Importance of Microbes in Foods

Question 1

What is food microbiology?

Answer 1

The study of the microorganisms which inhabit, create or contaminate food.

Question 2

What are the components of Food Microbiology?

Answer 2

1. Food Safety
2. Food Spoilage/Food Preservation
3. Food Fermentation

Question 3

Where do microbes come from in foods? Give examples.

Answer 3

1. Natural sources
   Eg. Plants - the surface of fruits, vegetables and grains; damaged tissues and pores of some tubers.
   Animals - skin, hair, feathers, gastrointestinal tract, urinogenital tract, respiratory tract, milk ducts
2. External Sources
   E.g. Air, Soil, Sewage, Water, Feeds, Humans/other animals, food ingredients, equipment/utensils, packaging, insects.

Question 4

The microbial flora of food consists of:

Answer 4

1. The microorganisms associated with raw materials
2. Microorganisms introduced during the harvesting, handling and processing
3. Microorganisms surviving any preservation treatment and storage

Question 5

List the Good, Bad and Ugly of Microbes in foods.

Answer 5

Good: Food Production (Fermentation, Vitamins etc)
Bad: Food Pathogens (Salmonella, Campylobacter etc)
Ugly: Food Spoilage (Black rot etc)

Question 6

Why are microorganisms used in food production?

Answer 6

Because microorganisms produce desirable flavours and textures and also inhibit pathogenic organisms

Question 7

What are some ways microorganisms are used in food production?

Answer 7

1. Fermentation
2. Food Supplements/Beneficial Bacteria
3. Biopreservation
4. Agriculture

Question 8

State the benefits of fermenting foods.

Answer 8

1. Fermentation makes food more nutritious, tastier and easier to digest
2. Enances food safety because it helps to preserve food

Question 9

List the categories of fermented foods and give examples.

Answer 9

1. Fermented meat products - eg. sausages
2. Fermented dairy products - yoghurt, cheese
3. Fermented vegs and fruits - pickles, sauerkraut, soy sauce
4. Fermented beverages - wines, bears, rum

Question 10

What genera do most fermented bacteria belong to?

Answer 10

• Streptococcus
  2. Lactobacillus
  3. Leuconostoc
  4. Pediococcus
  5. Micrococcus

Question 11

How do these microbes preserve food?

Answer 11

By conversion to sugars to lactic acid that would have been used by competing microbes; Inhibits the growth of some organisms

Question 12

What microorganisms are used in the production of vinegar?

Answer 12

1. Acetobacter
2. Gluconobacter

Question 13

What species of yeast is used to produce ethanol and CO2 and is used in the processes of brewing and baking?

Answer 13

Saccharomyces

Question 14

List the food supplements that are made from microorganisms.

Answer 14

Vitamins, Amino acids and Probiotics

Question 15

Which two vitamins are produced by microorganisms?

Answer 15

Vitamin B12 and riboflavin

Question 16

Which amino acids are produced using microorganisms?

Answer 16

Glutamic acid, aspartic acid, phenylalanine and lysine

Question 17

Define probiotics

Answer 17

Products containing living microorganisms, which in certain numbers exert health benefits beyond inherent general nutrition.

Question 18

What benefits do probiotics offer the gastrointestinal tract?

Answer 18

1. provides protection against enteric pathogens
2. supply enzymes to help metabolize foods
3. Detoxify harmful food components and metabolites that can cause cancers
4. Stimulate the intestinal immune systems
5. Improve intestinal peristaltic (Peristalsis is a series of wave-like muscle contractions that move food through the digestive tract) activity

Question 19

How do microorganisms contribute to biopreservation?

Answer 19

By producing different antimicrobial compounds
These compounds have bacteriostatic (prevents the growth of bacteria), bacteriocidal (kills the bacteria), fungistatic (inhibiting the growth of fungi) and fungicidal (kills the fungi) actions against organisms that cause food spoilage and food-borne diseases.
They are safe microorganisms

Question 20

Give examples of the different antimicrobial compounds that are produced by these microorganisms.

Answer 20

Organic acids, diacetyl, H202, reuterine, bacteriocins and enzymes

Question 21

How are microorganisms important in the agricultural industry?

Answer 21

1. Biological control and bioinsecticides: the control of an agricultural pest or disease-causing organism by a microorganism or microbial toxin to prevent infection of a plant
2. Vaccines
3. Fertility of soil and symbiotic associations with plants
   eg. Mycorrhizaea - a fungus plant root association
   Rhizobium (nitrogen fixation) - these bacteria in root nodules convert atmospheric nitrogen into fixed nitrogen that the plant uses for growth.
4. Ruminant Animals - microorganisms responsible for carrying out the digestion process.
5. Cycling of nutrients- nutrients like carbon, nitrogen and sulphur

Question 22

What are the five major (traditional) groups of pathogenic bacteria?

Answer 22

1. Salmonella and Shigella
2. Clostridium botulinum
3. Clostridium perfringens
4. Bacillus cereus
5. Staphylococcus aureus

Question 23

List the emerging pathogenic bacteria.

Answer 23

1. Yersinia enterocolitica
2. Escherichia coli
3. Listeria monocytogens
4. Campylobacter jejuni

Question 24

Which one of the following does not reproduce in foods and is not competitive in causing food-related illnesses?
A. bacteria
B. Molds
C. Yeasts
D. Viruses

Answer 24

D

Question 25

______ and _____ usually grow more slowly than bacteria and are rarely a problem in foods that support bacterial growth.

Answer 25

Yeasts, Molds

Question 26

What are some of the reasons foodborne diseases are still a major cause of death in both developing and developed countries?

Answer 26

1. Controlled food processing preceded by uncontrolled food production, mishandling in distribution/sale or the purchaser’s kitchen
2. Increased volumes of products from a single manufacturing source which leads to increased mass catering leads to more massive contamination and bigger food outbreaks
3. Canning replaced by freezing. Canning usually kills pathogens as opposed to freezing
4. Worldwide distribution of food serves as an unintentional spread of food-borne microbes.
5. Underdeveloped countries’ preference for pre-processed and street-vended meals and developed countries’ increased preference for fresh undercooked or raw foods enhances the chain of infection
6. Lag in the transfer of technologies into the regulatory chain
7. Animal husbandry has been more intensive over the years and more and more animals have become asymptomatic carriers of human enteric pathogens.
8. Public is still not sufficiently informed or concerned to be able to distinguish good from bad practices

Question 27

Why would one expect the incidence of foodborne illnesses to be significantly lower than they are in actuality?

Answer 27

1. Increased public awareness of bacterial food-borne illnesses
2. regulations and technologies geared towards food safety
3. increased sanitation

Question 28

What are some disadvantages of food spoilage?

Answer 28

1. Economic loss
2. Loss of consumable foods
3. Affects the availability of food