Estimation of Shelf Life of Mango Juice Produced Using Small-Scale Processing Techniques

摘要

The objective of this study was to estimate shelf life of mango juice produced using small-scale processing techniques. Juice was processed and packaged in 80 plastic bottles and stored at 13 oC and 30 oC. At each temperature, 20 bottles had preservative (0.5 mg/l sodium benzoate) and 20 bottles had no preservative. The juices were analyzed for pH, vitamin C, sensory attributes and microbial load at two week intervals for six weeks. From week 2 to week 6, juices stored at 30 oC had lower pH values (3.15 – 2.80 with preservative, 3.60 – 2.6 without preservative) than juices stored at 13 oC (4.20 - 3.80 with preservative, 4.15 - 3.70 without preservative ) and the differences were significant (p0.05). At 6 weeks, vitamin C loss was highest (79%) in juice without preservative stored at 30 oC, followed by juice stored at 30 oC with preservative (71.43%). The loss was lowest (26.98%) in juice with preservative stored at 13 oC. Significant differences (p0.05) in color were observed at week 6 between juices stored at 13 oC (4.5 with preservative and 4.66 without preservative) and 30 oC (5.02 with preservative and 7.00 without preservative). Juices stored at 30 oC were rated ‘bad’ from week 2, in smell (5.91 and 6.25) and taste (5.66 and 6.91) while at that time, juices stored at 13 oC were rated ‘almost similar’ to fresh juice in smell (4.25) and taste (4.25 and 4.58). Storage at 13 oC with preservative resulted in lowest bacteria (2.04 x 104 CFU/ml) and yeast and mold (1.72 x 104 CFU/ml) counts whilst highest bacteria (2.10 x 108 CFU/ml) and yeast and mold (1.96 x 108 CFU/ml) counts were observed in juices stored at 30 oC without preservative. The shelf life was estimated based on taste and smell as 2 weeks and 4 weeks for juices stored at 30 oC and 13 oC, respectively. Chilling combined with use of preservative slowed down rate of vitamin C loss, deterioration of sensory attributes and microbial growth.