Fructose is a fruit sugar that occurs naturally in fruit and vegetables and it is a key component in table sugar. It is a mono saccharide, also known as a simple sugar, and it is added to many processed and pre-prepared foods such as yoghurts and sauces to make them sweeter.
It is also one of the key components of honey, alongside glucose. The fructose is sweeter than glucose, which is why many people choose to use honey as a substitute for sugar as they can use less to achieve the same taste.
Fructose was first discovered in 1847 by a French scientist called Augustin-Pierre Dubrunfaut, who also discovered maltose. It wasn’t until 1857, however, that an English chemist named William Allen Miller came up with the name fructose.
Fructose is the most soluble of the sugars and will fully dissolve in very small amounts of water. Its unwillingness to form crystals makes it suitable for soft sweets. It also absorbs moisture well and retains it effectively, making it an ideal ingredient for use in baked goods.
Where does fructose come from?
Fructose is a naturally occurring sugar, but it can also be extracted to be used on its own. Some fruits have high levels of fructose, including grapes, pears, mangoes, apples and watermelon, and there are some high-fructose vegetables as well, including peas, asparagus and courgettes.
Almost all root vegetables contain sucrose, including carrots and parsnips, but one of the most notable is the sugar beet. These are grown and harvested for the commercial production of sugar. The beets are harvested, washed, sliced into thin strips and then the sugar is extracted using a process called leaching. The remaining by products are pulp and molasses, both of which are used as sweeteners.
Sugar cane is also grown in order to extract the fructose, although they are also a rich source of sucrose. Fructose can also be extracted from corn, and is usually found in the form of high-fructose corn syrup which is a combination of glucose and fructose and is added to a number of commercially produced drinks and desserts.
Fructose in fermentation
Along with glucose and fructose are the two sugars in wine must that ferment when combined with yeast. The process converts the sugars, most of the fructose turns into alcohol and carbon dioxide.
Wine scientists, or oneologists, study the strains of yeast that are more likely to consume glucose over fructose, tracing their DNA to ensure that they use those that maintain an even glucose/fructose ratio. Yeast strains that consume fructose effectively are known as fructophilic, and are a highly sought-after in the wine industry.
Fructose-based fermentation can also be used to make kombucha and can be added to batches that have already been fermented in order to add fizz and a sweet taste. Fructose can also be added to lactic acid fermentation recipes in order to speed up the process of fermentation. It can be used in kefir, often in the form of fruit juice, to add a little sweetness and aid the fermentation process, and it can be added to sauerkraut to increase the production of acetic acid.
Other uses of fructose
Fructose can be used as a sugar substitute, and it is a popular choice because it is sweeter than sugar and so quantities can be reduced. It is vegan, kosher and halal, so it can be used in recipes to suit a wide range of dietary requirements.
Once dissolved, fructose does not easily recrystallise, so it can be used to prevent crystallisation in other foods such as honey. Sprinkling fructose over fresh fruit helps prevent ice crystals from forming when freezing it.