Key Concepts and FactsMinerals are single atoms that cannot be created or destroyed by any ordinary means

Minerals are components of body structures and play key roles in the regulation of body processes

Deficiency diseases occur when too little of 1 or more of the 15 essential minerals is provided; overdoses occur when too much is provided

Inadequate intakes associated with chronic disorders like osteoporosis, iron deficiency, and hypertension

What are Minerals?Minerals are elements the body needs in varying

amountsMinerals needed in amounts of 0.1g or more each day

are called MACRONUTRIENTS or MAJOR MINERALSSodiumCalciumPhosphorusChloridePotassiumSulfurMagnesium

What are Minerals?Minerals the body needs in amounts of 0.01g

or less each day are known as MICRONUTRIENTS or TRACE MINERALSIronZincIodineCopperManganeseFluorine . . . and others

SodiumSodium is found in the body as positive

sodium ions.

Sodium helps maintain the balance that allows water to flow freely in and out of cells.

Salt is the primary source of sodium.

We only need 1 teaspoon per day at maximum: about 2.5 grams

Sodium and Water BalanceConsumption of a

salty meal or snackMakes you thirsty to

dilute the saltMakes you excrete

the salt (and water)Makes you thirsty to

replace lost water

Sodium ExcessExcessive amounts

of sodium can be problem to those with high blood pressure or heart disease.

Excessive amounts can LEAD to these problems, too!

Examples of how processing increases the sodium content of foods’ sodium values are for a 3-ounce serving of each food shown

Label Watch Not all processed foods with added

sodium taste salty

Increasingly, low-salt processed foods are entering the market and can be easily identified by the “low-salt” message on the label

To be considered low-sodium, foods must contain 140 milligrams or less of sodium per serving

CalciumCalcium is important to the body’s structure.

Calcium is needed to build and maintain strong teeth and bones; it also circulates in the body and maintains cell membranes.

Calcium ensures proper muscle action, regular heart-beat and blood clotting.

High levels of calcium is found in milk

Too Little CalciumOnly 14% of girls and 36% of boys between

12 and 19 consume recommended calcium

Calcium is also important to growing children and women throughout their life.

Low calcium intake during growing years increases probability of fractures and osteoporosis

Deficiency of CalciumA lack of calcium can cause osteoporosis.

(left) Electron micrograph of healthy bone (right) Electron micrograph of bone affected by osteoporosis

Osteoporosis44 million adults in the United

States have osteoporosis. 1.5 million suffer broken bones each year due to the disease

Osteoporosis increases with age

Much osteoporosis can be prevented

Build dense bones during childhood and keep bones dense as you age

How NOT TO lose Vitamins and Minerals

Enzymatic BrowningWhen fruits are cut or bruised oxygen enters the

damaged tissues so browning occurs.

The brown compounds that are produced are called melanins. Although unappetizing, they are safe to consume.

Fruits that are susceptible to enzymatic browning include apples, pears, bananas, avocados and others.

Prevention of enzymatic browningTo prevent enzymatic browning, the

enzyme may be denatured by: blanchinginhibited by adding acid to reduce the

pH. addition of either lemon or lime juice, with an

average pH of 2.3 and 2.2 respectively, is a good method of preventing browning

Fruits may be protected from exposure to oxygen by covering them with syrup

Blanching and SuchProducts such as Fruit Fresh, which contain

vitamin C in dried form, also prevent the browning reaction; they are available in the grocery store.

Fruits (and vegetables) that are to be frozen are usually blanched first; that is, they are briefly placed in boiling water. The short heat treatment is sufficient to inactivate the enzyme and prevent browning from occurring during frozen storage.

Preparation of FruitsFruit is often served raw because the texture is

usually more desirable than that of cooked fruit.

Heating causes several changes in fruits. They soften, due to softening of pectin Normally, the cell membrane allows water to pas

through it, but not solutes such as sugars or minerals.

The water moves from a low concentration of solutes to a higher one, until the solution concentration is equal on both sides of the membrane. This is known as osmosis.

If sugar is sprinkled on fruit such as strawberries, water will move out of the cells to the surface, where the solute concentration is higher, and sugar syrup will develop around the fruit.

Heating destroys the membrane’s ability to prevent loss or uptake of solutes through the cell wall. Solutes can then freely pass across the membrane until solute concentrations are equal on both sides. This is termed diffusion.

This principle must be taken into consideration when cooking fruit. If sugar is added to the fruit before it is cooked, it will help to retain its shape and firmness during cooking (especially if the fruit is not stirred), because the sugar enters the cells as the water leaves. Depending on the sugar concentration, the fruit may actually shrink. On the other hand, if fruit is cooked without sugar, the water moves into the cells and sugar moves out; this causes the fruit to swell and disintegrate. This is desirable if making a fruit sauce; if sugar is needed for flavor, it is best to add it at the end of the cooking period in this case.

Fruits may be prepared in different ways, such as baking, broiling or stewing, which adds variety and interest to the ways in which they may be served. For specific preparation methods, refer to pages 286-291 in your text book.

Nutrient Content Fresh vegetables are naturally low in calories, cholesterol, sodium and fat, and are good sources of fiber, vitamins, minerals and phytochemicals. Phytochemicals are non-nutritive compounds found in plants that possess health-protective benefits. The cruciferous vegetables (broccoli, Brussels sprouts, cabbage,

cauliflower, kale, etc.), as well as strawberries, pineapples and green peppers, contain phytochemicals that appear to inhibit cancer in laboratory animals. Tomatoes contain lycopene, which has also been identified as a phytochemical. The composition and nutrient content for the different types of vegetables depends on their function in the living plant. For example, photosynthesis takes place in the green leafy vegetables, and so they have a high water content, but are low in starch. All vegetables with a high water content are low in calories.

On the other hand, vegetables such as dried beans, potatoes and corn act as storage depots for the plant, and so they have a high starch content, and are therefore somewhat higher in calories; they also have a relatively low water content.Dark green leafy vegetables are good sources of riboflavin (vitamin B2), carotene, vitamin C and iron. Green vegetables are generally high in vitamin K and folate. Broccoli is also high in calcium. However, green vegetables also contain oxalates, which can bind to calcium, zinc and iron and may decrease their

absorption. The legumes (dried beans, peas and lentils) are relatively high in protein. For a more complete discussion of the nutrient content, see pages 248-249 in your text book.  Plant PigmentsVegetables (and fruits) come in a variety of different colors, which add variety and appeal to meals. It is important to understand how to preserve the color of vegetables during food preparation, so that their appeal is not reduced.Plant pigments can be divided into three categories – carotenoids, chlorophylls and flavonoids. A list of some common fruits and vegetables containing these pigments is given in figure 12.3 on page 247.Carotenoids and chlorophylls are fat soluble and are located in the plastids, whereas flavonoids are water soluble and are located in the vacuoles.Carotenoids include alpha- and beta-carotene (which has vitamin A activity), along with lycopene and the xanthophylls. These are yellow, orange or orange-red pigments, and are found in carrots, winter squash and tomatoes. The carotenoids are relatively stable during typical food preparation procedures, but

they may turn paler during prolonged heating or overcooking. Chlorophylls are responsible for the green color of plants, and they are important in photosynthesis. It is therefore not surprising that green leafy vegetables such as spinach, broccoli, green cabbage and kale are high in chlorophylls. In older plants, the chlorophyll is degraded, causing underlying pigments to

show. This is why broccoli florets left too long on the produce stand may turn yellow. Chlorophylls are not as stable to heat as carotenoids. During the heating process, organic acids are liberated from the vegetables, and they react with the chlorophylls, turning them a drab olive-green color. To avoid this, green vegetables should be cooked for as short a time as possible, and in plenty of water.

Also, cooking with the pan lid off at least for the first few minutes helps to retain the color, because the organic acids are volatile and escape with the steam. Cooking with the lid on concentrates the acids, because they cannot escape, and the chlorophylls are destroyed more quickly.Flavonoid pigments include the red-blue anthocyanins , the creamy to white anthoxanthins and the purplish-red betalains. These pigments are susceptible to changes in color due to pH change and also due to contact with certain metals. Anthocyanins are red in acid, purple at neutral pH and blue in alkali, and are found in vegetables such as red cabbage, egg-plant, radishes and in most berries. To preserve the attractive color of red cabbage, vinegar and/or a tart apple are often added before it is cooked. Without the addition of acid, red

cabbage may turn an unappetizing blue color, due to the alkaline pH of the cooking water. Anthocyanins may turn unpleasant colors in the presence of copper, iron, aluminum and tin. This effect may be seen if red cabbage is cut with a non-stainless metal knife, or cooked in an iron skillet.Anthoxanthins are white in acid, creamy at neutral pH, and turn yellow in an alkaline medium. They are found in white or light-colored vegetables such as cauliflower, potatoes and onions, and also fruits such as pears. Adding vinegar or lemon juice will increase the whiteness of vegetables containing these

pigments. Undesirable dark colors may be obtained if these pigments come in contact with metals.Betalains give beets their deep purplish-red color. These pigments are red in acid, purplish-red at neutral pH, and yellow in an alkaline medium. When cooking beets, it is best not to peel them first, in order to retain their deep color. Being water-soluble, the pigment will bleed into the water during cooking,

resulting in a paler colored vegetable.The colors of the different pigments in the presence of acid, alkali, heat and metals are summarized in table 12.4 on page 262 in your text book. Preparation of VegetablesThe following general principles should be followed when preparing vegetables:Purchasing: buy the freshest possible vegetables in amounts that you will use within a few days.Storage: Store vegetables at the appropriate temperature; refrigerate left-overs immediately and use within three days.Washing: All vegetables must be thoroughly washed, using a vegetable brush where appropriate, to remove soil, microorganisms, pesticides and herbicides. This is particularly important if the vegetables are to be eaten raw. Peeling and cutting: Remove only the minimum amount of peel, to avoid loss of nutrients. Cutting vegetables also results in loss of nutrients, so don’t cut up vegetables ahead of time, and don’t cut into smaller pieces than necessary.Cooking liquid: In general, as small an amount of liquid as possible should be used, to minimize loss of nutrients.Timing: The cooking time should be as short as possible to avoid nutrient loss as well as undesirable changes in texture, color and quality.Changes During HeatingTexture: High temperatures gelatinize starch, soften cellulose, and also cause water loss. This results in softening of the vegetable, and is desirable when baking potatoes and cooking legumes, but other vegetables should be heated until barely cooked, to retain their crispness. Acids or acidic foods, such as

vinegar or tomatoes, should be added toward the end of the cooking time, because they make vegetables more resistant to softening, and increase heating time. Adding alkaline ingredients such as baking soda has the opposite effect, breaking down cellulose and producing a mushy texture.Flavor and Odor: In general, vegetables should be heated as little as possible in order to retain flavor components. However, there are exceptions; onions develop a milder flavor when cooked for a longer period of time. Vegetables that belong to the brassica and allium families contain bitter sulfur compounds that are activated or formed during preparation or cooking. The brassica group includes broccoli, cauliflower, Brussels sprouts, cabbage, kale, mustard greens, kohlrabi, rutabaga, and turnips. These vegetables develop

unpleasant flavors during cooking, which become stronger with increased cooking time. To minimize strong flavor, these vegetables should be cooked for a short time, in a large amount of water. It is also helpful to keep the lid off the pan during the initial heating period, to maintain a low concentration of organic acids.

The allium family includes onions, chives, garlic, leeks and shallots. Cutting the vegetables in this family activates an enzyme (alliinase) which causes an intense odor. Cooking causes these vegetables to lose their strong flavor and odor, because the compounds escape with the steam. Again, they should be cooked uncovered in plenty of water if their flavor is to escape; less water should be used if a stronger flavor is desired.

Nutrient retention: Careful preparation of vegetables conserves important nutrients. In general, they should be cooked in as little water as possible to retain water-soluble nutrients, which are lost by leaching into the water. Also, the pan lid should be kept on to minimize nutrient loss through oxidation. Steaming, baking or microwaving may conserve nutrients, because the vegetables are not immersed in water. However, as has already been discussed, cooking in a small amount of water with the pan lid on may not be beneficial for color retention or flavor development of certain vegetables. It is important to consider which vegetable is being cooked, and whether it is most important to preserve color, minimize strong flavors, or retain nutrients. In addition, heating in a large amount of water speeds cooking, which will offset the increased nutrient loss. Other ways to minimize nutrient loss are to leave the skin on wherever possible, to cut vegetables into fewer, larger pieces, and to cook just to the point of doneness and no further.

Color: Heating influences color as has already been discussed in the section on pigments. Chlorophylls may turn a drab olive green, and the pH in the cooking water may change the color of the flavonoids (anthocyanins and anthoxanthins). This can be prevented by adding acid (cream of tartar, vinegar or lemon juice) to vegetables containing these pigments, such as red cabbage or cauliflower. However, it must be remembered that the addition of acid increases heating time because it slow softening of pectin and cellulose. Some potatoes may turn grey when exposed to oxygen; this can be prevented by soaking cut potatoes in water with a little lemon juice or cream of tartar added.

Cooking MethodsVegetables may be baked or roasted, fried, simmered, steamed or microwaved. For details on these cooking methods, read pages 262-266 in your text book. Potatoes are the most commonly baked vegetable, and take approximately one hour to bake in a conventional oven. Russet and Idaho potatoes are good for

baking. These are “mealy” potatoes with a high starch content, which yield a dry, light, fluffy texture when baked or mashed. Waxy potatoes such as round Reds have less starch than other types and are more suited for simmering. Their higher moisture content and better ability to hold their shape make them appropriate for dishes such as potato salad, soups, casseroles and scalloped potatoes.

 Storage Requirements of VegetablesVegetables (and fruits) continue to respire after they are harvested, taking in oxygen and releasing carbon dioxide. This natural respiration contributes to the deterioration of their appearance, texture and flavor and vitamin content. The faster the rate of respiration, the more quickly the vegetable deteriorates.

Respiration can be slowed by storing vegetables in the refrigerator. However, not all vegetables should be refrigerated; tomatoes, for example, are picked while green and unripe, and should be ripened in a paper bag. If placed in the refrigerator, they never reach their optimum flavor and texture. Once fully ripe, they may be refrigerated to slow spoilage. Other vegetables that should not be stored in the refrigerator include winter squash, potatoes and onions.

Other post-harvest changes include loss of moisture due to evaporation, which results in wilting. This can be minimized by maintaining a humid atmosphere. In the grocery stores, vegetables are intermittently sprayed with a fine mist of water to prevent water loss. In the home, vegetables should be stored in the refrigerator’s crisper, which is designed to retain moisture. Alternatively, plastic bags with tiny holes may be used; the holes allow the vegetables to breathe. Airtight plastic bags should not be used because they promote spoilage. Vegetables with a high percentage of water, such as lettuce, tomatoes and spinach, have a shorter shelf life (or storage time) than vegetables such as potatoes and carrots. Since leaves draw moisture from the rest of the plant, removing the green tops of carrots or radishes will increase the shelf life of these vegetables.

If vegetables are to be frozen, they should first be blanched. Blanching involves heating in boiling or near-boiling water for a short time, to denature enzymes that would cause deterioration of the vegetables during frozen storage.Storage of vegetables is discussed in more detail on pages 266-267 in your text book.

A: Fruits- Enzymatic Oxidative BrowningTo observe the effects of various treatments

on development of browning on the cut surface of apples.

To explain the mechanism by which various treatments inhibit oxidative browning.

To compare browning tendencies of the selected foods.

B: Vegetable- Effects of Cooking Treatments on Vegetable PigmentsTo observe the effects of cooking time on

plant pigments.To observe the effects of acid and alkali on

plant pigments.