carbs Flashcards
monosaccharide
Monosaccharides are the fundamental units because they are not hydrolyzed by acid to form a smaller unit.
disaccharide
consist of two simple sugarslinked by a covalent
glycosidic bond
oligosaccharide
consist of 3 to 10 monosaccharides linked together by glycosidic bonds
what is the functionality of monosaccharides
Coloring agents (caramel color) Production of flavors (caramelization)
what is the functionality of a polysach.
Thickening agents Gelling agents Emulsion stabilizers Water holding/ binding agents Anticaking agents Edible films Encapsulate flavors
complete
Their actual conformation is … in their crystalline state and
predominantly cyclic in solution
cyclic
Cyclization is due to the formation of internal … and
…
hemiacetals and hemiketals
hemeacetal formation in glucose forms a
pyranose ring
hemiketal formation in fructose form a
furanose ring
mutaotation
is the result of the cyclic form opening up and recyclizing, coming to equilibrium with its anomer.
which is the most comon test for reducing sugars
fehling’s test
The disaccharide maltose a reducing sugar while the
disaccharide sucrose is a non-reducing sugar - why?
Because even when 2 molecules of maltose are bind together they can open up however fructose cannot do this and so it is not a reducing sugar
which are the 2 ways that water can be elimiated from sugar
- by reaction of tehir hydroxyl groups
2. elimination of water grom within a sugar molecule, leading to the formation of higly unstaurated ring structure
A common intermediate formed during caramelization reactions by
dehydration is
hydroxymethylfurfural (HMF)
what are the 2 categories of browning reactions
(1) oxidative browning
(2) non-oxidative browning
caramelization reaction used to producde
flavor, color
carame flavor and color are made of
flavors - sucrose
color- glucose
what is an amadori rearrangement
schiff base to amadori compound
at higher temperature in the maillard reacion , the major reactions will be
dehydration and fragmentation
strecker degration
subcomponent of maillard reaction. Involves free amino acids produced by meaillard reacion or caramelization
which is the most sweet of the sugars and the less
most- fructose
less- lactose
true or false
The least sweet the less soluble
true
which sugar is an exception int he sence of sweetnes of the sugar alcohols
xylitol
the properties of polysaccharide are a fucntion of
their sugar/chemical makeup
• the presence of unique functional groups
• their molecular weight and degree of branching
• a combination thereo
wha are the unique porperties of starch
thickening, texture
starch is made up of
D glucose which are divided in amylose (alpha 1-4 linkages) and amylopectin (alpha 1-6)
explain starch granules
granyles are characterisic of the starch source. The starch is isolated and it is white. It contains granules that are made of amylose and amylopectin
what happens in gelatinization
starch and water are heated and it causes teh granules to swell. The viscocity increases
what are the variables that occur in the starch
concentration of starch
• The amylose:amylopectin ratio of the starch
• The average molecular weight (chain length) of the starch
• The rate of cooling
• The presence of other components in solution
true or false
Amylopectin is a highly branched water-dispersible
macromolecule
true
retrogration
continued Hbonds formation between starch molecules
what are the 2 problems with retrogration
- texture changes
2. syneresis may occur = the gel tightens up that it starts to exude water
factors affecting behaviours of starches in complex food system
pH, ionic strengh, proteins,
pre gelatinized strach
Starches granules are heated below the gelatinization temperature of the starch, causing them to swell
Causes some disorganization of the starch granule- making it dispersible in cold water and requires less heat or time to develop viscosity
acid modified starches
Produced by holding starch just below its gelatinization temperature in an acidic medium
Acid is used to partially and randomly hydrolyze the glycosidic linkage in the starch granule without breaking up the INTEGRITY of the granule per se.
cross linked starches explain
Maximum viscosity is normally reached when the granules are swollen
extensively but still intact - however, swollen granules normally break
down with subsequent shear.
Can hold starch granules together by cross-linking starch chemically so
that the swollen granule retains its integrity
what are the 2 types of starch conversion
dry pyroconversion and acid hydrolysis
what is pyroconversion
Starch granules are sprayed with dilute HCl and subjected to relatively high temperatures
what are the 3 products that are produced by pyroconversion
white dextrins, yellow dextrins, british gums
white dextrins
can be Under conditions of high moisture, high acid, and relatively low
temperature, hydrolysis predominates.
yellow dextrins
Lower moisture, moderate acid, higher temperature. Color due to caramelizatio
british gums
Little or no acid used - high temp. Dark color. Viscous and capable of forming a stiff gel
what are the 4 available enzymes to broke starch
alpha amylase
beta amylase
glycoamylase
pullulanase
what does alpha amylase does
attack the starch everywhere except the alpha 1- 6 branch. produce oligosaccharide
what does beta amylase does
attacks the non reducing end of the starch. Produces maltose! Also develop sweetness rapidly
what does the glucoamylase does
remove single glucose units form the non reducing end of starch and to split maltose into 2 glucose units
what pullulanase does
Take care of the branch
High-fructose corn syrups are similar to … and are in direct competition with sucrose, which is commonly inverted
(e.g., using the enzyme invertase) to stabilize its sweetness in
acidic environments )
invert syrups
Cellulose is often accompanied by other carbohydrates
(hemicelluloses and pectic substances) and … to form the
structural components of most plant tissues
lignin
