Do preservatives (any kind of preservative) prevent the oils in lotions/creams from becoming rancid? Or is the tendency of some oils to go rancid something that has to do with the expiration date of the oils themselves?
ROE and Vitamin E will slow rancidity. (but have no effect on mold or bacteria growth) All oils have different rates at which they will go rancid. Hemp oil will go rancid very quickly, where jojoba oil never goes rancid (cuz it's actually a wax :wink: ) I believe tha paul treats some of his more volitile oils with either vitamin e or roe as soon as he gets them. Which I think is a good practice because since the vit e slows the rancidity process, you want to slow it down asap.
Even when you do treat with the vit e and roe, the oils will still go rancid. There are resources available online that will tell you the shelf life of your oils, of course you'll want to buy from a supplier you trust so that you can feel confidant that your oils are as fresh as possible when you get them
If you're shooting for the unnatural shelflife that commercial lotions have, you can add lots of chemicals....but who really wants that.