Know how. Know now.
From border to border in Nebraska, UNL Extension is making an incredible impact on the success of our state — its youth, its families, its farms and ranches, its communities, its economy. Please check these websites for more "know how, know now" information.
How Food Spoils
Food spoilage and deterioration is no accident. It is a naturally occurring process. To understand how to maintain the quality of food and prevent spoilage, we need to know what can cause it. Factors that affect food spoilage include:
- Insects, Rodents, Parasites and Other Creatures
- Physical Damage
Many types of microorganisms can cause food problems. The microorganisms that can cause food-borne illness are called pathogenic microorganisms. These microorganisms grow best at room temperatures (60-90°F), but most do not grow well at refrigerator or freezer temperatures. Pathogenic microorganisms may grow in foods without any noticeable change in odor, appearance or taste. Spoilage microorganisms, including some kinds of bacteria, yeasts and molds, can grow well at temperatures as low as 40°F. When spoilage microorganisms are present, the food usually looks and/or smells awful. Read more about pathogenic microorganisms under Food Poisoning/Foodborne Illness►
Enzymes, substances naturally present in food, are responsible for the ripening process in fruits and vegetables. Enzymes are responsible for texture, color and flavor changes. For example, as a banana turns from green to yellow to brown, not only does the color change, but there is also a change in the fruit’s texture. Unblanched, frozen corn-on-the-cob may taste like the cob over time. This is the result of enzyme action.
Oxidation, a chemical process that produces undesirable changes in color, flavor and nutrient content, results when air reacts with food components. When fats in foods become rancid, oxidation is responsible. Discoloration of light-colored fruits can be reduced by using an antioxidant, such as ascorbic acid or citric acid, before freezing. Vapor-proof packaging that keeps air out helps reduce oxidation problems.
Light exposure could result in color and vitamin loss. Light also may be responsible for the oxidation of fats.
Insects, Rodents, Parasites and Other Creatures
These creatures require food to survive and damage food, making it more vulnerable to further deterioration.
Bruises and cracks on raw produce leave areas where microorganisms easily may grow. Improperly packaged foods, dented cans and broken packages provide places for microorganisms, air, light and creatures to enter. Gentle handling of food items will help maintain food quality and safety longer.
Temperature affects storage time, and food deteriorates faster at higher temperatures. Recommended temperatures for storage areas are:
- Cupboard/Pantry 50-70°F
- Refrigerator 34-40°F
- Freezer 0°F or below
Microorganisms, both spoilage and pathogenic, grow rapidly at room temperature. To slow microbial growth, the enzymatic and oxidation processes, store foods at lower temperatures. Read more about microorganisms and temperatures.
Microorganisms need time to grow and multiply. Other reactions, such as oxidation and enzyme action, also require time to develop. Purchase reasonable quantities, especially of perishable foods, to help avoid long-term storage.