Main Difference – Glucose vs Fructose
Carbohydrate is an essential macromolecule to all living creatures in the world and it can be divided into three categories. They are monosaccharides, disaccharides, and polysaccharides. Glucose and fructose are considered as simple and the most abundant monosaccharides in the world. However, there seems to be a lot of confusion over the difference between glucose and fructose because they have a similar formula: C6H12O6. Both fructose and glucose are considered as simple reducing sugars and are absorbed directly into the bloodstream during digestion. However, glucose is an aldo sugar whereas fructose is a simple keto sugar. Fructose is used commercially in foods and beverage industries because of its low cost and high sweetness compared to glucose. This is the main difference between glucose and fructose. In this article, let’s elaborate the difference between glucose and fructose in terms of their intended uses as well as chemical and physical properties.
What is Glucose
The word glucose is derived from Greek and literally means “sweet wine”; it is also known as grape sugar. Its molecular formula is C6H12O6. The D-glucose is the most predominant isomer in nature compared to L-glucose. It is the major output of the photosynthesis process where water and carbon dioxide are used to produce glucose by plant chlorophylls pigments in the presence of sunlight. In addition, glucose is the main energy releasing compound in cellular respiration and it is more or less similar to the reverse of the photosynthesis reaction. Glucose is also used to synthesize some disaccharides and polysaccharides. It is used to synthesize starch in plant and glycogen in animals. In addition, it can be obtained by the hydrolysis of carbohydrates including table sugar (sucrose), maltose, cellulose, glycogen etc.
What is Fructose
Fructose is a simple keto sugar and it is also known as fruit sugar because it is mainly found in many plants. Its molecular formula is C6H12O6. The D-fructose is the most predominant isomer in nature compared to L-fructose. It is the most reactive and most water soluble sugar compared to other natural sugars. It can be isolated from honey, tree and vine fruits, flowers, berries, and root vegetables. However, industrially fructose is produced from sugar cane, sugar beets, and corn. Fructose is mainly important for beverage industries and bakery products because it contributes to enhancing palatability and taste, and for browning or color development.
Difference Between Glucose and Fructose
The differences between glucose and fructose can be divided into following categories. They are;
Glucose was first described by the German chemist Andreas Marggraf in 1747. However, it was largely investigated by Emil Fischer.
Fructose was first introduced by French chemist Augustin-Pierre Dubrunfaut in 1847.
Glucose is rarely stored in plants or animals because it is highly reactive. But glucose is the building block for starch (storage compound of plants), glycogen (storage compound of animals), cellulose (in cell wall), sucrose (in nectar, plant derived treacle), and lactose (in milk).
Fructose is found in honey, tree and vine fruits, flowers, berries, and most root vegetables.
Glucose is also known as Blood sugar, Dextrose, Corn sugar, D-Glucose, Grape sugar.
Fructose is also known as Fruit sugar, levulose, D-fructofuranose, D-fructose, D-arabino-hexulose.
Glucose’s name is 2,3,4,5,6-Pentahydroxyhexanal.
Fructose’s name is 1,3,4,5,6-Pentahydroxy-2-hexanone.
Glucose is a hexose as well as an aldose and, therefore, it is also known as an aldohexose.
Fructose is a 6-carbon keto sugar and also known as D-fructopyranose.
Glucose is produced commercially via the enzymatic hydrolysis of starch.
Fructose is produced commercially from sugarcane, sugar beets, and corn.
A Product of Photosynthesis
Glucose is the major product of photosynthesis.
Fructose is not a product of photosynthesis.
Glucose is less water soluble compared to fructose.
Fructose is the most water-soluble sugar of all the sugars.
Control of Appetite
Drinking high-glucose results in higher circulating insulin and leptin levels, and lower ghrelin levels after the meal, compared with intake of high fructose drinks,
Drinking high-fructose results in lower circulating insulin and leptin levels, and greater ghrelin levels after the meal, compared with intake of high glucose drinks Since a low level of leptin and insulin can decrease appetite and high level of ghrelin can increase appetite, some investigators suspect that eating great amounts of fructose raises the probability of weight gain.
Glucose has a high glycemic index values compared to fructose.
Fructose has the lowest glycemic index (GI=19) value of all the natural sugars including glucose.
Glucose undergoes Maillard reaction, non-enzymatic browning, with amino acids slowly than fructose.
Fructose undergoes Maillard reaction more rapidly than glucose. Thus, it has the potential to play a major role in the changes in food palatability, browning and decrease of compared tenderness during cake preparation, and the creation of mutagenic compounds.
The sweetness of glucose is lower than that of fructose
The sweetness of fructose is greater than that of glucose and it shows a synergy effect when combined with other sweeteners.
Glucose is somewhat easy to crystallize from an aqueous solution compared to fructose.
Fructose is difficult to crystallize from an aqueous solution compared to glucose.
Hygroscopicity or Water Absorbance
Glucose slowly absorbs moisture from the environment compared to fructose.
Fructose quickly absorbs moisture from the environment compared to glucose.
Release of Water
Glucose quickly releases moisture to the environment compared to fructose.
Fructose slowly releases moisture to the environment compared to glucose. Thus, fructose is considered as a good humectant and preserves moisture for an extended period of time and can contribute a more palatable texture, and longer shelf life to the fructose containing food products.
Use as a Sweetener
Glucose is used in the production of candy, breakfast bars, jujubes, marshmallows, gelatin desserts.
Fructose is used in the production of diet soft drinks, fruit drinks, diet soda, instant breakfasts, chewing gum, frozen desserts, gelatin desserts, juices, laxatives, chewable vitamin supplements, milk drinks, pharmaceutical drugs, and supplements.
In conclusion, glucose and fructose are primarily simple sugars which are used as sweetening agents. But fructose is economically feasible and healthy food ingredient compared to glucose. However, there is still a controversial issue about the safety of the long-term consumption of these natural sugars.
Boerio-Goates, Juliana (1991), Heat-capacity measurements and thermodynamic functions of crystalline α-D-glucose at temperatures from 10K to 340K, J. Chem. Thermodynam. 23(5): 403–9.
Bray, G. A. (2013). Energy and Fructose From Beverages Sweetened With Sugar or High-Fructose Corn Syrup Pose a Health Risk for Some People. Advances in Nutrition: An International Review Journal 4 (2): 220–225.
Chapter 3: Calculation of the Energy Content of Foods – Energy Conversion Factors, Food energy — methods of analysis and conversion factors, FAO Food and Nutrition Paper 77, Rome: Food and Agriculture Organization, 2003, ISBN 92-5-105014-7.
Hyvonen, L. and Koivistoinen, P (1982). Fructose in Food Systems. In Birch, G.G. and Parker, K.J. Nutritive Sweeteners. London and New Jersey: Applied Science Publishers. pp. 133–144. ISBN 0-85334-997-5.
Malik, Vasanti S. and Hu, Frank B. (2015). Fructose and Cardio-metabolic Health. Journal of the American College of Cardiology 66 (14): 1615–1624.
“Glucose metabolism” by Häggström, Mikael. “Medical gallery of Mikael Häggström 2014”. Wikiversity Journal of Medicine 1 (2). DOI:10.15347/wjm/2014.008. ISSN 20018762. -Own work. (Public Domain) via Commons
“DL-Fructose num” by NEUROtiker – Own work. (Public Domain) via Commons