| Abstrakt: |
Experiments were made upon 300 gram guinea pigs fed a new basal diet designed to furnish practically optimum amounts of all nutrients except the antiscorbutic vitamine. The latter was furnished exclusively in the form of filtered canned tomato juice. Relative amounts of this vitamin in the treated and untreated portions of this juice were measured by determining the amounts necessary to prevent scurvy or by a quantitative rating of the severity of the scurvy produced. The technique and the probable degree of precision of the results will be discussed in a later paper.In the case of tomato juice of natural acidity, PH4.2, it was found that boiling for one hour destroyed practically 50 per cent., and for four hours practically 70 per cent. of the antiscorbutic vitamine present. The time curve of the destructive process is therefore much flatter than that of a unimolecular reaction. The latter finding applies also to similar heating experiments at 60° and at 80°. In such experiments at 60° to 100°, the temperature coefficients are relatively low (Q10= 1.1 to 1.3).In experiments in which the natural acidity was first neutralized in whole or in part, the juice then boiled for one hour and immediately cooled and reacidified, it was found at PH5.1 to 4.9 (natural acidity less than half neutralized) the destruction during one hour's boiling was increased to 58 per cent. Neutralization of a larger proportion of the natural acidity regularly increased the rate of destruction of the vitamine at 100°. When alkali was added to an initial PHof I I, which fell to about 9 during the hour of heating, the destruction found by feeding of the juice thus treated but immediately cooled and reacidified, was about 65 per cent. |
