Glycerine, Glycerites and Preservative Power

A lot of you lovely readers have been inspired by the glycerites I have been making lately, and several of you have asked me about the preservative power of glycerine.

Can glycerine function as a stand-alone preservative in a glycerite?

This is an excellent question.

Why?

Because the answer is not as straightforward as you were undoubtedly hoping it was going to be, but stick with me and we'll take a serious look at the hows and whys of glycerites and the preservative power of glycerine.

Preservatives in Glycerites? Is that Even Necessary?

The need for adding preservative to a glycerite depends. It depends not only on what you are using to make your glycerine extract, but on how much you use of what.

You: (groan) Really, Lise? Seriously? Does this have to be so difficult from the get-go?! Surely there is a simple answer!

I feel your frustration.

But you have to remember that glycerites can be made with a gazillion (if not a trillion gazillion) different things:

• dried herbs
• fresh herbs 
• dried whole flowers or petals
• fresh flowers or petals
• dried fruits
• fresh fruits 
• fresh veggies 
• etc.

So there's really not one perfect answer to this question. I wish there was, but then life would just be far too simple, and life – apparently – doesn't like being simple when it comes to glycerites.

Why Life Isn't Simple When it Comes to Glycerites

While researching glycerite-making methods, I came across numerous different recommendations of how much glycerine to use to ensure proper preservation.

And all this time, I did not come across a single written or online source that could recommend percentages when making a glycerite with fresh food.

Not.  A.  Single.  One.

I did make note of every recommendation did find. And according to those recommendations, each of the following percentages is the norm for how much glycerine to add to a glycerite:

• over 25%
• 50%
• minimum 50%
• over 55%
• 75%
• 80%

Quite a span, there, don't you agree? Many of these sources also offered a 'use by' period, and the range was from 6 months to 2 years.

These sources all struck me as serious, professional, and experienced.

My first post on cucumber glycerine extract (link below) referred to a guide that called for 50% glycerine, reconstituted dried herbs and the addition of 0.6% broad spectrum preservative.

I chose to (almost) follow that guide with the fresh food glycerites I have been making – using 0,5% preservative and a glycerine percentage of 'just around 50%'.

'Just around 50%'? Is That Accurate Enough?

Nope.

'Just around 50%' is not accurate enough.

With fresh fruit and veg, the water-to-glycerine ratio gets tricky. To add to the fun, fruits and many vegetables contain sugars – which can make for an additional challenge.

If you don't know the exact water (and sugar) content, it's pretty much impossible to calculate exact percentages.

How does one measure the exact water (and sugar) content of a fresh strawberry?

One cannot (if one also wishes to use it in a glycerite).

The only way to approach the water question is to find the average water content of said fruit (or veg), then work from there.

But average numbers are not exact numbers.

So.

To know for absolute sure how much – if any – preservative needs to be added to any glycerite, you need to do some calculating.

For Real?!!

You: (groaning and eye rolling)  Math, Lise?! Seriously?! Could this get any worse? Why isn't there an easier way?

I totally feel your pain.

Really.

I've already spent quite a bit of time trying to find the answers. And if there was an easy, all-in-one, simple-dimple answer to this question, I would hand it to you on a silver platter.

But there isn't.

So I can't.

But there's something I can (and will) do.

What I Can Do

I can give you a general guideline, and that is this:

Glycerine will greatly reduce the possibility for bacterial growth when it exceeds 50% percent of the formula.

You still have to do the calculating on the material you are using and go from there.

Because here's the thing:
from what I have been able to find in the time I have been researching this, it would appear that information on the preservation power of glycerine in fresh food glycerites is completely uncharted territory.

In short: your guess on formulating the perfect glycerite is as good as mine.

I can (and will) also give you a few helpful tips to help you on your way.

 A Few Glycerite Making Tips

• Always measure accurately – and by weight 
• Always work clean (keep your work space clean, sterilize equipment, etc) 
• Keep copious notes
• Label everything you make with a date, ingredients, and everything else that will help you recreate (or be able to pinpoint why you don't want to recreate) your formula
• Always save a LABELLED, DATED portion of your formula for observation – even long past your 'use by' date (this is by far one of the most educational things you can do for yourself, and will require a bit of storage space as you continue to make products).
• Keep even more notes 

It won't be long before you have your own encyclopedia of experience and notes to draw on.

Have fun.

Even with the math part.

You can totally do this. How do I know? Cuz I just know.

:)

Do Tell

How long do your glycerites last? Please share by dropping a comment!

Glycerite How to's on This Blog

Cucumber: 1
Cucumber: 2
Lemon
Strawberry
Blueberry

References

Jay E. Slater, MD, The role of glycerol on allergen extracts, Laboratory of Immunobiochemistry, FDA

Rebecca Wright, Guide to preserving Natural Products, Natural Skincare Formulations

John Kabara, Donald S Orth, Preservative free and self preserving cosmetics and drugs, Priciple and Practice, 1996, 45-69

Preserving Syrups, The Pharmaceutic and Compunding Laboratory, UNC Eshelman School of Pharmacy

Cech, Richo, Making Plant Medicine, 2000

Gladstar, Rosemary, Medicinal Herbs: A beginners Guide, Lemon Balm Glycerite, 160

Gladstar, Rosemary, Family Herbal  Guide to living life with energy, health and vitality, 2001

Wikipedia, Glycerine

Green, James, The Herbal Medicine Maker's Handbook - A Home Manual, p 185-192

Wynn, Susan, Fougere, Barbara, Veterinary Herbal Medicine, p225

Fetro, Charles W, Avila, Juan R, The Complete Guide to Herbal Medicine, p8

Preservative for Biological Specimens , US Patent, 1978 

Soap and detergent Association, Glycerine, an Overview, 1990