FTIR and solid state C-13 NMR spectroscopy of proteins of wet cooked and popped sorghum and maize

Fourier transform infrared (FTIR) and solid state C-13 NMR spectroscopic me thods were used to investigate changes in maize and sorghum proteins on wet cooking and popping. FTIR spectra indicated that wet cooking led to protei ns in two normal sorghums, namely NI( 283 a red hybrid) and KAT 369 (a whit e variety), two sorghum mutants (P850029 and P851171) and a maize hybrid (P AN 6043) assuming more antiparallel intermolecular beta -sheet character, p ossibly at tile expense of some alpha -helical conformation. Solid stale C- 13 NMR, using the technique of Cross Polarisation Magic Angle Spinning show ed shifts of the protein carbonyl carbon and alpha -carbon resonances upfi eld on M et cooking in all samples, also indicating a change in protein sec ondary structure from alpha -helical to beta -sheet conformation. The exten t of secondary structural change on wet cooking seemed to be greater in sor ghum than in maize and may have a bearing on the inferior protein digestibi lity of wet cooked sorghum compared to maize. Popping produced the same sec ondary structural change as observed for wet cooking in both sorghum and ma ize. However, the extent of change on popping was less than on wet cooking in sorghum and maize. (C) 2001 Academic Press.