1. Sweet paprika extractable color determination
by modified ASTA 19 method

OBJECTIVE

To determine absorbency of the 2-propanol based sweet paprika extract, and consequently ASTA color grade for sweet paprika.
 

THEORETICAL BACKGROUND

Paprika powder is obtained by the grinding of pods from the dried sweet red peppers Capsicum Annum. The name “paprika” is Hungarian, but it is also known as pimento (Spanish) and Spanische  pfeffer. Paprika is of Mexican/American origin and it was brought to Spain on the caravel Santa-Maria to be first cultivated in the garden of Queen Elizabeta in Seville. Nowadays, paprika is one of the most consumed spices worldwide and the best quality paprika originates from Hungary and Spain. The world consumption is between 50,000 and 60,000 metric tons per annum, and the trends are showing continuous growth.

Only the highest quality, ripe, intensely colored pods are used to make paprika. Such pods have the highest content of carotenoids such as  capsanthin, capsorubin, carotene, criptoxanthin, zeaxanthin and xantophyll in traces. Several grindings are necessary to achieve the correct powder texture. This aromatic powder is deep red to red-orange in color; its flavour is mildly sweet and non pungent.  

There are several areas of importance when evaluating paprika quality:

• Organoleptic characteristics such as color, flavor and aroma,
• moisture and
• microbiological specifications.

Paprika is normally classified by its extractable color (ASTA color) and this important factor determines the price of the final product. The lighter color product (more orange-red) will have a lower ASTA color rating and consequently a lower price. ASTA is the abbreviation for the American Spice Trade Association, a USA based international company which sets the spice specifications and standardized methods for spice analysis. ASTA Color units refers to the international standard for measuring the extractable color of paprika pods and powder, which is determined by the spectrometric method. There are various available color grades for paprika:

• ASTA Color minimum 160 (160-180)
• ASTA Color minimum 140 (140-160)
• ASTA Color minimum 120 (120-140)
• ASTA Color minimum 100 (100-120)
• ASTA Color minimum 80 (80-100)
• ASTA Color minimum 60 (60-80)

Some producers even offer paprika which has ASTA Color 50. That quality has mostly a culinary application, where color of the product is not the most important parameter. What paprika quality will be used is determined by the final application. If the final product color is the main organoleptic attribute, the highest quality paprika and the more expensive one will be used and vice versa.

Paprika quality is largely influenced by the storage conditions: time and temperature. Paprika should be stored consistently in a cool (5-10 °C) and dry environment, away from direct sunlight. Improper storage at 20-25 °C causes color loss of 1% every 10 days. If stored properly, paprika is good for up to 18 months.
 

CHEMICALS

• propan-2-ol, 99 %
• standard color solution (0.5 mg/ml p.a. potassium dichromate in 1.8 M sulfuric acid)
• 1.8 M sulfuric acid
  
   

MATERIAL AND EQUIPMENT

• 250 ml Erlenmeyer flask with stopper
• 100 ml volumetric flask with stopper
• 250 ml beakers
• 25ml and 100 ml pipettes
• glass funnel
• filter paper – black ribbon
• lab scale
• blisters
• plastic droppers
• Spektra^TM spectrometer
• samples of sweet paprika
   

HAZARDS
 

	Potassium dichromate is very toxic and dangerous to the environment. It is harmful in contact with skin and may cause sensitization by skin contact. It is toxic if swallowed. Wear protective gloves and goggles and avoid release to the environment. R: 49-46-21-25-26-37/38-41-43-50/53 S: 53-45-60-61
	Sulfuric acid is corrosive and causes severe burns. Wear suitable protective clothing, gloves and eye protection. R: 35 S: 26-30-36/37/39-45
	2-Propanol is irritating and highly flammable. Inhalation may cause cough, dizziness, drowsiness, headache and sore throat. It may cause dry skin and redness of eyes. Wear protective gloves and goggles. R: 11-36-67 S: (2-) 7-16-24/25-26

PROCEDURE

Sweet paprika extractable color is determined by measuring 2-propanol extract absorbency using the blue LED. The experiment is performed using the simplified dropper approach.

Weigh 0.1 g of sweet paprika into the 250 ml Erlenmeyer.  Add 100 ml of 2-propanol, close the Erlenmeyer and mix well.  Leave it in the water bath at 70°C for 3 hours or at room temperature in dark for 16 hours. Cool down the extract (in case the extraction has been at 70°C) and filter. Discard the first 10ml of the filtrate. Pipette 25 ml of the filtrate into a 100 ml volumetric flask. Dilute to volume with 2-propanol and mix well. Fill one plastic dropper with the prepared solution from the volumetric flask and the other with 2-propanol. Determine the absorbency of the extract using 2-propanol as a blank.

Measure 10 drops of the 2-propanol into the first blister hole, and 10 drops of the paprika extract into the second, third, fourth and fifth blister holes.  Measure transmittance of each sample and calculate absorbency.

Determine the absorbency of the standard color solution using sulfuric acid as a blank.  Fill in the plastic droppers with standard color solution and sulfuric acid. Measure 10 drops of the sulfuric acid into the first blister hole, and 10 drops of the standard color solution into the second, third, fourth and fifth blister holes. Measure transmittance of each sample and calculate absorbency.

Based on the absorbency results, standard color solution concentration and paprika extract concentration, calculate the ASTA Color units.
 

CALCULATIONS

ASTA Color units = Avz x 200 x Cst / Ast x b

where:

Avz - paprika extract absorbency: average value
Cst - potassium dichromate standard color solution mg/ml
Ast - potassium dichromate standard color solution absorbency
b – paprika extract concentration mg/ml
 

RESULTS
 

Developed and prepared by: Dušanka Dimitrijevič, Živilska šola Maribor, Slovenia