PHYSICOCHEMICAL AND BACTERIOLOGICAL ASPECTS OF PRESERVED MILK SAMPLES AND THEIR EFFECT ON FAT PERCENTAGE AS DETERMINED WITH THE MILKO-TESTER1

Abstract

Milko-Tester results decrease as a milk sample ages before analysis. Since no fat is physically removed, this phenomenon could be termed apparent fat loss. Reasons are advanced why the Milko-Tester shows lower results on stored samples. Bacteria counts, oiling-off determinations, and acidity titrations were made on preserved milk samples to show their possible relationship to apparent fat loss. It is believed that changes in fat globule membrane material are key factors that affect the optical properties utilized by the Milko-Tester and are responsible for depressed fat percentages. High initial bacteria count may be the major and primary factor responsible for apparent fat loss in preserved samples held at room temperature. Bacteria have been demonstrated to grow in the presence of potassium dichromate preservative. Under certain conditions preserved milk samples showed no apparent fat loss and could be tested accurately with the Milko-Tester up to 20 days.