238 Produce Degradation: Reaction Pathways and their Prevention
of processing for the fresh market. For example, peas, corn, and green beans should
have attained full size but still be tender, whereas mature potatoes are more desirable
than those less mature (Salunkhe et al., 1991). Small cabbage heads are higher in
ascorbic acid than large ones (Salunkhe et al., 1991). Small turnip leaves have
relatively more thiamin and riboflavin content than ascorbic acid but less carotene
than large leaves. In general, broccoli, cabbage, and cauliflower have the maximum
content of nutritive value at the harvest time. It is exceedingly important that veg-
etables in general, and crucifers in particular, be harvested at the proper stage of
maturity. Early-maturing fruits and vegetables usually have a shorter storage life
(Salunkhe and Kadam, 1998). The exact degree of maturity at which a given cultivar
of a species should be harvested also depends on the purpose for which it is used.
Fruits and vegetables harvested for the local fresh market must be harvested at
prime maturity. When harvested for shipping or processing, they should be harvested
a little earlier, for example, a week. However, if harvested too early and then stored
for a long time, they may shrivel and the characteristic aroma will disappear, and if
they are harvested too late and then stored for a longer period, they might have
higher-than-average concentrations of sulfur compounds and low ascorbic acid and
other water-soluble vitamins (Salunkhe and Kadam, 1998).
8.7.2 STORAGE CONDITIONS
8.7.2.1 Temperature and Relative Humidity
Temperature and humidity are the most important storage parameters that influence
the nutritional quality of both fruits and vegetables. Most fruits and vegetables are
exposed to unfavorable temperatures during the handling chain from harvest to the
wholesalers and retailers. Fresh fruits and vegetables probably receive the greatest
temperature abuse by retailers and consumers (Table 8.3). Temperature abuse is a
function of time and temperature during holding and the relative perishability of a
particular commodity. Some produce, for example, apples and cabbages, are often
displayed at improper temperatures in retail stores, but they do not lose quality as
rapidly as others such as strawberries and broccoli (Paull, 1999).
TABLE 8.3
Percentage of Fresh Fruits and Vegetables in Supermarket Display Cases Held
at Their Optimum Temperature Range During the Summer
Percentage
Sample Commodities Below Range Within Range Above Range
Apples, lettuce, cabbages 0 7 93
Mandarins, snap beans, summer squash 11 37 52
Winter squash, peppers 41 48 11
Sweet potatoes, bananas, green tomatoes 67 33 0
Source:Adapted from Paull, R.E. (1999), Postharv. Biol. Technol., 15:263277.