Impact of Thermal, Ultrasonication, and Thermosonication Processes on the Quality Profile of Watermelon-Beetroot Juice Blend: A Comparative Study

Fruit juices are popular beverages that provide various health benefits due to their rich nutritional profile, but they are prone to microbial spoilage and quality deterioration. Thermal pasteurization is the conventional method to preserve fruit juices, but it causes undesirable changes in the physicochemical and nutritional value of the juices. Therefore, there is a need to develop alternative methods to ensure the microbial safety and quality of fruit juices. The aim of this study was to investigate the impact of thermal (95-100°C for 4 min), ultrasonication (US) (25 kHz for 5 and 10 min), and thermosonication (TS) (25 kHz at 40 and 50°C) processes on the quality profile of watermelon-beetroot juice blend, a novel juice formulation with enhanced nutritional and functional properties with 50 : 50 formulation. The samples were analysed for physicochemical (colour, pH, total soluble solids, and titratable acidity), bioactive (phenolic, flavonoid, antioxidant, and ascorbic acid contents), and microbiological (total plate count and yeast/molds) properties. The results showed that all the processed samples retained high total phenolic (756.33-842.33 μg GAE/g), total flavonoid (435.33-512.67 μg CE/g), and ascorbic acid (45.23-50.34 mg/100 mL) contents along with a high antioxidant potential (total antioxidant capacity (274.14-305.33 μg AAE/g) and DPPH radical scavenging activity (33.05-42.18%)) while preserving the normal physicochemical characteristics and decreasing the microbial counts of all the processed blend juices. In conclusion, the US treatment (10 min) produced the juice blends with the best quality. The findings of this research suggest that thermal, US, and TS processes are promising technologies for the preservation of fruit juices and that watermelon-beetroot juice blend is a novel juice formulation with high nutritional and functional value. The results of this research might be useful to the processed fruit juice industry and the consumers who are looking for healthy and safe fruit juices.