Packing facilities for fresh blueberries have developed various protocols to clean/sanitize harvest containers to prevent cross-contamination between berries and their surfaces. However, it is unknown whether these cleaning/sanitizing practices could effectively remove biofilms formed by microorganisms from blueberry production/packing environments.
This study investigated the effectiveness of some cleaning and sanitization practices in removing biofilms formed on coupons of high-density polyethylene (HDPE), a material of blueberry harvest containers. It also assessed whether the color of HDPE affected the formation and removal of biofilms.
Three inoculums of fecal coliforms isolated from fresh market blueberry harvest/packing environments were used to develop biofilms on HDPE coupons with various colors (n=7). Coupons of selected colors (yellow and orange) with developed biofilms were treated with sterile water, 100 ppm sodium hypochlorite, and 2% liquid dish soap, respectively with or without a 5-min soaking, manually or using a benchtop wash machine for 1 min. The experiment was replicated twice, and each treatment was duplicated. Biofilms or their residues were quantified using the crystal violet binding assay. Data collected were analyzed using the Analysis of Variant of the SAS.
Treatments with soaking and using the bench top wash machine removed significantly (P≤0.05) more biofilms from coupons than those without soaking and manual washing. Sodium hypochlorite-treated coupons had significantly more biofilm residues than dish soap-treated coupons, while no differences (P>0.05) in biofilm residues were observed between these two types of coupons and water-treated coupons. Biofilm residues on the orange coupons were significantly higher than on the yellow coupons, although coupon color did not have a significant impact on biofilm formation.
The concentration of sanitizer and detergent used by some packing facilities may not be adequate to eradicate biofilms from berry-contact surfaces. The study reveals the challenges of maintaining the hygiene of blueberry harvest containers.
