Introduction
Vegetables: are the edible portion of plants eaten with (or as) the main course. They are in salads and soups. Vegetables may be processed into beverages or vegetable starches, eaten fresh or lightly processed, dried, pickled, or frozen. They impart their own characteristic flavor, color, and texture to diets, and undergo changes during storuge and cooking. Ranked nest to the cereal crops wheat, rice, and com, potatoes are the mont prolitic vegetahle crop grown for human consumption.
Fruits : are defined in more than one way. Botanically, fruits are the mature ovaries of plants with their seeds. Therefore this definition includes all grains, legumes, nuts and seeds, and common "vegetable-fruits" such as cucumbers, olives, peppers, and tomatoes. When defined and considered in a culinary role, fruit is the fleshy part of a plant, usually eaten alone or served as a dessert. Fruits are high in organic acids and sugar-higher than vegetables. The nutritive value of vitamins, minerals, fiber, and other compounds contained in fruits and vegetables is extremely important to the diet. Additional dietary and medicinal benefits of fruits and vegetables are being discovered. "Vary your veggies" and "focus on fruits" is the USDA advice in selecting vegetables and fruitsas part of a healthy diet. Also given as USDA advice is "make half your plate fruits and vegetables."
Structure and Composition of Cell Tissue The structure and composition of vegetables and fruits show that they contain both simple and complex cells. The simple cells are similar to one another in function and structure and include dermal tissue and parenchyma tissue. Dermal tissue is the single-layer outside surface of leaves, young stems, roots, and flowers, while paren- chyma tissue (see below) makes up the majority of the plant, and is where basic molecular activity such as the synthesis and storage of carbohydrate by sunlight (photosynthesis) occurs. Complex tissue includes the vascular, collen- chyma, and sclerenchyma supporting tissue. Major vascular tissue consists of the xylem and phloem; xylem conducts water from the roots to the leaves, and phloem conducts nutrients from the leaves to the roots. These tissues may be located in the center of the vegetable, for exam- ple, as is seen in carrots. A plant is composed primarily of simple parenchyma tissue Each cell is bounded by a cell wall produced intemally by the protoplast.
The wall serves to support and protect cell contents and their retention, influx, or release. When the wall is firm, the original shape and texture of the cell are maintained. However, when the wall is destroyed (by cutting, dehydration, or cooking), it breaks and spills its contents into the surrounding environment. Thus, water, sugars, or water-soluble vitamins of a cell may be lost. The primary cell wall is made of cellulose, hemicellulose, and pectic substances including pectin. Older, more mature plants may also have a secondary cell wall composed of lignin (see "Chemical Composition of Plant Material" section), in addition to the primary cell wall. Inside the parenchyma cell wall is the proto- plast, composed of three parts-plasma mem- brane, cytoplasm, and organelles. The plasma membrane surrounds the functional cell, while the cytoplasm of the protoplast includes all of the cell contents inside the membrane, yet out- side the nucleus. The organelles include nucleus, mitochondria, ribosomes, and plastids. It is the plastids that contain fat-soluble material such as fat-soluble vitamins, and fat-soluble pigments including chlorophyll and carotenoids (each is discussed in a subsequent section of this chapter.)
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