Pyrolysis of Caramel Colors

Chapter 11. Analytical Pyrolysis of Caramel Colors and of Maillard Browning Polymers 

Caramel colors are brown pigments produced by reaction of a saccharide with a browning accelerator. They can be considered a natural material as caramels may be formed in food. Caramels are prepared as food colors by heating a solution of a sugar (commonly glucose or sucrose) with the accelerator. The caramels can be classified as one of four types [1] shown in Table 11.1.1. 

The polymeric material from the plain caramel is generated from the condensation reactions of the aldehydes and ketones formed by heating the sugar with bases or acids. The ammonia caramel is formed in a Maillard type reaction [2] where carbonyl compounds react with amino groups or ammonia. This type of compound will be further presented in Sections 11.2 and 11.3. Sulfite caramel is also a Maillard type polymer. However, as hydrogen sulfites form stable adducts with aldehydes and ketones, the sulfite caramels include in their structure sulfite groups. 

Because the information on the caramel composition is of practical importance, several procedures have been proposed for their analysis. One such analytical procedure is Py-GC/MS, which has been used for a rapid classification of caramels. The differentiation can be done based on the nature of the compounds generated by pyrolysis. Using GC/MS analysis [1,3] of the pyrolysates, the nature of the caramel can be obtained from the peak intensities, which vary as shown in Table 11.1.2. 

As seen in Table 11.1.2, the caramels of type 1 form mainly furans and cyclopentenones and do not show nitrogen containing compounds. Caramels of type 3 (ammoniated caramels) contain a variety of pyrazines and no hydroxymethylfurfural, while the type 4 caramels contain both pyrazines and furans. Pyrolysis of caramel colors of type 4 also generates a certain amount of SO2. 

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