Novel Processing Technologies for Fruits - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 87

mechanical vibrations, which propagate through solids, liq-
uids, or gases with a frequency greater than the upper limit
of human hearing. Although this limit can vary from person
to person, the ultrasonic frequency range is considered to
be at frequencies over 20 kHz (Salazar et al., 2010). The
upper limit of the frequency range of ultrasound is mainly
limited by the ability to generate ultrasonic signals.
Ultrasound has been identified as a potential technology
to meet the FDA requirement of a 5 log reduction in per-
tinent micro-organisms found in fruit juices (Salleh-Mack
and Roberts, 2007). When high-power ultrasound prop-
agates in a liquid, cavitation bubbles are generated due to
pressure changes. These microbubbles collapse violently in
the succeeding compression cycles of a propagated sonic
wave. Ultrasound has been studied for microbial inactiva-
tion in fruit juices including orange juice (Valero et al.,
2007) and guava juice (Cheng et al., 2007). Zang (2004)
studied the inactivation of PME in orange juice and ad-
vocated the development of an ultrasound-assisted orange
juice process.
The influence of ultrasound and conventional heating un-
der different processing conditions on the inactivation and
potential subsequent growth of micro-organisms in orange
juice was investigated by Valero et al. (2007). A limited
level of microbial inactivation (

quantities of ozone and short contact times are sufficient for
the desired antimicrobial effect and it rapidly decomposes
into oxygen, leaving no toxic residues (Muthukumarapan
et al., 2000). Excess ozone autodecomposes rapidly to pro-
duce oxygen and thus it leaves no residues in food. Such
advantages make ozone attractive to the food industry and
consequently it has been declared as generally recognized
as safe (GRAS) for use in food processing by the FDA in
1997 (Graham, 1997).
Effects of ozone processing variables (gas flow rate
[0-0.25 L min − 1 ], ozone concentration [0.6-10.0% w/w],
and treatment time [0-10 min]) on orange juice quality
parameters were studied by Tiwari et al. (2008b). No sig-
nificant changes in pH,

◦ Brix, TA, cloud value, and NEB

.05) were found. L ∗ , a ∗ ,and b ∗ color values were af-
fected significantly by gas flow rate, ozone concentration,
and treatment time.

( p <

Dense-phase carbon dioxide
Dense-phase carbon dioxide (DP-CO 2 ) treatment is a
promising nonthermal processing method that may radi-
cally change liquid food preservation technology. In recent
years, many studies have reported innovations in the use of
DP-CO 2 to preserve liquid food. Chen et al. (2009) studied
the influence DP-CO 2 pasteurization on physicochemical
properties and flavor compounds in melon juice and com-
pared with HTST pasteurization. The DP-CO 2 treatment
was carried out using a DP-CO 2 unit (55 ◦ C, 60 min, and
35 MPa). Results indicated that there was no significant
loss of β -carotene in the DP-CO 2 -treated melon juice com-
pared to the initial fresh melon juice. There was no change
in ester composition (ethyl acetate, ethyl propanoate, ethyl
butyrate, butyl acetate, and ethyl-2-methyl butyrate) after
DP-CO 2 treatment. There were slight changes in alcohols
and aldehydes, such as (Z)-nonel-3-ol, (E, Z)-2,6-nonadien,
(Z)-nonel-6-ol, nonanol, hexanal, (Z)-6-nonenal, nonanal,
and 2-nonenal. The flavor of DP-CO 2 -treated melon juice
was similar to fresh melon juice.

1.08 log CFU/ml) was
achieved by selected batch ultrasonic treatment (500 kHz/
240 W for 15 min). However, microbial growth was ob-
served in the substrate following 14 days of storage at 5 ◦
and 12 ◦ C. The presence of pulp in the juice increased the
resistance of micro-organisms to ultrasound. After contin-
uous ultrasonic treatments at flow rates of 3,000 liter/hr,
negligible reductions of microbial counts were obtained.
No ultrasound-related detrimental effects on the quality
attributes of juice (limonin content, brown pigments, and
color) were found. Therefore, a combination of ultrasound
with other processing methods is required to prevent the
development of food-borne pathogens in orange juice.
Tiwari et al. (2008a) studied the effect of ultrasonic in-
tensity (UI) levels (8.61-22.79 W/cm 2 ) and treatment times
(0-10 min) on quality parameters (pH, ◦ Brix, titratable
acidity [TA], cloud, browning index, and color parameters
[ L ∗ , a ∗ ,and b ∗ ]) of freshly squeezed orange juice samples.
No significant changes in pH, ◦ Brix, or TA were found.
Cloud value, browning index, and color parameters were
significantly affected by UI and treatment time.

≤

CONCLUSION
Thermally processed food occupies major market share for
more than a century due to convenience and availability
throughout the year. Usually, the inactivation of micro-
organisms in food is ensured by thermal treatment (pasteur-
ization or sterilization), however, heat-induced changes to
flavor and taste, color, and nutrients are noteworthy. Re-
cently, there has been an increasing consumer demand for
additive-free fresh-like food products. The food industry
has responded by applying a number of new technolo-
gies (termed as novel or emerging technologies) to replace

Ozone treatment
Ozone has a wide antimicrobial spectrum, which, com-
bined with a high oxidation potential, makes it an attractive
processing option for the food industry. Relatively small