Glucose syrup (also known as starch syrup or corn syrup) is a concentrated solution of sugars and dextrins obtained by the incomplete hydrolysis of starch — most commonly from corn or potato. It is a sweet, thick, viscous liquid, typically clear and colorless to pale yellow. With a standard total solids content of around 78%, glucose syrup is one of the most important ingredients in confectionery, bakery, and many other branches of the food industry.
Production of glucose syrup
Glucose syrup is produced by breaking down starch molecules using diluted acids (hydrochloric or sulfuric), enzymes, or a combination of both. The starch slurry is heated under controlled conditions to achieve the desired degree of hydrolysis. After saccharification, the resulting syrup is purified, filtered, and evaporated to the required concentration — typically 78% total solids. The depth of hydrolysis determines the ratio of glucose to dextrins in the final product: a deeper process yields more glucose and fewer dextrins, resulting in a higher proportion of reducing sugars.
Types of glucose syrup
There are three main types of glucose syrup used in food production:
- Low-conversion (low-DE) syrup — contains 30–33% reducing sugars. It has a high proportion of dextrins, giving it greater viscosity and a mild sweetness. This type is preferred in caramel and hard candy production because it resists crystallization effectively.
- Regular conversion syrup — contains 38–44% reducing sugars. This is the most commonly used grade for general confectionery applications, including caramels, toffees, and fondant.
- High-conversion (high-DE) syrup — contains 44–60% reducing sugars. With more glucose and less dextrin, it is sweeter and less viscous. It is used where higher sweetness and humectant properties are needed.
Functions in food production
Glucose syrup performs several important technological functions. As an anti-crystallizer, it slows down or prevents the crystallization of sucrose solutions by increasing the viscosity of the syrup. At high dosages, crystallization may not occur at all — a property essential in the manufacture of caramel, toffee, and other non-crystalline sugar masses. Glucose syrup also controls the hygroscopic properties of confectionery products: it helps items like gingerbread and soft cookies retain moisture and resist drying out. In yeast-leavened products, it promotes greater volume, improved crumb porosity and elasticity, better crust color, and slower staling.
Maltose syrup
Maltose syrup is produced by enzymatic saccharification of starch-containing raw materials — primarily corn. After filtration, the syrup is evaporated to at least 78% total solids. It has a sweet taste with a distinctive malty flavor and aroma, and a characteristic brown color. The reducing sugar content is at least 65%, with maltose as the dominant sugar. Maltose syrup is valued in brewing, bakery, and confectionery for its mild sweetness and flavor contribution.
Refinery syrup
Refinery syrup (also called refiners’ syrup) is a byproduct of sugar refining. It is a uniform, clean mass with a dark cherry color and a sweet taste with caramel and slightly bitter-malty notes. While less commonly used than starch-based syrups, it finds application in dark-colored confectionery products and some baked goods.
Storage
Glucose syrups should be stored in steel tanks or metal drums at a temperature of 12–14 °C, protected from direct sunlight and atmospheric moisture. Under proper conditions, starch-based syrups maintain their quality for extended periods without significant changes in composition or appearance.