Abstract:

To figure out the relationship between ultra-high pressure homogenization (UHPH) treatment and survival of microorganisms, watermelon juice was homogenized under pressures ranging from 0 to 150 MPa and its microbiological indexes were examined. After homogenization at 150 MPa , the total bacterial count (TBC) of watermelon juice decreased by 2.0 to 2.3 logarithm unites, and the total yeast and mold count decreased by 3.1 to 3.5 logarithm unites, but the Bacillaceae count changed little. After once homogenization at 150 MPa , watermelon juice with an initial TBC of 1.0×104 CFU/mL could meet the requirements of the national food hygienic standards, and the overall sensory evaluation was similar to that of freshly squeezed watermelon juice. Although watermelon juice with a higher initial TBC after repeated UHPH treatment could also meet the requirements of the national food hygienic standards, its overall sensory evaluation exhibited a decrease.

Key words: watermelon juice, ultra-high pressure homogenization, sterilization, total bacterial count, total yeast and mold count, coliform bacteria