Copper

Abstract

Copper, in trace amounts, is an important inorganic catalyst in the normal metabolic activities of yeasts and other microbial organisms. The copper content of typical musts and wines made in the United States ranges from less than 0.1 to 0.30 mg/L. At higher levels, the metal plays an important role in catalyzing the chemical oxidation of wine phenols. In this regard, copper and copper complexes are more active than iron and its complexes. Aside from chemical and biochemical involvements, copper at concentrations exceeding 1 mg/L may be sensorily detectable (Amerine et al. 1972). Furthermore, copper, along with cadmium and mercury, ranks among the most toxic of heavy metals; and at levels exceeding 9 mg/L it becomes a metabolic toxin that inhibits or delays alcoholic fermentation (Suomalainen and Oura 1971). Fortunately, the latter situation is found infrequently in modem-day winery operations.