Field Test for Titratable Acidity in Milk

A field test was developed to enable milk haulers to assess titratable acidity at pickup. The test involved adding a volume of milk to a set volume of standard base in calibrated screwcapped test tubes. Judgment was based on final color after adding phenolphthalein. No color change indicated titratable acidity above a chosen cutoff point, and the typical pink color of phenolphthalein indicated milk with titratable acidity at or below the cutoff point. Of 116 samples examined by tlie field test, 4 failed to give the correct reaction, and these were ≤.01% from the cutoff point when titratable acidity was determined by titration. A survey of 192 samples of raw manufacturing and Grade A milk samples showed a mean titratable acidity of .164% with no significant difference between grades or seasons.