The endogenous components of okara can affect the extraction and modification of insoluble dietary fiber (IDF). This study was intended to investigate the effect of extraction and purification of IDFs from okara affected by the endogenous components and composite enzyme Viscozyme® L. After that, the physicochemical, functional, and structural characteristics of IDFs were analyzed. The results showed that with the purification of degreasing, deproteinizing and destarching, Viscozyme® L can accurately act on the cell wall of okara, leading to the increase in specific surface area of IDF and the formation of honeycomb-like structure. In accordance with the X-ray diffraction and Fourier-transform infrared spectrum investigations, relative crystallinity decreased and certain cellulose components were reallocated and changed into soluble dietary fiber. Moreover, the modified IDF showed improved water-holding capacity (10.73-11.59 g/g), oil-holding capacity (5.37-6.60 g/g), and swelling capacity (8.99-12.37 mL/g), leading to improved adsorption capacities of glucose (maximum: 39.60 mg/g), cholesterol (14.54-33.56 mg/g at pH 7; 10.94-19.37 mg/g at pH 2), and cholate and better cation-exchange capacity. The outcomes demonstrated the potential for the acquired IDFs, particularly the high-purity modified-IDFs T3 and T4 , to be exploited as functional fiber components in the food sector. PRACTICAL APPLICATION: This study advances the understanding of the internal mechanism of modified insoluble dietary fiber (IDF) with different purities in okara. The obtained high-purity modified IDF can be employed as a functional fiber raw material in the manufacture of functional foods, and can also be utilized to assist in the treatment of some illnesses due to its well-established in vivo function.
Keywords: enzymatic modification; insoluble dietary fiber; okara; physicochemical properties; purity.
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