The Nutritive Value of Ten Inbred Lines of Faba Beans (Vicia faba L.) in Relation to their Content of Antinutritional Constituents and Protein Quality

Abstract

AbstractTen inbred lines of fabe beans (Vicia faba L.) selected according to their quality characters have been investigated for carbohydrates, proteins, and antinutritional compounds. Digestible energy, N‐balance trials with growing rats comprising determination of the protein digestibility and biological value were used as criteria in connection with comprehensive chemical‐biochemical analysis.The chemical composition of the ten lines showed a considerable diversity as cad the results from the rat crisis. However, the content of vicine and convicine in all or the investigated lines were below the level previously found to have effects on the nutritive value, Starch, protein and fibre were the quantitatively dominating seed constituents, and all showed great variation among the lines.The starch content was not correlated to the quality or nutritive value of the seed, whereas the protein content was negatively correlated to the biological value and net protein utilization. These correlations followed the content of essential amino acids, lysine, threonine and methionine in the faba bean proteins. The content of the sulfur‐containing ammo acids cysteine and methionine are especially dominant factors for protein quality. A simple method for total sulphur determination was found nut 10 be a sufficiently reliable technique for evaluating the content of methionine and cysteine in the faba beans.Tannin, insoluble‐ and total dietary fibre are phenolic aromatic compounds which were negatively correlated with the faba bean quality as expressed by digestible energy, the protein digestibility and the biological value of the faba beans. The results obtained have also revealed, that it is not sufficient to consider tannin as a group in relation to the faba bean quality. We need to separate and evaluate the different types, of phenolics in relation to the variations in quality of faba beans. Some of the low molecular weight (LMW) phenolics in the faba beans seem 10 be involved in inhibitory effects on hydrolase enzymes, chymotrypsin and trypsin. Trypsin and chymotrypsin from different animals were different in their sensitivity to faba bean inhibitors and additional experiments are required to reveal details about these effects. It has also been revealed that fructosans Lind LMW carbohydrates (oligosaccharides) are important in relation to the quality of faba beans.