Dairy and Milk Science

Question 1

What is pasteurization

Answer 1

invented by Louis Pasteur. a process which uses heat to destroy all pathogenic bacteria from milk and other juices.

Question 2

Does pasteurization kill all bacteria?

Answer 2

no, many non-pathogenic bacteria remain

Question 3

What is one of the most heat resistant pathogenic bacteria in milk? and what temperature is it destroyed at

Answer 3

Q fever bacteria (coxiella burneti) destroyed at 145F at 30 minutes

Question 4

What does milk loose it’s flavor and consistency if cooked too hot?

Answer 4

because the albumin coagulates which changes the sugars, fats and salts in the milk.

Question 5

What are the 5 pasteurization methods

Answer 5

the VAT (Batch) Method
HTST High Temp Short Time Method
High Heat Short Time Method
Ultra High Temperature Method
Instantaneous Method

Question 6

What is the VAT (Batch) Method

Answer 6

145 for 30 minutes typically used for cultured dairy products such as sour cream and yogurt

Question 7

What is the HTST Method (name the three common temperatures and times)

Answer 7

Milk goes through a continuous flow process where it is carefully heated.

161 for 15 seconds
166 for 15 seconds (if Q fever in product)
175 for 25 seconds for high fat products such as ice cream

Question 8

What is the high heat short time method of pasteurization

Answer 8

similar to ultra high temp.

between 191 and 212 for a second or less

Question 9

What is the ultra high temperature method

Answer 9

in a vacuum chamber 194 for 3/4 second

used for high sugar/fat products such as half and half and whipping cream

Question 10

What is one of the benefits of ultra high temp pasteurization

Answer 10

gives a product a very long storage life. some products can even be stored at room temperature

Question 11

What is the instantaneous method of pasteurization

Answer 11

280 for a fraction of a second. not really used because it’s hard to maintain consistent temperature. it is used for some shelf stable dairy creamers

Question 12

Which method has been found to product the best results

Answer 12

high temperature short time

Question 13

What are some of the downfalls of the VAT method

Answer 13

bubbles in the vat can cool the milk resulting in improper pasteurization

to counter act something hot air is blown over the vat

Question 14

What are some downfalls to the HTST method

Answer 14

milk must be preheated first

Question 15

What happens if the milk does not get hot enough as it passes through the coils in the HTST method

Answer 15

it is automatically recirculated back through

Question 16

What are the names of the 5 standards for bacteria in milk

Answer 16

grade A raw milk
grade A pasteurized milk
grade b raw
grade b pasteurized
certified raw milk

Question 17

grade A raw milk

Answer 17

less than 50,000 bacti per ml

Question 18

grade A pasteurized

Answer 18

less than 15,000 bacti per ml (standard plate count)

Question 19

grade b raw

Answer 19

less than 1,000,000 bacti per ml

Question 20

grade b pasteurized

Answer 20

less than 50,000 bacti per ml
typically used for industrial processes (where it will be heated further)
not direct to consumer

Question 21

certified raw milk

Answer 21

same stds as grade a

less than 15,000 bacti per ml

Question 22

how much vitamin D is added to most milk products

Answer 22

400 ius

Question 23

What two vitamins does pasteurization destroy in milk

Answer 23

vitamin D and C

Question 24

What is homogenized milk

Answer 24

milk that has been centrifuged so the fat globules break up into a non settling liquid

Question 25

Name 10 diseases that may be found in milk

Answer 25

brucellosis
bovine tuberculosis
staphylococcus
typhoid
salmonella
streptococcus
septic sore throats
hep a
q fever
scarlet fever

Question 26

how long before the birth and after the birth must milk from a calving cow be disposed of

Answer 26

15 days prior and 5 days after

Question 27

How often are most cows examined

Answer 27

every 6 years

Question 28

milking cows are testing every year for what?

Answer 28

tuberculosis

Question 29

Can milk pails be used?

Answer 29

NO, milk is now collected and stored in bulk storage tanks

Question 30

The average milking cow produces __ to __ gallons of milk per day

Answer 30

5 to 7

Question 31

What is bovine mastitis

Answer 31

aka scarlet fever

a streptoccus infection of the cows udder

Question 32

What would a leucocyle count tell you about a cows health?

Answer 32

it’s a white blood cell count, it will tell you if they have an infection

Question 33

What are 4 foreign substances that can be found in milk?

Answer 33

antibiotics
insecticides
radioactivity
milkstone

Question 34

what are two radioactive materials that have been found in milk?

Answer 34

radioactive strontium and iodine isotopes

Question 35

What are milkstones

Answer 35

build up of calcium and magnesium from milking equipment that can get into milk

Question 36

What is the phosphatase test used for?

Answer 36

to test for the phosphatase enzyme which if present in milk indicates improper pasteurization

Question 37

What is the ring test (blue ring test)

Answer 37

tests for brucellosis in cows. a blue ring will form in the test bottle

Question 38

The methylene blue test is aka as ________ and tests what about milk?

Answer 38

the milk reduction test

tests overall quality of milk, mainly checking to see fi there is a large number of bacteria in the milk sample