High Pressure

Question 1

type of processing for:
solid foods
liquids

Answer 1

solid: batch
liquid: semi continous

Question 2

machinery required

Answer 2

pressure vessel and pressure generator

Question 3

describe process

Answer 3

packaged food is loaded in and the container is sealed, transmission fluid is pumped in until pressure is reached, valves are then shut for the desired time period

Question 4

why is water important

Answer 4

it is virtually incompressible

Question 5

describe process

Answer 5

packaged food is loaded in and the container is sealed, transmission fluid is pumped in until pressure is reached, and valves are then shut for desired time period

Question 6

what is the isostatic principle

Answer 6

pressure is transmitted instantaneously and uniformly throughout the sample
-independent of volume and geometry of the sample

Question 7

describe process

Answer 7

packaged food is loaded in and the container is sealed, transmission fluid is pumped in until pressure is reached, and valves are then shut for the desired time period

Question 8

describe process

Answer 8

packaged food is loaded in and the container is sealed, transmission fluid is pumped in until pressure is reached, and valves are then shut for the desired time period

Question 9

what is the isostatic principle?

Answer 9

pressure is transmitted instantaneously and uniformly throughout the sample
-independent of the volume and geometry of the sample

Question 10

why is LeChateliars principle important

Answer 10

reactions that result in a volume decrease are stimulated
-those causing a volume increase are disrupted

Question 11

what happens if bacteria tries to grow under pressure

Answer 11

bursts as system tried to reestablish equilibrium

Question 12

what happens to inoic bonds

Answer 12

broken

Question 13

what type of bonds are favoured

Answer 13

hydrogen

Question 14

what type of bonds are unaffected

Answer 14

covalent

Question 15

examples of covalent bonds in food

Answer 15

low molecular weight, resonsible for sensory nad nuutritional qualitity

Question 16

does the maillard reaction occur

Answer 16

no

Question 17

examples of changes in high molecular weight molecules

Answer 17

protein, starches have altered functionality

Question 18

where is the primary site of damage in cells

Answer 18

cell membrane
-disruption in function and leakage

Question 19

what happens to the cell membrane

Answer 19

volume and cross-sectional area of bi-layer is reduced

Question 20

what can happen to enzymes

Answer 20

change on active site conformation
alteration of intramoleuclar structure

Question 21

steps of DNA replication that are disrupted by pressure

Answer 21

replication and transcription

Question 22

are eukaryotes or prokaryotes more resistant

Answer 22

eukaryotes

Question 23

which is the most resistant stage of growth

Answer 23

stationary more than exponential

Question 24

what substrates confer protection

Answer 24

proteins, lipids and carbs

Question 25

what does a rich media supply

Answer 25

more amino acids for stressed cells

Question 26

why does pH of aqueous solutions decrease with pressure

Answer 26

electrostriction

Question 27

what temperature should be treated at

Answer 27

below ambient (2 or 10 C)

Question 28

how does applying mild heat affect the inactivation of resistant vegetative pathogens

Answer 28

more effective -E.coli -S.aureus

Question 29

two mechanisms for steralisation using pressure

Answer 29

1. lower pressure and temps causes spores to germinate and they are then inactivated by pressure 2. at higher temps a direct spore-inactivation mechanism occurs

Question 30

why are inactivation curves observed under higher temperatures for sterilisation harder to interpret

Answer 30

they dont follow first-order kinetics

Question 31

how does high pressure affect proteins

Answer 31

reversible or irreversible denaturation

Question 32

what does the denaturation of proteins depend on

Answer 32

kind of protein processing conditions pressure applied

Question 33

above what pressure does dentauration of proteins and inactivatoin of enzymes occur

Answer 33

300Mpa

Question 34

at pressure <300MPa what happens to enzyme activity

Answer 34

accelerated

Question 35

how are proteins denatured

Answer 35

destruction of hydrophobic and ion-pair bonds and unfolding of molecules

Question 36

what is HP used for in japan

Answer 36

surimi

Question 37

what happens to starch under HP

Answer 37

they can become gelatinised

Question 38

what pressure gelatinizes starch

Answer 38

400-500MPa 40-50C

Question 39

how are enzyme affected by HP

Answer 39

heat treatment is more affective for inactivation but used in combination with HP there may be inactivation

Question 40

commercial application of HP

Answer 40

mandarin juice: inibited mould grapefruit juice: inhibited bitter taste Oysters: pressure 200-300MPa 5-15 mins, 25C inactivated vibrio bacteria

Question 41

cost of HP

Answer 41

high capital cost ~10 mill production costs ~ 4.5 c per kg/l

Question 42

advantages

Answer 42

-instant and uniform treatment independent of size and geometry -once pressure is reach it does not require energy to hold it -environmentally friendly -minimal adverse effect/product stays fresh -low running cost -considered as natural process