DIY Belgian Candy Syrup 1: Sugar Science

[Miniseries part one, two]

A while back I wanted to make a belgian trippel; traditionally this style is brewed with up to 20% simple sugars to lower the final gravity.  Naturally, I looked first at belgian candy (candi?) sugars,  but found that they were basically just crystallized table sugar, with the darker varieties having some mystery darkening agent, some leftover of the refining process which presumably somehow added to the flavor of the final product.  As far as I can tell, the only products that lend any real flavor are the golden-brown to molasses-colored candy syrups.  In fact, the flavors normally associated with the common varieties of candy sugars are actually from the yeast, as revealed on a Brew Strong episode (part one and two) when the guys visited White Labs and did some side by side tastings of identical worts fermented with different yeasts.  And yes, I realize that using such a syrup will not actually result in a trippel (its far too dark), but I was already on my way down the rabbit hole.

With sugar being so cheap and the syrups marketing for over $7 USD per pound, I immediately thought I could do better by making my own.  If you have similar delusions, I would like to go ahead and dispel them for you now.  What actually happened was an undertaking something to the effect of a side hobby and me shelling out $25 for a thermometer that can read within +/- 1 degree or better up to 500F/ 260C (which was actually quite a deal).  I immediately started researching and found there to be a vast amount of hard science behind sugar and sugar processing, but basically nothing on how to make belgian style syrups.  In fact, the only thing that seems to be known is that (apparently) its made completely from beet-derived sugar (sucrose) with some magic and secretive belgian process- like Willy Wonka, if Willy Wonka ate chocolate waffles and baguettes with tartar.  With that, here’s a spoiler alert for the rest of the post: to me, its still a secret process.  But, I did get something that made an excellent beer, so that’ll be close enough for now I suppose.  I’ll go into some of the various approaches I tried to “further the field” of syrup making in part 2; for now, I’ll go into the science.

Types of Sugar

First things first: sugar is not just sugar.  I’m not sure of how many types of sugar there are, but I’ll go into a few that are important to brewing and syrup making.  In the atomic model images below, dark grey denotes a carbon atom, red is oxygen, and white is hydrogen; click on each image to enlarge.

• glucose (aka dextrose): a monosaccharide (ie a single sugar unit, the most basic building block of a carbohydrate); caramelization temperature 300F; a reducing sugar; there is a chain structure without the ring similar to the fructose image below, but this form is extremely rare (about 99.98% of glucose molecules exist as the ringed structure); this ring must first unfurl into the chain structure before glucose can react
  

  Atomic model of glucose. Note the characteristic six atom ring.

• fructose: a monosaccaride similar to glucose but with a slightly different atomic structure; caramelization much lower than other sugars at 220F; reducing sugar; more reactive in Maillard reactions than glucose because the ring structure does not need to be broken before it can react (there is a form with a five atom ring as seen below in the sucrose image, but it is uncommon to exist by itself this way)
  

  One form of fructose.

• sucrose: a disaccaride (di- denoting it is a sugar unit built of two sub-units); composed of one unit of glucose and one unit of fructose; can be broken down (inverted) by various enzymes or by heating in the presence of an acid; caramelization at 340F; this is what we know as table sugar; not a reducing sugar (it must first invert, then both ring structures must unfurl)
  

  Sucrose molecule. Left image: the six atom ring of the glucose is visible to the right, and the five atom ring of the fructose can be see on the left. Right image: rotated slightly to show the bond between the glucose and fructose.

• maltose: a disaccaride of two units of glucose; this is the primary sugar derived from malt (hence the name); yeast has an enzyme to break this down into units of glucose before it metabolizes it; reducing sugar
• maltotriose: a trisaccaride of three units of glucose; this is the most complex sugar brewer’s yeast will metabolize (generally only lager yeasts can consume this sugar, not ale yeast)- anything with more units adds to the body of the beer (unless you get a wild yeast, some of which will consume many of the longer chain carbohydrates); reducing sugar
  

  Left: maltose; Right: maltotriose

• lactose: milk sugar not able to be metabolized by yeast (which is why it is sometimes added to make sweet or “milk” stouts), a disaccaride of glucose and galactose; reducing sugar
• honey: about 80% fructose and glucose, with some sucrose and maltose; some consider it a natural invert syrup

A reducing sugar is one which has an aldehyde group (or is capable or forming one).  This allows it to act as a reducing agent; chemistry aside, for our purposes this means it is much more reactive in Maillard reactions.

Various types of sugar and a thermometer

Caramelization and Maillard Reactions

Now a little background on what actually is occurring when sugar goes from white table sugar to brown or black tasty gooey syrup, so strap on your science hats (or science socks, whatever your flavor is).  There are in fact two completely separate classes of reactions going on, caramelization and Maillard.  Both processes are dazzlingly complex, having hundreds, even thousands of reaction products.  Many of these reaction products are detectable by us as various aromas and flavors that span practically the entire spectrum of sensory perception.

Caramelization is a process which requires only sugar and heat (though water helps facilitate and control the reactions and prevent scorching).  When the sugar is heated to a high enough temperature, the sugar molecules begin to break down into smaller fragments.  These fragments then recombine into numerous other chemical compounds (some of which can then go through multiple cascading reactions) which can be sour, bitter, aromatic, or just provide color.  According to McGee’s On Food and Cooking, some examples of these compounds include alcohols, acetaldehydes (sherry/ green apple), acetic acid (vinegary), diacetyl (buttery), ethyl acetate (fruity), furan (nutty), benzene (solvent), and maltol (toasty).

Sucrose has a very high caramelization temperature, but it will at least partially degrade into its component glucose and fructose at a lower temperature (especially in the presence of an acid), a process known as inversion.  So, caramelization and scorching will actually begin occurring at a lower temperature than you might otherwise anticipate.

Though Maillard reactions were discovered in 1910, they are still not completely understood.  What is known is that they require more than just sugar- amino acids are also needed.  If you believe McGee, the sugars can be bound up in a starch carbohydrate chain (though simple sugars tend to be more reactive), but I cannot find another source to back this up; every other source says reducing sugars are required.  Likewise the amino acids can still be bound up in more complex proteins, though higher temperatures are required; multiple sources confirm that more complex whole proteins can be involved in Maillard reactions (sugars build into starches, amino acids build into proteins- think links in a chain).

These amino acids add nitrogen and sulfur to the mix of carbon, hydrogen, and oxygen from the carbohydrates, making for even more complex compounds than found from caramelization.  Some example compounds given by McGee are peptides (savory), oxazoles (floral), various sulfur compounds (onions, meatiness), pyridines (vegetable), pyrazines (vegetable, chocolate, potato, earthy), and various caramelization flavors.  Before you think that these would be undesirable in beer, keep in mind that it is this set of reactions that gives rise to the toasty flavor in bread crust, the flavor and color in dark malts, chocolate, and coffee beans.  Chocolate coffee stout anyone?  Not without Maillard you don’t.

Both processes require extremely high temperatures before they become apparent due to the relatively immense amount of thermal energy required to break the molecular bonds before various reactions can occur and produce the byproducts which give rise to flavor, aroma, and color molecules.  Sucrose, for example, requires 330-340F (166-171C) before caramelization occurs.  Maillard products begin forming about 100F/ 55.5C below this, around about 230F/ 110C.  However, this is above the caramelization temperature of fructose, and some portion of the sucrose would have inverted to its component glucose and fructose (I read at some point somewhere 25-28% will invert even without acid, 40-70% with acid).  The upshot is you will be caramelizing some fructose at the same temperature as you are forming Maillaird products with your sucrose, making the two reactions hard to distinguish without some awfully shiny lab equipment (and probably a PhD or two).

Heating Sugar

You might be wondering how to get the sugar to 230 to 340F (110 to 171C) when its in a water solution.  As you probably know, once water reaches its boiling point (212F/ 100C at sea level), it will never get hotter unless its put under pressure (hence the idea of the pressure cooker).  But, the higher the sugar concentration in the water, the higher the boiling point goes.  In fact, this works with many impurities such as salt, though it takes an awful lot.  In the case of sugar, as the concentration goes up, so does the boiling point in a very predictable exponential curve.  At about 75% by weight sucrose, the boiling point will be 230F/ 110C, about the point Maillard reactions start to occur.  Nearing 100% sucorse, the boiling point will reach 340F/ 171C and the sucrose will caramelize.  Generally this is achieved by mixing the sugar in water and letting water boil away until the desired temperature is reached.

Part two will go into some of the approaches I used to (mostly not) make some belgian syrup of of my own.  Click here to read on >>

[Miniseries part one, two]

– Dennis
Life, Fermented

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