Characterization of soy curd residue and full-fat soy flour as protein-based food ingredients

Abstract

The study investigated the soy curd residue and full-fat soy flour as potential protein-based food ingredients. Standard protocols were used to determine proximate parameters, functional properties, markers of oxidative stability under shelf storage, colour (CIE L* a* b*), and microbial quality of the flours. Commercial Afayak soybean varieties were used to prepare soy curd residue flour and two differently treated soy flours, namely full-fat soy flour and cold-water extracted full-fat soy flour. Findings from the study indicate that processing treatment and storage time significantly (p<0.001) affected the parameters measured. Cold-water extraction of full-fat soy flour resulted in a significantly (p<0.001) higher protein content denoting 1.0, and 1.2-fold than full-fat soy flour and soy curd residue, respectively. Full-fat soy flour showed the highest peroxide, acid, and p-anisidine (p < 0.001) under processing and storage conditions. Soy curd residue was the most oxidatively stable among the samples; however, it was noted that cold-water extraction of full-fat soy had better oxidative stability than full-fat Soy flour. After 12 weeks of storage, peroxide and acid values were below the acceptable limit of 10 mEq/Kg and 0.6 mg/KOH/g, respectively. The study supports the hypothesis that the proximate composition, physicochemical properties, and oxidative stability of soy-based flours are affected by the sample processing method and storage time. The study concludes that the samples characterized in this study are oxidatively stable, protein and energy-rich and may be ideal ingredients for food product development with desirable functional properties.