PPI Spring Meeting 2001 - Abstract
Thermal and Alternative Processing Technologies
K. P. Sandeep
Department of Food Science, North Carolina State University
In recent years, the demand for higher quality products from
consumers is on the rise. In an effort to meet this need, researchers
have been investigating alternative processing techniques. Some
of the alternative thermal techniques that have been investigated
are discussed here. Infrared heating (3 x 1011 - 4 x 1014 Hz)
serves as a quick means for surface heating and disinfection (seeds,
peas, ground beef patties, baked potatoes). Ohmic heating involves
passing electric current through a product (liquid whole eggs,
tomato sauces) to heat or sterilize it. The liquid and particulates
in a food can be heated at the same (rapid) rate using this technique.
However, products might have to be reformulated (to include more
salts) to facilitate heating.
The effectiveness of microwave (3 x 108 - 3 x 1011 Hz) and radio
frequency (3 x 103 - 3 x 108 Hz) heating depends on the dielectric
properties of the food. In radio frequency heating, the food is
placed between two plates, the polarity of which is reversed at
radio frequency. Microwave radiations heat up most polar molecules,
each having different dielectric properties, while radio frequency
waves predominantly heat up only the highly polar water molecules.
High pressure (100-800 MPa) is effective in inactivating many
microorganisms during processing of meats, fruit juices, jams,
and jellies. Ultrasonic waves cause an irreversible lethal effect
to some microorganisms due to cavitation (5550°C, 50 MPa).
Membrane processing has been used for concentration of liquid
foods, reduction of microbial counts, demineralization, production
of whey protein concentrate, and for aroma recovery.
The pulsed light technology uses light flashes (200 nm-1 mm)
at 1-10 Hz for a few microseconds to inactivate fungi and bacterial
spores on surfaces of fruits, vegetables, poultry, fish, and meat.
It is non-ionizing and cannot penetrate opaque materials. The
pulsed electric field technology involves the use of high intensity
electric field (1-40 kV/cm) at 1-5 Hz for a few microseconds to
inactivate microorganisms (by electroporation) such as E. Coli,
Staphylococus, and Pseudomonas in products such as liquid whole
eggs, apple juice, milk, and soups.
Irradiation involves the use of gamma rays (produced from Co-60
or Cs-137), accelerated electrons or X-rays to destroy microorganisms
(E. Coli, Trichinella, Salmonella) in spices, poultry, and pork.
Ultraviolet light has been used to sterilize air, milk, food packaging
surfaces, and packaging equipment and also to minimize souring
of vegetables. Ozone is primarily used to purify water. Ozonated
water has been used to wash fresh fish, meat, and vegetables.
It is also used as a sanitizing agent and performs better than
chlorine in this respect. Factors such as cost, scale-up issues,
range of applicability, establishment of health effects of these
technologies, and development of a database for approval by regulatory
agencies are some of the reasons for these technologies not being
adopted on a large scale.
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