Reduction of microorganisms on citrus fruit surfaces during packinghouse processing

Area of Science:

• Food Microbiology
• Agricultural Science
• Food Safety

Background:

• Citrus fruits harbor microbial populations on their surfaces.
• Packinghouse operations are critical control points for ensuring fruit safety.
• Understanding microbial reduction during processing is essential for food safety.

Purpose of the Study:

• To evaluate the impact of commercial citrus packinghouse processes on surface microbial populations.
• To quantify the reduction of specific microorganisms like coliforms and Escherichia coli.
• To assess the efficacy of washing and waxing treatments.

Main Methods:

• Sampling of citrus fruits (oranges, tangerines) at four points in seven commercial packinghouses.
• Microbial analysis including aerobic plate counts, yeast and mold counts, and coliform enumeration.
• Inoculation study using Escherichia coli to evaluate washing and waxing efficacy.

Main Results:

• Packinghouse processing reduced average aerobic plate counts from 4.0 to 2.1 log CFU/cm² and yeast/mold counts from 3.3 to 1.3 log CFU/cm².
• Waxing alone decreased aerobic plate counts and coliforms, with no Escherichia coli or Salmonella detected post-processing.
• Washing and rinsing reduced inoculated E. coli by 2.4 log cycles; combined washing and waxing reduced it to 1.4 log CFU/cm².

Conclusions:

• Commercial citrus packinghouse processes are effective in reducing microbial contamination on fruit surfaces.
• Washing and waxing are key steps in minimizing pathogen load, contributing to citrus fruit safety.
• No significant pathogen contamination (E. coli, Salmonella) was detected after standard processing.