Multiplication of Escherichia coli DH5a::gfp on Strawberry Fruit Surface

To verify the multiplication of microorganisms on the surface of strawberries, the fate of E. coli at different temperatures, times and strawberry extract concentrations were measured. The population of E. coli rapidly increased by 7.36~7.78 log CFU/g at for 24 hr and slowly increased by 6.49~8.49 log CFU/g at for 48 hr. However, E. coli did not grow at on the surface of the strawberries, regardless of the contact times with the bacterial suspension. E. coli reached 1.52~3.26 log CFU/g at as the contact frequency increased from two to six times. The contact frequencies did not significantly differ. In the case of the six-time contact on the surface of the strawberry at 25 and , the E. coli increased by 5.17 and 5.01 log CFU/g. The effects of the strawberry extracts on the growth of E. coli showed that sterilization and non-sterilization do not affect the growth of microorganisms for 96 hr. In the minimal broth, the growth of E. coli increased by 1 log CFU/g for 96 hr. In less than 50 percent of the strawberry extracts, the growth rate of E. coli was higher than in the control and increased by 4 and 5 log CFU/g at 50 and 25 percent of strawberry extracts, respectively. Therefore, E. coli can multiply and survive on the surface of strawberries when it comes into contact with the fruit extract.