Novel Processing Technologies for Fruits - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 84

fruits have been studied. Birla et al. (2008) measured DPs
of constitutional parts of the selected fruits (orange, grape-
fruit, and peach) intended for RF heating in a water-filled
container equipped with a mechanism to keep fruits rotating
and moving during RF heating (27.12 MHz, 12 kW parallel
plate RF unit). Results indicated that dissimilarity in peel
and pulp DPs greatly influenced the RF heating behavior
of the fruits. Core heating was prominent in peeled orange
and grapefruit, whereas subsurface/peripheral heating was
prominent in whole oranges and grapefruit.
Sosa-Morales et al. (2009) reported DPs of mangoes us-
ing an open-ended coaxial-line probe with an impedance
analyzer in the frequency range of 1-1,800 MHz. DP val-
ues decreased with increasing frequency, but this reduction
was larger for the loss factor (

was observed due to RF heating. The results provided the
evidence that the RF process inactivates bacteria in orange
juice at moderately low temperatures.

OTHER NOVEL TECHNOLOGIES
FOR FRUIT PROCESSING
Before discussing some of the other novel technologies, it
is worth mentioning that the use of some of the technologies
such as radiation for food processing or packaging may not
be allowed in some countries. It is highly advisable to check
with the local regulatory agencies before considering any
applications. For instance, the FDA (2005) is responsible
for regulating the use of irradiation in the treatment of food
and food packaging in the United States and in the countries
exporting there. This authority derives from the 1958 Food
Additives Amendment to the Federal Food, Drug, and Cos-
metic Act (FD&C Act), where Congress explicitly defined
a source of radiation as a food additive (Section 201[s] of
the FD&C Act). The 1958 Food Additives Amendment also
provides that a food is adulterated (i.e., it cannot be mar-
keted legally) if it has been irradiated, unless the irradiation
is carried out in conformity with a regulation prescribing
safe conditions of use (Section 403[a][7] of the FD&C Act).
Thus the FDA regulates the lawful use of irradiation through
the food additive petition process, the completion of which
results in the promulgation of a regulation published in the
Federal Register prescribing the approved use.
The US regulations are covering the scientific back-
ground about the risks by using these technologies in
food processing. The US Code of Federal Regulations
(CFR)—21 CFR 179—is the primary regulation that covers
irradiation in the production, processing, and handling of
food, and it is divided into subparts and sections as shown
in Table 5.8. Subpart B describes radiation and radiation
sources, which include gamma ray, e-beam and X-ray, as

ε ) than for the dielectric

ε ). Loss factor increased but dielectric constant
decreased with increasing temperature. Both

constant (

ε val-
ues decreased with storage time, caused mainly by reduced
moisture content and increased pH. It was observed that RF
energy has a six times higher penetration depth in mangoes
compared to MW energy at 1800 MHz at 20 ◦ C. DP mea-
surements of mangoes in storage can be useful in selecting
the optimal ripening stage at which dielectric heating is
suited for postharvest pest control.
RF heating (80 kW heater) has been used for pasteuriza-
tion of orange juice at flow rates of 1.0 and 1.4 liter/min
(Geveke and Brunkhorst, 2004). E. coli K12 in orange juice
was exposed to electric field strengths of 15 and 20 kV/cm
at frequencies of 21, 30, and 40 kHz. Processing at an outlet
temperature of 65 ◦ C reduced the population of E. coli by
3.3 log relative to the control. Increasing the treatment time
and temperature and decreasing the frequency enhanced
the level of inactivation. Varying the electric field strength
over the range of conditions used had no effect on the in-
activation. No loss in ascorbic acid or enzymatic browning

ε and

Table 5.8. Sections under 21 CFR part 179 (USA): Irradiation in the production, processing, and
handling of food. 1

179.21 Sources of radiation used for inspection of food, for inspection of packaged food, and for

controlling food processing

179.25 General provisions for food irradiation

179.26 Ionizing radiation for the treatment of food

179.3 Radiofrequency radiation for the heating of food, including microwave frequencies

179.39 Ultraviolet radiation for the processing and treatment of food

179.41 Pulsed light for the treatment of food

179.45 Packaging materials for use during the irradiation of prepackaged foods

1 Subpart B includes 21 CFR 179.26(b), which lists foods currently permitted to be irradiated, as shown in Table 5.8.
Irradiated food should be adequately labeled under the general labeling requirements in 21 CFR 179.26(c).