Frozen Soursop Puree

Abstract

The effect of the processing temperature, of the addition of sugar to 45° and 59° Brix and of the addition of four levels of ascorbic acid, 0.5, 0.75, 1.0, and 1.5 g. per pound, on the quality, shelf-life, and ascorbic acid retention of frozen soursop pulp was investigated. When unsweetened soursop pulps were processed at temperatures ranging from 74° to 200° F., no appreciable change in organoleptic properties were observed during a period of storage at —10° F. for over 400 days, in the pulps heated below 200° F. The pulp heated to 200° F. was found inferior to the others. No change in chemical composition or color was observed. The data for the ascorbic acid retention during storage do not show any definite trend which could be related to a temperature effect. Ascorbic acid retention varied from 70.8 to 94.3 percent. Pulps with cane sugar added to 45° to 59° Brix, respectively, and heated to temperatures ranging from 72° to 225° F. behaved like the unsweetened pulps when stored at —10° F. for about 400 days. No change in total acidity, pH, total and reducing-sugar content, or color was observed during the storage period. In the samples sweetened to 45° Brix, ascorbic retention values ranged from 98.18 to 133.9 percent. The retention of ascorbic acid in the 59° Brix pulps ranged from 75.0 to 91.7 percent, with the lower retention found in the sample processed at 225° F. Neither heating to different temperatures nor the addition of two levels of sugar were found to affect the shelf-life. Pulps processed at 175° F. and enriched by the addition of 0.5, 0.75, 1.0, and 1.5 g. of ascorbic acid per pound retained their flavor very well during the storage period showing less change in the organoleptic rating than the unriched sweetened and unsweetened pulps. The level of ascorbic acid had no effect on shelf-life or sample quality. Ascorbic acid retention ranged from 94.1 to 104.6 percent. No change in other chemical constituents or color were observed during the period of observation. Heating of the pulps reduced the plate counts of microorganisms. When the pulps were heated to about 175° F., almost sterile packs were obtained. Peroxidases were inactivated at 150° F. in the unsweetened pulps and at 185° F. in the sweetened. The results of this work indicate that two types of products can be prepared from soursop pulp: 1, A frozen pulp without sugar added, to be used for the manufacture of nectars, drinks, ice creams, and other similar products; and 2, a nectar base for direct consumer use prepared by the addition of sugar to 45° or 59° Brix which can be reconstituted for serving by the addition of 3 volumes of water. The addition of ascorbic acid to the nectar base would improve the shelf-life and the resulting product would have a vitamin C content higher than that contained in orange juice.