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Chapter 5

FOOD 2010 Chapter Notes - Chapter 5: Maillard Reaction, Starch Gelatinization, Glycosylamine


Department
Food Science
Course Code
FOOD 2010
Professor
Massimo Marcone
Chapter
5

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Chapter 5: Food Chemistry 2, Carbohydrates, Lipids, Proteins
5.1 Food Carbohydrates
-structure of sugars
-all contain CHO
-simple sugars (fructose, glucose, galactose are monosaccharides) and
(lactose, sucrose, maltose are disaccharides) also termed organic alcohols.
-monosaccharides
-3 carbons are triose
-5 carbons are pentose
-6 carbons are hexose
-disaccharides
-monosaccharides are the building blocks
-2 monosaccharides form one disaccharides
-sucrose (fructose, glucose)
-lactose (galactose, glucose)
-maltose (glucose, glucose)
-functional properties of sugar
-reducing sugars (sugars that contain aldehyde or ketone carbonyl group.
They react through oxidation-reduction to produce reduced substance plus
the oxidized sugar molecule. All monosaccharides and most disaccharides
are reducing sugars. Dextrose equivalent [DE] measure of % of glycosidic
bonds hydrolyzed in simple sugars, indicating the level of reducing sugar
present. Higher the DE = more soluble and greater reducing ability.)
-browning (Maillard browning and caramelization. Maillard browning is
nonenzymatic [simple sugars but sucrose] browning reaction between a
simple sugar and amino acid to form melanoidins. Happens in 3 steps. 1:
condensation of reducing sugar and amino acid gives glycosylamine. 2:
rearrangement glycosylamine becomes amadori compounds [colourless] and
then pyrazines. 3: polymerization, the colourless intermediate compounds
from the brown melanoidin pigments. There is also carmelization, which is
the formation of brown caramel pigments as a result of applying heat energy
to sugars. Need at least of a temperature of 200oC. There is no single
compound identified as caramel, it depends on the substance what is called
caramel.)
-crystallization (sugars can exist in soluble [as syrup] and crystalline states.
Formation of a crystalline structure implies organized 3D arrays of unit cells
into a solid form. A crystal is a solid made up of units in a repeating pattern.
When the sugar is purified crystallization is the key step. Happens in 2 stages.
The first one is transfer of sugar molecule to surface of a crystal and the
second is the incorporation of sugar into the crystalline structure.
Crystallization in hard candies is desirable, however in ice cream it would
make it more gritty.)

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Chapter 5: Food Chemistry 2, Carbohydrates, Lipids, Proteins
-humectancy (humectant = affinity for moisture. They hydrogen bond with
water molecules, making less water available for microbial growth.)
-inversion (hydrolysis of sucrose to its monosaccharides is carried out if a
sweeter product is desired than sucrose alone. The mixture of two
monosaccharides endproducts, called inverted sugar, is typically created in
food products through the deliberate application of the enzyme invertase)
-oxidation and reduction (oxidation causes a less sweet sugar. Reduction of
a disaccharide forms a sugar alcohol, which is a alternative sweetener.
Glucose + Hydrogen = sorbitol. Fructose + Hydrogen = mannitol. Maltose +
Hydrogen = maltitol.)
-sweetness and texturizing (Fructose>Sucrose>Lactose. in order from most
sweet to least sweet. Competition for water by sugar and other substances,
can change texture. Starch gelatinization is delayed due to sugars. The effect is
to reduce the viscosity and gel strength of starch thickened mixtures like
pudding. Sugars also act as tenderizers in cakes and baked products.)
-Polysaccharides and their funcitonal properties
-complex carbs
-10 or fewer sugar units are called oligosaccharides
-beta-glucans similar to cellulose but less linear. (oatrim [a by-prodcut] can
be used as a fat replacer and texturizing ingredient)
-cellulose (indigestible for humans. A non-caloric microparticulate form of
cellulose available in food industry, when dispersed, forms a network of
particles with mouthfeel and flow properties similar to fat. So it can be a fat
replacer.)
-dextrins and maltodextrins (dextrins are polysaccharides derived from
starch, linear arrays of glucose units. Produced commercially by hydrolyzing
amylose portion of starch. Heat is used to carry out the reaction. Can be used
as fat replacers. Dextrans have a alpha 1-6 linkage compared to alpha 1-4
linkage in dextrins. Dextrans are food gums. Maltodextrins are polysaccharide
fragments derived from starch hydrolysis. They can be used as a fat replacer,
texture modifier or bulking agent.)
-Fructoogligosaccharides ([FOS] are naturally occurring sugars consisting
of multiple units of sucrose joined one, two or three fructose molecules via
glycosidic bond to the fructose portion of the sugar molecule. Also known as
prebiotics, they promote growth of bacterial organisms believed to be
beneficial in health.)
-Inulin: Dietary Fibre (its a FOS that acts as a dietary fibre, occuring
naturally in some plants. Composed of a chain of fructose units with a terminal
glucose unit. Not digestible, and it can provide a creamy mouthfeel through texture
modification, as well as be a fat and sugar replacer, and it can be a bulking agent.
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