Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

FOSC202 > Physical properties of milk > Flashcards

Physical properties of milk Flashcards

(58 cards)

Start Studying
1
Q

physical structures of milk

A

colloidal system
oil in water emulsion
solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

why is milk a colloidal system

A

casein micelles and globular protein

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

why is milk an oil-in-water solution

A

milk fat

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

why is milk a solution

A

sugar
proteins
minerals
vitamins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the Tyndall effect

A

the ability of colloids to disperse and scatter light
-when light is shined through milk you can see the path

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

why is milk fat yellow

A

beta carotene in the animal diet

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

why is milk white

A

scattering of light by colloidal particles and fat globules

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

why does whey have a greenish tinge

A

B2-riboflavin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

why is trim milk slightly blue

A

caseins scatter blue wavelength slightly more than other colors

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

pH of raw milk

A

6.5-6.7

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

why is milk a buffer

A

diffusable salts (phosphates) and proteins

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is an indicator of mastitis in milk

A

slightly higher pH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

why are somatic cell counts (SCC) counted in milk

A

to test for mastitis
-SCC are higher in milk when the cow has mastitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what indicates a positive mastitis test

A

gelling of the milk and RMT solution

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what does the electrical conductivity of milk assess

A

the total ionic content (Na+, K+, Cl-)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

at 25 degrees what is the normal conductivity of milk

A

0.005 mho cm-1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

why do whey and skim milk have higher conductivity than whole milk

A

fat reduces the specific conductance

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

How can conductivity be used to screen for mastitis

A

higher Na+ and Cl- in the milk of cows with mastitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

what else can electrical conductivity test for

A

residual cleaning agents in milk
index of milk fermentation
ohmic (electrical) heat processing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what happens to CaP during fermentation

A

fermentation dissolves CaP groups of casein which increases the amount of free ions increasing conductivity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is the typical Eh (redox potential) of milk at 30C

A

+0.2-+0.3 volt

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what does having a positive Eh mean

A

it wants to become negative so it’s prone to spoilage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what kind of Eh do heated/powdered milks have

A

negative

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what does Eh depend on (5)

Study These Flashcards
A

dissolved oxygen, ascorbic acid, riboflavin, cysteine-cysteine content, and pH

25
what two tests used to check the microbial quality of milk rely on redox potential
methylene blue resazurin
26
what happens to milk without bacteria when methylene blue is added
the milk turns blue because the oxygen in milk keeps the methylene blue in the oxidised form
27
what colour is the oxidised form of methylene blue
blue
28
What happens to methylene blue when it is added to milk that has bacteria
the bacteria use the oxygen and the methylene blue turns into the reduced colourless form
29
what does the speed at which the methylene blue turn colorless relate to
the amount of bacteria present in the milk
30
difference between resazurin and methylene blue test
resazurin is more sensitive and gives an indication of pH
31
what color is resazurin at pH 3.8
orange/yellow
32
what color shows the best quality of milk when tested with resazurin
slate blue (no color change)
33
what colour indicates a pH above 6.5 (resazurin test)
purple
34
what is responsible for the surface tension of the milk
beta-casein + protease peptones (proteolytic products)
35
what is surface tension
work required to increase the surface area
36
lactose and salt ______ ST while fat ______ it
increases decreases
37
surface-active properties of milk are relevant for... (4)
creaming fat globule membrane function foaming emulsifier use in dairy products
38
what processing methods tend to increase surface tension
heating sterilisation homogenization shear (rubbing/missing things through milk)
39
what is the specific heat
amount of heat required to raise 1g of milk by 1C
40
what happens to milk as it becomes more concentrated
thermal conductivity decreases
41
what is thermal processing used for
extend shelf life increase WHC reduce synereisis
42
why is milk heat stable
protein and salt content
43
How does foaming affect the heat efficacy of heat transfer
decreases it
44
what is a rheological property
how materials behave when heat is applied to them
45
why is milk considered a Newtonian fluid
no matter how much shear force is applied the viscosity remains the constant
46
what does the viscosity of milk depend on
-concentration and degree of hydration of casein micelles -temperature -concentration and size of fat globules
47
what are colligative properties
physical changes that can result from adding solutes to a solvent
48
examples of colligative properties
vapour pressure lowering boiling point elevation freeezing point depression osmotic pressure
49
examples of colligative properties
vapor pressure lowering boiling point elevation freezing point depression osmotic pressure
50
which colligative properties does milk have
boiling point elevation freezing point depression osmotic pressure
51
what does osmotic pressure depend on
osmotic concentration -total concentration of all solutes in a solution
52
the freezing point of milk can be used to test ?
if it has been diluted
53
which has a lower freezing point yoghurt or milk
yoghurt because the lactose has been converted to lactic acid which increases the osmotic concentration
54
which has a lower freezing point yoghurt or milk
yoghurt because the lactose has been converted to lactic acid which increases the osmotic concentration
55
what is specific gravity
ratio of mass of a solution/substance to the mass of a similar volume of water
56
list ice-cream, whole milk and skim milk in order of increasing specific gravity
skim>whole>ice cream
57
what is specific gravity used for
testing if milk has been diluted assess total solids
58
what instrument is used to measure specific gravity
lactometer

FOSC202 (28 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions