Detection of Lactic Acid in Milk and Cream

Abstract

The steps involved are saturation with ammonium sulfate, filtering, shaking the filtrate with ethyl ether, separation of the ether layer, neutralization of the acid with alkali, evaporation of the ether, washing of the ethyl ether residue with petroleum ether, taking up the residue with water, heating with sulfuric acid, cooling, and adding guiacol (Denigès test). A red color indicates lactic acid. With care the test is sensitive to down to about 0.002 per cent of lactic acid in the milk. © 1934, American Dairy Science Association. All rights reserved.