What makes sugars reducing

Reducing sugars can react with other parts of the food, like amino acids, to change the color or taste of the food. Sugars are found naturally in all fruits, vegetables, dairy products and whole grains. These natural sugars are otherwise known as carbohydrates, an essential macronutrient. Dietary carbohydrates are categorized as monosaccharides, which are single sugar molecules; disaccharides -- two sugar molecules linked together; or oligosaccharides and polysaccharides, which are longer chains of sugar molecules.

Monosaccharides include glucose, galactose and fructose, which are all reducing sugars. Monosaccharides are not often found alone in nature, but they are components of disaccharides and polysaccharides. For this reason, some disaccharides, such as maltose, are also reducing sugars.

The most important monosaccharide and reducing sugar is glucose. In the body, glucose is known as blood sugar because it is essential for brain function and physical energy. Fructose is another reducing sugar and is known as the sweetest of all monosaccharides.

Galactose, another reducing sugar, is a component of lactose that is found in dairy products. The redox reactions involve the transfer of hydrogen, oxygen, or electrons where two very important characteristics are common in all three reactions. Secondly , they always involve a net chemical change where new substituents are formed by the reaction of reactants. The examples of all three forms of chemical reaction have been elaborated on below.

Two very important tests are often performed to identify the presence of reducing sugar. These tests are the Benedict test and the Fehling test. After around ten minutes the solution starts to change its color. If the color changes to blue it means that there is no reducing sugar present.

But if the color changes to green, yellow, orange, red, and then finally to dark red or brown color confirms the presence of reducing sugar in the food. The chemical composition of the Benedict solution states that it is made of an anhydrous solution of sodium citrate, sodium carbonate, and copper II sulfate pentahydrate. During its reaction with the reducing sugar, the blue copper sulfate in the solution is converted into red-brown copper sulfide.

It is worth mentioning here that these tests only show the qualitative analysis of reducing sugar. In the Fehling test, the solution is warmed until the sample where the availability of reducing sugar has to be tested is homogeneously mixed in water after which the Fehling solution is added. If the reducing sugar is present the color of the solution will be changed to a red precipitate color resembling rust.

This test is specifically used for the identification of monosaccharides, especially ketoses and aldoses. These tests can be used in the laboratory for the determination of reducing sugar present in the urine which can be used to diagnose diabetes mellitus. It must be noted here that the reduction of aldehydes results in the formation of primary alcohols while the reduction of ketones gives secondary alcohols.

The most common example of reducing sugar and monosaccharides is glucose. In the human body, glucose is also referred to as blood sugar. It is essential for the proper functioning of brains and as a source of energy in various physical activities.

Another reducing sugar is fructose, which is the sweetest of all monosaccharides. Galactose is another example of reducing sugar. It is a component of lactose available in many dairy products. Moreover, the list of reducing sugars also includes maltose, arabinose, and glyceraldehyde.

Carbohydrates, especially reducing sugar are the most abundant organic molecules that can be found in nature. They have a wide range of functions in biology. They provide a significant fraction of daily used dietary calories in most of the living organisms living on the earth. Also, their major role is to act as the storage of energy in living bodies. Read: Glycolysis , Fermentation , and Aerobic respiration.

Carbohydrates also serve as one of the cell membrane components and function primarily in mediating various intermolecular communications in the bodies of living organisms.

Lastly, via Maillard reactions, carbohydrates are responsible for determining the crust color and the taste of the food such as coffee, bread, and roasted food items. There are many uses of reducing sugar in our daily life activities. In medicines, the Fehling solution has been used as a test to detect diabetes in human blood.

The relative measurement of the number of oxidizing agents reduced by the available glucose makes it easy to calculate the concentration of glucose present in the human blood or urine.

Moreover, after the calculation of the exact amount of glucose present, it becomes easier to prescribe the amount of insulin that must be taken by the patients from the doctors. In food chemistry, the levels of reducing sugar in the products such as wine, juices, and sugar cane decide their quality.

Try to answer the quiz below to check what you have learned so far about reducing sugar. A variant of this procedure is used for the preparation of mirrors. Bottom line here is that adding base has the effect of increasing the concentration of the starting aldehyde.

If I am wrong, please tell me leave a comment. One of the access points for the initiation of a single-electron transfer reaction is a carbon-metal bond, which can be achieved through base-promoted formation of an enolate. That requires that the aldehyde have a proton on the alpha carbon i. Thus it would appear that the reaction needs to proceed through an enol. Hover here for a pop-up image or [ click for image of a hypothetical mechanism ].

Image sources: Benedicts solution. Tollens test. Note 1. The standard way to do it is the Pinnick oxidation. Note 2. The quantitative test apparently employs potassium isocyanate, which results in a colourless precipitate. See the mechanism section. Note 4. A very enjoyable post! In the 4th reaction, the charge is on the oxygen; this is preferable. What if a product contains high percentage of reducing sugar? What does it denotes? I have prepared a product which contains Thank you very much for your posts they are very helpful.

Blessings and thanks again! And thanks again for your very clear explanations. I have a question regarding reducing sugars as excipients with drugs.

Some carbohydrates reducing sugars form covalent bonds with drugs that contain primary and secondary amines. So I have been looking at the Maillard reaction which breaks down the hydroxyl group of a reducing sugar and then forms Amadori products.

I have been searching for a reaction mechanism for the Amadori adduct formed from dexamphetamine and lactose. I was wondering if you could perhaps give a generic mechanism or a similar example.

I note you give two examples of lactose and maltose as disaccharides that are reducing sugars as they contain the hemiacetal. I was wondering if you could give a general mechanism reacting with a primary amine such as R-NH2?. This website is phenomenal. Ashenhurst teaches these topics so much better than they do at school! Keep up the great work! Your email address will not be published. Save my name, email, and website in this browser for the next time I comment.

Notify me via e-mail if anyone answers my comment. This site uses Akismet to reduce spam. Learn how your comment data is processed. Previous What is Mutarotation? A test for blood sugar suitable for diabetics should have a similar ease of use. So what does this have to do with sugars?