Hard candies are a delightful category of confections that are known for their solid, crystalline structure and long-lasting sweetness. These candies are typically made by boiling sugar and other ingredients to create a concentrated syrup, which is then cooled and allowed to harden. They could be more specifically defined as a concentrated carbohydrate solution in which most of the water has been removed (final moisture content around 1–3%) and that has been cooled below its glass transition temperature (Tg) quickly enough that sugar crystallization cannot occur. Therefore, hard candy is an amorphous glass, of a similar molecular nature as window glass, made from sugar while a window glass is made from silica.
The primary ingredient in hard candies is sugar, which is often combined with corn syrup to prevent crystallization and enhance the candy's smooth texture. The type of sugar used can influence the texture of the candy. Granulated cane sugar is a common choice, but some recipes may use specialty sugars like beet sugar or invert sugar for specific properties. Natural and artificial flavorings are added to create a wide range of tastes. Additionally, food coloring may be used to achieve the desired color. Organic acids can be use too to enhance fruit-like flavors.
The production of hard candies involves several specialized technologies to ensure efficiency, precision, and consistency in the manufacturing process.
Cooking and Heating Systems: Modern candy manufacturing facilities are equipped with large, automated cooking and heating systems. These systems use steam or electric heat to precisely control the temperature of the sugar syrup during the cooking process.
Vacuum Cooking: Vacuum cooking is a technology used to reduce the boiling point of the sugar syrup, allowing for more precise temperature control. It also helps remove unwanted impurities and air bubbles from the syrup, resulting in a smoother, higher-quality candy.
Mixing and Blending: Industrial mixers and blenders are used to uniformly distribute flavors, acids, and colorings throughout the candy mixture. These machines ensure consistent taste and appearance.
Shaping and Forming Equipment: Candy shaping and forming equipment vary depending on the desired final product. This can include mold-filling machines for specific shapes, extruders for creating ropes or sticks, and batch roller and rope sizers for creating bite-sized pieces. These machines are often automated and can handle high volumes.
Cooling and Solidification: Cooling tunnels are used to efficiently cool and solidify the shaped candy. These tunnels control temperature and humidity to optimize the crystallization process, resulting in the desired hardness and texture.
Very important at formulating hard candy is to use enough water whether from corn syrup or extra water addition to assure sugar crystals complete dissolution. Typically, about
30–35% of the batch is water.
Invert Sugar or Liquid Glucose: Up to 5% by weight - Can be used in place of, or in addition to, corn syrup for improved texture and moisture control.
Glycerin: Up to 1% by weight - Can be added to improve texture and reduce crystallization.
Most common shelf life issues in hard candy are:
To extend the shelf life of hard candies, manufacturers often use moisture-resistant packaging, employ moisture control techniques during production, and store the candies in a controlled environment with stable temperature and humidity conditions.