Lecture 3

Question 1

What is a good growth media for bacterial growth?

Answer 1

Milk

Question 2

Why is milk a good growth media for bacterial growth?

Answer 2

High water content
Neutral pH
Variety of nutrients

Question 3

What is pasteurization?

Answer 3

A rapid heat treatment followed by rapid cooling

Question 4

What is the purpose of homogenization?

Answer 4

Fat particle reduction

Question 5

What is the purpose of homogenization?

Answer 5

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

Question 6

What are the two types of contamination?

Answer 6

Direct and environmental contamination

Question 7

What are examples of direct contamination?

Answer 7

Animal/human health
Udder health
Residual fecal matter

Question 8

What are examples of environmental contamination?

Answer 8

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

Question 9

What are the major bacterial spoiling agents in dairy products?

Answer 9

LAB, Psychotropic Bacteria and Coliforms

Question 10

The over-fermentation of LAB can lead to what?

Answer 10

Excessive acid production

Question 11

What does psychro mean?

Answer 11

Cold

Question 12

What does tropic mean?

Answer 12

Grow

Question 13

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

Answer 13

True

Question 14

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

Answer 14

Psychrotropic bacteria

Question 15

What spoils dairy products by producing gas and off odors?

Answer 15

Coliforms

Question 16

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

Answer 16

Coliforms

Question 17

What are common signs of souring?

Answer 17

Sour milk and curding

Question 18

What are the causes of souring?

Answer 18

Over fermentation of LAB

Question 19

What are signs of ropiness?

Answer 19

Slimy, viscous consistency

Question 20

What causes ropiness?

Answer 20

Specific types of bacteria that produce extracellular polysaccharides. EPS

Question 21

What causes sweet curdling?

Answer 21

Section of proteases

Question 22

What are the signs of sweet curdling?

Answer 22

Coagulates without the typical souring associated with lactic acid production

Question 23

What is the primary energy source in milk?

Answer 23

Lactose

Question 24

What is fermented to lactic acid?

Answer 24

Lactose

Question 25

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

Answer 25

Whey protein

Question 26

What are the two bacterial growth inhibitors found in milk?

Answer 26

Lactoferrins and lactoperoxidase

Question 27

What are lactoferrins?

Answer 27

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

Question 28

What is lactoperoxidase system?

Answer 28

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

Question 29

When do spore-forming bacteria form?

Answer 29

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

Question 30

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

Answer 30

aseptically packaged milk, cream, sweetened and unsweetened condensed milk

Question 31

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

Answer 31

Soft rot

Question 32

What is soft rot?

Answer 32

When the plant's structural polymers degrade

Question 33

What are examples of degradative enzymes?

Answer 33

Pectinase, cellulase, protease, phosphatidase, dehydrogenase

Question 34

What does cellulase break down?

Answer 34

Cellulose --> Glucose

Question 35

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

Answer 35

Non-climacteric and climacteric

Question 36

Non-climacteric

Answer 36

when it stops ripening after harvesting

Question 37

What are contamination sources for produce?

Answer 37

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

Question 38

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

Answer 38

True

Question 39

What is the purpose of chemical sanitizers?

Answer 39

To help prevent cross-contamination by wash water

Question 40

What is the purpose of MAP?

Answer 40

Reduced respiration and reduce senescence.

Question 41

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

Answer 41

True

Question 42

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

Answer 42

True