3.1. Breaking stress (BS)
The values of breaking stress (BS) of extruded products under experimental conditions are presented in Table 2.
The highest valueof BS was 0.828 N/mm2 while extrusion was done at 160 C with
50 g/100 g (dry basis) protein content and 40 g/100 g (wet basis)
feed moisture. The lowest value of BS was 0.141 N/mm2 while
extrusion processing at 140 C with 40 g/100 g (dry basis) protein
content and 45 g/100 g (wet basis) feed moisture. According to the
BS, barrel temperature is the most significant affecting parameter
(p < 0.05). Response surface plot for protein content vs. moisture
for temperatures of 140 C, 160 C and 180 C as predicted by the
model are shown in Fig. 1. The results show that with an increase in
temperature, the BS values increased, especially for the high
protein and high moisture content product. The lowest BS appeared
when the barrel temperaturewas the lowest (Fig. 1A), the moisture
and protein content are at the highest level; the highest BS
appeared in Fig. 1C, when the barrel temperature is the highest, the
moisture and protein content are also at the highest level.
Barrel temperature and material moisture content significantly
(p 0.05) affected the BS and all the quadratic effects including
protein content, moisture content and barrel temperature, and
interaction effects including protein content and moisture content,
protein content and temperature content, moisture content and
temperature significantly affected BS. Lack of fit was not significant
relative to the pure error, which meant the model was well fitted.
The regression equation for the empirical relationship between BS
3.1. Breaking stress (BS)The values of breaking stress (BS) of extruded products under experimental conditions are presented in Table 2. The highest valueof BS was 0.828 N/mm2 while extrusion was done at 160 C with50 g/100 g (dry basis) protein content and 40 g/100 g (wet basis)feed moisture. The lowest value of BS was 0.141 N/mm2 whileextrusion processing at 140 C with 40 g/100 g (dry basis) proteincontent and 45 g/100 g (wet basis) feed moisture. According to theBS, barrel temperature is the most significant affecting parameter(p < 0.05). Response surface plot for protein content vs. moisturefor temperatures of 140 C, 160 C and 180 C as predicted by themodel are shown in Fig. 1. The results show that with an increase intemperature, the BS values increased, especially for the highprotein and high moisture content product. The lowest BS appearedwhen the barrel temperaturewas the lowest (Fig. 1A), the moistureand protein content are at the highest level; the highest BSappeared in Fig. 1C, when the barrel temperature is the highest, themoisture and protein content are also at the highest level.Barrel temperature and material moisture content significantly(p 0.05) affected the BS and all the quadratic effects includingprotein content, moisture content and barrel temperature, andinteraction effects including protein content and moisture content,protein content and temperature content, moisture content andtemperature significantly affected BS. Lack of fit was not significantrelative to the pure error, which meant the model was well fitted.The regression equation for the empirical relationship between BS
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