Potential Sources of Microbial Contamination of Satsuma Mandarin Fruit in Japan, from Production through Packing Shed

Abstract

Potential sources of microbial contamination of satsuma mandarin fruit were investigated from production through the packing shed in the 2005 season. Microbial counts in the peel and flesh during the fruit development stage were below 2.4 log CFU/g for bacteria and 3 log CFU/g for fungi, except for the peel in August and September. In the field environment, the highest microbial counts were found in fallen leaves on the ground, followed by soil, organic fertilizer, and agricultural water. Only the pesticide solution collected in July was positive for Salmonella, while no verotoxin-producing Escherichia coli was detected from any of the samples. The bacterial and mold flora in the peel comprised phytopathogenic organisms such as bacteria genus Pantoea and mold genus Mycosphaerella and soilborne organisms such as bacteria genus Bacillus and mold genus Cladosporium, which were found in soil, fallen leaves, agricultural water, and cloth mulch throughout the production season. After fruit harvest and sorting, microbial counts of the peel increased, while those of the flesh remained below the lower limit of detection. Although some of the preharvest sources could also be postharvest sources, some packing shed equipment was assumed to be postharvest sources, because Bacillus cereus was not identified from the fruit in the production field but was detected on the peel after sorting and on equipment such as gloves, plastic harvest basket, and size sorter. These results suggest that using sanitizers for agricultural water and packing sheds to prevent cross-contamination would be useful in a good agricultural practices program of the satsuma mandarin in Japan.