Microbiological evaluation of mechanically harvested citrus fruit

Michelle D. Danyluk, Loretta M. Friedrich, Reza Ehsani


Significant reductions in harvesting costs will be necessary in coming years for Florida to continue to compete in the international citrus industry. Two steps are involved in the mechanical harvesting (MH) of citrus fruit: removal of fruit from the tree and collection of fruit (by a catch-frame device or retrieval of fruit from the ground). This study evaluates the microbiological aspects of mechanically handled fruit with respect to fruit surface microflora and corresponding fruit juice microflora. Four replicates of mechanical harvesting were performed, including two catch-frame (CF) replicates and two pick-up machine (PU) replicates. For each replicate, three treatment groups were evaluated: 1) hand-harvested fruit (control); 2) ground fruit (picked up directly from ground following canopy shaking); and 3) mechanically harvested (MH) fruit (collected from the OXBO pick-up machine or from the goat following collection on a catch frame). Microbial analysis included a total plate count (TPC), an acidophilic organism count (OSA), and generic Escherichia coli and Salmonella testing on pooled samples of five oranges. Juice samples, from each fruit, were subjected to the same tests. The amount of sand found on the surface of fruit was measured. Hand-harvest control fruit generally had fewer microbes on the surface of the fruit than either ground or MH fruit on both TPC and OSA. Juice corresponding to the control fruit also generally had fewer microbes on both TPC and OSA than the juice corresponding to ground or MH fruit. However, no real trends can be attributed to the harvest method for all runs. Generic E. coli was detected in 10 pooled orange samples (five CF and five PU) and Salmonella spp. was not detected in any of the pooled fruit or juice samples. Sand levels on PU MH samples were significantly higher than those found on CF MH, ground, or control fruit.

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Proc. Fla. State Hort. Soc.     ISSN 0886-7283