Cellulase-treated deoiled rice bran: effects of treatment conditions on dietary fiber content and utilization for formulation of cookies

Deoiled rice bran is source of dietary fiber derived from the oil extraction process of rice bran. This material has a low soluble dietary fiber content, which needs to be improved from the nutritional perspective. In this work, a cellulase preparation was used to treat deoiled rice bran for the reduction in content of insoluble fiber and increase in that of soluble fiber. The effects of technological parameters on the insoluble, soluble, and total dietary fiber content of deoiled rice bran were evaluated, including cellulase dosage and incubation time. The determined treatment conditions under which a lowered insoluble fiber content and an improved soluble fiber content could be achieved were cellulase dosage of 6 U/g dry weight and incubation time of 2 h. The untreated and cellulase-treated deoiled rice bran were incorporated into cookies at different levels (0, 20, 30, 40, and 50%, on the basis of composite flour) to formulate cookies with increased fiber content. Cookies incorporated with cellulase-treated deoiled rice bran showed a lower insoluble fiber content, coupled with a higher soluble fiber content compared to products containing untreated bran. The addition of both types of deoiled rice bran increased the spread factor and decreased the hardness of cookies. However, cookies with 50% cellulase-treated deoiled rice bran particularly showed a higher hardness than cookies having untreated bran at the same level. Deoiled rice bran processed with cellulase preparation could be considered as good source of dietary fiber for making cookies with improved soluble fiber content.