Phenolic compounds

Phenolic compounds are the most widely distributed secondary metabolites, ubiquitously present in the plant kingdom, even if the type of compound present varies according to the phylum under consideration.

Generic terms ‘phenolic compounds’, ‘phenolics’ or ‘polyphenolics’ refer to more than 8,000 compounds found in the plant kingdom and possessing at least an aromatic ring with one or more hydroxyl substituents, including functional derivatives like esters, methyl ethers, glycosides, etc.

They contain benzene rings, with one or more hydroxyl substituents, and range from simple phenolic molecules to highly polymerized compounds.

Phenolic compounds mainly exist in: soluble phenolic compounds and bound phenolic compounds.

Most soluble phenolic compounds are synthesized in the intracellular endoplasmic reticulum of plants, and stored in vacuoles. Bound phenolic compounds, however, are formed by the transportation of soluble phenolic compounds to the cell wall.

Phenolic compounds possess numerous bioactive properties and, although they are not nutrients, dietary intake provides health-protective effects, therefore postharvest treatments have been used to enhance or preserve the contents of phenolic compounds in fruits and vegetables.

Plant phenolics are considered to have a key role as defense compounds when environmental stresses, such as high light, low temperatures, pathogen infection, herbivores, and nutrient deficiency, can lead to an increased production of free radicals and other oxidative species in plants.

The basic structure of a phenolic compound comprises of an aromatic ring with one or more –OH groups.

Phenolics found in food material can be divided into three major groups: simple phenols and phenolic acids, hydroxycinnamic acid derivatives and flavonoids.
Phenolic compounds

Definition of Vegetable

A commonly given definition is that a vegetable is a crop used to make vegetable salad. Vegetables are plants foods that include various edible parts such as leaves, shoots, roots, tubes, flower, and stems.

They normally do not include fruit. However, tomatoes and olives which are technically fruit, are include as vegetable , because of their culinary role is related more to vegetables than the fruits, for example , a garden salad almost includes tomatoes and sometimes olives, but it never includes any other fruits.

Vegetables are a horticultural crop. Other horticultural food crops include small fruits and tree fruits, which are usually grown as perennials. Vegetable crops may be either annuals or perennials.

Vegetables belong to important class of foods that supply us with many nutritive requirements, including proteins, starches, fats, minerals, sugars, and vitamins.

Vegetables also supply bulk to the diets well as a large variety of flavor and odors that provide the knowledgeable chef with a repertoire of culinary tricks. On a world basis, vegetable make up a considerable crop being consumed in the fresh state.

Vegetable crops can be classified into 3 main groups according to the plant part that is most commonly eaten.
*Fruit and seed vegetable
*Leaf and stem vegetable
*Root and tuber vegetable
Definition of Vegetable

Classifications of Vegetables

Classifications of Vegetables
Vegetable are classified in the basis of the part of the plants such as root, stem or tuber that is used for food.

Root vegetables
The root group includes beets, carrots, radishes, rutabagas,, turnips and yams.

Stem vegetables
The stem group includes asparagus and kohlarabi.

Tuber vegetables
The tuber is an underground stem. Edible tubers include girasole or Jerusalem artichoke, potato, taro and yam.

Leaf and leaf-stalk vegetables
The leaf group includes Brussels sprouts, cabbage, celery, chard, chicory, endive, lettuce, parsley, rhubarb (pie) and spinach.

Bulb vegetables
The bulb group includes garlic, leek, and onion.

Immature inflorescene vegetables
This group includes artichokes, broccoli and cauliflower.


Fruits used as vegetables
The immature fruits are used as vegetables, cow pea, cucumber, papaya, jack fruit, egg plant (brinjal), Lima bean, okra, pea, summer squash (gourd).

Mature fruit vegetables
This group includes musk-melon, pumpkin, tomato, and water melon.
Classifications of Vegetables