Caramel Colours: Manufacture, Properties and Formulation Considerations
Colour of food or beverage is one of the first attributes recognized by the senses of the purchaser and consumer of the product. The familiar and pleasant appearance of a host of those products is provided by caramel colour.
Caramel colours are amorphous, brown to brownish materials resulting from the carefully controlled heat treatment of food grade carbohydrates in the presence of small amounts of food grade acids, alkalis or salts. This definition is in essential agreement with definitions contained in the U.S. Standard of Identity for Caramel. Code of Federal Regulations, Title 21, Sec. 7385; the monograph on caramel as in Food Chemicals Codex, Fourth Edition, the EEC Regulations on Colouring Matter, and the U.K. Specification for Caramel use in Foodstuffs.
Caramelization has been carried out as long as food has been cooked. Caramel colour, sometimes referred to as burnt sugar, first gained commercial importance as an additive in brewery products — porter, stout, dark beers and ales and as a colourant for brandy. In 1858, the first known published technical study of caramel authored by M.A. Gelis appeared in a French journal. Since then, other published papers and patents have added to the general knowledge of this product.1
The chemistry of caramelization is complex and difficult to reduce to simple terms. Larger carbohydrate molecules are reduced in size under the influence of acid, heat and pressure. Then a type of condensation or polymerization takes place in which the simple sugars are recombined into larger complex colour bodies. These are similar to those found in common foodstuffs such as roasted coffee, broiled meats and baked goods.
Modern caramel colour production in heat controlled closed vessels bears little resemblance to the early preparation by heating sugar in a pan. The introduction early in this century of acid stable caramel colour types for the soft drink industry was a significant achievement.
The ingredients or raw materials which may be used in the preparation of caramel colour in the United States are listed in the Standard of Identity for Caramel (CFR 21, 73.85). The edible carbohydrates are glucose, invert sugar, malt syrup, molasses, sucrose and starch hydrolysates and fractions thereof. Corn starch hydrolysate, that is, corn syrup of high dextrose equivalent is employed most frequently by the caramel colour industry.
Certain acids, alkalis and salts as provided by the Standard of Identity may be used as catalysts in amounts consistent with good manufacturing practice to assist caramelization. These acids, alkalis and salts meet Food Chemical Codex specifications.
Caramel colour is generally made batchwise in stainless steel reactors equipped with an agitator, heating and cooling coils or jackets of size to contain up to several thousand gallons of liquid sugar. Some types of caramel colour are best made in open or atmospheric kettles while other types require closed pressure reactors, capable of up to 70 psi gauge pressure with temperatures up to 320° F.
Product lines, pumps, filters, storage tanks and all contact surfaces are preferably made of 316 stainless steel due to the acidic nature of caramel.
In a typical batch, the required amount of sugar is introduced into the reactor, and warmed to facilitate mixing with liquid catalyst. The vessel is then closed and the reaction proceeds for several hours under controlled temperature and pressure conditions. The composition of the catalyst, the ratio of sugar to catalyst and the pH-time-temperature relationships will vary according to the type of caramel colour being produced. When the desired colour intensity is reached, the batch is cooled, filtered and pumped into storage.
In-process controls are the key to the production of uniform caramel colour batch after batch. Laboratory tests control the composition of the material prior to caramelization. Time-temperature-pressure records are kept during the process. Test samples are withdrawn at intervals during the reaction cycle for the determination of colour development, and to monitor changes in specific gravity, pH and viscosity. The reaction end point is determined from a combination of these various factors.
Before a caramel colour is offered for sale, a complete evaluation must be made of the finished product. Primarily a caramel colour user looks for colouring strength and compatibility with other ingredients. The following tests are made by the caramel colour manufacturer to measure these and other critical characteristics:
- Colour Measurement: Early methods were generally visual – for example the Klett Colourimeter and the Lovibond Tintometer. While useful, these visual comparison techniques have now generally been replaced by spectrophotometers which are precise and yield reproducible results. Values are expressed as absorbance, or in some cases percent transmission. The FCC definition of Colour Intensity is defined as the absorbance of a 1 gram caramel colour per liter dilution (using distilled water) as read on a quality spectrophotometer at a wavelength of 610 nanometers through a 1 cm square cell.
- Weight: Specific gravity is obtained by hydrometer or densitometer, and the weight per gallon can be determined by multiplying this number by 8.328, the weight of a U.S. gallon of water.
- Percent Solids: This can be approximated from sugar tables that relate specific gravity to percent solids or determined more exactly by classic AOAC procedures or densitometer.
- pH: This is usually determined with a commercial glass electrode and pH meter. The pH of a caramel colour for soft drinks will range from 2.5-3.5. Liquid caramel colours for other uses may have pH values up to 5.0. Certain powdered caramel colours may have a pH as high as 8.0.
- Viscosity: Generally, the caramel colour manufacturer tries to make a product for soft drinks with as low a viscosity as possible while maintaining the desired specific gravity. A beverage caramel colour that has been incorrectly processed will show this in an abnormally high viscosity. Measurement is made by means of a viscometer at 20° C and is expressed in centipoises.
- Haze: The haze point is an indication of the resistance of the caramel colour to a concentrated phosphoric acid solution. One part of the acid is added to two parts of caramel colour and the mixture is heated in a boiling water bath. A drop is taken out every five minutes, placed in a tube of distilled water and the solution observed for clarity. The time at which the drop makes a turbid solution is recorded as the haze point.
- Gel: The gel point is an extension of the haze, and is the time at which the acid-caramel mixture is no longer fluid.
- Resinification: The shelf-life of a caramel colour is an important consideration for a buyer, and the resinification test gives an indication of the length of time the colour will remain free-flowing. A small amount of caramel colour is sealed in a glass ampule and held at 100° C. The number of hours required for this sample to reach a point where it will not flow is the resinification value. Each 20 hours of resinification value is approximately equivalent to one year of storage under normal conditions.
- Ash: As the term implies, the ash is the percent of material remaining after combustion.
- Trace Metals: Measurement of iron, copper, lead, mercury and arsenic are all important to a complete analysis of caramel colour. Atomic Absorption Spectroscopy is the preferred method of analysis of many metallic elements found in just trace amounts in caramel colour.
- Isoelectric Point:The isoelectric point is the pH at which the colloidal charge is neutral and is established by the ingredients and the caramel colour process. A negatively charged caramel colour has a pH higher than its isoelectric point. The methods used to determine this neutral point are based on the mutual attraction of particles with opposite charges. The procedure in general use employs solutions with a known colloidal charge to detect the pH at which the charge of the caramel colour particles changes. Since a soft drink concentrate requires negatively charged caramel colour, an isoelectric point of pH 1.5 or lower is recommended.
- Other: Many useful and relatively simple lab tests can be used to check a given sample of caramel colour to predict its performance in a wide variety of applications. Among these are compatibility tests with various food acids, salts and with alcohols at various proofs.
Caramel colour is a complex mixture of compounds, some of which are in the form of colloidal aggregates. Caramel usually is a dark brown to black liquid or solid having an odor of burnt sugar and a somewhat bitter taste. Caramel colours have isoelectric points and pHs varying over a wide range.
In colouring a product with caramel, the particles of the caramel colour must have the same charge as the colloidal particles of the product to be coloured. If a caramel colour is put into a colloidal solution with opposite-charged particles, the particles will attract one another, form larger, insoluble particles and settle out. For example, a soft drink contains negatively charged colloidal particles, and therefore, a negative caramel colour should always be used.
The requirements for caramel colours vary with different applications. Where special qualities are desired, the manufacturer can develop a colour with the proper characteristics. In this case, the specifications are mutually agreed upon in discussions between the caramel colour manufacturer and the user. They are precise and set within narrow limits to insure uniformity from shipment to shipment. At this time, test procedures are also agreed upon. The manufacturer then specifies his raw materials and process conditions so that the finished caramel colour will meet the established standards. The plant’s laboratory follows rigid control procedures to make certain the finished product is within the defined limits.
Thousands of companies use caramel colours in the manufacture of various foods and beverages. Through the years, a great deal has been learned about the use of this ingredient. The following are items to be considered in developing formulations with caramel colour.
- Soft drinks: These account for the largest portion of caramel colour usage in the world. Single-strength caramel colours are used in colas, generally in concentrations of less than four grams per liter. Double-strength caramel colour, which adds less than one calorie per liter of beverage (making it the industry preference for diet drinks), is used in concentrations of less than two grams per liter.A third type of caramel colour is commonly used in such soft drinks as root beer. It contributes to the formation of a foamy head and an attractive red hue.In carbonated beverage concentrates, caramel colour serves as an emulsifier to impede separation of flavor oils. A “plug” in the neck of a concentrate bottle or a “ring” in the neck of a beverage bottle is usually a flavor oil emulsion breakdown, caused either by the average flavor oil particle size being larger than three microns (if caramel colour is the emulsifier) or a problem with the flavor oil-gum emulsion. Caramel colour is sometimes the culprit; however, what appears to be caramel colour are more frequently caramel-coloured flavor oils that have come out of dispersion.Ginger ale concentrates generally are alcoholic, so the caramel colour must not only be negatively charged; it must also be able to withstand the alcohol concentration, or precipitation will occur. Such precipitation is often reversible by adding small quantities of water. The addition of too much water must be avoided, or clouding of the ginger ale extract can result. Caramel colours with the stability to withstand high alcohol concentrations are available and preferable.
Manufacturers of caramel colour who use steel drums face the risk of product contamination caused by drum lining failure. This can begin with the simple bump of a forklift against the drum. In such a scenario, the container’s protective lining may crack, bringing caramel colour into contact with raw steel. Soft drink caramels, with their 2.5 to 3.5 pH, will attack the metal, possibly causing pinhole leaks and increasing the iron content of the caramel. As a result, end products may have a metallic tang to their taste. Plastic drums prevent the possibility of this problem ever occurring.
- Alcoholic beverages:Caramel colours also appear in beers, whiskeys, wines, rums and liqueurs. Those caramel colours that are stable in 120 to 140 proof alcohol are the most commonly used.Consideration must be given to the charge of the caramel colour selected. Beer contains positively charged proteins. Therefore, the addition of negatively charged caramel creates a cloud that agglomerates into particles large enough to precipitate quickly. For this reason, positively charged beer stable caramels should be selected.Negatively charged caramels (and, sometimes, specifically formulated spirit caramel colours) work well in whiskeys, wines, rums and liqueurs.
Wines clarified using gelatin and tannic acid require enough tannic acid to remove all the gelatin. Otherwise, the remaining positively charged gelatin and negatively charged caramel will precipitate and be removed in the filtration process, making the wine perceptibly lighter.
High (151) proof rums are best coloured with a sucrose-based spirit caramel. These products tend to have a higher alcohol tolerance than glucose-based spirit caramels.
For improved stability in liqueurs (especially creme liqueurs), it is important to premix the caramel with alcohol before adding the other ingredients. When using dairy ingredients, it is necessary to control the pasteurizer temperatures to prevent scorching the creme. These scorched creme particles tend to rise, giving the impression of caramel colour failure.
Colour fading may occur when caramel coloured alcoholic beverages are bottled in clear glass. Such products will evidence moderate fade under fluorescent lights; but in direct sunlight the rate of fade increases tenfold. Dark glass bottles are preferred for alcoholic beverages.
- Food products: Other products call for other caramel colour characteristics. As an example, soy sauce, which can be preserved with up to 15 percent salt, demands a caramel colour with the proper salt stability. Usually, positively charged caramel colours have inherent salt stability; special formulas provide stability in negative soft drink caramel colours. Positive types of caramel colour give finished soy sauce a hue more closely resembling that of the naturally fermented products.Still other products necessitate the addition of other agents to obtain the proper colour. In chocolate milk, caramel colours can create an almost muddy appearance. That can be countered by adding approximately 0.01 percent by weight of FD&C Red #40, which imparts “Dutch” chocolate shades. Adding a small amount of certified blue and yellow produces more of a brown chocolate shade.In cookies, very pleasing dark shades can be achieved by combining caramel colour and alkali-processed cocoa.
Sausage casings are commonly dipped in solutions of caramel colour and other colours to give them the desired tone. Here, one problem to guard against is that of bacteriological contamination of a solution held too long or inadequately protected. Caramel colours themselves are essentially sterile: with their high solids content and acidic properties, they’re not subject to bacterial attack until diluted.
Yellow spirit-type caramel colours combine well with FD&C Blue #1 to create a palette of greens. These formulations are used for such products as decorative sugars, like those sprinkled on Christmas cookies.
In some instances, caramel colours are easily incorporated into food products just as they are. Milk, for example, takes on a pleasing “eggnog” shade with the use of DDW #528, a yellow spirit-type caramel colour. That colour is also excellent for giving baked or microwaved poultry an “oven roasted” appearance.
Soups and gravies containing meat products and coloured with caramel often give a consistent but slightly different shade before and after retorting. Both positive and negative caramel colours work well in this application, depending on the shade desired. Positive caramel colours generally contribute more red hue.
Spice blends normally incorporate caramel colour powders with few problems.
Caramel colour is used to enhance the attractiveness of baked goods by supplementing the inadequate and irregular colouring power of refined ingredients in rye, pumpernickel, specialty breads, fillings, toppings, cakes and cookies. Several types are used. These include single and double-strength liquid and powdered caramel colours. Caramel colour in a powdered (less than 5 percent moisture), free-flowing state is prepared by removing water by drum or spray dryers. This dry product is particularly useful in food systems such as prepared mixes where free moisture is unwanted.
Positively charged caramel colours consistently work well in malt vinegar. However, cider and distilled vinegars can behave erratically in production. Negative caramel colours that work perfectly in one batch of vinegar may not work in the next batch of the same type. The exact cause of this problem is not known, but changes in bulk vinegar suppliers, even in alcohol and acetobacter nutrient sources may be involved. Vinegar bottlers are well advised to make a 24 hour lab test with a new batch of vinegar whenever they change anything.
In addition to those applications here detailed, caramel colours are used in a wide variety of products including canned meats and stews, table syrups, pharmaceutical preparations and meat analogs based on vegetable proteins.
Other considerations: Caramel colour is a product whose colour and viscosity increase with age. Those who use small amounts should be careful not to order too large a quantity, because, depending upon storage temperatures, the caramel colour in a 2-year-old drum could be significantly darker than that in a fresh drum of the same product.
Caramel colour is generally recognized as safe (GRAS) as a miscellaneous and/or general purpose food additive under CFR section 182.1235, and is deemed to be GRAS by the Flavor and Extract Manufacturers Association, FEMA Number 2235. Caramel colour is permanently listed and exempt from certification for use in colouring ingested and topically applied drugs and for use in colouring cosmetics, including cosmetics applied to the area of the eye.
Purity specifications are to be found in the third edition of the Food Chemicals Codex, The National Formulary XV, and the World Health Organization’s Composium of Food Additive Specifications-Volume 1, 1992.
Labeling: It is the opinion of D.D. Williamson & Co., Inc. that full label disclosure requirements are met with the words “caramel colour.” If other colours are used in conjunction with caramel colour, we believe that caramel colour could either be included in a separate list of colours or be covered under the words “artificially coloured.”
The percentage of caramel colour needed to impart the desired colour is normally so low that caramel would have no measurable impact on the nutritional profile of a product. Even though caramel is made from edible carbohydrates, the metabolic calorie content of double-strength caramel colour is less than one calorie per gram. The reason is that the starting carbohydrates are converted by caramelization to high molecular weight colour bodies which are not readily absorbed or metabolized.
Caramel colours made under the standard of identity contain no substances forbidden by the Jewish Dietary Code and are kosher, but as most caramel colours in the United States are made from corn syrup, they are not considered acceptable for use during Passover. Caramel colour made from cane or beet sugar under rabbinical supervision and certified as “Kosher for Passover” is available.
1Gelis, M.A. 1858, Action de la Chaleur sur les Substances Neutres Organiques; Edu du Caramel et des Produits Torrefies, Ann. Chim. Phys. (3) 52:352.