What is Sucrose?

Sucrose falls under the category of disaccharide. Sucrose is also commonly referred to as table sugar and also cane sugar. The chemical formula for sucrose is given as C₁₂H₂₂O₁₁. Sucrose is obtained naturally from sugarcane, sugar beets, sugar maple syrup, dates and honey. It is manufactured in, large quantities primarily from sugarcane as well as sugar beets. Being a disaccharide, it is formed by the combination of two sugar molecules namely glucose and fructose. Glucose is a monosaccharide obtained as a photosynthesis product. The positioning of the oxygen atom on fructose is different for both compounds. These two components combine together to form a sucrose molecule.

Carbohydrates form a vital component of our diets. Most natural carbohydrate supplies are grains, vegetables and fruits. Carbohydrates supply energy, especially in the form of glucose i.e. a simple sugar which is a component in so many basic foods; it is an element of starch. In humans, poultry and herbs, carbohydrates have additional critical roles. The formula for carbohydrate is represented as (CH₂O)_n where, n is the carbon number present in the molecule. Carbohydrates are categorized into three groups namely monosaccharides, disaccharides and polysaccharides.

Properties of Sucrose

• If sucrose passes through acid catalyst hydrolysis, a D-glucose and a D-fructose molecule is produced.
• The sucrose’s chemical composition includes the glucose’s α form and fructose’s β form.
• The glyosidic connection is an alpha connection because the creation of molecules is α oriented.
• Sucrose is a sugar that does not reduce as the hemiacetal oxygen is coupled (linked) and is free of hemiacetal hydroxide.
• It shows no mutarotation (α to β conversion) as it has no available hemiacetal-hydroxide. Sucrose does not create ozone's because of the same reason.

Structure of Sucrose

Disaccharides develop whenever two monosaccharides are dehydrated; this is also called condensation reactions. Through this step, one monosaccharide hydroxyl group is linked with monosaccharide hydrogen of another, which releases a water group thus establishing a covalent bond. The glycoside connection is the covalent bond that is formed between a carbohydrate compound and another molecule. Glyosidic associations may be alpha or beta-type, also known as glyosidic links.

An alpha bond is created when the OH group on the first glucose carbon-1 lies underneath the ring field. Glucose is also called as aldose where the carbonyl group is attached at the end of the carbon chain. A 6 membered ring structure is formed when a glucose molecule develops into a ring structure. Fructose is a ketose compound where the carbonyl group is attached at the center of the molecule. In sucrose, the fructose is normally found as a five membered ring compound but in the free state, fructose is usually found in the six-membered state.

Glucose with fructose is seen as contaminants in sugar processing because the mixture makes it impossible to crystallize. To prevent losses of sucrose through its hydrolytic cleavage in the operation of glucose and fructose, rigid cycle management especially of pH, must always be retained.

Glucose

Glucose, frequently identified as dextrose, a category defined as basic sugars carbohydrates (monosaccharides). The molecular formula C₆H₁₂O₆ is used for glucose. It is the only free sugar that circulates in the blood of vertebrates and is found in fruits and honey.  It is the reservoir of cellular energy and its metabolism control is of great importance. The starch molecules are thousands of straight-chain glucose segments and are the strongest carbohydrates of plants. Cellulose, which is also linear, is another important glucose compound. The dextrose molecule is in the D-glucose form.

Fructose

Fructose appears in apples, sweet spices and syrups together with glucose; it occurs in some vegetables. The disaccharide sucrose or common table sugar is made up of fructose alongside glucose. In the processing of carbohydrates, fructose phosphate variants (e.g., fructose-1-phosphate, fructose-1,6-diphosphate) are essential.

Refining of Sucrose

Refining of sugar is a strong extraction process of sugar using refined raw cane sugars. In beet sugar plants, the refining methods for remelting and recyrstalling top quality white sugars are also employed.  Some 35% of cane sugar is refined; the rest are eaten as white or raw sugar. In a four-step procedure, the sucrose is distilled from raw sugar (97.5% sucrose):

Affinity – It dissolves those impurities present on the surface.

Carbonation – Involves removal of additional impurities in the precipitating solution in presence of calcium carbonate.

Charcoal filtration – Involves removal of contaminants through carbon activation.

Crystallization – It uses a form of a vacuum.

Various lower quality materials such as molasses, golden syrup and treacle are extracted during the purification process. These products thus contain both sucrose and contaminant concentrations necessary to provide each substance with their special physicochemical characteristics.

Importance of Sucrose in Plants

Sucrose is the most frequent source of carbohydrate employed in a plant for the distribution of carbon. Sucrose can be disintegrated in water although keeping the framework intact. Sucrose, the unique vascular tissue for transporting sugars, can be transported to the phloem by plant cells. Sucrose passes across the intracellular locations of the leaf from the cells it was made. It reaches a vascular pack where it is pumped into the phloem by advanced cells. In order to prevent sugar combination from solidifying, the xylem or vascular tube which transports water introduces small volumes of water to this phloem.

Corn Syrup

Maize syrup is viscous sweet syrup made by disintegrating maize starch (hydrolyzing), whether by heating it with diluted acid or by using enzymes. Corn syrup is often also termed as glucose syrup, which is also derived by starch hydrolysis but not always by cornstarch, and weeds, potatoes, rice and other plants which could be used as sources for starch. Corn syrup is utilized in the manufacture of high-fructose corn syrup wherein glucose is converted to fructose by an enzyme named D-xylose isomerase. The food sector often uses high-fructose maize syrup for the production of particularly soft drinks, as it is substantially less expensive than sucrose.

Common Mistakes

The most common mistake student can make is while identifying the structure of glucose and fructose. Both will have the same structure with a difference in oxygen position. So care should be taken while naming a sugar molecule.

Practice Problem

What category of saccharides does the sucrose molecule belong to?

Solution: Disaccharide.

Context and Applications

This topic is significant in the professional exams for both undergraduate and graduate courses, especially for Bachelors and Masters in Chemistry, Biochemistry and Molecular Biology.