Comparison of the effects induced by different processing methods on sorghum proteins

The effects induced by cooking, dry heating, popping, fermentation and germination on sorghum proteins were studied. Changes promoted by these processing methods were compared via sodium dodecyl sulfate polycrylamide gel electrophoresis (SIDS-PAGE), in vitro protein digestibility (IVPD) assay and Fourier Transform Infrared (FT-IR). Cooking decreased protein digestibility and extractability. With dry heating, a decrease of only 4% in protein digestibility was observed. in these samples protein extractability was not affected. Popping had no effect on protein digestibility, however, it was noticed a decrease of protein extractability of popped samples. Fermentation and germination promoted an increase of 39.6% and 20.8% in the protein digestibility, respectively, and an increase in protein extractability. FT-IR analysis and multivariate correlation (PLS1) showed a calibration of protein digestibility values allowing quantification of unknown samples. As dry heated samples have practically the same digestibility values as unprocessed samples, we concluded that water plays an important role in deleterious effects of cooking. (c) 2009 Elsevier Ltd. All rights reserved.