Chemistry of Milk

Lesson 22. CARAMELIZATION AND ITS SIGNIFICANCE

Module 5. Carbohydrates in milk

Lesson 22

CARAMELIZATION AND ITS SIGNIFICANCE

22.1 Introduction

Caramelization is a type of non-amino browning reaction. This process consists of heating sugar slowly to around 170°C.As the carbohydrates are heated, the molecules break down and reform into compounds with a characteristic brown colour and flavour. It is a chemical decomposition of non-protein substances that occurs spontaneously at high temperatures and the reaction is known as pyrolysis. Caramelization is a complex, poorly understood process that produces hundreds of chemical products. Caramelization by heat during baking contributes to flavour and colour. However, it occurs to limited extent in milk and milk products and hence has limited significance.

22.2 Definition

Caramelization is the removal of water from a sugar, by heating. This process results in is omerization and polymerization of the sugars into various high molecular weight compounds. Compounds such as difructose anhydride may be created from the monosaccharides after water loss. The fragmentation reaction of sugars during heating would result in low molecular weight compounds that may be volatile and may contribute to flavour. Polymerization reactions lead to large molecular weight compounds that contribute to the dark brown colour.

Caramelization type of browning may be defined as the heat decomposition of sugars as a function of pH and buffers in the absence of amino compounds. It requires high order of activational energy.

Caramelization is the oxidation of sugar by heating resulting in the production of nutty flavour and changing to brown colour. During the process, volatile chemicals are released, producing the characteristic caramel flavour.

The types of reactions that occur during the process of caramelization are

• Sucrose inversion to fructose and glucose
• Condensation reactions
• Intramolecular bonding
• Isomerization of aldoses to ketoses
• Dehydration reactions
• Fragmentation reactions
• Unsaturated polymer formation.

22.3 Pyrolysis

Pyrolysis is the chemical decomposition of condensed substances that occurs spontaneously at high temperatures.

22.4 Caramel

Caramel colouring is a dark, rather bitter-tasting liquid. It is the highly concentrated product of near total caramelization, which can be used as food colouring and apart from its addition in beverages such as cola.

22.4.1 Components of caramel

Three main components of caramel called caramelan, and caramelin were isolated by using dialysis. Caramelan was described as a brown brittle, deliquescent solid having a bitter taste.

• Caramelan melts between 136°C to 144°C and it is readily water soluble.
• Caramelen is a brown substance much darker than caramelan and not deliquescent it melts at 153.5°C-154°C.

Caramelin exists in three modifications’ namely, soluble in cold water, soluble only in boiling water and insoluble in all ordinary solvents. They are infusible materials that are much darker than caramelan and carmelen. Three high molecular weight components have been separated from caramel prepared from sucrose. They are melanoidin found in ammonia processed caramels seem to be the sole polymeric compound in caramel. The pH values of caramel constitute an important property of caramels. A high pH may indicate an incomplete burn or alkali present. Above pH 6.0 caramel is susceptible to the attack by molds and below pH 2.5 it quite readily resinifies.

A good caramel should contain colloidal particles which do not precipitate during storage or to the products to which caramel is added. Though the control of viscosity of caramel is difficult manipulation of the temperature on the period of its contact with reagent, it is possible to obtain caramel of desired viscosity. The rate of dehydration is one of the most important parameter to influence the properties of caramel in general. The time of mutual contact of reagents and manipulation of the temperature may lead to caramel of desired viscosity.