Thermal degradation of carbohydrates

1. Presented by
Dr. A.Surendra Babu, Ph.D., PDF
Assistant Professor,
Dept. of Food Science and Technology,
SOAS, MRUH
Food Chemistry

2. Thermal degradation of sugars
• It may occur by two different major reaction pathways:
• Maillard reaction, which takes place in the presence of amino acids.
• Caramelization, that occurs when simple sugars are heated at high
temperatures.
• Caramelization is the common name for a group of reactions that occur
when carbohydrates are exposed to high temperatures with no amino
groups involved.
• Caramelization commonly occurs when sugars are heated, dry or in
concentrated solution, either alone or with certain additives

3. Maillard reaction
• The Maillard reaction, named after L. C. Maillard, is also known as non-
enzymatic browning.
• It is an extremely complex process and is the reaction between reducing
sugars and proteins by the impact of heat.
• The Maillard reaction starts with a reducing sugar reacting with an
amine, creating glycosyl amine.
• These substances undergo a reaction called Amadori rearrangement to
produce a derivate of amino deoxy fructose.

5. proceeds rapidly from around 140 to 165 °C

6. Caramelization
• Caramelization is a complex group of reactions that take place when
sugars, either dry or in concentrated aqueous solutions, are subjected to
high temperatures to form unique brown colors and flavors
• Caramelization is a poorly understood series of pyrolysis reactions.
• Most sugars can caramelize and the temperature necessary for
caramelization varies with the type of sugars.
• Fructose, for example, requires an initial temperature of 150oC while
maltose caramelizes at 180oC.

7. • The mechanism of caramelization development involves many steps -
carbohydrates (reducing mono- and di-saccharides) - dehydration
and degradation, condensation or polymerization to form complex
molecules of varying molecular weights.
Caramelization of sucrose, for example, can be divided into the
following stages:

11. • Process includes fragmentation, polymerization and subsequent formation of
volatile flavor compounds such as furan, maltol, ethyl acetate, diacetyl, etc.
as well as brown colored compounds such as caramelan, caramelen and
caramelin.
Application
• Caramelization can occur in many systems baked products.
• Caramel can be used as a filling, topping, or as a glaze.
• Flan and custard cake varieties commonly have a thin glaze of caramel
drizzled topically.
• Hardened caramel can also be used in decorating applications because of the
molding properties before complete hardening.