Sucrose caramelization

Caramel and caramelized sugars have also been investigated. Caramelized sucrose, glucose, mannose, arabinose, maltose and fructose induce high frequencies of chromosome aberrations (63),... 

Caramel Sucrose or lactose Smooth and short texture... 

The anhydrodisaccharides a-D-fructofuranose-P-D-fructopyranose 1,2 2,1 -dianhydride and a-D-fructofiiranose-P-D-fructofiiranose l,2 2,r-dianhydride have been identified in the ethanol-soluble products from the thermolysis of sucrose. These same products, along with di-P-D-fructofuranose-l,2 2,r-dianhydride, were found in caramelized sucrose. Dissolution of sucrose in anhydrous HF afforded a complex mixture of difructose dianhydrides and their glucosylated derivatives as well as oligosaccharides up to dp 14. a-D-Fructofuranose-P-D-fiructopyranose l,2 2,r-dianhydride was the main component in the mixture, either free or glucosylated at various positions. The reaction of some disacdiarides with anhydrous HF has afibrded some dimeric dianhydrides. Palatinose, leucrose and maltulose gave, respectively, the dianhydrides 25, 26 and 27. a-D-Fructofuranose-P-D-fmctofuranose-l,2 2,r-dianhydride has been converted into the bis-3,6-anhydro-derivative, which,... 

Action of sodium hydroxide. Boil about 0 2 g. of glucose with 5 of 10% NaOH solution the mixture turns yellow, then brown, and emits the odour of caramel. Fructose, maltose, lactose and soluble starch behave similarly sucrose and ordinary starch do not give colorations. 

Caramel. Officially, the color additive caramel is the dark brown Hquid or soHd material resulting from the carefully controlled heat treatment of the following food-grade carbohydrates dextrose, invert sugar, lactose, malt symp, molasses, starch hydrolysates and fractions thereof, or sucrose. Practically speaking, caramel is burned sugar. 

The literature in this field is confusing because of a somewhat haphazard method of nomenclature that has arisen historically. This is compounded by some mistakes in structure determination, reported in early papers, and which are occasionally quoted. The first part of this chapter deals with nomenclature and with a brief overview of early work. Subsequent sections deal with the formation and metabolism of di-D-fructose dianhydrides by micro-organisms, and the formation of dihexulose dianhydrides by protonic and thermal activation. In relation to the latter topic, recent conclusions regarding the nature of sucrose caramels are covered. Other sections deal with the effects of di-D-fructose dianhydrides upon the industrial production of sucrose and fructose, and the possible ways in which these compounds might be exploited. An overview of the topic of conformational energies and implications for product distributions is also presented. 

The treatment of sucrose with anhydrous HF89 results in the formation of a complex mixture of pseudooligo- and poly-saccharides up to dp 14, which were detected by fast-atom-bombardment mass spectrometry (FABMS). Some of the smaller products were isolated and identified by comparison with the known compounds prepared86 88 a-D-Fru/-1,2 2,1 -p-D-Fru/j (1), either free or variously glucosylated, was a major product, and this is in accord with the known stability of the compound. The mechanism of formation of the products in the case of sucrose involves preliminary condensation of two fructose residues. The resultant dianhydride is then glucosylated by glucopyranosyl cation.89 The characterization of this type of compound was an important step because it has permitted an increased understanding of the chemical nature of caramels. 

Thermal activation of sucrose and inulin in the presence of citric acid,93 and sucrose in the presence of acetic94 acid, yields caramels containing, among other products, di-D-fructose dianhydrides and glycosylated difructose dianhydrides, as described in Section V.6). Similarly, the thermal treatment of 6-0-ot-D-glu-copyranosyl-D-fructofuranose (palatinose) in the presence of citric acid87 has been shown to produce appreciable proportions of glucosylated di-D-fructose dianhydrides. 

Sucrose caramels have been produced under anhydrous thermal conditions that are designed to maximize the content of fructose-rich oligosaccharides.100-102 These sucrose thermal oligosaccharide caramels (STOC) have been tested in animals as a nutritional supplement. Improved weight gains and feed conversion, and increased levels of bifidobacteria (see section VIII) were observed in broiler chickens that were fed this supplement.103... 

Similar anomalous distributions are observed in other thermal product mixtures. A commercial soft caramel made by heating sucrose and 0.1% acetic acid to 160°C contained 18% of a mixture of di-D-fructose dianhydrides.94 fi-D-Fru/-1,2 2,1 - 3-D-Fru/(now assigned as a-D-Fru/-l,2 2,l -a-D-Fru/83), ot-D-Fru/-1,2 2,1 -p-D-Fru/(5), ot-D-Frup-1,2 2,l -0-D-Fnjp (4), ot-D-Fru/-l,2 2,1 - 3-D-Frup (1), and p-D-Fru/-l,2 2,3 - 3-D-Fru/ (2) were found in the ratio 4 12 1 6 2. The first three of these, constituting 68% of the mixture, are considered to be kinetic products. The authors commented on this, but did not offer any explanation. Notice, however, that the preparation of such commercial caramels commences with heating of an acidic aqueous solution of sucrose, which almost certainly results in hydrolysis. Hence, the final dianhydrides are probably derived from the reaction of fructose, rather than sucrose. 

The non-precipitable (that is, lower molecular weight) component of a product from thermolysis (170°C, 80 min.) of anhydrous amorphous sucrose acidified with 1% citric acid contains 19% disaccharides, predominantly di-D-fructose dianhydrides.93 Only two of these were identified, namely a-D-Fru/-1,2 2,1 - 3-D-Fru/ (5) and ct-D-Fru/-l,2 2,1 - 3-D-Frup (1) in the ratio 1 1. This result can be compared with the ratio 2 1 for the commercial caramel.94... 

The oldest way to produce caramel is by heating sucrose in an open pan, a process named caramelization. Food applications require improvement in caramel properties such as tinctorial power, stability, and compatibility with food. Caramels are produced in industry by controlled heating of a rich carbohydrate source in the presence of certain reactants. Carbohydrate sources must be rich in glucose because caramelization occurs only through the monosaccharide. Several carbohydrate sources can be used glucose, sucrose, com, wheat, and tapioca hydrolysates. The carbohydrate is added to a reaction vessel at 50°C and then heated to temperatures higher than 100°C. Different reactants such as acids, alkalis, salts, ammonium salts, and sulfites can be added, depending on the type of caramel to be obtained (Table 5.2.2). 

Other compounds identified in caramels are di-D-fructose and poly(glycosyl) dianhydrides (DFAs). DFAs were found in caramels prepared from D-fructose, D-glucose, and sucrose. The analysis was done after derivatization as TMS (per-0-trimethylsilyl) derivatives or as TMS-oxime (per-O-trimethylsilyl oxime) by... 

GC/MS. A large number of DFAs were identified but their compositions and amounts depend on the nature of sugar used for caramelization. Fructose caramel contains the highest amount of DFAs (more than 39% of dry matter), while glucose caramel contains mainly glucobioses. In sucrose caramel, both types of compounds were found in similar proportions. Based on these observations, DAFs are considered suitable tracers for the determination of caramel authenticity. ... 

Fourteen DFAs and some oligomers were identified in caramel obtained by thermal treatment of inufin. - Monosaccharides (glucose, fructose), dehydration products (1,6-anhydro-p-D-glucopyranose, 1,6-anhydro-p-D-glucofuranose), disaccharides (gentiobiose and isomaltose), and oligosaccharides were also found in glucose and sucrose caramel. ... 

Defaye, K. and Garcia Fernandez, J.M., Protonic and thermal activation of sucrose an the oligosaccaride composition of caramel. Carbohydrate Res., 256, Cl, 1994. Ratsimba, V. et al.. Qualitative and qnantitative evaluation of mono- and disaccharides in D-fructose, D-glucose and sucrose caramels by gas-liquid chromatography-mass spectrometry di-D-fructose dianhydrides as tracers of caramel authenticity, J. Chro-matogr. A, 844, 283, 1999. 

Among the important processes taking place when sucrose is heated is cara-melization. Caramel is actually a very complex mixture. Some constituents are volatile, such as furan derivatives, pyrones, aldehydes, and low molecular weight carboxylic acids, and these account for 10% of the mass.340 The main constituents of the nonvolatile component have also been identified these include... 

Depending on the process (acid- or base-catalyzed, leading to aromatic or color caramel) and on the particular sugar substrate (sucrose, fructose), different proportions and types of these molecules can be found.291 Some of the caramel components are similar to those observed when fructose and sucrose react in hydrogen fluoride, notably bisglycosylated difructose dianhydrides.287 341... 

J. Defaye and J. M. Garcia-Fernandez, Protonic and thermal activation of sucrose and the oligosaccharide composition of caramel, Carbohydr. Res., 256 (1994) C1-C4. 

Perhaps one of the most fascinating and complex chemical reactions involving carbohydrates is caramelization. For example, granulated sugar heated at a high temperature in the dry state eventually produces a dark, viscous mass which has a strong and characteristic flavor totally different from the sweet taste of sucrose. 

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