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Made available in DSpace on 2019-10-06T16:52:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-12-01 Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) Water addition is required for proper extrusion, improving dough flow, starch hydration and swelling, viscosity generation, and extrudate cellular formation. The implications of changing in-barrel moisture, however, is little studied for cat foods. Using a nutritionally balanced cat food recipe, the present study evaluated the application of six amounts of water at the extruder barrel, obtaining the following mass in-barrel moistures: 220 g/kg, 270 g/kg, 300 g/kg, 320 g/kg, 350 g/kg, and 370 g/kg. Treatments were processed in a single screw extruder; after stabilization (45 min), extrusion parameters was recorded at each 15 min, with four samplings per moisture level (considered the experimental unit). Treatments were evaluated in a sequential addition of moisture, and results submitted to variance analysis and compared by polynomial contrasts (P < 0.05). The specific mechanical energy application, temperature and pressure of extrusion, starch gelatinization, and in vitro digestibility of organic matter decreased with increasing in-barrel moisture (P < 0.01). The difference between reactive to total lysine decreased with increased in-barrel moisture, showing less lysine complexation with higher moisture contents (P < 0.05). Kibble expansion and lipid complexation showed a quadratic response (P < 0.01), with higher values for in-barrel moistures between 280 g/kg to 320 g/kg. Cat preferences to foods did not change due to water addition during extrusion. In-barrel moistures between 280 g/kg and 320 g/kg is suggested to improve extrudate formation, allow high starch gelatinization, and control mechanical energy application to the mass. Universidade Estadual Paulista (Unesp) Faculdade de Ciências Agrárias e Veterinárias Universidade Estadual Paulista (Unesp) Faculdade de Ciências Agrárias e Veterinárias

Made available in DSpace on 2018-12-11T17:37:41Z (GMT). No. of bitstreams: 0 Previous issue date: 2018-09-01 The aim of this study was to evaluate the effects of specific thermal energy (STE) application at the extrusion preconditioning stage on the processing parameters, starch gelatinization, kibble macrostructure, nutrient digestibility, feces characteristics, and palatability of a dog food formulation. Two experiments were conducted, and both used the same dog food recipe. In the first experiment, six amounts of STE were applied by changing steam infusion in the preconditioner to obtain the following discharge mass temperatures: 45 °C, 55 °C, 65 °C, 75 °C, 85 °C, and 95 °C. After evaluating the processing and kibble characteristics, the diets were fed to 36 dogs (six dogs per diet), and nutrient digestibility was determined by total feces collection. Palatability comparisons were carried out with 36 dogs using the two-pan method. Results were analyzed by analysis of variance (ANOVA), and means evaluated by polynomial contrasts according to the STE application (P < 0.05). In the second experiment, three treatments were produced. The extruder was operated with preconditioner mass temperature of 45 °C, and the amperage documented. On the sequence, the preconditioner mass temperature was increased to 95 °C, and the reduction on amperage was recorded. The extruder feed rate was them increased until a motor amperage equivalent to that of treatment 45 °C was observed but keeping constant preconditioner mass temperature at 95 °C. Processing and kibble characteristics were evaluated. Results were analyzed by ANOVA with means separated by Tukey's test (P < 0.05). In experiment one, a quadratic reduction of specific mechanical energy (SME) implementation with increasing STE was verified (P = 0.004), with a linear increase in total specific energy application to mass (P < 0.001). Regarding the relationship of starch gelatinization with increasing STE, a quadratic increase after preconditioning and a linear increase in kibbles after drying were verified (P < 0.001). Kibble expansion increased (bulk density, expansion rate, specific length), and hardness decreased with increasing STE (P < 0.001). Apparent nutrient digestibility and food palatability did not change according to STE application. Feces dry matter increased (P = 0.003), but pH and fermentation product content did not change. In experiment two, increasing STE was able to substantially elevate the mass production of the extrusion system while keeping the electric energy consumption constant. In conclusion, an increase in STE application decreased the SME required to process the food and increased the kibble expansion, starch gelatinization and in vitro digestibility of organic matter (OM), allowing a substantial increase in extruder productivity without increasing electric energy consumption, an important economic consideration for dog food production efficiency. Universidade Estadual Paulista (UNESP) Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal Universidade Estadual Paulista (UNESP) Faculdade de Ciências Agrárias e Veterinárias, Jaboticabal