Differential scanning calorimetric study of meals and constituents of some food grain Legumes

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Abstract
Two thermal transitions were observed in soya bean meal by differential scanning calorimetry (DSC) and on the basis of previous data were ascribed to the denaturation of the 11S globulin, glycinin, and the 7S globulin, β‐conglycinin. Three DSC transitions were apparent in Vicia faba meal; one was associated with starch gelatinisation, and was absent from thermograms of soya bean because the latter stores oil rather than starch. The remaining two transitions were identified with the 11S globulin, legumin, and a 7S globulin, vicilin. The denaturation parameters of legumin and glycinin were very similar, in contrast to those of vicilin and β‐conglycinin. From this it was concluded that legumin and glycinin probably represent homologous proteins, whereas the two 7S proteins possess intrinsically different structures to one another. Cowpeas (Vigna unguiculata) and dry beans (Phaseolus vulgaris) afforded two major transitions which were assigned to 7S globulins and starch. From its DSC profile, the 7S globulins of cowpea appeared heterogeneous, but nevertheless possessed denaturation characteristics similar to those of vicilin of V. faba. In contrast, the thermal behaviour of the 7S globulin of dry beans (glyco‐protein II) was distinct from that of any of the other 7S globulins investigated. Three protein transitions were observed in the three lupin species examined. As in the case of soya bean, no starch transition was present. On the basis of the correspondence in transition temperature, one of the protein transitions was assigned to the 11S globulin component. Overall, this study indicates the potential of DSC as a means for obtaining data on seed protein homology from whole meals rather than the extracted proteins.