A Moment of Caution - Spotting Defective Food Cans

by Susan Young - April 3, 2014, 5:01pm. Updated May 9, 2024, 1:58 p.m.

It has been a decade or more but I spotted one! There, in the middle of that case of store brand cat food, hid a blown can. At first hurried glance a can of normal enough appearance, unremarkable in every way. Click on any of the photos, below, to see a larger size of the image.

Younger buyers - those under 30 - may never have had an encounter with a blown can. Yet, as the world of packaging grows progressively faster and cheaper blown cans are starting to reappear on our store shelves. So, this just might be an opportune time to review the mechanics and the implications of a blown can.

A blown can indicates that dangerous gases formed inside the can during packaging due to a defect in the process. The contents of the can have been seriously compromised. Spoiled food is a major cause of blown cans and signals that the food inside is noxious, poisonous to you and your pet. But, spoilage is not the only cause of abnormal cans. Overfilling, buckling, denting, or closing while cool may also be responsible. Can defects, punctures, pin hole punctures, or rough handling of the product also contributes to spoiled food.

If you find a blown can on a store shelf take it to the manager and request that they destroy that one can. If you should be unlucky enough to have unknowingly bought a blown can, or, a can blows while in your cupboard, throw it away. Do not open it. There will be no loud bang. A can blows in silence and remains looking very much like a normal can. Almost undetectable.

What to Look For

Knowing what to look for, though, you can easily identify any suspect can. Blown cans appear in one of three configurations:

1.   The "flipper" whereby only one half or less of the lid of the can bulges upward.

The bulge can often be manipulated with your fingers and can be pushed from side to side along the top of the can. The bulge can also be pushed down into the can only to bulge again after a few minutes.

2.   The "dome" whereby the lid is rounded on the top of the can (convex shape), rather than being slightly depressed or concave in appearance, as all healthy cans should be.

showing can flipper slightly raised above the level of the top of the can which is also slightly raised upward

Notice the distance the tab is above the surface of the lid in this photo. This is the first clue. Notice also the slightly rounded appearance in the centre of the lid. This is the second clue. The bottom of the can may also be somewhat rounded out below the bottom edge of the can. The bottom will be very hard to push inward.

showing hard swell on a food lid

3.   The "modified dome" whereby the lid can have either a "soft swell" that can be pushed downward into the can only to immediately pop back up. Or, the lid may have a "hard swell" whereby the lid is unable to be pushed downward at all. The bottom of the can may be perfectly normal in appearance.

To keep your pets and your family healthy and safe always carefully check canned food while shopping. Any dent, wrinkle, fold or separation of seams of a food can is your cue that the hermetic seal of the can may have been compromised. When a cans' hermetic seal has been compromised, the safety and quality of the food inside will also have been compromised. Stay aware. Keep your furry family safe.

A Different Kind of Spoiled Food

showing outside of spoiled food can and its lids
During November of 2023, I encountered another form of spoiled cat food. In this case, I found the suspect can amongst an order of 12 cans made by the same pet food manufacturer purchased at a local retail store. The first thing I noticed was the outside of the can felt greasy. So, I wiped the can down thinking that perhaps something had been spilled on it at some point in its' travels. Wiping the can down, though, did not help the product wrapper to dry. The wrapper remained greasy looking and I could see that the paper had wrinkled and looked wet. The condition of the paper wrapper made it so that I could easily see the ribs of the tin underneath the wrapper. I didn't think much more about this particular can of food and put it in my cupboard.

showing outside of spoiled food can and its lids
The day arrived when I went to open this suspect can of food. When I took the can to open I noticed that around the outer rim of the lid there were what looked like rust spots. This started me thinking that I had a can of cat food that was probably spoiled. As soon as I opened the can the smell of the food was absolutely putrid! It smelled like something had died inside the can. Also, there was about one inch of food missing from the top of the can and I could see rust along the top of the can seam where the food was missing.

I immediately telephoned the manufacturer. They were very responsive and offered to refund me the purchase price. While I was on the phone to them, I provided them with photos of the can that I had taken. They suspect that the can had suffered a pin hole puncture sometime after packing and leakage of the water in the product had occurred. The loss of water in the product would result in shrinkage of the product in the can and the pin hole puncture would allow foreign organisms to invade the product. The result, the spoiled can of cat food that I had purchased. Next time, I'll check the shipment at receipt and immediately return the product.

Further reading on this subject can be found at on the FDA website.

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