Evidence of heat treated milk

Question 1

Name tests used for evidence of heat treatment:

Answer 1

Storch’s peroxidase test
Phosphatase test
Catalase test

Question 2

Describe Storch’s peroxidase test:

Answer 2

Prove presence or abscence of peroxidase in milk
Inactivation of peroxidase when milk is heated to 80C for a few seconds = when milk is pasterized.
Blue - unpasteurized
Greyblue - raw milk (under 80C)
Grey white - 80*C treated

Question 3

Describe phosphatase test:

Answer 3

Determines if the product recieved the correct treatment
Heat inactivation of alkaline phosphatase at 71-74*C
Reactivation can occur in UHT pasteurized cream/high fat products
White - pasteurized
Cream - +2.5% unpasteurized milk
Pale yellow - +5% unpasteurized milk
Intense yellow - unpasteurized

Question 4

Describe catalase test:

Answer 4

Determine if udder is healthy.
Catalase is destroyed by heating 75*C for 60 seconds.
Aim:
Destroy pathogens & majority of bacteria
Inactivate enzymes
Increase cheese yield

Question 5

Describe the scheme of heat treatment:

Answer 5

Therminization
Pasteurization
Ultra high temperature sterilization
Sterilization

Question 6

What is terminization?

Answer 6

Heating of raw milk at least 15 seconds between 57C and 68C(63*C for 30 min)
After, the milk show positive phosphatase test (not inactivated)

Question 7

Describe pasteurization:

Answer 7

High temperature for a short time.
72C for 15 seconds.
Phosphatase test -, peroxidase test +
Cream: min 90C for a few seconds

Question 8

Describe UHT (ultra high temperature sterilization):

Answer 8

135C for not less than 2-4 seconds
Phosphatase test -, peroxidase test -
Plate count at 30C (per 0.1 ml) < 10
Organoleptic test normal

Question 9

Sterilization:

Answer 9

In container, 115-120 *C for 20-30 min