Wednesday, January 25, 2012

Heating, holding, freezing, and thawing our ingredients!

The temperature of our ingredients is a hot topic these days, so let's take a look at a few questions I've been posed in the last few weeks...

If we heat carrier oils, will they go rancid quicker? Are we destroying the goodness in them?

I answered this question last year in this post, but let's summarize it here. (Quick answers are no and no.)

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.

Can we heat delicate oils - like evening primrose, borage, squalane, and so on - in the heat and hold phase of our products or should we leave them for the cool down phase?

There is no chemical difference between what we call exotic oils and carrier oils. They both contain fatty acids, phytosterols, polyphenols, and all kinds of vitamins and minerals. The concept of one oil being a carrier oil and another being an exotic oil has no basis in chemistry - it's a designation we've given the oils based on availability and cost. Wheat germ oil might or might not be an exotic oil depending upon the section of the store your supplier puts it in and how common it might be in your part of the world. Don't get me wrong...there are differences between something like borage oil and sunflower oil (for instance) - borage feels drier, it contains GLA, it has a different fatty acid make up - but they aren't so different that we have to treat borage with great delicacy and sunflower oil with reckless abandon!

I've only seen one oil listed as needing to be in the cool down phase and that's kukui nut oil. And to be honest, I'm not seeing anything scientific showing that kukui nut oil can't be used in the heated oil phase of the product or anything about its sensitivity to temperature. I got this information from a supplier's website, and I can't promise you that it's accurate. 

Every carrier or exotic oil we use should go into the heated oil phase to ensure it emulsifies into the product. If you put them in the cool down phase, you are risking an epic lotion failure, which is doubleplusungood and to be avoided! There is no need to put our exotic oils into the cool down phase because we aren't heating them up to the point of smoking, which is really the only way we can damage them.

70˚C or 158˚F is not that high a temperature in the grand scheme of things. Vitamins can handle high temperatures - click here for information on Vitamin C, for instance - as can our fatty acids, polyphenols, phytosterols. In this study, phytosterols were heated for either 50˚C for several weeks or 100˚C for an hour, and the oils "did not show any significant variation in the phytosterol content."

Tara asked in this postIs 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)?

It's a good question, and yes, there can be some changes in ingredients when they go from being frozen to heated, but there doesn't seem to be so big a difference when it comes to oils, butters, and exotic oils. The changes of concern are when we have to worry about ice crystals ruining something - say veggies or meat - or when we have a lotion that goes from being in my freezing car after a week of snow days into my too warm office. I regularly freeze and thaw my oils without problem.

So can you freeze and thaw then re-freeze your oils? Yes. It's fine. Can you leave your oils at room temperature? Sure. There's no problem there either!

I know the plural of anecdote is not data and I can't just ask you to take my word for the idea that you can freeze and thaw oils without problem, but I can't find any good studies showing that it's okay to do this. You can see what the North Dakota State University has to say about freezing oils (very brief, scroll down a bit). The key problem with freezing anything is the creation of ice crystals by the water in the product. Oils and butters don't contain water, so there's no problem there! 

If we can freeze our oils and butters, can we freeze our anhydrous products? In theory, yes. It would depend what product you're freezing. If you want to freeze a bath oil - sure, go ahead. Bath melts? Why not? Your sugar scrub base (without sugar)? Sure! A balm or lotion bar? Why not? And so on. And don't worry about the bottles - when oil freezes it contracts, unlike water, which expands! (Click here for more on water and freezing!)

You cannot freeze products that contain water! Emulsified products are especially fragile when it comes to freezing as are products that might contain water soluble ingredients (like conditioner bars that might have hydrolyzed proteins and panthenol, for instance).

Learn more about oils, butters, exotic oils, and esters in the emollients section of the blog!


Tara said...

Awesome! Thanks Susan!

I also freeze my emulsifiers, because there's more room in my freezer than fridge. This should be fine, right? They're already in solid form, so it's not like they require thawing.

Anonymous said...

Hi Susan

I have a question, when you say exotic oil, do you mean Essential oils?

I keep being told not to heat the later when making my lotions...

Thank you <3

Anonymous said...

Love your blog. Been reading it for awhile. Is the smoke point the reason why Cyclomethicone and Dimethicone are usually always added to the cool down phase?

Dawn said...

Thank you, Thank you, Thank you!!

Susan Barclay-Nichols said...

Hi Tara. I'd happily keep my emulsifiers in the freezer if I had the room!

Hi Anonymous! No, I mean exotic oils like evening primrose, borage, sea buckthorn, and so on. Do not heat your essential oils!

Hi other Anonymous. No, it's not about the the smoke point of dimethicone or cyclomethicone - it's about its reaction to heat.

Leman Aydemir said...

Hi Susan,

I realise this is an old post. Just wanted to ask if I can freeze butters like shea and cocoa? thanks

Susan Barclay-Nichols said...

There are no old posts! I've answered your question in today's Weekend Wonderings! The short answer - yes.

Lexi said...

It's summer so time to break out the insect repellents.

I want to make my own insect repellent lotion based on essential oils (e.g. lavender, eucalyptus, citronella). My product is 8% essential oils.

I know you said that we are not supposed to heat our essential oils but I only obtain a stable product if I heat (otherwise the oils "seep out").

Are my essential oils really that delicate that I can't heat and hold and 65C?

Thanks for all the information you are sharing on this blog.

Susan Barclay-Nichols said...

Hi Lexi. I've answered your question in today's Weekend Wonderings. The short answer - you aren't using enough emulsifier in this recipe, as evidenced by the instability in the lotion.

Anonymous said...

I'm happy that I found this form. My question concerns blending various carrier and essential oils to create an exclusive oil moisturizer. Do I need to heat the carrier oils to achieve a well blended product or is blending at room temperature sufficient?
I look forward to your response.
Lauren R.

Susan Barclay-Nichols said...

Hi Lauren. If you're making an all oil serum, you can just blend the oils together at room temperature.

Kloé said...

Hi Susan,
first, thank you so much for sharing all this information on your blog. I have just found it and I can tell it's going to be a *wonderful* reading.
I have a question. I have recently aquired a big quantity of cosmetic oils that my boss was just going to throw away because we don't need them anymore (we used to teach beauty product making where I work, but we don't anymore). These are cosmetic grade oils, I think the supplier is New Directions Aromatic, and there are: avocado, sweet almond, EVOO, apricot kernel, grapeseed, soy, hazelnut, and even 1 bottle of refined hemp seed oil. Problem is, they are old. I mean... really old (some bottles might have been opened 3-4 years ago). I know this largely exceeds their shelf life, BUT they have been kept in a refrigerator, undisturbed for the past 3 years. I've smelled them (my nose is usually quite good) and they smell perfectly normal to me. Only 6-7 bottles on the 40-more I aquired had either a funky smell or weird sediments. I usually really trust my sense of smell (2 other people have also smell them and said they seem normal), but then, I can't see how it's possible they would've NOT gone rancid.
So, my question --is it possible that they are still good after all this time? Or am I just deluding myself for believing in a perfect world full of unicorns, rainbows and unspoilable oils?
Of course, if I were to use them, I would immediately freeze them, use them with the utmost caution and only on myself (I do not sell my products, it is only a hobby, so there's so risk of skin-poisoning innocent customers!).
Thank you so very much for your time,
(sorry if some sentences are funky, English isn't my first language and sometimes I can phrase things like I were writing in French! It's very confusing)

Kloé said...

Hi Susan,
I'm the same Kloe who commented last April. I noticed you haven't answered my question (not an accusation --I understand you are busy!). I have chosen to keep the oils, I froze them. From what I can tell (with my limited experience!), only the apricot kernel oil seem to have not survived the years. I used some of the oils and they still look and smell fine. However, I am still curious about your opinion on the matter. It took me quite a bit of courage to dare asking you this question (afraid you would just answer something along the lines of «OF COURSE NOT, WHAT ARE YOU THINKING?!?!» lol) and when/if you have the time to answer, I'd love to read your opinion. At least you could tell me exactly WHY my idea was a bad idea ;)
Thank you and have a nice day!

Susan Barclay-Nichols said...

Hi Kloe! If you are comfortable with them, use them. I won't use oils that I haven't tracked since purchase - meaning that if a friend gave me oils, I wouldn't use them as I like to track them from purchase to present day in my possession - but that's just how I feel. If you are okay with how they smell, then use them, and keep checking them. When you make products with them, make sure you are checking on those products to ensure they are doing okay.

Refrigeration is a wonderful thing! It can retard rancidity wonderfully. But once they're out of the fridge, the clock is ticking!

Never be afraid to ask a question! How else do we learn? Be wary of those who put you down for asking questions!

Sam said...

This is so good to know! I hate having to throw out ingredients, so I'm glad to hear I can freeze my oils and silicones :)

I have a follow-up question, if you have the time: does the same go for powdered ingredients (in my case, things like niacinamide and allantoin)? I'm not sure if they count as anhydrous, as I found that apparently even crystals can contain water - source.

Thank you!


Susan Barclay-Nichols said...

HI Sam! Yep, loads of our crystals contain water. Look at Epsom salts - they're filled with water! You can happily freeze those ingredients if you want, but they have really long shelf lives, so it's pointless. Just put them in a nice space and use them as you wish.