チーズの熟成に関する研究

Abstract

The objects of the present studies are to consider changes of various nitrogenous compounds in cheese during ripening. As a result, several points have come to light from the experiments.1) Electrophoresis developed by TISELIUS was used for the analysis of a decreasing phenomenon of the water-insoluble nitrogenous compounds in cheese. The results obtained from the ascending and descending patterns are summdrized as follows: The water-insoluble substances in unripe cheese were chiefly α-, β- and γ-casein that normally occur in milk. The substances, however, changed with the progress of ripening, and it may be proved that they were extensively decomposed to soluble substances. Especially, α-casein was decomposed more rapidly than β-and γ-casein in cheese.2) Under normal conditions during ripening, those caseins were changed into water-soluble substa nces of simpler form which continuously increased throughout ripening. The increase of water-soluble nitrogenous substances, free amino acids and ammonia followed the same trend. Nitrogenous compounds in the form of proteoses and peptones tended to increase and then decrease during ripening. The rate of formation of the substances was more rapid in the early stages of ripening. The percentages of the substances in cheese obtained from the present studies were generally different from those given by other reports, but the trend in changes seemed to be essentially the same.3) The water-soluble substances in cheese increased progressively with the development of ripening. The substances were extracted with water and, prior to an electrophoretic experiment, dialyzed from the solution to separate any electrolyte, ion not present in the buffer solution. The results of experiments on changes in electrophoretic patterns of the solution during ripening are summarized as follows: There were substances of small mobility in unripe cheese, and many peaks were found in the patterns of the cheese which was ripened for 3 months. In the cheese furthermore ripened (for about 5 months) it was impossible to carry out more or less arbitrary separation in order to determine the peaks in the pattern of a given sample of cheese.4) The object of this experiment is to investigate the rate of liberation of free amino acids during ripening. A paper partition chromatography was used to examine free amino acids in cheese over a ripening period of 3 months from the date of manufacturing. Immediately after manufacturing, glutamic acid, leucine, methionine and aspartic acid were found in the cheese. Then 8 and 17 kinds of amino acids were found in the cheese over a ripening period of 15 days and 3 months respectively. Serine, alanine and methionine seem to have disappeared in the middle stage of ripening.