The following blog is part internet "facts" and part Jessica McClard's loose brain associations. She is NOT a scientist. Please take what she says with a grain of salt and certainly not as anything remotely resembling evidence-based practice.
“I worked in a grocery store while in college, and we routinely had non-refrigerated trucks parked for hours in the 100+ heat awaiting our unloading them.” - busboy789
You don’t have to look hard online to find anecdotes like this one. But Heloise says to keep all canned foods should be kept at 70°F or below...
This time of year, most folks with questions about stewarding a Little Free Pantry have one in common: What do we do when temperatures heat up?
LFP turned two in May...two Arkansas Summers. Turnover remains brisk. Just yesterday, I stopped by to put a few things inside, and a carload of grown men pulled in behind me and took most everything. Less than a minute.
When I polled the LFP Stewards Group, asking, “Which of these describes your approach or experience stocking projects in Summer temps?”
- “Items do not stay long enough to become unsafe,” or...
- “We ask folks to keep cans back until temperatures moderate,"
30 stewards indicated the former. One controls for temperatures. To do that, stewards must either collect and distribute all donations, or post some kind of notice at the site. Maybe share something like this:
Even then, without eyes on the box 24/7, someone could go right ahead with that can of green beans (likely gone before you'd ever know it). In other words control is near impossible. But that doesn’t mean we should just...
According to the USDA, it's best to store food at temperatures below 85 °F. Many of us won’t see 85° consistently until October. High temperatures (over 100 °F) are actually harmful to canned goods. The longer items are exposed, the more harm done. “Harm” ranges from nutrient loss and a change in appearance for food in glass containers to bacterial growth.
Different bacteria grow at temperatures from 32°F to 158°F, with bacteria causing foodborne illness growing best at body temperature. Whether that means temperatures around 98.6°F are most problematic, I don’t know. I’m not a scientist. Nor do I know the calculus for temperature change over time at a certain heat. (I do know my enchilada casserole heats through in 30 minutes at 350° and a pork loin takes longer.)
On this topic generally, Google wasn’t particularly helpful. (Its first two hits were from bloggers, “beprepared” and “survivalmom.”) But what does seem certain is cans and glass containers are most susceptible to spoilage from exposure to oxygen, not heat. Extreme temperatures cause container expansion and contraction, compromising seals.
Maybe the best notice to post at our projects is notice about discarding items that are deeply dented, bulging, leaking, or heavily rusted.
Maybe I should Ask Heloise.
Better yet...a food safety scientist/expert! Do you know someone who can answer these inelegantly posed questions? Email me! I'd love to feature a follow-up guest post from someone who'd never consider using an Elsa graphic.
jessica@littlefreepantry.org