Avaliação das características físico-químicas e sensoriais de polpa de acerola (Malphighi emarginata D.C.) submetidas a diferentes técnicas de congelamento.

Abstract

West Indian cherry pulp, submitted to three methods of initial freezing, in freezing at -22.6 °C, for circulation of nitrogen at -100 °C and for immersion in liquid nitrogen at -196 °C was stored at -22.6 °C along a period of 180 days. It was determined the kinetics of cooling and freezing of these pulps and the alterations of some characteristics physicalchemical (ascorbic acid, reducers sugars, pH, acidity, soluble solids) and sensorial (appearance, color, scent and taste), seeking to verify the effect of these treatments in the quality of the pulp. For the frozen pulp at -22.6 °C, the stages of cooling, crystallization and post-freezing were of 1800, 6000 and 6000 seconds, respectively. The average effective thermal diffusivity considering the stages 1 and 3 was 1.23 mm2.s"'. For the frozen pulp at -100 °C, those time were of approximately 360, 1140 and 3260 seconds. For the frozen pulp at -196 °C, the times of cooling, crystallization and post-freezing were of approximately 60, 30 and 140 seconds, respectively and the average effective thermal diffusivity was of 24.21 mm2.s"'. There was interference of the methods of freezing in the stability of the ascorbic acid. With the method of conventional freezing at -22.6 °C, they happened losses of 7.03 % along the storage period, while in the methods of freezing at -100 °C and -196 °C didn't happen significant losses. The levels of acidity of the acerola pulp, frozen in conventional freezer at -22.6 °C, decrease until the 90 days and then they tend to they stabilize. When frozen by the method of circulation of nitrogen at -100 °C and for immersion in liquid nitrogen at -196 °C, the acidity presents a decréscimo until the 60 days and starting from this period it tends to stabilize. The reducers sugars maintained, of a way general, stable in the acerola pulp when frozen at -22.6 °C and -100 °C, while in the method freezing at -196 °C happened a significant reduction at the end of 180 days of storage. The content of soluble solids of the acerola pulp tends to decrease when frozen at -22.6 °C, while in the treatments at -100 °C and -196 °C were shown stable starting from the 30 days of storage. There was a reduction of the pFI in the three methods of freezing along the storage period. There was not preference for appearance, scent and color among the methods of freezing, as well as there was stability for these attributes. With relationship to the taste, there was a significant decrease to the 180 days for the frizzed pulp at -196 °C.