resulting in a nonvisual external quality loss. Leafy vegetables or veg-
etables purchased with leaves are characterized by a locally differenti-
ated wilting behavior in postharvest. Bunched carrots and small radishes
show their first wilting symptoms on the leaves. For assessing product-
specific thresholds of bunched carrots and small radishes, the critical
water loss was determined by the shift from turgidity to the appearance
of slight wilting symptoms on the leaves. The maximum permissible
water loss is 4% for bunched carrots and 5% for small radishes (Kays,
1991). By knowing the maximum acceptable water loss of bunched car-
rots and small radishes and knowing the postharvest storage conditions,
it is possible to predict the time unit for shelf life. The product-specific
threshold represents the end of market life. This process is shown in the
Figure 5.7 using bunched carrots as an illustration. The relative air hu-
midity was held to be constant at 80%, while the air temperature varied
from 0°C to 25°C. In this case the specific product threshold was de-
fined by the critical water content (86%), because the entire relative
water concentration of harvested carrots with leaves was 90%. It is ob-
vious from this example that in the case of 25°C air temperature, the
threshold was reached in four hours. In contrast air temperature of 5°C
caused an shelf-life extension of about 16 hours.
Effect of Postharvest Storage Conditions on Shelf Life 93FIGURE 5.7Shelf-life prediction for carrots.