Germination alters the chemical composition and protein quality of lupin seeds

Abstract

Abstract The chemical composition and protein quality of the kernels from Lupinus angustifolius seeds were compared with that for sprouts after 6 days germination. Germination resulted in an apparent increase in protein content from 395 g kg −1 to 435 g kg −1 DM. Fat and carbohydrate contents decreased. The oligosaccharide content of the sprouted lupin fell to a negligible level, while the phytate and alkaloid concentrations fell from 4.7 g kg −1 to 1.6 g kg −1 and from 0.72 g kg −1 to 0.16 g kg −1 , respectively. The quality of lupin kernel protein was poor with a protein efficiency ratio (PER) of 1.45±0.15. Supplementation of kernel with DL‐methionine (2.0 g kg −1 ) increased the protein quality (PER = 2.87±0.17) to that of casein (PER = 2.86±0.18). Germination reduced protein quality (PER = 0.44±0.16), and did not improve apparent protein digestibility (APD kernel = 80.4%; APD sprout = 77.5%). Supplementation of sprout protein with DL‐methionine (2.0 g kg −1 ) increased the protein quality (PER = 2.57±0.20). The total sulphur‐containing amino acid concentration of lupin kernel protein, 1.9 g per 16 g N was low, and decreased further to 1.3 g per 16 g N in the sprout, a drop of 32%. The results showed that germination of lupin seeds reduced the concentration of the anti‐nutritive factors; however, it also reduced protein quality.