Another consideration for fruits and vegetables is that prior to har-
vest during growth and development product quality is built up whereas
storage and handling inevitably lead to quality loss. This means that dif-
fering concepts have to be applied. During growth, knowledge about the
relationships between agronomical conditions, cultivar and harvest is
critical to achieve a good shelf life during storage and handling for fresh
products. An example comes from the flavonoids, a group of secondary
plant metabolites that occur in a large variety of fruits and vegetables.
From a quality perspective the presence of several representatives of this
group is of great importance. In apples, for example, they are responsi-
ble for color formation (anthocyanins). At the same time they influence
the flavor of the products (catechins) and are of great interest for their
capacity to act as an antioxidant (flavonols). The biosynthesis process,
and as a consequence the levels of the various flavonoids, is dependent
on a large number of factors such as cultivar differences, agronomic and
storage conditions and conditions in the retail market. To enable the con-
trol of desired levels of specific flavonoids, fast and objective analyti-
cal measurement systems are required. Quality loss is inevitable because
harvesting imposes stress and the postharvest conditions are vital for
maintenance of good end-product quality. Fruit and vegetables are liv-
ing organisms that respire and are metabolically active. The composi-
tion and structure of the primary product and the associated handling
properties are strongly dependent upon metabolic processes. For a chain-
oriented system of quality control, reliable methods are needed that can
measure external and internal quality and predict shelf life.
Also, methods that can relate raw material composition and end-
product quality to the processing conditions are necessary (Jongen,
1996). An excellent example comes from the recent work of van Kooten
et al. (1997) on cucumber. Using the efficiency of the photosynthesis
system as a parameter, they have developed a measurement system that
can be used to measure temperature failure during storage and predict
shelf life in the chain.
Cycles of Change
The market for food products of plant origin has become increasingly
competitive and changing consumer demands have provided incentives
for companies to innovate. One example comes from the National Food
Surveillance study that was carried out in the Netherlands (Anon.). In
the last decade the growing awareness of consumers about health-related