The backbone fraction obtained from industrial processing of Atlantic cod (Gadus morhua) yields about 15% of the whole fish weight. Due to a high content of muscle and bone proteins, it is a valuable raw material for further processing. In the present work minced backbones were subjected to gentle hydrolysis by proteinases to solubilize muscle proteins before the pure bone fraction was heat extracted to recover gelatine and a solid residual fraction containing protein and calcium. Five enzyme preparations were compared: the bacterial enzymes Alcalase, Neutrase and Protamex and preparations of pig and cod trypsins. Best recoveries of protein hydrolysates were obtained with the bacterial enzymes, but these hydrolysates were more bitter than the hydrolysates obtained by tryptic digestion. The gelatine extracted had relatively low molecular weight and may be suitable for technical applications or as a neutraceutical. Apparently the solid residual fraction was mainly collagenous structures containing little calcium. (C) 2002 Elsevier Science Ltd. All rights reserved.