Effect of molecular and supramolecular characteristics of select dietary fibers on extrusion expansion

Orane Antonie Blake, Purdue University

Abstract

Dietary fiber has a number of health benefits. However, its incorporation into extrusion puffed products limits their puffing ability and reduces their crispness and bowl life. A number of factors were found to determine the effect of dietary fiber on extrusion puffing. Reduction in particle size of insoluble fibers, such as cellulose and corn bran, improved extrusion expansion, but only to a limited extent. Reduction in particle size of cellulose to less than 60 μm did not improve sectional expansion index. The supramolecular structure of cellulose, i.e. degree of crystallinity and the extent of ferulic acid cross-linkages of corn bran, had a significant effect on extrusion expansion of high fiber extrudates. Using model systems, the degree of crystallinity of cellulose had an inversely proportional relationship to extrusion expansion. Modification of the supramolecular structure of corn bran using alkali treatment significantly enhanced sectional expansion index of extrudates containing 26% total dietary fiber. Incorporation of 26% hemicellulose B from corn bran of suitable molecular weight in cornmeal also facilitated significant cross-sectional expansion of extrudates, such that their degree of expansion was similar to a control containing no added fiber. The molecular weight of soluble fibers played a significant role in determining the degree of extrusion expansion of extrudates; this was shown using corn fiber gum, arabinogalactan and CMC. An optimum number average molecular weight of 2.1–2.5 x 105 significantly improved the sectional expansion index of extrudates containing 30% CMC. A branched polymer versus linear polymers was also found to better facilitate increased extrusion expansion in high fiber puffed products.

Degree

Ph.D.

Advisors

Campanella, Purdue University.

Subject Area

Food science|Agricultural engineering

COinS