Reduction of microorganisms on citrus fruit surfaces during packinghouse processing

Abstract

Citrus fruit surface microbial populations were evaluated following various packingline processes of seven Florida commercial packinghouses. At each packinghouse, six fruits (oranges or tangerines) were collected at each of four sampling points. The sampling was conducted in duplicate; thus, 336 fruit were evaluated during this survey. Average aerobic plate counts and yeast and mold counts on fruit surfaces before washing were about 4.0 log CFU/cm2 and 3.3 log CFU/cm2, respectively, and were reduced to 2.1 log CFU/cm2 and 1.3 log CFU/cm2, respectively, by packinghouse processing. Waxing alone reduced the average fruit surface aerobic plate counts and coliform counts from 3.7 log CFU/cm2 and 35.2 most probable number (MPN)/cm2, respectively, to 2.6 log CFU/cm2 and 1.4 MPN/cm2. No Escherichia coli was recovered from fruit at the end of packinghouse processing, and no salmonellae were found on fruit during the entire processing. In an inoculation study to test the effect of packinghouse processes, test organism E. coli was applied to fruit to achieve a high level (4.8 log CFU/cm2) of contamination. The average E. coli count was reduced about 2.4 log cycles by washing and rinsing with potable water (40 psi, 25°C) for about 30 s. The combination of washing and waxing significantly reduced the inoculated level of E. coli from 4.8 to 1.4 log CFU/cm2.