Why food deteriorates

Doyle, M. A New Generation of Foodborne Pathogens. Dairy Food Environ. Desrosier, N. Technology of Food Preservation. AVI Publishing Co. Gould, W. Tomato Production, Processing and Quality Evaluation. Guthrie, R. Food Sanitation. Jarvis, B. Progress in Industrial Microbiology. Statistical Aspects of the Microbiological Analysis of Foods.

Elsevier Science Publishers, New York. Jay, J. Microbiological food safety. Food Sci. Modern Food Microbiology. John, G. Objective Methods in Food Quality Assessment. King, P. If these types of products are frozen, the emulsion will be destroyed and the fat and water will separate into distinct layers.

Fruits and vegetables that are allowed to freeze and then thaw will have their texture disrupted. The texture of canned fruits and vegetables becomes softened and mushy due to uncontrolled freezing, also called as chilling injury. B Many fruits and vegetables, like other living systems, have optimum temperature requirements after harvest.

This provides an exception to the inaccurate generalization that cold storage preserves all foods, and the colder the better.

High Temperature. There is a moderate temperature range over which much of the food is handled, i. Excessive heat treatment results into denaturation of proteins, breakage of emulsions, drying out of foods by moisture removal, and destruction of vitamins.

A Excessive heat treatment in green vegetables causes loss of integrity of cell walls and membranes with release of acids and enzymes. This results in the softening of texture as well as the development of off-colors and off-flavors.

B The consequences of excessive heat on muscle tissue leads to denaturation and clumping of proteins, and enzyme inactivation. This results in a toughening of the texture, loss of water holding capacity, cooked or caramel flavors, and development of off-colors. Dehydration, is another form of physical change that causes food deterioration. It can be defined as the loss of water from the food product.

Foods, especially fresh, chilled, and frozen, are subject to dehydration. Foods contain a substantial amount of water. Since water vapor is continually seeking to go from an area of high concentration to an area of low concentration, improper storage conditions and improper packaging will lead to dehydration.

Dehydration results when the humidity is too low in a storage area. The signs of dehydration include dryness or shriveling on the surface of the food item, development of off-colors, with usually a darkening effect. In frozen foods, the dehydration is known as freezer burn, whereas in fresh fruits and vegetables, it is known as wilt. Mechanical Damage. When any food item receives mechanical damage, not only is the appearance of the item affected but the damaged food tissue also becomes more susceptible to other forms of deterioration.

Such foods become more susceptible to invasion by microorganisms, for the damaged area serves as a port of entry. The cell walls of foods are also destroyed by mechanical abrasion, and the inherent enzymes in the food product are liberated from the cells. Once liberated, the enzymes begin the process of deterioration or, more specifically, autolysis.

The notable changes would be a softening in the texture, development of off-colors, and development of off-flavors. Freezer burn is a deteriorative condition commonly found in frozen foods, especially poultry, water foods, and red meats. This condition is a physical change in the food item that results in no loss of wholesomeness. Abnormal Characteristics. The abnormal characteristics that are exhibited by a freezer-burned product include an abnormal color, usually white or pale amber.

The surface of the product will be dry and shriveled, and usually a buildup of frost on the surface of the product, the texture similar to that of a dry sponge. Cause of Freezer Burn. Freezer burn is caused by the evaporation sublimation of moisture from the surface of the food item which results in the product having a bleached, unattractive appearance and adverse effects on the palatability.

A Dehydration. In a freezer, the relative humidity is low because the cold dense air is not capable of holding much moisture. This uneven concentration of moisture makes frozen foods very susceptible to moisture loss, hence the products which are improperly wrapped and packaged will be susceptible to dehydration resulting in a freezer burn. B Colour change. Chemical hazards are natural and man-made substances that may be present in the food at high concentrations resulting in food poisoning.

Physical hazards are extraneous material that may fall into the food during harvesting and processing such as glass, metal and stones that may lead to cuts and other injury while eating. Food companies may also set their own food safety standards as long as they are not lower that the standards set by the appropriate regulatory agency.

Food quality problems may include food safety issues but is much broader. Bread goes moldy due to the presence of mold in the environment where it is processed or stored. Mold spores can be easily carried by air. When they land on your bread they will grow as long as they have enough moisture and nutrients.

To prevent mold growth, breads must be processed in a clean environment and must be cooled prior to packaging.

Storing your bread in a clean environment and resealing the bag after opening will reduce the risk of contamination. Most commercial breads on the market are made with mold inhibitors such as calcium and sodium propionate, sorbic acid and potassium sorbate, benzoates, acetic acid and prune juice. Hence bread molding is more of a problem when you make homemade bread. If you have to make bread at home and want to keep it for longer, it is best to freeze it.

Breads go stale due to a process called retrogradation. In this process, amylose molecules in the starch bond to each other, forcing water out from between them. This leaves the firm and crumbly texture characteristic of staling.

To reduce staling, food manufactures add dough conditioners such as emulsifiers to bind amylose and hence restrict their movement. 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. 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.