There are a lot of reasons to choose fresh over canned greens ― texture, versatility, flavor ― but a look at the FDA Defect Levels Handbook has provided us with the most convincing reason of all: Mildew.
The Defect Levels Handbook outlines the maximum level of defects mass-produced food can have before it is deemed adulterated. Because let’s face it, it would be impossible to produce food on a large scale without a defect here and there. It runs the gamut from mold to maggots.
When it comes to canned greens the maximum level of defect is an “average of 10 percent or more of leaves, by count or weight, showing mildew over 1/2-inch diameter.” These canned greens refer to greens of the mustard family, which includes collards, mustard greens, turnip greens and often times mixed greens. While this does not mean that all these canned greens contain up to 10 percent of mildew on their leaves, it does mean that it can. And that is an unappetizing discovery.
So, the mildew is the bad news. The good news is that this defect usually occurs before the leaves have been harvested and is not a health hazard. The problem, according the the FDA, is purely aesthetic.
However, if that canned green happens to be spinach ― which is classified differently because it’s not in the mustard green family ― the defect is not mildew, but larvae. Up to “two or more 3-mm or longer larvae and/or larval fragments or spinach worms (caterpillars) whose aggregate length exceeds 12 mm are present in 24 pounds.” Yep.
Chew on that next time you crack open a can of greens.