Cooling is one of the most important post‐processing operations in the production of extruded aquatic feed pellets. In this study, a rotary pellet cooler of simple design was manufactured, and the effect of different operating parameters on the final quality of extruded floating and sinking aquatic feed (low density 0.538 g/cm3, medium density 0.789 g/cm3 and high density 0.915 g/cm3) was investigated. The cooler parameters that were studied included air suction velocity (2.32, 3.76, 4.35 and 5.87 m/s), cooler horizontal angle (10, 15, 20 and 30°) and turning speed (5, 10, 15 and 20 rpm). Results indicated that the most effective operating range for these parameters was 3.76–4.35 m/s, 10–15 rpm and 10°, respectively, which led to a cooling efficiency of 72.8–74.5%, and good quality aquatic feed pellets with 8.3–9.1% output moisture content, 0.0% molding percentage after 2 months of storage, 0.1–0.8% losses and 0.8–1.7% unpelleted mash. PRACTICAL APPLICATIONS An effective cooling system for extruded aquatic feed pellets can significantly reduce the energy costs involved in drying for long‐term storage and also minimize product losses during postprocessing operations. Counterflow rotary coolers provide very efficient drying and separation of unpelleted mash. The counterflow rotary air cooler that was designed, manufactured and tested in this study will be very useful for small‐scale industries involved in the production of both floating and sinking aquatic feeds, and can lead to greater efficiencies and cost‐effectiveness. The cooler performance was systematically evaluated, and the results are relevant to all coolers of similar design.
Extrusion cooking has been used in industries for many years to produce various types of human foods and animal feeds. Twin screw extrusion used for the production of expanded breakfast cereal. This work aimed to develop a local single screw extruder to produce the breakfast cereal by modifying extruder die and cutter knife units. The performance of the developed extruder was studied as a function of change in the physical and mechanical factors affecting the shear in extrusion barrel such as screw speed of(354and 438 RPM) , the clearance between the last screw unit and die of (3,10 and 20mm), number of holes in the die (1,3,6 and 9 holes) as mechanical factors and formula moisture content of (19,24 and 29%w.b.) as physical factors. Results indicated that the most effective operating range for these parameters was 438 rpm, 3 mm, 6 holes and 24%w.b., respectively, which led to an extruder productivity of 253.56 kg/h, specific mechanical energy (SME) of 67kW.h/ton and good product quality with 0.716 g/cm3 product bulk density, 93.18 %durability, 1.63 expansion ratio and 41.83% cereal water absorption. FINTRODUCTION ood extrusion has been practiced for well over a century. The first major commercial application of the screw extruder to food processing was the production of pasta. This low shear, low temperature forming process found first commercial production in the 1920s and 1930s and remains a standard production process into the twenty-first century. The screw extruder was first used as a continuous cooking device in the late-'30s. Today, the extrusion cooker has become the primary continuous cooking apparatus in the commercial production of many snacks, cereals, aquatic feeds, and pet foods.
The aim of the present study was to evaluate the combined effect of the preconditioner conditions and substitution soybean meal protein with sunflower meal protein on the chemical composition of freshwater fish feeds. This experiment was conducted using Box-Behnken design with three independent variables; i) substitution of soybean meal with sunflower meal at three levels 0, 25 and 50%, ii) preconditioner temperature at three levels of 85, 95 and 105 °C, iii) preconditioner moisture (15,17.5 and 20%). There was no significant effect of manipulating the level of the three independent variables on the extrudates crude protein, crude fat, ash level and trypsin inhibitor activity. Increasing the substitution of soybean meal by sunflower meal significantly increased the extrudates dry matter and crud fiber levels. Increasing the preconditioner temperature had no negative effects on all the essential amino acids levels with exception of the threonine level, while significant increase in arginine, histidine and alanine levels of the extrudates were observed. Increasing sunflower meal inclusion had a negative significant effect on lysine and tyrosine levels and had a significant positive effect on methionine and glycine levels. These results indicate that increasing of the preconditioner temperature has a positive effect on increasing the inclusion level of sunflower meal in freshwater fish diets.
Extrusion as new technology in aquatic feed producing need to understanding the extruder advantage and parameters effect because extruder is sensitive machine ,the production and quality clearly depend on many physical and mechanical parameters, the most affecting physical factor is the feed formulation and the most affecting mechanical factors is the extruder shear properties screw profile (high or low shear) and extruder zones temperature specialist die zone temperature all this factors judging the extruder performance and product quality. The study focuses on study the effect of extruder shear, (high or low shear), die zone temperature of 105, 120, 135 and 150 C o and tow kind of feed formulations (sinking and floating formula) on extruder performance and product quality. The results reported that for producing sinking feed, the optimum parameters at using low shear screw profile and control the die zone temperature at 105C o , the obtained results were 4.911Mg/h production rate, 98.54% sinking pellets percentage, 0.56 m/s sinking velocity, 1.03 expansion ratio, 561,11kg/m3 pellets bulk density and 63% sinking pellets water stability after one hour. For producing floating fish feed the optimum parameters at using high shear screw profile and 135Co die zone temperature, the obtained results were 3.636Mg/h production rate, 97,34% floating pellets percentage, 472min pellets floating time, 1.69 expansion ratio, 383.26 kg/m3 pellets bulk density and 100% floating pellets water stability after one hour. The electronic scanning images explicated the obtained data by measuring the void cells dimensions and the gelatinization degree.
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