Peanut brittle may seem like the simplest holiday treat, but it requires complicated chemistry to perfect.
Nothing characterizes the holiday season like the snap of a good homemade nut brittle or the stretch of a soft caramel. Like many traditions, this is more about grandparents pulling out their candy thermometers and gathering families into the kitchen than it is about the finished toffee or hard candy. But like any successful experiment in the lab, knowing the purpose of every reagent in these candy-making reactions is the key to ensuring a good outcome.
Peanut brittle relies on sugar in its non-crystalline form, so the first step to making it is to break down the disaccharide sucrose (common table sugar) to separate it into the monosaccharides that make it up—fructose and dextrose—which requires acid, water, and heat. As the sugar dissolves in water, the hydrolysis reaction will continue as long as the sugar and acid are in a fluid state, which depends on the amount of water present and how quickly it evaporates. You can control this by watching the temperature closely. For peanut brittle, start with a quantity of water that is 20-50% of the sugar by weight, and heat the solution over high heat.
As the water converts to steam, the monosaccharides begin to saturate the solution, increasing their tendency to form crystals and precipitate, which results in a gritty brittle. To prevent this, you need to interfere with the ability of fructose to rejoin dextrose. Once the solution reaches a boil, stop stirring it, since this can create cool pockets that promote crystallization. At this stage, it helps to add agents that chemically interfere with crystallization such as other monosaccharide sugars or acids. Acids tend to make syrups more prone to browning and more hygroscopic, making them soft and sticky. For brittles, glucose is the best option. Keeping the sides of the pot clean of crystals by brushing it with water can also help avoid crystallization as these crystals may seed crystallization in the solution.
Cooking is complete when the sugar reaches a certain level of saturation, which can be measured using a refractometer. But luckily for those of us who don’t keep a refractometer at home, sugar cooked to a certain temperature will always contain the same percentage of dissolved solids, so we can simply monitor our reactions using a candy thermometer. For peanut brittle, the proper level of saturation occurs at 110oC, which is where you can quickly stir in the peanuts (or substitute sesame seeds, other nuts, or cocoa nibs). Continue cooking, stirring constantly to roast the nuts and further saturate the sugar solution until the mixture reaches 155oC.
While 155oC is actually below the temperature at which sugar caramelizes, the amino acids present in the nuts contribute significantly to the Maillard reaction—a set of chemical reactions that browns everything from roasted squash to seared ribeye steak—speeding up flavor development.
When ready, remove the brittle mixture from the heat and add butter, vanilla extract, and salt to flavor your candy. Baking soda is also very important at this stage since it reacts to the heat, creating carbon dioxide that aerates the caramel, enabling it to snap when someone bites into it rather than requiring them to gnaw at it until it breaks or pulls apart. Baking soda also raises the pH of the mixture, promoting the Maillard reaction and giving the brittle its particular color and flavor profile.
Finally, pour the mixture onto a marble slab or cookie sheet so that it will cool quickly and evenly. You can stretch it as it cools if desired, or simply break it into pieces and serve it after dinner.
FAQs
Baking soda releases bubbles into our candy (you can see this on a more extreme level in my honeycomb recipe, which uses 5x the amount of baking soda!). This makes the brittle more delicate, crisp, and less chewy, which ultimately makes it more snappy and less likely to obnoxiously stick to your teeth.
Why didn't my peanut brittle get hard? ›
The main reason why peanut brittle doesn't get hard and have the crunch we expect is because the sugar was not cooked long enough. The sugar needs to be cooked to what is called the hard crack stage, 300ºF.
Why is my peanut brittle airy? ›
What is the purpose of adding baking soda to peanut brittle? Once you add the baking soda to the hot mixture, it bubbles up, and the mixture becomes somewhat airy.
How do you keep moisture out of peanut brittle? ›
#1 - Store in an airtight container
Keeping air out helps maintain your brittle's freshness by minimizing the amount of moisture that might come into contact with your sweet treat. In terms of material for your containers, it is totally up to your preference.
What makes peanut brittle too chewy? ›
Why did my peanut brittle turn out chewy? The likely cause is that the sugar mixture didn't reach the proper hard crack stage temperature. Ensuring it reaches 300˚F is key to getting that classic brittle texture.
How do you fix failed peanut brittle? ›
Why Is My Peanut Brittle Chewy / Sticky / Didn't Harden?
- Break up the brittle and place it in a glass, microwave-safe bowl. Heat on HIGH heat 1-2 minutes until soft and semi-melted. ...
- Transfer the semi-melted brittle to a a clean saucepan. ...
- Immediately remove from the heat and add additional 1/2 teaspoon of baking soda.
If you overcook the brittle, it could be bitter or burnt. If you undercook it, the brittle won't properly set and the end result will be sticky.
Should you refrigerate peanut brittle? ›
To store: Store peanut brittle (once it's completely cooled) in an airtight container at room temperature. Do not refrigerate as the moisture from the fridge will cause the brittle to soften. Store for 6-8 weeks. To freeze: Peanut brittle can be frozen and stored up to 3 months.
Does weather affect making peanut brittle? ›
I've learned that brittle is better when made on a cool, dry day. When I've made the candy on a warmer, humid day, it tends to be a stickier brittle. This is because the brittle takes longer to cool, and it reaches a point where it is no longer evaporating moisture into the air.
How do you keep peanut brittle crisp? ›
Once cooled and cracked, peanut brittle should be stored in an airtight container (it's okay to stack). Store in a cool dry place.
Peanut brittle has one redeeming quality: peanuts. Outside of that single ingredient, peanut brittle is painfully unhealthy. It contains: sugar, corn syrup, and butter, all of which are unhealthy for your body in different ways.
Why did my peanut brittle crystallize? ›
When candy cools slowly on a stone slab, more crystals have a chance to form. With a higher number of micro-crystals, the sugar has more sites on which to crystallize, and so crystallization ultimately happens faster.
Why add baking soda to peanut brittle? ›
Baking soda is also very important at this stage since it reacts to the heat, creating carbon dioxide that aerates the caramel, enabling it to snap when someone bites into it rather than requiring them to gnaw at it until it breaks or pulls apart.
Why is my peanut brittle hard but sticky? ›
What's important to know is that the corn syrup controls the grain of the brittle so adding too little and you have a grainy textured brittle, while adding too much will result in a stringy and sticky brittle.
What causes peanut brittle not to harden? ›
If your peanut brittle is too soft, you didn't cook it long enough. It's important to use a candy thermometer and cook the sugar mixture until it reaches the hard crack stage. Watch it closely…you may be tempted to take it off the stove sooner, but don't!!
What happens if you add too much baking soda to something? ›
Too much baking soda will result in a soapy taste with a coarse, open crumb. Baking soda causes reddening of cocoa powder when baked, hence the name Devil's Food Cake.
What happens if you put too much baking soda in peanut butter cookies? ›
Using too much baking soda or baking powder can really mess up a recipe, causing it to rise uncontrollably and taste terrible.
How does the amount of baking soda affect muffins? ›
More baking soda in a recipe doesn't necessarily mean more lift. You want to use *just enough* to react with the amount of acid in the recipe. Too much baking soda and not enough acid means there will be leftover baking soda in the recipe. You do not want that; it creates a metallic, soapy taste in your baked goods.
Does too much baking soda make cake hard? ›
How much baking soda can ruin a cake recipe? According to question, The amount of baking soda needed in a cake recipe can vary depending on the recipe and the other ingredients used. Using too much baking soda can make the cake taste bitter and have an unpleasant texture.
