PERTANIKA JOURNAL OF TROPICAL AGRICULTURAL SCIENCE

This study examines the effects of different pasteurisation temperatures and times on red dragon fruit juice's microbiological quality, physicochemical properties, and vitamin C content. Microbial analysis used the spread plate technique to determine total plate count (TPC) and yeast and mould count (YMC). Physicochemical properties were assessed through pH, titratable acidity (TA), colour, and total soluble solids (TSS). Vitamin C content was measured using iodometric titration. Pasteurisation at 80°C for 60 s achieved the lowest TPC (3.56 log CFU/mL) compared to 6 log CFU/mL in unpasteurised juice. All pasteurised samples showed YMC below 2 log CFU/mL, demonstrating effective microbial control. However, no significant differences (p > 0.05) were observed in TPC between 60°C and 80°C. Pasteurisation caused only slight changes in pH and TSS, with higher temperature (80°C) resulting in lighter juice colour, indicating potential pigment breakdown. Vitamin C, being heat-sensitive, decreased significantly as temperature and time increased, with a maximum reduction of 30.82 mg/100 mL at 80°C for 60 s. During 28 days of storage at 4°C, juice pasteurised at 60°C for 60 s maintained microbial loads within acceptable limits. TA increased slightly, and pH levels shifted from 5.05 to 4.98. TSS remained stable, while colour difference (ΔE) increased, indicating noticeable changes. Low-temperature pasteurisation (60°C for 60 s) resulted in minimal vitamin C loss (9.36%) compared to 80°C (17.59%). In conclusion, pasteurising at 60°C for 60 s effectively balances microbial quality, physicochemical properties, and vitamin C preservation.