Process for the preparation of sliced fish products

Abstract: A process for the efficient preparation of a sliced fish product, for example Seelachs slices, having a uniform size and consistent salt content; wherein the slices are obtained from frozen deep-skinned fish fillet blocks.

Description: TECHNICAL FIELD OF THE INVENTION A process for the efficient preparation of a sliced fish product having a uniform size and having a consistently uniform salt content. BACKGROUND TO THE INVENTION AND PRIOR ART Sliced fish products for example "Seelachs slices" are currently manufactured from large (Grade I/II) fish fillets having a weight of greater than 3.0 kg and preferably a weight of greater than 4.5 kg. These fish fillets are salted at 10°C for 3 to 4 weeks until the salt concentration contained in the cell water of the fish is from 22 to 26%. Generally the ratio of salt:fish used is 1:2 (w/w). The fish are then washed and the belly flaps removed before cutting into suitable lengths. These lengths are then sliced, coloured and desalted, smoked, dried and packaged. However, this process has many disadvantages, for example it is becoming increasingly difficult to obtain fish fillets of a suitable size, the salt concentration of the final sliced product may vary largely within each fish slice, and the yield is very poor. It is therefore highly desirable to be able to manufacture a product of a similar or higher quality using a process which does not have these problems. GB 1 387 117 (Unilever Ltd) describes a process for the preparation of slices of fish comprising: (a) contacting the raw fish fillets with salt to provide salted fish fillets containing from 3 to 20% salt expressed on a weight basis; (b) coating the salted fillets with 5 to 50% by weight of a binder comprising finely divided substantially bone-free raw fish muscle mixed with from 1 to 10% salt, and from 3 to 8% food grade phosphate; and (c) moulding the binder-coated fillets to form integral blocks of uniform weight shape and size. We have, however, now surprisingly discovered that it is possible to form blocks of fish fillets which adhere sufficiently well together without the requirement to salt the fillets prior to freezing and also without the requirement to provide a binder. Thus a much simpler process for providing high quality fish slices is disclosed which enables fish fillets having a uniform salt concentration to be produced with minimum waste. The fish fillets may also be sourced from smaller fish than the conventional process. It is essential, however, that the fish fillets are deep-skinned prior to being frozen into the fish block. By deep-skinned is meant that all the brown flesh from underneath the skin is removed. Such a deep-skinning process is essential in order to provide a sliced product which adheres together without the requirement for binder and is of the required high quality. DISCLOSURE OF THE INVENTION Accordingly the invention discloses a process for the preparation of a sliced fish product comprising: (a) freezing fish fillets from the Gadus family into a block of uniform shape wherein the fish fillets are deep-skinned prior to freezing into the block; (b) salting the block such that a salt concentration of from 22 to 26% is obtained within the fish cell water; (c) slicing; and (d) desalting the fish slices to a salt concentration of from 8 to 10%. As mentioned above this process is particularly advantageous for, but not limited to, the production of the product "Seelachs slices". This is a smoked saithe (sea/rock/mock salmon) slice, wherein the sliced fish is coloured and smoked prior to packaging. It is therefore preferred that the process additionally includes a colouring step and/or a smoking step. The desalting and colouring step may occur simultaneously, for example by passing the slices through a large vat of colourant. Preferably a colour concentration within the fish slice of 250 mg/kg is achieved. Preferably a salt concentration of from 8 to 9% is achieved by de-salting, most preferably a salt concentration of approximately 8% is achieved. One clear advantage of this process over the conventional process mentioned above is that the final concentration of salt can be closely determined, and slices having consistently uniform salt concentration can therefore be achieved. A final salt concentration of less than 8% provides the sliced product with a poor shelf life stability, whereas a final salt concentration of greater than 10% is perceived as being too salty in taste by the consumer. In order to obtain a higher quality final product it is preferred to freeze the deep-skinned fish fillets in the same orientation. The salting process is preferably carried out such that the ratio of fish to salt is 1:2. Furthermore, this process can conveniently be conducted at ambient temperature using the frozen deep-skinned fish fillet blocks. The salting process preferably achieves a salt concentration of 26% in the fish cell water. As mentioned above, the fish may be any member of the Gadus family, for example, saithe, cod, haddock, hake, Alaskan pollock, codling, whiting, blue whiting, coal fish, ling cod, blue ling, tusk, burbot. Preferably the fish is saithe. EXAMPLES The invention is illustrated with the following examples: Example 1 Saithe was filleted and deep-skinned to remove all the brown coloured flesh below the skin, prior to freezing the thus prepared fillets into blocks having the dimension 254x482x62.5 mm. The frozen deep-skinned saithe fillet blocks were then placed in salt in the ratio 1:2 (fish block:salt) and stored at ambient temperature for greater than 22 days in order that the salt content of the fish cell water reached 26%. The excess salt was then washed off the fish block and the block cut into smaller blocks having the dimension 63.1x62.5x96.0 mm. The smaller blocks were sliced and then desalted to a salt content of 8% and coloured simultaneously. The desalt/colour solution comprised: 30% sea salt solution 300,000 litres 10% solution vinegar 60,000 litres GIV 88173 colourant 3,000 kg Apple acid 2,250 kg Preservative 9,000 kg Water to 3,000,000 litres The slices were then smoked, dried and packaged. Good quality, uniform sized slices were achieved with uniform salt and colour concentration. Comparative Example A Example 1 was repeated except the saithe was not deep-skinned before being frozen into blocks. Poor quality slices having a uniform size were obtained. The slices fell apart easily and did not have a uniform salt concentration. Comparative Example B Example 1 was repeated except the saithe fillets were not frozen into a block but treated as individual fillets. The fillets were salted for 3 weeks at 10°C. The ratio of fish:salt was 2:1. The fillets were then washed, cut into 9 cm lengths and sliced. The slices were treated as for Example 1. The slices were not of uniform size. The salt concentration varied from 6 to 12% in the final product. A large proportion of the fish fillet was wasted due to the irregular size of the fillet.

Claims: A process for the preparation of a sliced fish product comprising: (a) freezing fish fillets from the Gadus family into a block of uniform shape wherein the fish fillets are deep-skinned prior to freezing into the block; (b) salting the block such that a salt concentration of from 22 to 26% is obtained within the fish cell water; (c) slicing; and (d) desalting the fish slices to a salt concentration of from 8 to 10%. A process according to claim 1 wherein the fish slices are additionally coloured. A process according to claim 1 or 2 wherein the fish slices are additionally smoked. A process according to claim 1 and claim 2 wherein the desalting and colouring steps are conducted simultaneously. A process according to any preceding claim wherein the fish slices are desalted to a salt concentration of from 8 to 9%. A process according to any preceding claim wherein the fish slices are desalted to a salt concentration of approximately 8%. A process according to any preceding claim wherein the deep-skinned fish fillets are frozen such that the fillets are orientated in the same direction. A process according to any preceding claim wherein the ratio of fish to salt used during the salting step (b) is approximately 1:2. A process according to any preceding claim wherein the salting step (b) is conducted at ambient temperature. A process according to any preceding claim wherein the fish is saithe.

Inventors: DE NUZZI LUCIO, DOMANSKI GERD, ROGGE DIETKE, DE NUZZI, LUCIO, DOMANSKI, GERD, ROGGE, DIETKE
Applicants: UNILEVER NV, UNILEVER PLC, UNILEVER N.V.
Application year: 1993
Main classification: A23L1
IPC codes: A23B4, A23L1