Changes in the content of the amino-acids in spite of the natural aging ofbeer

Results obtained during several years of experimental work proved the break down of a wide scale of amino-acids as well as of other components, in spit e nf the natural ageing of the beer during it's storing. The extent of the changes was dependent on this conditions of storing, mainly on the temperat ure and the time period. The contents of the particular aminoacids was chan ging in different ranges, whereby the contents of phenylalanine histidine a nd tyrosine were dropping most rapidly followed hv isoleucine. leucine and lysine. The drop in the amino-acids was stronger in beers having higher con tent of dissolved oxygen. The kinetics of the change of the amino acids con tent showed an initial hold-up phase (the lag phase) in the breakdown proce ss. These changes have been discussed in connection with the radical reacti ons, in which oxygen and melanin-substances participated.