Microbial Control In Foods

Question 1

Examples for biological control of microbial growth ?

Answer 1

Controlled acidification, bacteriocin, probiotics

Question 2

Actions of microbial control agents

Answer 2

Alternation of membrane permeability
Damage to proteins
Damage to nucleic acids

Question 3

Effectiveness of antimicrobial treatment depends on

Answer 3

Number of microbes
Environment
Time of exposure
Microbial characteristics

Question 4

Heat treatments used commercially

Answer 4

Blanching

Pasteurization

Question 5

What is blanching

Answer 5

Briefly pass through boiling water

Question 6

Does pasteurization kill all the pathogens

Answer 6

No

Question 7

Pasteurization —–pathogens
Kill ?
Inactivates ?

Answer 7

Inactivates

Question 8

What is the major site of sub-lethal heat induced injury

Answer 8

Cell membranes

Question 9

Destruction of a pure culture , by moist heat at a constant temperature, results in…

Answer 9

Negative exponential kinetics

Question 10

Bacterial death is

Answer 10

Logarithmic

Question 11

D value aka

Answer 11

Decimal reduction time

Question 12

What is D value ?

Answer 12

Time necessary at T to reduce the population by 90%

Or time necessary at T for the survivor curve to transfer one log cycle

Question 13

1 log reduction means

Answer 13

90% reduction,

10% survival

Question 14

When D value is higher the survivor curve

Answer 14

Is flatter because it takes longer to have 1 log reduction

Question 15

D values are —- specific

Answer 15

Process

Temperature

Question 16

Z value

Answer 16

Temperature change to result in a 10 fold change in the D value

Question 17

What is autoclave

Answer 17

Steam under pressure

Question 18

Classic method of pasteurization

Answer 18

Milk was exposed to 65 C for 30 min

Question 19

What is the pasteurization method used for milk today

Answer 19

High temperature short time pasteurization (HTST)

Question 20

HTST

Answer 20

Milk is exposed to 72 C for 15 sec

Question 21

Ultra high temperature pasteurization

Answer 21

Milk is treated at 140 C for 3 seconds and then cooled every quickly in a vacuum chamber

Question 22

What is the advantage of milk pasteurization

Answer 22

Pasteurized milk can be stored at room temp for several months

Question 23

Freezing

Answer 23

Temp below 0

Question 24

Freezing can be divided to

Answer 24

Flash freezing

Slow freezing

Question 25

Does flash freezing kill most bacteria

Answer 25

No

Question 26

Why is slow freezing harmful

Answer 26

Ice crystals disrupt cell structure

Question 27

What is lyophilization

Answer 27

Freeze drying

Question 28

Advantage of sublimation

Answer 28

Texture will be less affected

Question 29

What is an essential oil ?

Answer 29

Concentrated hydrophobic liquid containing volatile aroma compounds from plants

Question 30

What kind of essential oils have antimicrobial effects on fresh produce

Answer 30

Clove Basil Lemongrass Thyme

Question 31

What is the effect of emulsifier on emulsion

Answer 31

Stabilize it

Question 32

Why do we ferment foods

Answer 32

- Food preservation - Change in organoleptic characteristics - Money

Question 33

Fermentation takes place in the presence or absence of oxygen

Answer 33

Absence

Question 34

What are the major fermentation used

Answer 34

Lactic Propionic Ethanolic

Question 35

Most important bacterial starter cultures

Answer 35

Lactate Acid Bacteria | LAB

Question 36

Bacterial started cultures belong to 4 categories

Answer 36

Lactococcus Streptococcus Lactobacillus Leuconostoc

Question 37

How is yogurt produced

Answer 37

By the controlled fermentation of milk by 2 species of bacteria

Question 38

What are the 2 species of bacteria that are used in making yogurt?

Answer 38

Lactobacillus bulgaricus | Streptococcus thermophilus

Question 39

How does curd form in yogurt ?

Answer 39

The sugar in milk called lactose is fermented to lactic acid and it is this that Caucasus the characteristic curd to form

Question 40

How does streptococcus thermophilus affect milk

Answer 40

Brings the PH down to 5.5

Question 41

How does lactobacilluls Bulgaria help in making yogurt

Answer 41

It converts lactose to lactic acid

Question 42

At the end of incubation pH may fall to as low as

Answer 42

4.2-4.4

Question 43

-------coagulates the remaining milk proteins causing the yogurt to thicken

Answer 43

Lactic Acid

Question 44

What gives raw yogurt its characteristic flavor ?

Answer 44

Acetaldehyde

Question 45

What is bacteriostatic effect

Answer 45

Low temp Reduces metabolic rate of most microbes so they cannot reproduce or produce toxins

Question 46

What is fermentation ?

Answer 46

Any partial breakdown of carbohydrates taking place in the absence of oxygen

Question 47

How is acetalehye produce

Answer 47

It is a metabolic by product of both species

Question 48

How long is the incubation of yogurt

Answer 48

12 hrs at 32 C

Question 49

How does homogenization make pasteurized milk more stable ?

Answer 49

It makes fat globule smaller

Question 50

What is the liquid portion of milk called after treatment with rennin

Answer 50

Whey

Question 51

Where do they obtain rennin from

Answer 51

From the stomach of young calves

Question 52

What does rennin do

Answer 52

It causes the milk protein ( casein ) to clabber

Question 53

In Cheese making milk is treated with what bacteria

Answer 53

Lactic acid bacteria and enzyme called Rennin

Question 54

Before being sold and eaten, the cheese must age how long ?

Answer 54

From 60 days to several years