Glass Contamination: Why Does Glass Keep Getting In Our Food?

glass contamination

In the past 30 days they have been at least four food product recalls over glass contamination.

In March, Nestle recalled several spinach-containing varieties of DiGiorno, Lean Cuisine, and Stouffer’s dishes and Constellation Brands issued a recall of select Corona packs. Last week, Snyder’s-Lance ordered a recall of its Emerald 100-calorie packages of cashews and Roland Foods took a similar step to recall cans of fire-roasted pepper strips.

In every case, the recalls were issued after glass fragments were found by a consumer. Although no injuries have risen from any of these incidents, they do raise one very specific question: how does glass get into food in the first place?

Sources of Glass Contamination

Contamination can take many forms during food processing. Sometimes machinery doesn’t get cleaned thoroughly and dirt can slip in. Other times machinery doesn’t work as well as people would like, which is how you can end up with things like organs or bone in mechanically de-boned meat. The worst case, of course, is when lax or outright inept sanitary practices lead to contamination with things like salmonella.

Although none of these are acceptable, it is at least easy to understand how they might come about. Glass, however, is a different story. Glass does not have as large a role in food processing as other materials, except when used for bottling. This is probably why most identifiable sources of glass contamination don’t necessarily have to do with the manufacturing process itself.

Glass contamination that isn’t from the food’s own container (“glass-in-glass contamination”) is usually the result of something like a broken light bulb, shattered window or skylight, fractured thermometer, or a similar piece of equipment. Glass shattering is not always 100% avoidable either. Food production and storage areas need to be highly lit and certain elements of processing can result in high temperatures capable of compromising a glass structure.

If workers have to wear safety goggles, that is yet another possible avenue of contamination. Even shatterproof glass isn’t indestructible and this combined with every nearby bulb, window, or pair of goggles being a possible source, it can be seen how a contamination event might occur. While workers will do their best to clean up after something shatters, pieces can be missed. This problem is compounded in frozen foods where glass fragments can be mistaken for ice crystals.

The Role of Regulation

While regulation alone can’t prevent all cases of glass contamination, it can certainly cut down on the number. The USDA has specific requirements for what kinds of glass is allowed in food storage or production areas—typically heat resistant and shatterproof.

It is unclear if any of the companies who issued recent recalls were in compliance with these specific regulations since, even if they were, the contamination could still have happened. Ultimately it is up to manufacturers to be responsible in both preventative and reactive steps to avoid or minimize contamination risks and up to consumers to report contamination that they find.

“Snyder’s-Lance Announces Voluntary Recall of a Limited Number of Emerald® Cashew Roasted & Salted Halves & Pieces Due to Potential Presence of Glass,” U.S. Food and Drug Administration web site, April 1, 2016;, last accessed April 5, 2016.
Noonan, E., “Preventing Glass Contamination in Food Processing,” September 18, 2013;, last accessed April 5, 2016.
Rosado, J., “USDA Regulations Regarding Glass in a Food Manufacturing Facility,” Small Business web site;, last accessed April 5, 2016.
“Stouffer’s Meals and DiGiorno Pizzas Recalled for Glass in Food,” March 10, 2016;, last accessed April 5, 2016.
“Corona beer bottles recalled, may contain glass particles,” Fox News web site, March 11, 2016;, last accessed April 5, 2016.