Solar Drying: Fundamentals,Applications and Innovations - National ...

Aware and Thorat - Solar Drying of Fruits and Vegetables
2.2.2. Vegetables
The green colour of most vegetables is due to chlorophyll, which is the most widely distributed
plant pigment. The most common change that occurs in green vegetables during
thermal processing and storage is the conversion of chlorophyll to pheophytins,
causing a colour change from bright green to olive-brown, which is undesirable to the
consumer (Schwartz and von Elbe, 1983; An-Erl King et al., 2001). For green vegetables,
pretreatment prior to drying can aid the chlorophyll retention during the drying operation.
When vegetables are maturing in the field they are changing from day to day. There
is a time when the vegetable will be at peak quality from the stand-point of color, texture
and flavor. This peak quality is short and may last only for few days. The vegetables can
be stored, in some specific natural conditions, in fresh state that is without significant
modifications of their initial organoleptic properties. Fresh vegetable storage can be
achieved by short term like freezing or by cold storage and long term by drying. In order
to assure preservation for long term storage, it is necessary to process them by drying
(Jairaj et al., 2009).
Vegetables are classified according to which part of the plant is consumed. Some
of the vegetables may fall into more than one category as more than one part of the
same plant is consumed.
2.2.2.1. Types of vegetables
Leafy Vegetables: The plants whose edible parts are the leaves. They are valued because
of their mineral and salts content. These includes, broccoli, cauliflower, globe artichokes,
kale, collard greens, spinach, arugula, beet greens, bok choy, chard, choi sum,
turnip greens, endive, lettuce, mustard greens, watercress, garlic leaves, cabbage, fenugreek,
spinach, coriander etc.
Fruit and flower vegetables: The plants whose edible parts are the fruits and the
flowers, they are fruits or buds of flowers in reality but are used as vegetables. They are
avocado, bitter melon, capsicum, cucumber, eggplant, olive, pumpkin, tomato, snake
gourd, winter melon etc.
Root, Tuber and Bulb vegetables: The varieties included in this class are closely related
as to food value. Bulbs are usually grown just below the surface of the ground and
produce a fleshy, leafy shoot above ground. Bulbs usually consist of layers or clustered
segments, Such as onion and garlic. Tubers are vegetables which grow underground on
the root of a plant, Such as sweet potatoes, beets, radishes. Roots are a long or roundshaped
taproot, Such as asparagus, beet root, carrot, Yam etc.
Podded vegetables: They include all the varieties of beans, peas, and lentils. When
these foods are mature and dried, they have the highest food value of all the vegetables.
They include, chick pea, drum stick, soyabean, indian bean, okra, moong bean, lentils,
peanuts etc.
Seaweed vegetables: Seaweed offers a wealth of essential nutrients found in human
blood serum including vitamins, minerals, enzymes, amino acids and fatty acids. They
includes Aonori, Carola, Dabberlocks, Dulse, Hijiki, Kombu, Mozuku,Nori, Sea grape etc.
56 Drying of Foods, Vegetables and Fruits