A COOLING LIQUID FOR FISH

Abstract: A cooling liquid for fresh fish is characterized by comprising the following components: water; one or more inorganic salts, preferably NaCl; one or more polyhydric alcohols, preferably glycerol, and ascorbic acids. By use of this cooling liquid fish may be cooled down to -1 to -2 DEG C without the fishflesh freezing. The cooling liquid permits considerable increase of the shelf life of fish.

Description: A COOLING LIQUID FOE FISH The present invention relates to a cooling liquid for fresh fish. Fresh fish will keep for a relatively short time; approxi¬ mately 3 to 4 days when stored at 0-4°C. This, obviously, will cause great problems for retail transactions. Fresh fish of excellent quality is a rare and sought-after product. The alternative to fresh fish, frozen fish, does not have the same organoleptic quality as fresh fish. Consistency will especially deteriorate. During a freezing process cells are ruptured and when the fish is thawed thawing water (cellular liquid) will drain off. Attempts were made to develop methods to prolong the shelf life of fresh fish. Examples to be mentioned are immersion in ice-cold brine, storage in a controlled atmosphere (COg), and sterilization by radiation. So far, it may be ascertained that none of these methods are satisfactory. There is, thus, still a demand for a method which may enhance the shelf life of fresh fish. According to the present invention a cooling liquid is provided comprising water, one or more inorganic salts, preferably NaCl, one of more polyhydric alcohols, preferably glycerol, and ascorbic acid. According to a further development of the invention the components are present in the following realtive amounts: Water 87 - 97 by weight Alcohol 2.0 - 9.5 # by weight Salt 0.5 - 1.5 by weight Ascorbic acid 0.5 - 2.0 t by weight According to a further preferred feature of the invention the cooling liquid has the following composition: 95.. by weight of water, 15. by weight of NaCl, 356 by weight of glycerol, and 156 by weight of ascorbic acid. The cooling liquid according to the invention permits cooling down to -1 to -2°C without causing the fishflesh to freeze. For use of the cooling liquid the fish is etither immersed in, og sprayed with, the liquid. After this treatment the fish will be enveloped in a layer of the liquid which will prevent dehydration and freezing out of water during storage at -1 to -2°C. The additional cooling premitted by use of the cooling liquid according to the invention will prevent autolysis and growth of bacteria. The added ascorbic acid will prevent fat from turning rancid and will, thus, also assist to reduce perishability. Another observation was that fish sprayed with the cooling liquid according to the invention maintained its natural color, whereas fish stored in packed ice tended to turn much more light and pale in color. Temperature being below 0°C when the cooling liquid according to the invention is used, the ice will not melt, but the fish is still surrounded by an atmosfhere saturated with water. I should, thus, be possible to transport less ice per unit weight of fish. Reduced transport costs may, thus, be achived epesielly in case of air freight. The invention is disclosed in more detail below with reference to experiments that were carried out, and Figures of drawing which are described in connection with said expreriments. EXPERIMENT 1 In this experiment an attempt was made to prolong the shelf life by spraying with coolant and super cooling. The coolant prevented ice formation, dehydration, and rancidity and super cooling prevented autolysis and growth of bacteria. In super cooling the temperature in the fish is reduced to below zero degrees Centigrade without the fish freezing. - Cod and salmon were professionally gutted and rinsed, and placed in a polystyrene box with ice in the bottom and on top. The polystyrene box was placed in a carton having a nappy on its bottom. One box was stored at approximately 10°C; the fish sat in melting ice. The other box was placed in a super cooler. The fish was kept in the same packaging as in case of air freight of salmon and trout. The following analyses/observations were made: * Total of volatile nitrogen * Trimethylamin nitrogen (only cod) * Total number of live bacteria * Coliform bacteria * Temperature in the fish * Organoleptic evaluation. The fish stored at 0°C maintained a satisfactory quality for 5 days. The fish kept in the super cooler showed a satisfactotry quality after 12 days. By super cooling the fish maintained a satisfactory quality for 12 days, it could not be distinguished from fresh fish. The chemical and bacteriological analyses confirmed this observation. Another observation mad was that the fish sprayed with coolant kept its natural coloring, wheras fish packed in ice turned substantially more light/pale in color. EXPERIMENT 2 It was an object of this experiment to determine the storage period of fresh cod with super cooling (storage at —1.5*C). For reference was used cod stored in melting ice (storage at 0 β C). Three cods were sprayed with coolant and placed in ice in a super cooler and three cods were stored in melting ice. The fishes had been caught on 12.02.1987, and the experiment started on 13.02.1987. The fishes were gutted and rinsed in a professional manner and had a temperature of +10°C when the experiment started. Standard methods of the Directorate of Fisheries were used to determine "total volatile nitrogen" (TVB-N), trimethylamin nitrogen (TMA-N), total bacteria, coliform bacteria, and organoleptic quality. Figures A and B show the development of trimethylamin nitrogen, and the development of bacteria, respectively at 0°C and at -1.5°C (curves 2 and 3). Both formations of TMA-N and growth of bacteria are inhibited by super cooling. Curved 1 shows the development of quality of fish that was placed in a box with ice, but without topping up ice. When the ice has thawed down the fish is ruined in the course of few hours. The temperature in the rq m where the fish was stored was approximately 10°C. Coliform bacteria were not demonstrated in any of the samples during the experiment. The organoleptic evaluation showed that cod that had been stored for a week had a satisfactory quality. This was the case both for fish that was stored at 0°C, and supercooled fish. After 2 weeks fish that had been stored at 0°C was given the description acceptable (slight deviation in smell and taste), whereas fish that was stored at —1.5°C was described as satisfactory in the organoleptic evaluation. None of the samples fulfilled the demands for content of TMA-N. TMA-N should be less than 3 mg/100 g for fresh fish products. Fish stored at 0°C showed a higher content of bacteria (380000 bacteria/g) than fish stored at -1.5'C (37000 bacteria/g) after 14 days of storing. Fish at 0*C, had an acceptable bacteriological quality (the highest permitted value being 1 mill, bacteria/g), whereas fish at -1.5°C had good bacetiological quality. The conclusion is that cod stored at —1.5"C keeps a satisfac¬ tory quality for 11-12 days, whereas fish stored at 0°C has a satisfactory quality for 8-9 days. By supercooling of cod the keeping quality is prolonged by 2-3 days, also, supercooling is labour saving and weight saving, since less ice may be used and topping up ice is not necessary. Also, the problem of thawing water is avoided.

Claims: P a t e n t C l a i s. 1. A method for preservation of fresh fish, c h a r a c t e r¬ i z e d i that the fish is immersed in, or sprayed with a cooling liquid comprising 92-97% " by weight of water, 2-5$ by weight of one or more inorganic salts, preferably NaCl; 0.1-1.5 by weight of one or more polyhydric alcohols, preferably glycerol, and 0.5-1-5$ by weight of ascorbic acid to precipitate a layer of the liquid on the fish, and that the fish is then cooled down to, and stored at, a temperature of -1 to -2 β C. 2. A method as defined in claim 1, c h a r a c t e r i z e d i n that a " cooling liquid is used with the following composition: 95$ by weight of water, 1$ by weight of NaCl, 3$ by weight of glycerol, and 1$ by weight of ascorbic acid.

Inventors: HARAM EINAR, HARAM, EINAR
Applicants: HARAM EINAR, HARAM, EINAR
Application year: 1988
Main classification: A23B4
IPC codes: A23B4