.6 to 18.3 mg EAG.100g-1. Analysis of DPPH free radicals has not shown significant differences (P < 0.05) amongst analyzed soybean in grain and tofu brands; yet, we could identify antioxidant activities with an inhibition level above 50%. There was no significant difference among total lipid contents of the tested brands. Polyunsaturated and monounsaturated fatty acids found to be denser in soy and tofu samples were- linoleic, linolenic and oleic acid. The n-6/n-3 ratio values were satisfactory for soy and tofu. Thus, both soybean and tofu display significant antioxidant effects and are sources of polyunsaturated fatty acids.