Lecture 18: High Pressure Processing

Question 1

what is the SI unit for pressure?

Answer 1

Pa

Question 2

what is the british unit for pressure?

Answer 2

PSI

Question 3

what are equivalences of 1atm?

Answer 3

101. 3kPa
102. 1MPa
103. 7PSI

Question 4

what is 100 kPa defined by?

Answer 4

pressure exerted by a 1kg of mass on a 1cm^2 area

= 1 bar

Question 5

what is 10 kPa defined by?

Answer 5

pressure below 1m of water, or a drop in air pressure due to 1000m elevation

Question 6

what are the effects of high pressure processing?

Answer 6

• destroys microorganisms, especially vegetative cells
• microbial spores are more resistant
• inactivates enzymes
• alters functional properties
• cell wall/tissue rupture

Question 7

how does HP treatment affect nutritional quality?

Answer 7

almost no changes

Question 8

how does HP treatment affect color and texture?

Answer 8

they CAN be effected

Question 9

what bonds does HP treatment not affect?

Answer 9

covalent bonds

Question 10

what is the iso-static principle?

Answer 10

application of pressure is instantaneous and uniform throughout the sample

Question 11

what is le chatelier’s principle?

Answer 11

reactions resulting in a volume change are influenced by high pressure applications

Question 12

what are the main two HP processing principles?

Answer 12

1. isostatic principle

2. le chatelier’s principle

Question 13

reactions resulting in a volume decrease are _____ by HP

Answer 13

accelerated

Question 14

reactions resulting in a volume increase are ____ by HP

Answer 14

suppressed

Question 15

at constant T, an increase in pressure will ____ degree of ordering of the molecules

incr/dec

Answer 15

increase

Question 16

temp and pressure ___ kinetic energy associated with the molecules

incr/dec

Answer 16

increases

Question 17

what are advantages of HP processing?

Answer 17

• relatively low temp operation
• instant response and short time treatment
• uniform pressure
• natural quality
• minimal destructive effects on nutrients

Question 18

what foods is HP used for in:
A) pasteurization
B) sterilization
C) texture modifications
D: functional changes

Answer 18

A) pasteurization: juices and milk

B) sterilization: high and low acid foods

C) texture modifications: fish, egg, proteins, starches

D: functional changes: cheese, yogurt, surimi

Question 19

what is TAPS?

Answer 19

temp assisted pressure process

- pressure accelerated destruction kinetics of spores

Question 20

what is PATS?

what are advantages?

Answer 20

pressure assisted thermal process

a conventional thermal process

adv:

• adiabatic compression and decompression results in rapid heating and cooling
• high quality