Enhancing bioactive compounds retention in pomegranate juice powder through foam mat drying

The effect of addition of whey protein isolate (WPI; 0%, 5%, 7.5% and 10%) and carboxy methyl cellulose (CMC; 0%, 0.25%, 0.5% and 0.75%) was studied for its foaming properties and stability in pomegranate juice (PJ). High-quality powders can be produced from fruit juices and heat-sensitive food items using foam mat drying (FMD). The PJ foam with 10% WPI, a foaming agent, and 0.25% CMC, a stabilizer had high foam expansion (FE) (455.28%) and low foam density (FD) (0.2030 g/cc) and foam drainage volume (FDV) (20.10 mL). The PJ foam was subjected to different drying temperatures (50, 60 and 70°C) and thickness (3 and 6 mm). The drying temperature of 60°C and foam thickness of 3 mm were found to be the acceptable drying conditions based on drying time (180 min) and retention of bioactive compounds. At optimum drying conditions, the retention of phenols, anthocyanin, ascorbic acid, and antioxidant capacity was 97.86%, 83.90%, 77.29%, and 87.11%, respectively. The sensory evaluation of the reconstituted foam mat dried pomegranate juice powder (FPJP) showed lower overall acceptability scores than fresh juice (FJ), but the overall acceptability of the powder dried at optimum drying conditions was within liking limits (>6). FPJP has an amorphous nature with a particle size of 3564 nm and a porous and irregular structure. Bioactive compounds in FPJP were studied after 8 months of storage, with higher retention of bioactive compounds in refrigerated conditions.

Practical application

The studies revealed that foam mat drying is suitable for the pomegranate juice which has high moisture and sugar content. It requires shorter drying time of 180 min. for drying up to moisture content of 4% (db). The foam mat dried juice powder obtained at optimum drying conditions has retained higher bioactive compounds and has higher sensorial acceptability when compared with the other treatment combinations. This drying process requires low initial investment and can easily be scaled up to the commercial level thus making it profitable business venture. Further, higher storage stability up to 8 months, low volume and consequent low transport cost improves the technical and financial viability of the process in industrial application. The Foam mat dried pomegranate juice developed can be used in many food products such as reconstituted beverages, ice creams, confectioneries, etc.