Production Practices and Quality Assessment of Food Crops. Vol. 1

EFFECT OF PREHARVEST FACTORS ON THE QUALITY
OF VEGETABLES PRODUCED IN THE TROPICS
Vegetables: Growing Environment and the Quality of Produce
RUFARO M. MADAKADZE
Department of Crop Science, University of Zimbabwe, P.O. Box MP 167, Mount Pleasant, Harare,
Zimbabwe
JUDITH KWARAMBA
Department of Agricultural, Research and Extension Services, P.O. Box CY639, Harare, Zimbabwe
1. INTRODUCTION
Vegetables are plants whose parts are consumed in relatively small quantities as a
side dish or relish with the staple food or as a snack. They are mainly cultivated,
but some are collected from the wild. They form an important part of food supply
in all countries and contribute to balanced nutrition, health, stability and productivity.
Vegetables including roots and tubers occupy less than 10% of the whole
area under cultivation for all crops in the world (Yamaguchi, 1983). Consumption
of vegetables is correlated with per capita income, countries with low and middle
incomes use more grain products (beans, peas, cowpeas and maize) or starchy root
crops (sweet potato and cassava) in their diets compared to countries with higher
per capita income. The demand for vegetables results in an increase in incomes,
effecting better incomes for progressive farmers. Vegetables are important as sources
of different mineral nutrients and for food security from household level to national
concerns. A proper balance of human nutrition can be obtained from vegetables
alone. Vegetables can provide the following nutrients carbohydrates e.g. Irish potato,
sweet potato, cassava, dry beans and yams, oils e.g. legume seeds and mature
vegetable seeds such as Brassica napus proteins and amino acids e.g. beans, peas,
sweet corn, leafy green vegetables, vitamin A e.g. most yellow or orange coloured
vegetables such as sweet potato, squash, peppers and green leafy vegetables, green
beans and peas, vitamin C e.g. crucifers, peppers, tomatoes, most leafy vegetables
and bean sprouts and minerals e.g. most leafy vegetables and root crops.
Generally, among horticulturists quality is often expressed only in quantitative
terms, like yield and size. Postharvest quality changes are measured only as the
percent of waste (Martens and Baardseth, 1987). Kramer and Twiggs (1970) defined
quality as the composite of attributes that differentiate among units of a product
and have significance in determining the degree of acceptability of the unit by the
buyer. The quality of a product may be expressed by means of quality criteria
which includes nutritional properties (vitamins, proteins, carbohydrates), hygienic
properties (microbiological condition, content of toxic components) technological
properties (appearance flavour, texture). There is a need for measurement methods
(ranging from advanced instrumental techniques to sensory analysis) and establishment
of specifications (with tolerance limits) referring to standards or grades
R. Dris and S. M. Jain (eds.), Production Practices and Quality Assessment of Food Crops,
Vol. 1, “Preharvest Practice”, pp. 1–36.
© 2004 Kluwer Academic Publishers. Printed in the Netherlands.
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