Determination of specific gravity and freezing point

Question 1

What is specific gravity:

Answer 1

The ratio between the density of the substance (milk) and water

Question 2

Describe determination by use of lactometer:

Answer 2

Milk sample is placed in a measuring sylinder
Temperature of the sample is taken
(density varies according to temperature)
Lactometer (cylindrical glass slide) is slowly placed until it floats freely
(g/cm3)
L = 1000x valuel in g/cm3 - 1000
If the temp is above or below 20*C, we use a table (add L_20)

Question 3

Density normally values between:

Answer 3

1.0290-1.0330 g/cm3 or 29-33*L

Question 4

How is freezing point determined?

Answer 4

By molarity of solutes, mainly lactose and electrolytes, which create a constant osmotic pressure in milk (0.69 MPa)

Question 5

What is freezing point used to determine?

Answer 5

If there is added water
The lactose content
Estimate of whey powder in skim milk powder
Water activity in cheese

Question 6

What is the legislated freezing point of bovine milk?

Answer 6

-0.520 *C