BLBS102-c39 BLBS102-Simpson March 21, 2012 14:20 Trim: 276mm X 219mm Printer Name: Yet to Come
39 Minimally Processed Foods 755More recent reviews on the technology are Soria and Villamiel
(2010) and Chemat et al. (2010).
Different bacteria exhibit different sensitivities to ultrasonic
treatment in different media (Wang et al. 2010). Early appli-
cations of ultrasound showed relatively low microbial inactiva-
tions. However, there has been considerable progress in equip-
ment development that has resulted in increased inactivations but
typically below 5 logs. Application of ultrasound alone is not
very effective for microbial inactivation in commercial process-
ing, but the technique can be effective when used in combination
with other treatments (Raso et al. 1998). Thus, three differ-
ent techniques, namely thermosonication, manosonication, and
manothermosonication have been promoted as a result of the
synergistic actions of the different treatments on microbes (Lee
et al. 2009). Manothermosonication is an emerging technique
that combines heat and ultrasound at elevated pressure. Based
on intensity, amplitude, and time of treatment, manothermoson-
ication can be 6–30 times more effective in killing microor-
ganisms (Bacillusspecies,Sacchromyces cerevisae) compared
to thermal treatment given at same temperature. Different en-
zymes such as POX, lipase, lipoxygenase, protease, and pectin
methylesterase have been tested for inactivation by manother-
mosonication (Demirdoven and Baysal 2009). Manothermoson-
ication has been used to enhance the textural and functional
properties of tomato juice and milk proteins (Lopez and Bur-
gos 1995, Vercet et al. 2002). Ultrasound has also been used
in combination with chlorine, and a strong bactericidal effect
was observed (Blume and Neis 2005). Chlorine dioxide, when
used with heat and ultrasound, destroyedSalmonellaandE. coli
cells in alfalfa seeds (Scouten and Beuchat 2002). The full po-
tentials of ultrasound in food processing have yet to be tapped.
There will continue to be progress made on design of improved
and efficient equipment. Better understanding of the effect of
the process on technological and functional properties will be
crucial in identifying niche applications of the technology.UV IrradiationThe nonionizing UV radiation in the wavelength range of
100–400 nm is widely used in food processing. The electro-
magnetic spectrum is classified into three groups, namely UV-
A (315–400 nm), UV-B (280–315 nm), and UV-C (less than
280 nm). UV-C is particularly used because of its effective ger-
micidal capacity. The wavelength of 253.7 nm is known to have
the most lethal effect on microorganisms since photons are ab-
sorbed most by the DNA of microorganisms at this wavelength
(Labas et al. 2005). UV light can be generated from various
sources. The low pressure mercury vapor UV lamps are widely
used as reliable and low cost sources of UV light (Ngadi et al.
2003). These lamps operate at the nominal total gas pressures
of 102–103 Pa and their UV output is in the range of 0.2–
0.3 W/cm (Koutchma 2009). More recently, high intensity lamps
with enhanced potential for UV microbial inactivation are being
developed. Pulsed UV systems (PUV) have been developed and
have been shown to be more effective in inactivating bacteria. In
these systems, alternating current is stored in a capacitor and the
energy is discharged through a high-speed switch to form a pulseof intense emission of light of about 100μs durations. Some re-
cent studies have reported application of PUV light for surface
treatment of food products such as fresh-cut fruit, meats, and fish
(Woodling and Moraru 2005, Ozer and Demirci 2006, Alothman
et al. 2009, Oms-Oliu et al. 2009, Pombo et al. 2009). A prime
goal of UV application in food processing is to reduce microbial
load and achieve high-quality product with improved shelf life
while maintaining sensory attributes. Some fresh-cut fruits and
vegetables such as cantaloupe and fresh-cut melon treated with
UV light yield better quality retention, since the treatment was
effective in reducing microbial populations (Lamikanara et al.
2005, Art ́es-Hern ́andez et al. 2010). The efficiency of the treat-
ment depends on the structure of the fruit surface (Koutchma
2008). A reduction in microbial load was observed in juices
from apple, guava, pineapple, and orange when treated with UV
radiation (Keyser et al. 2008). Application of UV at 24 mW/cm^2
on apples inoculated withSalmonellaandE. coliO157:H7 re-
sulted in 3.3 log reduction (Yaun et al. 2004). In order to achieve
high microbial inactivation, UV light should be applied for a suf-
ficient time. Combination of UV and other minimal processing
technologies can be used to improve microbial inactivation effi-
ciency. Using modified atmosphere packaging (MAP; high con-
centrations of carbon dioxide) and UV together significantly re-
duced microbial population (Artes et al. 2009). Apart from anti- ́
microbial action, UV may also influence the antioxidant activity
of fresh-cut fruits and vegetables. An increase in the total phe-
nol contents of fresh-cut tropical fruits such as banana and guava
(Alothman et al. 2009), and enhanced flavonoid and antioxidant
levels were observed in blueberries (Perkins-Veazie et al. 2008,
Wang et al. 2009c) when the products were treated with UV ir-
radiation. Gomez et al. (2010) reported changes in the color and
mechanical compression behavior of apple cuts exposed to UV
irradiation. Treated cuts showed accelerated browning, which
the authors attributed to breakage of cellular membranes (plas-
malemma and tonoplast). The phenomenon was also used to
explain decrease in rupture stress and deformability indices for
UV-treated samples during storage. This observation is curious
as the action of UV on biological cells is traditionally attributed
to changes in DNA modification. Pretreatment of apple cuts
blanching or dipping in anti-browning solution were reported as
effective in reducing quality changes and maintaining the origi-
nal color of apple slices after UV treatment. Thus, the influence
of UV on biological cells may be more complicated as previ-
ously thought. Improved understanding of the effect may open
doors to innovative application of the technology.Other TechniquesVarious other novel techniques, photochemical (intense light
pulses, etc.) and nonphotochemical processes are being used for
minimal processing of fruits and vegetables. Electrolyzed water
has been used to disinfect food surfaces. The pH of electrolyzed
water can be raised or lowered by adding hydroxyl or hydrogen
ion concentration. Decreased bacterial growth in fresh-cut cab-
bage was observed when sanitized with slightly acid electrolyzed
water (Koide et al. 2009). Neutral Electrolyzed Water (NEW)
was used to demonstrate the efficacy of NEW over Sodium