ABSTRACT
Freshly harvested watermelon is extremely perishable due to its high moisture content, rate of metabolism and easy discolouration due to enzymatic actions; hence the need for preservation. This study was aimed at determining the microbiological analysis of watermelon juice preserved with sodium metabisulphite and pasteurization. Samples of watermelon fruits were obtained from New-Benin market in Benin City, Edo State, Nigeria. Sodium metabisulphite was added to the juice as a preservative at a ratio of 0.0, 0.05, 0.10, and 0.20 mg/L. Effect of pasteurization at 60 °C and 70 °C on the juice with metabisulphite potential was carried out. At every 24 hours interval, microbial analysis, pH, temperature, brix, vitamin C concentration and sensory evaluation were carried out. The results revealed that heterotrophic bacterial count of sodium metabisulphite preserved watermelon juice ranged from 1.33±0.61 to 21.66±2.33 Cfu/mL×102 , Staphylococcus count (1.00±0.40 to 16.33±0.65 Cfu/mL×101 ), Escherichia coil count (0.00±0.00 to 15.00±0.46 Cfu/mL×101 ) and fungal count (0.66±4.97 to 20.33±3.01 Cfu/mL×102 ), compared to the control which ranged from 15.00±1.24 to 94.33±1.10 Cfu/mL respectively. Also heterotrophic bacterial count of pasteurized watermelon juice ranged from 8.33±2.24 to 27.00±1.41 Cfu/mL×102 , Staphylococcus count (0.00±0.00 to 10.66±2.58 Cfu/mL×101 ), Escherichia coil count (0.00±0.00 to 8.00±0.19 Cfu/mL×101 ) and fungi count (2.15±0.40 to 10.00±0.00 Cfu/mL×102 ) compared to the control which ranged from 45.00±0.00 to 99.33±3.40 Cfu/mL respectively. Bacteria isolated from sodium metabisuphlite preserved watermelon juice were Staphylococcus sp., Citrobacter sp., Bacillus sp., Eschericia coli, Pseudomonas sp. and Staphylococcus aureus. While fungi isolated from sodium metabisulfite preserved watermelon juice and pasteurization method were Penicillium italicum, Fusarium spp., Saccharomyces cerevisiae, and Aspergillus niger. Hence, from the results of this study, it can be concluded that pasteurized watermelon juice with 70 °C and 0.2 mg/L of sodium metabisulphite preserved watermelon juice were found most acceptable in sensory after 5 days storage.
