Influence of mechanical harvesting system and abscission agent on microflora of citrus fruit
For Florida to continue to compete effectively in the citrus industry, significant reductions in harvesting costs will be necessary. Mechanical harvesting (MH), a possible means of cost reduction, can be thought of as a two-step process: 1) removal of fruit from the tree, and 2) collection of fruit (immediately by a catch-frame device, or by retrieval of fruit from the ground). This study evaluated the microbiology of the surface and juice of citrus fruit collected by various mechanical harvesting systems (OXBO 3220 or OXBO 3210) and with or without the application of the abscission compound 5-chloro-3-methyl-4-nitro-pyrazole (CMNP). Samples included fruit harvested by the following methods: 1) hand-harvested fruit (control); 2) ground fruit (picked up directly from ground following canopy shaking); and 3) mechanically-harvested (MH) fruit (collected from a catch frame), or any of these groups sprayed with CMNP. Microbial analysis included a total plate count (TPC), an acidophilic organisms count (OSA), a thermophillic aciduric bacillus count (TAB) and generic Escherichia coli and Salmonella testing on pooled samples of five oranges. Juice samples were subjected to the same tests, with the exception of TAB. Control fruit generally had fewer microbes on the surface of the fruit and in the juice than either ground or MH fruit on both TPC and OSA. TAB were rarely detected. Application of CMNP did not significantly alter microflora. However, no real trends can be attributed to harvest method for all runs. Generic E. coli was detected in ground, MH and control pooled fruit, and Salmonella spp. was not detected in any of the pooled fruit or juice samples. These results suggest that fruit which come in contact with the ground, catch-frame or CMNP are not consistently or significantly higher in surface or corresponding juice microflora than the hand harvested control.