6 Apr 2004 13:30
Unit:
Wageningen University
Location:
Aula (gebouw 362), Gen. Foulkesweg 1, Wageningen
Promotor:
prof.dr.ir. M.A.J.S. van Boekel (Product Design and Quality Management)
Co Promotor:
dr. H. Gruppen
Legumin, vicilin, and convicilin are the three storage proteins of pea. In this thesis characterisation of purified protein fractions lead to the conclusion that convicilin is not a separate protein, but a subunit (denoted alpha-subunit) of the extracted vicilin protein. Further experiments showed that these alpha-subunits increase the minimum gelling concentration of purified pea proteins at near-neutral pH, and cause transparent heat-induced gels to be formed. This behaviour was attributed to repulsion of the N-terminal extension regions of the alpha-subunits. These subunits also appeared to have an impact of the gelation of the pea protein isolates when present in sufficient quantity. Heat-induced gelation of legumin was compared with its analogous protein in soybean. Overall results showed that both proteins have the same physical and chemical driving forces acting during gelation, but soybean glycinin, unlike legumin, forms ‘reheatable’ gels. Comparison of the amino acid profiles of the two proteins gave no indication as to why these homologous proteins should form gels with different ‘reheatability’. The contribution of legumin to pea protein isolate gelation was cultivar specific. Disulphide bonds played a role in protein isolate gelation, but they did not demonstrate the gel strengthening ability that they are often reported to posses.
The research was spondered by the NWO-STW Programme Profetas.