Preservation and processing

Question 1

thermisation heat, time, and goal

Answer 1

65C, 15 seconds, kill heat-sensitive spoilage

Question 2

goal of pastuerisation

Answer 2

killing spoilage and pathogenic bacteria

Question 3

types of pastuerisation and what it involves

Answer 3

low temp: 65C for 30 min
high temp: 72C for 15 secs

Question 4

goal of sterilisation and what it involves

Answer 4

kill all bacteria including spores
-UHT: 140C for 5 secs
-container: 112C for 15 mins

Question 5

if milk has greater than 10% fat why does the temperature need to increase

Answer 5

fat is not a good conductor of heat

Question 6

what is the most heat-stable bacterium in milk

Answer 6

mycobacterium tuberculosis

Question 7

which enzyme is used as an indicator of pasteurisation sufficiency

Answer 7

alkaline phosphotase

Question 8

what are the negative impacts of pasteurisation

Answer 8

development of cooked/flat flavour
maillard reaction
affects heat sensitive nutrients

Question 9

what can happen to milk proteins during pastuerisation

Answer 9

denaturation

Question 10

what can happen to milk if pasteruisation is done under basic conditions

Answer 10

degradation of lactose to lactulose and acids

Question 11

what is lactulose

Answer 11

non-fermentable and non-absorbable sugar

Question 12

what can severe heat treatment during pasteurisation of milk cause

Answer 12

heat induced coagulation
dephosphorylation and hydrolysis of caseins

Question 13

alternative to pastuerisation

Answer 13

native antimicrobials in milk
microfiltration
bactofugation
UV pasteurisation
microwave or pulsed electric feilds

Question 14

how can native antimicrobials in milk be used to treat it

Answer 14

use of enzymes, lactoferrin, lactenins to kill or control bacteria growth

Question 15

how can microfiltration be used to treat milk

Answer 15

ceramic filter removes (99.9%) bacteria
-it removes fat globules so can alter flavour

Question 16

how can bactofugation be used to treat milk

Answer 16

removes microbes using centrifugal force

Question 17

how can UV be used to treat milk

Answer 17

UV ligh frequencies affect the DNA of bacteria

Question 18

why is UV treatment difficult

Answer 18

the opacity of milk makes it difficult to penetrate further than the surface

Question 19

how can microwave/electric feilds be used to treat milk

Answer 19

microwave energy/electric feilda destroy bacteria

Question 20

how can microwave/electric feilds be used to treat milk

Answer 20

microwave energy/electric field destroys bacteria

Question 21

why is milk prone to creaming

Answer 21

fat is less dense than water so it floats to the top

Question 22

how does homogenisation affect the sensory properties of milk

Answer 22

creamier, white colour, blander

Question 23

why must pasturisation occur before homogenisation

Answer 23

inactivate lipases making it less prone to rancidity

Question 24

how can the coagulation of milk occur

Answer 24

acid addition
acid/heat addition
enzyme action
age gelation

Question 24

how can the coagulation of milk occur

Answer 24

acid addition
acid/heat addition
enzyme action
age gelation

Question 25

how does acid coagulation occur

Answer 25

micelle have a negative charge under normal pH but when it reaches the isoelectric point (around 4.6) the micelles aggregate

Question 26

how does acid/heat coagulation occur

Answer 26

whey proteins are denatured by heat then in the presecne of acid of acid begin to aggregate to other whey and/or caseins

Question 27

how does enzyme coagulation occur

Answer 27

chymosin (enzyme in rennet) cuts off the k-casein which reduced the intra-micelles repulsion which leads to coagulation

Question 28

how does age gelation cause coagulation

Answer 28

actual cause is unknown, possible
-breakdown of casein by heat stable enzymes (plasmin)
-polymerisatoin of casein and whey through maillard reaction
-formation of kappa-casein-beta-lactoglobulin

Question 29

why is evaporated milk thicker and creamier than normal milk

Answer 29

more concentrated milk solids

Question 30

what concentrated is milk concentrated to before drying

Answer 30

50%

Question 31

key features, advantages, and disadvantages to spray drying

Answer 31

uses hot air
retains nutrients
moderate cost

Question 32

key features, advantages, and disadvantages to drum drying

Answer 32

uses hot surfaces
very low cost
dried milk has cooked flavour

Question 33

key features, advantages, and disadvantages to freeze drying

Answer 33

uses sublimation
retains nutrients
high costs

Question 34

what is membrane processing techology

Answer 34

separation that uses semi-permeable membrane filters to concentrate/fractionate the liquid

Question 35

what is the permeate

Answer 35

liquid passing through the membrane

Question 36

what is the retentate

Answer 36

the concentrate (retained liquid)

Question 37

four types of membrane processes

Answer 37

reverse osmosis
nanofiltration
ultrafiltration
microfiltration

Question 38

what becomes the permeate during reverse osmosis

Answer 38

water

Question 39

what becomes the permeate in nanofiltration

Answer 39

water and minerals

Question 40

what is fouling

Answer 40

blockage of pores

Question 41

what are the limitations of membrane processing

Answer 41

creates a bacteria biofilm and fouling cna occur