# How does cooking affect the amount of vitamin C in lemon juice?

by aisyahmaryamroji (student)

M08G

Title:

Measuring the concentration of vitamin C.

Research Question:

How does cooking affect the amount of vitamin C in lemon juice?

Hypothesis:

The longer the lemon juice is cooked up to the boiling temperature, the lower the concentration of vitamin C.

Variables:

• Independent: Type of lemon juice samples [fresh lemon juice (0 minute boiled) , 10 minutes boiled lemon juice, 1 hour boiled lemon juice].
• Dependent: The concentration of vitamin C.
• Constant:
1. The volume of DCPIP solution used. In each trial, 1 cm3 of DCPIP solution is used. 1 cm3 is chosen because it is neither too much nor too little since too much DCPIP solution used will need high amount of lemon juice to decolourise. In fact, the volume needs to be fixed as different volume of DCPIP solution requires different volume of lemon juice to decolourise.
2. The volume of lemon juice used for dilution. 4 cm3 of each type of lemon juice is used to make up 100 cm3 solution. The volume must be constant as if different amount of lemon juice is used in the dilution, then there is no point of conducting the experiment since the data for each condition of lemon juice does not correspond and tally to each other.
3. The volume of glacial acetic acid used. 4 cm3 of glacial acetic acid used for   dilution in all types of lemon juice.
4. Type of fruit used to prepare juice sample. Juices are extracted from lemon fruits for every trial. This is because different fruits contain different concentration of vitamin C, thus using variety of fruits will greatly affect the reliability of the data.

Apparatus & Materials / Procedures

Refer to the handouts.

DATA COLLECTION AND PROCESSING

1. Data Collection

• Qualitative Data
1. Glacial acetic acid is a colourless solution. It releases pungent and choking smell.
2. Lime juice is a yellowish solution and releases tangy smell.
3. DCPIP is a dark blue solution. When lime juice is titrated into DCPIP, the DCPIP gradually changes from dark blue to pink and eventually decolourises.
4. The resulting solution at the end of the titration, which comprises of DCPIP, lime juice and glacial acetic acid is a cloudy mixture.

• Quantitative Data

Table 1 The initial and final readings of burette in the titration.

1. Data Processing

The volume of lemon juice sample used in the titration can be calculated by using the formula:

Volume of lemon juice sample used = final reading – initial reading

Uncertainty of volume of lemon juice used = uncertainty of final reading + uncertainty of initial reading

Below is an example of calculation made:

The volume of lemon juice sample used in trial 1 for fresh lemon juice = (45.10 – 3.20) cm3

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