Homemade Xylitol Candy Explained
Welcome intrepid confectioner, on this page I'll explain why many people believe you cannot make good xylitol hard candies at home and why many procedures fail. If you are looking for my DIY instructions and not the explanation then you want to go to Homemade Xylitol Candy for the how to and recipe.
Sucrose vs Xylitol
Sucrose is a disaccharide which means it is composed of two sugar molecules, anyone familiar with candy making knows that you start by adding water to the sugar and begin heating. The first thing to happen is that the sugar dissolves and as the syrup begins to boil the water is removed. When the water has nearly completely evaporated and the temperature continues to rise you hit the critical stage. If a stray sugar crystal gets in or you are just very unlucky the whole pot of sugar can suddenly crystallize, which will be immediately followed by scorching, burning and you starting over.
To prevent this problem confectioners often take out "insurance" by adding a little acid like citric acid from lemon juice which helps cleave some of the disaccharide bonds or just add high fructose corn syrup ... both methods work by adding impurities to the mixture that makes it difficult for the sucrose to crystallize.
As the temperature increases you get more and more impurities until you reach a point that the sugar simply can no longer crystallize ... and there is rejoicing. For as it turns out sucrose has many useful and tasty liquid states that can still form hard candies.
Xylitol however, is very different. It's a monosaccharide which will not mean much to anybody except that there are no disaccharide bonds to cleave AND when heated too high instead of forming yummy caramel flavors it produces a yucky kind of burnt bitter flavor AND even a small amount of these burnt impurities make it very unlikely to crystallize and more likely to remain a runny syrup consistency.
The Problems
You need to heat xylitol just enough to melt it but not so high that it begins to decompose thermally. To make matters more difficult you need to do this without adding water {I'll explain that in a bit}. So in essence you need to reach that critical stage, without the help of any liquid and keep it there. THEN you need to prevent it from crystallizing too quickly or you will have a sugar cube like texture AND if you add too much or the wrong flavorant it will never harden.
The Solutions
Extremely good thermal regulation with very slow initial heating, addition of good flavorants {this is just hit or miss experimentation} and lastly good thermal regulation while cooling and without crystallization until you initiate it.
The only serious barrier to home xylitol candy making is the initial heating step and this is where most procedures/recipes fail.
As mentioned earlier, when making hard candies with sucrose {table sugar} you first add water then upon heating the sugar dissolves and you evaporate the water until it's all gone. Unfortunately xylitol has a melting point of 197.6°F (92°C) which is below the boiling point of water 212°F (100°C). By itself this doesn't mean much but xylitol is one of the sugar alcohols and contains five alcohol functional groups {aka hydroxy moieties} making it a very polar liquid like water and making it much more difficult to drive water away even when heated above the boiling point. Think of this like adding alcohol to a dish you can drive off most of it with heat but some always remains. Unfortunately just a tiny amount of water will make your hard candy sugar cube like.
What this all means is that realistically you cannot use water when starting your xylitol heating or atleast not in the way you would for sucrose. Instead you need a very slow, very even constant heat that does not go too much above the xylitol melting point of 197.6°F (92°C). If you try using a hot plate with a thin metal pot you will scorch the xylitol on the bottom before it can all melt and that little bit of scorching will prevent the final product from crystallizing properly
Alternatively melting the xylitol over a double boiler would seem like a good option, however, the melting point is so close to the boiling point of water that you need a roaring boil AND some way to keep the water vapor out of your melting xylitol. Surprisingly this is not that hard. I've used a canning jar with a pinhole in the lid, Glad Press 'n Seal again with a pinhole in the lid {the pinhole lets the pressure out} and both work though I found it's easiest to just put a plastic bag over the jar top and hold it there with some rubber bands or twist ties. Just be very careful to dry the tops and keep any moisture out of your liquid xylitol.
Another method that works is to use a heat diffuser like cast iron and just be very very careful to heat everything slowly and not too high. Ideally you would use an induction heater with an appropriately magnetic pot and a checked and calibrated heat setting ... seriously the temperature setting on those things is theoretical and depends on the pot you use so don't trust it.
The Hard Truth
So you are probably asking why didn't I mention any of these methods before? Well they work but they all kind of suck. I mean if you really want to you can get an electric skillet and slowly heat everything until you get the liquid xylitol but it takes forever and you are constantly having to stir and check for hot spots and even the hot water bath is a pain and I tried vacuum sealing the xylitol into a pouch, with a flavorant and then dropping it into boiling water. If you work fast and have good gloves {I use welding gloves} this method is ok but it's still wasteful, a lot of work and kinda sucks.
Large Scale Methods that Do Not Suck
Crock pots! You need to experiment with what you have available but in many ways they are like big coffee cup warmers. The thick ceramic insert diffuses the heat so you are unlikely to scorch anything BUT you probably wont be able to fill it all the way up since the filled crock final temp is often below the melting point of xylitol. I haven't tried this on that large a scale but I have a tiny crock that works. Unfortunately this is a hit or miss system and you will need to check what you have available and make sure it is suitable. I recommend just heating water first and measuring the temperature at different levels to get an idea of how much xylitol you can add. Also keep in mind you probably want a cheap crock, the more expensive ones have heat sensors that will likely turn the thing off too soon. Tip use a digital probe thermometer with the tip on the bottom of the pot ... I do this because I don't know what the final temp of my crocks are and it's good to be safe when you are working on larger scales.
Use your oven, this is the method anyone should be able to use for large scale. Be sure you have an accurate thermometer, AND your cooking vessel needs to have enough mass that it evens out your ovens thermal cycling and any hotspots before the xylitol can burn. Convection ovens are the best and chinese clay pots or ceramic cast iron with covers are very good choices {Do NOT use regular cast iron}. Success can also depend on where in the oven you place the container ... try to center your vessel and make sure it is not too close to an active heating element.
The magic number is 250°F (121°C). If you can melt your xylitol without ever letting it come in contact with anything above that temperature, you're safe for hours ... literally.
Most heating methods involve high heats and letting the temperature even out in the materials. This is why cheap pots often scorch the bottom while expensive "clad" pots don't as much. Unfortunately "clad" cooking vessels are not good enough for xylitol.
What Should you do First
Try my Homemade Xylitol Candy protocol first. Everything was designed to give first time users the best chance of creating a good product with cheap and probably already available materials. Here's why:
- Coffee cup heaters are designed to keep common volumes of coffee at a constant non-boiling temperature which means they are fairly uniform AND happen to be cheap {mine was $1 at GoodWill}. Without a load the heating surface gets to be 310°F which is too hot BUT with a glass container and ~25g of xylitol the temperature is just about perfect ... try to keep the temperature 230°F to 250°F (110°C to 121°C)
- Use a small glass container because glass is an insulator and the heat from coffee cup warmers can be just a little too high. Glass also has a high heat capacitance and will help diffuse the heat evenly. If you use metal and are very careful it will work but if you use a little glass container {I'm using an old Lee Kum Kee bottle now but an 8oz mason jar is fine} you do not need to be careful.
- Parchment paper because many flavorants like Kool-aid are acidic {citric acid} and react with aluminum ... it still works but there are many reasons why parchment paper is better. Do not even consider wax paper ... it will make a horrible mess.
- Use 25 grams because that's a good amount that will completely melt and probably wont overheat if you forget about it. It also happens to be about 2 tablespoons. Don't try to overload the little heater, the liquid should be close to 250°F when you pour, if it gets below 230°F you'll start having problems.
- The 13 inch parchment pour moulds are the perfect size to hold 25g of melted xylitol. More xylitol and you will have heat dissipation and size issues ... seriously the sizes and quantities were chosen for many reasons.
- Pour and do Not scrape out the last little bits. The liquid xylitol is hot enough to melt the few crystals on the side while you are pouring but when you try to scrape out the last bits you will just end up seeding your liquid too soon. Also note that 230°F snippet above.
- Try casting the sticks before trying other shapes or moulds! This method uses a slow crystallization procedure and xylitol contracts {shrinks} as it crystallizes. When you pour the liquid xylitol into the moulds the top tends to be convex. As it cools and crystallizes the top becomes concave. This is a good thing! otherwise you would get a lot of voids and "pipes".
There is away to avoid the shrinking problem AND make it all crystallize much faster but it is very tricky at this scale and I will write it up at some later date ... this DIY is supposed to be as simple and inexpensive a protocol as I could come up with.
I wish I could guarantee everyone success in this but there are many many factors that can change things. I do promise that it is possible to make good xylitol hard candies AND this is the procedure I use. Really it's very forgiving, +/- a few grams is fine and I use the coffee cup warming method because it's trivial and there is virtually no risk of burning anything. I actually let it sit heating for 2 or 3 hours to make my 20ppm colloidal silver xylitol candies {it takes that long for the water to finally evaporate}. Also it takes freakin forever to completely melt xylitol in the oven.
