Enzyme-assisted aqueous extraction (EAEP) is an environmental-friendly method which is an alternative to conventional hexane oil extraction.During EAEP of soybeans,an additional by-product,residue fraction was produced.About 4.4 kg residue would be produced for every liter soybean oil extracted.The residue fraction of EAEP of soybeans contains substantial amount of fibers,which can be considered as a rich resource of dietary fiber.A soybean dietary fiber was prepared from EAEP residues and further modified through carboxymethyl substitution.According to the results of single factor experiments,Box-Behnken response surface methodology was conducted to investigate the correlation between operating parameters and degree of substitution (DS).The results indicated that the effects of four parameters on DS followed an order of etherification time,chloroacetic acid dosage,alkalization temperature,and etherification temperature.For optimizing the four independent variables,square regression analysis was performed.The regression model was fitted with determination coefficient R2 of 0.968 4 and optimal parameters were as follows:alkalization temperature was 25℃;dosage of chloroacetic acid was 1.05 times of the mass of raw fiber;etherification temperature was 70℃ and etherification time was 3.8 h.The DS under above conditions was 0.430 5.Compared with the raw sample,the water holding capacity,oil holding capacity and expansion capacity of modified fiber were 8.21g/g,3.80 g/g and 9.88 mL/g,which were improved by 89.61％,20.63％ and 114.32％,respectively.The infrared spectrum showed that carboxymethyl substitution was occurred during modification.The modified dietary fiber from EAEP of soybeans exhibited desired functional properties,which can be used in meat,beverage and bakery products.%大豆水酶法残渣可作为膳食纤维的来源.以大豆水酶法残渣为原料,对其中的膳食纤维进行羧甲基化修饰,在单因素试验的基础上,通过Box-Behnken响应面试验设计建立了碱化温度、氯乙酸添加量、醚化时间和醚化温度对羧甲基取代度的模型.研究结果表明,各参数对羧甲基取代度的影响程度依次为醚化时间、氯乙酸添加量、碱化温度、醚化温度.通过对试验结果的二次回归分析得到的最佳制备工艺为碱化温度25℃、氯乙酸添加量为膳食纤维质量的1.05倍、醚化温度70℃、醚化时间3.8h,在此最优条件下制备的水酶法膳食纤维羧甲基取代度为0.430 5,其持水率、持油率和膨胀率分别较修饰前提升了89.61％、20.63％和114.32％.红外光谱结果表明,制备的大豆水酶法膳食纤维发生了羧甲基取代反应.
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