70 Produce Degradation: Reaction Pathways and their Prevention
of fresh-cut products, and so it is likely the pears to be used for slicing should be
selected at a less ripe stage to ensure that browning and softening are adequately
controlled, knowing that the flavor of the product may be sacrificed as a result.
Alternately, processors may achieve a significant market advantage, in terms of
flavor, if they can learn how to ensure low handling/display temperatures during
distribution and marketing.
Maturity testing, using an index based on color patterns on bisected apples, in
response to an iodine-potassium iodide solution, has been well developed for eval-
uating apples for harvest and long-term storage (Smith et al., 1979). In some cases
total starch is not well estimated by a starch-iodine test, depending on the apple
cultivar and year; however, this is not considered to be a serious problem (Fan et
al., 1995). Lau (1985) discusses the complexity of processes that change during
maturity and ripening in apples, including changes in starch content, ethylene pro-
duction, firmness, soluble solids, skin and flesh color, and titratable acidity. However,
in practice, it is difficult to incorporate all of these measures into an easily used tool
for deciding to harvest a particular orchard at a point in time. This practical limitation
might be circumvented by sampling orchards within a growing region, allowing
economical determination of multiple harvest predictors (Silsby, 1993). Improve-
ments in technologies might provide more streamlined approaches to monitoring
maturity and ripening. Advances in VIS/NIR-spectroscopy offer the potential of
being able to optimize harvest dates based on starch, soluble solids, titratable acidity,
and firmness determined simultaneously (Peirs et al., 2000), and this may lead to
an ability to improve poststorage quality over that obtained using the current starch-
iodine test done in parallel with ethylene measurements (which is used as an indicator
for softening potential in storage).
In stone fruit (nectarines and peaches), harvest maturity has generally been
determined through subjective determination of exterior fruit color (Lavilla et al.,
2002). However, this can be difficult in cultivars that show little color change during
maturation and ripening. Fruit are harvested at the mature, but not ripe, stage, defined
as the “well-mature stage.” At this stage external ethylene application is not required
to induce ripening. Ethylene is not useful as an indicator since climacteric ethylene
production occurs in parallel with softening and so the fruit would already be too
soft if harvested based on ethylene production (Tonutti et al., 1997). Lavilla et al.
(2002) suggest that measurement of the characteristic aroma volatiles of peaches or
nectarines could provide maturity indices, allowing the harvest of these fruits at a
well-mature stage in a condition that ensures the least amount of injury during
transport and marketing and that the fruit can ripen to produce a high-quality product
for the consumer.
Another aspect that requires further study is that of mathematical modeling to
predict optimal harvest dates. Hertog (2002) has pointed out that the variability of
any specific population must be understood with respect to postharvest behavior
since this variability will profoundly influence perceived fruit quality. It is not only
important to understand the average quality change of, say, a population of fruit in
a transport container, but it is also important to understand the extreme quality
differences in that population. Therefore, models can be useful only if they can
capture such variation. In addition, use of models may stimulate research to reduce