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Are fruit juices healthier than fizzy drinks?

Award Level Gold


Before you start your investigation you should carry out a risk assessment and have it checked by your teacher. For help with this, read through our health and safety information and look out for health and safety warnings in the text.

Fizzy drinks are considered unhealthy due to their high sugar content and the amount of additives they contain. On the other hand, fruit juices are often seen as a healthy alternative and of greater nutritional value. In this project you are going to carry out quantitative experiments to determine the concentration of some of the ingredients of these two types of drinks. Using your results, you will decide what the health benefits or risks are from drinking them and publish your findings for a particular target audience.

Getting started

First choose a range of products to analyse. These should include a range of regular fizzy drinks and popular flavours of pure fruit juice. Some tests you could carry out are:

  • Perception of sweetness. Many fizzy drinks contain artificial sweeteners whereas pure fruit juices are naturally sweeten Devise an experiment to compare the relative sweetness of artificial and natural sweeteners. This could involve carrying out taste tests with dissolved solutions of the sweeteners found in fizzy drinks and the natural sugars found in fruit juices, comparing their sweetness and other taste differences.

Remember, taste tests must not be conducted in a laboratory but in a food technology room. Make sure you use food grade chemicals and carefully follow hygiene procedures.

  • Determining reducing sugars concentration. A variety of techniques can be used for this experim You could use a test strip, like those used by diabetics, to provide a semi- quantitative result. For more accurate results, try using a compound called 3,5- dinitrosalicylate, or DNS. When added to a solution containing reducing sugars, DNS is reduced to a compound called ANS, which is a red colour. The density of this colour varies depending on the concentration of reducing sugars, this density value can be measured using a colorimeter.

3,5- dinitrosalicylate (DNS) is an IRRITANT.

  • Determining the amino acids present by chromatography. Which type of drink contains the most essential amino acids?
  • Determining the effect of fizzy drinks and fruit juices on tooth decay. Extracted teeth can be sourced from dentists and left in drinks to study their effect

Caffeine content

Carry out research into the caffeine content of the drinks you are investigating. You need to use a technique called High Performance Liquid Chromatography (HPLC) to determine the amount of caffeine in a substance. You are unlikely to have the equipment at your school or college, however you could approach a local university to see if you could use their facilities.

Antimicrobial effects of caffeine

It is claimed that caffeine can prevent microbial growth. Carry out a further experiment to investigate this claim. Test the antimicrobial activity of different concentrations of caffeine solution against different concentrations of other anti-microbials to determine If caffeine is more effective than other anti-microbials at any concentration, and at what concentration caffeine has the most anti-microbial effect.

You must adopt strict sterile technique, including autoclaving any plates without opening them after incubation.

Publishing your findings

Illustrate the findings and conclusions from your experiments and research work in a poster or information leaflet which is aimed at a particular target audience. This could be children and teenagers who frequently drink fizzy drinks or parents who want to decide what drinks are best to buy for their children.

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