The Basics

The functional role of sugar in food

    • Sugar is not only added to food for taste, but also for functional reasons
    • Sugar alternatives or low sugar foods may not be 'healthier'
    • Removing sugar can be technically challenging

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Aside from making some foods more palatable and providing kilojoules, sugar has a number of important properties that contribute uniquely to a food’s appearance, texture and shelf-life. It’s therefore an important ingredient in both the foods we make at home, and the manufactured foods on our supermarket shelves. Reducing or removing sugar from a product often requires replacement with a number of substitute ingredients to achieve the same quality, taste and texture profile. Below are some of the important roles sugar plays when it is added to foods:

As a bulking agent – sugar contributes to the texture of food, such as in meringue and biscuits.  This is an important role of sugar in most baking applications.

As a preservative – sugar helps to prevent or slow the growth of bacteria, moulds and yeast in jams and other preserves. It also helps to prolong the shelf life of many foods on our supermarket shelves by acting as a humectant – maintaining and stabilising the water content in foods.

Enhancing flavour – adding a little sugar to nutritious foods such as sour fruits (frozen berries or rhubarb), or porridge, helps to make them more palatable.  Sugar also enhances fruit flavours in foods.

For colour – on heating, sugar breaks down to produce the colour and desirable flavour that characterises many cooked foods. This is caused by sugars reacting with proteins as they break down in the cooking process, called the maillard reaction. A sprinkling of sugar and cinnamon on top of fruit muffins makes for a browned crunchy topping and gives a nice texture.

Adds viscosity – sugar provides body in drinks and semi-liquid foods like syrups, chutneys and sweet sauces.

As an anticoagulant – when it’s heated, sugar delays the coagulation of proteins (or the change to a semi-solid state), such as in baked custards and other desserts.

Implications of removing sugar from foods

Food and beverage manufacturers world-wide are looking for ways in which they can reduce the sugar content of their products in response to perceived consumer demand. This often poses some technical barriers due to sugar’s role in providing more than just taste.  

This complex combination of texture and taste makes the reduction or elimination of sugar more challenging than simply dropping a non-nutritive sweetener into a product in place of sugar. Even a straight swap involves significant challenges with getting the appropriate flavour and stability in foods exposed to high temperatures.

Sugar also provides bulk, density, and viscosity in food products. Therefore removing or reducing sugars from high-sugar-containing products and replacing them with lower energy sweeteners requires that they be replaced by other molecules that can control these physical changes in the product.  A variety of bulking agents such as insoluble fibres (gum systems) and polydextrose can be used, though these do not all reduce the energy content of the food (which is often the original intention of reducing sugar content).

Sugar also reduces the water activity in foods and beverages, making water unavailable for use by bacteria and fungi, thereby reducing microbiological activity and mould formation.  For this reason, many foods and beverages containing high concentrations of sugars do not need to be refrigerated. When sugar is removed from a product, or replaced with a non-nutritive sweetener, its preservative properties are lost.  Preservatives may therefore need to be added to these products, which is often less acceptable for consumers.

In breakfast cereals, sugar often plays an important functional role other than taste.  Small amounts of sugar provide lubrication for “dough” being processed into extruded breakfast cereal products. It’s also used for helping to bind pressed and moulded products such as Weetbix.  Simply removing sugar from these products would necessitate the use of other, less “natural” compounds in order to make the same product.

This may partly explain the difficulties faced by manufacturers when carrying out sugar reduction or replacement programs.

By Pat Silcock

For more information on the role of sugar in food, see the infographic 'Why is sugar in my food'

[Pat Silcock is the Manager of the Product Development Research Centre in the Department of Food Science at the University of Otago. He is also an independent advisor to the Sugar Research Advisory Service.]

 

NEXT: Sugar terminology

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