Effect of irradiation on microorganisms in strawberries

Seventeen samples of strawberries from seven different growers were analysed for total counts, Enterobacteriaceae, fluorescent pseudomonads and yeast and mould counts before and after irradiation at 1.2 or 2 kGy. Enterobacteriaceae were absent (less than 5 cfu/g) from all irradiated strawberries but were always detected at counts of greater than 30 cfu/g in untreated samples. This criterion was true for both fresh and stored (5 days at 8 degrees C) strawberries. Assuming no other sanitizing treatment, the Enterobacteriaceae count appears to be suitable for differentiating between irradiated and non-irradiated strawberries. The other counts used in this study were not suitable for this purpose. Isolates from irradiated strawberries could be classified into four types based on colony morphology. Three types consisted of aerobic spore-forming bacteria whilst the fourth group consisted of yeasts.