Ease of biofilm accumulation and efficacy of sanitizing treatments in removing the biofilms formed on coupons made of materials commonly used in blueberry packing environment

Authors: GAZULA, HIMABINDU - University Of Georgia; SCHERM, HARALD - University Of Georgia; LI, CHANGYING - University Of Georgia; Takeda, Fumiomi; CHEN, JINRU - University Of Georgia

Submitted to: Food Control
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2019
Publication Date: 4/27/2019
Citation: Gazula, H., Scherm, H., Li, C., Takeda, F., Chen, J. 2019. Ease of biofilm accumulation and efficacy of sanitizing treatments in removing the biofilms formed on coupons made of materials commonly used in blueberry packing environment. Food Control. 104:167-173. https://doi.org/10.1016/j.foodcont.2019.04.036.
DOI: https://doi.org/10.1016/j.foodcont.2019.04.036

Interpretive Summary: Fresh market blueberries are sent to packinghouses after harvest to separate good fruit from leaves and other debris, and immature, soft, and off-colored berries before packed into containers. In this process, blueberries contact surfaces made of stainless steel, rubber, and several types of plastics. If these surfaces are not effectively sanitized, bacterial biofilms can form that could adversely impact safety. In this study, we assessed the formation on bacterial biofilms on coupons made of materials on blueberry packing/sorting equipment and evaluated the efficacy of commercial sanitizers in removing the biofilms formed on these coupons. The amount of biofilms accumulated on polypropylene coupons was higher than that on all other surfaces and the lowest amount was found on stainless steel surface. After sanitizing, the highest residual biofilm mass was found on rubber and the lowest amount on stainless steel and polyurethane surfaces. Among the sanitizers assessed, ozonated water (OW) treatment was most effective in removing biofilms from stainless steel, but all sanitizers were less effective in removing biofilms on rubber surface. These results emphasized the importance of selecting proper chemical sanitizers and daily cleaning of blueberry packing line equipment, especially surfaces constructed with rubber products, to prevent biofilm formation and microbial contamination.

Technical Abstract: Biofilm-forming ability of six bi-strain mixtures of fecal coliforms, isolated from fresh blueberry packing environment, was assessed at 10°C for seven days on coupons made of materials commonly used for fresh blueberry packing lines, lugs and clamshells, including stainless steel, rubber, polyvinyl chloride, polypropylene, polyurethane, high-density polyethylene and polyethylene terephthalate. Coupons with developed biofilms were treated for one minute at room temperature with sanitizers commonly used by blueberry packers including 5 ppm chlorine dioxide, 3 ppm ozonated water, 200 ppm quaternary ammonium compound or 200 ppm sodium hypochlorite, and residual biofilms on treated coupons were quantified using the crystal violet binding assay. On average, the amount of biofilms accumulated on polypropylene coupons were significantly higher (P=0.05) than that on all other coupons used in the study. Biofilms formed on polyvinyl chloride and rubber coupons were statisically similar (P>0.05), but were significantly lower than those on polypropylene and polyurethane coupons and significantly higher than those on high-density polyethylene, stainless steel and polyethylene terephthalate coupons. Ozonated water had significantly higher efficiency in biofilm removal than quaternary ammonium compound, which had significantly higher efficiency than chlorine dioxide, followed by sodium hypochlorite. On average, significantly more residual biofilm mass was found on rubber coupons after the sanitizing treatments. The amounts of residual biofilms on polypropylene, polyvinyl chloride, and high-density polyethylene coupons were statistically similar but were significantly higher (P=0.05) than those on polyurethane and stainless steel coupons. The evaluated sanitizers had different efficacies in biofilm removal. The type of coupons and fecal coliform isolates used in the study both played a significant role in biofilm accumulation and removal on/from the selected coupons.