Food spoilage and its effects on nutrient

Introduction

The diet of many people is supplemented with food items preserved by special method and available in a variety of conditions and stages of preparation. Such food may be frozen, canned or dehydrated; it may be partly or completely baked or pre-cooked, reading for heating and serving. During preparation, heterotrophic microorganism for meeting their nutritional requirement can attack such food. The unrestricted growth and multiplication of these microorganisms in food may render it unfit for consumption and can result in spoilage or deterioration.

Definition of food spoilage

Food spoilage means the original nutritive value texture, colour, flavor of the food are damaged, due to the activities or action of microorganism, insects and enzymes which become harmful and unsuitable to eat.

Food spoilage can also be defined as the undesirable change occurring in food due to the influence of air, light, moisture, which fosters the growth of microorganism. Food takes different period of time to lose their natural form through spoilage. In context to food preservation, foods are classified as perishable (meat, fish, milk, fruit and some vegetable), semi perishable (eggs, onions, potatoes, carrot, beans) and non perishable (cereals, pulse, nuts).

Types of food spoilage

1. Putrefaction
2. Fermentation
3. Rancidity

Putrefaction: This is the decomposition of organic matter particularly the anaerobic (absence of oxygen) breakdown of protein by bacteria, with the production of foul smelling compound. The decomposition of complex nitrogen containing organic compound (primarily protein) caused by the action of putrefaction microorganism. Because putrefaction is accompanied primarily by the evolution of gaseous ammonia, putrefaction is also called ammonifaction and the microorganism involved in the process are called ammonifiers

Fermentation: This refers to the breakdown of carbohydrate with the fermentation of acid (latric), alcohol, carbon dioxide by the action of specific enzymes called ferments, produce by minute organism such as mould, bacteria and yeast. For example, lactase ferment produced by bacteria usually found in milk cause the milk to sour by changing lactose (milk sugar) into lactic acid

Rancidity: This is the chemical decomposition of fats and oil which result in the production of unpleasant odour and flavours. There are three types of rancidity and microbial rancidity

1. Hydrolytic rancidity occurs when triglycerides go through the process of hydrolysis, breaking them down into their fatty acid and glycerol.
2. Oxidative rancidity is caused by oxidation in unsaturated oil or fats. When these types of oil or fats are exposed to oxidation, they begin decomposing into short chain fatty acid such as bulyric acid which give the fats a rancid taste
3. Microbial rancidity is caused by bacteria breaking down fat with enzymes causing the fat to decompose.

Causes of food spoilage

1. Growth and activities of microorganism
2. Activities of enzymes
3. Action of insect and pest
4. Purely chemical reaction
5. Mechanical damage

1. Growth and activities of microorganism

This is brought about as a result of the development and biochemical activities of microorganism. The microorganisms responsible for food spoilage are mould, yeast and bacteria.

• Mould: Moulds are in the form of threads developed on perishable foods and are easily visible to the eyes. They contain spore which can spread through the air and start new mould plants. When these moulds find a favorable environment, they germinate and produce a puffy growth, often white or grey but sometimes bluish – green, red, orange or some other colour depending on the variety of the mould
• Yeast: Yeasts are tiny organism which are not visible to the naked eyes, but which can be seen through the microscope. They multiply very fast and cause fermentation by acting on certain components of the perishable food like fruit juice, syrups etc.; during yeast fermentation, the sugar present in the food are broken up to form alcohol and carbon dioxide. Foods liable to be spoiled by yeast are fruit juice, syrups, molasses, honey, jams and jellies
• Bacteria: Bacteria are unicellular organism and are much smaller in size than either yeast or mould. They occur in different size than either yeast or mould. They occur in different sizes and shapes and are classified as coccus (spheroidal), bacilli (cylindrical) or spirilae (spirilla) on the basis of their shape as seen under the microscope. They are also in their requirement for food, moisture, acidity, temperature and oxygen. Bacteria can grow and develop rapidly between and 53^o bacteria are classified according to the temperature ranges that they need for growth. We have mesophile with the temperature between 20^o­C – 37^o­C, the psychophile with the temperature between 0^o­C – 20^o­C

2. Activities of enzymes

Enzymes are biological catalyst which speeds up the rate of specific chemical reaction without undergoing changes at the end of the reaction. The life of every living cell depends upon the chemical reaction. Enzymes in a tomato help it to ripen and enzymes produce by the tomatoes, if not slow down or stop may cause the tomatoes to over ripe and lead to spoilage

3. Action of insect and pest

Insect like weevil, bugs, fruit flies, moth cause extensive damage to food and reduce its nutritional value and make it unfit for human consumption

4. Mechanical damage

During the harvest and transport they can sustain injuring and this lead to entrance of microorganism which cause food spoilage.

5. Purely chemical reaction

These are reaction not catalyzed by enzymes. Non enzymes bowing or mallard reaction is of importance in food manufacturing and its result can either be desirable or undesirable. The brown discoloration of evaporated and sterilized milk and oxidative, acidity of fat are undesirable

Signs of food spoilage

Signs of food spoilage may include an appearance different from the food in its fresh form. Such as:

1. Change in colour
2. Change in temperature
3. An unpleasant odour or undesirable taste
4. The item may become softer than normal

The effects of spoilage on nutrient

Spoilage destroys the nutritional value of the food and cause food poisoning when consumed. Sometimes it is difficult to draw line between spoilage by microorganism and harmless growth, or the same type of change may be considered undesirable in one and desirable in another. Thus, the home maker say that sour milk has spoiled, but the cultured buttermilk made by a lactic acid. Fermentation is good. Putrefaction in meat means definite spoilage. Proteinases catalyze the hydrolysis of protein to peptides, which may give a bitter taste to food. Peptidase catalyze the hydrolysis of polypeptides to simpler peptides and finally to amino acid which give flavor to some foods.

Prevention of food spoilage

1. Drying and dehydration
2. Use of preservatives
3. Heat treatment
4. Irradiation
5. Cold treatment

Drying and dehydration

The term drying and dehydration arte applied to the removal of water from food. To the food technologist, drying refers to natural desiccation such as by spreading fruit on track in the sun. Removal of water causes of food spoilage. Microorganisms cannot grow and most chemical reactions are greatly referred

Dehydration is defined as the application of heat under control conditions to remove majority of the water normally present in foods. The main purpose of dehydration is to extend the shelf life of the food by reduction in water activity. These inhibit microbial growth and enzyme activity but the processing temperature is usually insufficient to cause their inactivation.

Use of preservatives

Preservatives have been defined as any chemical which when added to a food tends to prevents or retard its deterioration. They are used to control spoilage microorganisms or chemical deteriorative processes or insect and rodent attacks. Chemical preservatives must be safe for consumption and not carcinogenic, example of such chemicals are sodium benzoate, ascorbic acid, sodium and calcium propionate

Heat treatment

Preservation of food by heat destroys most spoilage microorganism and natural enzymes present in the food. There are various ways of heat treatment which include bleaching, sterilization and pasteurization.

Irradiation

Irradiation is the process by which energy in form of light or heat is emitted from molecules and atoms as a result of internal changes. Radiation substances exist in nature but they can artificially induce. Certain electromagnetic radiation destroys microorganism and food enzymes

Cold treatment

Low temperature preserves food by retarding chemical reactions, enzymatic action and growth and activity of microorganism. The use of low temperature below freezing and generally stops at freezing temperature are: chilling, freezing and refrigeration

Conclusion

In conclusion, spoiled food cannot be rectified by any processing method. It results in wastage and food poising when consumed. To prevent spoilage and ultimately wastage, any surplus food should be processed and preserved immediately

References

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