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HTST extrusion of starch-lipid systems
Abstract
Corn starches containing 0-70% amylose were extrusion cooked with various lipids. Formation of complexes between the amylose portion of starches and various lipids was observed by DSC, X-ray diffraction patterns of extruded starches and iodine binding characteristics. The quantities of complexes formed during extrusion were determined by reductions in iodine binding capacities and apparent amylose contents. Addition of fatty acids and monoglycerides resulted in decreased iodine binding. $\lambda\sb{\rm max}$'s and ratios of absorbances at 630 and 520 nm also decreased. Among the fatty acids of different chain lengths, myristic acid gave maximum binding at 110$\sp\circ$C while the maximum for stearic acid was at 140$\sp\circ$C. Response surface methodology was used to determine the optimum extrusion barrel temperature, screw speed and feed moisture content for maximum complexing of starches with lipids. Only barrel temperature significantly affected the binding of lipids. In the presence of lipids, the functional properties of the extrudates also were affected only by temperature. Additionally, regression models were developed for estimating IBC, apparent amylose content and expansion ratios, bulk densities and water solubility indexes for processing variables in the ranges of 110-170$\sp\circ$C barrel temperature, 110-170 rpm screw speed and 19-25% feed moisture content. Effect of addition of various oils (triglycerides) to starches prior to extrusion resulted in modification of expansion ratios, bulk densities and water solubilities of extrudates. Addition of oils was found to result in a slight lubrication effect at 4% substitution level. GPC was used to study the changes in macromolecular structure of extrudates. The ultrastructure of starches also was modified upon extrusion with various lipids.
Subject Area
Chemical engineering|Food science
Recommended Citation
Bhatnagar, Sandeep, "HTST extrusion of starch-lipid systems" (1993). ETD collection for University of Nebraska-Lincoln. AAI9402388.
https://digitalcommons.unl.edu/dissertations/AAI9402388