4. Short electric pulses (20-80kV, microseconds)
Alternative of thermal pasteurization
Used for liquid and semi-liquid food products
Microbial inactivation:- Electroporation
Factors affecting:- electric field strength,
treatment time, cell size, growth phase
Products with no air bubbles, low electrical
conductivity and easily pumpable
Stored: refrigeration
Components:- Pulse generator, treatment
chamber, control & data acquisition
5.
6. Sound waves, frequency >16 kHz
Principle:- Intracellular cavitations
Types:- high frequency low energy, low frequency
high energy, power ultrasound
Requirements:- a liquid medium, source of high
energy vibration
Applications:- a) Physical-freezing, degassing,
crystallization, extraction, filtration, drying,
homogenization/emulsification, extrusion, cleaning
b) Chemical- oxidative ageing, enzymatic activity,
bacteriocidal, effluent treatment, living cell
Microbial destruction
Designs- Ultrasonic bath, probe system, reaction
vessel, liquid whistle, resonating type
7.
8.
9. Isostatic principle
Food subjected to high hydrostatic pressure
(100-800MPa for 1 sec to 30 min)
Instantaneous and uniform
Independent of food size, shape, composition
3ºC rise in temp per 100MPa
Inactivation depends on temp
C. botulinum spores (500-700MPa, 90-
100ºC)
Order of resistance:-
Spores>gram +ve >gram -ve
10. Effects of high hydrostatic pressure:-
a) Cell enveloped related effect
b) Pressure induced cellular changes
c) Biochemical aspect
d) Genetic mechanism
△V=2.3 R T [Log Kp1-Log Kp0]/[P1-P0]
Applications:- enzyme inactivation, gel
formation, protein denaturation, tenderization
of meat, tempering of chocolate
Components:- pressure vessel, pressure
generating system, temp controller
11.
12. ITU (915±13MHz and 2450±50MHz)
Similar to visible light
Non ionizing radiation
Depends on:-size, shape, dielectric constant
Penetration depth is inversely proportional to
frequency
Penetration depth- dielectric constant & the loss
factor of food.
Lower the loss factor, greater the penetration
Mechanism:- ionic polarization, dipole rotation
Mechanism of microbial destruction
Components:- power supply, magnetron, wave
guide, stirrer, oven capacity
13.
14. Electrical energy is dissipated into heat
Also called electrical resistance heating, Joule
heating, or electro-heating.
Volumetric heating
△P=△U2/△Ω=σE2△A△Z=σE2△V
Liquid foods, soups, fruit slices in syrups,
sauces, heat sensitive liquids, proteinaceous
foods
Every 120ºC rise in temp causes 2-3 times fall
in resistance
Rapid heating 1ºC/sec
)U(=Q 2
15.
16. An evolving field
Better potential
Equipment cost (though coming down) still is
a major limiting step
Process documentation, verification
procedures need to be worked out for
government approval to assure safety
(adequate processing)