INDUSTRIAL
and
ENGINEERING
CHEMISTRY ANALYTICAL EDITION
+
H a r r i s o n E. Hawe, Editor
Analvsis of Caramel Color J W. R . FETZER I nion Starch and Refining (‘ompan?, Granite ( : i t > , Ill. Sixteen million pounds of caramel colorburnt sugar coloring-are produced annually in the United States for use in the beverage, food, and pharmaceutical industries. No uniform methods for the analysis of caramel color have ever been published, and the author presents this paper on analytical procedure which will evaluate a caramel color not only for type but also for quality.
C
ARARIEL color, or burnt sugar coloring, is used exten-
sively in carbonated beverages, distilled liquors, wines, pharmaceuticals, extracts, bakery products, candy, soups, and baked beans. Figures on the amount manufactured are not available, as many concerns make their own coloring. According to the 1929 census of the Department of Commerce, fifty-three establishments were producing 1,450,000 galloni of caramel. More recent comparable data are not available but it is believed that there are fewer producers of caramel today. The 1935 census gives a production of 1,550,000 gallons and an estimate of production today would be in excess of 1,600,000 gallons. This increase is attributable to increase in amount of carbonated beverages consumed. Very little has been published about either the manufacturing or testing of caramel color. Probably the best article is that of Salamon and Goldie, published in 1900 (6). These authors presented data on its manufacture, and their tests in modified form are largely in use today. Brewers’ caramel has received more attention than caramel for carbonated beverages, although the latter requires a caramel of more specialized characteristics. The manufacture, with few exceptions, is carried on by “burners” who employ rule-of-thumb methods, so that there is considerable variation in the finished product. There are many methods of evaluating caramel, each manufacturer having his own tests for standardization of his product. Consumers, for the most part, are comparatively small users who do not test the caramel, but once they have a satisfactory source of supply will change only under the most unusual circumstances. Large users of caramel, with well-equipped laboratories, have their own tests, peculiar to their product. Their experience with various makes of caramel, in many instances, has been as unsatisfactory as that of the small user, so that they are equally conservative with regard to changing their source of supply.
The trouble with cararnel color is probably due to the fact that the conditions which a caramel must meet in specialized uses, such as carbonated beverages and pharmaceuticals, involye several characterist’ics which are equally important. Too often one is overemphasized or overlooketl. The laboratory has offered little aid to the user who ivoulrl resort to a chemical analysis. Probably the greatest difficulty lies in the multitude of methods in use, with the consequent lack of uniformity in evaluation by different laboratories. I n addition, most laboratory analyses are not sufficiently comprehensive to cover caramel in general, but are built around a specific use. Even the simple test of tinctorial or coloring power of a caramel varies between laboratories, because of failure to follow a uniform method of measurement This paper is presented in the interests of a standardized procedure for the analysis of caramel color. The tests include not only those that have been developed in the author’s laboratory but those of consumers and manufacturers, modified in some instances to fit t’he usual laboratory practice and to obtain a more general application. The tests given will evaluat’ea caramel both as t o quality and type.
Caramel Types Caramel is used in a wide range of products and is 1nanufactured in a number of types, each designed for a specific purpose. These include types for carbonated beverage manufacturers (including acidproof, nonacidproof, and foaming) brewers, distillers, bakers, and confectioners. Carbonated beverages, extracts, and distilled liquors require the highest quality of caramel. Caramel satisfactory for bakery and ice cream use may be entirely unsuitable for beverage use. True beer caramels cannot be used for carbonated beverages, although they serve satisfactorily in the bakery, in ice cream, and in candy. Carbonated beverage caramels, as a rule, cannot be used for hard candy because of t’heir high acid content, which ~voulclcause inversion in the candy. Various types of caramel may be used in carbonated beverages. Thus, ginger ales and cola beverages require an acicifast and tannin-resistant caramel. Root beer and cream soda do not require an acid-fast caramel, but one with good tannin resistance. If the root beer is a true root, extract, the tannin requirements are greater than if synthetic flavors are used. However, an acid-fast caramel with high tannin resistance can be used in all carbonated beverages. Thus, any consideration of caramel quality must take into consideration the service to which the caramel is put. -4lthough an apparently poor carhmel may give the best of service in an isolated instance, it is far safer to demand a high laboratory ~
350
INDUSTRIAL AND ESGINEERING CHEMISTRY
rating, or a caramel designed for exacting service, than to use a lower quality, where the margin of safety may be so small that a slight alteration in ingredients may cause precipitation of the caramel.
A4nalysisof Caramel Laboratory testing of caramel is based on a series of tests under specified conditions which bear a relationship to actual conditions. This series of tests will readily differentiate caramel as to grade and quality, but the individual must determine the grade suitable to his product and the variations in quality that his product can stand. This includes a consideration of shelf life. Thus, a cola or ginger ale dispensed a t fountains and immediately consumed does not require the same acid-fastness in a caramel as the same beverage when bottled, where the shelf life may be over three months. The following solutions are used in the tests: A. Caramel Solution, 1 per cent. Dissolve 10.000 grams of caramel color in distilled water and make to 1 liter. B. Acid Tannin Solution. Dissolve 0.1 gram of tannic acid U. S. P. and 15 grams of citric acid U. S. P. in 100 ml. of distilled water. Refilter until clear. This solution deteriorates rapidly and must be prepared daily. C. Tannic Acid Solution. Dissolve 1 gram of tannic acid U.S. P. in 100 ml. of distilled water. Refilter until clear. Make up solution daily. D. Alcohol Tannin. Dissolve 0.5 gram of tannic acid U. S. P. in 100 ml. of 50 per cent alcohol by volume. E. Alcohol Solution. 50 oer cent bv volume. F. Slcohol Solution; 55 per cent b i volume. G. Alcohol Solution, 60 per cent by volume. H. Alcohol Solution, 65 per cent by volume. For recording observations, the following notations may tie employed: A. Brilliant at end of 24 hours. B. Slight haze at end of 24 hours. C. Slight precipitate at end of 24 hours. D. Medium precipitate at end of 24 hours. E. Heavy precipitate at end of 24 hours. F. Immediate precipitate, in case of acid test during the boiling period. The 1 per cent stock caramel solution should be examined by transmitted and reflected light, recording observations as (1) hrilliant, (2) hazy, or (3) opalescent. After filtering through a 15-cm. (6-inch) filter paper, observations are recorded as (1) clean, (2) suspended matter, or (3) char.
VOL. 10. NO. 7
TINCTORIAL POWER.Probably no other part of a caramel analysis has varied more than the measurement of tinctorial power. As defined by Salamon and Goldie (6), the tinctorial power is the Lovibond reading obtained on a caramel solution, made by dissolving 1 gram of color in 1liter of distilled water, in a 2.5-cm. (1-inch) cell. The trouble may generally be attributed to three causes: Standard Glasses. The usual Lovibond glasses employed in the measurement of caramel color are the Caramel Series No. 52. These slides were designed for the measurement of color in beer (4) and may or may not match the color produced by commercial caramel color. As a rule, beer caramels match very well; distillers' caramels do not, as they contain more red than the No. 52 series. The carbonated beverage caramels lie betvr.een. In reading a distillers' or carbonated beverage caramel with No. 52 slides only, the tendency is to employ too many slides in order to secure a match, resulting in too high a tinctorial power. This can be overcome by adding 0.1 to 0.4 red to the No. 52 series. Light Source. The original Lovibond light for standardization was that reflected from a fog bank by the early morning sun across the meadow from the Lovibond brewery. This is a soft diffused light and may be matched for purposes of standardization by picking a time when similar light conditions exist. The source in the laboratory is the electriclight, and the common tendency of chemists is to employ too much light, resulting in readings that are too low. A good source can be obtained by passing the light of a 50-watt lamp through a daylight glass against white crepe filter paper at a 45" angle from the Lovibond cells. Once a source of light has been established, it' should be adhered to. Cells. The definition of tinctorial power calls for measurement in a 2.5-cm. (1-inch) cell. Many laboratories do not have an inch cell, but do possess 0.63- and 1.25-em. (0.25- and 0.5-inch) cells. In the latter case, the reading on a 0.1 per cent solution is multiplied by two, or the reading on a 0.2 per cent solution is made and called the tinctorial power. This leads to erroneous results, as the Lovibond reading under these conditions is not proportional for all caramel colors and may vary as much as 10 per cent from results obtained by a reading on a 2.5-cm. (1-inch) cell. The British Drug House modification of the Lovibond tintometer is an improvement over the older form. Carbonated beverage caramels require the addition of the red
General Tests SPECIFICGRAVITY.The specific gravity of commercial caramels varies widely, ranging from 34" to 42" BB., with an average of approximately 38.0' BB. d uniform gravity is especially important in carbonated beverage caramels, because when large quantities of caramel are used, as in root beer concentrate, variations in BaumB of the caramel will affect the final gravity of the aoncentrate. High gravities generally result from the burner's failure to produce the necessary amount of color in the burning process. Thus, in adding Tvater to "burnt" mass, he cuts back to the desired tinctorial power, without regard for gravity. Such caramels drain with difficulty and very slowly from the containers. Low gravities are generally the result of an attempt to obtain a freer flowing caramel. With a lower gravity, more color must be produced in the burning process, so that such a caramel must be examined carefully for overburning with resultant failure in quality. Immerse a hydrometer standardized at 15.56' C. (60" F.) in air-free caramel at 15.56' C. (60" F.) and obtain the reading. If a temperature correction is necessary, employ the arbitrary correction of 2.2224" C. (4" F.) equals 0.1" BB. When the sample of caramel is small, pitrticularly if the gravity is high or the viscosity great, it is best to use a Hubbard-Carmick specific gravity bottle, which is designed primarily for asphalt.
FIGCRE 1. DUBOSCQ TYPEOF TINTOMETER
JULY 15. 1938
ANALYTICAL EDITION
series (200) in addition to the KO.52 Caramel Series and i t is advisable to introduce about 0.2 red a t the start, adding the caramel slides until an approximate match has been obtained, after which the effect of an additional 0.1 red on bhe match may be studied. Other types of tintometers are in use. Figure 1 shows a Duboscq type in which a fixed glass standard is used. The degree of variation is measured on the drum, according to the degree of immersion of the plunger above or below the depth of definite solution, matching the glass standard, which is given the arbitrary rating of 100. Figure 2 shows a newer modification of the Duboscq. Lovibond slides are contained in the metal disks as follows: Caramel Series 52
Red Series 200
30 20 15 9.0 8.0 7 . 0 6 . 0 5.0 4 0 0 . 9 0.8 0 . 7 0 . 6 0 . 5 0.4 0 . 9 0 . 8 0 . 7 0.6 0.5 0.4
10 3.0 2.0 0 3 0.2 0 3 0.2
351
The relative viscosity can easily be determined by using
a 50-ml. l l o h r buret, filling with caramel a t a definite temp e r a t u r e i . e., 29.44' C. (8.5' F.)-and collecting 40 ml. in a graduated cylinder. ASH. The ash normally bears no relationship to quality. However, in recent years the hydro1 from refined corn-sugar processing has been used for caramel, which increases the ash content, depending upon the amount used, to as high as 8 per cent. Caramels with an ash content greater than 3 per cent, if intended for use in carbonated beverages, should be examined closely for the effect of ash on flavor.
1.0 0.1 0.1
This comparator has the advantage that the maximum number of slides which can be used is four, which is desirable with the Lovibond system. I n addition, the amount of light passing through the caramel may be altered by the reflector, thus compensating for the brilliance often found in some caramels and also for the differences in light absorption by different combinations of slides. This may also be done in the British Drug House tintometer by the addition of neutral slides, but it has been the author's experience that the employment of these neutral tints complicates rather than aids the matching. To determine the tinctorial power, dilute 50.0 ml. of stock caramel solution A to 500 ml., and read the color in a 2.5-cm. (1-inch) cell, using Lovibond glasses Series 52. iZdd 0.1 to 0.4 red if necessary to secure an exact match.
pH. The p H of a caramel gives an index of its quality and may be measured by either glass or quinhydrone electrodes. The readings b y the former are usually slightly lower. If the quinhydrone electrode is employed, an excessive amount of quinhydrone must be used to prevent drifting and the gold electrode must be kept clean. An undiluted caramel with a p H higher than 6.0 will mold. High p H also indicates an incomplete "burn" or excessive amounts of alkali, both of which mean that the caramel will increase in tinctorial power on aging. Caramels have been examined with p H as high as 9. Carbonated beverage caramels, undiluted, should run from 2.5 to 3.3 (glass electrode). Caramels m-ith pH less than 2.5 are likely to resinify, and have been known to become rubberlike or even turn to a solid within two months. The p H of a 1.5 per cent solution, intended primarily for beer caramels, should run from 4.5 to 5.0 under these conditions, comparable to the fermentation pH. Caramels which give higher or loJTer p H under these conditions when added to the fermenting wort are said to alter the pH sufficiently to change the flavor of the resulting beer. The p H of 1 per cent solution in a carbonated beverage caramel should run approximately 3.5. p H lower t'han 3.3 indicates a caramel with excessive residual acidity. Obtain the pH of a caramel by means of a glass or quinhydrone electrode. To determine the pH of a 15 per cent solution proceed in the same way on a solution of caramel made by dissolving 15 grams of caramel and making to 100 ml. To determine the pH of a 1 per cent solution, take 5 nil. of the above solution, add 70 ml. of distilled xvater, mix thoroughly, and obtain the pH.
VISCOSITY. Relative viscosity is important' with reference to the speed with which a caramel resinifies or ages. Caramels with excessive relative viscosity are usually oT-erburnt and lack acid-fastness.
OF DUBOSCQ TINTOMETER FIGURE 2. MODIFICAT~ON
IRON.Iron in a caramel will often run to excessive limits, entering through the burning equipment, which is often made of mild steel. Only a fern manufacturers employ glass-lined or stainless steel equipnient because of the cost involved. Samples of caramel haye been examined which have contained 2000 p. p. in. of iron. The effect of this iron o n the flavor of a pharmaceutical extract or carbonated beverage can lvell be imagined. The ash is tlissolred in acid and the iron content measured colorimetrically ( 1 ) . Specific Tests for Carbonated Beverage, Pharmaceutical, and Distillers' Caramel
ACIDTEST. This test, JThich is particularly important in caramel color used in cola and ginger ale beverages, has been found adequate by an old manufacturer in evaluating caramel color. Dilute 50.0 ml. of stock caramel solution A to 250 ml. with distilled water, add 7 ml. of concentrated hydrochloric acid (sp. gr. 1,18), cap, and boil gently for 5 minutes. Remove from flame and note whether precipitation has developed. Set aside and record observation 24 hours later. If the color is satisfactory, a measure of residual acid-fastness may be obtained by repeating the above test, boiling for 30 minutes instead of 5 minutes. Water must be added at intervals to maintain a constant volume.
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I\DUSTRIhL .4ND ENGINEERIUG CHEZIISTRY
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To 10 ml. of color add 20 ml. of distilled water, 'mix thoroughly, add 0.5 gram of compressed yeast, and stir until completely suspended. Pour into a fermentation tube and invert for 15 minutes or until all the air has been eliminated. Place tube in position, plug with cotton, and set aside for 48 hours at 26.67" to 32.22" C. (80" to 90" F.). Record the percentage volume of gas produced.
FOAJITEST. Caramels for carbonated beverage use are of foaming and rionfoaming types. The former are used for root beer and the latter for cola and ginger ale beverages. Foaming caramels are used in "mug" root beer, where a large stein is dranx, containing a large head of foam. Caramels can be burnt to have foaming qualities, eliminating any necessity for the addition of saponin or other similar foaming agents. Under the test outlined below, a caramel designed for cola or ginger ale d l give a head of foam lasting from 3 to 6 minutes, n-it,h bubbles that are large and break quickly. A foaming caramel will gil-e a head of fine bubbles last'ing from 30 minutes to 2 hours. Dissolve 10 grams of caramel in distilled water, make to 100 ml., run into a 250-ml. glass-stoppered cylinder, and shake for 2 minutes. Loosen the stopper and place in a water bath at 37.78" C. (100" F.). Observe the time for the head of foam to fall to the liquor surface. E'IGTRE
3. ACID TESTFOR
CARBOSATED
COMPATIBILITY.One of the most serious difficulties in the use of caramel for carbonated beverages occurs when caramel is added to a sirup or extract already containing caramel, or There t v o makes of caramel are used in the same plant. The weaker or inferior caramel m-ill often precipitate out.
BEVERAGE CAR.4lJELS
SEuTn.u. TANKISTEST. These tests are a measure of caramel's resistance to flocculation by extractives that occur in the various carbonated beverages and pharmaceutical extracts.
1. To 80 ml. of distilled water add 10 ml. of stock caramel solution A, then 10 ml. of stock tannin acid solution C, and mix
thoroughly. If clear, set aside for 24 hours and record ohaervations. 2. To 50 nil. of distilled water add 25 ml. of caramel solution, and then 25 ml. of tannic acid solution, and mix thoroughly. If clear, set aside for 24 hours and record observations. 3. To 13 ml. of caramel solution, add 12 ml. of tannic. acid solution, and mix thoroughly. If clear, set aside for 24 hours and record observations. ACID-TAKNiK TEST. This is a combined acid and tannin test. To 75 ml. of acidulated tannic acid solution B, add 5 ml. of stock caramel solution A and 20 ml. of distilled water, and niix thoroughly. If clear, record observations at end of 24 hours. ALCOHOLTESTS. Dissolve 1 gram of caramel in 100 ml. each of 50, 55, 60, and 65 per cent alcohol by volume. Mix thoroughly and record Observations at end of 24 hours. WHISKYTEST. Color 50 ml. of test solution D a distinct brown (the colol: of a 0.2 per cent solution) and observe 24 hours later.
Filter Paper Test. Run 1 or 2 ml. of a 0.2 per cent solution of caramel onto a large sheet of filter paper. The color from a satisfactory caramel m-ill follow the water. The color from an inferior caramel vi11 collect in a spot in the center, and the water will proceed to form a larger circular area. Such a caramel is invariably noncompatible. Solution Test. Dilute 50 ml. of solut,ion A of each caramel to 250 ml. and proceed as follows: Caramel A, ml. Caramel B ml. Distilled d a t e r , ml.
TABLE
FERJIESTATIOS TEST. Some bel-erage manufacturers depend upon the residual acidity of a caramel color to preserve their extracts. The residual acids in a caramel are a combination of those resulting from the catalyst' used-i. e., ainriionium sulfate-and those produced in the burning process-i. e., acetic acid. Titratable acidity data obtained on different makes of caramel are not comparable, since the methods of burning and catalysts used differ. For this reason, pH data are better. 4 s a rule, a pH of a t least, 3.0 is required to assure no fermentation, but this cannot be taken as a final criterion, as there is considerable mriation in the buffering power of caramels, depending on t'he t'ype of catalyst employed and the method of burning. A measure of t,he effectil-eness of the residual acidit'y is bhe fermentation test.
7
PO
I.
4 16
80
PHYSICAL
Brilliant Clea; 38.1
.ilcohol, 5 5 % h l r o h o l , 60%
Viscosity, C. t,8Sc F,): water =29.44' 1 Iron, p. p. m. Too thick t o measure.
14 6 80
16 4 80
EXAMISATIOX
Solution Retained on filter paper Baume Tinctorial power Acid test. 5 minutes 12cid test, 30 minutes Keutral tannin 1 SVeutral tannin 2 S e u t r a l tannin 3 .icid tannin .Ilcohol. 30% IVhiskv test Foam test. minutes Hops test, ,7G Fermentation test Compatibility: Filter paper tesi. Solution test
0
etc. eto. etc.
6 14
80
22.1 A
D A .A .A A
h
Brilliant Clea; 39.1 19.5
Hazy Clea; 37.5 21.0
.-1
F F A A
I
E
A
E .i B
h
F
d
n
B E
C F
Sone
None
Trace
OK OK
OK OK 2.9 2.9 3.6
OK OK 3.3 3.3 3.7
30.
230.
A A i 100
3.0 3.0 3.5 20.
