102 Produce Degradation: Reaction Pathways and their Prevention
from 93 to 120 μJ following a 2-day delay after harvest and from 74 to 104 μJ
occurred as a result of elevating temperature from 19 to 30°C.^227 Delay after harvest
and temperature had the opposite effect on compression damage threshold. Incidence
of tip rot increases with increasing severity of nonvisible impact damage to asparagus
spear tips. Lallu et al.^228 reported that impact on apical tissues after drops from 0,
50, 100, and 150 mm resulted in 0, 34, 36, and 64% tip rot, respectively, after 5
days at 20°C and 93 to 95% RH. Washing spears after impact increased the incidence
of tip rot. Although adverse physiological stress may be a factor involved in the
expression of tip rot, results indicated that physical damage may be a major con-
tributing factor, exploited by microorganisms present on the asparagus spears and
in packhouse wash water, leading to spoilage. Drop experiments using apricots
showed that ethylene production could be greatly affected by low temperature.^127
Ethylene was found to increase more in fruits that were impacted at 4°C and then
stored at 18°C than in fruits that were kept continuously at 18°C. Respiration was
also affected by temperature, but not as greatly as ethylene production. L (lightness)
and b (yellowness) values decreased significantly in the injured flesh compared to
the sound flesh, especially in fruit impacted at 4°C and then stored at 18°C.
The combined use of perforated polypropylene (PPP) and intermittent warming
(IW) appears to be a practical method to protect peaches from mechanical damage
due to transfer from cold to warm rooms and vice versa. In a study to determine
the effect of IW on quality of peaches cold-stored in PPP, IW slightly increased
senescence but extended shelf life, and the peaches were preferred for color and
flavor.^229 IW also allowed normal ripening and prevented wooliness. Controlled
atmosphere (CA) storage at 5 to 8% CO 2 by volume prevented the spread of Botrytis
cinerea in headed cabbages grown under extreme weather conditions, harvested by
hand or machine, and subjected to mechanical damage before cold storage (-0.5 to
0°C). Total storage losses were lower under CA storage than under normal cold
storage.^230 Temperature is the most critical factor influencing postharvest quality of
strawberries. Precooling as soon as possible after harvest and storage at low tem-
perature are considered essential for reducing the respiration rate of strawberries
and susceptibility to mechanical damage during transport. It is also recommended
that trucks with air-spring suspension be used to transport strawberries to minimize
vibrational damage.^43 The postharvest response of wild lowbush blueberries (Vac-
cinium angustifolium Ait. and V. myrtilloides Michx.) to mechanical damage and
storage temperature is mainly an increased number of shrivelled or split berries.^217
In general, the major quality attributes (firmness, microbial growth, hue, bloom,
split, and unblemished berries) deteriorate with increasing damage levels and
increasing storage temperature without significant interaction.
In a study of the effect of mechanical damage of greenhouse lettuce on some
biochemical processes occurring during storage, Leja and Mareczek^153 found that
total phenols and amino acids and enzyme activity increased during storage at either
20°C for 4 days or 5°C for 7 days. In autumn-grown lettuces, PPO and POD activities
were slightly higher in wounded lettuces than in intact ones. Free amino acid
concentrations increased in response to wounding, particularly in lettuces stored at
the higher temperature. Membrane permeability increased after wounding in lettuces
grown in autumn, and spring-grown lettuces were less sensitive to wounding than