http://en.wikipedia.org/wiki/Foodborne_illness

Foodborne illness (also foodborne disease and colloquially referred to as food poisoning[1] ) is any illness resulting from the consumption of contaminated food.

There are two types of food poisoning: food infection and food intoxication. Food infection refers to the presence of bacteria or other microbes which infect the body after consumption. Food intoxication refers to the ingestion of toxins contained within the food, including bacterially produced exotoxins, which can happen even when the microbe that produced the toxin is no longer present or able to cause infection. In spite of the common term food poisoning, most cases are caused by a variety of pathogenic bacteria, viruses, prions or parasites that contaminate food,[2] rather than chemical or natural toxins.

http://www.cliffsnotes.com/study_guide/Food-Spoilage.topicArticleId-8524,articleId-8516.html

Food is considered contaminated when unwanted microorganisms are present. Most of the time the contamination is natural, but sometimes it is artificial. Natural contamination occurs when microorganisms attach themselves to foods while the foods are in their growing stages. For instance, fruits are often contaminated with yeasts because yeasts ferment the carbohydrates in fruits. Artificial contamination occurs when food is handled or processed, such as when fecal bacteria enter food through improper handling procedures.

Food spoilage is a disagreeable change or departure from the food's normal state. Such a change can be detected with the senses of smell, taste, touch, or vision. Changes occurring in food depend upon the composition of food and the microorganisms present in it and result from chemical reactions relating to the metabolic activities of microorganisms as they grow in the food.

Types of spoilage. Various physical, chemical, and biological factors play contributing roles in spoilage. For instance, microorganisms that break down fats grow in sweet butter (unsalted butter) and cause a type of spoilage called rancidity. Certain types of fungi and bacteria fall into this category. Species of the Gram-negative bacterial rod Pseudomonas are major causes of rancidity. The microorganisms break down the fats in butter to produce glycerol and acids, both of which are responsible for the smell and taste of rancid butter.

Another example occurs in meat, which is primarily protein. Bacteria able to digest protein (proteolytic bacteria) break down the protein in meat and release odoriferous products such as putrescine and cadaverine. Chemical products such as these result from the incomplete utilization of the amino acids in the protein.

Food spoilage can also result in a sour taste. If milk is kept too long, for example, it will sour. In this case, bacteria that have survived pasteurization grow in the milk

and produce acid from the carbohydrate lactose in it. The spoilage will occur more rapidly if the milk is held at room temperature than if refrigerated. The sour taste is due to the presence of lactic acid, acetic acid, butyric acid, and other food acids.

Sources of microorganisms. The general sources of food spoilage microorganisms are the air, soil, sewage, and animal wastes. Microorganisms clinging to foods grown in the ground are potential spoilers of the food. Meats and fish products are contaminated by bacteria from the animal's internal organs, skin, and feet. Meat is rapidly contaminated when it is ground for hamburger or sausage because the bacteria normally present on the outside of the meat move into the chopped meat where there are many air pockets and a rich supply of moisture. Fish tissues are contaminated more readily than meat because they are of a looser consistency and are easily penetrated.

Canned foods are sterilized before being placed on the grocery shelf, but if the sterilization has been unsuccessful, contamination or food spoilage may occur. Swollen cans usually contain gas produced by members of the genus Clostridium. Sour spoilage without gas is commonly due to members of the genus Bacillus. This type of spoilage is called flat-sour spoilage. Lactobacilli are responsible for acid spoilage when they break down the carbohydrates in foods and produce detectable amounts of acid.

Among the important criteria determining the type of spoilage are the nature of the food preserved, the length of time before it is consumed, and the handling methods needed to process the foods. Various criteria determine which preservation methods are used.

http://www.foodservice.com/food_safety/fb6.cfm

Why Does Food Spoil?  

Food, just like humans, gradually deteriorates because of a natural aging process. However, there are a few things we can do that will have a positive effect on the shelf life and safety of our food. Some preservation is done at the food manufacturing level and some occurs naturally, but a better understanding of the processes may help you extend the shelf life. Preservation methods and storage conditions must be designed to reduce the rate of decomposition and protect the safety, appearance and taste of our food.

The causes of food spoilage - Once food is harvested or slaughtered, its plant or animal tissue soon starts to decay. Microorganisms, such as fungi (molds & yeasts), spoilage bacteria, and their enzymes usually cause the spoilage process. Not all these changes in food are undesirable. Some people like aged beef and cheeses or very ripe fruit. The production of wine and beer involves conversion of sugars to alcohol, while souring of milk is essential in the production of cheese.

However, it is important to remember that some of the conditions that accelerate spoilage, such as inappropriate temperature and moisture control, also encourage the growth of pathogenic microorganisms that cause foodborne illness. Consequently, spoiled food is not just an issue of quality, it is also often a question of food safety.

Mold & Yeast: Corn, nuts, breads, meat, cheeses, fruits and vegetables are all affected by mold. Do not try to salvage cheese that shows visible mold by cutting it away, unless of course it is a natural part of the cheese (i.e. bleu cheese, Brie, or Camembert). Mold forms a network of microscopic strands that extend into the foods which could cause allergic reactions or illness, so discarding them is the safest option. Most cheeses do not improve with age. Deli meats are the same. Yeast can cause discoloration, slime, and odors on sweet, acidic refrigerated foods or jams/jellies.

Bacteria: Some spoilage bacteria are also pathogenic (disease causing). For example, Clostridium perfringens (a common cause of spoilage in meat & poultry) and Bacillus cereus (spoils milk & cream) are also responsible for causing foodborne illness. Most foods are subject to bacterial growth.

Enzymes: Enzymes are naturally present in the cells of microorganisms that break down animal and plant foods. Breakdown continues until blanching or cooking inactivates the enzymes.

Other causes of spoilage include: 1) the bruising or piercing of vegetables, fruits or vacuum packaged food by rough handling; 2) oxidation (changes the taste or texture when exposed to oxygen) or freezer burn; 3) pest infestation as a result of poor receiving control, storage, rotation or cleaning; 4) adulteration through addition of leftover, inferior or undesirable food or ingredients to fresh food.

Detecting spoilage relies on being aware of the typical indicators, such as appearance (discoloration or slime), texture, smell or taste (obviously not recommended if any of the others are present).

Bottom line prevention - When in doubt, throw it out. Food spoilage affects your bottom line in food waste dollars. Prevention includes good receiving inspection practices, following the manufacturer's instructions, unfailing temperature recording and control, being observant and of course good sanitation and personal hygiene by food handlers.

http://www.nhf.org.nz/index.asp?PageID=2145823148

Causes and Prevention of Food Spoilage

What causes food spoilage?  How can you prevent it?

Types of spoilage in food

Slime: Food becomes slimy when there is so many bacteria they touch one another

Souring: Foods may go sour when the micro-organisms produce acids, e.g. sour milk.  Some meat products become sour if packaged in certain types of plastic

Discolouration: Food may become discoloured from microbiological growth.   Some moulds have coloured spores, e.g. black mould on bread, or blue and green mould on citrus fruit.  Sometimes meat becomes green due to the growth of micro-organisms

Gas: Bacteria often produces gas as a by-product which affects food, e.g.

-   Meat becomes spongy in texture -   Packages, cans or vacuum packs will smell

Odour: Rotten smells develop from the breakdown of bacteria.

Some moulds grow in refrigerators - especially walk-in style refrigerators.  Therefore, it is essential to use food quickly to stop if from becoming spoiling and to clean the refrigerator wall regularly.  

Food spoilage is more likely to happen in foods which are:

How can you try to prevent food spoilage?

Moist Keep food in well-ventilated places to avoid build-up of moisture.

Warm Do not keep food at warm temperatures.

Low in acidMake sure pickles or foods preserved in acid (vinegar, acetic acid) have sufficient acid added during processing and are used within a reasonable time.

Low in sugar Adding sugar to food will preserve them, e.g. jam.  However they should be used within a reasonable time.

Damaged Check food on delivery and do not accept damaged stock.

Old Rotate food using a first in-first out policy.

Sometimes micro-organisms can be used to produce foods we like:

The blue veins in cheese are formed by mould growth, so remember to store your blue cheeses separately from your other cheeses

Milk is soured in the production of yoghurt and cheese by useful bacteria

Yeast is used in the making of bread and alcoholic beverages.

http://home.pacific.net.hk/~ppleung/Chem/spoilage.htm

What is food spoilage?

Food spoilage means the original nutritional value, texture, flavour of the food are damaged, the food become harmful to people and unsuitable to eat.

Causes of the spoilage of food

The picture of spoiled food

Microbial spoilage

There are three types of microorganisms that cause food spoilage -- yeasts, moulds and bacteria.

Yeasts growth causes fermentation which is the result of yeast metabolism. There are two types of yeasts true yeast and false yeast. True yeast metabolizes sugar producing alcohol and carbon dioxide gas. This is known as fermentation. False yeast grows as a dry film on a food surface, such as on pickle brine. False yeast occurs in foods that have a high sugar or high acid environment.

Moulds grow in filaments forming a tough mass which is visible as `mould growth'. Moulds form spores which, when dry, float through the air to find suitable conditions where they can start the growth cycle again.

Mould can cause illness, especially if the person is allergic to molds. Usually though, the main symptoms from eating mouldy food will be nausea or vomiting from the bad taste and smell of the mouldy food.

Both yeasts and moulds can thrive in high acid foods like fruit, tomatoes, jams, jellies and pickles. Both are easily destroyed by heat. Processing high acid foods at a temperature of 100°C (212°F) in a boiling water canner for the appropriate length of time destroys yeasts and moulds.

Fungal Spoilage

Storage rot in grapes caused by Botrytis cinerea.

Storage rot in strawberry caused by Botrytis cinerea.

Blue mould rot in tomato caused by Penicilliumi spp. (also by Fusarium spp.)

Black mummy rot of grapes caused by Guignardia bidwellii

Watery soft rot in apple caused by Sclerotinia sclerotiorum.

Blue mould on oranges caused by Penicillium digitatum.

Bacteria are round, rod or spiral shaped microorganisms. Bacteria may grow under a wide variety of conditions. There are many types of bacteria that cause spoilage. They can be divided into: spore-forming and nonspore-forming. Bacteria generally prefer low acid foods like vegetables and meat. In order to destroy bacteria spores in a relatively short period of time, low acid foods must be processed for the appropriate length of time at 116°C (240°F) in a pressure canner. (Temperatures higher than 100°C [212°F] can be obtained only by pressure canning.)

Eatting spoiled food caused by bacteria can cause food poisoning.

Bacterial Spoilage

Soft rot in tomato caused by Erwinia carotovora.

Autolysis

Enzymes

Enzymes are proteins found in all plants and animals. If uncooked foods are not used while fresh, enzymes cause undesirable changes in colour, texture and flavour. Enzymes are destroyed easily by heat processing.

Oxidation by air

Atmospheric oxygen can react with some food components which may cause rancidity or color changes.

Other factors

Infestations (invasions) by insects and rodents, which account for huge losses in food stocks.

Low temperature injury - the internal structures of the food are damaged by very low temperature.

Low Temperature Injury

Internal mahogany browning of potato caused by low temperature injury.

Chilling injury in cucumber caused by low temperature. Note the watery surface.

Types of food decay

There are three types of food decay:

Putrefaction

Fermentation

Rancidity

Example of food spoilage

Microorganisms involved in food spoilage

Common mould on bread

Canned food spoilage

To prevent food spoilage, see also preservations.

http://wikieducator.org/Lesson_8:_Food_Spoilage

Lesson 8: Food Spoilage

FOOD SPOILAGE

Introduction

Discussion

have you ever kept some fresh food items such as meat, fish, pepper, mangoes, oranges or cassava on the kitchen shelf for a long time? Well,if you have never done that then let’s perform a small experiment.Just leave the above mentioned food items on the kitchen shelf for about three to five days and observe what happens to them.You will realize that their appearance, smell and taste have changed.Some of them will be covered with a whitish substance, others some orange powdery substance and some also will smell very badly.All these signs indicate that these foods are not wholesome since they are contaminated

Objectives

In this chapter I am going to talk about;

Food spoilage

Causes of food spoilage

Reasons for keeping food commodities from spoilage

The effects of food spoilage on;

protein

fruit and vegetables and fats

oils

Lesson Content

What is food spoilage?

Most natural foods have a limited life. Perishable foods such as fish, meat, milk, bread, tomatoes and potatoes have a short life span. Other foods keep for a considerably longer time but decompose eventually. Once food has been harvested, gathered or slaughtered it begins to deteriorate until eventually it becomes unfit for consumption. This deterio-ration is known as decay and leads to food spoilage.

Now let’s look at the picture below and describe the change that you can see on each food item.

Headline text

courtesy of flickr.com

Fig 14.1 Signs of deterioration of food.

Food Item Signs of spoilage

1 -

2 -

3 -

4 -

5 -

Well done, let’s continue.

These gradual changes that cause deterioration and decay in foods are due to certain organisms and chemicals present in the food and outside the food. Let’s now look at the causes of food spoilage.

Causes of food spoilage

Food spoilage is caused by two main factors, namely;

Natural decay in foods

Contamination by micro-organisms

Natural decay in food

This comes about as a result of moisture loss and the action of enzymes.

Moisture loss

Moisture loss mostly occurs in fruit and vegetables which contain large amounts of water. Fruits and vegetables continue to respire after harvesting and therefore lose water through their leaves and skin. Such water could be replaced from the soil through the roots when not harvested. The water retains the structures of the cells of the plants and makes them look fresh. After harvesting, there is no way that the lost water can be replaced so the vegetable or fruit shrinks in size, becomes limp and

its skin becomes wrinkled and leathery. Moisture loss occurs in other foods like meat, fish, cheese, due to evaporation of water from the surface.

Pause!

Why don’t you also try and see how moisture loss can affect some food. Collect carrots, oranges, garden eggs, kontomire and pepper and leave them on a plate for ten days. Then, keep observing their appearance for about two weeks.Now describe how each of them finally looks like in the following table.

Activity

2:Moisture loss in food

Food item Observation

Carrots--------------------------------------------

Pepper---------------------------------------------

Garden eggs----------------------------------------

Kontomire------------------------------------------

Orange---------------------------------------------

Good!

Let’s now look at another way through which natural decay can bring about food spoilage.

Enzyme action in the food

Food spoilage can also come about through the action of enzymes presents in the food. Enzymes are chemicals which are present in all food. They speed up chemical changes that result in loss of flavour, colour and texture. As enzymes are mainly composed of protein, they are sensitive to heat. They are active in temperatures found in a kitchen on a warm sunny day. They can remain very slightly active at very low temperatures such as those found in the freezer. This is why there is a limit to the time food can be stored in a freezer. The activity of these enzymes stops when

they are heated above 70 oC. Heat treatment by blanching (i.e. pouring boiling water on the food) is recommended. Some enzymes remain inactive until the food is harvested or slaughtered. Once activated, such enzymes speed up the process of decay by breaking down the tissues and components of the food in the various ways such as oxidation, browning and ripening.

Oxidation

When Oxidation occurs (i.e. when food comes into contact with oxygen) the enzymes cause the destruction of certain nutrients e.g. vitamin c, thiamine and carotene.

Browning

Enzymes again cause browning in certain foods the moment they are exposed to air. When you cut or bruise food such as apple or yam, the exposed surface will discolour and turn brownish due to the activity of enzymes.

Ripening

Enzymes are involved in the process that causes ripening in certain foods such as fruits and vegetables. Unripe bananas for example contain starch which is gradually converted to sugars, until the banana becomes very sweet, and its skin colour changes from green to yellow. Eventually, the skin colour changes to dark brown and it is no longer fit to be consumed.

The activity of enzymes in food makes it easier for the micro-organisms responsible for food spoilage to enter the food.

The activity of micro-organisms

Definition

Micro-organisms are tiny organisms present almost everywhere; they occur in all fresh foods, in the soil, in dust, on all surfaces and on the skin of people handling food.

Do you know of any micro-organisms that contaminates food? Pause!! and think about one. Let’s go on. The main micro-organisms responsible for the contamination of food are bacteria, moulds and yeasts. These micro-organisms are invisible to the naked eye, but can be seen under a microscope. They are capable of

multiplying very rapidly in the correct moisture, food and temperature conditions. These conditions must be avoided if the risk of food spoilage is to be reduced. Let’s now look at each of these micro-organisms and how they operate.

Moulds

Moulds are tiny plants, which are just visible to the naked eye. They grow from cells called spores present in the air. They settle and multiply on suitable foods. At this stage, they are visible as a fluffy coloured mass and the food is said to have gone mouldy. Moulds grow most readily in most conditions, at temperatures between 20oC and 40oC. They grow on a variety of foods, particularly meat, cheese, fruit and bread, especially if the food is stored in damp conditions. Moulds may remain active at the low temperatures of a refrigerator but they are destroyed by heat above 70oC. They also like a slightly acid medium and this is why they attack citrus and the surface of jams. Why don’t you try and give examples of food that can be attacked by moulds. Let’s continue.

Food that is contaminated with mould often appears to be safe to eat as only the outer part is affected by mould growth. However, recent research has shown that substances produced by the mould which migrate into the food could be harmful to many organs of the body. It is therefore advisable to discard mouldy food completely, rather than just to remove the mouldy part.

Yeasts

Yeasts are microscopic single called plants, which are found in the air and soil, and on the surface of fruit. Some are able to tolerate fairly high acidic, salt and sugar concentrations and can grow without the presence of oxygen. At the mention of yeast what comes into your mind? Bread and doughnut isn’t it? Yes, the activity of yeast is used in the baking and brewing industries to make bread, doughnut and alcoholic beverages through a process called fermentation. However, they can cause food spoilage in syrups, fruits, fruits juices and jam especially as they can survive without air.

Let’s look at how they reproduce. Yeast cells reproduce by budding. At first a small projection appears at the edge of the parent cell and from this cytoplasm and nutrients flow. As the bud grows, the nucleus moves towards it and divides so that a new nucleus enters the bud. When the bud is almost as large as the parent cell, a wall forms separating if from the parent cell, and it then breaks away. When they are reproducing rapidly, the buds do not break away but continue to reproduce until long chains of yeast cells are formed.

Yeast cells grow and reproduce in conditions similar to those required by other fungi. They need oxygen, warmth, food and moisture in order to grow successfully. Yeast grow best at temperatures between 25oC and 30oC. Extreme heat destroys all yeasts and most are destroyed at temperatures above 60oC.

Bacteria

Bacteria are the most widespread of the micro-organisms found in food. They are minute single cells of various shapes. Under ideal conditions, they divide into two every 20 minutes, consequently, millions of them may develop in contaminated food in a short time. They are more dangerous than moulds and yeast because food may be severely infected but not smell, taste or look bad. Many types of bacteria present are harmless but some do cause illness. The bacteria that cause infections in humans are known as pathogens.

As all bacteria thrive in similar conditions, it is important to avoid conditions which favour their growth in order to prevent infection. They are active over a wide range of temperatures. Some like warmth and are active at 75oC. Others like cold conditions and grow at temperatures as low as 5oC. This may cause problems in storage of foods. Some bacteria can form resting bodies called spores to protect them when the conditions are unfavourable for normal growth, for example the wrong degree of acidity or alkalinity, temperature or lack of moisture. Although normal bacteria are destroyed during heat treatment by boiling, some spores survive boiling for hours. They can resume normal activity when conditions become more favourable and contaminate some preserved foods. Bacteria are lalled in an acid medium, and therefore they are not a problem in preserving fruits and making jams. The pasteurization of milk does not destroy all bacteria in milk but does destroy those bacteria likely to cause disease. Freezer temperatures must be low enough to prevent bacteria activity during storage. Although some bacteria die in the freezer, some remain inactive in the food and start to grow again when the food thaus. The removal of moist are by drying or by addition of large quantities of sugar and salt make conditions unsuitable for bacteria, and these methods are therefore use in food preservation. (See unit 15).

After knowing the causes of food spoilage why don’t we look for the reasons for keeping food commodities from spoilage?

Reasons for keeping food commodities from spoilage

Deterioration may cause food to be wasted

Contaminated food can cause illness and in severe cases, this is known as food poisoning

Money is saved when food commodities are kept from spoilage

When food is kept from spoilage, it maintains it nutritive value

It also ensures food is available for use even during lean season

Why don’t you try and add a few points to the above reasons. Let’s now find out the effects of food spoilage on different food commodities.

The effects of spoilage on the various food commodities

Protein food

They go putrified when they are contaminated. This is the situation where protein foods rot, and produce very bad smell.

Fats and oils

They go rancid. This is the condition where food containing fats and oils begin to smell and tasted bad when they are old.

Carbohydrates

Cooked cereals become marshy and slimy when affected by micro-organisms. This condition is known as serenasis. Flour products smell and taste unpleasant when they are spoilt. They are described as being stale.

Fruits and vegetables

They rot, ferment and decay.