Advanced Projects in Chemistry - Density Method for Determination of Sugar Content in Fizzy Drinks

Sugar is an important diet constituent which unfortunately in today’s world is a major cause of stress related ailments such as obesity and diabetes. In the present day scenario, the curse of modernization is stress. Stress lowers the glycogen content of the body which makes a consumer reach out for a sugary drink. Stress is therefore linked directly as the cause of diabetes and obesity. Sugar absorption into the cells can be regulated by the hormone insulin. Whenever there is rise in blood sugar levels, immediately insulin is produced. Insulin is the only hormone that has to counteract all other hormones which tend to increase the blood glucose levels.

Most of these counteracting hormones are released during stress. Mental distress or overwork increases the body’s demand for sugar and sugar is a carbohydrate. Sugar gives energy to our muscles to help us walk and run. It also gives energy to the brain. Therefore, to a knowledgeable consumer, the label claim of the product becomes an important feature whilst choosing a product. With the ever increasing awareness of today's consumer, the dietary requirements and the content of the ingredients become mandatory.

Sugar is not only a major source of carbohydrate but also an instant source of energy to the body. During hard exercise, carbohydrate can be depleted at a rate of 3-4 grams per minute. If this is sustained for 2 hours or more, a very large fraction of the total body carbohydrate stores will be exhausted and if not checked will result in reduced performance. Recovery of the muscle and liver glycogen stores after exercise will normally require 24-48 hours for complete recovery. During exercise, there is in an increased uptake of blood glucose by the muscles and to prevent blood glucose levels falling, the liver produces stored glucose.

Consuming carbohydrate in the form of sugar before, during and after exercise will help prevent blood glucose levels falling too low and help maintain the body's glycogen stores. Many athletes cannot consume food before or during exercise and therefore a formulated drink is required which will provide the carbohydrate needed. Since sugar is so instrumental in both health and as a source of energy a project study for determining the sugar content in fizz drinks was thought to be important. Drinking plain water causes bloating, suppresses thirst and thus restricts further consumption of fluid. Plain water is a poor choice where high fluid intake is required. Water contains no carbohydrate or electrolytes.

Mass percentages is the best way of expressing concentration for applications in which the physical rather than the chemical properties of the mixture are most important. Be it an obese person or an athlete a quick look at the sugar content in the can of fizz drink is important. Sugar drinks provide the much needed instantaneous carbohydrate required by the body for both physical and mental activity. The fizz added to these drinks gives instant satisfaction through burping as well as a sharp taste to the drink. A student studying chemistry at the K-11-12 grade learns about solutions, different forms of expression of concentration as well as laws that govern the dissolution of gases in solution.

With a project on fizz drinks the student gets hands on experience in learning -

^ To express sugar concentrations in different forms viz.- mass %, molarity, molality, mole fraction, normality.

A comparison of the different forms of expressing concentration of sugar leads him/her to y conclude that since a fizz drink is a heterogeneous mixture of the different ingredients and so, mass % is the best means of expressing sugar content. An ordinary consumer requires knowledge of sugar in gms per volume or mass of solution only so that he can determine the calories consumed and monitor the sugar intake.

^ A student of chemistry always associates determination of solutes with chemical analysis. The student learns to use an intensive property such as density, to determine amount of solute viz sugar for a fixed volume of solution.

Carbon dioxide dissolved in the fizz drink does alter the outcome of the results. Dissolved Carbon dioxide in a flat drink can be completely removed only through the process of boiling. However, boiling causes change of mass or the possibility of the sugar caramelizing.

The amount of sugar determined experimentally is slightly lower than the label claim of sugar contained in the solution. The remnant amounts of carbon dioxide are used to the advantage of the study.

^ The student is instructed in his/her theory class of Henry’s Law. Henry's law is applicable to carbonated soft drinks. Before the bottle or can is opened, the gas above the drink is almost pure carbon dioxide at a pressure slightly higher than atmospheric pressure. The fizz drink itself contains dissolved carbon dioxide. When the bottle or can is opened, some of this gas escapes, giving the characteristic pop sound. The escape of the bottled gas is because the pressure above the liquid is now lower, some of the dissolved carbon dioxide comes out of solution as bubbles. If a glass of the drink is left in the open, the concentration of carbon dioxide in solution will come into equilibrium with the carbon dioxide in the air, and the drink goes "flat".

Using Henry’s Law the student is able to determine the moles of carbon dioxide gas that remains dissolved in the drink.

Henry’s law can be mathematically expressed as -
P = Kh. ( mole fraction of carbon dioxide in the solution)
P = The pressure of the gas above the solution = atmospheric pressure
Kh = Henry’s constant for CO2 dissolved in water = 29.4 L-atm/mol Using this expression the amount of CO2 dissolved in the flat fizz drink can be calculated.

This study enhances the knowledge of the student in the mathematical calculations of expressing concentrations, using an experimental technique to determine unknown amounts of sugars in drinks through density determinations and the application of Henry’s law to determine the amount of dissolved carbon dioxide.

Acknowledgments- The experimental work for this project was diligently carried out by Rahul Krishnan and Kevin Sam of Grade XII, of R.N. Podar, CBSE, Senior Secondary High School, Santacruz (West).