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Chemistry + Nutrition and Food

Measure the vitamin C in fruit juices

Titrate juices with iodine and starch to compare how much vitamin C each contains.

  • DifficultyIntermediate
  • Estimated time1 day
  • BudgetUnder ₹250
  • ClassClass 9–12
  • TeamSolo or up to 2
  • You needHousehold materials

Prerequisites: Idea of a chemical reaction and concentration

Original · by TechnifyedExperimentInvestigationLow costResearch orientedWell documentedTwo subjects

My projects

Overview

Iodine reacts with vitamin C. While vitamin C remains, added iodine is used up; once it is gone, the iodine turns starch blue-black. The number of drops needed tells you how much vitamin C was there.

Why build this?

It is a real quantitative analysis you can do at home, and the results often surprise people about packaged juices.

What you will learn

  • How a titration finds an unknown amount
  • What an end point is
  • How to calibrate with a known standard
  • How storage and heat affect vitamin C

Skills you will use

CalculationComparisonTitration

Safety

  • Wear safety glasses and gloves, work in a ventilated place, label every container and wash your hands afterwards. Do not taste or smell chemicals directly, and do not mix chemicals beyond the steps given.
  • Use clean equipment, do not eat anything tested with chemicals, and check for allergies before a tasting.

Materials and tools

  • Tincture of iodine
  • Starch solution (from boiled rice water or cornflour)
  • Vitamin C tablet (500 mg) as a standard
  • Fresh and packaged juices
  • Dropper or syringe
  • Clear cups

Tools and software

Dropper

Expected costUnder ₹250About ₹250 at most, less if you borrow parts
Estimated duration1 day6 build steps, plus the report

Step-by-step roadmap

  1. Start

    You will finish with: a ranked table of vitamin C per 100 ml for five juices.

  2. 1

    Prerequisites

    Know this first: idea of a chemical reaction and concentration. Then collect the 6 items in the materials list.

  3. 2

    Learn

    • How a titration finds an unknown amount
    • What an end point is
    • How to calibrate with a known standard
    • How storage and heat affect vitamin C
  4. 3

    Plan

    Write your question, your hypothesis and the one thing you will change. Draw the table you will fill in before you start.

  5. 4

    Build

    1. Dissolve the vitamin C tablet in 500 ml of water to make a 1 mg/ml standard.
    2. Put 10 ml of standard in a cup with a few drops of starch.
    3. Add iodine drop by drop, swirling, until a blue-black colour stays for 20 seconds; count the drops.
    4. Repeat with 10 ml of each juice.
    5. Calculate the vitamin C in each juice from the drop ratio.
    6. Repeat each sample three times and average.
  6. 5

    Test

    The fresh lemon or orange juice should need clearly more drops than a packaged drink.

  7. 6

    Document

    Record every reading with its unit, photograph the setup and draw a graph of the result. Report structure

  8. 7

    Present

    Explain the question, the method and the graph in two minutes; keep the setup ready to demonstrate. Presentation structure · Viva questions

  9. 8

    Publish

    Share the report and photos with your class, a science fair or your school magazine.

Expected outcome

A ranked table of vitamin C per 100 ml for five juices.

Other versions of this project

Beginner version

Compare just fresh orange juice and a packaged orange drink.

Advanced version

Test the same juice fresh, after a day in the fridge and after boiling, and plot the loss.

Research version

Study how storage time and temperature change vitamin C in one juice over a week.

Make this project better

  1. BasicCompare just fresh orange juice and a packaged orange drink.
  2. This projectMeasure the vitamin C in fruit juices
  3. AdvancedTest the same juice fresh, after a day in the fridge and after boiling, and plot the loss.
  4. ResearchStudy how storage time and temperature change vitamin C in one juice over a week.

Ways to do this project

Text marked "You write this" is a prompt for your own work; everything else is specific to this project.

Problem
Which juice has the most vitamin C per 100 ml?
Hypothesis
If juice is freshly squeezed, then it will contain more vitamin C than packaged juice.
Variables
Independent: type of juice. Dependent: drops of iodine to reach the end point. Controlled: sample volume, starch amount, iodine strength

Materials and procedure are in Materials and the Roadmap.

Observation table

JuiceDrops (trial 1–3)Mean dropsVitamin C (mg per 100 ml)
Graph
Bar chart of vitamin C per 100 ml for each juice
Results
You write thisState what the graph shows in one or two sentences, with numbers.
Conclusion
You write thisSay whether the result supports your hypothesis and why you think so.

Display board

  • Title and your name
  • Question
  • Hypothesis
  • Materials
  • Procedure (with photos)
  • Data table and graph
  • Conclusion
  • What you would do next

Questions judges ask

  • Why add starch?
  • Why do you need a standard?
  • Why does boiled juice have less?
  • What would you change if you did this again?
  • What was your biggest source of error, and how did you reduce it?
  • Where is this idea used in real life?

Working as a team

Solo or up to 2. Suggested roles:

ResearchSetup and measurementData and graphsDocumentationPresentation

Report and presentation

Report structure

  1. Title and question
  2. Background: the science behind it
  3. Hypothesis
  4. Materials
  5. Method (steps, with a diagram or photo)
  6. Observations (table)
  7. Results (graph and calculation)
  8. Sources of error
  9. Conclusion
  10. What you would do next
  11. References

Presentation structure

  1. The question
  2. Why it matters
  3. The idea behind it
  4. Setup (photo)
  5. Method in three steps
  6. Results (one clear graph)
  7. What the result means
  8. Errors and limits
  9. Conclusion and next step

Viva questions

Try answering before you open each one.

Why add starch?

It turns blue-black with free iodine, showing the end point.

Why do you need a standard?

To convert drops into milligrams of vitamin C.

Why does boiled juice have less?

Heat and oxygen destroy vitamin C.

What is the chemical name of vitamin C?

Ascorbic acid.

Resources

ICMR National Institute of Nutritionnin.res.inNCERT textbooksncert.nic.inPhET interactive simulationsphet.colorado.edu

Source and attribution

Original

Written by Technifyed. Free to use for your own school or college project; write the report in your own words. Added 1 Oct 2026.

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