weighted according to the requirements of the different customer groups
(consumer, trade, retail and industry). Weighting factors for each group
of product attributes can be determined by estimations of an expert panel
(van Kooten and Peppelenbos, 1993; Molnar, 1996) or by surveys of
each customer group, e.g., consumer surveys (Schonhof et al., 1997;
Lennernäs et al., 1997). Further attribute groups might be included, e.g.,
extrinsic attributes. If the threshold value for undesirable attributes is
exceeded, the product will have no market capability (Schreiner et al.,
1996).
At present, quality attributes of harvested plant products that are es-
tablished in official quality standards—like those of the European Com-
munity or the USDA Standards—are based on the Codex Alimentarius
of the Food and Agriculture Organization of the United Nations (FAO)
and the World Health Organization (WHO). In these official standards
product quality is primarily based on a subjective assessment of only
external product attributes, e.g., whole, firm, clean and fresh in ap-
pearence. However, in response to consumer demand there is an in-
creased emphasis on internal product quality, e.g., flavor and health
benefits. With increasing health consciousness, additional laws and reg-
ulations are being established to reduce undesirable and toxic product
attributes (e.g., nitrate). More recently the bioactive substances like glu-
cosinolates, carotenoids, polyphenols, saponins, and different fractions
of dietary fibers are generating interest (Figure 5.1) (Schonhof and
Krumbein, 1996, 1997; Schreiner et al., 1998). Changes in consumer
awareness of health, nutritional, and ecological aspects product quality
lead to continual change in the market place. Thus quality cannot be
considered fixed but is dependent on consumer perception and time.
EFFECT OF PREHARVEST CLIMATIC CONDITIONS
ON BIOACTIVE SUBSTANCES
Due to the health-promoting effect of carotenoids, the influence of air
temperature and photosynthetic photon flux density (PPFD) during the
production period on the content of -carotene and lutein has been in-
vestigated. The content of -carotene is dependent on the daily mean
temperature, e.g., broccoli cultivar ‘Emperor’ (Figure 5.2).
Daily mean temperatures below 16.5°C led to an obviously higher -
carotene concentration as daily mean temperatures above this tempera-
ture level decrease -carotene. The PPFD had no effect on the -carotene
or lutein content in broccoli (Figure 5.3).
Effect of Preharvest Climatic Conditions on Bioactive Substances 87