Christmas Candy Chemistry Part I: Caramels

I've often joked about someday writing a book called The Chemistry of Christmas. Many of the recipes I enjoy this time of year, mostly for candy, involve one or more aspects of chemistry. Even though "science" predominates with these recipes, the "art" of managing extraneous variables also plays an important role.
When it comes to candy making, some of these extraneous variables include the humidity in the atmosphere, the calibration of the thermometer you are using, the altitude, and even the rate at which you are raising the temperature. Another key aspect of candy making is to not substitute ingredients - for example using a low-fat substitute. The chemical structure of substitute ingredients will differ from the intended ones. As a result, the structure of the end product is unlikely to be what was initially intended.
Here are a few other tips related to candy making

• Use a heavy-bottomed pot. It needs to be one that will hold all of the ingredients without a risk of boiling over. A heavy material such as aluminum also conducts the heat evenly during the boiling process.
• Use a candy thermometer. We have had several through the years, and I currently use a digital one that clips to the pan. Yes, you can use the old-style method of evaluating how the mixture holds together in a cold water test. I prefer a more objective measure.
• Make appropriate adjustments for altitude. Remember that the boiling point for water is 212ºF at sea level, and it boils at lower temperatures as altitude increases. The temperatures for candy types are based on temperatures at sea level. Boiling to the specified sea level temperature results in increased evaporation of water and an end product that is going to be harder than desired. Here is a table with some guidelines for making adjustments based on altitudes. I will say that, through the years, as I have used different thermometers, I have also made multiple notes on my recipe cards regarding the final temperature that produces a candy consistency that we like.

STAGE	CANDY TYPE	DEGREES FAHRENHEIT
		Sea Level	2,000 ft	5,000 ft	7500 ft
Soft Ball	Fudge, fondant	234-240	230-236	224-230	219-225
Firm Ball	Chewy caramel	242-248	238-244	232-238	227-233
Hard Ball	Nougat, marshmallow	250-268	246-264	240-248	235-253
Soft Crack	Taffy, butterscotch	270-290	266-286	260-280	255-275
Hard Crack	Toffee, brittle, lollipops	300-310	296-306	290-300	285-295

• Do not allow your candy mixture to boil too quickly. This also alters the chemical structure and can allow crystals to form. You also run the risk of scorching your mixture and having it stick to the bottom of the pan. Use a medium low temperature and be patient as the mixture boils to the desired temperature. On another related note, don't decide to make candy if you are in a hurry to get somewhere else.

This caramel recipe is one I acquired from a friend over 20 years ago. It is one we have enjoyed year after year. I hope that you will enjoy it, too.

Ingredients:
1 cup butter (just use the real stuff!)
2 1/4 cups packed light brown sugar
1 cup light corn syrup (light in color not lite as in low fat)
1 can (14 oz) sweetened condensed milk
1 tsp vanilla

Coat the pan you will be pouring the caramel mixture into using butter or a non-stick spray. (This is one case where a low-fat option is acceptable.) I have a 7 1/2 x 11 inch pan that I have used with this recipe through the years. A 9 x 9 inch pan would also be just fine.

Melt the butter in a heavy 2-3 quart saucepan. Add the brown sugar and stir thoroughly, doing your best to ensure that the brown sugar dissolves into the butter. Stir in the corn syrup. Gradually stir in the sweetened condensed milk. Here is what the mixture will look like as it comes to a boil.

Cook the mixture over medium low heat, stirring occasionally. Boil until the mixture reaches a firm ball stage. We have found that at 242ºF produces a caramel of the consistency that we like. Of note, we also live at about 4,500 feet above sea level. 

Remove the mixture from heat and stir in the vanilla. I always like the sizzling sound as the alcohol burns off. 

Pour the mixture into the prepared pan and allow to cool.

 When cool, cut into squares and wrap in waxed paper. Here is what our pan of caramels yields.

The wrapping in waxed paper is my children's least favorite part of the process - probably because this is the task I assign to them. I tear off strips of waxed paper that are about 4-5 inches wide. I then cut the strips into thirds to get pieces the right size for the caramels.
Let me know if you try out this recipe. Stay tuned for another "Christmas chemistry" post next year.