Vegetable Handling & Storage
Vegetables provide color, flavor, and texture to culinary preparations. They are nutrient-rich and essential in the human diet for maintaining health and preventing diseases. Although humans are omnivores, they originally started as plant eaters and graduated to eating meats. Today, many people choose a vegetarian diet as a matter of health or for ethical reasons.
Vegetable Composition
Fresh vegetables are high in moisture, generally greater than 70% for potatoes and as high as 95% for lettuce. They are low in proteins and fats, with a few exceptions, such as avocado, which has a high-fat content, and corn, which has a moderate fat content.
Vegetables contain digestible carbohydrates in sugars and starches and indigestible ones in the form of cellulose fibers, which are essential for plant structure. Plus, they provide roughage in the human diet. Another fiber, lignin, is the woody part found at the base of stems, including asparagus, broccoli, and other vegetables. It is inedible and usually removed from the plant before cooking.
Vegetables are a good source of minerals, including calcium, iron, magnesium, phosphorus, manganese, potassium, copper, fluoride, and vitamins, especially vitamins A and C, particularly in the yellow-orange and green leafy vegetables.
Vegetable Pigments
Chlorophyll is a fat-soluble pigment in green vegetables, including broccoli, spinach, and green beans. It is an unstable pigment easily affected by heat and acids such as lemon juice or vinegar, turning it a drab green. Alkaline found in small amounts of tap water or the form of baking soda helps preserve color but destroys vitamins and breaks down the structure of the vegetable, making it mushy.
Because chlorophyll is such an unstable pigment, special care should be taken in cooking. In raw vegetables, gasses trapped between the cells cloud the bright green color of the vegetables. Cooking releases these gasses and brightens the color. However, continued cooking causes a magnesium atom in chlorophyll to detach and be replaced by hydrogen, changing the bright green to a dull gray-green color.
Cooking green vegetables in a large quantity of boiling water as quickly as possible and then stopping the process by plunging them into ice water is the best way to preserve the bright green color. This method is known by the French term a l’anglaise.
Carotenoids are fat-soluble pigments in orange vegetables, including carrots, sweet potatoes, and winter squash varieties. Carotenoid pigments also include lycopene, found in tomatoes, watermelon, pink grapefruit, and xanthophyll, giving corn its yellow color. Carotenoids are relatively stable pigments but are affected by heat, acids, and alkaline. Overcooking will diminish their bright color. Acids will dull their color and prevent tenderization. Alkaline will brighten their color but soften their texture.
Anthocyanin is a water-soluble red to blue colored pigment found in red cabbage, radishes, purple or blue potatoes, and fruits, including cherries, berries, and apples. When cooking these foods, they need help stabilizing their color. Plain water turns an anthocyanin plant from its typical hue to a dull, unappetizing blue. Acids, including lemon juice, vinegar, tart apple, and wine, will intensify the red color. Because acids will firm the vegetable, they are often not added immediately in the cooking process. Alkalis will turn anthocyanin into an unappetizing green or blue-green and is not recommended during cooking.
Anthoxanthin is a water-soluble white to yellow pigment found in onions, white potatoes, cabbage, cauliflower, turnips, parsnips, white wheat flour, and pears. It is a relatively stable pigment, but overcooking can cause the pigments to discolor and turn a dull yellow to gray or even pink. Acids, including citrus juice and vinegar, will help maintain a white color during cooking. Alkalis in baking soda will turn the pigments yellow and the texture mushy.
Betalain is a water-soluble red-yellow pigment in beets, chard, amaranth, and cactuses. The pigment bleeds easily, and vegetables lose color when cut and cooked in water. Acids will brighten the vegetable and help retain color but prevent them from softening, so it is best to add after the vegetables begin tenderizing. Beets turn slightly blue in alkaline solutions, so baking soda should never be used when cooking them.
Vegetable Classifications
Vegetables are often grouped according to their related family, such as the cabbage family, the onion family, or the mushroom family. Vegetables can also be understood by where their edible portion is located on the plant, such as fruits, flowers, or stems. For example, starchy root vegetables can be handled and cooked using the same methods. Salad greens are processed similarly regardless of the type or variety of lettuce. Once common vegetable characteristics are understood, a chef can swap and exchange similar vegetables in recipes, thus allowing for limitless creative variations.
Vegetable Taste and Texture
When freshly harvested, vegetables have a vibrant, sweet flavor and crunchy texture; however, once harvested, they quickly lose flavor, and their texture changes. Vegetables convert their sugar to starches and fibers that are tough in texture and bland in taste. Depending on the vegetable, this can happen quickly, sometimes in a matter of hours. The effects are compounded by the gradual moisture loss in storage. Yeasts, molds, and bacteria also contribute to the deterioration of vegetables. Conversely, many vegetable varieties are pretty hardy and can often be stored for weeks or months before use. Onions, potatoes, and other root vegetables are examples of vegetables that hold well.
Regarding fresh vegetables, the best advice is to order products as needed and avoid prolonged storage. Buying local foods will also provide fresher vegetables with a longer shelf life because commercially grown produce can take a week or more to reach the market. Avoid purchasing pre-cut vegetables because the loss in flavor, texture, and nutrients occurs much quicker. Prep what you need daily and avoid over-processing the vegetables.
Enzymatic Browning
When bruised or cut, vegetables and fruits often develop brown, gray, or red discoloration. This is caused by a chemical reaction from plant enzymes mixing with phenolic compounds and exposure to oxygen. The browning effect can be minimized by coating the vegetables or fruits with citric acids, including lemon juice or vinegar. Potatoes can be peeled and placed in water to prevent browning. Chilling the vegetables below 40˚F/4˚C will slow the process. Blanching or cooking in water will destroy the enzymes. Immerse fresh-cut salad greens in warm water (115˚F/47˚C) for a few minutes before chilling.
Seasonal Availability
Although a wide range of produce can be purchased year-round, buying in season whenever possible makes sense. Seasonal produce usually has superior flavor and texture, is more cost-effective, and can often be purchased locally.
Purchasing and Storing Vegetables
Most produce is stored under refrigeration at 40-45˚F (4-7˚C) with a relative humidity rate of 80-90%. Exceptions to this rule include potatoes and onions, which should be held at 45-55˚F (7-12˚C), and winter squash varieties, which should be stored at 50-55˚F (10-12˚C). Moisture promotes produce deterioration, so it is best to avoid cleaning or trimming vegetables until needed. Some vegetables, including mushrooms, onions, and potatoes, need air circulation to prevent molding and should not be sealed in plastic or air-tight containers. Tomatoes should never be refrigerated because the cold changes the texture to soft and mealy. Purchase produce to use it within three days.
Processing Vegetables
The flavor and texture of vegetables deteriorate when processed. Leave vegetables whole and intact until ready to use. Avoid trimming or washing before storage. Once processed, use as quickly as possible to maximize the flavor, texture, color, and nutrients.
Washing & Soaking
Clean vegetables to remove dirt or other impurities.
Leafy greens are often soaked to remove dirt and other impurities and as a way to refresh them.
Trimming & Cutting
Trim vegetables minimally to maximize yield.
Use vegetable trim for stocks or soups
Compost inedible trim
Soak potatoes in water after peeling
Some produce requires soaking in acidic liquid (citrus or vinegar) to prevent browning (artichokes, eggplant, apples)
Cut and use as close to service as possible.
