Agriculture Reference
In-Depth Information
14.4.5 Physicochemical treatments
Inhibition of physiological and/or pathological deterioration of fresh harvested produce by
a combination of any type of physical, chemical, or environment-friendly chemical methods
is called “physicochemical” treatments.
During fruit ripening on the tree and after harvest, some essential processes involve
the production of the anaerobic metabolites, acetaldehyde, and ethanol. These processes
include the production of aroma volatiles and removal of fruit astringency. A requirement
for anaerobic metabolites in normal ripening provided the initial indication that the appli-
cation of such anaerobic metabolites might be beneficial for postharvest fruit quality. In the
postharvest period, anaerobic metabolites may be applied to induce volatile production and
to improve fruit aroma (Pesis, 2005). “Murcott” mandarins held in N
2
exhibited a higher and
an earlier increase in the accumulation of the off-flavor volatiles than “Star Ruby” grape-
fruit (Shi et al., 2005). Finally, sensory evaluations indicated that the taste of mandarins
markedly deteriorated following exposure to anaerobic conditions and was rated as unac-
ceptable after 48 h in N
2
, whereas the taste of grapefruit deteriorated only slightly and was
rated acceptable even after 72 h of exposure to N
2
(Shi et al., 2005). Fallik et al. (2005a)
found that anoxia-treated tomatoes that were held at 20
◦
C for 12 days had organoleptic
qualities similar to those of untreated fruit that were held at cold storage plus marketing
simulation, and the trained panel preferred the N
2
-treated fruit. Pressure infiltration of ap-
ples with CaCl
2
solutions transiently inhibited volatile levels by forming a temporary barrier
to CO
2
and O
2
exchange between the fruit tissue and the surrounding atmosphere (Saftner
et al., 1999). Hypobaric (low pressure) storage offers considerable potential as a method
to prevent postharvest loss of horticultural and other perishable commodities, such as fruit,
vegetables, and cut flowers. The effects of hypobaric storage on the biological characteris-
tics of green asparagus were compared against refrigeration and room temperature storage.
Hypobaric storage maintained sensory quality and delayed the postharvest senescence pro-
cess of asparagus (Li et al., 2006). Ozone is a disinfectant that can be applied by direct
contact or by indirect contact through washing the produce with recycled water containing
ozone. Ozone is a powerful oxidant that acts on carbon residues dissolved in the washing
water, as well as on the produce surface. A detrimental effect of ozone treatment (0.35 ppm
at 2
◦
C) on strawberry aroma was observed, with a 40% reduced emission of volatile esters
in ozonated fruits (Perez et al., 1999). The effect of ozone on sensorial quality of whole and
fresh-cut tomatoes stored up to 15 days at 5
◦
C was examined. In whole and sliced tomatoes
treated with a humidified flow of ozone-enriched air applied cyclically (4 ppm of O
3
), a
higher sugar (fructose and glucose) and organic acid (ascorbic and fumaric) content was
found (Aguayo et al., 2006). The O
3
-treated fruit retained a good appearance and overall
quality in slices, but had a reduced aroma. Ozone did not cause any damage or off-flavor in
slices or whole tomatoes. In a different experiment, tomatoes were vacuum infiltrated at the
breaker stage with ethanol (EtOH) vapor and then held for a further period before ripening
in air at 22
◦
C. Aroma or flavors were not altered as determined by a trained taste panel,
except in extreme conditions, where in some cases off-flavors increased (Ratanachinakorn
et al., 1999). Strawberries treated with methyl jasmonate (MJ) in conjunction with ethanol
(MJ-ETOH) increased volatile compounds during storage period compared to control or
fruit treated with ethanol alone. The postharvest life was longer for those berries treated
with MJ-ETOH and MJ than for those treated with ethanol or control fruit (Ayala-Zavala
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