FR2696077A1 - Preventing melanosis in crustaceans - by treatment with soln. contg. glucono-delta-lactone and sulphite - Google Patents

Abstract

Process for preventing development of melanosis in crustaceans comprises immersing the prewashed crustaceans in an aq. soln. contg. a sugar alcohol (sic: glucono-delta-lactone is specified) and a sulphite salt; removing them from the soln.; packaging them without rinsing; and freezing them. USE/ADVANTAGE - The process is esp. applicable to prawns (or shrimps). The treatment prevents formation of black spots during storage without exceeding permitted levels for the chemicals used.

Description

 The present invention relates to a method for preventing the development of melanosis in crustaceans and in particular in shrimps.

 The process makes it possible, thanks to a simple bath containing a suitable mixture, to prevent crustaceans from turning black, which makes them unpalatable to consumers.

This phenomenon is particularly noticeable for shrimp that French consumers like to eat with the head, which is not the case in other countries, such as
United States of America.

 Whatever the market to supply, many techniques can prevent melanosis of crustaceans.

 The best known technique is the use of sodium metabisulphite; nevertheless, this technique has major drawbacks of toxicity for a market like France, where shrimps are eaten with the head, because it is in the cephalothoracic region, small black spots appear and become more intense as and as far as storage in the frozen state, as well as defrosting.

 In conclusion, in order to conserve the original color of the shrimp, much more sodium metabisulphite will be required for head-related shrimp than for shrimp with acephalic effect, which leads to incompatible toxicity in the former with respect to the health services used to treat the shrimp. human consumption.

 Numerous other patents describe mixtures of chemicals which also allow the prevention of melanosis, but none has results likely to compete with the present invention, as to the conservation of the color of shrimp with less toxicity.

 Among these patents, the document FR-A-2,656,771 has a composition that is useful for the preparation of canned seafood products, characterized in that it comprises at least one acidogenic agent, preferably glucolactone or gluconheptonolactone, preferentially derivatives hydrogenated saccharides such as sorbitol, mannitol and xylitol.

 Document FR-A-2,424,707 relates to a process for the dehydration of organic tissues, especially foodstuffs.

 The process is characterized in that the fabric is impregnated with an aqueous solution of carbon dioxide or a progenitor thereof, which is brought to diffuse into the tissue and is dehydrated. the fabric by applying heat and / or reduced pressure to an extent sufficient to release carbon dioxide from the solution into the fabric and thereby inhibit tissue contraction.

The solution may contain, inter alia, 0.1 to 5% gluconates and 0.1 to 5% sodium metabisulfite.

 JP-A-52.125.664 allows cod eggs to be preserved by means of a mixture of glycolic acid and sodium cellulose and glucono-delta-lactone.

 JP-B-79.155.239 relates to a method for preserving the color of seafood by the use of a solid edible acid such as, for example, glucono-delta-lactone.

 Similarly, JP-B-85.108.440 has the same purpose as the previous patent and uses a mixture of sodium-fumaric acid or potassium-bromic acid and maltose and gluconodelta-lactone.

 GB-A-6545 918 relates to a method for preparing boiled intestines, the last step being the addition of a mixture of sodium metabisulphite, benzoic acid and glucono-delta-lactone to allow preservation in the time of preparation.

 FR-A-2,286,606 relates to an additive to allow the freezing of crustaceans without discoloration, with a mixture of 15 to 25% sodium metabisulfite, or potassium, 40 to 60% citric acid or tartaric acid and from 25 to 35% MgCO3.

 There are still many patents on this subject, but none, despite many efforts, does not propose the exact mixture of the present invention, nor the decrease in toxicity that results from the use of this mixture.

 The present invention proposes to solve this problem of toxicity by means of a method for preventing the development of melanosis in crustaceans, which, once sins, are washed beforehand, characterized by the fact that the crustaceans are immersed in a solution containing a sugar-alcohol agent, a salt of sulfurous acid and water, that the crustaceans are emerge from the solution, that the said crustaceans are packaged without rinsing them, and finally that the crustaceans are frozen .

 Another object of the present invention is to provide a method for preventing the development of melanosis, characterized in that the sugar-alcohol agent is formed by gluconodelta-lactone.

 Yet another object of the present invention is to provide a method of preventing the development of melanosis characterized in that the sulfurous acid salt is formed by sodium metabisulfite.

 Another object of the present invention is to provide a method for preventing the development of melanosis, characterized in that the washing water and / or the solution water is seawater.

 Other objects of the present invention will appear on reading the following description of a preferred embodiment of the method which will make it easy to understand the invention.

 This embodiment is given for information only and not limiting.

 The process of blackening the flesh of crustaceans and especially shrimp is due to a well-known phenomenon, melanosis.

 These are amino acids contained in the protein fraction of the flesh, and more particularly of tyrosine, which generates this process.

 Under the action of proteolytic enzymes, the tyrosine molecules are released from the proteins, then polymerize under the action of another enzyme called phenoloxidase and oxygen to form the melanin molecule.

 In this molecule, the electrons of the alternating single and double bonds are not attached very strongly and they can be displaced by light of any wavelength. As a result, all light is absorbed by melanin and any body that contains it appears black. Melanin molecules attach to protein molecules and accumulate into granules whose color varies from yellow to black through all ranges of browns.

 In shrimp, the regions that are first affected by melanosis are the head, the separation between the body and the cephalothorax. These regions are the most irrigated by the blood that contains an enzyme: tyrosinase. This enzyme, which triggers polymerization, is also found in small carapace glands. It is understandable then that a simple crushing shrimp on each other, leads to real fractures of the shell and bursting of these small glands that release the tyrosinase and accelerate the phenomenon of darkening.

When tyrosine and tyrosinase are in the presence, the colorless tyrosine is transformed into Dopa which is pale in color, the latter being transformed into another pigment, the
Dopaquinone which is yellow then, in melanin and other pigments more and more dark.

<Tb>

<SEP> BLOOD <SEP> AND <SEP> GLANDES <SEP> SEGMENTAL <SEP> FROM
<tb><SEP> THE <SEP> CARAPACE
<tb><SEP> ii <SEP> 1
<tb><SEP> L <SEP> TYROSINE <SEP> ~ I \ II <SEP> DOPA <SEP> it
<tb><SEP> TYROS <SEP> (colorless) <SEP> INE <SEP>(<SEP> (pale)
<tb> II <SEP> rl <SEP> II <SEP> II
<tb><SEP><SEP> Series <SEP> DOPA
<tb><SEP><SEP> Series of <SEP>&verbar;<SEP> DOPA
<tb><SEP> Pigments <SEP> I <SEP> quinone
<tb><SEP> of <SEP> plus <SEP> in <SEP> (yellow)
<tb><SEP> more
<tb><SEP> dark
<tb><SEP> \ <SEP> || <SEP> MELANINE
<tb><SEP> (black-brown)
<Tb>
The enzyme therefore acts as a trigger for the melanosis reaction. Thus, melanin, the substance responsible for blackening, can only be formed if the following conditions are met.
presence of tyrosine on which the enzyme will act,
- presence of tyrosinase: the triggering enzyme and,
- presence of oxygen.

 Other factors also play an important role in this alteration: the temperature of the environment favors blackening, which explains the importance of the cold chain.

Washing is essential because it helps to get rid of mud and surface microorganisms that can accelerate the process of weathering. Metal complexing agents, such as glucono-delta-lactone, can be considered as enzyme inhibitors (tyrosinase) because copper or iron participate directly in the enzymatic activity. On the other hand, by a purely oxidative and not enzymatic route, the oxidation of phenols is better in the presence of copper and iron for alkaline PH.

 The interest of the glucono-delta-lactone then appears clearly.

 On the one hand, the complexation of copper and iron cations cancels the 'vitality' of tyrosinase and the oxidation of tyrosine into colored molecules.

 On the other hand, the acidification of the medium allows a better complexing efficiency of gluconates on copper and iron and a better conservation of crustaceans at a low PH.

 The action of gluconolactone is as follows: gluconolactone - gluconic acid - copper or iron gluconate.

 Metabisulfite, which has an irreversible effect on phenoloxidase, is not, however, a total antimelanic. In combination with glucono-delta-lactone, most of the promelanine factors can be controlled by inhibiting the enzyme, acidifying the medium and removing metal ions. But other precautions can combat the presence of bacteria (washing), temperature (cold chain), speed of execution (oxygen and light).

 Trials in different oceans of the world have been carried out.

Each time, the process has followed a predetermined protocol which is this one
before fishing, a soaking tank for the treatment of crustaceans is prepared by pouring, per 100 liters of seawater, approximately 2.5 kilograms of glucono-delta-lactone (GDL) to within 10 t and approximately two kilograms of sodium metabisulfite (SO2) always within 10 t.

 The solution thus prepared is stirred to mix the water and the two ingredients well. Finally, we cover the soaking tank to avoid any stain.

 Immediately after fishing, the crustaceans are thoroughly washed to remove, too, the soil.

 They are placed in appropriate baskets to allow soaking in the previously manufactured solution for at least three minutes.

 Of course, in this position, the baskets and their loading are agitated to facilitate a deep treatment of crustaceans.

 After soaking, the crustaceans are quickly packaged without rinsing.

 Then, there is freezing and storage at a temperature which may be, for example, at least twenty degrees Celsius.

 For this process to be truly effective, precautions for use are to be applied.

 Thus, it is advisable to change the solution as soon as one hundred and fifty kilograms of crustaceans have been treated by the same one-liter soaking bath.

 The tank must be emptied and rinsed before preparing a new bath.

 All previous operations should be done in a short time after capture, as there will be a preventive action against melanosis only if the solution has been used before contracting the disease.

 Therefore, a number of precautions must be followed.

 The shrimp, as soon as they come out of the water, must be thoroughly cleaned to remove bacteria, mud, etc.

 The seawater used for this cleaning and for the preparation of the bath must be clean and free of soil, which is generally the case on the high seas.

 The immersion time and the recommended doses that have been calculated for maximum effectiveness should also be respected.

 After having processed the shrimp quantity, it is imperative to change the bath in order to maintain an identical concentration of the solution for all the shrimps and to avoid the bacterial over-contamination of the last batches that will be immersed.

 Also, do not immerse too many shrimp at a time, because the shrimps in the middle of the basket would be badly treated.

 The tank must be closed when not in use to limit evaporation losses.

 In general, cleanliness is an effective ally in the fight against melanosis.

 Finally, all these operations must be carried out as quickly as possible so that the shrimp are as short as possible at room temperature, which we have already seen above.

As mentioned above, tests were carried out in several places, the first tests were carried out in Senegal, then more advanced tests were carried out in particular in the Pacific Ocean, in Ecuador (Table I) and in the 'ocean
Atlantic, Guyana (Table 11).

 In these tables, several abbreviations appear to allow to introduce a maximum of data in them.

 Thus "GDL" means glucono-delta-lactone, "SO," ignites sodium metabisulfite, "kg" represents kilograms, "L" translates liters, "ppm" particles per million, "Abs" is the abbreviation for absent, "+" means presence of melanosis, "0" represents the absence of melanosis, "+ / 0" means partial presence of melanosis, finally "Melanosis 15h / To amb" is the simplified translation of presence of melanosis after the shrimp spent fifteen hours at room temperature.

The results are as follows

<tb> Solu- <SEP> Concentrations <SEP> in <SEP> Residual <SEP> levels <SEP> in <SEP> additives
<tb> tion <SEP> additives <SEP> in <SEP><SEP> in <SEP><SEP> flesh <SEP> of <SEP> shrimp
<tb><SEP> solution <SEP> of
<tb><SEP> soaking
<tb><SEP> Glucono- <SEP> Metabi
<tb><SEP> delta- <SEP> sulphite <SEP> Shrimps <SEP> raw <SEP> Shrimps <SEP> cooked
<tb><SEP> lactone <SEP> of
<tb><SEP> sodium
<tb><SEP> Kg / 100L <SEP> Kg / IOL <SEP> GD <SEP> SO2 <SEP> Melanosis <SEP> GDL <SEP> SO2 <SEP> Nose <SEP>
<tb><SEP> L <SEP> - <SEP> 15 <SEP> ppm <SEP> - <SEP> nose
<tb><SEP> pp <SEP> ppm <SEP> h / Toamb <SEP> ppm <SEP> O <SEP> amb
<tb><SEP> m
<tb><SEP> 1 <SEP> 0 <SEP> 0 <SEP> Abs <SEP> Abs <SEP> + <SEP> Abs <SEP> Abs <SEP> +
<tb><SEP> 2 <SEP> 0.5 <SEP> 0 <SEP> Abs <SEP> Abs <SEP> + <SEP> Abs <SEP> Abs <SEP> +
<tb><SEP> 2 <SEP> 1 <SEP> 0 <SEP> 38 <SEP> Abs <SEP> + <SEP> 27 <SEP> Abs <SEP> +
<tb><SEP> 4 <SEP> 1.5 <SEP> 0 <SEP> 69 <SEP> Abs <SEP> + <SEP> 55 <SEP> Abs <SEP> +
<tb><SEP> 5 <SEP> 2 <SEP> 0 <SEP> 91 <SEP> Abs <SEP> + <SEP> 83 <SEP> Abs <SEP> +
<tb><SEP> 6 <SEP> 2.5 <SEP> 0 <SEP> 10 <SEP> Abs <SEP> + <SEP> 41 <SEP> Abs <SEP> +
<tb><SEP> 6 <SEP> 3 <SEP> 0 <SEP> 120 <SEP> Abs <SEP> + <SEP> 109 <SEP> Abs <SEP> +
<tb><SEP> 8 <SEP> 0 <SEP> 0.5 <SEP> Abs <SEP> Abs <SEP> + <SEP> Abs <SEP> Abs <SEP> +
<tb><SEP> 9 <SEP> 0 <SEP> 1 <SEP> Abs <SEP> 10 <SEP> + <SEP> Abs <SEP> 13 <SEP> +
<tb><SEP> 10 <SEP> 0 <SEP> 2 <SEP> Abs <SEP> 6 <SEP> + <SEP> Abs <SEP> 4 <SEP> +
<tb><SEP> 11 <SEP> 0.5 <SEP> 0.5 <SEP> Abs <SEP> 7 <SEP> + <SEP> Abs <SEP> Abs <SEP> +
<tb><SEP> 12 <SEP> 0.5 <SEP> 1 <SEP> Abs <SEP> 14 <SEP> + <SEP> Abs <SEP> 19 <SEP> +
<tb><SEP> 13 <SEP> 0.5 <SEP> 2 <SEP> Abs <SEP> Abs <SEP> + <SEP> Abs <SEP> 7 <SEP> + /
<tb><SEP> 14 <SEP> 1 <SEP> 0.5 <SEP> 31 <SEP> Abs <SEP> + <SEP> 18 <SEP> Abs <SEP> + /
<tb> 15 <SEP> 1 <SEP> 1 <SEP> 14 <SEP> 11 <SEP> + / 0 <SEP> 19 <SEP> 4 <SEP> 0
<tb><SEP> 16 <SEP> 1 <SEP> 2 <SEP> 27 <SEP> 15 <SEP> + <SEP> 30 <SEP> 28 <SEP> 0
<tb><SEP> 17 <SEP> 1.5 <SEP> 0.5 <SEP> 44 <SEP> 9 <SEP> + / 0 <SEP> 50 <SEP> Abs <SEP> 0
<tb><SEP> 18 <SEP> 1.5 <SEP> 1 <SEP> 58 <SEP> Abs <SEP> + / 0 <SEP> 44 <SEP> 11 <SEP> 0
<tb><SEP> 19 <SEP> 1.5 <SEP> 2 <SEP> 75 <SEP> 23 <SEP> 0 <SEP> 39 <SEP> 20 <SEP> 0
<tb><SEP> 20 <SEP> 2 <SEP> 0.5 <SEP> 120 <SEP> Abs <SEP> + / 0 <SEP> 147 <SEP> Abs <SEP> 0
<tb><SEP> 21 <SEP> 2 <SEP> 1 <SEP> 146 <SEP> 23 <SEP> + / 0 <SEP> 201 <SEP> 13 <SEP> 0
<tb><SEP> 22 <SEP> 2 <SEP> 2 <SEP> 309 <SEP> 14 <SEP> 0 <SEP> 120 <SEP> 22 <SEP> 0
<tb><SEP> 23 <SEP> 2.5 <SEP> 0.5 <SEP> 245 <SEP> 4 <SEP> + / 0 <SEP> 207 <SEP> Abs <SEP> 0
<tb><SEP> 24 <SEP> 2.5 <SEP> 1 <SEP> 212 <SEP> 14 <SEP> + / 0 <SEP> 195 <SEP> 7 <SEP> 0
<tb><SEP> 25 <SEP> 2.5 <SEP> 2 <SEP> 122 <SEP> 30 <SEP> 0 <SEP> 221 <SEP> 18 <SEP> 0
<tb><SEP> 26 <SEP> 3 <SEP> 0.5 <SEP> 194 <SEP> 5 <SEP> 0 <SEP> 240 <SEP> Abs <SEP> 0
<tb><SEP> 27 <SEP> 3 <SEP> 1 <SEP> 271 <SEP> 11 <SEP> 0 <SEP> 265 <SEP> 19 <SEP> 0
<tb><SEP> 28 <SEP> 3 <SEP> 2 <SEP> 118 <SEP> 9 <SEP> 0 <SEP> 195 <SEP> 12 <SEP> 0
<Tb>
TABLE I

<tb> Solu <SEP> Concentrations <SEP> in <SEP> Residual <SEP> levels <SEP> in <SEP> additives <SEP> in
<tb> tion <SEP> additives <SEP> in <SEP> the <SEP><SEP> flesh <SEP> of <SEP> shrimp
<tb><SEP> solution <SEP> of
<tb><SEP> soaking
<tb><SEP> Glucono- <SEP> Metabi
<tb><SEP> delta- <SEP> sulphite <SEP> Shrimps <SEP> raw <SEP> Shrimps <SEP> cooked
<tb><SEP> lactone <SEP> of
<tb><SEP> sodium
<tb><SEP> kg / 1001 <SEP> kg / 1001 <SEP> GDL <SE> SO2 <SEP> Melanosis <SEP> GDL <SEP> SO2 <SEP> Melt
<tb><SEP> ppm <SEP> 15 <SEP> ppm <SEP> nose
<tb><SEP> ppm <SEP> h / Toamb <SEP>#<SEP><SEP> ppm <SEP> O <SEP> amb
<tb><SEP> 29 <SEP> 3 <SEP> 0.5 <SEP> 277 <SEP> 16 <SEP> O <SEP> 274 <SEP> 10 <SE> O <SEP>
<tb><SEP> 30 <SEP> 2 <SEP> 1 <SEP> 95 <SEP> 5 <SEP> O <SEP> 86 <SEP> 4 <SEP> 0
<tb><SEP> 31 <SEP> 2 <SEP> 0.5 <SEP> 71 <SEP> 4 <SEP> O <SEP> 63 <SEP> - <SEP> 0
<tb><SEP> 32 <SEP> 1 <SEP> 1 <SEP> 78 <SEP> 7 <SEP> + / 0 <SEP> 99 <SEP> - <SEP>
<tb><SEP> 33 <SEP> 2 <SEP> - <SEP><SEP> 92 <SEP> t <SEP> + <SEP> 25 <SEP> - <SEP>
<Tb>
TABLE II
It is noted that several soaking solutions have been tested.

 Each of them is distinguished from the others by the amount of ingredients that are glucono-delta-lactone and sodium metalbisulfite.

 These tests were conducted on raw and cooked shrimp, which corresponds to the different types of shrimp sales in the trade.

The results obtained lead to the following conclusions
- the use of Glucono-delta-lactone as sole additive does not effectively prevent the development of melanosis.

This solution will not be retained (solutions 2 to 7 and 33)
- the use of metabisulfite as sole additive does not effectively prevent the development of melanosis (solutions 8 to 10)
the combined use of glucono-delta-lactone and metabisulfite allows, for certain concentrations, to effectively prevent the development of melanosis, for a period of at least eighteen months in the frozen state (solutions 19, 22, 25 to 31);
- Moreover, the residual sodium metabisulphite contents are well controlled since the maximum values are of the order of 30 ppm on raw shrimps, 20 ppm on cooked shrimps, which makes it easy to comply with legislation concerning use of these additives, where the maximum permitted levels are 100 and 30 ppm respectively;
the residual glucono-delta-lactone contents do not exceed 310 ppm, which constitutes, for this additive, quite reasonable concentrations;
- it will be noticed that, appreciably, the shrimp of Guiana have a better hold than those of Ecuador. Indeed, in Ecuador, shrimp are stored immediately after fishing, in baskets between two layers of ice and the baskets are themselves stored on each other in refrigerated trucks;
- These shrimps suffer a crash that will promote the development of melanosis. In French Guiana, shrimps caught at sea are stored in boxes in plate freezers and therefore do not undergo this crushing
It should be noted that cooked shrimps develop melanosis much more slowly than raw shrimps. In fact, it is possible to expect a significant inhibition of the enzymatic activity of tyrosinase during cooking.

 It therefore appears that if the soaking solutions are prepared in accordance with the proportions calculated in GDL and SO2, compliance with the legislation is easily achievable.

On the other hand, the results on raw are well below 100 ppm, so there is a margin of safety that would allow, if melanosis was developing before twelve months, to increase the doses of
SO2 to use in order to more effectively contain its development.

 It appears that the soaking time has little effect on the residual contents beyond three minutes.

 It is obvious that the difficult fishing conditions do not allow fishermen to work with a stopwatch.

 It is therefore interesting to know that beyond three minutes, the effectiveness of the solutions used remains intact and that the residual contents are always under control, whatever the soaking time.

 However, in practice, fishermen can not immerse shrimp less than three minutes in the solution because of the working conditions.

 The most interesting solutions are therefore in the vicinity of 2.5 kilograms of glucono-delta-lactone and two kilograms of sodium metabisulphite per hundred liters of water of the solution.

 All this information makes it possible to determine other objects of the invention.

 Thus, the method of preventing the development of melanosis is characterized in that for 100 liters of water of the solution, 1.5 to 3 kilograms of glucono-deltalactone and 0.5 to 2.5 kilograms of metabisulfite are added. sodium.

 As regards the proportions, the amount of gluconodelta-lactone and sodium metabisulfite is always greater than or equal to 3.5 kilograms.

 In the case where the crustaceans are previously cooked, the solution of one to three kilograms of glucono-delta-lactone and 0.5 to 2.5 kilograms of sodium metabisulphite is added to the one hundred liters of water.

 Again, proportions must be respected, in other words, the amount of glucono-delta-lactone and sodium metabisulfite is always greater than or equal to two kilograms.

 The immersion of crustaceans and thus shrimps in the solution is at least three minutes.

 Another object of the present invention is that the amount of crustaceans treated per hundred liters of solution can not exceed one hundred and fifty kilograms.

 Finally, a final object of the present invention is that crustaceans are shrimp.

Claims (11)

 1. A method of preventing the development of melanosis in crustaceans, which, once sins, are previously washed, characterized by the fact  that the crustaceans are immersed in a solution containing a sugar alcohol agent, a sulfurous acid salt and water,  that the crustaceans emerge from the solution,  that the said crustaceans are conditioned without rinsing them and finally,  that the crustaceans are frozen.  2. A method of preventing the development of melanosis, according to claim 1, characterized by the fact  that the sugar-alcohol agent is formed by glucono-deltalactone.  A method of preventing the development of melanosis according to any one of claims 1 or 2, characterized in that  that the sulfurous acid salt is formed by sodium metabisulfite.  4. A method of preventing the development of melanosis, according to any one of claims 1, 2 or 3, characterized by the fact  that the washing water and / or the solution water is seawater.  5. A method of preventing the development of melanosis according to any one of claims 1, 2, 3 or 4, characterized in that  that per 100 liters of water of the solution, 1.5 to three kilograms of glocono-delta-lactone and 0.5 to 2.5 kilograms of sodium metabisulphite are added.  The method of preventing the development of melanosis according to claim 5, characterized by the fact  that the amount of glucono-delta-lactone and sodium metabisulfite is always greater than or equal to 3.5 kilograms.  7. A method of preventing the development of melanosis according to claim 1, characterized in that  that the immersion of crustaceans in the solution is at least three minutes.  8. A method of preventing the development of melanosis according to any one of claims 1, 2, 3, 4, 5, 6 or 7, characterized in that  that the quantity of crustaceans treated per hundred liters of solution may not exceed one hundred and fifty kilograms.  9. A method of preventing the development of melanosis according to any one of claims 1, 2, 3, 4, 7 or 8 characterized by the fact  whereas when the crustaceans are cooked beforehand, one to three kilograms of glucono-delta-lactone and 0.5 to 2.5 kilograms of sodium metabisulphite are added to the 100 liters of water in the solution.  The method of preventing the development of melanosis according to claim 9, characterized by the fact  that the amount of glucono-delta-lactone and sodium metabisulfite is always greater than or equal to two kilograms.  11. A method of preventing the development of melanosis according to any one of claims 1, 2, 3, 4, 5, 6, 7, 8, 9 or 10, characterized in that  that crustaceans are shrimps.