Food Structure


Three different pure cellulose fibers (James River Corporation, NJ) with lengths of 22, 60 and 110 pm were used at 1, 2, 4, 6, 8 and 10% concentrations with normal corn starch. The fiber-starch mixtures were extruded (C.W. Brabender Laboratory Extruder) at moisture contents of 14, 18 and 22% (db), 140°C barrel temperature and 140 rpm screw speed. The expansion ratio of the starch-fiber extrudates varied from 5.0 to 13.3. The maximum expansion ratio of 13.3 was obtained with 2%-60 mm fiber and 14% (db) moisture content. Increasing fiber concentration and moisture content generally reduced the expansion volumes. Water solubility values varied from 0.7% (db) for 110 mm nature fiber to 9.1% (db) for 2% of 22 mm fiber . Gel permeation chromatographic (GPC) fractionation of the starch-fiber extrudates showed extensive degradation of fraction I {amylopectin) with increasing fiber concentrations and fiber lengths. Iodine binding abilities of the fractions varied widely. Water solubility, GPC and iodine binding capacity data generally indicated some chemical reactions among the molecules of starch and fiber.

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