Maturity, Ripening, and Quality Relationships 69
A third challenge is that of carrots, in which changes relating to storage ability
are reached after the crop has reached a stage of maximal yield (Fritz and Weich-
mann, 1979). In this case, as the ratio between monosaccharides and sucrose content
increases, the storage potential increases. This change has been posited as a means
of monitoring “ripening” in carrots. However, it is a gradual process and difficult to
monitor without expensive equipment, so carrot size is generally used as the harvest
criterion for storage (Salunkhe and Desai, 1984).
3.4.2 CLIMACTERIC FRUITS
Climacteric respiratory behavior occurs only in certain fruits (Saltveit, 2002) and is
characterized by a sharp, transient rise in respiration and ethylene evolution during
ripening (see Figure 3.3). This dramatic transient rise implies a rapid change over
a short period of time, which is another characteristic of climacteric fruit: they exhibit
exponentially increasing ethylene production rates associated with rapid softening,
increases in sugar, reduction of acid content, and increased aroma volatile production
(Abeles et al., 1992; Saltveit, 1999). Often, development of controlled atmosphere
and modified atmosphere technologies has focused on inhibiting the climacteric
ripening process.
Climacteric ripening fruits are much easier to predict for harvest since a climacteric
respiratory pattern is a sharp and easily discerned process, and senescence sets in quickly
once the optimal ripeness has passed (Figure 3.3). In addition, there are several easily
measured criteria that can be used to substantiate changes in ripeness (i.e., quality) of
the fruit. The most useful criteria for estimating ripeness stage are considered to be
ethylene evolution and respiration (Lau, 1985; Saltveit, 2002). These can be coupled
with such criteria as firmness, starch levels, skin color, and aroma volatile production
(Pantastico et al., 1975; Lau, 1985; Mattheis et al., 1991; Young et al., 1996).
3.5 QUALITY DETERIORATION MANAGEMENT
THROUGH MATURITY/RIPENESS SELECTIONMaturity and stage of ripeness have been used to manage quality in all fruits and
vegetables (Pantastico et al., 1975; Watada et al., 1984; Saltveit, 2002). Most of the
extensive literature on the topic relates to work with apples, and despite the volume
of work in that commodity, quality problems continue to persist (Toivonen, 2003).
The discussion in this section will highlight considerations that may help to improve
the quality prediction process.
End use and postharvest handling conditions have a significant influence on the
criteria used for selecting optimal maturity. As mentioned in the earlier discussion
of pears, selecting optimal maturity measured by firmness is essential to maximize
shelf life of slices made from that fruit. If slices are to be handled at low temperatures
(near 0°C), then fruit used to produce the slices can be relatively soft at a firmness
of 23 to 31 N (Chen et al., 2003). However, if the slices are to be handled at warmer
temperatures (~ 10°C), then pears that are to be sliced must have a firmness of 44 to
58 N (Gorny et al., 2000). The second temperature range is more the norm in handling