Corrugated containers sampled at produce grower-shippers by University of California, Davis, researchers and toxicologists with Haley & Aldrich Inc. all met acceptable sanitation levels.

Tests were done on 720 swab samples taken from containers from six different corrugated manufacturers in the Pacific Northwest, California and Florida. The Corrugated Packaging Alliance sought third-party testing to confirm containers meet sanitation criteria at the point of use.

“One hundred percent of the samples evaluated were below the sanitation levels of 1,000 colony forming units per swab for the organisms tested,” Maryann Sanders, senior toxicologist, microbiologist and regulatory compliance specialist at Haley & Aldrich, said Feb. 10 in a news release.

The 1,000 CFU per swab threshold used in the study was defined by Keith Warriner, professor of food safety at the University of Guelph, Ontario; the Food Safety Authority of Ireland; and the New South Wales Food Authority. The U.S. Food and Drug Administration does not have guidelines.

Reusable plastic containers were not tested in this study. In a 2014 study of RPC samples from five Canadian packing facilities, Warriner found among other things that 13% tested positive for generic E. coli and none tested positive for salmonella. “(A) high proportion of RPCs are of poor sanitary status due to inadequate sanitation or post-cleaning contamination,” he said in the study’s conclusion.

IFCO North America, Tampa, Fla., responded to the Canadian study with a statement saying more than 1 billion cases were shipped via RPCs in 2013, when third-party tests between March and August showed significantly lower microbials active on RPCs than cardboard boxes immediately prior to packing. No cardboard, RPC or other transport packaging were found to be the cause of any food safety incident, according to IFCO.

Test methods in the new corrugated study were comparable to those used in the Canadian study and another RPC study from the University of California, Davis, said Rachel Kenyon, vice president of the Fibre Box Association. The association jointly sponsors the Corrugated Packaging Alliance with the American Forest & Paper Association; AICC: The Independent Packaging Association; and the Technical Association of the Pulp and Paper Industry.