期刊
JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY
卷 54, 期 17, 页码 6226-6235出版社
AMER CHEMICAL SOC
DOI: 10.1021/jf060934s
关键词
acid urease; composite design; enzyme processing costs; ethanol; lactic and malic acids; model wine solutions; pH; metabisulfite; pseudo-first-order kinetic constant rate; specific activity; urea degradation kinetics
The specific activity (pi(A)) of a whole cell acid urease preparation was assessed in model wine solutions at different levels of malic (M) and lactic acids, metabisulfite, ethanol, and pH by performing a central composite design. M and then pH were found to be the most controlling variables, their effects being practically coincident but of opposite sign. For urea concentrations up to approximate to 1 mol m(-3) the ammonium formation rate was assumed of the pseudo-first-order with respect to urea, this being confirmed by two independent validation tests performed at 20 degrees C for as long as 24 h. In the case of real wines the effective pseudo-first-order kinetic rate constants were found to be smaller than those pertaining to the model solutions having the same wine composition and pH by a factor varying from 10 to 1000, this affecting significantly the specific urease treatment costs per liter of wine treated.
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