Refrigerate lettuce to reduce risk of E. coli contamination, researchers say

Leafy inexperienced greens are essential sources of dietary fiber and vitamins, however they will harbor dangerous pathogens. Specifically, lettuce has typically been concerned in outbreaks of foodborne sickness throughout the U.S. A new study from the College of Illinois Urbana-Champaign examines components that have an effect on E. coli contamination on 5 totally different leafy greens—romaine lettuce, green-leaf lettuce, spinach, kale, and collards.

“We’re seeing a number of outbreaks on lettuce, however not a lot on kale and different brassica greens. We needed to be taught extra concerning the susceptibility of various leafy greens,” mentioned lead creator Mengyi Dong, now a postdoctoral analysis affiliate at Duke College. Dong performed the analysis as a doctoral pupil within the Division of Meals Science and Human Vitamin (FSHN), a part of the Faculty of Agricultural, Shopper, and Environmental Sciences (ACES) on the U. of I.

The researchers contaminated complete leaves from every of the 5 greens with E. coli O157:H7 and noticed what occurred after storage at 4° C (39° F), 20° C (68° F), and 37° C (98.6° F). General, they discovered that susceptibility was decided by a mixture of temperature and leaf floor properties, similar to roughness and the pure wax coating.

“At room temperature or increased, E. coli grows very quick on lettuce, but when lettuce is refrigerated at 4° C (39° F), we see a pointy decline within the E. coli inhabitants. Nevertheless, for waxy greens like kale and collard, we get the other outcomes. On these greens, E. coli grows slower below hotter temperatures, however whether it is already current, it may survive longer below refrigeration.”

Even so, kale and collard are total much less inclined to E. coli contamination than lettuce. Moreover, these greens are normally cooked—which kills or inactivates E. coli—whereas lettuce is consumed uncooked. Rinsing lettuce does assist, Dong mentioned, however does not take away all of the micro organism due to their tight attachment to the leaf.

The researchers additionally inoculated minimize leaves with E. coli O157:H7 to check the intact floor of an entire leaf to the broken floor of a minimize leaf.

“Entire leaves and freshly minimize leaves current totally different conditions. When the leaf is minimize, it releases vegetable juice, which comprises vitamins that stimulate bacterial development,” Dong defined. Nevertheless, the researchers discovered that spinach, kale, and collard juice truly exhibited antimicrobial properties that defend in opposition to E. coli.

To additional discover these findings, they remoted juice (lysate) from kale and collards and utilized the liquid to lettuce leaves, discovering that it may be used as a pure antimicrobial agent. The potential functions might embody antimicrobial spray or coating to regulate foodborne pathogen contaminations at each pre-harvest and post-harvest phases, the researchers mentioned.

“We won’t utterly keep away from pathogens in meals. Greens are grown in soil, not in a sterile setting, and they are going to be uncovered to micro organism,” mentioned co-author Pratik Banerjee, affiliate professor in FSHN and Illinois Extension specialist.

“It is a complicated downside to resolve, however we will embrace finest practices within the meals business and meals provide chain. There’s a number of curiosity from the analysis neighborhood and federal companies to handle these points, and the USDA imposes excessive requirements for meals manufacturing, so total, the U.S. meals provide is sort of protected.”

Banerjee and Dong emphasize they don’t need to discourage folks from consuming contemporary fruit and greens; they’re a part of a nutritious diet. Simply comply with meals security pointers, wash your lettuce completely, retailer it within the fridge, and take note of any meals security recollects in your space, they conclude.

The findings are printed within the journal Meals Microbiology.