Carbohydrate when heated results to a complex group of reactions in absence of nitrogen containing compounds. Such reaction is commonly known as caramelization. Sugars will show caramelization to a relatively high temperature. The browning of these carbohydrates is further facilitated by the presence of small amount of acid, salts of this acids, phosphates and metallic ions. Lack of moisture in the sugar molecule with formation of anhydro rings are actually caused by thermolysis. When double bonds are produced this leads to the development of unsaturated rings such as furans. The conjugated double bonds will then absorb light producing the brown color. Specific types of caramel colors, solubility and acidities are directed by some catalysts to increase the reaction. Mostly some of the unsaturated rings condense into polymers yielding the different colors.
One of the commonly used sugars during caramelization is sucrose solution. The brown caramel color produced in its reaction with ammonium bisulfate is used in cola soft drinks, syrups, candies, pet foods and dry seasonings. Solutions of it are acidic with pH ranges from 2-4.5 and with colloidal particles having negative charges. The non-enzymatic browning caramel pigments are large polymeric molecules with complex, uneven, and indefinite structures. It is these polymers that form the colloidal particles. Their rate of formation increases with increasing temperature and pH. (Fennema, 1996) The diagram below shows a summary of the caramelization process in the experiment “effects of heating to properties of sugar”.(deMan, 1999)
There are three general types of browning, a.) Reaction of ketones and aldehydes among the reducing sugars with amino compounds like amino acids, peptides and proteins. This reaction is not dependent on the presence of oxygen b.) Caramelization which takes place in polyhydroxy carbonyl compounds such as reducing sugars when heated at high temperatures c.) The oxidative change of polyphenols to d- or polycarbonyl compounds and the oxidation of ascorbic acid which can be partially fully enzymatic (Meyer, 1960)
In order to determine the effect of heating on the characteristics of sugar, an experiment was performed and the observations were noted as shown in table 2.4 below.
Results showed that particular temperature have a corresponding stage of heating. At temperature 110-113°C, a transparent yellow color was observed. It formed threads at the bottom of the Petri dish and then become dispersed upon pouring on the beaker. This can be used in making syrups and some icing. The next stage was soft ball wherein the sample was observed to be flat and dispersed at the bottom of the Petri dish and formed ball when poured at the beaker. This light yellow stage in sugar heating can be used in making fondants, fudge, meringue and some butter creams. The third stage was flat and maintains it shape at the petri dish, upon pouring at the beaker, it formed ball yet it is still dispersed.
Such stage can be used to make caramel candies. For the fourth stage, the hard ball which is yellow was observed to have the same properties with the previous stage. This can be used in making marshmallows, gummies and hard candies. The fifth stage produced hard ball and maintained its shape when poured on the beaker and Petri dish. At this stage, butterscotch and taffies can be made. At the sixth stage, an orange color was observed; there was formation of ball where its shape was maintained. Lollipops can be made at this stage. Lastly was brownish black with defined shape and hard tail, it is also consistently hard. This stage can be used in making light caramels for syrups, spun sugars and coloring agents.
The capability of forming crystals is known property of sugars. Crystallization is an important step in the purification of sugar. If the sugar is pure the easier it is to be crystallized. However those sugars found to have anomers and ring isomers in solution make them intrinsically impure and difficult to crystallize. In some foods like sweetened condensed milk and ice cream, crystallization is undesirable. (deMan,1999)
In candy-making, controlling the rate and extent of sugar crystallization provides a huge range of textures. These range from the soft textures of fudges where crystallization is minimized, to hard candies where crystallization results in a desired grainy structure.( http://www.sugar.ca/english/healthprofessionals/functional.cfm#a)
Belitz H.D Grosch W. Schieberle P.2009.Food Chemistry. 4th revised and extended ed. Derman, J.M. 1999. Priciples of Food Chemistry. 3rd Edition.USA.Aspen Publishers, Inc. Fennema Owen R.. 1996.Food Chemistry3rd Edition. Marcel Dekker, Inc.