Sugar, Sugar!: A look at the functional role of sugar in baking.
A look at the functional role of sugar in baking
Written by Jenny Gusba
Sweeteners are one of the most important ingredients used in bakery foods. While there are many different sweeteners available, sucrose (or sugar) is perhaps the most versatile.
A large variety of sugars can be produced by extracting and purifying sugar from sugar cane and sugar beet. These sugars may differ in colour, flavour, sweetness, and crystal size. For example, the molasses in brown sugar gives it a different flavour and appearance compared to granulated white. Sugar can also be used in both crystalline and liquid forms. All of these characteristics contribute to the variety of functions performed by sugar in foods. Sugar not only makes foods taste sweet, it also has many other functions.
Sweetness is generally the most recognized functional property of sugar. The preference for sweetness is thought to be innate, appearing shortly after birth. Perception of the relative sweetness of sugar depends on factors such as temperature, pH, concentration, presence of other ingredients, and the difference in individuals’ ability to taste (e.g., detection threshold).
Sugar is an important contributor to flavour by interacting with other ingredients. Depending on the food application, sugar has the unique ability to heighten flavour or depress the perception of other flavours. In breads, for example, the resulting flavour typically is due to two processes that involve sugar: fermentation and crust browning.
In bakery products, sugar is recrystallized as water is removed during baking, resulting in a crisp texture. This crispness is increased by the effects of browning. Two different reactions are responsible for crust browning: caramelization and the Maillard reaction. Caramelization results from the melting of sugars to create a deep brown colour and new flavours. The Maillard reaction takes place when reducing sugars (e.g., glucose and fructose) and proteins are heated together.
The yellow-brown colours that developin baked foodscan be attributed tothe presence of sugar. Sucrose itself develops colour through caramelization.
In addition, sugar can be broken down into its two monosaccharide units (glucose and fructose), which can take part in the Maillard reaction and add to browning. Sugar also contributes to the colour of preserves and jellies through its capacity to attract and hold water. By absorbing water more readily than other components, such as fruit, sugar prevents the fruit from absorbing water, which would otherwise cause colour to fade through dilution.
Sugar acts as an important tenderizing agent in foods such as baked products. During the mixing process, sugar competes with other ingredients for water. In bread-making for example, the affinity of sugar to bind to water will delay the development of gluten, a protein in grains that is essential for maintaining a soft or tender product. Gluten strands, in general, are highly elastic, and this property allows the batter to stretch under the expansion of gases. Too much gluten formation, however, will cause the dough or batter to become rigid and tough. When the correct proportion of sugar is added in the recipe, an appropriate amount of gluten develops and optimum elasticity results. Sugars are also used in bread-making to prevent stickiness.
The physical functions that sugar contributes to foods include its solubility in water, its ability to lower the freezing point
and raise the boiling point. Solutions of varying sugar concentrations are important in many food applications, including the production of jellies and jams. Freezing point depression is an important property in ice creams, frozen desserts, and freeze-dried foods to ensure the development of fine crystal structure and product smoothness.
Microbial (Food Preservation and Fermentation)
Sugar plays an important role in extending the shelf life of bakery products. Sugar can bind to water molecules, slowing moisture loss and preventing staleness in baked goods. In addition, the glucose/ fructose mixture in invert sugar present in jams and jellies helps to inhibit microbial growth and, later, spoilage.
Fermentation, an extremely important process in the baking industry, is fuelled by sugars. Sugars are used to activate yeast for fermentation. The type and amount of sugar added can increase the dough yield and softness of bread by altering the rate of fermentation. When a hard crust bread is desired, sugars are either omitted or used in lower quantities. In this case, the yeast is activated by sugars formed when starch is broken down by enzymes present in the flour. Sugars remaining after fermentation contribute to the overall flavour, colour, and texture of the final product.
Sugar can act as an antioxidant in some food systems. It is able to block metal ions (e.g., copper, iron) and prevent or slow down oxidation reactions, which cause food to deteriorate.
Sugar can be used in nearly all baking applications, including yeast-based products, chemically leavened products, icings, and fillings. It plays a number of different roles in baking that go beyond the perception of sweetness.
Jenny Gusba is the director of nutrition and scientific affairs with the Canadian Sugar Institute, the national, non-profit association representing Canadian sugar manufacturers on nutrition and inter-national trade affairs. Find out more at www.sugar.ca .