Process for the enhancement of caramel colorant

Disclosed is a process for the rapid enhancement of caramel colorant which comprises passing a liquid containing caramel colorant through a size exclusion chromatographic material while subjecting the liquid to centrifugal forces. The process for the enhancement of caramel colorant can be conducted in a relatively short period of time and produces a caramel colorant of improved coloring power and a reduced content of undesirable or non-color contributing substances.

BACKGROUND OF THE INVENTION 
The present invention relates to a process for enhancing the properties of 
caramel colorants, and more particularly, to a process for the color 
enrichment and desalting of caramel colorant utilizing centrifugal size 
exclusion chromatography. 
Caramel colorant is a coloring agent widely used in food, pharmaceutical 
and beverage manufacturing industries, most particularly in the 
manufacture of cola-type soft drinks. The caramel colorant is used to 
impart the amber shade extensively found in carbonated beverages, 
pharmaceutical and flavoring extracts, candies, soups, bakery products and 
numerous other foods. Caramel colorant is made commercially by heating a 
solution of sugar with or without the addition of a catalyst in a process 
known as caramelization. Heating the solution during caramelization causes 
several complex chemical reactions such as polymerization, rearrangement 
and condensation to occur. In currently used caramelization processes, the 
extent of heating is limited because if the heating treatment is too 
extensive, additional reactions occur which impart undesirable 
characteristics to the caramel colorant product such as charring, 
unmanageable viscosities, diminished solubility and instability which may 
lead to the tendency for the colorant to resinify on storage. Commercial 
caramel colorant, which has not been refined beyond the conventional 
caramelization and having a minimum of undesirable properties, contains 
color-imparting solids accounting for less than one-half of the total 
solids contained in the product, the remainder of the solids being 
materials not contributing directly to the coloring power of the mixture. 
Attempts have been made to determine the various constituents in caramel 
colorant by a variety of means but the constituents revealed in 
preliminary tests have indicated the complexity of the product and have 
often dissuaded further investigations. These attempts have revealed 
however that the color-imparting solids of the colorant are of relatively 
high molecular weight whereas the remainder of the materials which do not 
impart color are of relatively low molecular weight. 
The coloring power, or tinctorial power, of caramel colorant is the basis 
on which it is marketed commercially. The higher the coloring power, the 
more attractive the product is to the user. The amber shade produced by 
caramel colorant has become so fixed in the consumer's acceptance of 
certain foods and beverages that when these products have low or lighter 
color intensity, it often causes the food or beverage to be viewed as 
being inferior or lacking in strength. Therefore, it becomes a necessity 
for manufacturers of commercial caramel colorant to have economical 
processes for supplying colorant of high coloring power. Thus, the need 
for efficient and practical processes for the enhancement of caramel 
colorant is present in the caramel colorant, food and beverage industries. 
Over the years, many diverse processes have been developed to enhance the 
coloring power of caramel colorant solutions and to remove undesirable, 
non-color contributing contaminants from the caramel solutions. Examples 
of known processes for producing caramel colorants of increased coloring 
power include separation of a colorant solids concentrate by the addition 
of coagulating or precipitating agents, e.g. ethanol, to the caramel 
colorant solutions; separation of a colorant solids concentrate from 
caramel colorant previously treated with microorganisms, and dialysis of 
caramel colorant to obtain a colorant solids concentrate. A more recent 
example of a caramel colorant concentrating process is the use of 
ultrafiltration such as the process disclosed in U.S. Pat. No. 3,249,444 
to Bollenback et al. 
It was reported by Stinson and Willits, Journ. Assoc. Offic. Anal. Chem. 
46(2), pp. 329-330 (1963), that acid-proof caramel colorant could be 
separated from ash salts and sucrose by subjecting the caramel colorant to 
gel filtration using cross-linked dextran as the filter gel. According to 
the report, it was possible to separate acid-proof type caramel colorant 
from ash salts and sucrose in one pass through a large static column of 
Sephadex type filter gel. 
While the above-mentioned processes for the enhancement of caramel colorant 
have been generally satisfactory in terms of the product produced, the 
processes have not been entirely satisfactory for implementation in 
commercial operations of large capacity due to, among other things, the 
relatively long periods of time necessary to affect an enhancement of the 
caramel colorant. 
SUMMARY OF THE INVENTION 
It is, therefore, an object of the present invention to provide a process 
for the enhancement of caramel colorant which can be conducted in a 
relatively short period of time and which produces a caramel colorant of 
improved coloring power and a reduced content of undesirable or non-color 
contributing substances. 
Briefly, in its broader aspects, the present invention relates to a process 
for the rapid enhancement of caramel colorant which comprises passing a 
liquid containing caramel colorant through a size exclusion 
chromatographic material while subjecting the liquid to centrifugal 
forces. 
Further objects, advantages and features of the present invention will 
become more fully apparent by reference to the following, more detailed 
description of the present invention. 
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
As mentioned previously, caramel colorant comprises high molecular weight 
caramel colorant solids which impart the coloring capability to the 
product, and a wide variety of low molecular weight materials including 
ash, sugars, inorganic salts and the like which do not contribute to 
coloring power of the caramel colorant. For convenience, the high 
molecular weight substances will be referred to hereinafter as "colorant 
solids", and the lower molecular weight materials will be referred to 
hereinafter as "non-colorants". 
In accordance with the process of the present invention for the enhancement 
of caramel colorant, the colorant is caused to pass through a size 
exclusion chromatographic material (hereinafter referred to as an SEC 
material) while being subjected to centrifugal forces. Generally, the SEC 
material may be selected from a wide variety of substances which are 
capable of producing a separation between the high molecular weight 
caramel colorant solids and the lower molecular weight non-colorants of 
the caramel colorant. At least some SEC materials can be characterized as 
gel filtration media. Suitable SEC materials for the purposes of the 
present invention include kieselguhr, cellulose and dextran. A 
particularly suitable SEC material is cross-linked dextran such as that 
sold under the name Sephadex, especially Sephadex grade number G-25-C. 
Centrifugal forces may be applied to the caramel colorant solution passing 
through the SEC material in a variety of ways in accordance with the 
present invention. Centrifugal force may be defined as the force which 
impels matter outward from a center of rotation. A presently preferred 
manner to apply these forces is to utilize a basket-type centrifuge 
capable of retaining the SEC material, and then passing the caramel 
colorant solution through the material while the basket is rotating at a 
relatively high rate of speed. The magnitude of centrifugal force applied 
may vary considerably but amounts in the range of about 10 G to about 2000 
G, preferably about 100 to 1500 G, or even about 160 to 1000 G, have been 
found to be satisfactory. Generally, forces of less than about 10 G 
provide no significant increase in the rate of separation of the caramel 
solids while forces in excess of about 2000 G, although providing good 
yield give poor separation, and tend to be impractical economically in 
terms of the processing equipment required and power utilized while 
providing no significant advantage over applied forces of a smaller 
magnitude. 
The process of the present invention may be conducted using various caramel 
feeds of differing concentrations. The feeds contacted with the SEC 
material may, for example, contain about 10 to 50, preferably about 15 to 
40, weight % of colorant solids based on total solids. The total solids 
concentration, i.e., both colorant and non-colorant solids, of the feed 
may often be about 20 to 60 weight %, preferably about 25 to 50 weight %. 
The purified product often contains at least about 60 or 65 weight % color 
solids based on total solids, preferably at least about 75 or 80%. 
As a general rule, various types of caramel colorants from suitable 
carbohydrates are capable of being treated by the process of the present 
invention so as to improve the coloring properties of the colorant and to 
remove undesirable non-colorant materials such as inorganic salts. 
Examples of caramel colorants which may be treated by the method include 
cane-sugar caramel colorants, malt caramel colorants, and corn-sugar or 
dextrose caramel colorants. The process may be particularly adapted to the 
enhancement of "acid-proof" caramel colorants produced by the 
sulfite-ammonia process which are used primarily by the beverage industry. 
Other systems for producing the caramel colorant feed may employ only 
ammonia or sulfite. 
The efficiency of the present process for the enhancement of caramel 
colorant can be measured by a comparison of several properties of the 
enhanced colorant with the starting caramel colorant, e.g., by the yield 
of colorant (the total amount of colorant solids in the starting colorant 
which are passed through the size exclusion chromatographic material into 
the enhanced or enriched colorant), the percentage of colorant solids (the 
purity of the enriched colorant in terms of total solids in the colorant) 
and the decrease in potassium ion concentration from the starting caramel 
colorant to the enriched or enhanced colorant. The decreased potassium ion 
concentration is indicative of the removal of inorganic salts including, 
of course, potassium salts as well as sodium and other similar salts. 
While it is generally desirable to maximize colorant yield and percentage 
of colorant solids in the product while minimizing the potassium ion 
concentration when utilizing the present invention, in practice it has 
been found that all of these properties have not generally been maximized 
simultaneously by appropriate selection of the process variables, but 
rather the maximization of one property of the product may tend to reduce 
one or more of the other properties of the product from their maxima. For 
example, it has been found that the process variables of concentration of 
colorant solids in the starting caramel colorant, quantity of colorant 
treated with a given amount of SEC material, the magnitude of centrifugal 
force applied, and the use of one or more subsequent aqueous washes may 
have a significant effect on the characteristics of the colorant product. 
Generally, higher yields of caramel colorant are achieved when the initial 
colorant is of lower solids concentration, the applied centrifugal force 
is relatively high, and the use of a high volume of colorant per volume of 
SEC material. In contrast, a higher caramel colorant enrichment in terms 
of colorant solids concentration and a greater potassium ion removal are 
achieved in the final product when a lower volume of initial starting 
colorant is used, the applied centrifugal force is relatively low and the 
concentration of colorant solids in the initial colorant is relatively 
high. The use of a subsequent aqueous wash of the SEC material tends to 
increase the colorant yield but at the expense of the colorant solids 
concentration in the final product. 
While the above-mentioned process variables all affect the results of the 
process to at least some extent, it appears that the process variable 
which most strongly affects the colorant yield is the magnitude of the 
applied centrifugal force, and that the process variables which most 
significantly affect the final colorant concentration are the magnitude of 
the applied centrifugal force and the colorant solids concentration in the 
initial caramel colorant. 
As mentioned previously, it is a significant feature of the process of the 
present invention that the properties of caramel colorants can be enhanced 
to at least approximately the same levels as those produced by known 
caramel colorant enhancement processes but, by use of the present process, 
the enhancement can be obtained in a much shorter period of time. For 
example, it has been found that caramel colorant can be passed through a 
static column of cross-linked dextran to produce a colorant having a 
colorant solids concentration of between about 85 and 95% with a yield of 
colorant between about 75 and 80% depending upon the dilution of the 
initial colorant. However, in order to achieve these results, it is 
necessary to allow the column to drain for a relatively extended period of 
time. In contrast, by use process of the present invention, comparable 
results in terms of yield and colorant solids concentration can be 
achieved in far less time, generally on the order of about ten to fifteen 
minutes. 
The method of the present invention is further illustrated by the following 
examples and accompanying test data. In the examples, the effects of the 
varables of quantity of caramel colorant solution, the solids content of 
the caramel solution, the use of wash water, wash water temperature, and 
the magnitude of applied centrifugal force are illustrated. It should be 
understood that the examples are given for the purposes of illustration 
only and do not limit the invention as described herein.

EXAMPLE I 
An aqueous solution of caramel colorant is subjected to centrifugal size 
exclusion chromatography. The starting caramel colorant used is a 
commercial acid-proof caramel sold by D. D. Williamson, Inc. under the 
type designation 11 DS double strength caramel having a colorant solids 
concentration of about 48%. Prior to treatment, the commercial caramel 
colorant is diluted with water to produce an aqueous solution having a 
total solids concentration of about 28.5%. 
A conventional laboratory centrifuge is used in the centrifugal size 
exclusion chromatographic separation, the centrifuge being a Model UV 
centrifuge sold by the Damon-International Equipment Corporation and 
having a manganese-bronze perforated basket and a stainless steel draining 
chamber. The centrifuge is prepared for filtering the caramel colorant 
solution by lining the basket with a porous polyethylene sheet of 
sufficient dimensions to prevent stretch-opening due to subsequently 
applied centrifugal forces. 
The SEC material used is a cross-linked dextran sold under the tradename 
Sephadex G-25-C gel by Pharmacia, Inc. of Piscattaway, New Jersey, U.S.A. 
The material is prepared by swelling or hydrating about 660 g of the dry 
Sephadex with tap water to produce a gel having volume of about 3300 ml. 
The SEC material is allowed to swell for about six hours at room 
temperature. Thereafter, about 3000 ml of the swollen SEC material with 
excess water is stirred and immediately transferred to the centrifuge 
basket rotating at about 660 rpm. The rate of spin of the centrifuge is 
then rapidly accelerated to the process velocity to form the gel material 
into a vertical bed wall in the basket and to remove interstitial water 
between the gel beads. If necessary, the bed wall may be shaped to 
substantial vertical uniformity by the addition of water while the basket 
is rotating at a relatively low speed or by sluicing the bed down at low 
speed and rapidly accelerating the basket again. 
Once the bed wall of SEC material is formed, about 260.6 g of the 
above-mentioned caramel colorant solution is slowly added to the 
centrifuge basket rotating at a low speed of about 600 rmp. During the 
addition of the caramel colorant solution to the centrifuge basket, the 
solution is fed so as to evenly distribute the solution over the vertical 
wall of the rotating bed. The rate of rotation of the basket is increased 
to and maintained at about 1000 rpm (about 600 G's) until the flow of 
liquid from the basket ceases in about 10 to 15 minutes. The solution 
passing through the centrifuge basket is collected in a tared container 
and then measured so as to determine the yield of colorant solids, percent 
caramel color substance, colorant solids concentration and reduction in 
potassium concentration in the collected solution. The following results 
are realized: 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 50.6 85.3 77.4 
2 50.4 90.9 73.4 
3 74.8 74.6 78.6 
4 70.7 80.5 73.2 
______________________________________ 
In run 3, a wash of 250 ml of tap water of about 10.degree. C. is utilized 
to help facilitate the caramel colorant yield. 
Color yield is determined by diluting about 0.2 ml of the initial caramel 
colorant solution to about 108 ml with distilled water and then swirling 
to assure homogeneity. The absorbance of the diluted caramel solution is 
measured at about 610 nm on a visible absorption spectrophotometer. A 
sample of the collected caramel colorant solution is also subject to the 
same dilution and measurement. Percentage color yield is determined by 
dividing the absorbance of collected caramel solution by the absorbance of 
the initial caramel solution and then multiplying by one hundred. The 
percent of color substances in the total dissolved solids is determined by 
using high performance-size exclusion chromatography. 
Potassium ion concentrations of the initial caramel colorant solution and 
the collected solution are determined by mixing about 0.05 to 0.10 ml of 
the particular caramel colorant solution with about 1 ml of 10 M acetic 
acid, about 0.2 ml chloride solution (63.5% W/V), and diluting to about 
100 ml in a volumetric flask. Each of the resultant solutions is aspirated 
into the flame of an atomic absorption spectrometer calibrated with a 
potassium or sodium standard. The concentration (ppm) of potassium 
indicated on the spectrometer is multiplied by the dilution factor to 
yield the concentration in each of the undiluted caramel colorant 
solutions. 
The basic procedure of Example I is then repeated as is set forth 
hereinafter in Examples II-VIII. In these Examples, the effect of varying 
one or more of the process variables of (a) quantity of caramel colorant 
solution treated, (b) total solids concentration of the initial solution, 
and (c) the rate of rotation of the centrifuge are investigated. In 
Examples II-VIII, one or more of these variables is increased as shown in 
the following table where an "X" indicates that that particular variable 
was increased in magnitude over the value set forth in Example I. 
______________________________________ 
Variable 
Solids 
Example Quantity Concentration 
Spin Rate 
______________________________________ 
II X 
III X 
IV X 
V X X 
VI X X 
VII X X 
VIII X X X 
______________________________________ 
EXAMPLE II 
The procedure of Example I is repeated except that about 493.4 g of the 
caramel solution are utilized. The following results are obtained from the 
centrifugal size exclusion chromatography. 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 83.1 77.5 64.4 
2 66.2 82.6 54.4 
3 93.2 68.7 66.8 
4 80.8 74.2 53.2 
______________________________________ 
EXAMPLE III 
The procedure of Example I is repeated except that the percentage of solids 
in the caramel solution is 47.5 rather than 28.5 as in Example I. The 
following results are obtained from the centrifugal size exclusion 
chromatography of the caramel containing solution; 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 47.6 97.8 88.4 
2 45.0 91.3 68.2 
3 61.1 89.2 88.3 
4 68.2 76.6 59.7 
______________________________________ 
This example illustrates that a higher solids content produces a relatively 
high purity resultant solution but that the yield is relatively low. 
EXAMPLE IV 
The procedure of Example I is repeated except that the basket is rotated at 
about 2600 rpm (about 1000 G) rather than at about 1000 rpm. The following 
results are obtained from the centrifugal size exclusion chromatography of 
the caramel containing solution; 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 74.0 87.1 56.3 
2 70.2 88.2 49.6 
3 82.0 69.5 58.8 
4 80.1 69.6 55.4 
______________________________________ 
EXAMPLE V 
The procedure of Example II is repeated except that the caramel solution 
has a solids content of about 47.5%. The following results are obtained 
from the centrifugal size exclusion chromatography caramel containing 
solution; 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 51.5 85.3 57.9 
2 48.1 91.0 71.4 
3 64.3 76.8 55.7 
4 60.0 80.9 51.0 
______________________________________ 
EXAMPLE VI 
The procedure of Example III is repeated except that the basket of the 
centrifuge is rotated at about 2600 rpm. The following results are 
obtained from the centrifugal size exclusion chromatography of the caramel 
containing solution; 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 88.0 70.0 56.3 
2 83.0 70.8 53.4 
3 78.0 74.9 59.7 
4 81.1 71.5 50.6 
______________________________________ 
EXAMPLE VII 
The procedure of Example II is repeated except that the basket of the 
centrifuge is rotated at about 2600 rpm. The following results are 
obtained from the centrigual size exclusion chromatography of the caramel 
containing solution; 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 92.3 74.0 19.0 
2 88.6 74.2 18.2 
3 97.0 66.0 45.3 
4 92.8 65.1 25.3 
______________________________________ 
As is evident, the use of a relatively high solids concentration and a 
relatively high spin rate, while producing a high yield, did not reduce 
the potassium ion concentration to a great degree. 
EXAMPLE VIII 
The procedure of example V is repeated except that the basket of the 
centrifuge is rotated at about 2600 rpm. The following results are 
obtained from the centrifugal size exclusion chromatography of the caramel 
containing solution; 
______________________________________ 
Color Color Reduction of K+ 
Run Yield (%) Substance (%) 
Concentration (%) 
______________________________________ 
1 82.2 76.6 36.5 
2 86.1 69.2 52.9 
3 84.5 70.7 51.0 
4 75.3 76.7 51.2 
______________________________________ 
While the present invention has been described with reference to particular 
embodiments thereof, it will be understood that numerous modifications may 
be made without departing from the spirit and scope of the invention.