Wednesday, April 25, 2007

Not So Simple Syrup

It's been a while folks, but I have a few drinks backlogged that I will get to very soon. But basically the problem is that it's very difficult to train for a triathlon and drink often. There must be room for both somewhere, so I'll squeeze them both in somehow.

Anyway, to follow on the simple syrup stuff from Alton Brown's show, I've been thinking about simple syrup chemistry. Turns out there's a lot more going on than just dissolving some sugar into water.

First of all is the concept of "water activity". I happen to work at a place that employs a food scientist, and she introduced me to the term while we were discussing the possible shelf life of reconstituted peanut butter powder.

Water activity is basically the amount of water that is in a substance that isn't immobilized or chemically bound. High water activity means fast spoilage, low water activity means slow spoilage. Bacteria and fungi need water, and therefore high water activity, to live and reproduce. From Wikipedia, "Bacteria usually require at least 0.91, and fungi at least 0.7". Wikipedia's list of common foods' water activities show that raw meat and milk with .97 or so water activity leads to quick spoilage, but honey or dry pasta at only .5 will stay good for a long time.

This is where sugar comes in. Sucrose (a disaccharide, made up of glucose and fructose) is a small molecule, and really good at binding up that free water. You can make a sugar syrup by just dissolving table sugar (sucrose) in water, like the commenter in the previous entry said, by pouring boiling water into a bowl of sugar. But you aren't really getting the water activity low enough to prevent spoilage without refrigeration. You can try adding more sugar than water, but at some point you're either going to get a syrup that's too thick, or run the risk of super-saturating the solution and ending up with rock candy in the bottle. What to do?

Monosaccharides like glucose and fructose are smaller than glucose, and are even better at reducing water activity. So if you were making simple syrup, you'd probably want that sucrose, which is made of glucose and fructose, to break up, right?

Turns out there are two super-easy ways to do it: for a 1:1 sugar/water solution, add a pinch of cream of tartar along with the sugar to the boiling water. Or a bit of lemon juice. (1 gram of acid per kilogram of sugar) Acid is a catalyst to breaking up those sucrose molecules into fructose and glucose. You have to simmer for 20 minutes for the reaction to totally finish, but the resulting syrup will have a lower water activity than a sucrose solution, as well as being about 20% sweeter. This stuff is called an partially inverted sugar syrup, or invert syrup for short. The "invert" part is about how it polarizes light, if you must know.

You can also make a partially invert syrup without acid by changing the recipe from a simple syrup (1:1) to 2:1 sugar/water, and simmering for 5-7 minutes until the solution is clear. The result will be a bit thicker since there is more sugar solute.

This stuff can sit out on your bar for a good six months. Although you'll probably have used it up by then, anyway.

I'm definitely going to try the acid version, as my pourers have a hard time with the thick 2:1 that I've been using. Here's to chemistry!


Anonymous Brett said...

Great post - very simple explanation.

Thought you might enjoy this read on fructose:

3:41 PM  
Blogger Barna said...

Thanks for the explanation; I┬┤ve been looking for some insight on simple syrup for some time now.

Nice blog BTW!

4:16 AM  
Blogger Darryl said...

Wow, that's interesting. I'd love for my admittedly half-assed syrup to last longer than it does. Thanks for posting.

5:15 PM  
Blogger Isaac said...

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8:28 AM  
Anonymous Jay Hepburn said...

Sounds like I've been making partially invert syrup accidentally all this time - I've always used a 2:1 mix for sugar syrup, as per Diffords Guide to Cocktails, and simmered it until clear.

I might give that 1:1 recipe a try though, as I've recently brought pourers for my bottles and have also been having trouble getting my sugar syrup through even a large "fast pour" pourer.

Thanks for the tips!

12:51 PM  
Anonymous coffeeaholic said...

Although I am not a big drinker I have been using 2/1 ratio for years for my coffee, it is way better and cheaper than any store bought syrup and very easy to flavor with any extract.

10:30 AM  
Anonymous Priscilla said...

I made this yesterday (2 C sugar, 1 C water, juice of 1/4 lemon, brought to a boil then simmered for 7 minutes) and today it has tiny threads in it. It was clear when I bottled it in a sanitized bottle. I'm a little worried at this point- any ideas?

12:15 PM  
Blogger Cocktail Jen said...


I have no idea what that might be! I don't know that anything nasty would grow inside in just one day, but I'm no food safety expert. Maybe they might be bubble trails that formed when it was cooling? If what you are seeing is more like swirls where the light changes, it just might be the thick consistency of the solution, which I've seen in some syrups before and it was fine.

When my grenadine goes bad (I've never had sugar syrup go bad), it grows a thick opaque sediment at the bottom and smells really off. But that takes months to happen.

If it doesn't smell and is still clear, I'd try some and see if you can detect any weird flavors.

3:27 PM  
Anonymous Cocktails at 80 said...

This is fantastic. I've read about and made invert sugar for brewing - it ferments differently in beer (think Belgian beer), but I didn't know anything about the 'water activity' factor.

Also, I believe Honey is a special case - there is a lot going on in a honey solution beyond sugar.

10:25 PM  
Anonymous Anonymous said...

awesome.. i was planning to make a mint simple syrup with my mint plants since they're starting to die and i haven't used them up... but i was worried about shelf life... so i added some lime juice and simmered for 20 minutes, now it will last and be perfect for mojitos :-)

12:12 PM  
Anonymous Patricia said...

Banah Sugar ( makes a Pure Liquid Cane Sugar that is like simple syrup (not inverted), made from natural cane sugar and lasts for up to 8 months, no refrigeration required. I know they are planning to retail the stuff. You might want to check them out.


1:24 PM  
Blogger festivetea said...


the problem is the "simmered for 7 minutes" you must maintain a temp of 158 for at least 40 minutes to get 20% inversion. As another note. It is not necessary to boil the sugar, this may caramelize some of the sugar, adding an unwanted taste and making it thicker. There is NOTHING that could grow in your syrup. (except crystals) I am sure your Threads are just that; Crystals of Sucrose. also called rock candy.

Joe of Joe's Syrup

12:57 PM  

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