Food expiration dates are everywhere but according to an article in the NY Times,1 most of them are for marketing, not safety, reasons. What about the sanitizer test strips used in hospitals, kitchens, daycare, cruise ships & long term care facilities? These strips ensure proper strengths of sanitizing/disinfection chemicals will work as needed on knives, cutting boards, doorknobs to faucet handles. Does the same logic apply to sanitizer test strip expiration? Good today & probably good tomorrow too!

Some Sanitizer Test Strips Never Expire

The 0-200ppm chlorine test strips are the simplest and most robust of sanitizer test strips commonly used in commercial kitchens. They come as short strips of paper, 100 in a plastic bottle, and are based on a very well understood chemical reaction known as the iodine starch reaction 2. It would be the slightest of exaggerations to say these strips never expire. Strips in 10-year-old bottles that have sat unopened on the manufacturer’s shelf still perform exactly the same as freshly made ones. They are so stable that we have sold them for over 10 years without even a batch number on them. However, for the sake of accurate stock rotation, we will be adding these going forward.

Chlorine & Iodine Sanitizer Test Strips

200ppm chlorine & 50ppm iodine sanitizer test papers are found in every commercial kitchen. They are cheap to make & have no set expiration date due to an indefinite shelf life.

They are also extremely cheap to make. We advise our customers to buy a 5 year supply to save on freight. For customers who buy 10 at a time, that brings the cost in under $3.00 per bottle, including freight.  Beware of offers “free shipping”. That usually means heavily padded prices in case you buy just 1 or 2.

 

High-Level Strip Expiration

At the other extreme are the 10000ppm chlorine test strips and 10000ppm quat test strips. These strips use more complex chemical reactions and are very sensitive to moisture. They can, in fact, degrade quite quickly if left out in the open, exposed to high humidity levels. As such, they and even the lower range 1000, 1500 & 2000ppm strips all come in airtight, desiccant lined bottles which can absorb some of the airborne water vapor when a strip is extracted.

Test Strips in Desiccant Bottles-Long Shelf Life

Various chlorine, QAC & hydrogen peroxide sanitizer test strips get a shelf life boost when packaged in desiccant lined bottles. Left unopened, these strips are good for 5 years or more. The countdown starts once opened & they should be used in 6 months.

The standard guarantee on these strips is 2 years after purchase which typically falls within the 27 months after the batch date on the bottle.  Left unopened, these strips are completely accurate and as fast reacting, even after 5 years on the shelf. These strips are typically good for 6 months after the bottle is opened. This is simply because the desiccant in the bottle gets used up and the strips slowly lose their potential for measuring.

Herein lies the difficulty of adding a set expiration date. These are relatively expensive strips and throwing away perfectly good strips based on an arbritary expiration date is not good economic sense. Instead, we suggest customers buy only what they think they can use in 2-3 years. Mark the date on the bottle with a felt marker or similar after you open it.  At 6 months after opening, test freshly opened sanitizer since the undiluted concentration should be accurate.

Use our dilution calculator to create a small amount of solution and see how the strip performs. If the numbers make sense, keep on using the strips for another few weeks & repeat while the strips last.

 

Footnotes/References

1) The NY Times requires a subscription signup but it allows up to 4 free articles per month.

2) See Wikipedia for the: Iodine starch reaction. Chlorine is also a halogen, two rows above iodine in the periodic table but reacts with 1/4 the intensity.

3) Related information: Coronavirus/norovirus: The art & science of handwashing.

4) Using stronger chlorine concentration to kill viruses: What Kills Norovirus on Surfaces (also applies to COVID-19).

5)  Wash, Rinse, Sanitize: 200ppm chlorine test strips put through their paces.

6) Strong Bleach; An Old Chemical Kills New Bugs. An early blog for when we first started offering the 10000ppm chlorine strips.

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