Micro-organisms play many roles in food some desirable and helpful and some undesirable and detrimental
Good effects of Microbes in food
Microbes are deliberately grown in food to produce required changes. Microbes that can not be reproduced synthetically produce these changes. The changes are usually complex and the microbes can often be grown economically.
Beer, wine, saki etc.
Cheese, yoghurt, butter,
Sauerkraut, Tempe, Soy sauce
Some food processes do not use microbes for the main changes but fermentations
may contribute incidentally to flavours
Coffee, Cocoa, and Tea
Single Product Production
Fermentations can be used to produce ingredients used in food such as Citric Acid, Vitamin C, Vitamin A, and Enzymes.
Microbes as Food:
Microbes can be grown as food. This usually involves converting some
cheap waste or biproduct of another process in to microbial cells that
can be user as human food or fed to stock to convert it to meat or milk.
Eg Singe Cell Proteins
From Waste petroleum material
Paper production waste (sulphite liqueur)
Molasses (waste from sugar processing)
In some areas it is cheaper to grow a high yielding carbohydrate crop like cassava and the convert it to SCP. This produces more grams of protein per acre than growing a high protein crop like soybeans.
Bad Effects of Microbes on Food
This is when microbes produce a negative effect on food that make that
food less desirable. The changes produced may be called undesirable in
one culture but considered desirable in another. It may or may not make
the food dangerous to eat. But is always obviously changed so it is rarely
eaten. In this way spoilage as a beneficial effect by stopping us from
eating food that might be dangerous
If food is cooked the food spoilage organisms are usually killed. This allows
Food poisoning bacteria to grow with out us knowing. This is because food poisoning organisms donít make obvious changes.
There is many different type of food spoilage but they are usually caused by saprophytes such as Pseudomoni and fungi. Most often plant material is spoiled by fungi
Food Born Disease
Diseases can be caused by microbes in food producing a toxin. In most the organisms must grow in the food while they make the toxin. These include e bacteria, fungi. Toxins can accumulate in the bodies of sea food these are be caused by algae that the fish eats in the sea.
Bacterial food poisoning:
Fungal food poisoning
Aflatoxin Aspergillus flavis
Ergot Claverceps purpurea
Yellow Rice Disease Penicillium
Algae Food Poisoning
Red Tide Dinoflagellates
Physteria ( Physteria piscicida)
Food Borne Infections
With infections the organism must grow in the human to cause an infection. This may be confined to the intestine to cause gastro-enteritis or they may invade the rest
Food Borne Infections that require a Large Inoculum
These diseases are coursed by week pathogens that require large numbers
to cause a disease and must grow in the food before it is eaten
Eg Salmonella, E. coil, Vibrio Paraheamolytica , ListeriaFood Borne Infections that require a Small Inoculum
There are many parasites that can cause infections with only one or
These do not need to grow in the food and can be transmitted by Just a Touch from an infected individual
Many of these are Zoonoses ie disease of other animals and include bacteria, viruses and parasites
Typhoid Salmonella typhi
Cholera Vibrio cholerae
T.B. Mycobacterium tb.
Q- fever Coxiella burnetii