Enzymatic determination of soluble and insoluble dietary fiber in rice and wheat bran.

The information about dietary fiber presents controversies in many research areas such as in nomenclature, related illnesses, recommended quantities and terminology, mainly because of lack of analytical data. Different needs and interests for the dietary fiber composition of foods and forages have led to a proliferation of methods for its analysis. This research, a further adaptation of the enzymatic method of Asp et al. (1983) for its application is proposed for rice and wheat bran, byproducts of agroindustries in the southern region of Rio Grande do Sul (Brazil). The inclusion of Amyloglucosidase in the proposed methodology contributed to the decrease in the content of residual starch at the end of the experiment, like Prosky et al (1992). To increase the efficiency of the enzyme system in this type of samples, other changes were made with respect to incubation time and proteolytic enzyme concentration. In the final adaptation, a decrease of 51.33% of the starch content was observed in rice bran (RB) and of 52.93% in wheat bran (WB). This decrease was also verified in the model system (MS) (52.08%), which demonstrates the adequacy of the proposed adaptation. With respect to the residual protein, it was verified that the measures adopted provoked a reduction of 42.15% (RB), 52.19% (WB) and 42.11% (MS) as compared to the original method. Then the proposed conditions has been shown to be efficient in decreasing the level of interference (indigestible starch and protein) in the quantification of dietary fiber in rice and wheat bran.