PM SHRI KENDRIYA VIDYALAYA NO.
2 AFS
TAMBARAM, CHENNAI.
CHEMISTRY INVESTIGATORY PROJECT
SESSION: 2024 – 2025
TOPIC: STUDY OF ACIDITY OF FRUIT & VEGETABLE JUICES
NAME: GOPIKA S MENON
CLASS: 11-A
CERTIFICATE
This is to certify that _____________of class_______,
Roll no _________ has satisfactorily completed the
chemistry investigatory project on ______________
prescribed by SSCE course under my guidance for the
year 2024 – 2025.
INTERNAL EXAMINER SUBJECT CONVENOR
PRINCIPAL
INDEX
S.No TOPIC Page.No
7
STUDY OF ACIDITY OF FRUIT &
VEGETABLE JUICES
INTRODUCTION
Acidity in fruit and vegetable juices is an important
characteristic that affects their taste, shelf life, and health
benefits.
The acids present in these juices are mainly citric acid, malic
acid, and tartaric acid. These acids not only provide a tangy
flavour but also play a role in the preservation and
antimicrobial properties of the juice.
Different fruits and vegetables have varying acid
compositions, which contribute to their distinct flavours and
health benefits.
For instance, citrus fruits like lemons and oranges are rich in
citric acid, making them more acidic, while vegetables like
carrots have lower acid content, making them milder in taste.
Thus, studying the acidity of fruit and vegetable juices
provides valuable insights into their chemical properties,
health effects, and practical applications in food science.
AIM
To study the acidity of different fruit and vegetable juices by
determining their pH levels and analyzing their effects on food
preservation and digestion.
MATERIALS REQUIRED
1. Fresh fruit and vegetable juices (lemon, orange, tomato,
carrot, etc.)
2. pH paper or pH meter
3. Beakers
4. Glass rod
5. Distilled water
6. Dropper
7. Sodium hydroxide (NaOH) solution
8. Phenolphthalein indicator
9. Measuring cylinder
10. Pipette
THEORY
1) The acidity of a solution is determined by its pH value. The pH
scale ranges from 0 to 14, where:
pH < 7: Acidic
pH = 7: Neutral
pH > 7: Basic
Fruit and vegetable juices contain natural acids, making them
acidic in nature. The presence of acids can be tested using
indicators or pH meters. A titration method can also be used to
determine acidity more accurately. The concentration of acids in a
juice affects its sourness, stability, and ability to inhibit microbial
growth. Highly acidic juices, such as lemon juice, are often used
as natural preservatives.
PROCEDURE
1. Collect fresh fruit and vegetable juices in separate beakers.
2. Dip a pH paper into each juice sample and observe the color
change.
3. Compare the color with a pH chart to determine the
approximate pH.
4. Alternatively, use a pH meter to measure the exact pH value.
5. For titration:
o Take 10 mL of juice in a beaker.
o Add 2-3 drops of phenolphthalein indicator.
o Add sodium hydroxide (NaOH) solution dropwise until
the color changes.
o Note the volume of NaOH used and calculate the
acidity.
o Record observations carefully for analysis.
OBSERVATIONS
Juice pH Value Color Change
Observations
Sample (Approx.) in Titration
Lemon Highly acidic, very
2-3 Pink
Juice sour
Orange Moderately acidic,
3-4 Pink
Juice slightly sweet
Tomato Mildly acidic, slightly
4-5 Light Pink
Juice tangy
Carrot Least acidic, mildly
5-6 Faint Pink
Juice sweet
RESULTS
Lemon juice has the highest acidity, followed by orange
juice.
Tomato juice is less acidic than citrus juices.
Carrot juice is the least acidic among the tested samples.
The acidity of these juices influences their taste, storage, and
potential health effects.
CONCLUSION Different fruit and vegetable juices have varying
levels of acidity. Citrus fruits like lemons and oranges are highly
acidic, whereas vegetables like carrots have lower acidity.
Measuring the pH of juices helps in understanding their properties
and effects on health. Highly acidic juices can be beneficial in
preventing bacterial growth, while less acidic juices may be more
suitable for individuals with acid sensitivity.
PRECAUTIONS
1. Use fresh juices to get accurate results.
2. Clean the pH meter properly before and after use.
3. Handle NaOH solution carefully as it is corrosive.
4. Perform the experiment in a well-ventilated area.
5. Use standardized NaOH solution to ensure precision.
6. Rinse glassware thoroughly between tests to prevent cross-
contamination.
APPLICATIONS
1. Helps in food preservation and quality control.
2. Used in dietary recommendations for acid-sensitive
individuals.
3. Important for beverage industry formulations.
4. Assists in determining the suitability of juices for individuals
with digestive conditions.
5. Helps in understanding the role of acidity in flavor
enhancement.
BIBLIOGRAPHY
NCERT Chemistry Textbook
Laboratory Manual for Chemistry
Online research articles on acidity in fruits and vegetables
Food Science Journals and Research Papers
