Exam

Question 1

Give 4 causes of protein denaturation

Answer 1

Heat
Shear
pH
interfacial forces

Question 2

What sugar gives the most sweetness?

Answer 2

Fructose

Question 3

What sugar should be added for spread ability?

Answer 3

Low methoxy pectin

Question 4

What sugar should be added for thickening? (give 2)

Answer 4

Alginate
Locust Bean Gum

Question 5

What are the major changes the occur in malting?

Answer 5

-Softening of grain
-Activation of enzymes
-Some formation of starch and soluble carbohydrates

Question 5

What are the major changes the occur in kilning?

Answer 5

-dehydration
-prevents further germination and enzyme activity

Question 6

What are the major changes the occur in milling?

Answer 6

-Physical breakdown of grain
-Increased starch/enzyme contact
-Increased surface area

Question 7

What are the major changes the occur in mashing?

Answer 7

-enzymatic starch hydrolysis
-formation of glucose and maltose
-separation of sugars from husks

Question 8

What are the major changes the occur in brewing?

Answer 8

-hop addition
-alpha acid extraction
-isomerisation to iso alpha acids
-enzyme denaturation

Question 9

What factors favour yeast growth over bacterial growth in beer fermentation?

Answer 9

-ethanol
-low pH
-low temp
-some antibacterial compounds extracted from hops

Question 10

What is the Crabtree effect?

Answer 10

Yeast produce ethanol preferentially in high glucose concentrations.

Question 11

What are the implications of the crabtree effect for yeast production.

Answer 11

Fed batch required to achieve higher productivity.

Question 12

What are the 8 stages in a polymeric membrane cleaning cycle?

Answer 12

-Product drainage
-Pre rinse
-alkali recirculation
-rinse
-acid recirculation
-rinse
-alkali + chlorine recirculation
-rinse

Question 13

What are the conditions for the alkali and acid rinses in polymeric membrane cleaning?

Answer 13

-50 C
-alkali pH 10.8-11
-acid pH 2.0-2.2

Question 14

what is the purpose of acid cleaning step in polymeric membrane cleaning?

Answer 14

-mineral/salt removal

Question 15

what is the purpose of alkali cleaning step in polymeric membrane cleaning?

Answer 15

-fat/protein removal

Question 16

what is the purpose of the alkali/chorine step in polymeric membrane cleaning?

Answer 16

disinfection, alkali moves equilibrium to free chlorine

Question 17

what chemical is used to disinfect in membrane cleaning?

Answer 17

Sodium hypochlorite NaOCL

Question 18

What chemical class is used for removal of insoluble metals in membrane cleaning?

Answer 18

Sequestrants

Question 19

What chemical class is used for the removal of hydrophobic species in membrane cleaning?

Answer 19

Surfactants

Question 20

Why must casein microfiltration be conducted below a critical flux?

Answer 20

Excessive flux causes formation of a “dynamic membrane” of foulants, which will have a reduced size cut and retain whey protein.

Question 21

What causes the transition from the constant rate drying step to falling rate drying step? What is this point called?

Answer 21

Loss of continuous film of water at solid surface. Critical moisture content.

Question 22

give 2 causes of surface enrichment

Answer 22

-large slowly diffusing molecules
-fast evaporation (high temperature)

Question 23

What are the physical changes caused by extrusion (6)?

Answer 23

-mixing
-kneading
-agglomeration
-shearing
-shaping
-dehydration

Question 24

What are the chemical changes caused by extrusion (4)?

Answer 24

-cooking -pasteurisation -protein denaturation -starch gelatinisation

Question 25

What are the steps of starch gelatinisation?

Answer 25

-disintegration and hydration -viscosity increase due to starch untangling -breaking of untangled starch clusters reducing viscosity -thermal and enzymatic degradation of starch

Question 26

What are some reducing monosaccharides?

Answer 26

All

Question 27

What is a common non reducing disaccharide?

Answer 27

Sucrose

Question 28

What thermodynamic property is responsible for emulsion instability?

Answer 28

Interfacial tension

Question 29

What is responsible for interfacial tension?

Answer 29

Net attractive force towards the bulk of a fluid

Question 30

What is the mechanism for pH based casein coagulation?

Answer 30

Lowering of pH reduces charge on casein micelles, causing the hairy layer to collapse

Question 31

What is the mechanism for rennet based coagulation?

Answer 31

Cleavage of the kappa casein chain removes the hairy layer from micelles.

Question 32

What roles do additional cultures play in cheese making?

Answer 32

-add flavour -promote ripening through proteolytic and lipolytic enzymes -form holes

Question 33

give 4 ways caramelisation and mailard browning differ.

Answer 33

-mailard requires protein + reducing sugar -mailard is fast at high temp -caramelisation requires temps greater than 150 C -caramelisation requires very low water content -mailard is acid inhibited -produce different flavours

Question 34

how to identify constant pressure filtration equation?

Answer 34

V/2

Question 35

how to identify constant rate filtration equation?

Answer 35

not constant 2

Question 36

What are the major steps in white wine production?

Answer 36

1. Destemming 2. Crushing 3. Maceration 4. Pressing 5. Fermentation 6. Maturation and Clarification 7. Stabilising and Finishing

Question 37

What are the major steps in red wine production?

Answer 37

1. Destemming 2. Crushing 3. Fermentation and maceration 4. Pressing 5. Malolactic Fermentation 6. Maturation and Clarification 7. Stabilising and Finishing

Question 38

What changes occur in maceration?

Answer 38

-Agitation of Skins -Sugars and enzymes released from skins -Phenolics released from skins and seeds

Question 39

What changes occur in pressing?

Answer 39

-separation of skins from juice

Question 40

What changes occur in malolactic fermentation?

Answer 40

-conversion of malic acid to lactic acid by lactic acid bacteria -increase in pH

Question 41

What common preservative is added to wines? In what production stage is it added?

Answer 41

Sulphur Dioxide, crushing

Question 42

What changes occur in fining?

Answer 42

Absorbsion and precipitation of suspended material

Question 43

What are the two major acids present in grapes?

Answer 43

Tartaric acid, malic acid

Question 44

What water activity is required for bacterial growth?

Answer 44

0.9

Question 45

What water activity is required for mould growth?

Answer 45

0.6

Question 46

What water activity is required for yeast growth?

Answer 46

0.8

Question 47

draw the curves for non log linear cell death

Answer 47

check slides

Question 48

give a common cause of non log linear survival?

Answer 48

mixed strains with thermal resistant microbes

Question 49

give a common type of homogeniser?

Answer 49

rotor-stator mixer

Question 50

What are the 3 regions of current density vs voltage called?

Answer 50

ohmic region, plateau region, overlimiting region.

Question 51

What is a cause of the increase in current density in the overlimiting region?

Answer 51

Water splitting

Question 52

Give the most likely cause of poor current efficiency in electrodialysis?

Answer 52

Water splitting

Question 53

Give 2 minor potential causes of poor current efficiency in electrodialysis?

Answer 53

Poor membrane selectivity Back diffusion of ions

Question 54

Which stream is the product in electrodialysis?

Answer 54

Diluate

Question 55

Which stream is the waste (salt solution) in electrodialysis?

Answer 55

Concentrate