A study of changes in wheat protein during bread baking using SE-HPLC

Samples of bread at different stages of baking were divided into three sections viz. crust, center and base. The sections were freeze-dried, ground and sieved, and changes in protein were followed using SE-HPLC. Sonication was used to solubilize proteins in SDS buffer pH 6.9. A decrease in extractable protein with time of baking was shown by the decrease in total area of the SE-HPLC profile. The center section of bread showed the maximum decrease in extractable protein as compared to the crust and base, which could be due to the differences in rate of temperature change as well as moisture content in the different sections of bread. To check the nature of cross-links formed during baking causing insolubility of proteins, a freeze dried sample of crust (20 min baking) was reduced with β-mercaptoethanol (ME) at room temperature. Almost complete reduction of protein into subunits suggested that disulfide bonds are the major cross-links formed during baking.