Impact of thermal pasteurization by retort technology on the quality and safety of red dragon fruit (Hylocereus polyrhizus) juice during refrigerated storage

Abstract

This study evaluates the quality and safety of red dragon fruit (Hylocereus polyrhizus) juice processed using retort pasteurization (90 °C for 5 minutes) and stored under refrigeration for two months. Quality parameters, including betacyanin content, total phenolic content (TPC), total flavonoid content (TFC), DPPH radical scavenging activity, total soluble solids (TSS), and pH, were analyzed alongside microbial safety assessments. Retort pasteurization effectively preserved juice quality, retaining 91.9% of betacyanins, 90.82% of TPC, and 95.19% of DPPH radical scavenging activity immediately after pasteurization. During storage, 81.9% of betacyanins, 98.61% of TPC, and 80.19% of DPPH activity were maintained after two months. Although pasteurization caused a slight reduction in betacyanin content and a significant decrease in TPC due to heat-induced oxidation, TFC increased post-treatment. TSS levels declined due to sugar depletion and Maillard reactions, while pH remained stable. Microbial analysis revealed no mesophilic bacterial growth for 20 days, no psychrophilic growth throughout storage, and minimal yeast and mold growth by the end of the storage period. These findings demonstrate that retort pasteurization effectively extends the shelf life of dragon fruit juice while preserving its quality and antioxidant properties. However, additional control measures are recommended to further prevent yeast and mold growth during extended storage.