PARTITION OF MAIN AND TRACE MINERALS IN MILK - EFFECT OF ULTRACENTRIFUGATION, RENNET COAGULATION, AND DIALYSIS ON SOLUBLE PHASE-SEPARATION

A study was carried out on the effect of soluble-phase separation on m ineral distribution in milk. Fractioning was carried out by rennet coa gulation (RC), ultracentrifugation (UC), and dialysis (D) against a la rge volume of water (1:10). Reconstituted skim milk powder was used an d calcium, magnesium, sodium, potassium, phosphorus, manganese, zinc, citrate, lactose, and nitrogen were determined in the soluble fraction . The results of the first two procedures were comparable, except for Zn, which was lower in RC; greater precision was achieved with UC, esp ecially for manganese. On fractioning by dialysis, Ca and Zn levels in the diffusate were higher than in the soluble fractions obtained by U C and RC as a result of long dialysis times (24 h) and low operating t emperature (5 degrees C). With dialysis, Na and K levels in the diffus ate were lower than with the other procedures. Of the three procedures assayed, UC appeared to be the best suited for work in series.