What is the titrated acidity of yogurt 90 degrees converted to citric acid?

Calculated from mass fractions

Malic acid 0.067, acetic acid 0.060, tartaric acid 0.075, citric acid 0.070 (with 1 molecule of water of crystallization), citric acid 0.064, lactic acid 0.090, hydrochloric acid 0.036, phosphoric acid 0.033

Acidity can also be expressed as titratable acidity. Titration acidity of buttermilk is achieved by raising the pH in the milk sample being tested to approximately pH 8.4 using an alkaline solution of known concentration, usually with phenolphthalein as an indicator, which changes color from colorless to pink. The experiment actually measures the amount of base required to raise the pH of cow’s milk from 6.6 to 8.4. If bacterial growth causes the milk to become acidic, the amount of alkali consumed in the above experiment increases and the acidity or titratable acidity value of the buttermilk rises.

Acidity can be expressed in a number of ways, depending on the concentration of NaOH used in the experiment:

°SH: i.e. Soxhle Henkle degree, 100 ml of milk sample is titrated with 1/4N NaOH, using phenol-phthalein as indicator.

The standard value is about 7. This method is mostly used in Europe.

°Th: This is the Thrner’s degree. A 100 ml sample of milk, diluted twice with distilled water, is titrated with 1/10 N NaOH, using phenolphthalein as an indicator, and has a standard value of 7. This method is mostly used in Sweden.

°D: Dornic degree. A 100 ml sample of milk is titrated with 1/9 N NaOH, using phenolphthalein as indicator, and the standard value is 15. This method is used in the Netherlands and France.

%I.a. = i.e. lactic acidity. This method is widely used in the United States, USA, Canada, Australia and New Zealand.

Several methods of expressing acidity

°SH

°Th

°D

%I.a.

1

2.5

2.25

0.0225

0.4

1

0.9

0.009

4/9

10/9

1

0.01