Oxygenated oils are generally a leading cause of a finished product going rancid. Rosemary extract, being highly antioxidant, doesn't allow oxygen to attach to the free fatty oils - thus making your product's shelf life a much longer one.
Oxygenated oils can be one of several causes when a finished product goes rancid. Generally the oil phase of a formulation is fairly stable, but depending upon the age of the oils you are using, and their shelf life expectancy - its always better to error on the side of caution. Rosemary extract is highly antioxidant and it doesn't allow oxygen to attach to the free fatty oils, thus giving your finished product a longer shelf life. As with all preservatives, the oils that you are formulating with must be "clean" (or free from rancidity), otherwise this preservative will not work.
Rosemary seed extract, which is also commonly called Rosemary Oleoresin, or ROE is one preservative that is both naturally derived and approved for organic skincare formulations. We recommend using this oil in conjunction with vitamin E. The two together help make a very stable oil-soluble preservative system.
Since ROE is oil-soluble, please understand it will do nothing for the water side of your formulation. Its this side that's very susceptible to mold, bacterial and yeast. Therefore, you will need to add a water soluble preservative to your system as well.
Use at a ratio of 3% or less. This product should be added at around 90° F (or below) - do not reheat your product after this preservative has been added. This product contains 5% carnosic acid.
PLEASE NOTE: this extract does hold an earth-y scent and is brownish in color. This product is not the same as rosemary essential oil.