I am always talking about Peroxide Value (PV) when I talk about oils. This is part of how we assess the quality of an oil.
When we receive a new shipment of oil, we check:
- The Production date,
- The test date,
- The Peroxide Value,
- And the Free Fatty Acids (not to be confused with the Fatty Acid Profile – 2 different things)
“Peroxide Value” is a chemical measurement of the peroxide (aka hydroperoxides) in an oil that indicates how an oil is aging. The PV on the Certificate of Analysis from when they made the oil is a snapshot in time. Six months later we may run another PV test. The free fatty acids should be within the limit set on the spec and will go up when the PV (or oxidation) has increased measurably.
You should also always look at the production date and the shelf-life so you know what you are dealing with.
Recently Isabel (our QC/QA manager) and I did a deep dive into the international picture of safety in oil and decided to make a couple of changes to our specifications. We have raised the limit on PV on our Specifications to a PV of 5 for refined oils and 10 for unrefined oils. This does not mean they are “bad” above those limits. It means they are starting to age and will eventually go rancid.
Our recommend USE limit for safety is a PV of 20 for an unrefined or virgin oil and of 10 for a refined oil. We will not sell an oil over 10 for Virgin and over 5 for refined (except olive oil – different story)– because we know they will continue to age.
We also recommend that you use a good antioxidant in your blends. We sell a sunflower derived natural tocopherol that will often, at the least, double your shelf life.
So – remember – these are food that we are using in cosmetics, they are made from plants and they all have different rates at which they age. You can always call us with questions.