Uric acid retention ranged from 65.1 to 76.6%. Table II presents the results of the analysis of variance for percent uric acid reten- tion in the extrudates as affected by the extrusion variables. Analysis of variance revealed that temperature was the only vari- able that affected (P < 0.05) the retention of uric acid in the extrudates. Feed moisture did not significantly affect (P > 0.05) retention of uric acid within the range tested. Uric acid is relatively insoluble in water (Lehninger 1979); therefore a small increase in the water content of wheat flour did not change the retention of uric acid in extrudates. No interaction was found (P < 0.05) between temperature and moisture content.
The mean percent uric acid retention of the extrudates as affected by the heat treatment is shown in Table III. A difference (P < 0.05) was found in the percent uric acid retained in the extru- dates processed at 120'C when compared with the uric acid retained in extrudates processed at 160'C. The highest retention of uric acid (74.2%) was at 160'C, whereas the lowest retention (68.4%) was found at 120'C. This appeared at first to be illogical. However, the reason for the higher retention of uric acid at a higher temperature was attributed to differences in the residence time of the material at different temperatures. Chen et al (1991) reported that when corn meal was extruded (at temperatures of
100-200'C and moisture contents of 20-30%), a lower tempera- ture at any given moisture content caused the feed to become more viscous and increased the residence time. Therefore, longer expos-
ure to heat at a lower temperature must have been more effective in degrading uric acid than higher temperature with shorter residence time.
The results of this study show that uric acid in contaminated wheat flour can survive heat to a relatively high degree. On aver- age, about 72% of uric acid was retained in extruded wheat flour. This high retention level indicates that uric acid is relatively stable at temperatures commonly encountered in processing operations
and could be used as an indicator of insect contamination in extruded products. The degradation of uric acid in heat-processed food would depend on the level of temperature and the extent of heating of the contaminated food. The results presented here provide information that can be used as a basis for future investi- gations of extrusion and other thermal processes. Studies involv- ing a wider range of temperature, as well as close measurement of the residence time of materials, are suggested.
Uric acid retention ranged from 65.1 to 76.6%. Table II presents the results of the analysis of variance for percent uric acid reten- tion in the extrudates as affected by the extrusion variables. Analysis of variance revealed that temperature was the only vari- able that affected (P < 0.05) the retention of uric acid in the extrudates. Feed moisture did not significantly affect (P > 0.05) retention of uric acid within the range tested. Uric acid is relatively insoluble in water (Lehninger 1979); therefore a small increase in the water content of wheat flour did not change the retention of uric acid in extrudates. No interaction was found (P < 0.05) between temperature and moisture content.The mean percent uric acid retention of the extrudates as affected by the heat treatment is shown in Table III. A difference (P < 0.05) was found in the percent uric acid retained in the extru- dates processed at 120'C when compared with the uric acid retained in extrudates processed at 160'C. The highest retention of uric acid (74.2%) was at 160'C, whereas the lowest retention (68.4%) was found at 120'C. This appeared at first to be illogical. However, the reason for the higher retention of uric acid at a higher temperature was attributed to differences in the residence time of the material at different temperatures. Chen et al (1991) reported that when corn meal was extruded (at temperatures of100-200'C and moisture contents of 20-30%), a lower tempera- ture at any given moisture content caused the feed to become more viscous and increased the residence time. Therefore, longer expos-ure to heat at a lower temperature must have been more effective in degrading uric acid than higher temperature with shorter residence time.The results of this study show that uric acid in contaminated wheat flour can survive heat to a relatively high degree. On aver- age, about 72% of uric acid was retained in extruded wheat flour. This high retention level indicates that uric acid is relatively stable at temperatures commonly encountered in processing operationsand could be used as an indicator of insect contamination in extruded products. The degradation of uric acid in heat-processed food would depend on the level of temperature and the extent of heating of the contaminated food. The results presented here provide information that can be used as a basis for future investi- gations of extrusion and other thermal processes. Studies involv- ing a wider range of temperature, as well as close measurement of the residence time of materials, are suggested.
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