Vacuum frying Flashcards
Vacuum frying conditions
high-pressure lower temperature
what does having pressure below atmospheric do to the evaporation temperature
decreases it
characteristics of vacuum frying
lower frying temp
less oil content
higher quality
decrease oxidation/browning (less air during frying)
less acrylamide formation.
describe process flow chart for vacuum frying
peeling/coring
frying
vacuum cooling
removal of excess oil
packing with nitrogen
advantages ot vacuum frying
preservation of natural colours and flavours
less acrylamide
reduced fat products
can process food with high-reducing sugars
high evaporation rates
improved texture
what is the drying temperature affected by
vacuum level
intial and final moisture levels
what sensory properties does fry time affect
colour and texture
what attributes are not affected by temp
colour
fat content
what is the effect of pressure on frying conditions
temp decreases
mass transfer increases
oil content decreases
what process is vacuum frying similar to
freeze drying
-but better mouth feel and sensory attributes
why two processes does vacuum frying carry out
mass and heat transfer
Advantages to using lower temperature frying
better colour, and sensory attributes
retains nutrients
less oil content
how does a vacuum effect oil diffusion
vacuum above surface of the oil which creates resistance
-decreases diffusion
how is lipid oxidation and enzymatic/non-enzymatic browning reduced
due to absence of air during drying
how is acrylamide formed
exposing carbohydrates/starchy material to high temperatures
compare drying times for conventional, vacuum fry and freeze-dried
conventional: 2 -16 hrs
vacuum:
freeze-dried: 20 hrs +
temp of deep frying
130-160C
basic principles
under vacuum, lower temp required for water to evaporate
type of heat transfer exploited
conductive and convective
why is mass transfer faster than other types of drying
utilises both convective and conductive heating
how is the shape maintained/fixed
the outisde becomes crispy adn hardened
what does the hardening/fixing of the outside of the food product prevent
prevents cellular collapse of the product
what does the vacuum on the surface of the oil do
enhance moisture movement
prevent oil uptake
how is the shape maintained/fixed
the outside becomes crispy and hardened
explain the heat transfer phenomenom
heat from the oil moves into the product and evaporates the water
explain the mass transfer phenomenon
water from the product diffuses into the oil
how does the simultaneous heat and mass transfer contribute to crispiness
allows the product to maintain structure and porosity
machinary required
heavy metal container
vacuum pump connected to water trap
motor
role of motor
creates movement of the hot oil
role of heavy metal container
to support vaccum
role of vacuum pump
generate vaccum
role of water trap
absorb moisture generated by vacuum
how does the motor improve convective heat transfer
by moving the oil
how is the temperature, pressure etc controlled
using a computer
effect of pressure on temp, mass transfer, oil content
temp decreases
mass transfer increases
oil content decreases
types of pre-treatment that have shown to be effective
oven drying
