An Analysis of the Amount of β-Carotene in Carrots

Pixshark. (n.d.). Beta-carotene [Image]. Retrieved April 18, 2015, Retrieved from http://pixshark.com/carotenestructure.htm

By: Roman HodsonMay 7, 2015

UV-Vis Spectrophotometry

Bio 750. (n.d.). Spectroscopy - UV-Vis [Image] Retrieved April 18, 2015, Retrieved from http://www.sci.sdsu.edu/TFrey/Bio750/ UV-VisSpectroscopy.html

• Beer’s Law

• A = εlc

• A = -log(I/Io)

Background/Question

• Beta-carotene is a carotenoid, which gives orange color1

• Beta-carotene is a phytochemical2

• Phytochemicals are found in plants, help reduce risk of disease such as cancer and diabetes2

• Question: Does the amount of β-carotene decrease after letting a sample sit in the dark for a week?

Hypothesis/Expected Results

• Hypothesis: The concentration of β-carotene is expected to decrease after being left to sit in the dark of a laboratory cabinet for a week due to rotting

• Concentration of β-carotene: 74.06 μg/mL 3

• The wavelength β-carotene absorbs: 449 nm 3

Experiment Process/Instrumentation

• Organic/not-organic samples (12 g in 15 mL hexanes)

• Stock solution of 0.1 mg/mL β-carotene

• Vacuum filtration (4x)

• Standard addition solutions of 1.6, 0.8, 0.4, and 0.2 μg/mL

• Spike recovery (1.6 μg/mL)

• 300 – 600 nm range

Experimental Results

400 410 420 430 440 450 460 470 480 490 5000

0.050.1

0.150.2

0.250.3

0.350.4

Organic Sample A

1.6 ppm 0.8 ppm

0.4 ppm 0.2 ppm

Wavelength (nm)

Abs

orba

nce

449 nm

Experimental Results

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.80

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4f(x) = 0.176829255145529 x + 0.0617824222730555R² = 0.99901549274621

Organic Standard Addition A

Concentration (ppm)

Abs

orba

nce

Experimental Results of Fresh SamplesSample Average

Mass of β-carotene

(mg)

Standard Deviation

%RSD Conf. Interval

(mg)

Weight Percent

(%)

Non-Organic

0.157 8 x 10-3 5 0.157 ± 0.014

1.31 x 10-3

Organic 0.125 2.1 x 10-2 17 0.125 ± 0.036

1.04 x 10-3

Experimental Results of Week Old SamplesSample Average

Mass of β-carotene

(mg)

Standard Deviation

%RSD Conf. Interval

(mg)

Weight Percent

(%)

Non-Organic

0.319 0.204 64 0.319 ± 0.343

2.7 x 10-2

Organic 0.184 2 x 10-3 1 0.184 ± 0.004

1.5 x 10-2

Discussion/Conclusion

• Week old data had higher values due to evaporation

• Absorption at 449 nm

• Calculated Limit of Detection: 3 x 10-3 ppm

• β-carotene calculated less than literature3

• Inconclusive results

References1. MAYO Clinic. (n.d.). Beta-Carotene. Retrieved April 18, 2015, from http://www.mayoclinic.org/drugs-supplements/beta-carotene/background/hrb-200588362. American Cancer Society. (n.d.). Phytochemicals. Retrieved April 18, 2015, from http://www.cancer.org/treatment/treatmentsandsideeffects/complementaryandalternativemedicine/herbsvitaminsandminerals/phytochemicals3. Biswas, A.K., Sahoo, J., & Chatli, M.K. (2011). A simple UV-Vis spectrophotometric method for determination of β-carotene content in raw carrot, sweet potato, and supplemented chicken meat nuggets. Food Science and Technology, 44, 1809-1813.