Energy value and bioactive proteins of inulin‐enriched tofu produced by hydrothermal process with chymosin‐pepsin rennet

Summary Nutritional properties of inulin‐enriched tofu obtained after hydrothermal cooking of soymilk, using chymosin‐pepsin rennet and inulin as a functional ingredient, were assessed. This procedure significantly differs from the traditional one. The residual activity (rTIA) of trypsin inhibitors (TIs) and lectins, content of proteins, carbohydrates, fats and their energy values (EV) were suitable for human nutrition. Inulin‐enriched tofu was characterised with low rTIA (3.08–5.71%) and TIs content of 3.62–18.99%. Content of Kunitz and Bowman‐Birk TIs as well as total TIs content (r = 0.98) in tofu were strongly correlated with tofu protein content. Content of Bowman‐Birk polymeric forms (3.11–5.36%) was higher than Bowman‐Birk monomeric forms (0.51–2.31%) in inulin‐enriched tofu. Low urease activity (0.60–1.78%) indicated that soybean was heated adequately to inactivate TIs. Increasing content of inulin did not increase tofu EV (˜18 kJ per g tofu). The proximate composition of inulin‐enriched tofu, advantageous rTIA and a very low EV qualifies this product for human nutrition. Inulin‐enriched tofu was characterised with low residual trypsin inhibitors activity. Low urease index activity indicated that tofu was heated adequately to inactivate trypsin inhibitors. Lectins are firmly bound to the gel network of soy protein/oligosaccharide system. Increasing concentrations of inulin did not increase tofu energy values. ‘Functional’ firm tofu with low‐energy and high‐nutritional values was developed. ​