Kiwifruit - Tropical and Subtropical Fruits: Postharvest Physiology, Processing and Packaging - page 471

Kiwifruit ( A. deliciosa ) has chlorophyll content of
1.8-2.26 mg/100 fresh weight (Cano et al., 1993b), but
lower values have been reported for the 'Hayward' cultivar
from New Zealand (Celik et al., 2007). The total chloro-
phyll content in the green-fleshed 'Hayward' is 3-4 times
higher than of yellow-fleshed 'Golden King' (Watanabe and
Takahashi, 1999). The color of fresh-cut kiwifruit changes
from bright green to dull brown/olive green due to the for-
mation of pheophytins and pyropheophytins during stor-
age or heat treatment (Cano and Marın, 1992). Kiwifruit
products also undergo nonenzymatic browning due to
Maillard browning reactions and ascorbic acid brown-
ing reactions. Color changes are more deleterious when
the storage time is prolonged and the storage temper-
ature increases. The quality changes of minimally pro-
cessed kiwifruit slices are lessened using vacuum impreg-
nation combined with sucrose, potassium sorbate, ascorbic
and citric acids, and zinc chloride (Leunda et al., 2000)
and calcium and/or copper chlorides (Vial et al., 1991).
However, these treatments can result in 70-90% degra-
dation of chlorophyll in minimally processed kiwifruit
slices (Leunda et al., 2000). Hence color deterioration is
not only due to chlorophyll breakdown but also due to
other ongoing complex chemical and enzymatic reaction
mechanisms.

(McMath et al., 1991) but SSC between 13% and 16% is
equally preferred. Consumers like ripe kiwifruits with SSC
ranging from 11.6% to 13.5%, but 12.5% SSC has been
proposed as a minimum quality index for early-marketed
kiwifruit (Crisosto and Crisosto, 2001). The acidity of ki-
wifruit can play a significant role in consumer acceptance
when kiwifruit have ripening SSC < 11.6% combined with
acidity > 1.17% (Crisosto and Crisosto, 2001). Astringency
and bitterness can develop during storage, and the devel-
opment of off flavors is greatly influenced by the storage
temperature, time, and the degree of maturity and pre- and
postharvest treatments. Storage at 4 ◦ and 10 ◦ C can lead
to an increase in stalky, woody flavors compared to stor-
age at 0 ◦ C (Marsh et al., 2004). Bitter taste can be devel-
oped in fresh-cut kiwifruits after 4 days of storage at 4 ◦ C
(O'Connor-Shaw et al., 1994), and the flavor was poorly
received after 7 days.

Safety
The safety of a product needs to address several aspects
including intrinsic health hazards (e.g., chemical residues
and heavy metals, allergens, antinutrients) and extrinsic
hazards (e.g., microbial contamination and the formation
of organic compounds during storage). Both microbial and
allergic effects of kiwifruits have been investigated (Roller
and Seedhar, 2002; Lucas et al., 2004) but information
on other potential safety concerns still lacks in literature.
Proper sanitation and handling procedures (use of hydrogen
peroxide or sodium hypochlorite rinse before processing)
can reduce the surface microbial numbers and reduce the
potential risk of contaminations.
Edible coatings represent a good carrier for antimicro-
bial compounds to control microbial growth. Several other
interventions such as the application of citric acid (Senesi
and Pastine, 1996), carvacrol and cinnamic acid (Roller
and Seedhar, 2002), natural aroma compounds (e.g., hex-
anal), and citrus, mandarin, cider, lemon, and lime essen-
tial oils (Lanciotti et al., 2004) to inhibit microbial growth
in kiwifruit have been reported with various degrees of
success.

Te x t u r e
Firmness is the mean texture characteristic desired in mini-
mally processed kiwifruit products. Kiwifruit slices soften
during storage. About 12%, 50%, 62%, and 75% of the
firmness are lost after 3 days of storage at 0 ◦ ,5 ◦ ,10 ◦ ,
and 20 ◦ C, respectively (Agar et al., 1999). This softening
could be delayed by the use of calcium application (1-2%,
depending on the salt used) in combination with ethylene
scrubbing. For example, the shelf life of kiwifruit slices is
more than double under a combination of calcium chloride
dips and storage at 1 ◦ C under gas composition of 2% O 2
and 5% CO 2 with an ethylene scrubber (Agar et al., 1999).
Mild heat pretreatments ( 45 ◦ Cfor 25 min) improve

the firmness of kiwifruit slices when applied to firm-ripe
kiwifruits (Beirao-da-Costa et al., 2006). The application of
1-methylcyclopropene (1-MCP) prior to cutting can reduce
wound responses and delaying ripening in cut kiwifruits
(Mao et al., 2007).

< <

PROCESSING AND PROCESSED PRODUCTS
Kiwifruit processing is carried out to utilize any surplus of
the market requirements, add the value, and utilize fruits
that do not meet export criteria. Therefore safe and sta-
ble products can be obtained and the uniqueness of the
fresh fruit as much as possible, its natural green color,
aroma, nutritional value, and structural characteristics can
be retained (Gianotti et al., 2001). However, processing

Flavor
The perception of flavor by consumers is a decision nor-
mally based on combined different taste and aroma com-
ponents (Kader, 2002). The acceptability of kiwifruits
is compromised at soluble sugar content (SSC) < 13%