SOP: Colour Value in Turmeric Oleoresin

GIFSQ — Global Institute for Food Safety & Quality

Principle

The colour value of turmeric oleoresin is the E¹%₁cm value at 422 nm; a dilute solution in 95% alcohol is measured spectrophotometrically and the absorbance is multiplied by the appropriate factor for the solution strength used.

Apparatus required

• 100 ml volumetric flasks
• Spectrophotometer with 1 cm cell

Reagents

a. 95% alcohol.

Procedure

Prepare a 0.01% solution of the oleoresin by diluting 1 g to 100 ml in a volumetric flask using 95% alcohol, and diluting 1 ml of this solution to 100 ml with 95% alcohol

↓

Measure the colour in a spectrophotometer using a 1 cm cell at 422 nm

↓

Multiply the absorbance by 1000, which gives the colour value

↓

If the reading is too high, prepare a 0.005% solution, measure the absorbance and multiply by 2000

Calculation

Colour value (0.01% solution) = Absorbance × 1000

Colour value (0.005% solution) = Absorbance × 2000

Where,

• Absorbance = absorbance of the solution measured at 422 nm in a 1 cm cell

References

Ranganna, S., Handbook of Analysis and Quality Control for Fruit and Vegetable Products, 2nd edition.

EOA Specifications and Standards, EOA No. 271, Essential Oil Association of USA, Inc.