Effect of spray drying on bioactive and volatile compounds in soursop (Annona muricata) fruit pulp

Soursop is seasonal and highly perishable fruit, which limits its commercialization. Thus it is necessary to conserve its pulp so that it is available throughout the year. One of the most common forms of fruit preservation is by dehydration. This work had an objective to dehydrate soursop pulp by spray drying at optimum conditions and to analyze the retention of bioactive and volatile compounds in soursop powder, besides analyzing its antioxidant capacity. The total phenolics, carotenoids and flavonoids contents were determined, while volatile compounds were analyzed by Stir Bar Sorptive Extraction (SBSE) coupled with GC-MS system. The total content of the phenolic compounds and flavonoids in the fresh pulp were 160.28 mg of GAE/100 g and 87.17 mg of quercetin/100 g, respectively while for rehydrated dried powder their values were 158.95 mg of GAE/100 g and 85.17 mg of quercetin/100 g, respectively. The total phenolic compounds, flavonoids and antioxidant capacity did not show any significant difference (p < .05) between the fresh fruit pulp and dehydrated powder. A total of 85 volatile compounds were identified, of which 33 were esters, representing the major class of organic compounds, 15 were terpenes, 10 aldehydes, 7 acids, 5 alcohols, 5 lactones, 3 ketones, and 6 other compounds. Of the total 85 compounds, identified in soursop pulp, 58 compounds were identified in the rehydrated dried powder. The principal compounds for both samples were methyl (E)-2-hexenoate, methyl hexanoate and methyl (E)-2-butanoate, which contribute to soursop aroma according to their Odor Active Values (OAV). Considering that there was no significant difference (p < .05) between fresh pulp and the rehydrated dried powder in concentrations of bioactive compounds and even with the reduction in the concentration of the main volatile compounds while the OAVs of these compounds were relatively high, it is concluded that spray dried powder of soursop pulp retains its nutritional and aroma quality, besides maintaining the antioxidant capacity.