Kiwifruit - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 469

for each specific case under the applied environmental and
technological conditions.
The use of other chemicals (potassium sorbate, ascor-
bic and citric acids, erythorbate, zinc chloride, and copper
chloride) with the aid of vacuum impregnation or osmotic
dehydration (Vial et al., 1991; Leunda et al., 2000) provided
improved color retention under vacuum impregnation but
not with atmospheric impregnation. The use of reducing
agents (e.g., 1% ascorbic acid or erythorbate) affords the
ability to convert quinones, brown compounds generated
by the actions of polyphenol oxidase (PPO), back to phe-
nolic compounds, which reduce the discoloration rate. The
same outcome can be obtained by decreasing the surface
pH, which reduces PPO activity through the application of
acids (e.g., citric or ascorbic acid), which at a higher use
rate can potentially affect the flavor of the product.

Edible coatings
Edible coatings have the potential to reduce moisture loss
and soggy appearance of freshly cut fruits, regulate oxy-
gen transmission, retard ethylene production, and maintain
flavor and the ability to incorporate functional compounds
(antimicrobial agents and antioxidant) that can improve the
keeping qualities during shelf life. Available information
on the use of edible coating are reported on whole fruit as
mentioned earlier and future research would probably cover
the potential use of these material on minimally processed
kiwifruit products.

Packaging of minimally processed products
Given the importance of the atmosphere composition in
extending the shelf life of the product, a close attention
to the packaging system used with minimally processed
kiwifruit products is necessary. For example, the type
of packaging material used, its thickness, and gas trans-
mission properties (permeance to low molecular weight
compounds and the respiration activity of the packed
produce/respiration rate), temperature, amount of material
packed, headspace of package, surface area of product,
and permeability/permeability ratio. Calmshell has been
the most used in research on fresh-cut kiwifruit products
(Agar et al., 1999; Rocculi et al., 2005) and polypropylene
(Wang and Buta, 2003). Specific requirements for kiwifruit
are not available in literature, but future research is
expected to be driven toward active packaging systems,
which afford the control of microbial, nutritional, and
flavor changes in addition to the current focus on textural
changes. Isotactic polypropylene-based nanocomposite
films filled with nanoparticles of calcium carbonate may be
potentially useful for kiwifruit fresh products (Avella et al.,
2007).

Modified atmosphere
The use of volatile compounds (methyl jasmonate, ethyl
alcohol, 1-propano, and isopropyl alcohol) to maintain the
quality of fresh-cut kiwifruit was investigated by Wang
and Buta (2003). Methyl jasmonate (concentration range
2.24-22.4 μ l/liter) was the most effective compound in
delaying the development of decay in kiwifruit slices during
storage at 10 ◦ C. Methods of application affect the efficacy
of the volatile compounds with suspension of the source of
volatile compounds within the package, which yields better
results compared to volatilization of the volatile compounds
from beakers placed inside the packages. Methyl jasmonate
also maintains higher levels of sugars and organic acids
compared to the untreated slices.
Low levels of O 2 (0.25-5%) and high CO 2 concentrations
(10-20%) have been used to maintain the quality fresh-cut
kiwifruit slices (Agar et al., 1999). The use of low oxygen
and high CO 2 concentrations at low storage temperatures
reduces the respiration of the products and reduce weight
loss. Positive effects on color result due to lower concen-
tration of O 2 (required for PPO reactions) in the package,
and consequently the rate of discoloration. Attention needs
to be paid to avoid conditions that promote anaerobic fer-
mentation, which can lead to the formation of off flavors
and rapid loss of quality.
The use of other gas mixtures (90% N 2 O

Microbiological issues
Raw and minimally processed kiwifruits are characterized
by several properties that may compromise their safety. The
product is normally sold fresh to the consumer in a ready-
to-eat form without applying preservatives or antimicro-
bial substances or heat treatments. Blanching using satu-
rated water vapor at various temperatures has been reported
(Leunda et al., 2000; Llano et al., 2003). The level of acid-
ity after ripening may not be high enough to suppress bac-
terial growth. Therefore a variety of pathogenic bacteria
such as Listeria monocytogenes, Salmonella spp., Shigella
spp., Aeromonas hydrophila, Yersinia enterocolitica ,and
Staphylococcus aureus as well as some Escherichia coli
strains may be present on fresh-cut or minimally processed

+ 5% O 2 +

5% CO 2 ; 90% Ar + 5% O 2 + 5% CO 2 ; 90% N 2 O + 5%

O 2 + 5% CO 2 ) to improve the quality of kiwifruit slices in

polypropylene boxes during 12 days of storage at 4 ◦ Chave
been investigated (Rocculi et al., 2005). MA with 90% of
N 2 O exhibited the best ability to maintain the quality of
kiwifruit slices.