In summary, a comparison of the two types of vinegar (Fig. 4) reveals that the difference in total nitrogen contents persisted in the resulting vinegars. The problem posed by the formation of urea during wine ageing was suppressed by the subsequent acetification process; as a result, the vinegar from the aged wine contained no urea – and that from the young,unaged wine very little.With provision for experimental error, the two types of vinegar had a very similar profile of nitrogen compounds except for ammonium ion, which was absent from the vinegar made from the aged wine and present at a concentration about 1 mM in that from the young (unaged) wine.