Fruit juice is important in human nutrition for beyond its use as a
refreshing source of liquid. Many fruits contain a variety of minor
ingredients, particularly vitamins and minerals, as well as
carbohydrates which are the predominant solid component.
Although fruit contains small amounts of protein and fat, these are not important ingredients of juices.
Nutrients
frequently consumed in sub-optimal concentrations by humans are
protein, calcium, iron, vitamin A, thiamin (vitamin B1), riboflavin
(vitamin B2) an ascorbic acid (vitamin C). Some of these nutrients occur
in higher concentrations in fruit juices than in other foods. There is
experimental evidence that indicates that ascorbic acid of natural
origin is apparently superior to that of synthetic origin.
It
has been established that the above phenomenon is caused by the
presence of certain flavonoids compounds in fruit juice that influence
blood circulation, increasing the permeability and elasticity of
capillaries.
This action is known as vitamin P
activity, but the flavonoids showing this property are not classified as
vitamins, because there several substances with is activity and no
serious deficiency diseases occur if they are not consumed.
There
are indications that these flavonoids have a useful protective action,
in particular against some respiratory diseases, but they are readily
decomposed in the body, and it is impossible to maintain an effective
concentration.
Apart from the more obvious benefits of
fruit juice, such as being a source of potassium, it contains other
substances that have or are claimed to have useful pharmacological
activity. Sorbitol, which occurs in many fruit juices, has a laxative
effect.
Several components with antioxidant activity
are found in fruit juices. These are including ascorbic acid,
tocopherols (vitamin E), beta carotene and flavonoids. Beta carotene has
antioxidant activity that can quench the singlet oxygen that can induce
precancerous cellular changes.
Whatever the
nutritional interest, it should be noted that changes occur during
storage, particularly to the minor components of juices and particularly
under adverse conditions (e.g., light, increasing temperature, time)
Major nutrient and chemical compound in fruit juice
