Production and evaluation of the physicochemical and antioxidant properties of fruit jam from star fruit, hog plum and black plum

Tropical fruits such as black plum, star fruit, and hog plum are excellent sources of phytochemicals which are essential for human health but the back drop of these fruits is their perishability, leading to tones of postharvest losses. To address these concerns, these fruits could be utilized in jam processing to further extend their shelf lives. This research work on production and quality evaluation of mixed-fruit jam produced from star fruit, hog plum, and black plum using mixture experimental design of response surface methodology was undertaken to improve the utilization of these underutilized fruits in jam processing. The produced mixed fruit jams were assessed for physicochemical and antioxidant properties using standard methods. Statistical analysis and optimization of mixture variables were carried out using Design-Expert software version 6.0.8 while means were separated using ANOVA and significance accepted for p≤0.05 using Duncan ranged multivariate test using the IBM SPSS Statistics software version 22. Result of analysis for physicochemical properties showed that pH of the fruit jams ranged from 3.41 to 4.46, titratable acidity 0.33 to 0.48 %, total solids 44.35 to 75.07 %, while the range of 53.22–74.65°Brix was recorded for total sugar and 19.94 to 25.64 mPas for viscosity. Antioxidant properties of the fruit jams ranged from 310.34 to 471.57 mg/ml for DPPH and ranged from 526.64 to 650.26 mmol.AAE/g for FRAP. The result of mixture variable optimization showed that optimal responses, jam should be produced from fruit combination comprising 8.43 %-star fruit, 91.57 % black plum and 0 % hog plum with 60 % desirability or experimental run comprising 5.08 %-star fruit, 90.39 % hog plum and 4.53 % black plum with 58 % desirability