Method for processing fish material

The present invention relates to a method for processing fish material including fish bones, into a product with good nutritional properties. The method comprises heat treating fish bones essentially free from fish meat. The fish product is useful as an ingredient in food, feed and other products.

EXAMPLE 1 
 METHOD 150 kg fish raw material consisting of backbones with remains of fish meat from production of salmon filets was added water in ratio 1 part of backbones to 0.8 water (on weight basis). Temperature was adjusted to 55° C. and Bacillus endoprotease preparation (Protamex 1.5 MG™) was added at a dosage of 1 g per kg fish raw material (a dosage of 1 g corresponds to an activity of 1.5 AU). Hydrolysis for 45 minutes at 55° C. was followed by heating to 95° C. for 15 minutes to inactivate the enzymes. The material was sieved to collect the bones which were now free from fish meat. From 150 kg backbone was achieved 18.75 kg clean bones. The remaining 131.25 kg is removed as a liquid containing soluble and partly soluble protein together with the oil. Three batches each of 300 g bone material free from fish meat from the hydrolysis mentioned above were heated in a closed container without adding water (according to the conditions mentioned in Table 1). After the heating the bone samples were dried in an oven at 105° C. for 16 hours. In Table 1 is also shown the water binding capacity of the dried bone. The water binding capacity was measured by weighing off 50 g dried bone, which was pulverized in a blender and gradually adding as much water as the bone powder can absorb. The amount of water absorbed (in % w/w) of dry bone is expressed as the water binding. 1 TABLE 1 Temperature Holding Water Color (° C.) time binding of dried bones 1. Control sample No heating — 76% Brown 2. 100 4 hours 130% Light yellowish 3. 125 30 minutes 121% Light yellowish 
 RESULTS It is clear that by heating the bones in the presence of water (samples 2 and 3) prior to drying the bones achieve improved properties with respect to both water binding and colour compared to the control sample. It was surprising to see the results of the control, which had received some heat treatment during the drying, did not develop as good properties as the other two samples. This shows that heating the bones in a drying process develops much different from heating in the presence of water.