MILK & MILK PRODUCTS

Formulae for the Estimation of Solids-not-Fat (SNF) and Total Solids Content in Cow and Buffalo Milk in India

October 2, 2023

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Formulae for the Estimation of Solids-not-Fat (SNF) and Total Solids Content in Cow and Buffalo Milk in India

Milk testing for quality assurance is an essential component of any milk processing industry. Chemical quality control and assurance tests are designed to ensure that the milk and dairy products meet accepted standards for compositional parameters and purity as well as levels of different components. Raw milk of good quality is the basis for the production of high quality dairy products. Milk payment strategies differ across the world as the markets, product portfolios, consumer and farmer preferences change. Pricing policy is very important for any organized enterprises. It should comply with the standards laid by the law regulating agencies. The initial good quality milk is allocated high price. Pricing in many countries depends mainly on the quantity of milk and fat and SNF% (Sandhu, S. S. 2003). In most of the countries, the following chemical quality characteristics have been set for raw milk reception; (a) fat percentage, (b) total solids (TS) or solids-not-fat (SNF) percentage (c) protein content and (d) the temperature (°C) of received milk. Based upon the chemical analysis results, raw milk is graded. In milk, fat and Snf are variable, in India pricing of milk is based on quantity and quality i.e. fat and Snf content of milk. To ensure the quality of milk, the minimum standards for milk have been fixed by the legal authorities “Food Safety Standard Authority of India (FSSAI).The Richmond’s formula using specific gravity lactometer has been widely used in our country for calculating the solids-not-fat in cows and buffaloes milk. By using this formula wide variations in the results with gravimetric method have been reported by different workers. A slight error in the estimation of fat and SNF, especially when the milk is handled in large quantities in a dairy plant, can result in big discrepancies in the balance sheets and recovery amounts (Bector and Sharma, 1980). Usually fat will be estimated by Gerber, Mojonnier and instrumental methods. Most commonly used method for fat estimation is Gerber, but Mojonnier method is the reference (standard) method for fat estimation. The determined level of SNF in milk varies somewhat with the method of estimation. Gravimetric method is the standard and accurate method for estimation for SNF. However, this method is time consuming and demands a better analytical skill. Lactometric methods are rapid and simple. Now a day’s different states using different formulae and different lactometers for the estimation of Solids not fat and total solids in milk but most of the formulae underestimates Snf by >0.2%.Therefore, the present study is being undertaken to bring %SNF estimated by formula method maximum near to gravimetric method by developing a possible uniform formula for determination of SNF and TS contents in both cow milk and Buffalo milk. In conclusion the milk, fat and Snf are variable, in India pricing of milk is based on quantity and quality i.e. fat and Snf content of milk and to meet legal standards, in order to get Snf value very near to gravimetric value many things play a role i.e. type of the formula, type of lactometer, temperature of measurement and accuracy of glassware. Existing formulae will underestimate >0.2%SNF.Developed formulae in case of cow milk at 27°C 91.52 and at 29°C 91.93% samples are in the acceptable range (within 0.2% error) and in case of buffalo milk at 27°C 80.24 and at 29°C 77.33 % of samples are in the acceptable range.

Determination Of S.N.F. (Solid Not Fat) And Total Solids Of Milk

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.

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:

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.

Compiled & Shared by- This paper is a compilation of groupwork provided by the

Team, LITD (Livestock Institute of Training & Development)

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Reference-On Request.

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