Reusable Produce Containers Often Contaminated: Study

Reusable plastic containers for packaging of produce show troubling signs of being unsanitary, according to a University of Guelph study.

The researchers found visible organic residue, bacteria, mould and yeast in reusable plastic containers (RPCs), which are used to package fruits and vegetables for shipping to retailers.

Some of those problems have worsened since a smaller 2013 study by the same researchers, said lead author Prof. Keith Warriner, Department of Food Science. Warriner’s team worked with researchers from the University of California-Davis, and will be conducting a follow-up study that analyzes risks and discusses solutions. The study, which has garnered media attention recently, is also scheduled to be discussed at a Nov. 12 conference. It was conducted on behalf of the Canadian Corrugated Containerboard Association.

The researchers examined 160 crates over a period of up to 10 weeks in Ontario and Quebec. They randomly selected RPCs from different lots of trays that had been delivered on pallets wrapped in plastic.

The researchers visually inspected the containers and tested for food safety indicators (E. coli, Listeria) and spoilage indicators (yeast, mould). They found no listeria, but they did find other indicators.

“Of more concern was the recovery of fecal indicators that included E. coli that strongly suggested the crates had been contacted by either contaminated produce and/or water,” the report said.

Warriner said this is less a consumer concern and more a biosecurity issue for farmers and government officials.

“Plant pathogens could be easily transmitted from one region to another,” he said.

“As an example, if you look at plum pox virus, which was introduced in 2000, it took Ontario 11 years to eradicate the plant pathogen. Although there is a risk of human pathogens being transferred, this would be considered low.”

This new study found some improvements, including fewer damaged containers, and found that Ontario RPCs were cleaner than those in Quebec.

“However, the same issue of labels from previous users and high microbial counts persists. Growers could reject any crates at the point of delivery, but retailers need to do more to ensure standards are being met. Retailers are the ones demanding crates be used.”

The report is titled, “Microbiological Standards for Reusable Plastic Containers Within Produce Grower Facilities Within Ontario and Quebec​.”

Prof. Keith Warriner
Department of Food Science
519-824-4120, Ext. 56072