are, either at low temperature (no chilling injury, see 5 and 10°C in Fig-
ure 7.7) or near the optimal temperature (chilling injury), the larger the
effect of temperature becomes, due to the sum of rates in the denomi-
nator of Equation (7.5). This effect partly explains the difficulties en-
countered in practical conversion of keeping quality rules of thumb from
one country to another.
Effects of Initial Conditions and Harvest Time
Lange and Cameron (1994) studied the effect of diurnal harvest time
on the keeping quality of sweet basil. Analysis of the data revealed that
the diurnal harvest time only affects the initial quality Q 0 , without af-
fecting the reaction rate constants. The initial quality could be described
by a sinusoidal function, linked to the rise and fall of the sun during a
day’s period. Increasing the initial quality greatly increased the keeping
quality and consequently the acceptability of the product. Again, as for
the potted plants, acceptability can be increased by increasing the initial
intrinsic quality of the product without losing the consumer’s confidence
in the product by playing too close to the acceptability limit.
Variance in Batches
Every batch of products consists of individuals. Despite the apparent
identical stage of maturity, (external) quality and appearance, all these
individuals are actually at different stages of maturity. The number of
individuals in a batch that have to be acceptable for the entire batch to
be acceptable (batch quality limit) depends on the preferences of the
user(s) and the intended application. The first individuals in a batch that
become unacceptable determine the acceptability of that batch. Inher-
ently that is those individuals that are more developed/mature to begin
with. This fact puts a large emphasis on the type of distribution of the
quality attribute in a batch of products with apparently an identical state
of maturity.
With the recently developed very accurate techniques of quality mea-
surements, especially computer imaging techniques for measuring color
and color models similar to the model for the potted plants (see Equa-
tion [7.1]), it has become within reach to study the distribution of color
in a batch of products. Schouten and van Kooten (1998) reported on the
type and change of the distribution of color in batches of cucumbers.
They found that the distribution of color over the individuals in a batch