Do you know apple, cherry, grape, guava, mango, litchi, sugar cane and even honey all have one thing in common? Do you know what is it? Well the answer is they all contain the same kind of sugar which is ‘Fructose’. Fructose is also called fruit sugar or levulose. The word ‘fructose’ is made up of Latin word ‘fructus’ which means ‘fruit’ and ‘ose’ which means sugar. ‘ose’ is a generic chemical suffix for sugars. Fructose was discovered by French Chemist Augustine – Pierre Dubrunfaut in 1847 while the name fructose was coined by English Chemist William Allen Miller in 1857.  

Fructose or fruit sugar is naturally found in fruits, honey, flowers, berries, and most root vegetables. It is a simpler sugar than glucose and sucrose. So, it is easier to digest but only the liver can digest fructose sugar. Over consumption of fructose leads to overwork pressure on the liver. In this condition the liver starts converting fructose into fat which leads to obesity. Apart from this, over consumption of fructose can be a key driver of many diseases like type diabetes, heart disease and liver failure. 

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What is Fructose? 

Fructose is simple ketonic monosaccharide sugar found in many plants, flowers, and fruits. It is a fruit sugar which is one of the three dietary monosaccharides along with glucose and galactose that are absorbed into blood directly during digestion. Monosaccharides are the simplest form of sugar and basic unit of carbohydrates. So, fructose is the simplest sugars and easier to digest than other sugars. In pure form it is sweet, white, odorless, and crystalline solid. It is more soluble in water than other sugars. Commonly it is found in fruits such as mango, litchi, cherry, guava, and vegetables such as carrot, radish, beetroot and sugarcane etc. Commercially, it is derived from sugar cane, maize, and sugar beets. 

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Structure of Fructose

Crystalline fructose possesses a ring structure. It is a 6 – carbon polyhydroxy ketone. It gains stability by hemiketal and internal hydrogen bonding. In this form it is called D – fructopyranose while in its water solution fructose occurs as equilibrium mixture of 70% fructopyranose and 22% fructofuranose and 7% three other forms including its acyclic structures. 

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Fischer projection of D – Fructose (open chain form)

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Cyclic Form of Fructose 

Fructose contains six carbons atoms, twelve hydrogen atoms and six oxygen atoms. It has a ketone functional group at carbon number 2. Thus, it is a ketohexose. It is obtained along with glucose.  Molecular formula of fructose is C6H12O6

Physical Properties of Fructose 

Fructose is an important ketohexose which is obtained by hydrolysis of disaccharide sucrose. Physical properties of fructose are listed below –

  • Its molar mass is 180.156 g.mol-1.

  • Its melting point is 103.

  • It is most soluble sugar in water.

  • It is sweet in taste. This is the reason it is used in beverages and foods as a sweetening agent. It is low cost and sweetest of all naturally occurring carbohydrates. As we increase the temperature, its relative sweetness decreases. 

  • It is white crystalline solid at room temperature. 

  • It is an odorless sugar.

  • It absorbs moisture quickly and becomes sticky.

  • It is an excellent humectant. 

Chemical Properties of Fructose 

It is very important to know all chemical aspects of fructose as it is extensively used in food products and part of our daily diet. Chemical properties of fructose are listed below –

  • Fructose can be fermented anaerobically by yeast and bacteria. Yeast converts sugar to ethanol and carbon dioxide. 

  • It shows Maillard reaction. As it can exist in open chain form for greater extent so the initial stage of Maillard reaction occurs more rapidly. 

  • It has potential to form mutagenic compounds. 

  • After dehydration, fructose gives hydroxymethylfurfural (“HMF”). 

Preparation of Fructose 

It can be prepared by hydrolysis of sucrose in presence of invertase or dilute sulfuric acid. It is a laboratory method of preparation of fructose. Reaction is given below –

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Now fructose is separated from glucose by crystallization using alcohol. As glucose is only sparingly soluble in alcohol so it gets separated first in the form of crystals. 

Commercial production of fructose is done by using glucose. An aqueous solution of glucose is prepared which is then converted into D – glucosone. Now by chemical hydrogenation process D – glucosone is converted into pure fructose. 

Applications of Fructose 

Fructose has various applications. Few of them are listed below –

  • As it can be converted into hydroxymethylfurfural (“HMF”) so it can be used as diesel fuel additives and diesel fuel itself. 

  • Large scale applications of fructose involve its use as a sweetener. It is used in many foods as a sweetening agent. It is a low - calorie sweetener which enhances its value as a sweetening agent. 

  • It is used in plastics as well.

  • It is used to increase the shelf life of foods like nutrition bars and cookies.

  • Corn syrup is produced by using fructose.

  •  It is used in infant feeding formulas. 

  • It is used as a food for diabetics. 

  • It has a low glycemic index and results in moderate release of insulin to the bloodstream relative to glucose and fructose. 

  • It is used in stevia. 

  • It is used in many beverages and baked goods etc. 

Potential Health Effects of Fructose 

Over consumption of fructose causes many adverse effects on human health. Few of them are listed below –

  • It causes weight gain. Due obesity, hypertension is caused. 

  • High fructose corn syrup may cause Alzheimer’s and memory loss.

  • It elevates bad cholesterol levels in the body.

  • It causes type – II diabetes. 

  • Over consumption creates a lot of work pressure on the liver and that may cause damage to the liver.

  • It can cause cardiovascular disorders. 

  • It is extremely addictive and can cause damage to the immune system as well. 

Although fructose is a low - calorie sugar when compared to glucose and sucrose and has many benefits over them but as stated above it also has many adverse health effects when consumed in large amounts. So, we need to consume fructose added food products in limited and required amounts. 

This is all about Fructose, if you are looking for solutions to NCERT Textbook problems based on this topic, then log on to Vedantu website or download Vedantu Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.