Heat treatments of defatted soy flour: Impact on protein structure, aggregation, and cold-set gelation properties

This study reveals that mild heat treatments of defatted soy flour promote Maillard reaction and modify its protein techno-functional properties such as solubility, aggregation, and cold-set gelation. Glycation was promoted by treatments of defatted soy flour (DSF) at 60 degrees C for 12, 24, and 48 h, with and without relative humidity control (RHC and WRHC, respectively) at 79%. All samples presented a significant increase of glycation extent (GE), reaching the highest value after 48 hat RHC. Despite all samples presented a similar protein denaturation degree, the increase in GE was accompanied by a decrease of antitryptic activity. Protein solubility (PS) of DSF remained constant for treated samples WRHC. However, PS decreased progressively with the treatment time at RHC. SDS-PAGE of soluble proteins revealed a positive relation between band intensities and PS. Despite sample dispersions showed a protein particle size increment with treatment time, further aggregation after heat-treatments at 100 degrees C produced a similar protein size distribution among samples. Rheological and microstructural studies of cold-set gels of samples obtained WRHC revealed no changes in the maximum elastic modulus (G'(max)) and a slight increase of its pore sizes. However, samples obtained with RHC showed cold-set gels with a progressive G'(max) decrease with the treatment time, which could be related to a coarser gel microstructure. In the more extreme condition, the sample obtained after 48 hat RHC showed a total loss of gelation capability. These results can be used to address the development of new tofu-like food products with different rheological properties.