Effect of Freeze-Drying on the Phytochemical, Microbiological and Sensory Quality of Watermelon–Orange–Mango Composite Fruit Powder

Abstract

Tropical fruits are highly nutritious but highly perishable because of their high moisture content, leading to substantial postharvest losses in developing countries. This study evaluated the effect of freeze-drying on the phytochemical, microbiological, and sensory quality of watermelon–orange–mango composite fruit powder produced from locally available fruits in Nigeria. Individual purees of watermelon (Citrullus lanatus), orange (Citrus sinensis), and mango (Mangifera indica) were prepared and formulated into six composite blends. Sensory evaluation using a 9-point hedonic scale identified the blend containing 50% watermelon, 30% orange, and 20% mango (sample 618) as the most acceptable, and it was selected for freeze-drying at −45°C under vacuum to a residual moisture content of approximately 2–3%.Freeze-drying significantly (p<0.05) affected the phytochemical composition of the composite fruit powder. Total phenols increased from 251.76 to 261.76 mg/100 g, flavonoids from 26.07 to 36.07 mg/100 g, tannins from 32.54 to 42.54 mg/100 g, phytosterols from 20.77 to 30.77 mg/100 g, and terpenes from 5.79 to 15.79 mg/100 g. In contrast, lycopene and β-carotene decreased from 12.48 to 7.13 mg/100 g and from 42.76 to 21.32 mg/100 g, respectively, indicating partial degradation of carotenoid compounds during processing. The freeze-dried powder maintained good microbiological quality throughout three months of storage, with low total bacterial, Enterobacteriaceae, and yeast counts, while Salmonella/Shigella remained undetectable. Sensory evaluation showed that freeze-drying preserved desirable appearance, aroma, taste, texture, and consistency, resulting in a higher overall acceptability score (7.72) than the fresh composite puree (7.20).The findings demonstrate that freeze-drying is an effective preservation technology for producing shelf-stable composite fruit powder with good phytochemical retention, microbiological safety, and consumer acceptability for functional food formulations and reduced postharvest losses.