week12C1 : starch modifications Flashcards
what is the inconvenient with pre-gelatinized starch
you need more starch for the same viscosity.
how is pre-gelatinized starch made ?
heated below the gelatinization temperature to cause swelling then dried this causes disorganisation of the granule. Reduces the heat necessary to develop viscosity. Less viscous than real starch.
how is produced thin-boiling starches
boiling the starch under gel temp in acid neutralization drying.
what is the purpose of thin boiling starch
producing low viscosity fluids (candy industry).
what is the method used to produce granules resistant to shear?
the cross-linking method
what are the agent used for the cross-linking of starches
acetic, citric or adipic anhydrides are used
T or F : cross-linked starches are less suseptible to acid
true
what is the goal of modifying starches byh adding charges
to reduce the polymer polymer hydrogen bonding.
____ produces cold-water soluble starch.
dry pyroconversion
what are the reagents used in the formation of oxidized starches
- sodium hypochlorite
2. hydrogen peroxide
what is the effect of the oxidation of starches
transformation of hydroxyl groups into carboxyl groups (COOH)
what are the possibilities of reactions in starches when they are undergoing pyroconversion
- hydrolysis of 1-4 and 1-6
- transglucosidation (1,3 or 1,5)
- caramelization
- repolymerization of free sugars
what is the technique that produces cold water soluble starch
the dry pyroconversion
what are the three basic product produced by pyroconversion
1- white dextrins
2- yellow dextrins
3- british gums
how are made syrup by acid hydrolysis
starch is gelatinized by hot steam, then hydrchloric acid can hydrolyse the bonds.
how can you measure the starch breakdown in acidic or enzymatic hydrolysis
by measuring the reducing sugar content of the hydrolysate (fehling’s) –> it will increase.
higher is the D.E and ____ is the sweetness
higher
what is the maximum DE of acid hydroluysed starch and why
The DE of acid hydrolysed can’t be higher than 50% because of the equilibrium between polymerization and hydrolysis.
a-amylase is an endoenzyme or exoenzyme
endonzyme
b-amylase is an endoenzyme or exoenzyme
exoenzyme
___ changes the viscosity rapidly while ___ doesn’t
a-amylase
b-amylase
____ is also known as saccharifyin enzyme
b-amylase
how is invert sugar made
by heating sucrose.
why is invert sugar used in the food industry
because more stable than sucrose (the glycosydic bond is heat labile in sucrose).
what are the advantages of HFCS
1- more sweet
2. more soluble
3- doesn’‘t crystallize easily because of the mixture of sugars.
____ is used to increase the viscosity without adding calories
CMC
Pectic substances are made from the polymers of ____
galacturonic acid.
what are the properties of guar gum and locust bean gum?
1- viscosity not affected by pH
2 -stability and rheology not affected by processing
3- compatible with starches, cellulose and other gums.
what is the basic unit of guar gum and locust bean gum
2 mannose and a galactose
what is the basic unit of pectin
galacturonic acid (methylated or not)
what is the basic unit of carrageenan
D-galactose and L-galactose
what is the basic units of alginates
D-manuronic acid and L-glucuronic acid
what are the gums that can form gels with the use of divalent ions for the cross-linking
- low methoxy pectin
- carboxymethyl cellulose
- alginates
what is the basic unit of dextrans
are made from glucose unit linked by a alpha 1-6 and branched by a alpha 1-3.
what is the basic unit of xanthan gum ?
D-glucose, D-mannose, and D-galacturonic acid, present in approximately a 3:3:2 ratio.
