EP3594367A1 - Method for tanning a skin of smoked salmon and tanned smoked salmon skin - Google Patents

Abstract

A method (100) for tanning a smoked salmon skin, comprising a step of tanning (160) for a smoked salmon skin comprising: dipping (161) the smoked salmon skin in a solution comprising a phosphonium ion at a content greater than or equal to 4% by weight relative to the weight of the smoked salmon skin, and soaking (162) the smoked salmon skin in a solution comprising a hydrogen peroxide at a content greater than or equal to 0.5% by weight relative to the weight of the smoked salmon skin.

Description

The invention relates to the field of tanning of fish skins, and more particularly of smoked salmon skins. The invention relates to a tanning process which makes it possible to produce, from a smoked salmon skin, a tanned salmon skin having good aesthetic and functional characteristics. The invention also relates to a tanned salmon skin capable of being obtained by such a process.

[Prior art]

A very large variety of animal skins is currently tanned, some of which, such as lizard, fish and crocodile skins, can be considered exotic in the sense that they are not very widespread. In addition, some of these skins have unique characteristics with, for example, tanned salmon skin which is characterized by typical ornamental patterns which cannot be obtained artificially or from other animals.

The skins of fresh animals, which mainly contain proteins, are subject to decomposition, in particular by microorganisms. The tanning of animal hides aims to increase the mechanical, chemical and biological stability of tanned hides compared to fresh hides. For this, the tanning processes generally include a main tanning step which is combined with various preparation and finishing steps which can improve the quality of the leather.

For so-called exotic skins, their rarity is generally due to the difficulties linked to obtaining raw materials. In addition, these skins are generally derived from animals essentially reared or captured for their skin, which can generate discomfort among users or potential users, who are not in favor of these sacrifices dictated by well-being and not necessity.

Smoked salmon is the most commonly produced by-product from Atlantic salmon. The European smoked salmon market was estimated at 323,100 tonnes in 2016. The smoked salmon skin, along with the head and central rib, is one of the main smoked salmon waste. Thus, it would constitute a raw material of choice for the manufacture of tanned salmon skin because the salmon was not killed initially for its skin but for its flesh.

However, there is no method of tanning the skin of smoked salmon and tanned salmon skins today come from fresh skins or preserved in the wet state ( EP0285738 ; EP0575632 ; EP1045039 ). Indeed, the smoked salmon skin underwent a stage having consequences on its composition and its physico-chemical properties causing difficulties during its tanning. In addition, the known methods of tanning fish hides generally use heavy metals or chromium ( Zengin, A., Basaran, B., Karavana, H., Mutlu, M., Bitlisli, B., Gaidau, C., Niculescu, M., Maereanu, M .. (2015). XXXIII IULTCS Congress, At Novo Hamburgo / Brazil. Fish Skins: Valuable Resources for Leather Industry .). However, chromium is a toxic and difficult to recycle compound which is no longer desirable to use for the manufacture of consumer goods.

Consequently, there is a need for new methods for tanning efficient and environmentally friendly smoked salmon skin as well as for tanned smoked salmon skin as such which can be used in leather goods.

[Technical problem]

The invention therefore aims to remedy the drawbacks of the prior art. In particular, the object of the invention is to propose a tanning process specially adapted for tanning a smoked salmon skin, said process being moreover environmentally friendly.

The invention further aims to provide a tanned smoked salmon skin, said tanned smoked salmon skin being able to be very resistant mechanically, having a quality appearance.

[Brief description of the invention]

• le trempage de la peau de saumon fumée dans une solution, de préférence aqueuse, comprenant un ion phosphonium à une teneur supérieure ou égale à 4 % en poids par rapport au poids de la peau de saumon fumée, et
• le trempage de la peau de saumon fumée dans une solution, de préférence aqueuse, comprenant un peroxyde d'hydrogène à une teneur supérieure ou égale à 0,5 % en poids par rapport au poids de la peau de saumon fumée.

To this end, the invention relates to a method for tanning a smoked salmon skin, according to which a step of tanning said skin comprises:

• soaking the smoked salmon skin in a solution, preferably an aqueous solution, comprising a phosphonium ion at a content greater than or equal to 4% by weight relative to the weight of the smoked salmon skin, and
• soaking the smoked salmon skin in a solution, preferably aqueous, comprising a hydrogen peroxide at a content greater than or equal to 0.5% by weight relative to the weight of the smoked salmon skin.

Such a tanning process makes it possible, from a smoked salmon skin, to make a leather with mechanical and chemical properties desired by the consumer and this without the use of chromium harmful to man and the environment. While the conventional tanning methods do not work on smoked skin, the method according to the invention makes it possible to obtain quality leather despite the prior transformations which have been suffered by the skin during smoking.

According to other optional characteristics of the process:

• It comprises, prior to the tanning step, a first cleaning step, said cleaning step comprising soaking the smoked salmon skins in an aqueous solution comprising at least one disinfectant and at least one detergent, the aqueous solution preferably being at a temperature between 10 and 20 ° C.
• It comprises, prior to the tanning step, a preparation of the skin including a liming step of the smoked salmon skin in an aqueous solution comprising sodium sulfide at a content of at least 1% by weight relative to the weight of smoked salmon skin and calcium hydroxide at a content of at least 1% by weight relative to the weight of smoked salmon skin. This combination, used in the skin preparation step prior to the tanning step, helps the skin to relax.
• the aqueous solution used during the liming stage comprises sodium hydrogen sulfide. This compound allows the elimination of impurities still present on the skins and improves the effect of liming.
• it comprises a step of deliming smoked salmon skins, said deliming step comprising the use of strong acids having a pKa of less than or equal to -4 and / or weak acids having a pKa of between -2 and 5.
• it comprises a step of softening the smoked salmon skins, the said step of softening comprising soaking the smoked salmon skins in an aqueous solution comprising a protease.
• the method comprises, prior to the tanning step, a preparation of the skin including a pickling step in an aqueous solution comprising an organic acid and sodium chloride. This lowers the pH of the smoked salmon skin and prepares it for the tannins.
• the pickling step includes soaking carried out with stirring in an aqueous solution supplemented with sodium chloride until a density of Baumé degree greater than 10. This density allows better preparation of the skin for tanning.
• the pickling stage involves adding sodium chlorite and then sodium thiosulfate to the aqueous solution. The addition of this competition combination to improve the performance of the pickling stage.
• the method comprises, after the tanning step, a step of retanning the smoked salmon skin carried out using a tanning agent of plant origin. This step improves the product while maintaining great respect for the environment.
• It comprises a step of fattening tanned smoked salmon skins, said step of fattening comprising soaking the tanned smoked salmon skins in an aqueous solution comprising one or more fats.
• the process is carried out on a smoked salmon skin having a heavy metal concentration of less than or equal to 1 ppm. Thus, this reduces the risk of intoxication, allergy, neurological degeneration and other pathologies linked to heavy metals, both for operators and for users.

The invention further relates to a tanned smoked salmon skin capable of being obtained by a tanning process according to the invention having a chromium concentration of less than or equal to 10,000 ppm. The invention is therefore more respectful of the environment and of human health. Indeed, a low concentration of Chromium eliminates the problems associated with ingestion, inhalation, absorption and contact with the skin. Thus, the invention provides better security for operators and consumers by reducing the health risks associated with Chrome. In addition, since chromium is a pollutant in soils and waters, reducing its use is therefore beneficial for the environment, in particular limiting the impact of Chrome on the environment. In addition, preferably, a tanned smoked salmon skin according to the invention has a thickness of between 0.4 and 5 mm.

The invention further relates to an article comprising a tanned smoked salmon skin according to the invention. Such an article is respectful of the environment and human health while having good physical, mechanical and chemical qualities.

• Figure 1, un schéma du procédé de tannage d'une peau de saumon fumée selon l'invention,
• Figures 2A et 2B, photographies de peaux de saumon fumées tannées obtenues selon le procédé selon l'invention.

Other advantages and characteristics of the invention will appear on reading the following description given by way of illustrative and nonlimiting example, with reference to the appended figures which represent:

• Figure 1 , a diagram of the tanning process for a smoked salmon skin according to the invention,
• Figures 2A and 2B , photographs of tanned smoked salmon skins obtained according to the process according to the invention.

[Description of the inventionl

In the following description, the term “tanning process” means a process consisting in transforming skins into leather by making them more durable and more flexible. A "tanning step" according to the invention is a step of a tanning process aimed at reinforcing the collagen fibers.

“Smoking” is understood to mean, within the meaning of the invention, a process by which a salmon, preferably whole and not flaked, is subjected to a product of combustion of certain plants. Preferably, smoking corresponds to the action of fumes which are released during the combustion of certain plants. However, it can also include bringing a salmon into contact with a preparation comprising a product of combustion of certain plants. Smoking generally leads to hardening of the salmon skin. The smoked salmon skin according to the invention is therefore a skin which has undergone a smoking step. A tanned smoked salmon skin is therefore a leather made from a smoked salmon skin.

“Heavy metals” is understood to mean, within the meaning of the invention, natural metallic elements whose density is greater than 5 g / cm ³ . Preferably, the heavy metals within the meaning of the invention are Mercury, Lead, Chromium and Cadmium.

“Polycyclic Aromatic Hydrocarbon” (PAH) within the meaning of the invention means aromatic hydrocarbons, the structure of which comprises at least two condensed aromatic rings. Preferably, the Polycyclic Aromatic Hydrocarbons within the meaning of the invention are selected from: Benzo (a) anthracene, Benzo (b) fluoranthene, Benzo (k) fluoranthene, Benzo (a) pyrene, Inden (1,2,3- cd) pyrene, Dibenzo (a, h) anthracene, Benzo (g, h, i) perylene, Benzo (e) pyrene and Chrysene.

For the purposes of the invention, the term “soaking” means the action of soaking with, of immersing in or of soaking in a solution, the skins of smoked salmon. The soaking can be carried out manually or automatically, for example by means of rotary drums, perforated or not.

For the purposes of the invention, the term “fats” means animal, vegetable, mineral or synthetic oils or fats in the form of a fatty substance which is in the liquid state at ambient temperature and which does not mix not in the water.

By “substantially” within the meaning of the invention is meant a value varying by less than 30% relative to the compared value, preferably by less than 20%, even more preferably by less than 10%.

For the purposes of the invention, the term “aqueous solution” means a solution of which the majority constituent is water and for example a solution of which the solvent is water. An aqueous solution within the meaning of the invention may be in the form of an emulsion or a microemulsion.

In the following description, the same references are used to designate the same elements.

Most production methods for salmon skin leather are based on fresh salmon skins and involve the use of chromium. However, the presence of Chromium, in particular Chromium VI, or other heavy metals potentially exposes users to health risks with for example the development of allergies or dermatoses. In addition, the sources of fresh salmon skins are dispersed and produce relatively small and very heterogeneous volumes. Smoked salmon is a secondary product, the skin of which is considered as waste and which represented on the European market around 320,000 tonnes in 2016, i.e. almost 35,000 tonnes of smoked salmon skins. The development of these relatively homogeneous smoked salmon skins would generate substantial income for the smoked salmon preparation industries.

However, the tanning processes developed for fresh salmon skins do not allow satisfactory results to be obtained on smoked salmon skins. In addition, these conventional tanning methods use high concentrations of chromium which it is desirable not to use. Thus, the inventor has developed a new method of tanning the skin of salmon specially adapted to salmon having undergone a smoking step.

Thus, according to a first aspect, the invention relates to a method for tanning a smoked salmon skin.

• Etapes de préparation de la peau de saumon fumée : nettoyage 110, chaulage 120, déchaulage 130, assouplissement 140 et picklage 150 ;
• Etape de tannage : tannage 160 ; et
• Etapes de finition : retannage 170, engraissement 180.

The tanning of hides generally requires a plurality of steps making it possible to obtain, at the end of the process, a quality product that meets consumers' expectations. The inventor has developed a series of steps for the tanning of smoked salmon skins as presented in the Figure 1 . These steps can be divided into:

• Preparation steps for the smoked salmon skin: cleaning 110, liming 120, deliming 130, softening 140 and pickling 150;
• Tanning step: tanning 160; and
• Finishing steps: retanning 170, fattening 180.

These steps will be described individually in the following description before the description of a particular example of tanning according to the invention.

The salmon skins from which the method according to the invention is implemented are smoked salmon skins. That is to say, they are skins from salmon having undergone a smoking step.

Smoking is preferably bringing the salmon skin into contact with smoke, pre-treated or not, which is released during the combustion of certain plants. Advantageously, the fumes used have a reduced concentration of PAHs and in particular of benzo (a) pyrene. The reduction of this PAH concentration can for example be achieved by the use of liquid fumes whose PAH concentrations and in particular benzo (a) pyrene have been reduced.

In addition, the smoked salmon skins, before being tanned according to the tanning process according to the invention, may have undergone manual or enzymatic flaking, preferably manual.

The process developed is particularly suitable for smoked salmon skins containing little or no heavy metals. Thus, preferably, the smoked salmon skin used in the process according to the invention comprises a concentration less than or equal to 1 ppm of heavy metals, more preferably a concentration less than or equal to 0.1 ppm of heavy metals, and even more preferably a concentration less than or equal to 0.05 ppm of heavy metals.

In addition, the process developed is particularly suitable for smoked salmon skins containing little or no Polycyclic Aromatic Hydrocarbons (PAHs). Thus, preferably, the smoked salmon skin used in the process according to the invention comprises a concentration less than or equal to 10 ppb of PAH, more preferably a concentration less than or equal to 1 ppb of PAH, and of even more preferably a concentration less than or equal to 0.1 ppb of PAH. In particular, the smoked salmon skin used in the process according to the invention has a benzo (a) pyrene concentration of less than or equal to 1 μg / kg, more preferably less than or equal to 0.1 μg / kg, and even more preferably less than or equal to 0.05 μg / kg.

In addition, the process developed is particularly suitable for smoked salmon skins containing little or no dioxins and polychlorinated biphenyls. Thus, preferably, the smoked salmon skin used in the process according to the invention comprises a concentration less than or equal to 75 ppb of polychlorinated biphenyls, more preferably a concentration less than or equal to 50 ppb of polychlorinated biphenyls, and still more more preferred a concentration less than or equal to 20 ppb of polychlorinated biphenyls. In addition, preferably, the smoked salmon skin used in the process according to the invention comprises a concentration less than or equal to 20 pg / g of dioxins, more preferably a concentration less than or equal to 5 pg / g of dioxins , and even more preferably a concentration less than or equal to 1 pg / g of dioxins.

The contents of heavy metals, PAHs, dioxins and polychlorinated biphenyls can preferably be measured according to the recommendations of EC regulation n ° 1881/2006.

In the following description, the contents of compounds are expressed by weight of the tanned salmon skins. Preferably, this corresponds to the weight of the skinned salmon skins except for the cleaning step where it corresponds to the weight of the salmon skins after smoking and cutting. In addition, the method is described here for a salmon skin for reasons of simplification. However, the method according to the invention is preferably used on a plurality of salmon skins as presented in the examples.

Cleaning step for smoked salmon skins

The method according to the invention may include a first cleaning step 110. The aim of this step is in particular to remove dirt, flesh residues and smoking residues from smoked salmon skins.

This cleaning step 110 may include soaking the smoked salmon skins in an aqueous solution comprising at least one disinfectant and at least one detergent. The aqueous solution is preferably at a temperature between 10 and 20 ° C.

The disinfectant can for example be a bactericidal compound. The bactericidal compound is for example selected from: formaldehyde, glutaraldehyde, succinic aldehyde, hypochlorites, quaternary ammoniums, alcohols such as ethanol and isopropanol, and their mixtures. The disinfectant can be used at a content of between 0.1% and 10% by weight relative to the weight of the skin of smoked salmon.

The detergent can be an ionic or nonionic detergent. Preferably, the detergent is a nonionic detergent. The nonionic detergent is for example selected from: glycol esters such as ethylene glycol stearate, glycerol esters such as glycerol stearate, polyoxyethylene glycol esters, sorbitan esters, polyoxyethylene sorbitan esters such as Tween 20®, phenol esters such as newts and Triton-X100®, and mixtures thereof. The detergent can be used at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin.

The soaking step can be carried out with or without stirring. Preferably, it lasts at least an hour and can last up to several days. Preferably, it is longer than the cleaning steps intended for fresh salmon skins. Thus, it advantageously lasts at least 20 hours.

Following this soaking step, the smoked salmon skins can then undergo conventional preparation steps and can be drained, skinned and weighed.

Liming stage of smoked salmon skins

The method according to the invention may include a liming step 120 of smoked salmon skins. The purpose of this step is to destroy fatty bonds and prevent the leather from hardening. This step is preferably carried out after a cleaning step 110.

This liming step 120 may include soaking the smoked salmon skins in an aqueous solution comprising sodium sulfide and calcium hydroxide. The aqueous solution is preferably at a temperature between 10 and 20 ° C.

Preferably, during the liming step 120 of the smoked salmon skin, the content of sodium sulfide in the solution is at least 1%, more preferably at least 2%, by weight relative to the weight of smoked salmon skin and the calcium hydroxide content is at least 1%, more preferably at least 2%, by weight relative to the weight of smoked salmon skin.

For example, sodium sulfide can be used at a content between 1% and 10% by weight of smoked salmon skin and calcium hydroxide can be used at a content between 1% and 10% by weight relative to the weight of the smoked salmon skin.

Advantageously, the aqueous solution used during the liming stage can comprise sodium hydrogen sulfide (NaHS). The sodium hydrogen sulfide can be added at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin, preferably between at a content of between 0.5% and 5% by weight. relative to the weight of the smoked salmon skin.

The liming step can be carried out with or without agitation. Preferably, it lasts at least an hour and can last up to several days.

Deliming step

The method according to the invention may include a deliming step 130 of the smoked salmon skins. The deliming step removes a large part of the lime used in the liming process from the leather. This step is preferably carried out after a liming step 120.

Deliming can use strong acids (e.g. sulfuric acid, hydrochloric acid) having a pKa less than or equal to -4 or weak acids (e.g. formic acid) having a pKa between -2 and 5.

Preferably, this deliming step 130 may include the soaking of limed smoked salmon skins in an aqueous solution comprising an organic acid, and a detergent. The aqueous solution is preferably at a temperature between 10 and 20 ° C.

The organic acid is preferably a carboxylic or dicarboxylic acid. The organic acid is for example selected from: formic acid, acetic acid, propanoic acid, butanoic acid, benzoic acid, oxalic acid, malonic acid, succinic acid and their mixtures. The organic acid can be added at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin.

The detergent can be an ionic or nonionic detergent. Preferably, the detergent is a nonionic detergent. The nonionic detergent is for example selected from: glycol esters such as ethylene glycol stearate, glycerol esters such as glycerol stearate, polyoxyethylene glycol esters, sorbitan esters, polyoxyethylene sorbitan esters such as Tween 20®, phenol esters such as newts and Triton-X100®, and mixtures thereof. The detergent can be added at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin.

The aqueous solution used in the context of the deliming step can also comprise an ammonium salt. The ammonium salt is for example selected from: ammonium sulfate, ammonium chloride, ammonium nitrate, ammonium bicarbonate and mixtures thereof. The ammonium salt can be added at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin, preferably at a content of between 0.5% and 5% by weight. relative to the weight of the smoked salmon skin.

The deliming step can be carried out with or without stirring. Preferably, it lasts at least an hour and can last up to several days. Advantageously, the deliming step can be repeated one or more times.

Easing step

The method according to the invention may include a step of softening 140 the smoked salmon skins. The softening step 140 has in particular the objective of producing a supple leather for example by altering the structure of collagen. For this purpose, proteolytic enzymes can be used. It is carried out before the pickling stage 150 and in the presence of a liming stage 120, it is carried out between the deliming stage 130 and the pickling stage 150.

Thus, this softening step 140 may include soaking the smoked salmon skins in an aqueous solution comprising a protease. The aqueous solution is preferably at a temperature between 25 and 40 ° C.

Protease is an enzyme capable of cutting the peptide bonds of peptides or proteins. The protease used in the softening step can be an endopeptidase or an exopeptidase such as an aminopeptidase or a carboxypeptidase. The protease is for example selected from: serine proteases such as trypsin or chymotrypsin, cysteine proteases, acid proteases such as pepsin, metalloproteases, threonine proteases, glutamic acid proteases, and mixtures thereof . The protease can be added at a content of between 0.001% and 10% by weight relative to the weight of the skin of smoked salmon, preferably at a content of between 0.001% and 5% by weight relative to the weight of the skin of smoked salmon.

The aqueous solution used as part of the softening step may also contain an organic acid. The organic acid is preferably a carboxylic or dicarboxylic acid. The organic acid is for example selected from: formic acid, acetic acid, propanoic acid, butanoic acid, benzoic acid, oxalic acid, malonic acid, succinic acid and their mixtures. The organic acid can be added at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin.

The softening step 140 can be carried out with or without agitation. Preferably, it lasts at least an hour and can last up to several days. Advantageously, the softening step 140 can be repeated one or more times.

Pickling stage

The method according to the invention may include a step of picking 150 of the smoked salmon skins. The purpose of the pickling step 150 is in particular to lower the pH of the smoked salmon skin and to prepare it for receiving the tannins. It is carried out before the tanning step 160 and in the presence of a liming step 120, it is carried out between the deliming step 130 and the tanning step 160.

This pickling step 150 may include soaking the smoked salmon skins, preferably limed, in an aqueous solution comprising sodium chloride. The aqueous solution is preferably at a temperature between 10 and 20 ° C.

Advantageously, the soaking is preferably carried out with stirring until reaching a density in degree of Baumé greater than 10 and preferably until reaching a density in degree of Baumé between 10.5 and 15, preferably at a temperature of 15 ° C. These values are higher than the values observed in the literature and are particularly suitable for the preparation of a smoked salmon skin. The Baumé scale is used to express density and density. It can be obtained via correspondence tables with densimetric degrees.

Once the desired Baumé density is reached, the soaking is followed by a step of acidification of the aqueous solution by the addition of an organic acid until a pH of between 2 and 4 is reached.

Advantageously, the soaking can be followed by the addition of sodium chlorite in the aqueous solution. Sodium chlorite can be added at a content of between 0.1% and 10% by weight relative to the weight of the skin of smoked salmon. In this case, the pickling step can also comprise the addition to the aqueous solution of sodium thiosulfate, preferably at a content sufficient to neutralize the chlorine dioxide formed during the addition of sodium chlorite. Sodium thiosulfate can for example be used at a content of between 0.1% and 5% by weight relative to the weight of the skin of smoked salmon.

The addition of sodium chlorite can advantageously take place before the acidification and the sodium thiosulfate is then added after the acidification.

Alternatively, the pickling step 150 comprises soaking the smoked salmon skins in a solution comprising an organic acid and sodium chloride.

The pickling step 150 can be carried out with or without agitation. Preferably, it lasts at least an hour and can last up to several days. Advantageously, the pickling step 150 can be repeated one or more times.

The Tanning stage

The method according to the invention comprises a tanning step 160 of smoked salmon skins. After the preliminary steps described above, the smoked salmon skin is still putrescible. It must therefore undergo a tanning step 160 proper aimed at stabilizing its structure.

• le trempage 161 d'une peau de saumon fumée dans une solution comprenant un ion phosphonium à une teneur supérieure ou égale à 4 % en poids par rapport au poids de la peau de saumon fumée, et
• le trempage 162 de la peau de saumon fumée dans une solution comprenant un péroxyde d'hydrogène à une teneur supérieure ou égale à 0,5 % en poids par rapport au poids de la peau de saumon fumée.

The tanning step 160 of the smoked salmon skin according to the invention comprises:

• soaking 161 of a smoked salmon skin in a solution comprising a phosphonium ion at a content greater than or equal to 4% by weight relative to the weight of the smoked salmon skin, and
• soaking 162 the smoked salmon skin in a solution comprising hydrogen peroxide at a content greater than or equal to 0.5% by weight relative to the weight of the smoked salmon skin.

This tanning step 160 preferably comprises a first soaking 161 of the smoked salmon skins in an aqueous solution comprising a phosphonium ion and preferably having a pH between 2 and 4. The aqueous solution is preferably at a temperature between 10 and 20 ° C.

A phosphonium ion is a cation of formula PR ₄ ⁺ with R which can be independently selected from a hydrogen or a group composed of 1 to 20 carbons, branched or linear or cyclic, unsaturated or not, for example of the alkyl, aryl, heteroaryl type, cycloalkyl, arylalkyl or alkylaryl and which may contain one or more heteroatoms. The phosphonium ion can for example be selected from: PH ₄ ⁺ , tetraphenylphosphonium, methyltriphenylphosphonium, tetrakis (hydroxymethyl) phosphonium, and mixtures thereof. The phosphonium can obviously be added in the form of a salt such as a chloride, a sulfate or a nitrate. The phosphonium ion can be added at a content of between 0.1% and 15% by weight relative to the weight of the smoked salmon skin, preferably at a content of between 1% and 10% by weight relative to the weight smoked salmon skin.

An organic acid can be added to the aqueous solution of the first soaking during the tanning step. The organic acid, preferably sodium acetate, can be added at a content of between 0.1% and 10% by weight relative to the weight of the smoked salmon skin, preferably at a content of between 0 , 5% and 5% by weight relative to the weight of the smoked salmon skin.

The first soaking 161 can be carried out with or without stirring. Preferably, it lasts at least 30 minutes and can last for several hours.

The tanning step 160 may also include a step of increasing the pH of the aqueous solution to a pH of at least 5. This increase in pH is preferably carried out by the gradual addition of baking soda.

The tanning step 160 further comprises a second soaking 162 of the smoked salmon skin in a solution comprising hydrogen peroxide. This second soaking 162 can be carried out by adding hydrogen peroxide to the aqueous solution of the first soaking 161 or, preferably, include the preparation of a second aqueous solution comprising hydrogen peroxide and the soaking of the smoked salmon skin in this second aqueous solution. In this case, the salmon skin is preferably drained between the two soaking.

The aqueous solution for the second soaking 162 preferably has a pH greater than or equal to 5. The hydrogen peroxide can be added at a content of between 0.01% and 5% by weight relative to the weight of the salmon skin smoked, preferably at a content of between 0.1% and 2% by weight relative to the weight of the smoked salmon skin.

Following this tanning step, the smoked salmon skins can then undergo conventional preparation steps and can in particular be drained and rinsed.

The retanning step

The method according to the invention comprises a retanning step 170 of the smoked salmon skins. Tanned smoked salmon skin can be considered as a semi-finished product whose appearance can greatly benefit from finishing steps. This step is preferably carried out after the tanning step 160.

This retanning step 170 of the smoked salmon skin is carried out using a tanning agent of natural origin, preferably using a tannin of vegetable origin. The retanning step 170 of the smoked salmon skin can be carried out by soaking in an aqueous solution comprising a tanning agent of vegetable origin. The aqueous solution is preferably at a temperature between 15 and 55 ° C.

The tanning agent of plant origin can for example comprise polyphenolic compounds obtained by leaching with water of plant materials such as bark, leaves, fruits or roots. Preferably, the tanning agent of vegetable origin comprises polyphenolic compounds obtained by leaching with bark water. The tanning agent of vegetable origin can be added at a content of between 1% and 20% by weight of smoked salmon skin, preferably at a content of between 2% and 15% by weight of smoked salmon skin.

Advantageously, the retanning step 170 can comprise the addition of dihydroxydiphenyl sulfone to the aqueous solution. This can improve the subsequent conservation of the leather. The dihydroxydiphenyl sulfone can be added at a content of between 1% and 50% by weight relative to the weight of the skin of smoked salmon, preferably at a content comprised between 1% and 40% by weight relative to the weight of the skin. smoked salmon.

Preferably, during this retanning step 170, the aqueous solution comprising the tanning agent of vegetable origin can also comprise one or more synthetic tannins. More preferably, the aqueous solution comprising the tanning agent of vegetable origin can also comprise one or more synthetic tannins, also called replacement syntans, resulting from the polycondensation of molecules selected from: phenols, naphthols, dihydroxydiphenyl sulfone, naphthalenes, sulfonic phenols, benzene sulfonic acids and mixtures thereof.

The retanning step 170 may also include adding at least one elastomeric polymer to the aqueous solution.

Advantageously, the retanning step 170 can also comprise the addition of at least one (meth) acrylic polymer to the aqueous solution. The (meth) acrylic polymer may for example have been formed at least in part from acrylates such as methylacrylate or ethylacrylate and / or methacrylates such as methyl methacrylate. Advantageously, the (meth) acrylic polymer has been formed at least at 50% by weight of acrylates or methacrylates. The (meth) acrylic polymer can be added at a content of between 1% and 15% by weight relative to the weight of the smoked salmon skin, preferably at a content of between 1% and 10% by weight relative to the weight of the smoked salmon skin.

The retanning step 170 can be carried out with or without stirring, preferably with stirring. Preferably, it lasts at least an hour and can last up to several days. Advantageously, the retanning step 170 can be repeated one or more times. Following this retanning step, the smoked salmon skins can be drained and rinsed.

Advantageously, the aqueous solutions used in the context of the process according to the invention, for example during the tanning and retanning steps, have a formaldehyde concentration of less than or also 10,000 ppm, preferably less than or equal to 1,000 ppm and even more preferably less than or equal to 500 ppm.

Likewise, the aqueous solutions used in the context of the process according to the invention, for example during the tanning and retanning steps, have a phenol concentration of less than or also 10,000 ppm, preferably less than or equal to 1,000 ppm and of even more preferably less than or equal to 500 ppm.

The fattening stage

The method according to the invention may include a step 180 for fattening tanned smoked salmon skins. The aim of the fattening step 180 is in particular to introduce greases between the fibers of the leather in order to give it good mechanical properties. This step is preferably carried out after the tanning step 160 or the retanning step 170.

The addition of fats, natural or synthetic, during the retanning step 170 and / or subsequently during the fattening step 180 allows the production of salmon leather having a high flexibility and elasticity.

This fattening step 180 may include soaking the tanned smoked salmon skins in an aqueous solution comprising one or more fats. The aqueous solution is preferably at a temperature between 10 and 50 ° C.

The fats can be fats, or oils, natural or synthetic. Natural fats are preferably from animals or plants which can, for example, be selected from: castor oil, linseed oil, coconut oil, palm oil, oil soy, olive oil, beef fat and their mixtures. The fats can be used at a content of between 1% and 20% by weight relative to the weight of the skin of smoked salmon, preferably at a content of between 2% and 15% by weight relative to the weight of the skin of smoked salmon.

The fats can then comprise at least one fatty acid in esterified form. This improves the suppleness of a tanned smoked salmon skin. Advantageously, the fattening step 180 can comprise the addition of at least one fatty acid in esterified form to the aqueous solution. The fatty acid in esterified form can, for example, form a phospholipid, a glyceride or even a sulphonated fatty acid. The fatty acid can be saturated or unsaturated and substituted or unsubstituted. The fatty acid generally has a number of carbon atoms between 4 and 28. The fatty acid in esterified form can be added at a content of between 1% and 15% by weight relative to the weight of the salmon skin smoked, preferably at a content of between 1% and 10% by weight relative to the weight of the smoked salmon skin.

The fats used in the fattening stage can also be fats which have undergone processing to improve their stability and / or their interaction with tanned smoked salmon skin. Thus, the fats can advantageously be fats that have undergone a transformation and correspond to compounds selected from: sulfonated fats, sulfated fats, phosphate fats, phosphonated fats. For example, the fats can correspond to a compound selected from: sulfated olein, sulfonated olein, sulfated lecithin, and mixtures thereof.

Preferably, during this fattening step 180, the aqueous solution comprising one or more fats is in the form of an emulsion, and more preferably a microemulsion.

The fattening step 180 can be carried out with or without stirring, preferably with stirring. Preferably, it lasts at least an hour and can last up to several days. Advantageously, the fattening step 180 can be repeated one or more times. Following this fattening step, the smoked salmon skins can be drained, rinsed and then dried.

Conventionally, the drying process that can be used is vacuum drying. This vacuum drying can be done by positioning the leather between two plates heated, for example at a temperature between 25 ° C and 75 ° C.

This vacuum drying can advantageously be preceded by a calendering step so as to remove a majority of the moisture contained in the tanned smoked salmon skin.

Once dried, the tanned smoked salmon skin also called smoked salmon leather is ready to use.

According to another aspect, the invention relates to a tanned smoked salmon skin capable of being obtained by the method according to the invention.

As illustrated in Figure 2A and 2B , the process was specially adapted to transform a smoked salmon skin into a quality leather and this objective is achieved as will be presented in the examples. The smoked salmon leather according to the invention, or tanned smoked salmon skin, has better characteristics than conventional fish leathers, from the point of view of breaking strength, its elasticity and these chemical properties. The invention then also relates to a tanned smoked salmon skin obtained by the method according to the invention.

Thus, the invention relates to a tanned smoked salmon skin capable of being obtained by the process according to the invention having a chromium concentration less than or equal to 10,000 ppm, preferably less than or equal to 5,000 ppm, so more preferably less than or equal to 1000 ppm and even more preferably less than or equal to 100 ppm. In addition, the method according to the invention makes it possible to obtain a skin of which the amount of Chromium VI is not detectable by conventional methods. Thus, the invention also relates to a tanned smoked salmon skin capable of being obtained by the process according to the invention having a chromium VI concentration of less than or equal to 1 ppm, preferably less than or equal to 100 ppb, and of more preferably less than or equal to 10 ppb. The chromium concentration is preferably measured according to standard NF EN ISO 17072-2 04-2011.

Likewise, the invention relates to a tanned smoked salmon skin capable of being obtained by the process according to the invention, which may have a concentration of heavy metals less than or equal to 20,000 ppm, preferably less than or equal to 10,000 ppm , more preferably less than or equal to 1000 ppm and even more preferably less than or equal to 100 ppm. The concentration of heavy metals is preferably measured according to standard NF EN ISO 17072-2 04-2011.

In addition, preferably, the invention relates to a tanned smoked salmon skin capable of being obtained by the method according to the invention and having a higher resistance to rupture in the direction of the length (direction of the scales) or equal to 10 N / mm ² , preferably greater than or equal to 15 N / mm ² and more preferably greater than or equal to 20 N / mm ² . The breaking strength is preferably measured according to standard NF EN ISO 3376 01-2012.

The invention also relates to a tanned smoked salmon skin capable of being obtained by the method according to the invention and having a breaking strength measured according to standard NF EN ISO 3376 01-2012 in the direction of the width (perpendicular in the sense of scales) greater than or equal to 15 N / mm ² , preferably greater than or equal to 20 N / mm ² and more preferably greater than or equal to 25 N / mm ² .

In addition to its resistance to deformation, the smoked salmon leather according to the invention has great flexibility. Thus, preferably, the invention relates to a tanned smoked salmon skin capable of being obtained by the process according to the invention and having a percentage of elongation at break measured according to standard NF EN ISO 3376 01-2012 lengthwise (direction of scales) greater than or equal to 65%, preferably greater than or equal to 70% and more preferably greater than or equal to 75%.

The smoked salmon leather according to the invention preferably has a thickness that is substantially constant over its entire surface. The thickness is generally between 0.1 and 10 mm, preferably between 0.4 and 5 mm and more preferably it is substantially equal to 0.6 mm. Alternatively, the cut of the smoked salmon skin is done in such a way as to include part of the pulpit of the smoked salmon. The tanning process according to the invention is such that it is less aggressive than other tanning processes and allows the leather to retain a significant thickness. Thus, it is possible to reach thicknesses greater than conventional thicknesses. The thickness of the tanned smoked salmon skin according to the invention is therefore preferably between 1 and 10 mm, preferably between 1.5 and 6 mm and more preferably it is substantially equal to 2 mm. The thickness is preferably measured according to standard EN ISO 2589: 2006.

According to another aspect, the invention relates to an article comprising a tanned smoked salmon skin according to the invention.

The article can for example be selected from a garment, a shoe, or an article of leather goods such as bag, wallet, purse, belt, binding or jewel.

In particular, the article can be selected from: a case for tablets or for a mobile phone, an orthopedic sole, a key ring, a watch strap, a piece of jewelry such as a necklace, a jacket diary, a cover of book, pencil case, leather box, suitcase, wallet, bag, pocket, shoulder strap, shoe, briefcase, for example briefcase type, harness, label, leather strap, a box, a wallet, a strap for the saddlery, a briefcase, a handbag, a piece of furniture or furniture covering, a key case, a card holder, a cover for travel clothes, a jumpsuit, vest, pants, slipper, suit, coat, jacket, hat, belt, leggings, sandal and glove.

Examples

Below is an example of tanned smoked salmon skins.

As shown in Table 1 below, the smoked salmon skins used have a very low concentration of heavy metals and hydrocarbons. Table 1 Measurement in smoked salmon skin Reference value Mercury 0.027 mg / kg <0.5 mg / kg Lead <0.0050 mg / kg <0.3 mg / kg Cadmium <0.0017 mg / kg <0.05 mg / kg Benzo (a) pyrene <0.05 µg / kg <2 µg / kg Benzo (a) anthracene + Benzo (a) fluoranthene + Benzo (a) pyrene + Chrysene <0.10 µg / kg <12 µg / kg Dioxin-like polychlorinated biphenyls (ICES-6) 9 ng / g <75 ng / g Sum of dioxins and polychlorobiphenyls of dioxin type (WHO-PCDD / PCBTEQ) 0.817 pg / g <6.5 pg / g Measurements carried out according to the recommendations of EC regulation n ° 1881/2006 .

100 kg of smoked salmon skins are cleaned in 1000 L of water comprising 4 kg of Triton X100 ® for 20 hours. They are then drained, skinned and weighed.

After a step of rinsing with water, for the liming step, the skins are introduced into 1000 L of water comprising 2 kg of sodium sulfide, 4 kg of calcium hydroxide and 1 kg of sodium hydrogen sulfide.

After 24 h of stirring, the smoked salmon skins are drained and weighed.

The deliming step is carried out in 400 L of water comprising 1 kg of formic acid, 1 kg of acetic acid, and 0.1 kg of Tween 20®. After 24 hours, the salmon skins undergo a softening step following the addition of a solution of trypsin to the aqueous solution for the equivalent of 100 grams of trypsin. After two hours with stirring, the salmon skins are drained.

The pickling step is carried out in 400 L of water at 15 ° C by adding sodium chloride until a Baumé density of 11 is reached, after which 2 kg of sodium chlorite are added to the aqueous solution and then the the whole is stirred for 30 minutes.

Formic acid is then added until a pH of 3 is reached before adding 500 grams of sodium thiosulphate.

After two hours with stirring, the salmon skins are drained.

The tanning step is carried out in 400 L of water at pH 3 by adding 5 kg of tetrakis (hydroxymethyl) phosphonium chloride.

The acid solution is then gradually neutralized by the addition of baking soda.

After two hours with stirring, the salmon skins are drained and then introduced into a solution comprising 500 grams of hydrogen peroxide.

After two hours with stirring, the salmon skins are drained.

The retanning step is carried out in 200 L of water comprising 5 kg of tannins of plant origin such as the DYECO BIO VF solution (Codyeco®), 1 kg of lanolin, 2 kg of esterified animal fats and 2 kg of lauric acid.

After two hours with stirring, the salmon skins are drained. They are then introduced into an aqueous solution at pH 4, then drained and dried.

The physicochemical characteristics of the pieces of smoked salmon leather obtained were then studied and are presented in Table 2 below: Table 2 Amplitude Average Average observed in the state of the art on non-smoked fish skins ¹ chrome tanned Thicknesses (mm) 0.50 - 0.64 0.56 0.5 Breaking strength ² (lengthwise, in N / mm ² ) 10.3 - 22.5 16.25 14,11 Breaking strength (across the width, in N / mm ² ) 24 - 30.3 26.5 nd Elongation at break ² (lengthwise, in%) 70.6 - 105.1 75.1 71.7 Elongation at break (across the width, in%) 41.8 - 49.8 45.7 nd Chromium concentration (ppm) 45 - 47 46 14,400 ¹ Zengin, A., Basaran, B., Karavana, H., Mutlu, M., Bitlisli, B., Gaidau, C., Niculescu, M., Maereanu, M .. (2015). XXXIII IULTCS Congress, At Novo Hamburgo / Brazil. Fish Skins: Valuable Resources for Leather Industry
² Tensile strength and Elongation at break were measured according to standard NF EN ISO 3376 01-2012

From Table 2, it is clear that the tanned smoked salmon skins according to the invention have mechanical characteristics equivalent or superior to conventional fish leathers while having a much lower chromium content.

Thus, the method according to the invention makes it possible to produce quality leather, from available smoked salmon skins. In addition, the process developed uses little or no chromium and is therefore more respectful of the environment and consumers than the processes conventionally used for non-smoked fish skins.

Claims (15)

Method (100) for tanning a smoked salmon skin, according to which a tanning step (160) for said skin comprises: the soaking (161) of the smoked salmon skin in a solution comprising a phosphonium ion at a content greater than or equal to 4% by weight relative to the weight of the smoked salmon skin, and - soaking (162) the smoked salmon skin in a solution comprising hydrogen peroxide at a content greater than or equal to 0.5% by weight relative to the weight of the smoked salmon skin. Method (100) for tanning a smoked salmon skin according to claim 1, characterized in that , prior to the tanning step (160), the method comprises a first cleaning step (110), said cleaning step (110) comprising soaking the smoked salmon skins in an aqueous solution comprising at least one disinfectant and at least one detergent, the aqueous solution preferably being at a temperature between 10 and 20 ° C. Method (100) for tanning a smoked salmon skin according to either of Claims 1 or 2, characterized in that , prior to the tanning step, the method comprises a preparation of the skin, including a liming step (120) smoked salmon skin in an aqueous solution comprising sodium sulfide at a content of at least 1% by weight relative to the weight of smoked salmon skin and calcium hydroxide at a content of '' at least 1% by weight relative to the weight of the smoked salmon skin. Method (100) for tanning a smoked salmon skin according to claim 3, characterized in that the aqueous solution used during the liming stage (120) comprises sodium hydrogen sulfide. Method (100) for tanning a smoked salmon skin according to any one of Claims 1 to 4, characterized in that it comprises a deliming step (130) of the smoked salmon skins, said deliming step (130 ) involving the use of strong acids having a pKa of less than or equal to -4 and / or weak acids having a pKa of between -2 and 5. Method (100) for tanning a smoked salmon skin according to any one of Claims 1 to 5, characterized in that it comprises a softening step (140) of the smoked salmon skins, said softening step (140) comprising soaking the smoked salmon skins in an aqueous solution comprising a protease. Method (100) for tanning a smoked salmon skin according to any one of Claims 1 to 6, characterized in that , prior to the tanning step, the method comprises a preparation of the skin including a pickling step (150) in an aqueous solution comprising an organic acid and sodium chloride. Method (100) for tanning a smoked salmon skin according to claim 7, characterized in that the pickling step (150) comprises a soaking carried out with stirring added with sodium chloride until reaching a density in degrees of Baumé greater than 10. Method (100) for tanning a smoked salmon skin according to one of Claims 7 or 8, characterized in that the pickling step (150) comprises adding sodium chlorite then thiosulfate to the aqueous solution sodium. Method (100) for tanning a smoked salmon skin according to any one of Claims 1 to 9, characterized in that the method comprises, after the tanning step (160), a retanning step (170) of the smoked salmon skin produced using a vegetable-based tanning agent. Method (100) for tanning a smoked salmon skin according to any one of Claims 1 to 10, characterized in that the method comprises a step of fattening (180) tanned smoked salmon skins, said step of fattening (180) comprising soaking the tanned smoked salmon skins in an aqueous solution comprising one or more fats. Method (100) for tanning a smoked salmon skin according to any one of Claims 1 to 11, characterized in that it is carried out on a smoked salmon skin having a heavy metal concentration of less than or equal to 1 ppm . Tanned smoked salmon skin capable of being obtained by a tanning process according to one of Claims 1 to 12, characterized in that it has a chromium concentration of less than or equal to 10,000 ppm. Tanned smoked salmon skin according to claim 13, characterized in that it has a thickness of between 0.4 and 5 mm. Article comprising a tanned smoked salmon skin according to one of claims 13 or 14.

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