Amino acid profile in fermented Lupinus angustifolius L. cv zapaton

Resumen del trabajo presentado a la 6st European Conference on Grain Legumes: Integrating Legume Biology for Sustainable Agriculture, celebrada en Lisboa (Portugal) del 12 al 16 de noviembre de 2007.Legumes are important components in the traditional diets of many regions of the world and constitute an excellent source of protein as well as of other macro and micronutrients. Among them, sweet lupin is a very interesting crop since it can be cultivated in regions with extreme climates and poor grounds, having high protein content (30 to 45%). lt has been reported that lupin has lower levels of non nutritive factors, such as phytic acid and protease inhibitors compared with other legumes. However, lupin presents high alpha-galactoside contents (7-15%) that interfere in their consumption since they are flatulent-causing factors. Many studies have been carried out to develop processes to reduce these non nutritive sugars and to enhance the nutritional quality of legumes. Fermentation of legumes is an ancient technology and one of the most practical methods for preserving food and enhancing their nutritional and organoleptic qualities. lt has been reported that fermentation cause desirable changes in taste and texture, the breakdown of antinutritional factors and a general improvement in the nutritional value of legumes. However, there is scarce information about the effect of different fermentation conditions on the amino acid content of the fermented product and it might be interesting to select those fermentation conditions which provide higher nutritional value. The aim of this work was to study the effect of different fermentation conditions on the amino acid profile of lupin (Lupinus angustifolius cv. zapatón) seeds. For this purpose, lupin seeds were processed by natural or induced fermentation using different microorganisms (Lactobacillus plantarum, Bacillus subtilis, Aspergillus oryzae and Rhizopus oryzae) and total and free protein amino acids were analysed by HPLC-PAD. Raw lupin seeds present Glu, Asp and Arg as the major components among non-essential amino acids (NEAA), while Val, Leu, and Lys predominated among essential amino acids (EAA). Low levels of sulphur amino acids were also found. Fermentation of lupin affected NEAA composition increasing the amounts of Asp and Glu. In this way, an upward trend for most of EAA in fermented lupin was also observed, although higher EAA content was found in lupin after induced fermentation by starter cultures than in natural fermentation. In addition, differences on essential amino acid composition were observed depending on the starter culture used. L. plantarum and B. subtilis brought about the highest increases in the EAA content compared with mould strains (A. oryzae and R. oryzae ). Finally, lupin fermentation trought about rises in the amounts of free protein amino acids compared to raw seeds and the highest performance was found in lupin fermented by B. subtilis or A. oryzae. Therefore, results indicated that lupin fermentation with B. subtilis is the best choice to improve the nutritional quality of lupin since a suitable EAA composition and high levels of free protein amino acids were achieved.The authors are indebted to the Spanish Comision lnterministerial de Ciencia y Tecnología (CICYT) for their financial support of project AGL 2004-0886/ALI .Peer reviewe