HP processing

Question 1

What are the SI and imperial units for pressure?

Answer 1

SI: kPa
Imperial: PSI

Question 2

HP has mostly been studied as a replacement for:

What are other major applications? (2)

Answer 2

replacement for thermal processing
inactivate enzymes
drying

Question 3

HP will mostly affect: ___ molecules, such as:

Answer 3

bio molecules
organisms
enzymes
molecules in food (proteins, etc)

Question 4

True/False: HP will result in nutrient loss

Answer 4

False; nutrients largely unaffected

Question 5

HP will not affect ____ bonds, but will affect ______.

This results in:

Answer 5

covalent
secondary, tertiary structure
CHANGE IN FUNCTIONAL PROPERTIES

Question 6

how do fruits and veggies survive the extremely high pressure without being crushed?

Answer 6

equal pressure exerted on all sides: does not allow for deformation

Question 7

Can HP be used to kill microorganisms?

Answer 7

Yes; but spores more resistant

Question 8

the 2 principles of HP:

Answer 8

1. Iso-static principle: application of pressure is UNIFORM, and INSTANTANEOUS
2. LeChatelier’s: rxn that would cause volume decrease will be ACCELERATED by pressure
   (rxn causing volume increase will be slowed)

Question 9

Pressure will increase ____ and _____ of molecules.

A combination of temp and pressure will _____ kinetics.

Answer 9

degree of ordering
kinetic energy

accelerate

Question 10

How can HP affect texture/structure of food?

Answer 10

high mechanical stress

can cause tissue/cell rupture

Question 11

Advantages of HP: (5)

Answer 11

short time, instant response
lower temp
independent of size/shape (uniform pressure)
preserve quality (color, flavor, nutrients)
waste free, save energy

Question 12

Can HP be used for sterilizing low acid foods?

Answer 12

yes, both high and low acid foods

Question 13

How can HP be used as a texture modification aid?

Answer 13

gelatinize starch at lower temp
coagulate proteins
enhance protein abilities (due to slight denaturation, sites exposed)

Question 14

What HP process has been well studied already?

Answer 14

HP pasteurization; guidelines have been developed by FDA

Question 15

The guidelines established by ____ for HP processing dictate that:

Answer 15

USDA - FDA

must be 5 log reduction in PRESSURE RESISTANT PATHOGENS (E Coli, Salmonella, etc)

Question 16

How could HP processing be beneficial for cheese production? (2)

Answer 16

Could allow for safe, “raw” milk quality cheese
(kill pathogens but not inactivate native enzymes for ripening)

improves firmness

Question 17

if pressure is too high, what issue might occur?

Answer 17

discoloration due to denatured proteins (fish, eggs)

Question 18

Sterilization with HP is still considered a _____. Why might there be concerns?

Answer 18

need sufficient data; normal temp destruction kinetics may not apply. (pressure sensitive vs temp sensitive microbes)

Question 19

The 2 types of HP sterilization processing:

Which one is established as a method, and which one is still considered novel?

Answer 19

TAPS - temp assisted pressure sterilization
PATS - pressure assisted temp sterilization
(TAPS novel)
(PATS is accepted; since using temperature to kill)

Question 20

compression causes temperature (increase/decrease), through ____ ____. This is a very (rapid/slow) process. Why?

Answer 20

increase
adiabatic heating
very rapid heat/cooling - does not involve energy transfer

Question 21

How does PATS work? Why would PATS be advantageous to normal temperature sterilization?

Answer 21

use HP to quickly achieve necessary temperature - hold for necessary time - rapid cooling

faster, don’t need CUT since almost instantaneous, preserve quality better

Question 22

What happens to freezing point as pressure is increased?

Answer 22

depressed

Question 23

How can HP be used for freezing?

Answer 23

HP -> FP depressed -> water is supercooled (below 0, but still liquid) -> pressure released -> very rapid freezing -> continue cooling and allow for some crystal growth

Question 24

HP freezing is advantageous because:

Answer 24

very rapid -> lot of nucleation -> many tiny fine ice crystals (preserve better texture)

Question 25

How is HP used for thawing?

Answer 25

HP -> FP depressed, creates greater difference between heating temp and product freezing temp -> more rapid thawing -> pressure released

Question 26

HP thawing results in: (4)

Answer 26

firmer texture, less drip, microbe control, more rapid thawing