Glucose caramelization

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. ... 

Sugisawa H. (1966) The thermal defradation of sugars. II The volatile decomposition products of glucose caramel. J. Food Sci. 31, 381-5. 

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. 

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... 

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. 

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

With regard to a glucose-proline system, Roberts and Acree277 have examined the sensory aspects in much more detail by applying Charm analysis (see the Olfactory Threshold section above). Four compounds provided most of the aroma 2-acetyl-3,4,5,6-tetrahydro-l//-pyridine (burnt, caramel 63%), 2-acetyl-1-pyrroline (popcorn 19%), 2-acetyl-l,4,5,6-tetrahydro-l//-pyridine (burnt, caramel 12%), and UDMF (cotton candy 4%). All Maillard systems of interest need to be submitted to similarly detailed analyses. 

Caramel in this context means a brown colour that is produced either traditionally by heating sugar or as a very intense product that is made by heating carbohydrate, usually glucose syrup, with ammonia. Caramel colour is the product of the Maillard reaction, i.e. the reaction of a reducing sugar with an amino group. Chemically the colour is a melanoidin - these substances are extremely stable and can be used in any type of confectionery. 

Liquorice is a slightly unusual example of a starch gel instead of separating the starch, wheat flour is used directly. It is also a product where brown sugars and treacle are used. Liquorice paste is typically made from treacle, wheat flour, liquorice extract and caramel. Caramel in this context means the brown colour produced from sugar and not a form of toffee. Industrial caramel is made by the action of ammonium hydroxide on a carbohydrate, typically glucose syrup. The resulting product is not well defined chemically, and for this reason its use is recommended to be limited to 0.2% maximum. 

Various Isopentyl-substituted pyrazines, such as 2-lsopentyl-3-methylpyrazine, 2-isopentyl-5-methylpyrazine, 2-isopentyl-6— methylpyrazlne, 2-i8opentyl-5,6-disiethylpyrazlne, 2-isopentyl-3,5-dimethylpyrazlne and 2-isopentyl-3,6-dimethylpyrazlne were identified from the thermal reaction of glucose and leucine (12). The formation mechanisms for these compounds may also involve the reaction of 3,6-dihydropyrazine with isovaleraldehyde, the Strecker aldehyde of leucine. Kltamura and Shibamoto (13) described 2-lsopen-tyl-5,6-dimethylpyrazlne as having a caramel-like, coffee and sweet aroma. Although isopentyl-substituted pyrazines have not yet been reported in cocoa, they could, if present, be very Important contributors to that characteristic aroma. 

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