Thursday, March 3, 2011

Question: Heating and holding our ingredients

Papi asked this question:  I have a question, if we heat oils (like grapeseed) at 70˚C won't it get rancid? And maybe we ruin some of its properties too (like evening primrose oil) or the 70˚C is the safe temperature? 

This is a good question because the last thing we want is to have rancid oils in our products (click here for more information on the mechanisms of rancidity)!

Given how many things we use call for inclusion in the cool down phase - extracts, panthenol, silicones, some cationic polymers, and so on - you'd think that we'd want to treat our oils more gently. Heating them up to 70˚C and holding can't be a good thing, right? But heat won't ruin our lovely oils because we aren't heating them up to a temperature where they will start smoking or burning or oxidizing. (For instance, coconut oil has a smoke point of 180˚C or 350˚F. Click here for a list of the smoke points of various oils.) As you can see, the more refined the oil, the higher the smoke point. Grapeseed oil isn't as fragile as one might think: It has a smoke point of 216˚C, which is right in the middle of the list!

Yes, heat will increase the rate of oxidation of our oils, but only by a bit, and we can compensate for that by including Vitamin E or another anti-oxidant. It's not going to speed up the rate of rancidity so much that a 1 year shelf life lotion becomes a three month shelf life lotion. It's more like making a 1 year shelf life lotion a 11.5 month shelf life lotion. And besides, if you don't heat and hold, you're not going to get a great emulsification anyway, which severely limits the shelf life of every product to "the moment it fails", which could be shortly after creation.

Someone else asked about including our lovely hydrosols, aloe vera, and other botanicals in the water phase, reasoning that the goodness will be boiled out of them. But we aren't boiling our lovely ingredients! 70˚C or 158˚F isn't as close to the boiling point as we think, and the molecules in our ingredients can stand up to the heat without falling apart easily.

This is why knowing the phase into which we put our ingredients is so important. We don't want to add a cool down phase ingredient into the heated phase as this could hurt the great properties for which we're using it!


Terri said...

oh dear, I think I'm reading too much. I thought we needed to be above 165F. SOme info has heat/hold in the mid 170's. DOes it matter? I have so many notes my head is spinning. Being over 165F is expected for food service and anything between 140 F to 40F(in the food industry) is the 'danger zone'(temp.range for very active microbes). any thoughts? not sure if we can correlate food industry findings with lotion production? want to lessen chance of 'beasties', but not ruin the integrity of ingredients...

Susan Barclay-Nichols said...

Hi Terri. The recommendation for our products is to heat and hold the heated water and heated oil phases at 70˚C/158˚F to 80˚F/176˚F and start our cool down phase at 45˚C/113˚F. It is different from food because we're not dealing with raw meats, for instance, which have to be cooked to a specific temperature to be safe. I think we can take some things away from the food industry - for instance, washing our hands, cleaning procedures, things like that - but the temperatures are very different when it comes to lotion making.

Terri said...

THanks so much for clearing things up for me. ANd,thanks to all your wonderful information and encouragement, I had great success making a lovely facial moisturizer and toner for myself.

Tara said...

Is there some validity in the point that it is the CHANGES in temperatures that help to destroy our oils? I like to freeze most of my oils, but they need to be brought to room temperature before I can use them. I then refreeze them and thaw them again the next time I use them. Is this more destructive than if I just leave them at room temperature (or slightly below, as my work area is in the basement)?

Thanks Susan!