Effect of aqueous, acid and alkaline thermal treatments on the protein quality of Lupinus campestris seed

摘要

Increasing importance is being given to the genus Lupinus (Lupinus spp) as a possible soybean (Glycine max) substitute in human food. Lupinus campestris seed has a similar chemical composition to soybean seed and contains 44 % protein and 13 % oil. Lupin protein is low in the sulphur amino acids. However, when supplemented with DL-methionine its biological value increases. Lupin seed utilisation has been limited because of the presence of toxic quinolizidine alkaloids (QAs). The objective of this work was to reduce, or eliminate, the alkaloids trough aqueous, acid or alkaline thermal treatments and to determine the improvement in the protein quality following treatment. The results showed that the most efficient treatment for alkaloid elimination was the alkaline one. The protein content increased with both treatments from 44 % to 50 - 53 %. Although the protein concentration was higher with all the treatments, it was not possible to determine its biological value because the experimental animals refused to eat any diet and finally died. Supplementation of debittered lupin meals, with 0.5 DL-methionine gave a PER value of 2.04. However, this was lower than the casein PER of 2.45. The PER results showed that the alkaline thermal treatment was the best. The apparent digestibility was more than 90 % for all treatments. Alkaline treated seed had the highest digestibility (93 %).