4 color EXTENSION Black/PMS 186 EXTENSION EC446 Food Storage Julie A. Albrecht, Extension Food Specialist Black EXTENSION Proper food storage helps maintain food quality How Food Spoils by retaining flavor, color, texture and nutrients, while reducing the chance of contracting a foodborne illness. Food spoilage and deterioration is no accident. It is a Foods can be classified into three groups. The first naturally occurring process. To understand how to main- group, perishable foods, includes meat, poultry, fish, tain the quality of food and prevent spoilage, we need to milk, eggs and many raw fruits and vegetables. All know what can cause spoilage. cooked foods are considered perishable foods. To store these foods for any length of time, perishable foods Microorganisms need to be held at refrigerator or freezer temperatures. Many types of microorganisms can cause food If refrigerated, perishable foods should be used within problems. The microorganisms that can cause foodborne several days. illness are called pathogenic microorganisms. These Semi-perishable foods, if properly stored and microorganisms grow best at room temperatures (60- handled, may remain unspoiled for six months to about 90oF), but most do not grow well at refrigerator or freezer one year. Flour, gain products, dried fruits and dry mixes temperatures. Pathogenic microorganisms may grow in are considered semi-perishable. foods without any noticeable change in odor, appearance or taste. Spoilage microorganisms, including some kinds Staple, or non-periabable, foods such as sugar, dried of bacteria, yeasts and molds, can grow well at tempera- beans, spices and canned goods do not spoil unless they tures as low as 40oF. When spoilage microorganisms are are handled carelessly. These foods will lose quality, how- present, the food usually looks and/or smells awful. ever, if stored over a long time, even if stored under ideal conditions. Enzymes There is no exact method to determine how long Enzymes. substances naturally present in food, a food will maintain quality and be safe to eat, because are responsible for the ripening process in fruits and many conditions affect quality. The storage life of foods is vegetables. Enzymes are responsible for texture. color affected by: and flavor changes. For example, as a banana turns • the freshness of the food when it reached the from green to yellow to brown, not only does the color grocery store. change, but there is also a change in the fruit’s texture. Unblanched frozen corn-on-the-cob may taste like the • the length of time and the temperature at which it cob over time. This is the result of enzyme action. was held before purchase. • the temperature of your food storage areas. Air • the humidity level in your food storage areas. Oxidation, a chemical process that produces un- • the type of storage container or packaging the food desirable changes in color, flavor and nutrient content, is stored in. results when air reacts with food components. When fats in foods become rancid, oxidation is responsible. Discol- • the characteristics of the food item. oration of light-colored fruits can be reduced by using an Extension is a Division of the Institute of Agriculture and Natural Resources at the University of Nebraska–Lincoln cooperating with the Counties and the United States Department of Agriculture. University of Nebraska–Lincoln Extension educational programs abide with the nondiscrimination policies of the University of Nebraska–Lincoln and the United States Department of Agriculture. © 2007, The Board of Regents of the University of Nebraska on behalf of the University of Nebraska–Lincoln Extension. All rights reserved. antioxidant, such as ascorbic acid or citric acid, before food items will help maintain the rotation system. freezing. Vapor-proof packaging that keeps air out helps Check canned items frequently for signs of spoilage. reduce oxidation problems. Do not use food from cracked, bulging or leaking cans, or those that spurt liquid when opened. Never taste these Light foods to determine their safety, but discard the cans im- Light exposure could result in color and vitamin mediately. loss. Light also may be responsible for the oxidation of fats. Refrigerated Storage Insects, Rodents, Parasites and Other Creatures Refrigerator temperatures do not destroy pathogenic These creatures require food to survive and damage or spoilage microorganisms. The lower temperature does, food, making it more vulnerable to further deterioration. however, slow the growth of microorganisms already in the food. Perishable food will deteriorate, even at Physical Abuse refrigerator temperatures, due to spoilage microorgan- Bruises and cracks on raw produce leave areas where isms, enzymes and oxidation. Time and temperature are microorganisms easily may grow. Improperly packaged important factors in food quality. foods, dented cans and broken packages provide places Use food quickly, and don’t expect food to remain for microorganisms, air, light and creatures to enter. high-quality for the maximum length of time. Opened Gentle handling of food items will help maintain food and partially used items usually deteriorate more quickly quality and safety longer. than unopened packages. o o Temperature Maintain your refrigerator between 34 F and 40 F. Refrigerator thermometers are available to help monitor Temperature affects storage time, and food dete- the temperature inside the appliance. riorates faster at higher temperatures. Recommended temperatures for storage areas are: Foil, plastic wraps or bags or airtight containers are the best choices for storing most foods in the refrigerator. o Cupboard/Pantry 50-70 F Open dishes may result in refrigerator odors, dried-out o Refrigerator 34-40 F foods, loss of nutrients and mold growth. Freezer 0oF or below Food placement in the refrigerator affects air circula- Microorganisms, both spoilage and pathogenic, tion and efficiency. Don’t stack foods tightly or cover grow rapidly at room temperature. To slow microbial refrigerator shelves with foil or any material that prevents growth, the enzymatic and oxidation processes, store air circulation from quickly and evenly cooling the food. foods at lower temperatures. Some foods, including milk, meats and leftovers, Time should be kept colder than others. The coldest part of the refrigerator is usually the area nearest the freezer com- Microorganisms need time to grow and multiply. partment, but a refrigerator thermometer will provide an Other reactions, such as oxidation and enzyme action, accurate check for each appliance. also require time to develop. Purchase reasonable quanti- ties. especially of perishable foods, to help avoid long Freezer Storage term storage. Keep your freezer at zero degrees or below to Cupboard/Pantry Storage maintain the quality of frozen foods. Most foods will maintain good quality longer if the freezer temperature o o Cupboard or pantries should be kept clean. dry, dark is -10 to -20 F. At temperatures between 0 and 32 F, food and cool. The best temperature range for dry and canned deteriorates more rapidly. Fluctuating temperatures, such items is 50-70oF. Temperatures over 100oF may cause as those in self-defrosting freezers, also may damage canned food to deteriorate and lose quality. food quality. Do not plan to store frozen foods for the maximum suggested time if your freezing unit cannot To prevent foods from spoiling, use a rotation maintain zero degree temperatures. Even foods stored system — FIRST IN, FIRST OUT. By using this method, properly will lose color, texture, flavor and nutritional older canned and dried food items will be used before quality but will not cause foodborne illness. newly purchased items. Writing the date of purchase on 2 © The Board of Regents of the University of Nebraska. All rights reserved. Freezer temperatures, however, do not destroy unplugged, leave the door open for a day or two to pathogenic or spoilage microorganisms, which will begin air it out. If the odor remains, try one of the following growing under warmer temperature conditions. When methods: frozen foods are thawed at room temperature, the sur- • Place trays of activated charcoal, clean kitty litter face of the food warms enough for microorganisms to or baking soda on the shelves of the refrigerator or grow and multiply. freezer. Run the appliance empty for two or three If your freezer does not have a built-in thermometer, days. Activated charcoal can be purchased from check the temperature frequently. One easy way to esti- stores that sell aquarium and terrarium supplies. mate the freezer’s temperature is to check the consistency • Place freshly ground coffee on cookie sheets in the of ice cream stored inside the compartment. If the ice refrigerator or freezer and close the door. Again, cream is not brick-hard, the temperature of your freezer run the appliance empty for two or three days. A is too warm. A warning light or other device may be slight coffee odor may remain, but will disappear installed to warn you if the freezer is not operating cor- after washing and rinsing. rectly. A plug protector may be used to keep the electrical plug in the outlet. • Pack each refrigerator or freezer shelf with crumpled newspaper. Set a cup of water on the top Time is an important factor in maintaining shelf or sprinkle the newspaper with water. Allow high-quality frozen foods. Frozen foods will not last the refrigerator or freezer to run for approximately forever. The chart at the end of this publication lists the five or six days. This method is time consuming, maximum length of storage times to help you maintain but effectively removes strong odors. quality food products. One option is to label frozen food items, maintain a rotation system and use the items with • Several commercial products are available for the oldest dates first. removal of refrigerator and freezer odors. These products may be purchased at hardware, grocery, Many products. including foil, plastic wrap or bags, discount and variety stores.