The Chemistry of Candy (from Hershey's Technical Center)

" Sometimes I think that the one thing I love most about being an adult is the right to buy candy whenever and wherever I want." Ryan Gosling
We all have these life moments, when we turn crazy about candy. It is like we want to go back to the time and memory when we were kids, and where we all we had to worry about was our next trip to the store to get some candy! Candy is all about bringing out these childhood memories. The sweet taste and the multi flavors from lemon, to strawberry and chocolate...etc can bring us - adults - some joy in this hectic world!
Apart of their bad health effects ( which I will not be talking about) , candy making is extremely entertaining to learn and know about !
It is a pure science on its own . Each candy has its own recipe and technicality!
I am sharing few knowledge I learned while I was in USA for training few years ago. As part of the training, we visited the technical center of Hershey in Pennsylvania, where we had to learn about the chocolate and candy making process straight from the scientists!


Candy is made from sucrose, the basic form of sugar.                                                 Sucrose is actually two simpler sugars stuck together: fructose and glucose.
Adding a little bit of acid
(for example, some lemon juice or cream of tartar) will cause sucrose to break down into these two components.
Combined with other ingredients,  sugar can wonderfully make candies as hard as lollipops, or as soft as fudge.
Chemically speaking, we can divide candies into just two main categories:

1.  Crystalline (have a  shape)
2. Non-crystalline (or amorphous i.e no shape) 

Temperature and Ingredients are 2 important factors in candy making

How do we do candy?

If  you want to cook up a batch of candy, you cook sugar, water, and various other ingredients to extremely high temperatures. At these high temperatures, the sugar gets dissolved in the solution, even though much of the water has boiled away.
As it boils away, there would be alot of sugar in the solution and thus, candy starts to harden.
Stirring or jostling of any kind can cause the sugar to begin crystallizing.

Candy shaping in Hershey's

Type of Candies:

Sugar solidifies into crystals is an extremely important step in candy making. There are basically two categories of candies - crystalline (candies which contain crystals in their finished form, such as fudge and fondant), and noncrystalline, or amorphous (candies which do not contain crystals, such as lollipops, taffy, and caramels). The formation of sugar crystals is not desirable, because they give the resulting candy a grainy texture.

Crystalline Candies

 Generally smooth & creamy. Crystalline candies  contain crystals of sucrose in their finished form; the  sucrose molecules are able to align and form large  lattices. They are best formed by slow cooling of a  sugar solution, without stirring, which can disrupt  crystal formation.

Non- Cyrstalline Candies

Generally hard & brittle. Non-crystalline, or
amorphous candies, form when crystallisation
is prevented. This can be accomplished by the
addition of sugars such as glucose and fructose that interfere with the development of crystals. Often,  their mixtures are too viscous for crystals to form.
Crystals are undesirable in some candy recipes—and how do you stop them from forming?
By simply adding Interferring agents in Candy Formation, thus preventing crystals to form. 
One way to prevent the crystallization of sucrose in candy is to make sure that there are other types of sugar—usually, fructose and glucose—to get in the way.  HOW?: 2 ways:

1. A simple way to get other types of sugar into the mix is to "invert" the sucrose (the basic white sugar you know well) by adding an acid to the recipe. Acids such as lemon juice or cream of tartar cause sucrose to break up (or invert) into its two simpler components, fructose and glucose. 
2. Another way is to add a non-sucrose sugar, such as corn syrup, which is mainly glucose. Some lollipop recipes use as much as 50% corn syrup; this is to prevent sugar crystals from ruining the texture.
3. Adding Fats in candy serve a similar purpose. Fatty ingredients such as butter help interfere with crystallization—again, by getting in the way of the sucrose molecules that are trying to lock together into crystals. Toffee owes its smooth texture and easy breakability to an absence of sugar crystals, thanks to a large amount of butter in the mix.

Source: http://www.compoundchem.com/2014/10/21/chemistryofcandy/