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MCIM 224 > 13 The Microbiology of Foods > Flashcards

13 The Microbiology of Foods Flashcards

1
Q

T or F: Sterility in foods is rare.

A

T

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2
Q

List the 3 components of food microbiology.

A
  1. Microbes can be used as, or to make, foods
  2. Microbes which degrade and spoil foods
  3. Microbial diseases transmitted by foods
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3
Q

What two types of factors determine the types of microbes that are able to grow in foods?

A
  1. Intrinsic factors

2. Extrinsic factors

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4
Q

List 4 types of intrinsic factors (inherent characteristics of the food itself) that determine whether microbes are able to grow in food.

A
  1. Water availability (Aw), types of nutrients, pH, etc.
  2. Natural antimicrobial properties of the food
  3. Physical entry barriers
  4. Physical structure of the food
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5
Q

“Fungi tolerate a lower Aw and lower pH than bacteria.”

What intrinsic factor is being described here?

A

Water availability, types of nutrients, pH, etc.

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6
Q

“Skins, peels, shells, etc.”

These are examples of which intrinsic factor?

A

Physical entry barriers

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7
Q

“High sugar concentration or high salt conc. inhibit microbial growth”

What intrinsic factor is being described here?

A

Natural antimicrobial properties of food

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8
Q

“Grinding increases SA and distributes microbes, which promotes microbial growth”

What intrinsic factor is being described here?

A

Physical structure of the food

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9
Q

List 3 types of extrinsic factors (conditions under which the food is stored) that determine whether microbes are able to grow in food.

A
  1. Atmosphere
  2. Temperature
  3. Type of packaging
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10
Q

“Food is kept in a well-ventilated room”

What extrinsic factor does this represent?

A

Atmosphere (O2 presence)

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11
Q

“A food package is permeable to moisture”

Which extrinsic factor is being described here?

A

Type of packaging

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12
Q

“Pizza is kept in the fridge overnight”

Which extrinsic factor is being described here?

A

Temperature

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13
Q

List the 3 components of food microbiology.

A
  1. Microbes can be used as, or to make, foods
  2. Microbes which degrade and spoil foods
  3. Microbial diseases transmitted by foods
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14
Q

What’s another name for microbes who are used directly as food?

A

“Single-cell proteins”

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15
Q

From where are single-cell proteins derived?

A

Cultured fungi OR bacteria

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16
Q

Example of a single-cell protein?

A

“Myco-protein”

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17
Q

Where is myco-protein extracted from?

A

The mycelium of Fusarium fungi

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18
Q

What is found in myco-protein?

A

High protein (no fat or cholesterol)

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19
Q

What is specifically used when we’re talking about foods and beverages produced w/ the aid of bacteria/fungi?

A

The END PRODUCTS of bacterial/fungal metabolism that may contribute to texture or flavour of foods

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20
Q

Name 3 examples of processes that involve the utilization of bacteria for manufacturing foods/beverages.

A
  1. Lactic acid fermentation
  2. Alcoholic fermentation
  3. High-Fructose corn syrup manufacture
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21
Q

Name two genuses of bacteria that’re used in lactic acid fermentation.

A
  1. Streptococcus

2. Lactobacillus

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22
Q

List the steps involved in how S. thermophilus and L. acidophilus produce lactic acid in yogurt.

A

They are added to milk > incubated at ~43ºC > S. thermophilus grows first and makes milk anaerobic and weakly acidic > L. acidophilus grows next and makes milk even more acidic > Lactose gets fermented to lactic acid (adds flavour)

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23
Q

What microorganism is used to metabolize glucose to alcohol?

A

Saccharomyces yeast

24
Q

Species of what three bacterial/fungal genuses are involved in the conversion of cornstarch to high-fructose corn syrup?

A
  1. Bacillus species
  2. Aspergillus species
  3. Streptomyces species
25
Q

How do you know if your food is microbiologically “spoiled”? (2)

A
  1. change in appearance/texture

2. undesirable taste/odour

26
Q

What governs the types of bacterial/fungal species that spoil foods?

A

The intrinsic and extrinsic factors of those specific foods

27
Q

Microbial food spoilage is most often due to…(2)

A
  1. Accumulation of metabolic end products (e.g. acids, gases)
  2. Microbial enzymes breaking down components of the food
28
Q

T or F: Microbial spoilage constitutes a serious health hazard.

A

F

Not necessarily. However, if there’re high numbers of organisms, this may mean that pathogens are also present.

Also, microbial toxins (esp. from fungi) may be present

29
Q

Bacteria-caused food spoilage mostly occurs in what kind of foods?

A

Foods w/ high Aw (water content)

30
Q

These microorganisms are responsible for most food spoilage. Why are they better at causing food spoilage?

A

Yeasts and molds (fungi)

They’re better bc:

  1. They have lower optimal temperatures, pHs, and Aw’s (compared to bacteria)
  2. They release a lot more degradative enzymes during metabolism
31
Q

When are foods that’re spoiled by molds and yeasts considered a health hazard?

A

When toxins are produced (e.g. hallucinogenic alkaloids, carcinogenic aflatoxins)

32
Q

Three methods used to control food-spoilage microbes:

A
  1. Prevent microbes from entering food
  2. Inactivate any microbes which have gained entry
  3. Prevent or slow the growth of microbes in the food
33
Q

What’re two ways to reduce/inhibit the growth of food-spoilage microbes?

A
  1. Lower temp (e.g. fridge)

2. Use preservatives

34
Q

What’re two ways to inactivate food-spoilage microbes that have gained entry into food?

A
  1. Heating

2. Irradiation

35
Q

What type of disease is usually caused by microbial diseases that’re transmitted by foods?

A

GI (“enteric”) diseases

36
Q

Common symptoms of GI diseases?

A
  1. Nausea
  2. Vomiting
  3. Diarrhea
  4. Abdominal cramping
37
Q

T or F: Human pathogens usually use foods as their “home” when outside of the human body.

A

F

Human pathogens DO NOT usually use foods as their “home” when outside of the human body.

Thus, foods act as a “vehicle” for delivery of microbes (or microbial toxins) into the gut

38
Q

How can a pathogen gain entry into foods? (4)

A
  1. From infected human
  2. From infected insects or rodents
  3. From animal fecal material during processing
  4. From the environment (e.g. soil, un-clean processing equipment)
39
Q

List the three microbes in order of MOST likely to cause food-borne diseases to LEAST likely to cause food-borne disease.

A

Viruses > bacteria > parasites

40
Q

The majority of food-borne diseases are caused by _____.

A

viruses

41
Q

Why is it difficult to determine how many GIT-illness-causing microbes are out there.

A

Because GI illnesses are under-reported.

There are 136 total cases of GI illness due to microbes for every 1 confirmed case.

42
Q

What’re the two types of BACTERIAL food-borne diseases?

A
  1. Food-borne intoxications (aka “food poisonings”)

2. Food-borne infections

43
Q

Describe food-borne intoxications (i.e. food poisonings)

A

Bacteria grow on food > they release a “toxin” during growth > bacteria may not survive preparation (e.g. heating), but toxin may persist > toxin is ingested > symptoms of disease appear

44
Q

Describe food-borne infections.

A

Bacteria are present on food > food (with bacteria) are ingested > bacteria multiply in gut > bacteria release toxins and/or penetrate further > symptoms of disease appear

45
Q

Why do symptoms of bacterial food-borne infections appear more slowly than bacterial food-borne intoxications?

A

Food-borne infections require bacterial pop growth in the gut before they can cause disease.

Food-borne intoxications are caused by pre-existing toxins, so they cause diseases much sooner.

46
Q

The entry of LIVE bacteria into the gut IS req’d for this type of bacterial foodborne disease.

A

Foodborne infections

47
Q

The entry of LIVE bacteria into the gut IS NOT req’d for this type of bacterial foodborne disease.

A

Foodborne intoxications

48
Q

T or F: Having food poisoning automatically means that you have an infection.

A

F

Food poisoning means that only the bacteria-produced toxin is present, but not the bacteria themselves.

49
Q

Most common food associated w/ foodborne illnesses?

A

Leafy vegetables

50
Q

What system is used to ctrl the transmission of food-borne diseases at the industry (manufacturing) level, from “farm to fork”?

A

HACCP:

Hazard
Analysis
Critical
Control
Points
51
Q

Summarize how HACCP works to ensure risks of food-borne diseases are minimized (3)

A
  1. Critical points of likely hazards are IDENTIFIED during production
  2. These critical ctrl points are ACTIVELY MONITORED for possible hazards
  3. CORRECTIVE ACTION is needed if a hazard is identified (at any of these critical pts)
52
Q

This is the main cause of foodborne disease at the consumer level?

A

Inadequate refrigeration

53
Q

How is the transmission of foodborne diseases ctrled through active surveillance?

A

A network can actively monitors and investigates and traces enteric disease activity on a national or international level

54
Q

Give 2 examples of networks that monitors food-borne diseases.

A
  1. FoodNet USA

2. FoodNet Canada

55
Q

Transmission of food-borne diseases be ctrled at what three levels? (3)

A
  1. At the industry (manufacturing) level
  2. At the consumer level
  3. At the gov’t level (through active surveillance)
56
Q

Elements of an active surveillance network include: (4)

A
  1. Surveying hospital-based clinical microbiology LABS
  2. Detailed ANALYSIS of the agent causing enteric disease
  3. Surveying primary-care physicians (# of pts reporting GI disease but never tested)
  4. Monitoring GLOBAL TRENDS in foodborne disease outbreaks

MCIM 224 (25 decks)

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