How do different temperatures (20℃, 40℃, 60℃, 80℃, 100℃ ± 0.5℃) affect the relative absorbance of natural fruit dye extracted from frozen blueberries, measured with a spectrometer?
Variables
Independent variable:
The temperature used to filter the fruit dye (20℃, 40℃, 60℃, 80℃, 100℃)
Using a hot plate to achieve (40℃, 60℃, 80℃, 100℃)
Used outdoor temperature to achieve 20℃
Dependent variable:
Relative absorbance of the different temperature fruit dyes, measured with a spectrometer with a wavelength ranging from 380.0-950.0nm
Control variables:
Concentration of fruit dye
By diluting with a fixed volume of distilled water
The volume of fruit dye
120g diluted solution
Source of frozen blueberries
The same box of frozen blueberries
Introduction
Fruits often leave stains on fabric that are hard to wash off because of their natural color pigments. Blueberries, strawberries, raspberries, blackberries, etc., all contain anthocyanin, which has the molecular formula C15H11O+ and gives the effect of natural color dyes.
Anthocyanins are water-soluble pigments found in fruits, vegetables, or greens. As part of the phenol group, anthocyanin produces blue, red, and purple. Therefore, anthocyanins are often used as natural fruit dyes. However, the pH, light, temperature, and structure can still affect the color and stability of these pigments. Anthocyanins are particularly sensitive to temperature, which can degrade their structure and change their absorption properties, leading to changes in their color intensity (Mattioli et al.).
Figure 1 (chemical structure of anthocyanin)
(Mattioli et al.)
Inspired by the blueberry stain on my sweatshirt, and how the stain fades after long exposure to the sun, I decided to base my chemistry IA on natural fruit dyes and temperature. In this experiment, a spectrometer is used to measure the relative absorbance of blueberry dye at different temperatures. A spectrometer is ideal for this experiment as it allows precise measurements of the pigments’ light absorption at specific wavelengths, which corresponds to their color intensity.
Apparatus
Frozen blueberries (100g)
Mortar and Pestle
Marker and tape
Hot plate
Beaker (250mL) x7
Chronicle flask (250mL) x5
spectrometer and 5 cuvettes (1 cm path length)
Glass stirring rod
Pipet x2
Timer
Filter paper x5
Funnel x5
Thermometer
Distilled water (150mL)
Volumetric cylinder (25mL)
Sieve
Weighing scale
Methodology
Measure 100g of frozen blueberries
The frozen blueberries were crushed with a mortar and pestle until liquidy
The mass of an empty 250mL beaker was measured with a scale
The crushed frozen blueberries were transferred into the 250mL beaker to get a total mass of 202.25g
The total mass of the beaker with frozen blueberries was measured
The beaker with the frozen blueberry mixture is heated with a hot plate at 100℃ for 10 minutes
The heated berries were stirred with a glass rod during the heating process
The beaker with frozen blueberries is removed from the hot plate
The mixture was set to simmer at room temperature for approximately 1.5 hours to reach 25℃
The mixture was sieved with a sieve into another 250mL beaker to remove solid residue
Prepare 5 of the following: chronicle flasks (250mL), beakers (50mL), filter papers, funnels
A 3mL pipet is used to transfer the sieved frozen blueberries onto 5 different flat filter papers
The filter paper is spun around to spread the mixture evenly
The filter papers are then folded and set on the funnels
The funnels containing the filter paper with the frozen blueberries are placed on 5 different 250mL chronicle flasks
Each chronicle flask is labeled with a marker and pen with the different temperatures (20℃, 40℃, 60℃, 80℃, 100℃)
20mL of distilled water is measured with a volumetric cylinder
The 20mL of distilled water is transferred to a 250mL beaker
Heat the beaker to 40℃ (measured with a thermometer)
Repeat steps 17-19 with 60℃, 80℃, and 100℃
Repeat steps 17-18 and leave the beaker outdoors until 20℃ (experiment done in the winter)
The different temperature of distilled water is poured through the filter paper with the frozen blueberries
Each mixture is left to completely filter
Another pipet is used to transfer the filtered frozen blueberry extracts into 5 different cuvettes
Each cuvette is measured with a spectrometer
Each data (different temperatures) is recorded
3 repeated readings are taken for each temperature
Risk Assessment
Raw Data
Simplified Data
Calculations
Beaker: 102.25g
The total mass of the beaker with crushed frozen blueberries: 202.25g
So the mass of crushed frozen blueberries: 202.25g - 102.25g = 100.00g
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