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The Food you Buy - How Food is Preserved

[Do Not Use]DK Publishing logo[Do Not Use]DK Publishing 2/07/2014 DKBooks
Photo: Well-stocked shelves - Mass food-production methods ensure a plentiful, year-round supply of food products, preserved by a variety of methods, from canning to freezing. © Provided by DKBooks Well-stocked shelves - Mass food-production methods ensure a plentiful, year-round supply of food products, preserved by a variety of methods, from canning to freezing.

Limit sugar intake - Children often like sweet things, but it is important to offer them reduced-sugar foods, such as low-sugar jelly.

Photo: Nutrition facts label - This part of the label is obligatory on most packaged foods and includes information on serving size, calorie content, and amounts of nutrients contained in the product. © Provided by DKBooks Nutrition facts label - This part of the label is obligatory on most packaged foods and includes information on serving size, calorie content, and amounts of nutrients contained in the product.

Photo: Growing needs - Many brands of orange juice are fortified with calcium and Vitamin D, two nutrients that are important for growing children. © Provided by DKBooks Growing needs - Many brands of orange juice are fortified with calcium and Vitamin D, two nutrients that are important for growing children.

Well-stocked shelves - Mass food-production methods ensure a plentiful, year-round supply of food products, preserved by a variety of methods, from canning to freezing.

© Provided by DKBooks

Nutrition facts label - This part of the label is obligatory on most packaged foods and includes information on serving size, calorie content, and amounts of nutrients contained in the product.

Photo: Limit sugar intake - Children often like sweet things, but it is important to offer them reduced-sugar foods, such as low-sugar jelly. © Provided by DKBooks Limit sugar intake - Children often like sweet things, but it is important to offer them reduced-sugar foods, such as low-sugar jelly.

Growing needs - Many brands of orange juice are fortified with calcium and Vitamin D, two nutrients that are important for growing children.

How Food is Preserved

Various techniques are used to preserve the quality of food for long-term storage.

Since ancient times, food has been preserved by techniques such as curing, smoking, storing in salt or brine, and freezing: methods that ensure supplies will not run out when adverse conditions limit the availability of fresh products.

The commercial food producers of today use a variety of methods to prolong the life of their products, including canning, pasteurization, and irradiation, in addition to more traditional methods.

Preserving food not only helps maintain plenty of choices for the consumer throughout the year, but also saves time and energy, since fewer shopping trips are needed to stock up on the ingredients for daily meals.

Preservation methods

Freezing, which is one of the most common methods of preserving food, protects the flavor, color, moisture content, and nutritive value of food. Frozen vegetables, in particular, are often of excellent quality, since they are processed and packaged very quickly after harvesting, with the result that few of the nutrients are lost.

Canned foods are an excellent pantry standby, because they have a long shelf-life. Fruits, vegetables, soups, sauces, and basic meals are all available in this form, providing the basis for a quick meal at any time. All such products carry a food label listing ingredients and a detailed nutritional analysis of the contents .

To make milk and milk products safe for consumption, they usually undergo pasteurization, a process involving heating to a temperature high enough to eliminate bacteria. This process also extends the shelf-life of the product without affecting taste or nutritional value. A variety of other preservation methods are used with milk products, including evaporation, condensation, and UHT.

One of the oldest forms of food preservation, smoking involves exposing foods such as fish, meat, or poultry to the smoke of burning aromatic woods. The process also imparts extra flavor to the food. Traditionally, fish and meats were salted before being smoked, giving a particularly strong taste.

Good and bad additives

A quick look at the food label on commercially produced food products reveals lengthy lists of substances that are added to the basic food ingredients to prolong the shelf-life of the contents and improve its color and taste. These substances are discussed in section Why are additives needed?.

Food irradiation

A relatively recent addition to the range of preservation techniques, irradiation involves the use of electromagnetic waves to eradicate the microorganisms that cause food spoilage and deterioration. Scientists believe it to be a useful, controlled, and predictable process that does not change the important characteristics of most products. Foods that have been irradiated must carry an international symbol in the form of a stylized flower, known as a “radura.”

What do food labels mean?

Food manufacturers are required by law to supply a Nutrition Facts label on most of their products. This label includes 14 mandatory nutrients that must appear in a prescribed order. These particular nutrients were selected because they address current health concerns. The order in which they appear on the label reflects the priority of current dietary recommendations. The panel ends with a footnote explaining the basis of the Daily Values.

Voluntary information

In addition to the mandatory nutrients that must be listed are certain voluntary nutrients. These include the amount of monounsaturated and polyunsaturated fat, soluble and insoluble fiber, sugar alcohol, and other carbohydrates. The percentage of vitamin A present as beta-carotene and the amounts of other essential vitamins and minerals may also be listed. If a claim is made about any of these nutrients, or if a food is fortified or enriched with any of them, the label then has to give nutritional information about these nutrients. Particular claims relating to health issues are now allowed to be printed on food labels .

Ingredients listing

In addition to the mandatory Nutrition Facts panel, food labels must list all ingredients in the product. These are given in order of weight, starting with the greatest. Because some people may be allergic to certain additives, the ingredient list must include the following, if appropriate:

FDA-certified color additives

Sources of protein hydrolysates, which are used in many foods as flavors and flavor enhancers

Caseinate, which is a milk derivative used in foods claiming to be nondairy.

Labeling exemptions

Foods that are exempt from labeling requirements include:

Those for immediate consumption

Bakery, deli, and also candy-store items

Medical foods prepared for patients with nutritional needs

Plain coffee and tea, some spices, and foods containing no significant amounts of any nutrients

Why are additives needed?

Food additives are substances that are added to processed foods in order to improve their flavor or appearance, maintain freshness, increase shelf life, and enhance their nutritional value. They can be either naturally occurring substances or synthetic.

Food manufacturers use at least 3,000 different additives, ranging from familiar substances, such as sugar and salt, to chemicals or preservatives, such as citric acid. The US Department of Agriculture (USDA) regulates additives in different categories. For example, additives can include coloring agents, natural and synthetic flavors, sweeteners, and flavor enhancers to make foods look more attractive and taste better, and stabilizers, thickeners, and emulsifiers to give body and texture to foods.

Additives can also protect foods from adverse conditions, such as variations in temperature and damage during the distribution process. Preservatives slow the spoilage of foods and help protect consumers from food-borne illness. They also help retain a food’s natural color and freshness and keep oils and fats from turning rancid during storage and transportation. Acids, which help in the release of the gas carbon dioxide from yeast, may also have preservative effects in certain foods.

Fortified and enriched foods

Many foods, such as bread and milk, are also fortified with vitamins and minerals that might otherwise be lacking in the diet, or enriched with nutrients that were lost in the refining process . For example, milk is fortified with vitamins A and D, and salt is fortified with iodine, while orange juice contains added calcium and vitamin D. The vitamin folate is now added to cereals and grain products to help reduce the risk of babies being born with neural tube defects .

Young boy with a soy allergy

Name Alexander

Age Four years


This past winter, Alexander attended his cousin’s birthday party at his aunt’s house. A vegetarian, she decided to make pizza made with soy cheese, among other vegetarian alternatives. Alexander enjoyed the pizza, but soon began to sneeze, and had watery eyes with a stuffy nose for the remainder of the party. His parents thought he had a cold and treated him with over-the-counter cold medications.

Now it is summer, Alexander still has symptoms of what seems to be a persistent cold. He has developed an itchy rash that prompted a visit to the doctor. The doctor discovered that Alexander’s parents had decided, soon after the birthday party, to incorporate his aunt’s healthy lifestyle into their own. Since Alexander liked the pizza, they tried other soy products, such as soy nuggets and breakfast links, and tofu hot dogs, as well. The doctor referred Alexander to an allergist, who did a skin-prick test that came back positive only for soy. The test was negative for milk, chocolate, eggs, and peanuts—other common food allergens.


Alexander is a typical four-year-old who attends preschool five days a week, from 9a.m. to 1p.m. His mother prepares a packed lunch, and he enjoys staying with his friends until after lunch. His weekends are filled with playing in the backyard with his sister and outdoor birthday parties now that it is summer. He has just begun his first full day at camp, where lunch is provided. He eats breakfast and dinner at home, and usually has a snack in the afternoon when he returns home from camp at 3p.m.


Since Alexander is allergic to the proteins found in soy, his parents must make sure he does not consume it in any form. They will need to read labels for soy and other ingredients that may contain soy. These include hydrolyzed vegetable or plant protein, vegetable broth, gums, and starches. Soy lecithin, which is made from fatty substances in soy beans, can be eaten safely by many people with soy allergy.

Alexander’s parents should maintain their healthy eating, but with nonsoy products. The nuggets can be prepared with white-meat chicken and sautéed lightly in olive oil. They can buy fat-free hot dogs, low-fat turkey sausages, and pizza with low-fat mozzarella. When they eat out, they must be careful of hidden sources of soy, such as salad dressings, mayonnaise, soy cheese, and certain sauces, such as soy and teriyaki sauce. They should include more grains, vegetables, and fruits as Alexander gets older.

Understanding food additives

The following are some of the additives or groups of additives approved by the Food and Drug Administration (FDA) for inclusion in foods.


Vegetable gum used as a stabilizer or thickener in many foods.


Seaweed product used as a thickener in salad dressings.

Ammonium chloride

Chemical used to help yeast grow in bread products.


Product used to color yogurt, margarine, and smoked fish.

Anti-caking agent

Additive used to absorb moisture and prevent caking or lumping in powdered products.


Protects food from breakdown on exposure to air.

Baking powder

Mixture of baking soda, starch, and an acidifying agent, used to help baked goods rise.

Calcium chloride

Chemical that helps bread rise. It is also used to keep fruits and vegetables firm during cooking.

Calcium propionate

Used to prevent mold from growing in cheese and baked goods. It occurs naturally in Swiss cheese.

Calcium sulfate

Used to boost calcium content in bread and keep tomato products and canned vegetables firm.

Caramel color

Coloring agent made from toasted sugar.

Carob (locust bean) gum

Thickener used to improve texture and to blend ingredients together.

Carrageenan (Irish moss)

Seaweed product used in ice cream to stabilize the size of ice crystals and to keep cocoa from settling in milk.

Cellulose gum

Plant additive used to improve texture and retain moisture in candy, pastry fillings, and jellies.

Citric acid

Chemical derived from citrus fruits and used to maintain food color, increase tartness, and prevent foods from becoming rancid.


A starch, commonly used as a thickener in gravies, sauces, and baking mixes.


Substances that help prevent the separation of ingredients that would not normally mix, such as oil and water. Used in salad dressings and mayonnaise where they prevent oil separating from vinegar.

Guar gum

Plant substance used as a thickening agent in sauces, milk products, and baking mixes.


Help maintain moisture in foods by absorbing water from the air. They may be listed as glycerol, propylene glycol, and sorbitol.

Hydrolyzed vegetable protein

Derived from soybeans, wheat, or corn and used as a flavor enhancer.

Leavening agents

Products such as yeast and baking powder that cause baked goods to increase in volume during cooking.


Typically derived from eggs and soybeans and used to keep foods from separating. Also prevents loss of flavor and food becoming rancid.

Modified food starch

Substance made from grains, potatoes, or tapioca that keeps ingredients from separating and prevents lumps in powdered foods.


Monosodium glutamate (MSG) is used as a flavor enhancer in a variety of foods prepared at home, in restaurants, and by food manufacturers.


Fruit-derived additive used in jellies, jams, and soft candies as a thickener, to prevent separation of ingredients and give a gel-like texture.

Phosphoric acid

Used to make food acidic and to give texture to soft drinks.


Blending agents used to keep oil and water from separating.

Potassium sorbate

Used in cheese, margarine, and wine to prevent microbes from causing food spoilage.


Chemicals that prevent discoloration or rancidity in food.

Silicon dioxide

Used to keep salt from clumping or foaming.

Sodium aluminum phosphate

Used in cheese processing to aid congealing. Also used to keep processed fruits and vegetables firm.

Sodium benzoate

Prevents microbes spoiling processed foods.

Sodium erythorbate

Maintains flavor and color in cured meats.

Sodium hexametaphosphate

Used to retain moisture, preserve beef and pork products, and prevent cheese and ice cream from becoming rancid.

Sodium stearoyl-2-lactylate

Helps bread dough bake evenly and prevents spoilage. Prevents separation of oil and water in salad dressings and nondairy creamers.


Used to prevent discoloration in dried fruits and inhibit bacterial growth in wine.


A coal-tar derivative used to color foods, especially dairy products.

Xanthan gum

Used as a thickener, emulsifier, and stabilizer in dairy products, desserts, and dressings.

Sugar and no-calorie sweeteners

In addition to adding sweetness, sugar’s distinctive properties enable it to play an important role in food preservation. For example, sugar (otherwise known as sucrose) absorbs and retains water very easily and is therefore included in breads and muffins to help keep them moist and tender. Sugar also helps prevent the growth of bacteria in jams and preserves, and retain the bright colors of canned fruits, when they are packed in a sugar solution. Sugar, however, is also a source of “empty calories” and, as such, contributes to a number of health risks, including overweight and tooth decay.

A diet rich in sugar can also blunt your appetite for more nutritious foods, such as those containing complex carbohydrates, vitamins, and minerals. Therefore, try to limit your intake of sugary foods.


A variety of sweeteners—no-calorie sweeteners and sugar alcohols (polyols)—are used by food manufacturers in their products. These are many times sweeter than sugar and much less is needed, with a corresponding decrease in the calorie content. The following are among the most commonly used sweeteners.


Commonly known as Ace-K, this is 200 times sweeter than table sugar, yet contains only four calories per teaspoon. It is safe and, since it is not absorbed by the body, is ideal for people who have diabetes.


This synthetic sugar is 200 times sweeter than sugar, yet contains less than four calories per teaspoon. It is not suitable for baking or cooking. Studies done by the Food and Drug Adminstration conclude that aspartame is safe and especially useful for those with diabetes. However, aspartame is potentially life-threatening for people who have the inherited condition phenylketonuria (PKU), in which the body cannot process the amino acid phenylalanine. Products containing aspartame are marked with a warning.


This was the first substitute sweetener and remains one of the most popular. It is 300 times sweeter than sugar and is suitable for baking and cooking. Studies confirm that it is safe and poses no danger to humans.


This is 600 times sweeter than regular sugar, and is the most versatile sweetener. It is available in granular form that, cup for cup, can replace sugar in drinks and recipes.


Used as a sweetener and to protect against moisture loss in food products, sorbitol is 60 percent as sweet as sugar, with one-third fewer calories. It provides a cool, pleasant taste and withstands high temperatures.


This sweetener is also used in food products as a stabilizer, bulking agent, and humectant. It is more than 70 percent as sweet as sugar and, like sorbitol, has a cool, sweet taste.

Claims about fat

Increasing public awareness of the links between certain components of food, such as fat and sodium, and health have led manufacturers to market products with those concerns in mind. However, it is not always obvious what is meant by the various claims that are made.

The most confusing area of food labeling is with products that claim to be low- or reduced-fat. For example, a vegetable oil labeled “94 percent saturated-fat-free” may be mistakenly perceived as 94 percent fat-free and therefore much lower in calories than it actually is. If you take a second look at the nutritional information on the back of the bottle, you will see that 100 percent of the calories come from fat.

Understanding nutritional claims about fat content

The Food and Drug Administration has produced standard definitions for nutritional claims on food labels. Many of these relate to fat content per serving size, which is given on the food label. However, claims are also made about sodium, potassium, fiber, and calorie content. Here, we list the definitions relating to fat content:


The product must contain less than 0.5g of fat per serving.

Low fat

The product must contain less than 3g of fat per serving, or at least 50 percent less fat than a comparable product.

Low saturated fat

The product must contain less than 1g of saturated fat per serving.


The product must contain at least one-third fewer calories than a comparable product and must contain less than 50 percent of calories from fat.

Reduced fat

The product must contain at least 25 percent less fat than a comparable product.

Low cholesterol

Each serving must contain less than 20mg of cholesterol and 2g of total fat.

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