The Importance of a Candy Thermometer
Sugar has very specific cooking stages between the temperatures of 230ºF-350ºF (110ºC-177ºC). Precise temperature control, understanding what’s happening to the sugar, and being aware of how to avoid crystallization are things you need to know. A Thermapen, along with some easy tips will give you the tools necessary to make your next sugar project a sweet success.
With fall equinox and a mega harvest moon behind us, fall is officially here—and it’s apple season! If you have your own apple trees, or live near an orchard, chances are you have apples by the bushel that need to be put to good use. Allow us to suggest a seasonal favorite: Caramel Apples!
Ditch the store-bought wrapped caramels this year, and make your own caramel for dipping. Making caramel involves cooking sugar, which can be intimidating; but once you understand some critical points in the sugar cooking process and you’re equipped with the right tools, it’s easy.
A couple of the most common problems with cooking sugar are
1) it can crystallize while its cooking and become gritty, and
2) if it’s overcooked it becomes bitter
Inversion: During the sugar cooking process, the sugar (sucrose) is transitioning from a granular state to a liquid state. As water and heat are applied to the sucrose, it dissolves and splits into fructose and glucose. These two sugars each have unique flavor qualities, and are what give caramel its characteristic flavor.
But sugar molecules have a tendency to revert back to their crystalline form and, given the chance, they will do so quickly. That’s why it’s so important to take measures to ensure that doesn’t happen.
Burning: Once you’re into the high temperature caramel-stages of sugar cooking, care needs to be taken to monitor the temperature—don’t walk away! If you like caramel that tastes deep and robust, you can push the temperature up to about 380ºF (193°C); but once the temperature increases beyond that point it can burn, resulting an an unpleasant bitter flavor that cannot be fixed. At these high temperatures Rose Levy Beranbaum says in her book The Baking Bible, “The darker you make your caramel, you risk burning it if you don’t have an absolutely accurate thermometer.” Keep your Thermapen ready to go.
A couple of tips can make cooking sugar foolproof.
Tips for Perfect Cooked Sugar
1. Keep it Clean: Always start with extremely clean tools. The presence of any dirt, dust or other debris in the pan can adhere to sugar crystals, later providing the seed for re-crystallizing the entire batch. After initially stirring the ingredients, use a clean pastry brush dipped in water to wipe clean any sugar crystals that may be stuck to the sides of the pan. You can continue to brush down any sugar crystals you may see during the whole cooking process, or try the cover method listed below.
2. Catalyze it: Once water is added to the sugar in the pan and mixed in, it’s time to add an already inverted sugar like corn syrup or glucose (or an acid like lemon juice or cream of tartar) to catalyze the inversion process. The corn syrup or acid will interfere, and help keep the sugar solution from crystallizing.
3. Cover it: In a post from the LA Times on Keeping Sugar From Crystallizing, we found this tip to be very helpful:
“Cover the pan loosely with a lid or baking sheet. As the sugar cooks and the water evaporates, a loose lid works to temporarily trap the steam in the pan; the steam will help keep the sides of the pan clean, much like using a moistened pastry brush. Keeping the lid ajar will allow some steam to escape as the sugar continues to cook.”
4. Don’t Stir: Once your ingredients are mixed (whether or not the pan is covered), it’s important to let the sugar solution cook undisturbed over medium to medium-high heat until it reaches your target temperature. As the sugar approaches its desired finished temperature, reduce heat to no higher than medium. Again, resist the urge to stir the sugar. Agitating the solution can cause crystallization, so just let it be.
5. Stop the Cooking: Bringing the mixture all the way up to your target sugar temperature, and then stopping the cooking process immediately once it’s reached, is critical to your success. Just like carryover cooking with meats, there is a strong carryover that can occur with your sugar because of the latent heat in the bottom of the pan that was directly against the heat source. This is a point where it’s easy to take your beautiful amber-colored sugar from delicious to bitter in seconds.
Have a bowl of cold water at the ready right by the stove, and as soon as your target temperature is reached, plunge the bottom of the pan into the cold water to immediately stop the cooking.
You may have noticed that there is a bit of a paradox in the above steps. You don’t want to stir the sugar mixture while it is cooking for fear of inducing crystals. At the same time, you need to know precisely when your sugar mixture has reached your target temperature so you can get it off the heat. This is where having the right thermometer is so important. Let me explain why…
Temperature is Key – Pick the Best Candy Thermometer
Thread (230ºF-235ºF/110ºC-112.8ºC), soft-ball (235ºF-240ºF/113ºC-116ºC), firm-ball (245ºF-250ºF/118ºC-121ºC), soft crack (270ºF-290ºF/132ºC-143ºC) and hard crack (300ºF-310ºF/148ºC-154ºC), caramel (320ºF-350ºF/160ºC-176ºC)—what does it all mean?
There are several stages of sugar cooking, and the sugar has different qualities at each stage. Generally speaking, the higher the temperature of the sugar, the more firm it will be once cooled. The stages have very specific temperature windows, and just a couple of degrees out of that window can mean the difference between a kitchen success or a flop. There is a great go-to chart of sugar cooking stages and temperatures on our website you can reference.
Which Thermometer? We suggest using a Thermapen to check the temperature of your sugar. A leave-in probe thermometer such as the ChefAlarm may seem like the obvious choice so you can constantly monitor the temperature; but we find that the presence of the probe actually creates an area where sugar can attach and crystallize (think back to growing rock candy sugar crystals when you were in elementary school), just like the presence of any dirt or debris would. An infrared thermometer doesn’t disturb the sugar at all; but since it only measures surface temperature, it isn’t quite the right choice either. A Thermapen will measure the internal temperature of the sugar, and its response time is so fast that you’ll be able to check the temperature in an instant—perfect as the sugar’s temperature increases quickly. Test the temperature periodically so you can be sure to hit your target temperature every time.
The Kitchen Project
We followed Martha Stewart’s recipe for Classic Caramel Apples. This recipe uses a fair amount of corn syrup, and as we learned earlier, it will help prevent sugar crystallization.
Prepare your apples first. We have a couple of helpful tips on preparing your apples. The goal is a tasty, crisp apple with caramel that hasn’t slid off the apple. We chose local organic gala apples for the project; but you can really use any apple that you like. Some people prefer granny smith, some prefer gala or fuji. It’s up to you. Now for the tips:
- Chill the apples overnight: Dipping cold apples will help the caramel set up immediately, rather than sliding off the apple.
- Sand the apples: Yep, you read that right. You’re going to use some fine-grit sandpaper from the hardware store. We found this Caramel Apple Tip from thekitchn.com. Just like preparing a wooden surface for painting, the sanding will create a bit of a rough surface on the apple skin for the caramel to attach to.
- Insert Sticks: Use candy sticks, popsicle sticks, or twigs, and insert them directly through the center of your apple keeping it at a 90º angle from the sheet pan. Be sure to dab away any juice that may drip out when you insert the sticks. The presence of moisture will keep the caramel from adhering to the apple.
Making the Caramel:
- The sugar, cream, corn syrup, and butter are all combined in the pan, brought to a boil and allowed to simmer until it reaches 245ºF (118ºC), or firm ball stage. This will likely take about 10-12 minutes. Use your Thermapen to periodically check the temperature of your sugar mixture. This is the stage where you can make soft, chewy caramels. Oddly enough, it isn’t the actual caramel stage of sugar cooking. That doesn’t come along until the sugar is over 300ºF (149ºC).
- Once your sugar mixture has reached 245ºF (118ºC), immediately submerge the bottom in a cold water bath to stop the cooking. If the sugar temperature continued rising, the caramel would likely pull out your crowns and fillings.
- Dip your prepared apples to completely coat them. Let the apples set up on a parchment paper lined sheet pan until set—about 15 minutes.
A recap of tips for successful sugar cooking:
- Use very clean equipment
- Add a catalyst
- Brush the inside of the pan with water
- Cover it
- Don’t stir
- Check the temperature periodically with a Thermapen (no leave-in probes)
- Immediately stop the cooking by the use of a water bath once the target temperature is reached
Grab some apples and your Thermapen, and start dipping!