Efficient isolation of lupin protein

The increasing demand for low cost and non-genetically modified vegetable proteins has pushed the food industry to explore alternative sources of protein. Lupin has similar protein content and amino acid profile to soy. The Australian sweet lupin (Lupinus angustifolius), a low alkaloid variety, is high in protein and fibre and low in fat, making it a potential ingredient for functional foods. A concentrated form of lupin protein with a protein content of 90% was prepared by alkaline extraction at pH 9.0 followed by acidic precipitation at eight different pH levels (4.0, 4.2, 4.4, 4.5, 4.6, 4.8, 5.0 and 5.5) covering the isoelectric points of major legume proteins. There was no significant difference (P > 0.05) in protein content and yield of lupin protein isolates precipitated at pH 4.4, 4.5, 4.6, 4.8 and 5.0. Instead of using pH 4.5 for lupin protein precipitation, a higher pH such as 5.0 can be used that would result in decreased acid usage, thus providing a more economical approach to protein isolate production.