Umidade da massa no extrusor sobre os parâmetros de processamento, macroestrutura, cozimento do amido e palatabilidade de alimentos extrusados para gatos.
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Data
2017-02-23
Autores
Baller, Mayara Aline
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Universidade Estadual Paulista (Unesp)
Resumo
A adição de água é uma das variáveis que otimiza o processo de extrusão, uma vez que favorece o umedecimento dos ingredientes e transferência de calor, proporcionando o cozimento adequado; ocasiona mudanças na viscosidade e nas características macroestruturais dos kibbles reduzindo o desgaste da rosca extrusora; e se adicionada em quantidades suficientes, diminui a taxa de ocorrência da reação de Maillard. Apesar de sua importância, não se localizaram estudos sobre os melhores intervalos de umidade de processamento para a produção de rações para gatos. O objetivo deste trabalho foi avaliar os efeitos da umidade da massa no canhão da extrusora sobre os parâmetros de processamento, macroestrutura dos kibbles, balanço de massa e energia, gelatinização do amido e teor de lisina reativa em alimentos extrusados para gatos. Uma fórmula padrão para gatos foi extrusada, e durante o processo de extrusão foram adicionadas seis diferentes quantidades de água no canhão extrusor, correspondendo as umidades da massa de 22%, 27%, 30%, 32%, 35% e 37% (tratamentos). O alimento foi produzido em extrusora de rosca simples e as condições de processamento foram estabilizadas para a dieta 22%, não sendo alteradas para as demais dietas. Os parâmetros registrados foram a temperatura do pré-condicionador, temperatura, pressão e produtividade da extrusora. Amostras de ração foram coletados a cada 15 minutos na saída da extrusora, sendo considerado cada coleta uma unidade experimental. A energia mecânica específica e a energia térmica específica, transferidas à massa, foram calculadas de acordo com Riaz (2007). A lisina reativa foi avaliada pelo método da O-metilisoureia (Moughan e Rutherfurd, 1996). Os dados obtidos foram submetidos à análise de variância (ANOVA) e as médias comparadas por contrastes polinomiais (P<0,05). A adição de água aumentou a umidade de processamento de forma linear (P<0,001), o que resultou em diminuição da pressão e temperatura de extrusão, redução quadrática da aplicação de energia mecânica específica (EME) (P<0,001), redução quadrática na densidade aparente e específica, e na expansão radial e longitudinal (P<0,01), sem alterar a força de ruptura e a gelatinização do amido das dietas. Houve ainda um aumento da lisina ligada, indicando maior complexação do aminoácido (P<0,001). Conclui-se que uma elevada umidade da massa no canhão leva à uma redução da EME, da temperatura, da pressão, da gelatinização do amido, explicado pelo aumento da fluidez da massa e consequente reduz do cisalhamento. Por outro lado, a baixa umidade da massa reduziu a expansão, a temperatura e o flash-off ou vaporização da água, fenômeno chave na formação celular e expansão do extrusado.
The addition of water is one of the variables that maximizes the extrusion process, since it favors the hydration of the ingredients and the heat transfer, providing a proper cooking; it also causes changes in the viscosity and macrostructural characteristics of the kibbles, reducing the wear of the extruder thread; if added in sufficient amounts it decreases the occurrence of Maillard reaction. Despite their importance, there are no studies evaluating the best processing moisture ranges for the production of cat food. The objective of this work was to evaluate the effects of the in-barrel moisture on the processing parameters, kibble macrostructure, mass and energy balance, starch gelatinization and reactive lysine content of extruded foods for cats. A standard formula for cats was extruded, and during the extrusion process six different amounts of water were added to the extruder barrel, corresponding to the moistures of22%, 27%, 30%, 32%, 35% and 37% (treatments).The feed was extruded in a single screw extruder and the processing conditions were stabilized for the 22% diet, they were not changed for the other diets. The productivity, pressure and temperatures of the conditioner and of the extruder were recorded. Feed samples were collected every 15 minutes at the end of the extruder, each sample was considered an experimental unit. The specific mechanical energy and specific thermal energy transferred to the mass were calculated according to Riaz (2007). The reactive lysine was evaluated by the O-methylisourea method (Moughan and Rutherfurd, 1996). The data were submitted to analysis of variance (ANOVA) and the means were compared by polynomial contrasts (P <0.05). Addition of water linearly increased the processing moisture (P <0.001), which resulted in a decrease in extrusion pressure and temperature, quadratic reduction of specific mechanical energy application (P <0.001), quadratic reduction in density apparent and specific, radial and longitudinal expansion (P <0.01), without altering the breaking strength and the starch gelatinization of the diets. There was also an increase in the bound lysine indicating greater amino acid complexation (P <0.001). It is concluded that an increase in in-barrel moisture leads to a reduction in the EME, the temperature, the pressure, the starch gelatinization, explained by the increase of the fluidity mass and consequent reduction of the shear. On the other hand, a low in-barrel moisture reduced expansion, a temperature and flash off, a key phenomenon in the cell formation and expansion of the extrudate.
The addition of water is one of the variables that maximizes the extrusion process, since it favors the hydration of the ingredients and the heat transfer, providing a proper cooking; it also causes changes in the viscosity and macrostructural characteristics of the kibbles, reducing the wear of the extruder thread; if added in sufficient amounts it decreases the occurrence of Maillard reaction. Despite their importance, there are no studies evaluating the best processing moisture ranges for the production of cat food. The objective of this work was to evaluate the effects of the in-barrel moisture on the processing parameters, kibble macrostructure, mass and energy balance, starch gelatinization and reactive lysine content of extruded foods for cats. A standard formula for cats was extruded, and during the extrusion process six different amounts of water were added to the extruder barrel, corresponding to the moistures of22%, 27%, 30%, 32%, 35% and 37% (treatments).The feed was extruded in a single screw extruder and the processing conditions were stabilized for the 22% diet, they were not changed for the other diets. The productivity, pressure and temperatures of the conditioner and of the extruder were recorded. Feed samples were collected every 15 minutes at the end of the extruder, each sample was considered an experimental unit. The specific mechanical energy and specific thermal energy transferred to the mass were calculated according to Riaz (2007). The reactive lysine was evaluated by the O-methylisourea method (Moughan and Rutherfurd, 1996). The data were submitted to analysis of variance (ANOVA) and the means were compared by polynomial contrasts (P <0.05). Addition of water linearly increased the processing moisture (P <0.001), which resulted in a decrease in extrusion pressure and temperature, quadratic reduction of specific mechanical energy application (P <0.001), quadratic reduction in density apparent and specific, radial and longitudinal expansion (P <0.01), without altering the breaking strength and the starch gelatinization of the diets. There was also an increase in the bound lysine indicating greater amino acid complexation (P <0.001). It is concluded that an increase in in-barrel moisture leads to a reduction in the EME, the temperature, the pressure, the starch gelatinization, explained by the increase of the fluidity mass and consequent reduction of the shear. On the other hand, a low in-barrel moisture reduced expansion, a temperature and flash off, a key phenomenon in the cell formation and expansion of the extrudate.
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Palavras-chave
energia mecânica, extrusão, gelatinização do amido, mechanical energy, extrusion, starch gelatinization