Changes in pH and colour of watermelon juice during ohmic heating

Athmaselvi, K. A.; Ishita, C.

Changes in pH and colour of watermelon juice during ohmic heating

2017

Athmaselvi, K. A. | Ishita, C.

Watermelon is a highly perishable fruit with a niche for majority of microrganisms. Itcomprises of 91% water and hence it is very difficult to preserve watermelon based products byapplication of conventional means. Ohmic heating, also known as Joule heating is an electrothermaltechnique of processing. In this study, the effect of ohmic heating on the electricalconductivity, pH and colour of the watermelon juice at various voltage gradients (10-23.33V/cm) was investigated. The change in the pH and colour of the watermelon juice during storagewas studied. The bubbling of juice was observed above 60°C at all voltage gradients. As thevoltage gradient increased the time required to reach the desired temperature decreased. Theelectrical conductivity was observed to increase with increase in temperature. Linear modelgave the best fit to the electrical conductivity of watermelon juice. The change in pH andcolour has increased with increase in voltage gradient, ohmic heating time and storage period.Ohmic heated watermelon juice showed better retention of physicochemical properties whencompared to conventional heating.

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