SOP: Estimation of Total Carotenoids
GIFSQ — Global Institute for Food Safety & Quality
Principle
The total carotenoid content — carotenes, xanthophylls and xanthophyll esters together — is estimated from the petroleum ether extract of the sample without chromatographic separation, by measuring the colour at 452 nm against a β-carotene standard curve.
Apparatus required
- Volumetric flasks, 100-ml
- Spectrophotometer or colorimeter
Reagents
a. Petroleum ether extract of the sample, prepared as in SOP: Estimation of Beta-Carotene (the unadsorbed extract, before chromatography).
b. Acetone.
Procedure
Pipette an aliquot of the petroleum ether extract of the sample (unadsorbed) into a 100-ml volumetric flask containing 3 ml of acetone
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Dilute to the mark with petroleum ether
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Measure the colour at 452 nm
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Read the concentration of carotenoids from the β-carotene standard curve
Calculation
Calculate the total carotenoid content in the same manner as for β-carotene, using the concentration read from the curve:
μg of carotenoids per 100 g = [Concentration of carotenoids in solution as read from the standard curve (μg/ml) × Volume made up (ml) × Dilution × 100] ÷ Wt of sample (g)
Where,
- μg of carotenoids per ml = concentration read from the β-carotene standard curve
- Dilution = dilution factor applied to the extract
- Wt of sample = weight of the sample taken (g)
Precautions
- Use the petroleum ether extract before it is chromatographed — after adsorption the biologically active fraction is separated off, so only the unadsorbed extract represents the total carotenoids.
References
Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.
- Kemmerer, A.R. & G.S. Fraps, Ind. Eng. Chem., Anal. Edn., 15, 714 (1943).
- Wall, M.E. & E.G. Kelley, Ind. Eng. Chem., Anal. Edn., 15, 18 (1943).