Abstract: The number of consumers preferring natural and organic foods to those that involve synthetic chemicals has recently shown dramatic growth. As such a native isoelectrically precipitated Soy Protein Isolates (SPIs) were prepared from full-fat and defatted flours using amaranth (Aamaranthus tricolor L.) lye (pH>12.5) and lemon extract (pH<2.5) as natural food-plant-based chemicals, replacing the conventional synthetic ones (NaOH and HCl, respectively). Functional properties, total polyphenol content and antioxidant activity of the natural SPIs were compared to those of synthetic ones. All the SPI samples qualified to be soy protein isolates with a minimum protein content of 91.21%. The natural SPI showed significant increase in emulsion stability (p≤0.05). While higher values with narrow margins were shown by the synthetic than the natural SPIs in oil absorption (0.66±0.02, 0.50±0.01%, respectively), emulsion capacity (56.53±0.57, 55.50±0.39%), foam stability (11.33±0.61, 10.40±0.40%). No significant difference was observed in water absorption capacity. The DPPH assay showed increased antioxidant activity in the natural SPI although its total polyphenol content was lower. Thus, SPI with functional properties similar to those of conventional ones can be naturally processed using amaranth ash and lemon extracts as alternative chemicals to addressing the fear of consuming synthetic chemical by health-conscious natural and organic food consumers.
Moses Vernonxious Madalitso Chamba, Yufei Hua, Quirino Dawa, Odlon Jakpo and Caimeng Zhang, 2013. Effects of Synthetic and Natural Extraction Chemicals on Functional Properties, Polyphenol Content and Antioxidant Activity of Soy Protein Isolates Extracted from Full-Fat and Defatted Flours. Journal of Food Technology, 11: 52-59.