Each value was the mean of 30 determinations.
The metmyoglobin percentage was estimated spectrophotometrically by measuring the reflectance at 525 and 572 nm according to Stewart and others (1965).
The maximum value of the quotient between K/S572 and K/S525 at the beginning of the experiment was fixed as 0% MetMb, while 100% MetMb was obtained after oxidizing a sample in a 1% (w/v) solution of potassium ferricyanide (Ledward 1970).
Each value was the mean of 30 determinations.