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Food Microbio > Lecture 3 > Flashcards

Lecture 3 Flashcards

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1
Q

What is a good growth media for bacterial growth?

A

Milk

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2
Q

Why is milk a good growth media for bacterial growth?

A

High water content
Neutral pH
Variety of nutrients

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3
Q

What is pasteurization?

A

A rapid heat treatment followed by rapid cooling

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4
Q

What is the purpose of homogenization?

A

Fat particle reduction

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5
Q

What is the purpose of homogenization?

A

Break down fat globules so that the fat is dispersed evenly throughout

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6
Q

What are the two types of contamination?

A

Direct and environmental contamination

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7
Q

What are examples of direct contamination?

A

Animal/human health
Udder health
Residual fecal matter

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8
Q

What are examples of environmental contamination?

A

Atmosphere, water supply, inadequate equipment cleaning, inadequate refrigeration, and cross-contamination.

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9
Q

What are the major bacterial spoiling agents in dairy products?

A

LAB, Psychotropic Bacteria and Coliforms

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10
Q

The over-fermentation of LAB can lead to what?

A

Excessive acid production

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11
Q

What does psychro mean?

A

Cold

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12
Q

What does tropic mean?

A

Grow

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13
Q

True or False. Psychrotropic bacteria grow at refrigeration temperatures and are significant spoilage agents in dairy.

A

True

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14
Q

What type of bacteria produces enzymes that remain active even after pasteurization?

A

Psychrotropic bacteria

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15
Q

What spoils dairy products by producing gas and off odors?

A

Coliforms

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16
Q

What ferments lactose to produce CO2 resulting in gas pockets in cheese and spoilage in fluid milk products?

A

Coliforms

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17
Q

What are common signs of souring?

A

Sour milk and curding

18
Q

What are the causes of souring?

A

Over fermentation of LAB

19
Q

What are signs of ropiness?

A

Slimy, viscous consistency

20
Q

What causes ropiness?

A

Specific types of bacteria that produce extracellular polysaccharides. EPS

21
Q

What causes sweet curdling?

A

Section of proteases

22
Q

What are the signs of sweet curdling?

A

Coagulates without the typical souring associated with lactic acid production

23
Q

What is the primary energy source in milk?

A

Lactose

24
Q

What is fermented to lactic acid?

A

Lactose

25
Q

What remains soluble in milk and is less susceptible to microbial proteolysis?

A

Whey protein

26
Q

What are the two bacterial growth inhibitors found in milk?

A

Lactoferrins and lactoperoxidase

27
Q

What are lactoferrins?

A

Iron binding agents that limit the presence of iron, thus controlling bacterial growth

28
Q

What is lactoperoxidase system?

A

An enzyme that is present in fresh raw milk. Can be reactivated by adding thiocyanate

29
Q

When do spore-forming bacteria form?

A

Low-acid milk products are preserved by sub-sterilization heat treatment and packaged with little chance of recontamination with vegetative cells

30
Q

What are examples of products in which spore-forming bacteria could occur?

A

aseptically packaged milk, cream, sweetened and unsweetened condensed milk

31
Q

What is the most commonly know type of spoilage for produce?

A

Soft rot

32
Q

What is soft rot?

A

When the plant’s structural polymers degrade

33
Q

What are examples of degradative enzymes?

A

Pectinase, cellulase, protease, phosphatidase, dehydrogenase

34
Q

What does cellulase break down?

A

Cellulose –> Glucose

35
Q

What are the two groups that produce can be placed in based on physiological changes after harvesting?

A

Non-climacteric and climacteric

36
Q

Non-climacteric

A

when it stops ripening after harvesting

37
Q

What are contamination sources for produce?

A

Irrigation water
Soil and manure
Wildlife and Livestock
Atmosphere/Weather
Harvesting equipment
Composition of produce (pH, aw, sugar, aroma)

38
Q

True or False. The spoilage of dried fruits is generally caused by osmophilic yeast and xerotolerant molds

A

True

39
Q

What is the purpose of chemical sanitizers?

A

To help prevent cross-contamination by wash water

40
Q

What is the purpose of MAP?

A

Reduced respiration and reduce senescence.

41
Q

True or False. The microbiota of frozen produce is the same as fresh produce.

A

True

42
Q

True or False. All produce undergo some type of processing before reaching the consumer.

A

True

Food Microbio (10 decks)

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