Comparative study of the polypeptide profiles and functional properties of Sinapis alba and Brassica juncea seed meals and protein concentrates

Defatted meals and protein concentrates from six accessions of Sinapis alba and one accession of Brassica juncea mustard seeds were analysed for their polypeptide profile and functional properties. Two types of protein concentrates were prepared using acid-induced and calcium-induced protein precipitations. Meals from the S alba seeds had similar polypeptide composition, which was different from that of the B juncea meal. Non-reducing sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that two of the major polypeptides (50 and 55 kDa) in S alba seeds were susceptible to acid-induced precipitation but resistant to calcium-induced precipitation. The B juncea meal proteins were significantly (p < 0.05) more susceptible to heat coagulation than the S alba meal proteins. Emulsifying activity index was significantly higher (p <= 0.05) in the B juncea meal and protein concentrates when compared with similar products from S alba. It was concluded that the presence of a high-molecular-weight (135 kDa) disulfide-bonded polypeptide could have contributed to the lower emulsifying power of the S alba products when compared with the B juncea proteins that do not have this polypeptide. (c) 2005 Society of Chemical Industry.