Abstract
This study investigated the effect of freeze-drying on the nutritional composition of a watermelon–orange–mango composite fruit powder. Individual watermelon, orange and mango purees were produced and used to formulate six composite fruit blends. The formulations were subjected to sensory evaluation, and the most acceptable formulation, comprising 50% watermelon, 30% orange and 20% mango, was selected for freeze-drying. The selected composite puree was freeze-dried at an initial freezing temperature of −45 °C under vacuum, and the nutritional composition of the fresh puree and resulting freeze-dried fruit powder (FDFP) was determined. Freeze-drying reduced moisture content from 83.45 ± 3.34% in the fresh composite puree to 3.55 ± 3.34% in the FDFP. Correspondingly, measured concentrations of ash, protein, crude fibre, fat and carbohydrate increased from 0.74, 0.96, 0.74, 0.50 and 13.61% to 2.76, 4.39, 2.89, 0.78 and 85.63%, respectively. Most vitamins and all minerals analysed showed higher measured concentrations in the FDFP, although folic acid decreased from 4.10 to 0.53 mg/100 g and vitamin B12 was not detected in either sample. The concentrations of several amino acids also increased following freeze-drying, with L-citrulline increasing from 118.05 ± 3.86 to 250.01 ± 0.03 mg/100 g and arginine from 8.67 to 181.14 mg/100 g. The results indicate that freeze-drying effectively converted the high-moisture composite puree into a low-moisture fruit powder while retaining measurable nutritional constituents. However, the apparent increases in nutrient concentrations should principally be interpreted as concentration effects resulting from water removal rather than synthesis or necessarily complete nutrient retention. The findings demonstrate the potential of freeze-drying as a preservation and value-addition technology for watermelon–orange–mango composite fruit products.