Efeito do processo de desidratação osmótica a pulso de vácuo na transferência de massa e nas propriedades reológicas e de cor de fatias de manga

Abstract

O presente trabalho teve como objetivo estudar as propriedades reológicas, de cor e a cinética do processo de desidratação osmótica, a pulso de vácuo, de fatias de manga. As fatias de manga foram imersas em soluções hipertônicas de sacarose, nas concentrações de 45, 55 e 65 °Brix com temperatura controlada (20 e 30 °C). No início do processo, aplicou-se ou não um pulso de vácuo, utilizando as pressões de 50 e 100 mbar por 10 minutos. As frutas foram desidratadas por 5 horas, sendo avaliadas em diferentes tempos em relação à perda de peso, perda de água, ganho de sólidos, a w , cor e propriedades reológicas Abstract The aim of this work was to study rheological and colour properties and process kinetics of mango slices subject to pulsed vacuum osmotic dehydration. The slices were immersed in osmotic sucrose solutions (45, 55 and 65 °Brix) at 20 or 30 °C. At the beginning, a sub-atmospheric pressure was applied or not to the solid-liquid system (50 or 100 mbar of pressure) for 10 minutes followed by an atmospheric pressure operation up to 5 hours. Fruit samples were evaluated after pre-determined times in terms of weight loss, water loss, solids gain, a w , colour and rheological properties (stress and strain at rupture). The concentration and temperature increases lead to a weight and water reduction. Solid gain was favoured by lower concentration and a higher temperature and by the pulsed vacuum application. The sample softening, which is characterized by a reduction of maximum stress at rupture, and the increased stress on strain at rupture ocurred at the great solids updake conditions. The colour parameters did not change during the dehydration process.