Efeito de algumas variaveis operacionais nas caracteristicas de qualidade de arroz parboilizado convencionalmente e por microondas

AUTOR(ES)
DATA DE PUBLICAÇÃO

1984

RESUMO

In this project, the effects of some operational parameters of the conventional and microwave parboiling process on the technological characteristics of yield, color and cooking time of parboiled rice were investigated. For the conventional process the parameters studied were soaking temperature, grain moisture content after soaking, concentration of sodium acetate in the soaking water and drying temperature. Grain moisture content after soaking, soaking temperature and radiation time were the parameters studied for the microwave parboiling process. The relation between the processing parameters (independent variables) and the technological characteristics (response) of the product, were determined by mathematical models obtained with the Response Surface Methodology . The products obtained using the better conditions of the conventional and microwave processes were compared with brown and polished rice with respect to their yield and chemical composition. The analysis of variance of the mathematical models that related the response with the variables independents of the conventional parboiling process, demonstrated that these models were well fitted. The yield of whole grains was mainly affected by the drying temperature and by water absorption. The other independent variables: temperature of soaking and concentration of sodium acetate, did not have a significant influence on these technological characteristics. Increasing the water absorption caused increases in the milling yield, independent of the drying temperature. On the other hand, decreasing the drying temperature caused increases in the milling yield, for the same water absorption. X-ray diffraction studies shoved that milling yield was affected by the extension of gelatinization during cooking. For the microwave process the milling yield was influenced by water absorption, soaking temperature and radiation time high milling yields being obtained with radiation times of 4 and 8 minutes, increasing the radiation time caused an increase in the area, with high yields. The effects of water absorption was limited by the soaking temperature. At elevated water absorption values, the yield was high when the soaking temperature was lower than 52.00ºC for 4 minutes of radiation, or lower than 60.0°C for 6 minutes of radiation. With 8 minutes of radiation the increase in water absorption caused an increase in milling yield, independent of the soaking temperature. In the conventional parboiling process, the cooking time was affected by the drying temperature and water absorption. Increasing these variables caused a decrease in the cooking time. The lowest cooking times were obtained between 31.00-32.00% of water absorption and a drying temperature of 80.0°G. The X-ray diffractograms of parboiled rices dried at 80.0ºC had peaks less resolved than those dried at 40.0ºC, which indicated a decrease in the intensity of the rétrogradation at high drying temperatures, which resulted in low cooking times. The cooking time for parboiling rice by the microwave process was influenced by the radiation time, soaking temperature and water absorption. Increasing the radiation time caused a decrease in the cooking time. The lowest cooking time with 4 minutes of radiation was obtained with a water absorption of above 30.00% and soaking temperatures below 45.0°C, For 6 minutes of radiation the lowest cooking time was obtained with a water absorption below 30.00% and soaking temperatures below 65.0°C. The lowest cooking time for 8 minutes of radiation was obtained with water absorption values below 29.80% and soaking temperatures above 68.0°C. The color of the parboiled rice for the conventional process was affected by the drying temperature and water absorption. Drying temperatures of 40.0°C and water absorption of 29,00% showed lower color values (D.E.) than those obtained at 8O.ºC and 35.00 - 32.00%. The color of parboiled rice obtained by the microwave process was mainly affected by the soaking temperature and water absorption. The radiation time had little influence on this characteristic of the parboiled rice. In general a white color similar to polished rice was obtained with decreases in the soaking temperature and water absorption. These were no significant differences between the protein and fiber contents of the polished rice’s and those of the parbailed rices obtained by the conventional and microwave processes. The parboilinq process causes an increase in the ash, fat, thiairin, riboflavin and niacin contents. Parboiled rices by the microwave process had the highest levels of ash, fat and vitamins.

ASSUNTO(S)

arroz - secagem

ACESSO AO ARTIGO

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