Hygiene conditions of fresh blueberry packing lines and microbial quality of fresh market blueberries in Georgia

Authors: CHEN, JINRU - University Of Georgia; Takeda, Fumiomi; DEVETTER, LISA - Washington State University

Submitted to: Journal of the American Society for Horticultural Science
Publication Type: Abstract Only
Publication Acceptance Date: 4/3/2019
Publication Date: 7/20/2019
Citation: Chen, J., Takeda, F., Devetter, L.W. 2019. Hygiene conditions of fresh blueberry packing lines and microbial quality of fresh market blueberries in Georgia [abstract]. Journal of the American Society for Horticultural Science. Paper No. 30230.

Interpretive Summary:

Technical Abstract: Foodborne outbreaks have been linked to the consumption of blueberries contaminated with pathogenic bacteria. The microbial quality of blueberries could be influenced by the hygienic conditions prevailing during postharvest handling. This study evaluated the hygienic conditions of six fresh blueberry packing lines and microbial quality of fresh market blueberries in Georgia. Five of the six packing lines were sampled twice, and the remaining one was sampled once during the summer of 2015 and the summer of 2017. A delimited area on each of the 10 selected sites of the packing lines was swabbed with sterile sponges before the packing started (AM samples), during lunchtime (NOON samples), and at the end of the packing day (PM samples). The sponges were thoroughly rinsed with Dey-Engley neutralization broth and sampled for total aerobes, yeasts and molds, total coliforms, fecal coliforms, and enterococci. Meanwhile, unpacked and packed blueberries (n=124) were collected in duplicate for assessment of microbial contamination. Resulting microbial colonies were enumerated, and presumptive fecal coliforms and enterococci confirmed. Results of the packing line survey showed that sample site and sampling time had a significant influence (P=0.05) on total aerobic, yeast and mold, and total coliform counts. The PM samples had significantly higher (P=0.05) total aerobic and yeast and mold counts than the NOON samples, which had significantly higher (P=0.05) counts than the AM samples. Forty-six out of the 310 (14.8%) collected samples tested positive for enterococci, while 27 (8.7%) samples tested positive for fecal coliforms. Berry lugs, rubber belts on color sorters, and premature berry disposing areas had significantly higher (P=0.05) microbial counts than the other sites. For the berry analysis, eleven berry samples from three packing houses tested positive for fecal coliforms and one sample tested positive for enterococci. Mean total aerobic counts, total yeast and mold counts, and total coliform counts of the berries were 3.89, 4.42 and 1.42 log CFU/g, respectively. Sampling time had significant influence (P=0.05) on the recovery of all three groups of microorganisms. On average, berry samples collected at the end of the day had the lowest microbial counts. In general, the packing process had no significant influence (P>0.05) on recovered microbial counts; however, unpacked berries had numerically higher aerobic counts, and yeast and mold counts than packed berries. This study suggests that sorting of blueberries before packing for the fresh market does not lead to significant reductions in microbial counts.