of substrates including reduced unfolded proteins and thiol containing networks and gels bovine qsox1 catalyzes the oxidation of a test reduced protein e g pancreatic rnase with a catalytic efficiency two fold higher than the egg white qsox1 as shown in table 2 of example 3 below this latter protein has been shown to catalyze the oxidation of a wide range of reduced proteins and peptides hoober et al j biol chem 274 22147 22150 although bovine milk is a preferred source of qsox1 sulfhydryl oxidase activity has also been found in small amounts in human rabbit and rat milk c e isaacs et al pediatric research 18 532 535 1984 as secreted qsox1 is expected to be a general feature of milk the enzyme may also be present in commercially feasible quantities in the milk of other animals such as sheep and goats accordingly the invention described herein is not limited to bovine milk whey is a by product of cheese making and can be readily obtained in large volumes from the dairy industry whey solution can be created by the well known procedures of precipitating casein by acidifying milk or adding rennet chymosin to milk as described for example in cheese chemistry physics and microbiology volume 1 third edition general aspects patrick f fox paul mcsweeney timothy cogan timothy guinee eds academic press 2004 qsox1 can be isolated and purified.