Conservação da polpa de açai atraves da tecnologia de obstaculos e caracterização reologica

AUTOR(ES)
DATA DE PUBLICAÇÃO

2002

RESUMO

The objective of this study was to improve the preservation process of the assai pulp through the application of obstacles technology in milder conditions that the ones applied by Carneiro (2000) and to extend the knowledge on rheological behavior of the assai pulp. In the application of the obstacles technology, the following preservation factors were used: reduction of pH the 3.5 for the addition of 0,5% w/w of citric acid, thermal treatment (82,5°C for 1 min), reduction of the water activity for the addition of sucrose (10, 25 and 40% w/w) and addition of potassium sorbate (O,0.075 and 0.15% w/w). A complete experimental planning of factorial type 22was used in the elaboration of the formulations of the product. Additionally, a control formulation, acidified and only thermally treated, was made. The formulations were conditioned in glass flasks and stored at 25°C in the absence of light for 5 months. The formulation 2 (0% of potassium sorbate and 40% of sucrose) was discarded because of mycrobiologic problems in the first month of storage. The formulation 8 (0% of potassium sorbate and 0% of sucrose) was not accepted sensorially in the first month of storage and 1 (0% potassium sorbate and 10% of sucrose) after 3 months storage. The formulations 4 (40% of sucrose and 0,15% of potassium sorbate) and 5 (25% of sucrose and 0,075% of potassium sorbate) showed a good overall acceptability shelf-life time of 5 months. In the study of the rheological behavior of the assai pulp, a controlled stress rheometer from Carri-Med CSL2 500, equipped with parallel-plate geometry of stainless steel (smooth and grooved surfaces) of 4,0 cm of diameter was used. The assays were carried through in the temperatures of 10, 25, 40, 55 and 70°C. The product showed shear-thinning behavior with yield stress and the flow curves followed the Herschel-Bulkley mode!. Thixotropic behavior was observed in ali the studied temperatures. The Arrhenius equation was used to study the effect of the temperature on the viscosity. At low shear stress, the presence of slip effects was evidenced (steady and oscillatory state). The assai pulp gave a weak gel-like response independent of the temperature. The modified Cox-Merz rule was applicable to the steady and dynamic properties data on assai pulp

ASSUNTO(S)

reologia açai

ACESSO AO ARTIGO

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