As we become more and more concerned about food safety, we have become rather obsessed with sell by dates, best before dates and use by dates. I often wonder where these dates spring from and suspect much of it is a fear mongering marketing strategy! On the Government website, it states that you can use a food up to midnight on its use by date, but not a minute after. This seems rather ridiculous to me, but I guess there has to be a cut off point somewhere.
The use by date was created to protect people from eating food that has been bacteriologically contaminated. Interestingly enough, the food poisoning events that have been reported in the press are from processed, packaged foods. For example, we all remember the botulinum poisoning from tinned John West salmon a decade or more ago. Over the years, various packeted dog biscuits have been recalled due to bacterial contamination. But no carefully dried powdered nutritional supplement has ever had a problem.
The ingredients in PET Plus are all very carefully and thoroughly dried so the contents are held in suspended animation. They only become active once they are wetted, by mixing with food or water or by being consumed, so being wetted by saliva and digestive juices. To this end, none of the ingredients deteriorate as long as the containers are stored in a cool dry place.
I have been manufacturing PET Plus for 28 years now and never had a problem. I even kept some from older batches and gave them to my own pets with no observable change in its effectiveness.
I have recently added a sticker on the bottom of the pots saying best before date June 2026 for this current batch to reassure everyone. But in reality, the powder lasts for much longer, as long as it is stored correctly.
Once the container is opened, it would be best to use it within about 4 months, but as long as it is kept cool and dry, it lasts longer. If you have a large pot and know that you won’t use it all up within 4 months, you can decant some into a smaller container to use every day. This reduces the number of times the big container is opened and so reduces the exposure of the powder to the dampness in the air. In this way, the large pot lasts longer.
At the end of the day, use your common sense! If the powder is clumping together or smells bad, it has probably been exposed to dampness and so is probably best added to your compost, where the garden beasties will love it and your compost will be awesome!