Effect of combined processes of osmotic dehydration and freezing on papaya preservation

Abstract

The effect of combined processes of osmotic dehydration, and freezing on papaya pieces preservation was evaluated. Sucrose solutions were used as osmotic medium. Two multifactorial experimental designs, in two levels, were conducted consecutively to quantify the effect of the following factors: temperature, osmotic dehydration time, concentration of the osmotic medium and freezing rate. The response variables considered were: sensory evaluation, instrumental colour, instrumental texture, water activity (a(w)), drip loss, and reducing and total sugars. The first experimental design selected fast freezing as the best process to preserve the texture of the fruit. From the second experimental design, under fast freezing, were obtained the following optimal levels: 65degreesBx for the concentration of the osmotic medium, 20degreesC for the syrup temperature and 60 min for the osmotic dehydration time. An acceptability test was performed under these conditions with 100 potential consumers on a 7-point hedonic scale, which gave 98% acceptance. Glass transition temperature (T-g') of the maximally cryoconcentrated liquid was -33.74degreesC for the product processed under optimum conditions, which was the closest value to the common storage temperature (-18degreesC) among all the measured samples.