week12C1 : starch modifications

Question 1

what is the inconvenient with pre-gelatinized starch

Answer 1

you need more starch for the same viscosity.

Question 2

how is pre-gelatinized starch made ?

Answer 2

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.

Question 3

how is produced thin-boiling starches

Answer 3

boiling the starch under gel temp in acid  neutralization  drying.

Question 4

what is the purpose of thin boiling starch

Answer 4

producing low viscosity fluids (candy industry).

Question 5

what is the method used to produce granules resistant to shear?

Answer 5

the cross-linking method

Question 6

what are the agent used for the cross-linking of starches

Answer 6

acetic, citric or adipic anhydrides are used

Question 7

T or F : cross-linked starches are less suseptible to acid

Answer 7

true

Question 8

what is the goal of modifying starches byh adding charges

Answer 8

to reduce the polymer polymer hydrogen bonding.

Question 9

____ produces cold-water soluble starch.

Answer 9

dry pyroconversion

Question 10

what are the reagents used in the formation of oxidized starches

Answer 10

1. sodium hypochlorite

2. hydrogen peroxide

Question 11

what is the effect of the oxidation of starches

Answer 11

transformation of hydroxyl groups into carboxyl groups (COOH)

Question 12

what are the possibilities of reactions in starches when they are undergoing pyroconversion

Answer 12

1. hydrolysis of 1-4 and 1-6
2. transglucosidation (1,3 or 1,5)
3. caramelization
4. repolymerization of free sugars

Question 13

what is the technique that produces cold water soluble starch

Answer 13

the dry pyroconversion

Question 14

what are the three basic product produced by pyroconversion

Answer 14

1- white dextrins
2- yellow dextrins
3- british gums

Question 15

how are made syrup by acid hydrolysis

Answer 15

starch is gelatinized by hot steam, then hydrchloric acid can hydrolyse the bonds.

Question 16

how can you measure the starch breakdown in acidic or enzymatic hydrolysis

Answer 16

by measuring the reducing sugar content of the hydrolysate (fehling’s) –> it will increase.

Question 17

higher is the D.E and ____ is the sweetness

Answer 17

higher

Question 18

what is the maximum DE of acid hydroluysed starch and why

Answer 18

The DE of acid hydrolysed can’t be higher than 50% because of the equilibrium between polymerization and hydrolysis.

Question 19

a-amylase is an endoenzyme or exoenzyme

Answer 19

endonzyme

Question 20

b-amylase is an endoenzyme or exoenzyme

Answer 20

exoenzyme

Question 21

___ changes the viscosity rapidly while ___ doesn’t

Answer 21

a-amylase

b-amylase

Question 22

____ is also known as saccharifyin enzyme

Answer 22

b-amylase

Question 23

how is invert sugar made

Answer 23

by heating sucrose.

Question 24

why is invert sugar used in the food industry

Answer 24

because more stable than sucrose (the glycosydic bond is heat labile in sucrose).

Question 25

what are the advantages of HFCS

Answer 25

1- more sweet
2. more soluble
3- doesn’‘t crystallize easily because of the mixture of sugars.

Question 26

____ is used to increase the viscosity without adding calories

Answer 26

CMC

Question 27

Pectic substances are made from the polymers of ____

Answer 27

galacturonic acid.

Question 28

what are the properties of guar gum and locust bean gum?

Answer 28

1- viscosity not affected by pH
2 -stability and rheology not affected by processing
3- compatible with starches, cellulose and other gums.

Question 29

what is the basic unit of guar gum and locust bean gum

Answer 29

2 mannose and a galactose

Question 30

what is the basic unit of pectin

Answer 30

galacturonic acid (methylated or not)

Question 31

what is the basic unit of carrageenan

Answer 31

D-galactose and L-galactose

Question 32

what is the basic units of alginates

Answer 32

D-manuronic acid and L-glucuronic acid

Question 33

what are the gums that can form gels with the use of divalent ions for the cross-linking

Answer 33

1. low methoxy pectin
2. carboxymethyl cellulose
3. alginates

Question 34

what is the basic unit of dextrans

Answer 34

are made from glucose unit linked by a alpha 1-6 and branched by a alpha 1-3.

Question 35

what is the basic unit of xanthan gum ?

Answer 35

D-glucose, D-mannose, and D-galacturonic acid, present in approximately a 3:3:2 ratio.