Purpose: This study determined the microbial quality of fresh blueberries collected from berry-packing houses.
Methods: Unpacked and packed blueberries (n=92) were collected in duplicate in the morning, lunchtime, and evening from five different packing house in Georgia from May to June of 2015. Berries were rinsed (n=92) or homogenized (n=92) in 0.1M PBS and appropriate dilutions were inoculated on tryptic soy agar, MacConkey agar, Enterococcus agar and potato dextrose agar and resulting microbial colonies were enumerated. The influence of packing, sample source, sampling time, and sample preparation method on berry-borne microbial counts was determined.
Results: Average aerobic bacteria, yeast and mold, and total coliform counts of collected berries ranged from 3.13 to 5.20, 3.76 to 4.85, and 0.62 to 2.21 log CFU/g, respectively. Six berry samples from two processing plants tested positive for fecal coliforms and one sample tested positive for enterococci. Sample source and sampling time have a significant influence (P≤0.05) on the aerobic bacteria counts, and yeast and mold counts. Berry samples collected in the evening had the lowest microbial counts. Packing of fresh berries had no significant influence (P>0.05) on microbial counts, however, non-packed berries had higher aerobic bacteria, yeasts and molds counts than packed berries. Homogenization of berries before enumeration resulted in higher yeast and mold counts than rinsing.
Significance: This study suggests that sorting of blueberries before packing for the fresh market does not lead to reduction in microbial counts. Packed blueberries are labelled as not ready to eat products therefore, thorough washing of retail blueberries before consumption should be encouraged.