The aim of this study was to determine the effects of different soy protein concentrate (0, 15, 30, and 45%), defatted soy flour (0, 10, 20, and 30%), and wheat flour (10, 20, and 30%) contents replacing fish meal on physiochemical properties of extruded aquatic feed by using a twin screw extruder. The moisture content, barrel temperature, die diameter, and screw speed were adjusted to 45%, 137oC, 4 mm, and 250 rpm, respectively. With the higher amount of soy protein concentrate replacing fish meal, the expansion ratio, swelling ratio, and water stability increased significantly while specific length and water holding capacity decreased significantly. With the increasing defatted soy flour content, expansion ratio increased significantly, but specific length, water holding capacity and water stability decreased significantly. With increase in the wheat flour content, the specific length significantly decreased while the water stability significantly increased. In conclusion, aquatic feed quality was optimized in this study and could be used in the future.

The aim of this research is to evaluate the impact of various process conditions on the physical properties and digestibility of extruded fish feed at different barrel temperatures (120, 130, and 140oC) and moisture contents (35, 40, and 45%). The expansion ratio decreased with increasing the moisture content. The hardness was negatively correlated with the expansion ratio. The bulk density decreased by increasing moisture content. The water holding capacity increased by increasing the moisture content and barrel temperature. Soaking time significantly (p<0.05) affected water stability and the best water stability was observed in all samples soaked for 1 h, but water stability was also stable at 2 h and 3 h. There was a significant increase in the protein digestibility of extruded fish feed, compared to that of the raw material.

The aim of this study was to evaluate the optimization extrusion variables on quality of textured vegetable protein by using response surface methodology. In this study, 50% soy protein isolate, 40% wheat gluten, and 10% corn starch were blended and 15% of the mixture was substituted with green tea. The moisture content (45, 50, and 55%), barrel temperature (130, 140, and 150oC), and screw speed (100, 150, and 200 rpm) were varied. A Box- Behnken design was used in this experiment. Second order polynomial regression equations were developed to relate the response to extrusion variables as well as to obtain a response surface plot. The independent variables had significant effects on the quality of the products and moisture content was the most significant. The lower moisture content led to the higher integrity index, lower nitrogen solubility index, lower water absorption capacity, higher texture, and higher cutting strength. The optimum conditions were identified as moisture content 47.78%, barrel temperature 150.00oC, and screw speed 196.05 rpm. Incorporation of green tea into protein materials could effectively improve the nutritional value of the product. Understanding these optimized extrusion variables on the product quality was useful for producing textured vegetable protein in the future.

The aim of this study was to determine the different soy protein concentrate (0, 15, 30, and 45%), defatted soy flour (0, 10, 20, and 30%), and wheat flour (10, 20, and 30%) contents replacing fish meal on physiochemical properties of extruded aquatic feed by using twin screw extruder. The moisture content, barrel temperature, die diameter, and screw speed were adjusted to 45%, 137°C, 4 mm, and 250 rpm, respectively. With the higher amount of soy protein concentrate replacing fish meal, the expansion ratio, swelling ratio, and water stability significantly increased while specific length and water holding capacity significantly decreased. With increasing the defatted soy flour contents, expansion ratio significantly increased, but specific length, water holding capacity and water stability significantly decreased. With increasing in the wheat flour contents, the specific length significantly decreased while the water stability significantly increased. In conclusion, high-quality aquatic feed was achieved in this study and could be used in the future.

The aim of the study was to determine physiochemical properties of extruded fish feed at different barrel temperature (120, 130, and 140°C) and moisture content (35, 40, and 45%). As barrel temperature and moisture content increased, expansion ratio, water holding capacity, and water stability increased, while bulk density, hardness, and swelling ratio decreased. Soaking time had significant (P<0.05) effect on water stability. Best water stability was observed on all samples soaked for 1 h. Protein digestibility was not significantly different among the samples while protein digestibility of extruded fish feed significant higher than raw materials.