Removal of antinutritional compounds

Legume seeds contain a variety of anti-nutritional factors: 1) flatulence-producing factors, such as tri- and tetrasaccharides, raffinose and stachyose, verbascose; 2) protease inhibitors, such as trypsin and chymotrypsin inhibitors; 3) tannins; 4) phytic acid; 5) haemagglutinins or lectins; 6) favism-inducing factors (Nout & Rombouts, 1990). Cereal grains contain several anti-nutritional factors such as 1) phytic acid, 2) tannins, and 3) polyphenols (Sandberg & Svanberg, 1991; Svanberg et al., 1993; Matuschek et al., 2001). During the tempeh fermentation process, R. oligosporus can reduce or eliminate these anti-nutritional factors (Hachmeister & Fung, 1993; Rodriguez-Burger et al., 1998; III). Co-inoculation with R. oryzae may assist in the degradation of flatulence-producing compounds (Rehms & Barz, 1995; Wiesel et al., 1997). LAB can degrade phytates in sourdough (de Angelis et al., 2003) and reduce many other anti-nutritive factors in other fermented foods (Leroy & de Vuyst, 2004). Co-inoculation with selected LAB strains during barley tempeh fermentation might subsequently improve the nutritional quality of barley tempeh. In our study, 28% of the phytate was reduced during barley tempeh fermentation (III). Yeast can produce phytases, but co-fermentation of yeasts with R. oligosporus did not reduce phytate further than R. oligosporus fermentation alone (III). In contrast, 97% of the grain phytate could be removed by further modifying the pre-treatments of barley in the preparation of tempeh (Eklund-Jonsson et al., 2006).

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