Biochemical Analysis of Milk

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BACKGROUND

Milk is one of the important beverages and an essential part of every individual daily diet. It is filled with important micro and macro nutrients. It is due to its important composition that it is necessary both in childhood as well as adult times. The impact of milk on human health is quantitatively relevant and is therefore a subject of investigation.

So, the basic objective of this experiment is to perform biochemical analysis of milk.

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REQUIREMENTS

Sample:          Milk sample

Chemicals:      Potassium chromate

     0.1N AgNo3

     Phenolphthalein indicator

     0.1N NaOH

     H₂SO₄

     Amyl alcohol

     DMAB solution

Apparatus:      Beaker

     Water bath

     Crucible

     Burette

     Centrifuge machine

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PROCEDURE

Sample preparation

Take the milk sample in a beaker and warm it to a temperature of 37^oC to 40^oC. It is warmed by keeping the beaker containing the milk in water bath. For proper homogenization it should be stirred consistently. Now pour this milk sample back to the bottle for mixing it with remaining residual fat sticked to the sides of the bottle.¹ Then again bring it back to the beaker and allow the milk sample to cool down to room temperature and withdraw for biochemical analysis.

Total solid determination

Take a crucible and weigh it, then take 5 g of the milk in the crucible and keep it in water bath for full dryness. Then keep it in oven and once it is cooled down the weight is measured.²

% of total solid = wt. of crucible with sample after drying – wt. of crucible/wt. of sample × 100

Chloride determination

To about 10 ml of milk sample add 40 ml of water and then add about 9-10 drops of potassium chromate. Then titrate this mixture with 0.1 N AgNO₃ till a brick red precipitate is formed. The total amount of 0.1 N AgNO₃ gives the total content of chloride.

1 ml of 0.1 N AgNO₃=3.55 mg of Cl

Titrable acidity determination

Take 10 ml of milk sample and mix phenolphthalein indicator 1 ml.³ Then titrate it with 0.1 N NaOH 1 ml of 0.1 N NaOH is equivalent to 0.009 g of lactic acid.

Fat determination

In a butyrometer tube take 10 ml of H₂SO₄ and with it mix the sample milk. To this mixture add Amyl alcohol 1 ml, and then close the stopper. Shake it for proper mixing and then keep it in water bath at 65^oC for about 5 min. Then centrifuge it at 1100 rpm for about 4 min. Now remove the tube and again keep it in water bath for about 5 min at 65^oC. Measure the % of fat in the tube.

Urea determination

First prepare the standard curve by pipetting 5 ml of standard solution into TT (5 ml). To each of above solution add 5 ml DMAB solution. Now prepare 5ml buffer and 5 ml DMAB soln as reagent blank. Now properly shake the tubes and keep it undisturbed for about 10 min. Read the absorbance at 420 nm. Preparing the sample, mix 10 ml of trichloroacetic acid to 10 ml of milk sample to precipitate out the proteins and filter it.⁴ Now take 5 ml of this filtrate and add 5 ml of DMAB. At 420 nm the optical density of the yellow colour is measured. From the standard curve now amount of urea is calculated.

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CONCLUSION

The important composition of milk makes it a very healthy drink among the humans.

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REFERENCES

1. Hemme T, Otte J. Status of and prospects for smallholder milk production—a global perspective. Rome: FAO; 2010.
   
2. FAO. Food outlook—global market analysis. Rome: FAO; 2012.
   
3. Davies KM, Heaney RP, Recker RR, Lappe JM, Barger-Lux MJ, Rafferty K, Hinders S. Calcium intake and body weight. J Clin Endocrinol Metab. 2000;85:4635–8.
   
4. Parikh SJ, Yanovski JA. Calcium intake and adiposity. Am J Clin Nutr. 2003;77:281–7.