Milk Titration

Titration of Milk
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In the food industry titration is used to determine many things from the acidity in cheese and orange juice to the fat content in yogurt and sugar in pudding. 
We will look in depth at the process of milk production; predominantly the acidity of the liquid.

The standard pH level of fresh milk is between 6.6-6.8 but because the acidity of the liquid plays such an important part in the taste and quality of the product it must be tested to be sure it meets the standards. Therefore dairy farmers use titration to determine the pH of a small sample of milk and determine it's pH.

The steps are as follows:
Take a small sample of milk (ie: 10mL)
Add a few drops of a pH indicator solution (ie: 3 drops of phenolphthalien or methyl blue)
Using a burette containing 0.1M of a base (ie: NaOH)
Add drops of the base until the colour of the milk changes colour. This is your endpoint and you can begin calculating to find the pH of the milk. (Let's assume that 5mL of NaOH was added to reach the endpoint)
Once you know the amount of the 0.1M base added and knowing the amount of milk you started with you can determine the pH of the milk using stoichiometry. We can find the moles of NaOH used by multiplying the molarity and the volume: 0.1M x .005L=0.0005moles NaOH

Milk (10mL, unknown pH) + NaOH (0.1M, 5.0mL=0.0005moles) ------> Solution (15mL, pH 8.0)
This information here allows us to determine the pH because we know that the 5.0mL of NaOH raised the pH of the milk to 8.0 because that is the level where phenolphthalien turns pink.
The calculations for this step require us to know how much the acid in milk reacts with the OH in the base. We can then determine the original pH of the milk by comparing the endpoint pH with the neutralization reaction (the moles used).

This is an example of how titration is easily used in the food industry to perform routine checks on common products such as milk. With the technology available today...