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CHAPTER 5 : FOOD MICROBIOLOGY - Coggle Diagram
CHAPTER 5 : FOOD MICROBIOLOGY
What is food microbiology?
Microbiology :
is the study of microscopic organisms (microorganisms) such as bacteria, yeast, fungi, algae, viruses and other microscopic forms of life.
Food microbiology :
the study of microorganisms and their beneficial and harmful effects on the safety and quality of processed and raw foods.
Chapter 5.1 :
Types of microorganisms in food
What is microorganisms?
Living organism too small to be seen with naked eye without magnification, but visible under a microscope.
Types of microorganisms :
1) Viruses
2) Protozoa
3) Bacteria
4) Algae
5) Fungi
Microorganisms and food
Microorganisms is a living cells that need a source of food and a place to live that is within their physiological tolerance.
Microbes alter food by secreting enzymes into the food they are growing on and absorbing the small soluble nutrient molecule.
Types of bacteria
Spoilage :
Not particularly harmful bacteria which cause food to go off
Beneficial :
"Good Bacteria" which are used to make yogurt and cheese
Pathogenic :
Illness causing bacteria
Chapter 5.2 :
Factors affecting microbial growth
The ability of microorganisms to grow or multiply in a food is determined by the
food environments
as well as the
environment where the food is stored.
Intrinsic Factors
Factors inherent to the food.They are chemical and physical characteristics of food
Nutrient content
Anti microbial constituents
Water activity (aW)
Biological structures
Acidity (pH)
Extrinsic Factors
Storage conditions of the food.Properties of the environment in which the food is stored
Relative Humidity
Presence of gases
Temperature
Presence & activities of other microorganisms
Chapter 5.3 :
Negative roles of microorganisms in foods
Chapter 5.3.2 :
Food poisoning
What is food poisoning?
-
Food poisoning is an illness caused by eating contaminated food. Most people get better without the need for treatment.
The symptoms of food poisoning usually begin 1-3 days after eating contaminated food. They include :-
i) feeling sick
ii) vomiting
iii) diarrhoea
iv) stomach cramps
Foods particularly susceptible to contamination if not handled, stored or cooked properly include :-
i) raw meat and poultry
ii) raw eggs
iii) raw shellfish
iv) unpasteurised milk
v) 'ready to eat' foods
How is food contaminated?
Food can become contaminated at any stage during production, processing or cooking. For example, food poisoning can be caused by :-
i) not cooking food thoroughly
ii) not storing food that needs to be chilled at below 5'C correctly
iii) leaving cooked food for too long at warm temperatures
iv) someone who is ill or who has dirty hands touching the food
v) eating food that has passed its 'use by' date cross contamination
Who's at risk of food poisoning?
If they do get sick, the effects are much more serious. These groups include :-
1) Pregnant women & babies
2) Older adults
3) Persons with chronic illnesses
Treating food poisoning
To help relieve your symptoms you should rest and drink plenty of fluids. It is best to avoid food until you feel much better. When you start eating again, choose foods that are easily digested, such as toast.
Try to drink as much water as you can, even if you can only sip it, particularly every time you pass diarrhoea.
Chapter 5.3.1 :
Food spoilage
What is food spoilage?
The process in which food deteriorates to the point in which it is not edible to humans or its quality of edibility becomes reduced
Foods can be classified into 3 major categories :
1) Non-perishable foods
2) Semi perishable foods
3) Perishable foods
Common indication of food spoilage include changes of :
1) Appearance e.g : discoloration or slime
2) Smell
3) Texture
4) Taste
Factors contributing to food spoilage
2)
Enzymes
Enzymes are biological catalysts, mainly proteins, generated by an organism to speed up chemical reactions.
3)
Insects
Worms, bugs, weevils and fruit flies cause extensive damage to food and reduce its nutritional value and make it unfit for human consumption.
1)
Microorganisms
The different kinds of microorganisms responsible for the food spoilage are :
i) Bacteria
ii) Yeasts
iii) Molds
Chapter 5.4 :
Source of microorganisms
Microorganisms are present in natural ecosystems such as air, soil and water. They are also present on the man himself and all living animals and plants.
In animal products, the bacteria are often already in the meat. Cooking the meat at high temperatures kills many pathogens, preventing illness.
Sources of microorganisms found in food :
-
1) Soil & water
2) Air & dust
3) Plants & plants product
4) Intestinal tract of animals
5) Food utensils
6) Food handlers
7) Animal feed
8) Animal hides
Cross contamination :
Transfer of microorganisms from a contaminated surface of material to a non-contaminated food or surface.
Examples of cross contamination are :-
1) Hands that touch raw foods
2) Surfaces, like cutting boards
3) Raw or contaminated foods that touch or drip fluids on cooked or ready to eat foods
Chapter 5.5 :
Uses of microorganisms in food production
Making foods with microorganisms :
Microorganisms are widely used in the food industry to produce various types of foods that are both nutritious and preserved from spoilage because of their acid content.
Food processed by microbes develop different flavors and nutrient content.
Yeast & Mold
Saccharomyces cerevisiae
(yeast) will undergo anaerobic respiration in the absence of oxygen to produce ethanol and carbon dioxide.
This reaction forms the basis for the production of a range of food sources, including bread and wine.
Lactic acid bacteria
Bacteria which convert
carbohydrates
to
lactic acid without using oxygen
.
Lactic acid
contribute to the taste and texture of fermented products and inhibit food spoilage bacteria by producing growth-inhibiting substances
What is fermentation?
General definition
: An anaerobic cellular process in which bacteria, yeast or other microorganisms convert organic foods into simpler compounds and chemical energy (ATP) is produced.
Fermentation in food processing
: the conversion of carbohydrates into alcohols and carbon dioxide or organic acids by yeast, bacteria or a combination of both.
Fermented food products :
-
1) Yogurt
2) Tempeh
3) Kombucha
4) Miso
5) Fish sauce, tamari and shrimp paste
6) Sauerkraut
7) Kimchi
8) Pickles
9) Kefir
10) Sourdough
11) Vinegar