Color and haze measurement of fruit drinks and carbonated beverages

FAQ: “I have worked with a company measuring the color of sports drinks. Now this company is interested in fruit drinks and also in carbonated soft drinks. Have you worked with these types of beverages? Any advice or recommendations?”

Fruit drinks contain:

  • water
  • corn sweeteners
  • may contain some fruit juice or fruit solids
  • flavors (oil emulsions)
  • may have clouding agent which is usually citric acid. Putting in a clouding agent to create a hazy appearance is a marketing decision which depends on the consumer association with the type of drink.

In a fruit drink, whether there is any natural fruit juice or not, the appearance of haze can be created by the presence of oil flavor emulsions and/or clouding agents such as citric acid. These are added on purpose to create a hazy appearance in some flavors of fruit drinks such as pineapple, lemonade, grapefruit and guava where the consumer expects some scattering.

For other fruit drink flavors such as apple, cream soda or grape the consumer does not have the expectation of a hazy appearance and no additional clouding agents are added.HunterLab can measure both lot-to-lot color and haze (or no haze for clear drinks) inherent in different fruit drinks.

If the beverage is carbonated (a separate source of scattering), it should be decarbonated to remove the carbonation as an unnecessary cause of scattering (independent of color) and measurement variation.To de-carbonate the beverage, place the liquid sample in a sonicator (there are a number available but I have seen a Branson Sonicator in successful use in the lab) that breaks up the carbonization by bombarding with Ultrasound for 60 seconds. Some care has to be taken that the carbonated beverage be placed in a container at least twice the volume of the beverage because when the ultrasound pummels the carbonization, the release of carbon dioxide gas can effervesce suddenly.

Another low-tech option to decarbonization is to place an air hose from the normal lab air supply into the beverage and gently run the air for about 4 minutes. The slow stream of air bubbles break up the carbonization gradually.

Carbon Blackness [My], Jetness [Mc], Undertone [dM] and Tint Strength [T]

“Carbon black, also called charcoal black lamp black, pigment black, soot or black carbon, is a fine particle carbon pigment obtained as soot from the incomplete combustion of many different types of organic materials, such as natural gas, or oil. Carbon black is usually a fine, soft, black powder. It is very stable and unaffected by light, acids and alkalis. It is commonly used in printing and lithograph inks and in Chinese ink sticks. In industry, carbon black is used as a filtration material and a filler /pigment in coatings, rubber, plastics, paints, carbon paper, and crayons. Continue reading

What is the stability of the APHA/Pt-Co/Hazen liquid color standards?

Per Section 6.2 of ASTM D1209 Standard Test Method for Color of Clear Liquids (Platinum Cobalt Scale):

“When properly sealed and stored the standards are stable for at least a year and do not degrade markedly for 2 years.”

 Our industrial experience is that if kept properly stoppered in amber bottles, the APHA/Pt-Co/Hazen visual color standards do not degrade significantly for longer than 2 years but this is the time frame that most sources reference as optimal.

If you have a dated APHA/Pt-Co/Hazen 500 liquid color standard, one validation method would be to see if it still meets the absorbance tolerance limits of ASTM D1209 Table 1, and is effectively clear (ASTM D1003 Haze% < 2).

A literature reference on stability of the APHA/Pt-Co/Hazen color standards can be found at:

Scharf, W. W., Ferber, K. H., and White, R. G., “Stability of Platinum-Cobalt Color Standards,” Materials Research and Standards, Vol. 6, No 6, June 1966 pp 302-304.


Color Measurement of Wine

Wine is a natural product where some color variation is expected and accepted. High color comes from high anthocyanin content and high tannins associated with red wines. Color varies with wine processing practices, particularly fermentation temperature. Co-pigmentation in wine and berry colors, related to presence of anthocyanins, enhances the wine color. Continue reading

What is Hunter Whiteness Index?

Hunter Whiteness Index [WIH]

There are at least half a dozen whiteness indices in use today, and a similar number of legacy whiteness indices no longer in use. There are subtleties among them and it is important to know the forms of these whiteness metrics and conditions for which they are derived for. In general, a material will exhibit high whiteness if the material reflectance has high and even reflectance, near 100%, across the visible spectrum.

Continue reading

Do you have a source for EP Opalescence Standards?

The reference document that defines the visual EP Opalescence scale is:

EP 2.2 Physical and Physico-Chemical Methods for color and opalescence

EP – European Pharmacopoeia, Section 2.2 Physical and Physico-Chemical Methods, Unit European Pharmacopeia, Strasbourg, France (1997: 15-16)

This method describes the visual evaluation of scattering or opalescence in near clear liquids, typically pharmaceutical, relative to distilled water being a perfect clear.

There are two types of physical liquid standards for visual turbidity or opalescence – Formazin solution (with or without stabilizer) and polymer beads (polystyrene micro spheres). The Formazin solution is the historical liquid scattering standard but the polymer beads is considered more stable and homogenous.

Section 2.2.1 Clarity and Degree of Opalescence of Liquids in the EP 4th edition defines a Formazin Primary Opalescent Liquid Suspension (rated at 4000 NTU per EP 5th edition) as a solution of hydrazine sulphate solution and hesamethylenetetramine solution which is stable for 2 months stored in glass.

The EP 4th edition further defines a Formazin Standard of Opalescence (rated at 60 NTU per EP 5th edition) as a dilution of 15.0-ml of the Formazin Primary Opalescent Liquid Suspension (4000 NTU) to 1000.0–ml of water. This suspension must be freshly prepared and stored for no more than 24 hours.

To make the EP Reference suspensions or OP – Opalescence standards, the Formazin Standard of Opalescence (60 NTU) is mixed with distilled water in the following proportions to define 4 levels of liquid EPOP Opalescence Standards. Distilled water is nominally a fifth EPOP standard defining no opalescence or scattering.

Table 2.2.1-1 EPOP Standards 0 I II III IV
 Formazin Standard of Opalescence (60 NTU) 0.0 ml 5.0 ml 10.0 ml 30.0 ml 50.0 ml
Distilled Water (fill to 100.0 ml mark) 100.0 ml 95.0 ml 90.0 ml 70.0 ml 50.0 ml
NTU Rating 0 3 6 18 30

Sources for EPOP Liquid Opalescence standards are:

Hach Company

Loveland, CO 80538 USA


Hach offers the STABLCAL Reference Suspension Set that consists of a range for EP Opalescence Standards per EP is 0 (distilled water >0.1), 3, 6, 18, 30 NTUs. Given the 2-year stability, stabilizers will have been added to these liquid EP standards.

Hach STABLCALC set of EP Opalescence Standards

Hach STABLCALC set of EP Opalescence Standards

Another source for the Formazin Primary Opalescent Liquid Suspension (rated at 4000 NTU) and EPOP Liquid Opalescence standards (rated at 0 – ­30 NTU) is:

RICCA Chemical Company

Arlington, TX 76094 USA


Reporting of EP Opalescence using a HunterLab Sphere Instrument and EasyMatch QC Software

As of EasyMatch QC version 4.82 and higher HunterLab has implemented a correlation method to the EP Opalescence scale based on these standards and is able to report EPOP-10mm (D65/10) for liquid samples measured in a 10 mm path length transmission cell. EPOP values are reported to tenths of a unit, along with NTU values as well.

Is it possible to create ASTM traceable haze standards above 30%?

The current, available ASTM D1003 Haze Standards have nominal Haze% values of 1, 5, 10, 20 and 30 with air (transparent solids) or the transmission cell filled with DI water being 0 (transparent liquids). Here are some thoughts on further options. Continue reading