Food Spoilage:

It refers to change in Physical and Chemical property of food, making food unfit for Consumption. Invasion of microorganisms like bacteria and fungi usually causes spoilage of food.


Food spoilage generally occurs due to Physical, Chemical or Biological agents that changes colour, flavour, appearance, odour and other properties of food. Shelf life of most of the natural foods is very less and is perishable, for example, meat, fish and bread can spoil easily. Decomposition of food generally involves 3 processes: Putrefaction (chemical breakdown of food or decay of organic matter), Fermentation (chemical breakdown of substances by action of microorganisms, yeast), Rancidity ( refers to oxidation of fats).

Natural Contamination:

It refers to contamination of food when microorganisms themselves attaches to food in its growing stages and this kind of contact is essential for certain kinds of food. For example, Yeasts contaminates fruit for carbohydrates fermentation.

Artificial Contamination:

This type of contamination occurs during handling of food when food is under various stages of production like, packaging, storage, etc. Improper handling of food during this stages results in contamination of food by microorganisms.

Intrinsic factors of food like pH, redox potential, H2o activity determines the type of microflora growing on the food. This final composition of microflora is responsible for food spoilage.

Types of Food Spoilage:

1.Microbial Spoilage:

Microorganisms associated with food are:

Bacteria, Filamentous Fungi, Viruses, Yeasts, and animal parasites.


They are associated with both plant and animal foods. Bacteria are associated with food intoxication and spreading of food borne diseases.


Acenatobacter Gram negative- present in raw and prepared foods like beef and poultry carcasses.

Aero monas: gram negative, responsible for spoilage of fish.

Alkaligans: gram negative, responsible for spoilage of egg and dairy products.

Citrobacter: gram negative, it is responsible for spoilage of vegetables and fresh meat.

Corynebacterium: gram positive, involved in spoilage of vegetables and  meat.

Filamentous Fungi:

When food is left for one or more day covered, tangled mass of furry growth appears on food which is called fungi or mould. Fungi are responsible for spoilage of Grains, nuts, and fruits as they have low pH and H20 activity.


Mucor: Zygomycotena-common contaminant of fruits, berries and nuts.

Rhizopus: Zygomycotena- known commonly as bread mould. It is more prevalent in fermented and stored foods.

Claviceps: Ascomycotena-  produces toxic alkaloids in cereals, when consumed can cause Hallucinations.


Contamination by yeasts results in Souring of milk.


Candida: most common contaminant of dairy products, fresh fruits, and alcoholic beverages.

Saccharomyces: spoilage of fruits and fruit products.

Torulopsis: responsible for spoilage of beef, creamed butter, condensed milk, etc.


viruses found in food are termed as enteric or intrinsic viruses.


Enterovirus, Adenovirus, Reovirus, Hepatitis A virus.

Animal Parasites:

They belong to 3 distinct groups:

Protozoa: Giardia, Entamoeba Hystolytica

Flatworms: Taenia, Fasciola

Roundworms: Ascaris

2. Physical Spoilage:

Physical Spoilage refers to damaging of food during Harvesting, Processing or distribution of food. During such processes there are high chances of food spoilage if proper measures are not followed. The damage increases the chance of spoilage as the outer layer is completely broken or bruised. For example- Canned foods gets spoiler easily if the cans are not properly packed with lid or are contaminated during processing.

3. Chemical Spoilage:

Chemical reactions in food are responsible for change of colour, texture and taste of the food products. Generally foods are fresh especially vegetables and animal food, but after harvesting and slaughtering, chemical changes begin automatically in the food and the quality of food becomes deteriorated.

4. Enzymic Spoilage:

Enzymes acts as biological catalyst to carry out biological reactions in cell and play an important role in biochemical reactions. After death of cells or tissues, enzymes play a role in its decomposition by a process called Autolysis( self destruction )

Example: In tomatoes, some enzymes helps it for ripening, but at the same time there are certain enzymes which are responsible for its decay. Once enzymic Spoilage is underway, it damages the outer skin of tomato and exposes it to mould growth and decay.

Factors Affecting Food Spoilage:

  1. Water Content: Amount of water holding capacity in foods is referred to as it’s water activity.(WA). Water activity of most of the fresh fruits is approximately 0.99, which makes them more susceptible to microbial growth.
  2. Environmental Conditions: Environmental influence on food is the major concern. When food is exposed to intrinsic conditions like temperature, air, or even small amount of moisture, can result in growth of Micro-organisms. Changing environmental conditions can help to prevent spoilage. For example- storing food at lower temperature can prevent it from spoiling.
  • Packaging and storage: Packaging of foods is after processing is very vital as it protects food from harmful contaminants and also from various other factors like environment, temperature, etc. The type of packaging plays a key factor in ensuring the safety and preventing spoilage. Food packed in jars, cans ensures safety and prevents food from dust, moisture, air and harmful microbes.

Sources of Micro-organisms for Food Spoilage:

Micro-organisms are present everywhere. General source of Micro-organisms include air, water, sewage, soil and animal wastes. Foods grown in ground have higher risk of spoilage due to micro-organisms.  Foods like fish, meat are contaminated by presence of bacteria in their  internal organs like skin and feet. Meat has higher tendency of contamination as raw meat attracts lot of microbes, so it is advisable to store raw meet immediately after chopping.

Ways to Prevent Food Spoilage:

  • Ensure proper packaging is available to the food cans and jars after processing.
  •  Don’t leave the food in open air for more than 15min, to avoid contact with microbes.
  •  Ensure that your refrigerators are operating at correct temperatures.
  •  Food must be protected from light and must be stored in amber colour or transparent containers.
  • Low temperature is a key as it retards microbial growth.
  • Avoid placing food where there is more humidity, as high humidity attracts more growths of microbes and moulds. Placing food in dry places is most appropriate.

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