Analysis of lupin seed protein digestibility using gel electrophoresis and immunoblots.

Proteins from the seeds of 12 cultivars of three lupin species were analyzed by gel electrophoresis. Similarities between cultivars of the same species were noted. Antibodies raised against the three major globular proteins, conglutin alpha, beta, and gamma, of Lupinus albus cv. Ultra were used to probe immunoblots of crude extracts. The immunoblots revealed variations between cultivars not previously resolved and identified which protein-subunits were derived from which conglutin. In vitro digestibility studies were done on four of the lupin cultivars. During the digestion of these cultivars, the large protein units were shown to be degraded to smaller intermediates with specific molecular sizes. Some of the intermediate protein subunits were identified as being derived from conglutin beta. The digestibility of the four cultivars, based on the amount of identifiable protein in the ruminal fluid digest at 9 and 24 h, showed Ultra > Primorski > Juno > Danja. From this study a novel system of analyzing protein digestibility was devised.