Micro-organisms in Foods

Question 1

Micro-organisms, in relation to food, can have one of these 3 roles:

Answer 1

⦁ Pathogenic micro-organisms can cause infections or intoxications
⦁ Saprophytic micro-organism play a role in biodegradation and cause food spoilage
⦁ Cultured micro-organisms like probiotic bacteria are used in food processing.

Question 2

cause food-borne infections or intoxication, and include bacteria, viruses, parasites and moulds.

Answer 2

Pathogenic micro-organisms

Question 3

The main factors that contribute to occurrence of foodborne diseases are:

Answer 3

⦁ The use of raw food and ingredients from unsafe sources
⦁ Inadequate cooking or heat processing
⦁ Allowing several hours to pass between preparation and eating of food
⦁ Inadequate reheating
⦁ Improper hot holding, meaning below 65°C
⦁ Food handling by infected persons or carriers of infection
⦁ Inadequate cleaning of equipment and utensils

Question 4

are the most important microorganisms to the food processor.

Answer 4

Bacteria

Question 5

three basic shapes:

Answer 5

spherical, straight rods, and spiral rods

Question 6

Some rod-shaped bacteria are capable of existing in two forms

Answer 6

dormant spores and active vegetative cells

Question 7

Is a common cause of diarrhea humans as well as some animal species. The transmission can be by direct contact between humans and infected animals or their feces. More commonly, it is transmitted by the consumption of contaminated food or water, t person-to-person spread.

Answer 7

⦁ Campylobacter jejuni

Question 8

There are more than 2000 serotypes of salmonella spp, of which only a few cause Salmonella gasteroenteritis in humans. Animals are the main reservoir, and transmission occurs by ingestion of contaminated products. Foods especially at risk are poultry, meat, eggs and milk.

Answer 8

⦁ Non-typhi salmonellosis

Question 9

Cause typhoid fever and paratyphoid fever respectively. Since the reservoir for both these bacteria are usually humans, transmission occurs mainly through person-to-person contact or contamination of food by food handlers.

Answer 9

⦁ Salmonella typhi and paratyphi

Question 10

The source of this infection are humans. The bacteria are often found in smaller amounts in the nose and on the skin of clinically healthy people.

Answer 10

⦁ Staphylococcus aureus

Question 11

There are several serotypes, some of which are harmless to humans whereas others can cause gastroenteritis. Enterotoxigenic E.coli is the most common cause of traveller’s diarrhea. The source is humans, and transmission usually occurs through contaminated food and water.

Answer 11

⦁ Escherichia coli

Question 12

This bacterium is highly associated with food stored for long periods of time in the fridge because it is ubiquitous, and has the ability to grow slowly, even at low temperatures. Can be fatal in immunocompromised, where it can cause septicemia and meningitis.

Answer 12

⦁ Listeria monocytogenes

Question 13

The source is humans and primates. Because it has low infectious dose, the main mode of transmission is person-to-person contact. It can also be transmitted through infected food and water. The symptoms of shigellosis are fever and watery diarrhea. The infection can also manifest as a dysenteric syndrome which includes fever, abdominal cramps and tenesmus, and frewuent, small volume, bloody stools containing mucous.

Answer 13

⦁ Shigella

Question 14

The source of this infection is humans. The main mode of transmission is through contaminated water and food, or person-to-person spread in overcrowded, unhygienic situations. It causes severe watery diarrhea, which can reach up to 20 liters per day.

Answer 14

⦁ Vibrio Cholerae 01

Question 15

Its source is the intestinal tract of fish, birds, and mammals. It is also widely distributed in nature. The bacterium is a spore producing anaerobe, with a highly potent heat labile toxin that affects the nervous system.

Answer 15

⦁ Clostridium Botulinum

Question 16

Many parasites, such as the helminths, have a complex lifecycle involving more than one host. The major route of transmission for these parasites to humans is by the route of food. The consumption of undercooked pork or beef, or the consumption of raw salads washed in contaminated water seems to be the trend.

Answer 16

⦁ Parasites

Question 17

also called pig and beef tapeworms. Their cysts,, present in the muscle of the animal are ingested and the adult worm develops in the gut. The ova may develop into larvae that may invade other tissues, such as the brain, forming cysticercosis and severe neurological disorders as a consequence.

Answer 17

⦁ Taenia solium and T. saginata

Question 18

is found in undercooked pork. The larvae can invade tissues and cause a febrile illness.

Answer 18

⦁ Trichinella spiralis

Question 19

This infection can be foodborne, waterborne or spread by interpersonal contact. It causes acute or subacute diarrhea, with malabsorption, fatty stools, and abdominal pain and bloating.

Answer 19

⦁ Giardia lambila

Question 20

The transmission is mainly food- or waterborne. The cysts pose a major problem since they are highly resistant to chemical disinfectants, including chlorination. The infection is usually asymptomatic, but may appear as either a persistent mild diarrhea or a fulminant dysentery.

Answer 20

⦁ Entamoeba histolytica

Question 21

are the smallest and simplest microorganisms.

Answer 21

viruses

Question 22

are the major causes of gastroenteritis

Answer 22

⦁ Rotaviruses and Norwalk virus

Question 23

outbreaks are mainly caused by asymptomatic carriers which handle food.

Answer 23

⦁ Viral hepatitis A

Question 24

It is the change of look, consistency, flavor and odor of foods, and is caused by bacteria, moulds and yeasts.

Answer 24

food spoilage

Question 25

Examples of action of bacteria involved in food spoilage:

Answer 25

1.Lactic acid formation
2.Lipolysis
3.Pigment formation
4.Gas formation
5.Slime or rope formation

Question 26

Some strains produce mycotoxins under certain conditions

Answer 26

Moulds

Question 27

Foods most at risk for moulds:

Answer 27

1.Grains and grain products
2.Peanuts, nuts and pulses
3.Fruits and vegetables
4.Milk and milk products - aflatoxin

Question 28

Most commonly used microorganisms

Answer 28

yeast, bacteria, moulds, (YBM)

Question 29

Fermented milk products:

Answer 29

Lactobacillus, Lactococcus, Bifidobacterium

Question 30

are live food supplements used in yoghurt and other fermented milk products.

Answer 30

Probiotics

Question 31

Mould in food production:

Answer 31

cheese, dry salami, soy sauce, sake

Question 32

is an unwanted quality change in a foodstuff, such as staling, discoloration, the development of off-flavours and odours (e.g. rancidity), and thinning of sauces.

Answer 32

Chemical food spoilage

Question 33

A series of continuous degradative changes occurring in a food item which may affect the product’s wholesomeness, result in a reduction of its quality, and/or alter its serviceability.

Answer 33

Food Deterioration

Question 34

is a term that refers to freedom from pathogenic or otherwise harmful microorganisms.

Answer 34

Wholesomeness

Question 35

is a term which we often hear in conjunction with deterioration. It is often used as a synonym for deterioration. However, it needs to make distinction between these two terms.

Answer 35

Spoilage

Question 36

is food procured, packed, or held under unsanitary conditions that renders it injurious to the health of the consumer, or food or food containers having naturally occurring or added harmful substances, or food found to be filthy, putrid, decomposed, or produced from a diseased animal or an animal that died other than by slaughter.

Answer 36

Unwholesome

Question 37

is any variation from the expected appearance, feel, smell, or taste characteristics of a product when it was initially produced or processed for resale

Answer 37

Off-condition

Question 38

a term that refers to the degree of excellence or grade of a Product.

Answer 38

Quality

Question 39

a term that refers to the usefulness of a food item. Reduced serviceability in a product may result in the use of additional processing methods to return the food item to its original state.

Answer 39

Serviceability

Question 40

Major causes of food deterioration include:

Answer 40

1.Growth and activities of micro-organisms, mainly bacteria, yeasts and moulds;
2.Activities of natural food enzymes;
3.Insects, parasites and rodents;
4.Temperature, both heat and cold;
5.Moisture and dryness;
6.Air and in particular oxygen;
7.Light;
8.Time.

Question 41

Human illnesses caused by foodborne microorganisms are popularly referred to as…

Answer 41

Food Poisoning

Question 42

A few of this strains found in human feces are in themselves pathogenic, causing infection and disease.

Answer 42

Escherichia coli

Question 43

commonly referred to as “staph,” is normally present on the skin, the mucous membranes, and in pimples and boils of human beings and other animals.

Answer 43

Staphylococcus aureus

Question 44

is almost always caused by eating contaminated food or drink. Contamination originates from the intestinal tract of human beings or animals who harbor Salmonella organisms.

Answer 44

Salmonella

Question 45

produces a rare but often fatal disease called botulism. It is caused by a neurotoxin produced during growth in the absence of air.

Answer 45

Costridium botulinum

Question 46

is a spore-forming organism which, like botulinum, grows only in the absence of air.

Answer 46

Clostridium perfringens

Question 47

is a spore-forming organism that grows in the presence of oxygen and is widely distributed in most raw foods. Since the spores survive boiling for several minutes, they remain viable in cooked foods in small numbers.

Answer 47

Bacillus cereus

Question 48

is a non-spore forming, slightly curved rod, closely related to the organism that causes cholera. It is widely distributed and grows in brackfish waters, estuarine sediments, raw fish, and shellfish throughout the world.

Answer 48

Vibrio parahaemolyticus

Question 49

This changed with food related outbreaks in Nova Scotia, Massachusetts, California and Texas.

Answer 49

Listeria

Question 50

was first isolated from human diarrheal stools in 1971. Since, then it has continually gained recognition as a disease causing organism in humans.

Answer 50

Campylobacter jejuni

Question 51

are harmful byproducts from molds that grow on foods and feeds. They have caused severe illness and death in animals for centuries.

Answer 51

Mycotoxins

Question 52

refers to the growth of a population (or an increase in the number of cells), not to an increase in the size of the individual cell. Cell division leads to the growth of cells in the population.

Answer 52

microbial growth

Question 53

Two Types of Asexual Reproduction in Microbes:

Answer 53

1. Binary Fission - Bacterial reproduction occurs through fission, a primitive form of cell division that does not employ a spindle fiber apparatus.
   2.) Budding - A few bacteria and some eukaryotes (including yeasts) may also replicate by budding, forming a bubble-like growth that enlarges and separates from the parent cell.

Question 54

Requirements for Growth

Answer 54

Ph
Temperature
Food
Acidity
Osmotic pressure
Time
Oxygen
Moisture