Fructose is another common monosaccharide, also known as fruit sugar. It is the sweetest natural carbohydrate, with a sweetness 1.8 times that of sucrose. It is abundant in some very sweet natural foods, such as lychees, honey and mangoes. Fructose is also present in sucrose which is a disaccharide composed of fructose and glucose. Honey is the most concentrated source of monosaccharides in nature. The fructose in honey comes from the hydrolysis of plant sucrose. It contains about 40% fructose, 30% glucose, 7% maltose and about 20% water.
In the 1970s, technology was developed to manufacture fructose from starch. Corn starch is hydrolyzed into glucose by amylase, then transformed into fructose by isomerase. This process can produce syrup containing up to 90% fructose, and it is called high fructose corn syrup. Due to its sweeter taste and lower cost, it gradually replaced sucrose in foods and beverages. People also consume large amounts of fructose from snacks and beverages unknowingly. Fructose is even found in meals, as it may be used in flavored sauces.
Powder, Syrup of Fructose Applicated in Food Industry
Fructose is widely used in candy, candied fruit, cake and beverage: sweetener, humectant, sweeter in cold and inhibits bacteria. Being used as a sweetener in food is its main function. When sucrose reaches its peak sweetness in about 30 seconds, it tends to override food specific flavor. The sweetness of high fructose corn syrup is perceived sooner and reaches its peak in a short time. When other flavors in food occur, the faded sweetness will not disrupt them. Because their sweetness peaks at different moments, using sucrose and fructose in food together makes the sweetness stronger and last longer.
Inhibiting bacteria is its another function. Before fructose was manufactured in factory, people discovered that concentrated solutions of sucrose was similar to brine for sterilization and preservation. Sucrose, which is easily soluble in water, produces a high osmotic pressure to kill microorganisms. Since fructose molecular weight is about half of sucrose, the same mass of fructose can generate twice osmotic pressure. At room temperature, it is twice as soluble as sucrose, and its maximum osmotic pressure is four times greater than sucrose. Therefore, a large amount of fructose powder is used in candied fruit to inhibit bacteria and prevent spoilage. Its high solubility also prevents it from crystallizing on the surface, making an excellent appearance for products.
Breads and cakes become hard after being exposed to air due to moisture evaporation. Fructose absorbs moisture from the air very easily and remains moist even in a dry environment. Cakes with only sucrose show hardening and broken crusts after a few days. On the other hand，breads with fructose absorb moisture and remain fluffy. Fructose does not crystallize as easily as sucrose, so candies with high fructose corn syrup are not only sweeter but also have a softer texture. Fructose is not easily used by microorganisms in the mouth. It is much less likely to produce tooth decay than natural sugars such as glucose or sucrose.
The character of tasting sweeter in colder conditions makes it very suitable for cold beverages. Drinks containing fructose taste better and have enhanced flavors when refrigerated. Moreover, it is sweeter than sucrose, so less fructose will achieve the same sweetness, which helps reduce costs and calories. High fructose corn syrup also shines in sports beverages. During competition, glucose-containing drinks tends to raise insulin and lower blood glucose, which is one of the reasons athletes underperform. The insulin-independent and faster metabolism make fructose a great choice for athletes to replenish their energy.