Titrimetric Determination of Protein Content of Milk
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DEPARTMENT OF PURE AND APPLIED CHEMISTRYCOLLEGE OF ARTS AND SCIENCESVISAYAS STATE UNIVERSITYVisca ,Baybay, LeyteName: Nonna Fatima H. Abello Date Performed: January 19, 2015Lab. Schedule: M 1:00–4:00 Date Submitted: January 26, 2015Group No. 2EXPERIMENT 6TITRIMETRIC DETERMINATION OF PROTEIN CONTENT OF MILKINTRODUCTION:OBJECTIVES:To know what type of milk has higher amount of proteinTo determine the protein content of milkMETHODOLOGY:To 100 mL glass measuring flask, the group poured 10 mL of milk sample, and added 1 mL of phenolphthalein and 0.4 mL saturated potassium oxalate solution and was left for 2 min. The potassium oxalate removes the disturbing effect of soluble calcium salts. After this, the milk was neutralized into faint color with 0.1M NaOH from a buret. Then, the solution was added 2 mL of 40% formaldehyde solution. The group continue the titration to the same pink color as previously and record the amount of 0.1M sodium hydroxide required for the second titration only and the same as with the third titration.
DATA/RESULTS:Type of MilkAmount of NaOH Used (on second titration)Amount of Titrant per 100 mL sample%ProteinCoco Milk4.3 mL4.3mL*10 = 43mL43*0.17 = 7.31%Non-fat Milk3.2 mL3.2mL*10 = 32mL32*0.17 = 5.44%Low-fat Milk3.3 mL3.3mL*10 = 33mL33*0.17 = 5.61%DISCUSSION:Proteins are macromolecules that play a crucial role in nutritional growth and development. These large biological molecules contain at least one long chain of amino acid residues and are responsible for a multitude of biological functions, including DNA replication and repair, catalyzing metabolic reactions, and providing structure and communication in and between cells. The digestive breakdown of proteins into amino acids provides an important source of fuel and dietary nitrogen. Milk naturally contains a number of key nutrients, including protein, which is beneficial to humans regardless of their age. Globally, milk is a commonly consumed food product that, due to its high nutrient composition, is regarded as highly beneficial for growth. In cow and sheep milk the percent protein can range from 3.3% to 5.8%. For estimating the protein content of milk, we can use this equation (%Protein = T x 0.17) where T refers to the volume of 0.1M NaOH required to neutralize the acidity produced in 100 mL in milk. It may also be used for estimating non-fat milk solids present in ice cream. ). The influence of nutrition on milk protein has been variable, but increasing energy intake and dietary crude protein have been associated with small increases in milk protein content. Improving the supply of methionine and lysine have resulted in increases in milk protein content. Dietary fat has consistently been associated with reductions in milk protein content and increases in milk protein yield. Milk protein content is negatively correlated with milk yield. Thus, as milk yield increases we would expect protein content to decrease. The decrease is small, but we would expect protein in milk at 70 lbs to be 2.92% and at 80 lbs to be 2.89%.