Influence of natural colourants annatto and pumpkin powder on the physicochemical properties, antioxidant activities and sensory characteristics of Carica papaya L. juice

The processing of papaya juice alters the colour of the juice, resulting in a less visually appealing appearance. To improve the juice's visual appeal, food colouring is required. This study aimed to investigate the effects of annatto and pumpkin powders, as natural colourants, on the physicochemical properties, antioxidant activities, and sensory characteristics of papaya juice. Papaya was blanched in citric acid (0.5% w/v) at 95°C for 2 mins before blending into puree and was treated with pectinase enzyme (20 ppm) at 45℃ for 60 mins to enhance juice extraction. The juice (86.5% v/v) was added with 10% w/v sucrose and 2% w/v annatto, and pumpkin powder at different ratios (0:0 (control) (S1), 100:0 (S2), 75:25 (S3), 50:50 (S4), 25:75 (S5), 0:100 (S6)). Then, the papaya juice was analysed for pH, total soluble solids (TSS), turbidity, colour, total phenolic content (TPC), total flavonoid content (TFC), antioxidant activities (DPPH and FRAP assays) and sensory characteristics using check-all-that-applied (CATA) analysis. Higher annatto powder ratios (S2 and S3) appeared more attractive and made the TFC of papaya juice (26.20 and 23.77 mg QE/100 mL) significantly higher compared to other ratios, but resulted in a bitter aftertaste and unpleasant mouthfeel. However, higher ratios of pumpkin powder (S5 and S6) significantly reduce the TPC of papaya juice (26.48 and 28.21 mg GAE/100 mL). Higher ratios of pumpkin powder significantly increased the antioxidant activities (DPPH and FRAP) and overall acceptability scores, but the juice colour was unattractive. A combination of 50:50 ratios of annatto and pumpkin powders provided the optimal balance between attractive appearance, high antioxidant properties, and acceptable sensory characteristics. The findings of this study emphasised the importance of selecting appropriate natural colourants and ratios to improve the quality of processed fruit juices.