Abstract Effects of nano-sized (NDF, 370 nm) and micro-sized (MDF, 110 μm) dietary fibers on gelling properties, water state and microstructure of tofu were investigated. Soymilk was mixed with different volumetric ratio of NDF or MDF suspension (0–50%) to make tofu. As the volumetric ratio of NDF suspension increased, yield, moisture, fiber content, syneresis and whiteness of tofu gradually increased, parameters of texture profile analysis (TPA) continuously decreased, while water holding capacity fluctuated. Measurements on relaxation times (T21 and T22) and corresponding peak areas by nuclear magnetic resonance (NMR) indicated more immobilized water while less free water as the ratio increased. With respect to NDF, changes of MDF suspension ratio led to the same change tendency of TPA parameters, but opposite of whiteness. The other parameters as mentioned above increased and then decreased as the ratio increased up to 50%. When added at the same ratio (> 30%), MDF tofu showed significantly lower yield, fiber content, synersis and whiteness, while higher TPA parameters. Proton density analysis showed that water was more evenly distributed in the NDF tofu than that of MDF tofu. Light microscopy and SEM confirmed that NDF tofu formed porous and disconnected gel matrix, in which the NDF particles were evenly distributed, while MDF fragments were randomly imbedded in the continuous gel matrix of tofu. Although being more uniformly and steadily entrapped in the tofu matrix, NDF more pronouncedly impeded the gelling ability of soymilk than MDF, which might be due to the stronger interactions with soybean proteins and water.

中文翻译：

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不同粒径豆渣膳食纤维对豆腐凝胶凝胶特性、水态及微观结构的影响

摘要 研究了纳米级（NDF，370 nm）和微米级（MDF，110 μm）膳食纤维对豆腐凝胶特性、水分状态和微观结构的影响。将豆浆与不同体积比例的 NDF 或 MDF 悬浮液（0-50%）混合制成豆腐。随着NDF悬浮液体积比的增加，豆腐的产量、水分、纤维含量、脱水收缩和白度逐渐增加，质构剖面分析（TPA）参数不断下降，持水能力波动。通过核磁共振 (NMR) 对弛豫时间（T21 和 T22）和相应峰面积的测量表明，随着比率的增加，更多的固定水和更少的游离水。对于NDF，MDF悬浮率的变化导致TPA参数的变化趋势相同，但白度相反。上面提到的其他参数随着比例增加到50％而增加然后减少。当添加相同比例 (> 30%) 时，MDF 豆腐的产量、纤维含量、脱水收缩率和白度显着降低，而 TPA 参数更高。质子密度分析表明，与中密度纤维板豆腐相比，中密度纤维板豆腐中的水分分布更均匀。光学显微镜和扫描电镜证实NDF豆腐形成多孔且不连续的凝胶基质，其中NDF颗粒均匀分布，而MDF碎片随机嵌入豆腐的连续凝胶基质中。尽管 NDF 更均匀、更稳定地包裹在豆腐基质中，但与 MDF 相比，NDF 更明显地阻碍了豆浆的胶凝能力，这可能是由于与大豆蛋白和水的相互作用更强。