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BACKGROUND
Milk and all dairy product are vital human food staple and is very much required for maintaining a balance in everyday diet. There are a number of dairy products available that are sourced from various animals like whole milk of sheep, goat milk, cheese and also for baby’s milk formula that contains milk solids. Cheese is an important dairy product available in the market. It is consumed by almost 90% population in the whole world. Therefore, it is important to know about the various properties and ingredients present in the cheese.
The main objective of this experiment is to perform biochemical analysis of cheese.
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REQUIREMENTS
Sample: Cheese
Reagents: HCL
H2SO4
0.05 M NaOH
Apparatus: Flat-bottom dishes with lid
Hot air oven
Desiccator
Sand
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PROCEDURE
Preparation of cheese sample for biochemical analysis
Take cheese sample and pass it through 8 mesh sieves 3 times or in the other way you can grate the sample and mis it properly. Now transfer this sample into a container which is properly air tight till analysis. Biochemical analysis should be carried out as soon as possible for better results. If due to some unavoidable circumstances it is not possible to analyze the sample, proper precautions should be taken to avoid the moisture condensation inside the container. The temperature should be maintained at 10oC.1
Analysis for moisture content in cheese
Take the flat bottom metal dish and keep 20 g pf sand and heat it in the hot air oven for about 1 hour. Keep stirring in small interval. Then transfer it to a desiccator for about 30-40 min for cooling it. Now take about 3 g of the prepared cheese sample in the metal dish. Now add little drops of distilled water to the sand to properly saturate it and mix the cheese sample with the sand with constant stirring with the rod, to avoid formation of lumps and even spreading of the sample over the metal dish. Now keep this set up in a boiling water bath for about 20-30 min. Clean the bottom of the dish by wiping it with a cotton cloth. Now transfer this dish to a oven maintained at a temperature of 102oC for about 4 hours. Then transfer it to a desiccator for cooling by replacing the lid. Now accurately weight 0.1 mg of the sample. Now again dry this sample, allow it to cool down and again weigh it, until the difference between successive weight is 0.5 mg. Record the final weight.2
Moisture % by mass in cheese = M1-M2/M1-M × 100
Where,
M = mass in g, of the empty dish along with the glass rod;
M1 = Preliminary mass in g of the dish, lid, glass rod laterally with the material occupied for analysis;
M2 = the final mass in g of the dish, lid, glass rod laterally with the material after drying.
Analysis of fat in cheese sample
Take about 1-2 g of the prepared cheese sample in beaker of 100 ml volume. To it add conc. HCl (10 ml). In a Bunsen burner heat it with frequent stirring in a glass rod. Allow it to cool down to room temperature. To the beaker add ethyl alcohol 10 ml and then transfer this to a Mojonnier fat extracting flask. Take 10 ml of H2SO4 and with it mix the sample milk. To this mixture add Amyl alcohol 1ml, and then close the stopper. Shake it for proper mixing and then keep it in water bath at 65oC for about 5 min. Then centrifuge it at 1100 rpm for about 4min.Now remove the tube and again keep it in water bath for about 5 min at 65oC. Measure the % of fat in the tube.3
Analysis for protein content in cheese
Take 20 g of cheese sample and blend it with 80 g of hot 0.05 M NaOH for about 5 min in order to get a very homogeneous mixture. Then transfer this mixture to a volumetric flask of 100 ml, allow it to cool down and then make the final volume with distilled water. Now with the help of a calibrated syringe take 2.24 ml of the mixed sample and transfer it to a 2 oz polyethylene sample bottle. Determine the sample weight. Now with the help of tomatic pipette add 40.44 g of dye reagent solution to a sample from which protein content was determined.3
Protein % = 100 [ V Co – (V + v) c]/0.312 W x 5
C = concentration of unbound dye in filtrate (mg / ml)
Co = original dye concentration (mg / ml)
V = volume of reagent dye solution
v = volume of sample
W = mg of sample
0.312 = dye binding capacity
5 = constant dilution factor
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CONCLUSION
This reliable and easy method helps in proper analysis of various important constituents of cheese.
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REFERENCES
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Douglas FW Jr., Greenberg R, Farrell HM Jr, Edrnondson LF. Effects of ultra- high-temperature pasteurization on milk proteins. J Agric Food Chem. 1981;29:11.
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Elfagrn AA, Wheelock JV. Heat interaction between a-lactalbumin, 3-actoglobulin, and casein in bovine milk. J Dairy Sci. 1978;61:159.
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Fiske CH, Subarrow Y. The colori-metric determination of phosphorus. J Biol Chem. 1925;66:375.
