Vacuum frying

Question 1

Vacuum frying conditions

Answer 1

high-pressure lower temperature

Question 2

what does having pressure below atmospheric do to the evaporation temperature

Answer 2

decreases it

Question 3

characteristics of vacuum frying

Answer 3

lower frying temp
less oil content
higher quality
decrease oxidation/browning (less air during frying)
less acrylamide formation.

Question 4

describe process flow chart for vacuum frying

Answer 4

peeling/coring
frying
vacuum cooling
removal of excess oil
packing with nitrogen

Question 5

advantages ot vacuum frying

Answer 5

preservation of natural colours and flavours
less acrylamide
reduced fat products
can process food with high-reducing sugars
high evaporation rates
improved texture

Question 6

what is the drying temperature affected by

Answer 6

vacuum level
intial and final moisture levels

Question 7

what sensory properties does fry time affect

Answer 7

colour and texture

Question 8

what attributes are not affected by temp

Answer 8

colour
fat content

Question 9

what is the effect of pressure on frying conditions

Answer 9

temp decreases
mass transfer increases
oil content decreases

Question 10

what process is vacuum frying similar to

Answer 10

freeze drying
-but better mouth feel and sensory attributes

Question 11

why two processes does vacuum frying carry out

Answer 11

mass and heat transfer

Question 13

Advantages to using lower temperature frying

Answer 13

better colour, and sensory attributes
retains nutrients
less oil content

Question 14

how does a vacuum effect oil diffusion

Answer 14

vacuum above surface of the oil which creates resistance
-decreases diffusion

Question 15

how is lipid oxidation and enzymatic/non-enzymatic browning reduced

Answer 15

due to absence of air during drying

Question 16

how is acrylamide formed

Answer 16

exposing carbohydrates/starchy material to high temperatures

Question 17

compare drying times for conventional, vacuum fry and freeze-dried

Answer 17

conventional: 2 -16 hrs
vacuum:
freeze-dried: 20 hrs +

Question 18

temp of deep frying

Answer 18

130-160C

Question 19

basic principles

Answer 19

under vacuum, lower temp required for water to evaporate

Question 20

type of heat transfer exploited

Answer 20

conductive and convective

Question 21

why is mass transfer faster than other types of drying

Answer 21

utilises both convective and conductive heating

Question 22

how is the shape maintained/fixed

Answer 22

the outisde becomes crispy adn hardened

Question 23

what does the hardening/fixing of the outside of the food product prevent

Answer 23

prevents cellular collapse of the product

Question 24

what does the vacuum on the surface of the oil do

Answer 24

enhance moisture movement
prevent oil uptake

Question 25

how is the shape maintained/fixed

Answer 25

the outside becomes crispy and hardened

Question 26

explain the heat transfer phenomenom

Answer 26

heat from the oil moves into the product and evaporates the water

Question 27

explain the mass transfer phenomenon

Answer 27

water from the product diffuses into the oil

Question 28

how does the simultaneous heat and mass transfer contribute to crispiness

Answer 28

allows the product to maintain structure and porosity

Question 29

machinary required

Answer 29

heavy metal container vacuum pump connected to water trap motor

Question 30

role of motor

Answer 30

creates movement of the hot oil

Question 31

role of heavy metal container

Answer 31

to support vaccum

Question 32

role of vacuum pump

Answer 32

generate vaccum

Question 33

role of water trap

Answer 33

absorb moisture generated by vacuum

Question 34

how does the motor improve convective heat transfer

Answer 34

by moving the oil

Question 35

how is the temperature, pressure etc controlled

Answer 35

using a computer

Question 36

effect of pressure on temp, mass transfer, oil content

Answer 36

temp decreases mass transfer increases oil content decreases

Question 37

types of pre-treatment that have shown to be effective

Answer 37

oven drying