It is thus apparent that some considerable change had taken place in the composition of the material.

A portion of the same original liquor was concentrated under a partial vacuum of 15 in. at 180° Fahr. for three hours and a half, and the composition of the resulting extract calculated to a 20-per-cent.-moisture content shows :—

It is seen that when the liquor is evaporated under vacuum there is some change in the composition of the resulting extract—the proportion of the organic matter decreases, while the mineral salts increase; otherwise the composition of the vacuum-evaporated extract is very nearly that of the original liquor calculated to a 20-per-cent.-moisture content, the acidity, insoluble and coaguable proteids, proteoses, and total meat bases being present in about the same amounts in each case. In the original liquor there were no peptone-like bodies, whereas in the vacuum-concentrated extract there were found 0·31 per cent. of these substances.

The extract concentrated in the open pan is very different in composition from either the original liquor or the vacuum extract: the proportion of the organic matter has decreased, and the mineral salts increased considerably; the total nitrogen remains about the same, but the forms in which the nitrogen is present have undergone considerable change; about three-fifths of the insoluble and coaguable proteids have been rendered soluble and converted to other nitrogenous substances; there is a decrease in the amounts of proteoses and meat bases; while against these decreases there is found 8·69 per cent. of peptone-like bodies which are absent in the original liquor, and present in the vacuum extract to only 0·31 per cent. The acidity has increased by over 2 per cent.

The peptone-like bodies and polypeptides are bitter in taste, and it is found that extracts containing relatively large amounts of these bodies have a decidedly bitter taste. Samples containing 16·58 per cent., 12·02 per cent., 14·65 per cent., and 13·43 per cent. of peptone-like bodies were found to be bitter, while in samples containing 8·44 per cent., 8·60 per cent., 8·69 per cent., and 5·09 per cent. of these bodies no bitter taste could be noticed.

As but very small amounts of peptone-like bodies are present in vacuum-concentrated extract, and but little change in the composition of nitrogenous bodies is found, it is probable that the prolonged action of heat on the nitrogenous material in the presence of the normal flesh acids and salts, the amount of which increase as the evaporation proceeds, is the cause of the marked change in composition found in the open-pan-concentrated extract. The so-called “burned” flavour sometimes found in meat-extracts is doubtless due to the same cause, for in vacuum-concentrated extract no such undesirable flavour is noted.

For permission to publish these results the author desires to express his thanks to the Christchurch Meat Company (Limited), in whose chemical laboratory most of the work in connection with this investigation was carried out.