Effect of vibration on the bacterial growth on strawberry fruits

Author: Nobutaka Nakamura ^1*, Yasuhiro Inatsu ¹, Shinichi Kawamoto ¹, Hiroshi Okadome ¹, Kohei Nakano ², Shigenori Maezawa ² and Takeo Shiina ¹

Received 17 September 2006, accepted 11 December 2006.

Abstract

The effects of vibration on the growth of aerobic mesophilic bacteria and coliform bacteria, and the survival of inoculated Escherichia coli O157:H7 or Listeria monocytogenes were studied on the strawberry fruits. Post-vibrated strawberries were stored at 10°C and 25°C and the periodic microbial count was observed for 4 days. It was found that vibrated strawberries caused increase of aerobic mesophilic and/or coliform bacteria on post storage incubation at 25°C (P<0.01), while vibration treatment did not affect the growth of mesophilic bacteria, if stored at 10°C. L. monocytogenes levels on vibrated strawberries stored at 10°C and 25°C were slightly lower than that of non-vibrated strawberries, but the difference was not significant. E. coli O157:H7 level for vibrated fruits stored at 10°C showed slightly but significantly lower value than that for non-vibrated fruits (P<0.01). On the other hand, E. coli O157:H7 levels on vibrated and non-vibrated strawberries stored at 25°C increased during storage (P<0.05). The results showed that vibration caused a significant increase of bacteria on strawberry fruits stored at 25°C, but non-significant when stored at 10°C.

Key words: Strawberry, vibration, damage, storage, temperature, aerobic mesophilic bacteria, coliform bacteria, Escherichia coli O157:H7, Listeria monocytogenes.