Food Spoilage and Preservation

Food security is a situation that exists when all people, at all times, have physical, social and economic access to sufficient, safe and nutritious food that meets their dietary needs and food preferences for an active and healthy life”. This definition of food security was adopted at the 1996 World Food Summit.

Simply put, food security is the state of having reliable access to a sufficient quantity of affordable, nutritious food. There are several angles to food security but I would like to focus on preservation of food and preventing spoilage. It is important to note that a nation may do all it can to store food, but if the right parameters for storage is not applied all that have been stored would go waste due to spoilage.

Food Spoilage

Spoilage is the process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced. This means the original nutritional value, flavor and texture of the food are damaged and hence unsuitable for human consumption. In many cases food becomes harmful to consume when spoilage sets in. Spoilage results from several extrinsic and intrinsic factors and it is important these factors are well known in order to forestall this phenomenon.

It is very common to come across tomatoes and heaps of fruits that have gone to waste due to spoilage. Spoilage commences immediately after harvesting, slaughtering or fishing. It is with this mindset that preservation techniques must be explored, tested and adopted before the process of planting, rearing of animals or even fishing begins. The President’s idea of revamping agriculture is a laudable one.

We should not start large scale agriculture and harvest tons of produce before we begin to think of how to preserve those that are not readily procured by customers and consumers. Factors influencing the rapid deterioration of perishable goods must be understood to give direction to the best storage methods. Spoilage may arise due to the activities of bacteria, moulds, yeasts and pests.

Microorganisms like human beings survive by feeding. They require carbohydrates, proteins, fats and vitamins. There are some bacteria that require oxygen to grow, others do not need oxygen at all, whilst others can grow in the presence or absence of oxygen. When these organisms are given the opportunity to grow they release byproducts from biochemical reactions and these may be toxins or odoriferous chemicals which makes food unfit for consumption.

Particular enzymes produced by bacteria, moulds and yeast cause ripening and hence facilitates spoilage. Pests like rodents, weevils, flour moths and beetles have the capacity to cause damage to food and introduce microorganisms as well. For instance, the urine of rodents is poisonous to the human body.

We’ve already outlined the fact that food must be preserved in order to save it from the activities of spoilage organisms. There are several preservation techniques that could be adopted.

Food Preservation

Food preservation is the process of treating and handling food to stop or slow down food spoilage, loss of quality, edibility, or nutritional value and thus allow for longer food storage microorganisms. There are several techniques that can be employed both domestically and industrially to preserve food. These methods can be grouped into categories. Low and high temperatures, dehydration, chemicals, controlled atmospheres, fermentation and other physical methods are used to preserve food.

Low and High Temperatures

Temperature is a key parameter employed in food preservation. Pasteurization has been used to preserve so many foods and still continues to be used. It is important to note that, for longer storage of food, pasteurization has to be used in conjunction with refrigeration or freezing to prevent microbial spores from regenerating. Fresh vegetables, fruits and ready-to-eat foods can be preserved in a refrigerator at a temperature of 1 – 4oC.

In order to preserve products for several weeks or months, storage in a deep freezer is recommended. Remember to keep the temperature of the freezer at -18oC at all times. Certain foods have high doses of mould spores and pathogens and these need very high temperatures to preserve them. Milk preserved in tins for example has to undergo sterilization at a temperature of 121oC for 2-3 minutes whilst most spices undergo ultra-heat treatment (UHT) at a temperature of 135oC for 1sec. It is possible to reduce the quantum of tomatoes that go waste to the barest minimum if we can employ canning

Chemical Preservation

Chemical preservation is one of the oldest methods used in the preservation of all kinds of food products. Salt is one key preservative used in preserving a lot of foods including fish and meat. Some vegetables are also well preserved in salt. There are other chemicals such as nitrates or nitrites for the curing of meat. These helps retain the colour of meat and also reduces the rate of spoilage to the barest minimum. Pickling or acidification is another chemical method employed in preservation of food.

Moisture reduction/Smoking

Moisture reduction can be applied in many forms. The most popular technique in moisture reduction is sun-drying. Traditionally maize, cereals, cocoa beans and others are sun-dried as a means of preservation. These food items can be preserved for several years through this method. In fact, a combination of sun-drying and chemical methods has been known to preserve grains for many years.

Signs and Spoilage

For the purposes of consumer safety, it is imperative for consumers and owners of food businesses to ascertain when spoilage has set in. In the case of consumers, it helps prevent consumption of food and for business owners, it prevents the sale of contaminated food. Some bacteria are both pathogens and spoilage organisms. The reason why food must not be eaten when spoilage has set in. The following are some signs of spoilage; off odours and dicolouration. Examples of food which can give these characteristics are fish, meat and vegetables. Another sign of spoilage is slime or stickiness and these presents themselves clearly in meat and fish. Fruits and vegetables would show mould presence. Texture change in fish, meat, vegetables and creams is an indication of spoilage. In many instances, there is deterioration of taste and this reveals itself in foods like milk, fish and cooked meat. For dried products evidence of spoilage can be seen through the presence of food pests such as weevils and moths. Milk and fatty foods could aslo go rancid to indicate spoilage.  The phenomenon of gas production by certain pathogenic bacteria should be taken seriously. As consumers and customers, special attention is needed when purchasing canned food. Avoid buying canned products that are blown either on one side or on both sides. There is a possibility of contamination with gas-producing pathogenic bacteria which can cause food poisoning.

The rate of spoilage will depend on several factors including; age and condition of the food, the level of acidity of the food, the amount of water in the food, temperature, oxygen, preservatives present in the food, the type of microorganisms present


We stand the chance of preserving food and our health if we pay attention to the vast number of techniques available to us. Fermentation is a preservation method that goes a long way to boost stomach acidity thereby eliminating some pathogens which cannot withstand that level of acidity. The application of the techniques above on a large scale will help solve our food security issues and at the same time help ward off unwanted foodborne illnesses.

Johnson Opoku-Boateng is the Executive Director & Lead Consultant, QA CONSULT (Consultants and Trainers in Quality/Safety Management, Manufacturing Excellence and Food Safety). He is also the CEO of GS1 Ghana, providers of barcodes for all categories of products. He can be reached on +233209996002, email:

BY: Johnson Opoku-Boateng

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