CHAPTER 17 VEGETABLES

I. CLASSIFICATION OF VEGETABLES A. Vegetables can come from any part of the plant 1. Roots a. carrots b. beets c. radishes 2. Bulbs a. onions b. garlic 3. Stems a. celery b. asparagus 4. Seeds a. beans b. corn c. peas 5. Flowers a. broccoli b. cauliflower B. Believed vegetables that are actually fruits 1. Tomatoes 2. Squash 3. Cucumbers 4. Avocados 5. Olives 6. Peppers

II. COMPOSITION OF VEGETABLES A. Structure 1. Cell wall a. cellulose – indigestible for humans b. pectic compounds – provides firmness and elasticity c. hemicellulose – provides firmness and elasticity d. lignin – provides rigid structure to plant and increases with age e. gums – swell greatly with heating 2. Parenchyma cells are responsible for a plant’s a. starch content b. color c. water volume d. flavor 3. Intercellular air spaces a. spaces between cells that add volume and crispness to vegetables and fruits b. apples have about 25% by volume and potatoes 1% B. Pigments 1. Carotenoids a. types - carotenoids  reddish-orange - lycopenes  deeper red - xanthophylls  light yellow b. heat and oxygen exposure will diminish the colors 2. Chlorophyll a. essential for photosynthesis (usage of the sun’s energy for the conversion of water and carbon dioxide to carbohydrate) b. green in color c. will often mask other carotenoids until degraded d. a fat-soluble pigment that will diminish quickly in the presence of heat 3. Flavonoids a. anthocyanins - red, purple, and blue colors in vegetables - will diminish quickly in the presence of a base - will become brighter in the presence of an acid b. anthoxanthins - comprised of flavones, flavonols, flavonones - creamy white in color - will become more pronounced in the presence of an acid c. betalains - red and yellow hues - will become brighter in the presence of an acid - red will turn yellow in a basic medium

III. PURCHASING VEGETABLES A. Grading Vegetables 1. Done on a voluntary basis because of perishability 2. Graded according to a. color b. ripeness c. shape d. uniformity e. size f. freedom from bruises and decay B. Choosing Vegetables 1. Vegetables have growing seasons like any other plant 2. Vegetables can have radically different flavors when purchased out of season

IV. PREPARATION OF VEGETABLES A. General Guidelines 1. Buying a. purchase the freshest available b. purchase only what you will use in a few days 2. Storage a. store immediately b. do not leave out of storage any longer than necessary 3. Washing a. all vegetables must be washed prior to use b. washing should be done quickly to avoid excess water absorption 4. Cooking liquid a. use as little as possible b. water soluble vitamins readily leach out 5. Timing a. cook as quickly as possible b. do not overcook c. serve immediately B. Changes During Heating 1. Texture a. heat will cause - gelatinization of starch - decrease in bulk by softening the cellulose - reduces turgor by water loss b. acids should be added at the end of cooking as they will increase the amount of time needed for cooking 2. Flavor a. comes from volatile oils b. quick cooking helps preserve these flavors 3. Odor a. usually from sulfur compounds b. most times these compounds are not volatile unless exposed to air 4. Color a. can be affected by heat, pH, and different metals b. the Maillard reaction, caramelization, and enzymatic browning are other well know influences 5. Nutrient retention a. do not cook in water; rather steaming is preferred b. leave in larger pieces rather than small c. leave the skin intact with the vegetable if possible C. Dry-Heat Preparation 1. Baking 2. Frying D. Moist-Heat Preparation 1. Simmering 2. Steaming 3. Microwaving E. Preparing Legumes 1. Best prepared by simmering 2. May be soaked as desired, but soaking helps the legumes to retain their skins 3. It is best to avoid cooking in hard water or added salt prior to the end of cooking

V. STORAGE OF VEGETABLES A. Harvesting 1. Vegetables continue to respire after harvest 2. Treating with nitrogen gas is not uncommon 3. Moisture loss post-harvest is another big problem B. Refrigeration 1. Reduces respiration 2. The greater the moisture content of the vegetable, the shorter amount of time available to store it C. Dry Storage 1. Best for vegetables that are not completely ripe at time of purchase 2. Potatoes have a very undesirable conversion with refrigeration making them waxy 3. Onions and potatoes should not be stored next to each other as their shelf lives will be greatly shortened D. Controlled-Atmosphere Storage 1. Vacuum packaging 2. Severely limits respiration 3. Can potentially last up to 75 days