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The Alkalinity of Milk Ash and its Relation to the Detection of Neutralizers in Dry Milks. I. Dry Skim Milk^*

Division of Dairy Husbandry, University of Minnesota, University Farm, St. Paul, Minnesota

ABSTRACT

Samples of unneutralized dry skim milk were obtained from commercial drying plants to determine the variation which could normally be expected in the ash alkalinity, as determined by the Tillmanns-Bohrmann method. The ash alkalinity of 115 samples was found to vary within the range of 66.0 to 127.0 expressed as the milliliters of 0.10 normal hydrochloric acid required to titrate the ash from 100 grams of dried skim milk. The average ash alkalinity of these samples was 96.8. The samples of dry skim milk were obtained over a period of one year, and during that time no significant seasonal variations were apparent.

The milk from different breeds of cows was studied to determine whether there were variations in the ash alkalinity of the milk due to breed. Considerable differences were consistently found in the milk from the breeds studied. The ash alkalinity of dry skim milk from Holstein milk was greater than the ash alkalinity of dry skim milk from Guernsey or Jersey milk.

The effect of added neutralizers on the ash alkalinity of dry skim milk was studied. It was found that when sodium bicarbonate, sodium sesqui-carbonate or calcium hydroxide was added to skim milk in amounts sufficient to reduce the titratable acidity as little as 0.01 per cent, the ash alkalinity of the dry product was measurably increased. The increase produced by the three different compounds was similar. Even though the addition of alkaline compounds in amounts sufficient to reduce the titratable acidity 0.01 to 0.03 per cent caused appreciable increases in the ash alkalinity, the increases were not sufficient in most cases to cause the ash alkalinity to appear abnormal when compared with the range of values obtained on samples of unneutralized dry skim milk.

^* Taken from data presented in a thesis submitted to the Graduate Faculty of the University of Minnesota by R. W. Kunkel in partial fulfillment of the requirements for the degree of Master of Science. Scientific Journal Series Paper 2190, Minnesota Agricultural Experiment Station.