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, daycares, cruise ships & long term care facilities? These strips ensure that the right dilutions have been done & proper strengths of sanitizing/disinfection chemicals will work as needed on everything from food, water, knives, cutting boards, to doorknobs & faucet handles. Does the same expiration date logic apply to sanitizer test strips?
Food Expiration Dates
Not all food is the same. Expiration dates on packaged chicken or hamburger are there for good reason. A few scattered bacteria living on fresh meat food days before expiration won’t likely harm you. Fast forward a few days to the expiration date or later & thousands of bacteria have become millions. Even worse, if you left the meat sitting on the counter for a few hours at room temperature, those millions have become billions. Eat it & you could be looking at a bad case of food poisoning caused by Salmonella, E. coli, Listeria & so on.
On the other hand, consider yoghurt with live cultures. Ever opened & eaten some a day, a week, even months after the expiration date? Nothing. Why? Because that is what probiotic means. It’s the live bacteria in yoghurt that you want to get into your digestive tract because they keep the bad bugs at bay. Of course, once opened, you may find mold a week or month later but that’s caused by fungus. It shouldn’t do serious harm as disgusting as it might look.
What about that apple or spaghetti sauce you made in your pressure cooker & put into sealed mason jars? It’s completely sterile & that struggle to open the jar is because of a vacuum created by cooling. The contents are air tight & can be safe to eat years later. Once you open it though, time to refrigerate.
The last scenario describes sanitizer (& other) test strips stored in scientifically designed desiccant vials. Read on to find out the science behind it & why you should not toss perfectly good, expensive test strips based on arbitrary expiration dates.
Sanitizer Test Paper Expiration Dates
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 is not an exaggeration to say these strips never expire. Strips in 10 year old bottles that have sat unopened 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 lot/batch (date of manufacturing) number on them. We have high turnover of these but for the sake of customer confidence in 100% accurate stock rotation, we will be adding expiration dates to these going forward.
Sanitizer Test Strip Expiration Dates
All air/moisture sensitive Indigo™ plastic backed sanitizer test strips come in desiccant bottles. These strips have paper pads with indicator chemicals in them. If you leave these strips out in the open, their test pads will absorb water and eventually inactivate the indicator chemicals. Sanitizer test strips stored in airtight, desiccant lined bottles can for all purposes, be preserved indefinitely.
How Do Desiccant Bottles Work?
If you have ever bought electronic goods, you likely found a small packet of silica gel, a type of desiccant, in the box as well. They absorb water vapor which can potentially corrode electrical contacts. These packets are bulky and if stuffed into small plastic bottles, would leave little room for test strips. This is where science comes to the rescue.
Click to see these vial specifications & note the Desiccant Type: molecular sieve. This is a chemical crystal lattice known as an aluminosilicate or zeolite. These are highly porous structures capable of trapping water, sodium ions, odors or even crude oil. You may have some in your home where they are used in water softeners, cat litter & air purifiers. The vial designers found a clever way to incorporate this chemical into the walls of plastic bottles.
Click on this Certificate of Conformance to see the 2 most relative features: “moisture ingress” & “total capacity”. These numbers say the vial is designed to absorb 1000μg/day (1 millionth of a gram) while closed but performed better than that, allowing only 535μg/day. Further, the minimum it is supposed to trap is 1.5g before failing but actually trapped 1.882g.
This mean that a typical vial, lined with this desiccant & left unopened in a room at 250C & a relative humidity of 60%, is guaranteed to protect its contents for over 4 years. Its actual performance (Result) is even more impressive-nearly 10 years!
Check for Yourself
Don’t throw away your “expired” Indigo™ sanitizer test strips. The next time you open a fresh bottle of bleach or peroxide, you can use it to test the test strips. Use our dilution calculator to create a small amount of solution. If the test strip & the dilution calculator values agree, you know the strips are still good!
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.