The chemical composition and nutritive value of low- and high-tannin faba bean varieties

Abstract

A comparison was carried out of the chemical composition and nutritive value of three genotypes of faba beans: two with coloured flowers, Nadwiślański and the self-ending Tinos varieties, and one with white flowers, Caspar. Caspar seeds were heavier and had a lower hull proportion and lower crude protein content (27.2% DM). The largest differences were in the content of proanthocyanidins (condensed tannins) which ranged from 0.02% (Caspar) to 1.11% DM (Tinos). The proanthocyanidin content in dehulled seeds of coloured flower varieties was low (0.02%) and similar to that in the low-tannin variety, Caspar. The antitrypsic activity of the seeds varied, ranging from 3.4 TIU/mg (Caspar) to 7.4 TIU/mg (Tinos). The inositol phosphate (1.05-1.15% DM) and α-galactoside (2.1-2.4% DM) contents did not differ significantly. The new varieties, Caspar and Tinos, contained almost twice as much vicine and convicine (0.75% and 0.92%, respectively) as the traditional variety, Nadwiślański (0.36% DM). True digestibility coefficients (TD) for seeds determined on rats differed significantly and were: for Caspar, 83.9; Tinos, 77.3 and Nadwiślański, 80.0. Replacing whole seeds with dehulled seeds significantly increased the digestibility of dietary protein, to 88.1, 88.3 and 84.9, respectively. The net protein utilization (NPU) of the Nadwiślański and Tinos seeds were similar (55.4 and 55.0, respectively) and significantly lower than the NPU of Caspar seeds (61.0). The protein efficiency ratio (PER) of whole seeds supplemented with methionine and tryptophan were similar (Caspar, 2.21; Nadwiślański, 2.18; Tinos, 2.03) and insignificantly lower than the PER of dehulled seeds (2.37, 2.32 and 2.25, respectively).