Maintaining Food Quality in Storage
Source of Recipe
The University of Georgia College of Agricultural & Environmental Sciences
Food is like fine china. Not only is it expensive, but it must be handled carefully because of its fragile nature. Food products are susceptible to spoilage, loss of nutrients, insect/rodent infestations, changes in color, flavor or odor, and even package corrosion and leakage. Environmental control of temperature, humidity and pests, as well as inventory control (through proper stock rotation) is needed to minimize these changes in food quality during storage.
By definition, "food quality" includes the nutritional value, aesthetic quality(such as color, flavor, texture and appearance) and functional property (such as thickening power of tomato sauce) of a food product. Food quality is the sum of all the desirable characteristics which make a food acceptable to eat.
The "shelf life" of food products varies and is limited. Food shelf life is that finite time that a product remains of satisfactory quality after manu-facture or retail purchase. The shelf life of a food product depends on its chemical nature and the way it has been processed, packaged, distributed and stored. Processed foods (canned, dried, frozen) have limited shelf life in terms of food quality. They may lose some nutritive value and undergo subtle chemical and physical changes on long-term storage even though they may not be spoiled. Fresh foods, being more fragile, spoil primarily by bacterial deterioration (usually evidenced by off-odor) which reduces their quality. In both cases, these losses are due primarily to fluctuating or inadequate temperature control during storage.
Unfortunately, predicting the exact shelf life of any food product after its manufacture is practically impossible because of a lack of information on the environmental conditions during its distribution. However, many food manufacturers emboss code dates on their product packages which give customers either the age or approximate shelf life of the product at the point of purchase. This date, in addition to directions on further storage, should enable the customer to extend product shelf life and quality until preparation or sale.
There are several reasons for writing this bulletin:
Food service businesses and institutions (which represent the largest segment of the food industry and who purchase large quantities of both fresh and processed foods) must know the proper environmental controls to extend product shelf and food quality.
Wholesale/retail grocers (who practice long-term food storage) need to understand that both environmental control of products and inventory rotation are necessary to maintain quality products for buyers.
There is a demand for consumer information on nutritional changes in stored foods.
Consumers want to know what package code dating means to the shelf life of products they purchase.
Foods Vary in Perishability
Perishability is a relative term when describing a food product because conditions such as holding, processing, and packaging can all influence its shelf life. Milk, for instance, will hold or "keep" for less than a day at room temperature. However, unopened milk will stay fresh for three to four weeks if refrigerated at 35 degrees F. If the fat content of milk is removed and the remainder dried to a powder (and stored in a moisture proof package), the product will remain acceptable for 12 to 18 months.
The three major food perishability categories are as follows:
Perishable foods are those that must be held under refrigerated conditions (32 to 35 degrees F) in order to keep 2 to 30 days. Cold temperatures, if held properly, will slow down the changes which cause these foods to spoil quickly or get stale. Included in this category are fluid milk products, some bakery items, some processed dairy products, fresh meats, fish, poultry, and fresh fruits and vegetables and their juices.
Semi-perishable foods do not deteriorate as rapidly as perishable foods under refrigeration, but still do not have a very long shelf life (between 30 and 90 days). These foods generally last longer because of their natural inhibitors (such as an egg shell) or added inhibitors (such as sugar, salt, vinegar, food additives) and/or a mild type of preservation (pasteurization, pickling, smoking). This category includes eggs, cheese, some pickled foods, processed salads, some fruits and vegetables, and cured meats. Semi-perishable foods can have a shelf life of 30 to 90 days under refrigeration temperatures (32 to 35 degrees F), depending on the food.
Shelf-stable foods are sometimes improperly termed "non-perishable foods," but no foods are truly non-perishable. All foods begin to lose quality at some rate as soon as they are harvested, slaughtered, or processed. Foods in this category last from 90 days to three years depending on the process/packaging system used and their storage environment. Canned foods are heat processed at high temperatures to destroy spoilage agents and their seal prevents further contamination. In dried foods, the moisture level is reduced to a point where spoilage won't occur. Many products are vacuum packed to remove air which can cause spoilage. Shelf-stable foods include dried foods, nuts, grains, cereals, pasta, all canned foods, salt, and sugar. Many frozen foods are considered shelf-stable if the temperature at which they are stored is low enough and consistently maintained to freeze most of the water in the tissues. Some exceptions are fatty meats (luncheon meats, ground beef, lamb, and pork; fatty fish such as mackerel, etc.) and shellfish, giblets, and some bakery goods (cake batter, pie shells, yeast breads and rolls) which are considered semi-perishable even if kept frozen.
Storage Environment Affects Food Quality And Shelf Life
Bacteria, molds, yeasts and enzymatic breakdown are the main causes of deterioration in fresh (perishable and semi-perishable)foods. Usually, bacterial deterioration occurs well before chemical or physical changes can be noticed. The most important factor in maintaining quality and extending the shelf life of fresh foods is a consistent low refrigerated (32 to 35oF) temperature. Various chemical and physical reactions caused by enzymes take place in processed (shelf-stable) foods during storage. These changes are subtle and require a longer period of time to occur but they also are greatly influenced by the storage temperature. Prolonged storage of canned and dehydrated foods at temperatures exceeding 100 degrees F may increase the rate of oxidation of fatty foods leading to the development of rancid off-flavors. Textural changes in protein based foods may occur leading to a loss of functional properties such as whipping, gelling, and thickening power. Brown discolorations may occur in dehydrated foods due to a chemical reaction between its sugar and protein components.
Pigments may oxidize resulting in color fading of highly colored canned fruits or vegetables. Chemical deterioration of some vitamins may also occur. If canned foods are held at excessively high temper-atures (120 degrees F), chemical reactions may occur between the food and the container leading to "pinholing" and leakage of the food product. From a practical standpoint, canned and dried products should be stored at 50 to 70 degrees F to minimize these quality changes and extend shelf life.
Store frozen foods in a temperature range of at least 0 degrees F to -18 degrees F. Note, however, that an even lower storage temperature would preserve product nutrient quality and extend shelf life. Temperatures higher than 0 degrees F can increase the rate of deterioration of fatty foods, contribute to color fading of highly colored products and reduce the stability of some vitamins. In addition, temperature fluctuations great enough to cause thawing and re-freezing may cause protein and carbohydrate breakdown leading to textural changes, such as softening and leakage.
For fresh, canned and dried foods, every 18 degrees F rise in temperature doubles, triples or even quadruples the rate of quality loss, depending on the specific kind of food. So not only is it important to keep the storage temperature as low as practical, it is equally important not to allow the temperature to fluctuate.
Humidity control is very important in the storage of perishable foods. High humidity (90 to 99%) is needed in the storage of most fresh fruits and vegetables to avoid excessive shriveling which affects appearance. Fresh meats which require a lower humidity (70 to 80%) are usually packaged in a material with low moisture permeability. A high humidity (greater than 70%) will provide the moisture needed for microorganisms to cause decay in fresh onions. Semi-perishable foods such as cheese, nuts, and cured meats require a low humidity (50 to 60%) to prevent molding. High humidity will cause rancidity development in fried snack foods as a result of enzymatic action. Dried foods (such as grains, breakfast cereals and dehydrated milk) require a low humidity (50 to 60%) to prevent rancidity develop-ment, molding, and excessive caking or lumping. High humidity in canned food storage areas decreases shelf life by accelerating external can corrosion. Canned goods should be stored at humidity of 65 to 70%.
Pests (Insects/Rodents) cause deterioration and spoilage of food products by damaging the integrity of the food itself or the package surrounding the food. Insects do not destroy food by consuming large quantities of it, but once they damage the product, further deterioration results from microbial invasion. For example, a small insect hole in a tomato may not be a severe problem, but this can lead to bacterial invasion which can spoil the entire tomato. Storage insects such as weevils and beetles infest food products, including grains, flour, cereals, beans, peas, dried fruits, dates, spices, and nuts. They deteriorate food by eating holes in the food or packaging material, leaving their feces and body parts in the food and producing off-odors in the food. Other insects (such as flies and cockroaches) spoil food by depositing their feces and large numbers of bacteria onto the product.
Rodents (rats and mice) damage and contaminate greater amounts of foods and packaging materials through gnawing, chewing, body contact, and by the discharge of their body wastes (urine and feces) onto the product. These pests will eat anything, but prefer meat, fish, fruits, vegetables, bakery products, candy, cereal, and nuts. Rodents have strong, well developed front teeth called incisors. When gnawing and chewing, they exert a force equal to 24,000 pounds per square inch! It is no wonder they have been known to gnaw their way through the steel plate of canned foods. These pests can be controlled by (1) sealing up all openings to food storage areas, (2) eliminating their hiding places by keeping storage areas clean of debris and (3) starving them by removing their food sources through a good sanitation program.
Inventory control is very important. Although food manufacturers attempt to provide the longest shelf life practical (consistent with costs and method of handling), it is the food service employee, wholesaler, retailer, and consumer who ultimately must store food properly to extend its freshness. In addition to environmental control, proper stock rotation is important during food storage. Follow the practice of first-in, first-out (F-l, F-O) to maintain food quality. This means use food in the order in which it is received. For example, don't stack new deliveries of fresh vegetables in front of vegetables already three days old. Likewise, do not put today's frozen beef in the freezer on top of that purchased last month. Good food inventory means setting up a code dating system so new food deliveries are labeled and placed in the rear of the storage areas, and food which has been stored is always utilized first.
How Storage Affects The Nutritional Value of Foods
The major methods of preservation (blanching, canning, drying, freezing, and fermenting) all cause some change in the nutritional value of food, but the loss is not significant. The most sensitive nutrients to change are Vitamin C, and to a lesser extent B1 (thiamin). Other nutrients are much more stable and very little is lost in most processes. However, greater losses can occur due to improper storage of food under adverse environmental (temperature, humidity, etc.) conditions. Assuming proper storage, the question might be asked, "What happens to vitamins, proteins, fats, carbohydrates, minerals, and moisture during long term storage?"
Vitamins - There is every reason to believe that only insignificant levels of B vitamins are lost during the storage of frozen meats, provided the temperature is low enough and does not fluctuate. The ones most susceptible are thiamin (B1) and riboflavin (B2). Canned meat can also lose some thiamin during storage, but the other B vitamins (riboflavin, niacin and pantothenate) appear to be stable. Milk may lose substantial amounts of Vitamins B2 and C within a few hours if stored in a clear bottle in sunlight, whereas Vitamins A and D are not affected. The vitamin content in cereals (rice, wheat) remains relatively stable provided the moisture content does not increase above 10%. The B Vitamin content in stored bread and breakfast cereals remains stable provided good storage conditions are used. Vitamins C and A are regarded as the most important nutrients in fruits and vegetables. But substantial quantities of Vitamin A and C can be lost if produce is held at room temperature (causing shrivel) or if it is mechanically abused in shipping and distribution. Certain cellular enzymes promote the oxidation (and therefore the loss) of these vitamins.
Vitamin losses may occur in canned fruits and vegetables when these products are stored at high temperatures (100 degrees F and above). Although frozen storage temperatures between 0oF and -18 degrees F result in satisfactory Vitamin C and A retention levels in fruits and vegetables, added protection can be given if these products are packaged in materials that are oxygen and light impermeable. At storage temperatures above 15 degrees F, Vitamins A and C are easily oxidized and will be lost in a short period of time. Vitamin E, which is highly susceptible to oxidation, is found in substantial quantities in nuts (peanuts, pecans, etc.). This vitamin can best be preserved by vacuum packaging nuts or freezing them in packages that are oxygen impermeable. Dehydrated eggs can be stored at -18 degrees F for 12 months without loss in niacin, but there is a slight loss in riboflavin (B2) and significant loss in Vitamin B6. Drying does not cause major losses in vitamins, provided the finished foods are adequately protected from oxygen by packaging or antioxidants.
Proteins - The biological value of protein is usually little affected by proper storage of food products. However, some slight loss may occur in dried foods if improperly stored. High storage temperature will cause certain amino acids (such as Iysine) of proteins to chemically bind with simple sugars (glucose) to form brown pigments. This is known as the "Maillard" or browning reaction and it occurs non-enzymatically. This browning reaction does affect the nutritional value of the food because it causes the essential amino acids in our diet to become physiologically unavailable. Improperly stored dried milk solids and egg white solids are particularly susceptible to this browning reaction. This reaction will also occur if poor packaging of dried foods allows an increase in moisture level.
Fats (lipids) - The nutritional value of fat lies in the energy supplied to the body during digestion and in the essential fatty acid (linoleic acid) also only supplied by the diet. Fats are fairly stable to processing (except frying), but may undergo quality deterioration during prolonged storage. Oxidative and hydrolytic rancidity occurs in stored food leading to off-flavor development. These reactions can be caused by enzymes or by moisture and air. They occur more rapidly under adverse storage conditions, but can also develop in properly stored fatty foods. For example, fat soluble Vitamins A, E, D, and K, and essential fatty acids are oxidized in frozen fried foods high in fat (French fried potatoes, pre-cooked fatty meats and fish). Fat (lipid) oxidation produces off-flavor compounds called "hydroperoxides" and other compounds called "peroxides" which read chemically with fat-soluble vitamins and linoleic acid, rendering them nutritionally useless. Loss of these nutrients can be minimized by wrapping foods in moisture proof and oxygen impermeable packaging materials, avoiding fluctuating frozen temperatures and utilizing food products within a reasonable time period.
Carbohydrates - Compared to sensitive nutrients such as vitamins, food carbohydrates are relatively stable to processing and storage. There is no significant loss in the nutritional value of carbo-hydrates in frozen, canned or dried foods. In fact, some carbohydrates are made more digestible through processing thus become more nutritionally available. Complex carbohydrates and starch are converted into simpler sugars. Most changes in canned food occur when sugars are leached from the food to the canning medium (water, syrup, etc.). Adverse brown pigments occur in some frozen and dried foods when carbohydrates react with proteins or when they are dehydrated as is the case in "freezer burn." This affects the sale of the product more than the nutritional value.
Elements - The elemental content of food is stable to processing although some leaching of salts into the brine occurs during canning. Actually, the mineral content of stored food is normally higher due to additives (sodium and calcium salts) used in processing. One element which appears unstable is iodine and evidence shows substantial quantities of iodine are lost from frozen fish.
Moisture - Changes in the moisture content of dried and frozen food can affect the nutritional quality of the food. Increases in moisture of dried food will promote microbial deterioration (molding) and accelerate rancidity of fats and fat-soluble vitamins such as Vitamin A. Improperly wrapped frozen food can suffer "freezer burn" which is a dehydration of moisture from the food's surface. This loss of moisture will cause fat oxidation and browning reactions to occur, resulting in off-flavor and off-color. Additionally, it will lower the nutritional value of the food because of the oxidation of Vitamin C and A. Freezer burn will cause the unavailability of certain amino acids.
Fiber - Although processing causes water-insoluble fiber of fruits and vegetables to become more soluble, there are no appreciable decreases in fiber content of frozen or canned products in storage.
Storage Tips for Specific Food Classes
Meats are considered perishable foods. Maximum shelf life can be achieved by placing them in a refrigerator at 32 to 35 degrees F immediately after receipt. Wrap raw meat loosely to allow for air circulation. Wrap leftover cooked meat tightly. Hold frozen meat at a maximum temperature of 0 degrees F to -18 degrees F to preserve quality and shelf life. Wrap meat tightly in moisture proof paper, or place it in moisture-proof containers before freezing to avoid the brownish condition known as freezer burn. Ham, bacon, and processed luncheon meats are high in fat and develop rancidity during long term frozen storage, so use them quickly.
Poultry must be wrapped loosely and refrigerated at 32 to 35 degrees F to maintain its quality. Fresh poultry is highly perishable and its shelf life will depend on its age. Giblets and cut-up pieces of poultry will deteriorate more rapidly than whole birds. Properly wrap poultry in moisture proof paper and hold at a maximum temperature of 0 degrees F to -18 degrees F after freezing to extend its shelf life.
Eggs are considered semi-perishable because of their natural inhibitor to deterioration, the intact shell. Temperatures of 40 degrees F to 45 degrees F are adequate for egg storage, although 32 degrees F to 35 degrees F will not harm them. Leave eggs in trays with the covering over them to prevent dehydration, grade and quality loss on long term refrigerator storage. Package dried egg solids (whites and yolks) in moistureproof and oxygen proof paper to prevent browning discolorations.
Fish Products are highly perishable. Hold fresh seafood at 32 degrees F to 35 degrees F and cover with crushed ice to keep it moist. Wrap seafood (fish products) in moisture proof paper and hold at a maximum temperature of 0 degrees F to -18 degrees F after freezing to extend its shelf life.
Dairy Products are perishable foods. Hold them at 32 degrees F to 35 degrees F for maximum shelf life. Most dairy products readily absorb strong odors from certain fruits (peaches), vegetables (cabbage, onions) and fish. For this reason keep dairy foods tightly covered when stored with these strongly flavored products. Cottage cheese, sour cream, whipping cream, etc., generally have a shorter shelf life than fluid milk. Tightly wrap cheese in oxygen and moisture proof paper during refrigerated storage to keep it from molding. Package dried milk solids in moisture and oxygen proof paper to prevent browning discolorations during storage.
Bakery Products are considered semi- perishable foods be-cause they are fairly low in moisture (30 to 40%). They are not usually refrigerated. Cakes, pies, cookies and breads, however, will develop rancid off-flavors if held at high room temperatures. Bakery products freeze well. To extend shelf life of bakery products, wrap tightly in oxygen and moisture proof paper and store at a maximum temperature of 0 degrees F to -18 degrees F after freezing.
Fruits and Nuts - Most ripe fruits keep best in the refrigerator. There are some, however, which can suffer cold damage if held at refrigerator (32 degrees F to 35 degrees F) temperature. This will result in physiological disorders of the tissue such as browning, softness, and accelerated decay. Fruits which should not be held at refrigerated temperatures (but at temperatures ranging between 45 degrees F and 60 degrees F) include lemons, limes, mangoes, papayas, honeydew melons, grapefruit, and avocadoes. Protect these fruits from low temperatures by storing them in the warmest section of a walk-in cooler or refrigerator and by insulating them in paper bags, insulated containers, etc.
Do not refrigerate bananas but hold them at 60 to 65 degrees F. Humidity is important in the storage of fresh fruits. High humidity (85 to 95%)prevents fruit wilting and loss of nutritional value. To raise the humidity level, sprinkle fruits with water and store in polyethylene food storage bags until used. Don't sprinkle berries, grapes or cherries and then seal in bags, because the surface moisture will increase the likelihood of mold growth on these products. Nuts (pecans, peanuts, etc.) can best be stored at refrigerated temperatures (32 to 35 degrees F). However, they are susceptible to molding and rancidity development if stored at humidities higher than 70%. To keep humidity low, store nuts in moisture proof bags or containers in the refrigerator. Both fruits and nuts can be frozen. Shelf life will be pre-served by holding at a maximum temperature of 0 degrees F to -18 degrees F after freezing. Store these products in moisture proof and oxygen proof bags or containers to prevent dehydration and discolorations during frozen storage.
Vegetables - Most fresh vegetables keep best under refrigeration (32 to 35 degrees F). The exceptions are snap beans, bell peppers, ripe tomatoes, summer squash, watermelons, and okra, which should beheld at 45 degrees F. Hold cucumbers, eggplant, pumpkins, sweet potatoes and winter squash at 55 degrees F. Both of these groups of vegetables will be cold damaged if held at refrigerator (32 to 35 degrees F) temperatures for very long. Protect these vegetables from low temperatures by storing them in the warmest section of the cooler and insulating them in paper bags, etc. Never refrigerate green tomatoes, since low temperature (less than 55 degrees F) will prevent ripening. Humidity control is important in the storage of fresh vegetables. Most vegetables require a high humidity (85 to 95%) to prevent shriveling (especially leafy vegetables), loss of nutritional value and accelerated decay. The humidity level may be increased by sprinkling vegetables with water and storing them in polyethylene food storage bags until used. Dry bulb onions (such as Vidalias) and garlic store best at refrigerated temperatures (32 to 35 degrees F). At 50 degrees F, sprouting begins and at 70 degrees F, decay accelerates in dry bulb onions. Both onions and garlic require low humidity (65 to 70%) storage to prevent molding and decay. Store these vegetables in moisture proof bags or containers in the refrigerator. Most vegetables must be adequately blanched before freezing to prevent the development of off-flavors, loss of color, and soft textures during frozen storage. Hold vegetables at maximum temperatures of 0 degrees F to -18 degrees F after freezing to preserve shelf life. Wrap vegetables in moisture proof and oxygen proof packaging to prevent freezer burn and discolorations during storage.
Canned foods - The two most important factors affecting the shelf life of canned foods (meats, fruits, vegetables, etc.) are temperature and humidity. Store canned goods at a tem-perature between 50 degrees F and 70 degrees F. At temperatures above 100 degrees F, thermo-philic spores will germinate. This microbial growth can cause reduced shelf life and reduced quality of the food. Store canned goods in a humidity between 50 to 60%. Higher humidity will cause external rusting of the can surface leading to can corrosion. Assuming proper storage conditions, acid canned foods (fruits) will have a longer shelf life than non-acid canned foods (meats, vegetables) because of the protective nature of the acid in the food itself.
Dehydrated foods (meats, fruits, vegetables) must be protected from high humidity, high temperature and air to avoid loss of shelf life. Storage temperature should be between 50 degrees F and 70 degrees F, and the humidity held between 50 to 60%. Tightly seal these dehydrated foods in moisture proof and oxygen proof packaging materials. Store them away from strong light to prevent loss in nutritional value.
Grains, Grain Products, Seasonings, Coffee and Tea are all considered shelf-stable foods provided they are stored properly. Use a storage temperature of 50 to 70 degrees F and humidity of 50 to 60% to maximize shelf life. Oxygen is especially harmful to coffee causing rancidity and loss of flavor. Vacuum packaging has enabled its quality to be prolonged. Grains and their products are favorite targets of insects and rodents. Keep these products covered and in durable containers. Keep the dry goods area clean, well-lighted and dry to prevent these vermin from gathering.
Frozen Convenience Foods must be packaged in moistureproof and oxygen proof containers and kept at maximum temperatures of 0 degrees F to -18 degrees F to maintain quality. One of the most serious problems in holding frozen convenience foods is fluctuating temperature during storage. This causes rancidity development in meat portions, loss of color and flavor in vegetable portions and loss of texture in sauces. Maintain a consistent frozen temperature for best shelf life.
Fats and Oils (such as shortenings and vegetable oils) should be kept wrapped or closed in bottles to prevent deterioration by air. Hold these items in a cool (50 to 70 degrees F) and dry (50 to 60%) place. Minimize time of exposure to light since it can accelerate rancidity development.
What Does Package Code Dating
Really Mean to Shelf Life?
Food shelf life varies with the age and type of ingredients, the process, the package, environmental conditions during distribution, and consumer holding. The food processor can control the first three factors to ensure the initial quality of the product, but the last two conditions are not within his or her control. The "freshness" or "quality" of food ultimately depends on existing distribution and marketing systems and consumer food storage habits. Following manu-facture, most food processors ship their products directly to regional distribution centers. From there the food is sold to food brokers or supermarket chains, who deliver the products to their regional terminal warehouses. At this point, the food moves to supermarket storerooms, then to the grocery shelf or display case and finally to the consumer's home (shelf or refrigerator) where it is further stored before consumption. All along this chain, temperature and humidity changes will cause abuse to food resulting in quality loss. So the shelf life of a food can only be accurately predicted if the exact temperature/humidity history profile of each package is known.
Two manufacturers could process the same type of food with the same quality criteria on the same day, yet not achieve the same shelf life if one manufacturer's product receives more abuse during distribution. The consumer at the point of purchase, however, will have no idea of the difference between these two foods since both will be labeled with the same date of manufacture. Thus such a date will not help in decisions regarding freshness. If the consumer selects the "more abused" food, it won't be apparent until he or she has opened the package or tasted the food at home. It is apparent that the product code date can't always be equated with its potential shelf life or freshness. Yet, food manufacturers use several types of dates which they put on packages to give consu-mers information about food freshness. These dates, however, are not used consistently on food products and therefore often confuse or mislead consumers. In an attempt to clear up their meanings and implications, the following dating systems used at the retail level are discussed.
Pack Date - Several food products have a pack date either stamped on the package (some bread and bakery items) or embossed on the container (canned soup). Many more food manufacturers use a "closed code" (coffee, seasonings, dried milk, canned foods, frozen foods) which is really a pack date but is understood only by the processor. The pack date tells the consumer only when the finished product was packaged and nothing about the specific age of the ingredients. Oranges, for example, are harvested over a short season, their juice extracted and frozen at low temperature (-20 degrees F) for up to a year before being concentrated and packaged for sale as frozen orange juice. Assuming proper storage conditions, there would be little affect on quality, but obviously the pack date on the frozen orange juice is not an accurate indication of the actual age of the juice. The major drawback with a pack date, however, is that it does not say anything about the loss in quality which may occur during distribution, nor does it tell the consumer or grocer how long the product will retain its high quality. Thus, the pack date could be most useful to grocery stock personnel to monitor inventory and rotate new stock to replace the old on grocery shelves, since it would be easier to read a date than a closed code.
Sell-by-Date - Many food manufacturers place a "sell-by" date on the food product package (milk, fresh poultry and meats, dairy products, eggs, corn oil, margarine, prepared salads) which indicates the last date the product should remain on the grocer's shelf, on the assumption that by then there is a significant loss in quality. Many consumers are confused as to the fitness and safety of food products bearing sell-by dates, especially if they are purchased near or on the date itself. "Is the product safe to eat?" or "Will it become spoiled or unsafe if it is held two more days?" are questions frequently asked by consumers. Most food manufacturers have included a 7 to 10 day home storage period in determining their product sell-by date. This means the product should remain at acceptable quality this period of time after the sell-by date has expired, assuming proper home storage. Some food processors indicate this on the package by words such as "Good For 10 Days Beyond Date Stamped." In determining this date however, the processor must take into account the worst possible conditions during distribution.
Use-by Date - The straight forward approach of some food processors is to stamp a "use-by date" on the package. Unfortunately, this implies the food becomes inedible or unsafe once the date has been exceeded, which may or may not be true depending on conditions during storage and distribution. Thus, the date is misleading and confusing to consumers. Foods properly handled during distribution would be safe and nutritious long after their use-by date. On the other hand, if the use-by date were ignored by the grocer and consumer, quality would be lost gradually over time. Again, the determination of a food product use-by date requires careful study by the manufacturer. Generally, food processors presume the worst possible shipping and holding conditions the product might encounter when choosing a specific use-by date for each food (cheese, mayonnaise, pizza, fresh orange juice, etc.). Actually, many of the food products on grocery shelves will still be of high quality even though the use-by date has expired. This system can also be confusing to the grocer, who removes past-date food to a special store location and sells it at a lower price.
Best-if-used-by Date - "Best-if-used-by dates" are now being used on several food products (snack foods, breakfast cereals, baby food, luncheon meats, salad dressings, butter and rice products).This term eliminates some of the confusion inherent in the "sell-by date," by implying that the product is still usable after the date shown, but probably of decreasing quality. In establishing such a date, the food manu-facturer must consider not only factors such as processing, storage, and distribution (which affect product quality), but also home handling practices over which he or she has no control. Thus, because of the almost infinite number of adverse conditions a package may experience, it is apparent that to accurately predict the exact shelf life of a food product is impossible! Consequently, no matter which date food processors use, consumers still have to take a chance in their purchase. Yet, the best-if-used-by date appears to give the consumer the most useful information, especially if it is accompanied by information on proper home storage conditions, such as "full freshness beyond date stamped on package when stored at 40 degrees F" (bacon). A modification of the best-if-used-by date is that of "Guaranteed fresh for seven days beyond date stamped on package" (flavored potato chips). This statement gives food brokers and grocers the "sell-by date" they want and a date for consumer guidance. Without this addition, grocers could be confused as to when and if they should remove or segregate open dated products. A national survey has reported that consumers would like to have a combination of two dates, "pack" and "best-if-used-by date" as well as information on home storage conditions. At present there are no federal labeling regulations which require this information to be printed on food packages or products.
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