Foam Mat Drying of Soursop Pulp: Evaluation of Phytochemicals and Physico-chemical Properties of Powder Obtained

Foam mat drying (FMD) was employed to dry soursop pulp, with the objective of assessing the powder quality parameters. Egg albumen was applied at 3%, 6%, 9%, 12%, and 15% wt/wt and methylcellulose at 0.4%, 0.8%, 1.2%, 1.6%, and 2% wt/wt as foaming and stabilizing agents, respectively. The samples were air-dried at different temperatures of 55, 60, 65, 70, and 75°C. The experimental design was determined using central composite. Physicochemical properties of the powders [hygroscopicity, bulk density (BD), pH, water absorption capacity (WAC), total soluble solids (TSS) and color], were evaluated. Additionally, qualitative analysis of the phytochemicals present, such as tannins, alkaloids, saponins, flavonoids, and anthocyanins, was conducted. Phytochemical analysis revealed the presence of tannins, alkaloids, saponins, and flavonoids in soursop powder; anthocyanins were detected at selected drying temperatures indicating their retention under certain drying conditions. Identification of these phytochemicals is important for their potential application in functional foods. pH value ranged from 4.5 to 5.3, and TSS ranged from 3.9 to 6.95 brix. Hygroscopicity increased with increasing methylcellulose content, whereas the color parameters (L*, a*, and b*) were affected by the drying temperature, leading to discoloration during the process. BD, WAC, color, and wettability were significantly affected by drying temperature (p < 0.05). Based on these data, FMD may be considered a viable method for dehydrating soursop pulp; the resulting powder can be readily reconstituted for food formulations. Thus, soursop powder has significant potential for the development of functional foods.