Date of Award
Doctor of Philosophy
Patricia A. Murphy
An examination of the effects of low-cost extrusion on some nutritional and sensory properties of whole soybean/whole corn mixtures was carried out;Ground soybeans and corn at ratios 60:40, 70:30, 80:20, and 100:0 soybean:corn were processed with an Insta Pro 600 extruder cooker. Extruder exit temperatures were 127, 138, 149, and 160°C. Soybean trypsin inhibitor activity was destroyed 48.9 to 98.8% as exit temperature increased. Extrusion had no major effect on the tocopherol isomers. Lipoxygenase was completely inactivated by extrusion. In vitro protein digestibilities of samples extruded at 127°C were significantly lower than samples extruded at higher temperatures. Residual lipase activity ranged from 2.7 to 63.7 micromoles H[superscript]+· min[superscript]-1· g[superscript]-1;The effects of temperature and relative humidity (RH) on the aroma deterioration during storage of the 80:20 blend extruded at 150°C were studied. The temperatures were 15, 25, 35, and 45°C and the relative humidities were 11 and 65%. Production of volatiles followed apparent zero order reaction kinetics up to 12 weeks of storage. Activation energies were higher at the lower RH for the majority of the compounds analyzed. Activation energies ranged from 4.2 to 37.4 Kcal/mole. Free fatty acid (FFA) production was observed at 35 and 45°C. The aromas of all the samples stored at 65% RH were judged undesirable by an untrained panel by week six of storage. Samples stored at 25 and 15°C and 11% RH were judged not undesirable by more than 60% of the panelists after up to 14 weeks of storage.
Digital Repository @ Iowa State University, http://lib.dr.iastate.edu/
Gabriel Jaime Guzman
Guzman, Gabriel Jaime, "Properties of soybean-corn mixtures processed by low-cost extrusion " (1989). Retrospective Theses and Dissertations. 9190.