During fish ripening, biochemical changes occur that give rise to the organoleptic properties characteristic of the product. Enzymes play a key role in this ripening process, although it is not known exactly which enzymes are involved. We investigated the effects of the gutting method (nobbing only, or nobbing and butterflying) and addition of cathepsin C on general proteolytic activity, chymotrypsin activity, pH and organoleptic characteristics during brine ripening of fresh Engraulis encrasicolus. We also monitored these variables during brine ripening of frozen/thawed E. encrasicolus and E. anchoita. Butterflied fish ripened more rapidly than fish prepared by the traditional method (nobbing only). Inclusion of cathepsin C in the brine had a negative effect on texture (very firm, low juiciness) but a positive effect on flavour, which was more intense. Frozen/thawed fish were successfully ripened, giving a final product with fully acceptable organoleptic characteristics. In all batches except the E. anchoita batch both general proteolytic activity and chymotrypsin activity increased rapidly after immersion in brine, then dropped gradually over the ripening period.