Physicochemical properties of wet-glycated soy proteins

On a lab-scale, glycation is generally a lengthy process that would be costly if replicated on an industrial scale. In this study, a simplified method for glycating soy protein isolate has been developed. Soy proteins were glycated with allulose, fructose, and glucose in the presence of water. Free amino group content, protein solubility, browning index, and reducing sugar concentration were measured for the glycated proteins. Fourier Transform Infrared (FT-IR) spectroscopy was used to examine structural changes, and hydration behavior was evaluated using Time Domain Nuclear Magnetic Resonance (TD-NMR) relaxometry through T2 relaxation time measurements. The results showed that proteins could be glycated under these austere conditions and with minimal control. It was found that high temperatures were not favorable for glycation, and lower temperatures could be preferred. At high temperatures, proteins become more denatured and less soluble, as shown through the Lowry method for protein solubility and TD-NMR results. Higher browning was observed at a higher temperature, primarily when allulose and fructose were used for glycation. The highest glycation was obtained with glucose, while allulose and fructose showed the lowest reactivity under the proposed conditions. Proteins with low solubility had longer T2 relaxation times, indicating more free water and weaker water-binding capability.