Kiwifruit - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 464

stored at 0 ◦ C has been rated as more sweet and less acidic
than those stored at 4 ◦ C. While cold storage at around 0 ◦ C
can effectively maintain the firmness and extends storage
life of kiwifruits, several publications reported the devel-
opment of physiological disorders (Lallu, 1997) and accel-
erated loss of the fruit firmness after cold storage (Arpaia
et al., 1987; Antunes and Sfakiotakis, 2002b).

The production of ethylene by the kiwifruit is triggered
by exposure to exogenous ethylene, mechanical injury, or
pathogen attack (Yano and Hasegawa, 1993; Sfakiotakis
et al., 1997). Therefore cold storage at 0 ◦ C, where en-
dogenous ethylene production is delayed, has been used
as an industrial practice to maintain the firmness of the
fruits during storage (Manolopoulou and Papadopoulou,
1998). However, recent research showed ethylene produc-
tion in A. deliciosa ('Hayward') at 0 ◦ C, accompanied by an
increase in Botrytis cinerea contamination (Chiaramonti
and Barboni, 2010). It is likely that the contamination
with B. cinerea rather than metabolic processes leads to
the generation of ethylene since B. cinerea can lead to
the production of a significant amount of ethylene (Qadir
et al., 1997).
The age of the fruit at harvest (number of days after polli-
nation) plays an important role in the initiation of ethylene
production and the response to propylene treatment (com-
monly used procedure to initiate the ripening process). Low
ethylene production and poor response to propylene treat-
ment have been found with the increase in the fruit maturity
(Mworia et al., 2010).
Soluble sugar content can also change (either increase or
decrease) independent of ethylene during storage as carbo-
hydrates utilized in fruit respiration (MacRae et al., 1992).
The involvement of sucrose-phosphate synthase, which is
activated by ethylene, cool storage, and the ripening pro-
cess, has been suggested (MacRae et al., 1992). Regarding
the titratable acidity in kiwifruit ('Hayward'), little change
(MacRae et al., 1989) or significant reduction (Crisosto and
Crisosto, 2001) was reported. Environmental and growing
factors probably lead to a higher initial acidity in the fruit
(kiwifruits from the Northern Hemisphere reported to have
about 2.5% acidity compared to New Zealand kiwifruit,
which has about 1.4%), which decreased subsequently on
storage, whereas the acidity of New Zealand kiwifruit re-
mained unchanged. At harvest, the organic acids contain
about 40-50% as citrate, 40-50% as quinate, and 10% as
malate (Marsh et al., 2004). The storage temperature plays
an interesting role in the metabolism of organic acids with
subsequent great effect on the sensory attributes of the fruit
(Marsh et al., 2004). For example, kiwifruit stored at 0 ◦ C
exhibited a steady decline in the proportion of citrate and no
change in the proportion of malate, whereas storage at 4 ◦ C
increased the malate concentrations (MacRae et al., 1989).
Marsh et al. (2004) have confirmed the increase of malate in
kiwifruit stored at 4 ◦ C (50-100% more malate content than
0 ◦ C stored fruits) and reported a lower decline rate in citrate
in fruits stored at 10 ◦ C. In both sensory studies, kiwifruit

Postharvest losses, causes, and remedies
Consumers expect consistent and high-quality product for
continuous purchase decisions and defects can lead to un-
marketable product, which causes financial losses. High-
quality kiwifruits should not be shriveled and should be
free of peduncle, pest, moisture sunscald, scars, growth
cracks, insect injury, bruises, internal breakdown, and decay
(UNECE, 2008). Several defects can originate before har-
vest as a result of damage by insects, diseases, birds and/or
hail, chemical injuries, and various blemishes (such as
scars, scabs, abrasions, and staining), which, if undetected
during processing, can cause more damage during posthar-
vest storage. Severe losses can be encountered by the ki-
wifruit industry for various controllable reasons (e.g., time
of harvest, handling, hygiene, and storage conditions) or the
sometimes uncontrollable conditions (insects and patho-
logical diseases, undetected injuries). The amount of losses
reported varies widely and are season and location depen-
dent; for example, in New Zealand, the industry has average
losses of 11.6% for green kiwifruit and 10.6% for the gold
variety (NZPA, 2007). Higher and lower values were re-
ported in New Zealand (Apata, 2008; NZKGI, 2010) for
different seasons and among different kiwifruit growers.
A much higher rate of disease incidence of kiwifruit rot
( A. deliciosa ) in Korea has been reported (Koh et al., 2005).
The extent of damage caused by fruit rot diseases (bacterial
canker and bacterial blossom blight) can be severe and con-
tinues during cold storage, transportation, marketing, and
retail.
Postharvest defects may result from physical, chemi-
cal/biochemical, or microbial effectors. The final outcome
of these factors is undesirable change in the sensory at-
tributes of the fruit (firmness, juiciness and mealiness, fla-
vor, aroma) that affect the product marketability and con-
sumption. Off flavors may result from the accumulation
of fermentative metabolites (acetaldehyde, ethanol, ethyl
acetate). Nutritional quality is related to the contents of vi-
tamins, minerals, dietary fiber, and phytochemicals (Rush
et al., 2002).