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Sugar as a shelf life extender
There’s more to sugar than taste. Here we discuss how its unique water retention properties mean our food stays fresher for longer.
Why do we need sugar in our food?
Although its primarily used for flavour and sweetness, sugar’s functional properties mean it is an essential component in modern food production. Sugar is what’s known as a hygroscopic, meaning it binds water molecules very easily. In jams and preserves, this starves harmful bacteria of the water they need to grow, and in cakes and biscuits acts as a humectant, retaining moisture and preventing products from going stale.
What the current global trend for reducing the amount of sugar in foodstuffs fails to recognise is that these properties are unique to sugar and cannot easily be replicated by an alternative. Some manufacturers turn to artificial preservatives to try to replicate the same results. Potentially this is more detrimental to the consumer’s health than a naturally occurring product like sugar.
Producing products that sport a sugar free label pleases consumers and regulatory bodies, however, it oversimplifies the complex role sugar plays as a functional ingredient in food and beverages. Nearly all sugar free products do not retain the same taste, and the processes undertaken to ensure the preservative and humectant qualities are still present can lead to a less healthy product. Let’s now look at how sugar is used as a humectant in the food and beverage industries.
Why is sugar used as a preservative?
Sugar is used as a preservative in foods and beverages because it prevents microbial growth by reducing the water activity in a product, primarily through osmosis, or dehydration. Whether in solid or liquid form, sugar will always try to reach the same level of sugar present in the foodstuff it is in contact with. In order to achieve this, the water cells in the food product are replaced by sugar cells. Deprived of this water, bacteria find it extremely difficult to multiply and then spoil products.
In conjunction with this, sugar also disrupts the enzyme activities of microbes and weakens the molecular structure of their DNA. As a result, their ability to develop and inflict damage is limited, meaning products remain fresher for longer. Due to this, those foods and beverages that possess a high sugar concentration can be stored without refrigeration, conserving energy and negating the need for artificial sugar alternatives.
There are, however, some products, such as concentrated fruit juices, that can be spoiled by certain sugar-loving strands of yeast. These resist many traditional preservation methods and present considerable challenges to the food industry when looking to guarantee the maximum shelf life of products. Despite this, using sugar as a preservative represents an ancient and longstanding method to prevent microbial growth and stop foods spoiling.
How does sugar keep food moist?
Alongside hampering the growth of bacteria, the fact that sugar is a humectant means it is also used to retain moisture in food, such as in low fat baked goods like cakes, biscuits and bread rolls. The presence of sugar as an ingredient ensures water cannot escape quickly, preventing them from going stale and extending their shelf life. Due to their high affinity for water, invert syrups are typically used for this application.
Inverts can also take the place of glycerol as the humectant in cakes. This brings with it several added benefits, including improved colour, sweetness and more developed flavours throughout the baking process. As we have seen previously, replicating these and the above properties with a sugar substitute can prove to be highly challenging and not always possible.
More than taste: the functional role of sugar
Sugar is present in food and drinks for much more than taste and flavour. It plays a vital role in ensuring products remain at their optimum freshness for as long as possible by preventing the growth of harmful bacteria and retaining moisture. This is owing to its unique and powerful humectant qualities.
Such is the nature of the role that sugar plays, removing it entirely or swapping it for an alternative often throws up more issues than it solves. Artificial preservatives are typically chosen to fill the sugar void, which can potentially cause more harm than good. Sugar’s functional role in extending the shelf lives of the food and beverages we consume daily is important and should not be overlooked.