Milk Acidity – test for Quality and Freshness
Measuring Titratable Milk Acidity in Dairy Products
The HI84529-01 uses methods based on AOAC International and Standard Methods for the Examination of Dairy Products. Both of these methods report titratable milk acidity as % lactic acid and a conversion factor is used to convert the results to the other available units. The HI84529-01 can be customized to meet the needs of any dairy analysis lab. Samples can be titrated by weight or volume, diluted or non-diluted (low range only) and titrated to a fixed pH endpoint that can be adjusted by the user. The HI84529-01 offers three different methods depending on the expected range and the weight of sample used. Select low range 50 to titrate a 50 mL or 50 g undiluted sample. The other titration options are low range 20 and high range 20 to titrate 20 mL or 20 g samples that are diluted twice their volume with deionized or distilled water.
There are two fundamentally different measurements of dairy products: titratable acidity and pH. pH is a measurement of hydrogen ion concentration while titratable acidity is the neutralizing capacity of a dairy product with NaOH. An increase in acidity can be caused by bacteria formation. Monitoring acidity is a way of determining the quality and freshness of dairy products. Acidity is determined by a pH endpoint titration using NaOH (sodium hydroxide) and is defined as the consumption necessary to shift the pH value from 6.6 (corresponding to fresh milk) to a pre-determined pH value. When using phenolphthalein as an indicator, a faint pink color change occurs at pH 8.3.
Titratable acidity is expressed in a variety of units based on the titration method performed. Each method varies in sample size and strength of NaOH used for the titration.
% Lactic Acid (%l.a.): Determined by taking a 20 mL or 20 g sample and diluting with twice its volume with deionized or distilled water. The sample is then titrated with 0.1 M NaOH to a phenolphthalein endpoint.
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