Efeito das condições de processo na cinetica de secagem de cogumelo (Agaricus blazei). / Effect of process conditions on drying kinetics of mushrooms (Agaricus blazei).

AUTOR(ES)
DATA DE PUBLICAÇÃO

2005

RESUMO

The present work had as objective to study the drying of mushroom Agaricus blazei with and without osmotic dehydration in a fixed bed dryer. The osmotic treatment was carried out at 20ºC with 10% w/w salt solution, agitation of 80 rpm, temperature of 20°C and processing time of 60 minutes. The isotherms were obtained for three different temperatures (40, 60 and 80°C) using the static method with saturated salt solutions. Experimental data were fitted by several models (BET, GAB, Halsey, Henderson, modified Henderson. Chung-Pfost and Oswin). The best fitting was obtained when the traditional and modified Henderson models were used. For the drying experiments, carried out at various air temperature (40 to 80°C) and air velocity (1,0 to 2,5 m/s), a screening design was applied to evaluated the influence of temperature and air velocity on the responses drying constant of the exponential model and total color difference between dried and fresh samples. The experimental data of drying kinetics were fitted using diffusional model, considering no shrinkage, exponential and Page?s model. The obtained effective diffusivity were 3,84 x 10-10 to 16,80 x 10-10 m2/s for the in nature mushroom and of 5,38 x 10-10 to 15,08 x 10-10 m2/s for the osmotic dehydrated mushroom. The Page?s model presented better fitting in relation to the others model used. The experimental data also presented a good fitting to the exponential model, in the which the drying constant varied from 2,02 x 10-4 to 8,06 x 10-4 s-1 for the in nature mushroom and of 2,78 x 10-4 to 7,25 x 10-4 s-1 for the osmotic dehydrated mushroom. Through the Response Surface Methodology, it was chosen a condition to obtain the largest values drying constant and smallest values color difference. Like this, in the optimized conditions of the process (70°C and 2,0 m/s, and 80°C and 2,5 m/s for the samples without and with osmotic treatment, respectively), it was made a characterization of the dried products, evaluating the B-glucan content, water activity and rehydration properties.

ASSUNTO(S)

quality osmotic dehydration desidratação osmotica secagem mushrooms qualidade cogumelos drying

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