6. Starch

Question 1

What is amylose

Answer 1

D glucose polymer with alpha 1 4 linkages and few alpha 1 6 branches

Question 2

What is amylopectin

Answer 2

D glucose polymer with alpha 1 4 linkages and about 5 percent alpha 1 6 branches

Question 3

What is the structural difference between amylose and amylopectin

Answer 3

Amylose is mostly linear and amylopectin is highly branched

Question 4

What is an A chain in amylopectin

Answer 4

A branch with no further branches

Question 5

What is a B chain in amylopectin

Answer 5

A branch that carries other A or B chains

Question 6

What is a C chain in amylopectin

Answer 6

The central chain containing the only reducing end

Question 7

Which chain in amylopectin contains the reducing end

Answer 7

The C chain

Question 8

What crystal structures can amylose form

Answer 8

Double helix and single helix inclusion complexes

Question 9

What is the A pattern in starch

Answer 9

X ray pattern of well organized double helices

Question 10

What is the B pattern in starch

Answer 10

X ray pattern of less densely packed double helices

Question 11

What is the V pattern in starch

Answer 11

Single helix inclusion complex

Question 12

What happens first during starch gelatinization

Answer 12

Water enters granules and they swell

Question 13

What happens at maximum viscosity during gelatinization

Answer 13

Granules are swollen and amylose leaks out

Question 14

What happens when granules degrade during heating

Answer 14

Intermolecular forces break and soluble starch forms

Question 15

What happens during cooling after gelatinization

Answer 15

Reassociation of starch chains and gel formation

Question 16

What is setback in starch

Answer 16

Recrystallization of amylose during cooling

Question 17

What does setback indicate

Answer 17

Extent of amylose retrogradation

Question 18

What is starch retrogradation

Answer 18

Reassociation and crystallization of gelatinized starch

Question 19

What is the temperature dependence of retrogradation

Answer 19

Nucleation increases at low temperature

Question 20

Which starch fraction retrogrades fastest

Answer 20

Amylose

Question 21

Which starch fraction causes bread staling

Answer 21

Amylopectin

Question 22

What is staling

Answer 22

Loss of bread softness due to starch retrogradation

Question 23

How do exo amylases inhibit staling

Answer 23

They remove outer branches of amylopectin

Question 24

What properties must anti staling enzymes have

Answer 24

Exo acting not endo acting suitable pH and temperature and no glucose formation

Question 25

How can staling be quantified

Answer 25

DSC or firmness measurements

Question 26

How do emulsifiers inhibit staling

Answer 26

They form single helix inclusion complexes with amylose

Question 27

How does chemical modification change starch properties

Answer 27

It alters crystallization melting and swelling behavior

Question 28

Which bond does alpha amylase hydrolyze

Answer 28

Alpha 1 4

Question 29

Is alpha amylase exo or endo

Answer 29

Endo

Question 30

Which bond does isoamylase hydrolyze

Answer 30

Alpha 1 6

Question 31

Is isoamylase exo or endo

Answer 31

Endo

Question 32

Which bond does beta amylase hydrolyze

Answer 32

Alpha 1 4

Question 33

Is beta amylase exo or endo

Answer 33

Exo

Question 34

What is the main product of beta amylase

Answer 34

Beta maltose

Question 35

Which bonds does glucoamylase hydrolyze

Answer 35

Alpha 1 4 and alpha 1 6

Question 36

Is glucoamylase exo or endo

Answer 36

Exo

Question 37

What is the product of glucoamylase

Answer 37

Beta D glucose

Question 38

Which bonds does pullulanase type I hydrolyze

Answer 38

Alpha 1 6

Question 39

Which bonds does pullulanase type II hydrolyze

Answer 39

Alpha 1 6 and alpha 1 4

Question 40

What does alpha in alpha amylase refer to

Answer 40

Product has alpha configuration

Question 41

What does beta in beta amylase refer to

Answer 41

Product has beta configuration

Question 42

Which enzyme is needed for full degradation of amylopectin

Answer 42

Glucoamylase

Question 43

What is the glucose yield from 100 g dry starch

Answer 43

111 point 1 g glucose

Question 44

What happens to iodine color with endo amylase

Answer 44

Rapid loss of color due to rapid DP reduction

Question 45

What happens to iodine color with exo amylase

Answer 45

Slow loss of color because chain length decreases slowly

Question 46

What is the relationship between reducing sugars and iodine intensity for endo enzymes

Answer 46

Fast increase in reducing sugars and fast drop in iodine color

Question 47

What is the relationship between reducing sugars and iodine intensity for exo enzymes

Answer 47

Slow increase in reducing sugars and slow drop in iodine color