Development of a pilot process for the production of alfalfa peptide isolate

Enzymatic membrane reactors are widely used to produce protein hydrolysates. During the past few years, leaf extracts have been recognised as a good source of high quality protein. The interest in alfalfa protein concentrate (APC), a hydrophobic protein with excellent functional and nutritional properties, is due to its abundance, to its amino acid composition and to its ribulose 1,5-biphosphate carboxylase–oxygenase content. In order to use this potential protein source in various fields (food, pharmaceutical and cosmetic industries), a pilot process for APC hydrolysis in a continuous stirred tank membrane reactor (CSTMR) was carried out. At pH 9.5 and 40 °C, the hydrolysis of APC (30.6 g dm−3) by Delvolase (2.4 g dm−3) with a residence time of 180 min, gave a conversion of 759 g kg−1 protein at steady state. Coupling the reactor with an inorganic ultrafiltration membrane (Carbosep M5) with a 10 kDa nominal molecular weight cut-off (NMWCO), allowed production of a soluble and reproducible peptide permeate with 23 g dm−3 of hydrolysed protein. Phenolic compounds, responsible for the brown colour of the permeate, were removed at pH 5.0 and room temperature by anion-exchange chromatography using Amberlite IRA900Cl, with a yield of 920 g kg−1. After electrodialysis and spray-drying of the decolorised permeate, an alfalfa peptide isolate (API) was obtained. It was soluble over the full pH range and its amino acid composition was comparable to that of the FAO/WHO standard. It could be used as a protein supplement in human diets and other fields. Copyright © 2003 Society of Chemical Industry