Polymerization caramel

During caramelization several flavor components as well as polymeric caramels are pro-dnced. Caramels are a complex mixture of various high molecular weight components. They can... 

Monosaccharides are probably involved in the browning reactions that occur during the roasting of coffee. Caramelization involving the sugars alone, and Maillard reactions, between sugars and free amino acids, produce polymeric yellow to dark brown substances, known as melanoidins. These melanoidins can be extracted into hot water, separated and characterized.105... 

With alkaline degradation, the formation of 1,2-enols is also the initial step. This reaction in turn can produce three-carbon compounds which yield a series of intramolecular reactions involving condensation and polymerization. Both acidic and alkaline caramelization produce numerous volatile and nonvolatile compounds that significantly contribute to aroma, taste, and color. 

FINAL Red-brown Dark brown Aldol condens. Polymerization Strecker degrad. COj evolution Sulfites do not decolorize Acidic fluorescence Reducing pvr. in acids Caramel, roasted aromas Colloids, melanins form... 

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. 

At 230°, the degree of polymerization of caramel becomes still higher. Hydrocarbons were suggested as being the final products of carameUzation at elevated temperatures, but this suggestion has not been documented experimentally. Simultaneously, the same result could be achieved at constant temperature as the reaction time is extended. 

For the melanoidins and caramels, given that these are complex polymeric molecules and their stracture has only been elneidated in a few cases (Amoldi et al., 1997), it is difficult to show possible resonanee stmctures. An examination of the proposed pathways for non-enzymatie browning give intermediates in which resonance straetures are important. This includes keto-enol trans-... 

Even if the water is rapidly removed by vacuum, at this stage the reactions will inevitably tend to follow the course of those occurring in very concentrated solution. The sugar anhydrides readily form dimers, levulosan in particular being converted into diheterolevulosans. It is now known that similar products are formed by refluxing fructose in 80% solution (24). The reactions of caramelization cannot be limited to the initial stages without simultaneous further dehydration and polymerization, as well as extensive degradation to produce hydroxymethylfurfural (13). 

Caramelization of sucrose requires a temperature of about 200°C. Reactions involved in the caramelization of sucrose include mutarotation, enolization and isomerization, dehydration and fragmentation, anhydride formation, and polymerization. The extent to which the reaction occurs depends upon pH, temperature, and heating time. Sucrose, held at 160°C as a melt, will hydrolyze to glucose and fructose anhydride. The production of water and organic acids such as acetic, formic, and pyruvic during sucrose caramelization will enhance the hydrolysis. Hydrolytic products, glucose and fructose, are reactants in the formation of caramel and volatile flavor compounds... 

Sucrose is unstable at temperatures albO C (320T) and thermolyzes to the brown candy that we appreciate as caramel. Caramel contains a myriad of decomposition products formed by simultaneous cleavage of sucrose to glucose and fructose, dehydrations, fragmentations (such as retroaldol additions), isomerizations through enols (apply the last three reactions to glucose and see what you get), and polymerizations. Two of the odorants that have been identified in the mixture are shown below. 

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