4. ๏ฝ Short electric pulses (20-80kV, microseconds)
๏ฝ Alternative of thermal pasteurization
๏ฝ Used for liquid and semi-liquid food products
๏ฝ Microbial inactivation:- Electroporation
๏ฝ Factors affecting:- electric field strength,
treatment time, cell size, growth phase
๏ฝ Products with no air bubbles, low electrical
conductivity and easily pumpable
๏ฝ Stored: refrigeration
๏ฝ Components:- Pulse generator, treatment
chamber, control & data acquisition
5.
6. ๏ฝ Sound waves, frequency >16 kHz
๏ฝ Principle:- Intracellular cavitations
๏ฝ Types:- high frequency low energy, low frequency
high energy, power ultrasound
๏ฝ Requirements:- a liquid medium, source of high
energy vibration
๏ฝ 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. ๏ฝ Isostatic principle
๏ฝ Food subjected to high hydrostatic pressure
(100-800MPa for 1 sec to 30 min)
๏ฝ Instantaneous and uniform
๏ฝ Independent of food size, shape, composition
๏ฝ 3ยบC rise in temp per 100MPa
๏ฝ Inactivation depends on temp
๏ฝ C. botulinum spores (500-700MPa, 90-
100ยบC)
๏ฝ Order of resistance:-
Spores>gram +ve >gram -ve
10. ๏ฝ Effects of high hydrostatic pressure:-
a) Cell enveloped related effect
b) Pressure induced cellular changes
c) Biochemical aspect
d) Genetic mechanism
๏ โณV=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. ๏ฝ ITU (915ยฑ13MHz and 2450ยฑ50MHz)
๏ฝ Similar to visible light
๏ฝ Non ionizing radiation
๏ฝ Depends on:-size, shape, dielectric constant
๏ฝ Penetration depth is inversely proportional to
frequency
๏ฝ Penetration depth- dielectric constant & the loss
factor of food.
๏ฝ Lower the loss factor, greater the penetration
๏ฝ Mechanism:- ionic polarization, dipole rotation
๏ฝ Mechanism of microbial destruction
๏ฝ Components:- power supply, magnetron, wave
guide, stirrer, oven capacity
13.
14. ๏ฝ Electrical energy is dissipated into heat
๏ฝ Also called electrical resistance heating, Joule
heating, or electro-heating.
๏ Volumetric heating
โณP=โณU2/โณฮฉ=ฯE2โณAโณZ=ฯE2โณV
๏ Liquid foods, soups, fruit slices in syrups,
sauces, heat sensitive liquids, proteinaceous
foods
๏ฝ Every 120ยบC rise in temp causes 2-3 times fall
in resistance
๏ฝ Rapid heating 1ยบC/sec
)U(=Q 2
๏๏ซ๏ฆ
15.
16. ๏ฝ An evolving field
๏ฝ Better potential
๏ฝ Equipment cost (though coming down) still is
a major limiting step
๏ฝ Process documentation, verification
procedures need to be worked out for
government approval to assure safety
(adequate processing)