There's a lot of physical chemistry involved in making old fashioned fudge. The recipe calls for combining and boiling milk, bitter chocolate or cocoa, and sugar together until the temperature of the syrup reaches 238 degrees F (114o C), pouring the seething mixture into a bowl, cooling to 115 degrees F (46 degrees C), and then beating until the surface shine disappears. If you don't follow the cautions in the recipe -- wash down the sides of the pan with a wet pastry brush or cover the pan for a few minutes early in the cooking process; don't scrape the pan; don't disturb the candy until it's cooled; don't let anything, even a speck of dust, fall into the cooling syrup -- you are very likely to wind up with a coarse, gritty mass instead of creamy fudge.
Sugar dissolves far less readily in cold liquids than in hot. There is no way that two cups of sugar will dissolve in a cup of milk at room temperature. Heating the sugar and milk mixture allows the milk to dissolve more and more sugar, and by the time the mixture is boiling, all the sugar is dissolved. The general principle is that at a particular temperature, a given solvent (in this case, milk) can dissolve only so much of a particular solute (sugar). When the milk has dissolved all the sugar it can hold, and there is still some undissolved sugar left, the mixture is said to be saturated. The higher the temperature, the more concentrated the saturated solution becomes.
Water (and milk) boil at 212 degrees F (100 degrees C) at sea level, but the sugar changes that. In general, a solid dissolved in a liquid makes it harder for the liquid molecules to escape. Consequently, the solution has to be hotter for the liquid molecules to get away at the same rate, and the boiling point rises.
In our fudge, the rise in boiling temperature is an exact function of the amount of sugar in the solution. Consequently, we can use the temperature of the boiling syrup to tell when enough water has boiled away to give the syrup the right ratio of sugar to water. For fudge and similar creamy candies, the syrup should boil at a temperature 26 degrees F (14 degrees C) hotter than the boiling point of plain water.
Some of the initial water in the syrup has now boiled away. Because the sugar couldn't dissolve completely until the mixture was near boiling, the syrup reaches saturation very soon after it starts to cool. If you've done everything right, however, sugar does not come back out of solution. Instead, the syrup continues to cool as a supersaturated solution. The solid phase -- in this case, sugar -- cannot start to crystallize without something to serve as a pattern, or nucleus. However, if a single sugar crystal is present, the syrup will start to crystallize, the crystals will grow steadily as the syrup continues to cool, and the result will be very grainy fudge.
This is why most fudge recipes require that the sides of the pot be washed down early in the cooking process, either with a wet pastry brush or by putting the lid on the pan for about three minutes to remove any sugar crystals clinging to the container walls. It is also why the recipes specify that the sides and bottom of the pan should not be scraped into the bowl where the candy is to cool. There is too much chance of scraping in a stray sugar crystal.
As the cooling syrup gets more and more supersaturated, its tendency to crystallize becomes even stronger. Even a speck of dust can start the process if all the candy contains is sugar, milk, and chocolate. Using more than one kind of sugar can counter this tendency. Most fudge recipes contain either corn syrup (which contains glucose instead of the sucrose of table sugar) or cream of tartar (which breaks sucrose into glucose and fructose). The different sugars tend to interfere with each other's crystallization and minimize the chance that the candy will crystallize too soon. They must be used in moderation, however -- too much and the fudge will remain a thick syrup forever!
The final stage is stirring the syrup when it is lukewarm to promote crystallization all at once throughout the candy. Disturbing (stirring) a very supersaturated solution causes many crystals to form at once. Because they compete with each other for the dissolved sugar, none can grow very large. The result is the proper creamy texture of fudge and the change in appearance from shiny (supercooled liquid) to dull (a mass of very tiny crystals).
FAQs
When making fudge, heat and acid work together to convert sucrose – basic white sugar – into its two components, glucose and fructose. When these sugars are present, they prevent sucrose from turning into big sugar crystals.
What is the principle of fudge? ›
Heating the sugar and milk mixture allows the milk to dissolve more and more sugar, and by the time the mixture is boiling, all the sugar is dissolved. The general principle is that at a particular temperature, a given solvent (in this case, milk) can dissolve only so much of a particular solute (sugar).
What is the composition of fudge? ›
fudge, creamy candy made with butter, sugar, milk, and usually chocolate, cooked together and beaten to a soft, smooth texture. Fudge may be thought of as having a consistency harder than that of fondant and softer than that of hard chocolate.
What is the chemistry of candy making? ›
In general, candy is made by dissolving sugar into water to create a solution. Granulated sugar, the most common type used in candy-making, is sucrose, a disaccharide molecule made up of glucose and fructose. When you force these two molecules to break apart, a very tasty reaction occurs: caramelization.
What causes fudge to turn to sugar? ›
Beating fudge when it's still over heat creates sugar crystals, aka the grittiness you feel in the fudge. Instead, wait to pick up the spoon (our Test Kitchen loves using wooden spoons) until the fudge drops to between 110 and 113°F, about 15 minutes.
What gives fudge its texture? ›
Tiny microcrystals in fudge are what give it its firm texture. The crystals are small enough, however, that they don't feel grainy on your tongue, but smooth. While you ultimately want crystals to form, it's important that they don't form too early.
What makes fudge hard or soft? ›
If there is too much evaporation, when the cooking time is too long, there will not be enough water left in the fudge and it will be too hard. Conversely, if the cooking time is too brief and there is not enough evaporation, too much water will remain and the fudge will be too soft.
What is the key to making fudge? ›
You have to control two temperatures to make successful fudge: the cooking temperature AND the temperature at which the mixture cools before stirring to make it crystallize. Confectionery experiments have shown that the ideal cooking temperature for fudge is around 114 to 115 °C (237 to 239 °F).
What is fudge technically? ›
Fudge is a dense, rich confection typically made with sugar, milk or cream, butter and chocolate or other flavorings. The base for fudge is boiled until it reaches the soft-ball stage (135 to 140 degrees F), then stirred or beaten as it cools to minimize the formation of sugar crystals.
How do you make fudge firmer? ›
Harden the fudge: Place your container or tins in the fridge for 2 hours, which is the time it takes for the fudge to set. Once it's hardened, cut the fudge into 12 pieces or remove it from the muffin tins. Store in the fridge or the freezer (if you don't devour it right away).
Fudge-making has evolved a variety of flavors and additives. The favored flavors vary by location: in the United States, chocolate is a default flavor, with peanut butter and maple as alternatives. When it is made from brown sugar, it is called penuche and is typically found in New England and the Southern States.
What's the main ingredients in fudge? ›
This delicious fudge recipe is easy to make in the microwave with just 3 ingredients: chocolate chips, condensed milk, and butter. Add nuts, mini marshmallows, or candy before chilling to make this treat even more decadent, or try peanut butter chips instead of semisweet chocolate chips to make peanut butter fudge.
How do you describe high quality fudge? ›
High-quality fudge tastes smooth and creamy because it contains small sugar crystals. It has a deep brown color and a satiny sheen. Poor-quality fudge tastes grainy because it contains large sugar crystals.
What is the physics of candy making? ›
To make candy, sugar is first heated to a high temperature so that it melts . The scalding solution is then then cooled into a solution that is supersaturated. The supersaturation is considered unstable, forcing the sugar molecules to crystallize into a solid.
What is the chemical formula for candy? ›
Did you know that most types of candy are made of sugar from two kinds of plants: sugar cane and beets? The common form of sugar is called sucrose (C12H22O11), a molecule made up from glucose and fructose (see front cover).
What makes fudge set up? ›
You have to control two temperatures to make successful fudge: the cooking temperature AND the temperature at which the mixture cools before stirring to make it crystallize. Confectionery experiments have shown that the ideal cooking temperature for fudge is around 114 to 115 °C (237 to 239 °F).
What is the interfering agent in fudge? ›
Corn syrup acts as an "interfering agent" in this and many other candy recipes. It contains long chains of glucose molecules that tend to keep the sucrose molecules in the candy syrup from crystallizing.
What is fudge usually made of? ›
Fudge is a dense, rich confection typically made with sugar, milk or cream, butter and chocolate or other flavorings. The base for fudge is boiled until it reaches the soft-ball stage (135 to 140 degrees F), then stirred or beaten as it cools to minimize the formation of sugar crystals.
What are the characteristics of fudge? ›
Characterised by its smooth, creamy texture and decadent flavour, fudge is typically made from a mixture of sugar, butter, and milk or cream. The ingredients are heated to the soft-ball stage, around 235-245°F (113-118°C), and then beaten while cooling, which gives fudge its characteristic smooth and dense texture.
