Determination of S.N.F. (Solid Not Fat) and Total Solids of Milk
Objectives:
To estimate the level of Total solid content of milk.
To decide the quality of milk on the basis of total and SNF.
Relevant Information:
Total solids content is the entire residue left after complete evaporation of water from milk. This includes fat protein, lactose and mineral matter. These solid constituents exist in milk in a mechanical mixture.
I) Total solids can be determined by
i) Gravimetric method
ii) By use of formula
iii) By Richmond’s scale.
1. Precautions:
As per exercise 3 (B)
Material Required: Milk
Apparatus:
i) Specific gravity bottle
ii) Balance
iii) Porcelain dish
iv) Hot air oven
v) Tongs
vi) Hot water bath.
vii) Desiccators
viii) Glass jar
ix) Lactometer
x) Dairy floating thermometer
xi) Petri plate/dish
Procedure:
I) Gravimetric method:
i. This is an accurate method but not practicable and hence is not used.
ii. Take flat bottomed 50 cm diameter porcelain crucible.
iii. Clean and dry in hot air oven for 1 ½ hour.
iv. Not the weight of crucible.
v. Add 5 ml of milk sample and weight it.
vi. Put the crucible in hot air oven adjusted at 100 0 C for 3 to 4 hours.
vii. Remove the crucible from oven and cool in desiccators’ and weight.
viii. Again put the crucible for ½ hour in oven.
Remove the crucible from oven and cooled in desiccators’ and weigh.
This process should be continued/repeated till getting the constant weight or difference in last two weights should not exceed 0.01 gm. The total solids are determined by formula.
Weight of residue
Total solids % = ————————————————– x 100
Weight of milk sample
II) By use of Formula:
i) Determine the fat percentage of milk sample by Gerber’s method.
ii) Take out the lactometer reading and temperature of milk and calculate.
Corrected lactometer.
iii) Place the figures of fat and CLR in the following formula for calculating total solids and solids not fat.
Richmond’s Formula:
CLR
Total solids % = ———————– + 1.21 F + 0.14
4
CLR
SNF % = ————————— + 0.21 F + 0.14
4
ISI Formula:
CLR
T.S. % = ————————– + 1.22 F + 0.72
4
CLR
SNF % = ————————- + 0.22 F + 0.72
4
Where CLR = Corrected lactometer Reading
F= Fat content in milk
III) By Richmond’s Scale:
To have immediate results the total solids content is determined by Richmond’s scale. The mechanical device made in the form of a ruler with a sliding centre slip. The total solids can be determined if lactometer reading, temperature of milk and fat content is known. The observed lactometer reading is placed opposite the little arrow at 60 0 F on the temperature scale. The corrected lactometer is observed opposite the line indicating observed temperature of milk. This would give the corrected lactometer reading. Next, the arrow on the sliding portion is placed against the fat content of the given milk and bottom part of scale would give the percentage of total solids opposite to the CLR reading on small scale
