Nutrient Loss 243
8.9 PRODUCE TREATMENT AND NUTRIENT QUALITY
8.9.1 PREHARVEST TREATMENT
Environmental conditions and agronomical treatments during the growth of the plant
influence the quality of produce. The influence of soil moisture and temperature,
fertilization, insecticides, and fungicides on the nutritional composition of fruits and
vegetables has been widely recognized (Salunkhe et al., 1991). The climate of the
crop areas, soil type, irrigation, pruning, thinning, and rootstock also exert an influ-
ence on the nutritional composition of the produce. Fertilizers, growth regulators,
and pesticides have all been known to influence the quality of produce to varying
degrees. Marked effects on yields and quality have been found in fruits and vege-
tables to which different types of fertilizers have been applied. Growth regulators
have been known to modify size, shape, duration of maturation, and other growth
characteristics. Pesticide residues give rise to flavor taints in fresh and processed
products. If excessive amounts are used, fruits and vegetables may even produce
toxic metabolites that may not necessarily be destroyed during processing. The same
variety of plant grown in different locations will sometimes vary in composition,
taste, and desirability. Valencia orange juice from California is, in general, more
deeply colored and more acidic than that from Florida. Grapefruits from Florida
have higher naringin content and a more pungent tang than those grown in California
and Arizona. The latter possess a stronger acidic taste due to higher citric acid
content. Likewise, Texas-grown grapefruits have higher soluble solids:acid ratio and
lower naringin content than fruits from other states.
The ascorbic acid content of turnips and rutabagas is influenced by variations
in soil fertility and moisture of the locations where they are grown (Salunkhe and
Kadam, 1998). Growth in general is also influenced by the soil temperature because
of the increased uptake of minerals. The nitrogen, phosphorus, and potassium are
higher in the leaves when large quantities of minerals are available in the soil. The
literature relating to the effect of fertilization upon the nutrient content is generally
contradictory, presumably because of the variations in soil chemistry, water avail-
ability, and other environmental factors. It can thus be stated that adequate fertili-
zation with nitrogen, phosphorus, potassium, calcium, magnesium, manganese,
boron, and iron is essential for normal growth and adequate yields of high-quality
nutritious crops (Winsor and Adams, 1975).
Seasons also influence the nutritional quality of produce. In general, the effect
of season and light on the synthesis of any nutrient in a plant depends on the plant
species, the amount and duration of light exposure, and temperature and soil fertility.
In pineapples, for instance, summer fruit is generally richer in volatile flavor con-
stituents than winter fruits. In tomatoes, the quantity of sugar increases as the
growing season progresses (Winsor and Adams, 1975). The carotene content of
carrots tends to decrease during fall and winter and increase in the early spring.
Likewise, the ascorbic acid content of turnip greens is highest in the spring and
lowest in the fall, but in other greens, such as kale, broccoli, and collards, the ascorbic
acid content is not affected by the season. It has also been found that carotene content
decreases with an increase in light intensity; thiamin content increases when trace