EP3594367B1 - Method for tanning a skin of smoked salmon and tanned smoked salmon skin - Google Patents

Description

The invention relates to the field of tanning fish skins, and more particularly smoked salmon skins. Disclosed is a tanning process for producing, from smoked salmon skin, a tanned salmon skin having good aesthetic and functional characteristics. The invention also relates to a tanned salmon skin obtainable by such a process.

[Prior art]

A very wide variety of animal skins is tanned at the present time, some of which, for example the skins of lizards, fish and crocodiles, can be considered as exotic in the sense that they are not widely used. In addition, some of these skins exhibit unique characteristics with for example the tanned salmon skin which is characterized by typical ornamental patterns which cannot be obtained artificially or from other animals.

Fresh animal skins, which mainly contain proteins, are subject to decomposition, especially 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, tanning processes generally have 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 associated with obtaining the raw materials. In addition, these skins are generally derived from animals which are essentially bred or captured for their skin, which can cause discomfort among users or potential users, who are not favorable to these sacrifices dictated by well-being and not necessity.

Smoked salmon is the most common by-product generated from Atlantic salmon. Thus, the European market for smoked salmon was estimated at 323,100 tonnes in 2016. The skin of smoked salmon is, with the head and central ridge, 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 initially killed for its skin but for its flesh.

However, there is no method of tanning smoked salmon skin and today tanned salmon skins are obtained from fresh skins or stored in a moist state ( EP0285738 ; EP0575632 ; EP1045039 ). In fact, the smoked salmon skin has undergone a step having consequences on its composition and its physicochemical properties leading to difficulties during its tanning. In addition, the known methods of tanning fish skins 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 compound which is difficult to recycle and which it is no longer desirable to use for the manufacture of consumer goods.

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

[Technical problem]

The aim of the invention is therefore to remedy the drawbacks of the prior art. In particular, the object of the invention is to propose a tanning process specially adapted to the tanning of a smoked salmon skin, said process also being respectful of the environment.

The invention further aims to provide a tanned smoked salmon skin, said tanned smoked salmon skin being able to be very mechanically strong, 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 process for tanning a skin of smoked salmon according to which a step of tanning said skin comprises:

• soaking the smoked salmon skin in a solution, preferably aqueous, 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 produce a leather with the mechanical and chemical properties desired by the consumer and that without the use of chromium which is harmful to humans and the environment. While conventional tanning methods do not work on smoked hide, the process according to the invention makes it possible to obtain quality leather despite the prior transformations which have been undergone by the hide 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 a temperature between 10 and 20 ° C.
• It comprises, prior to the tanning step, a preparation of the skin including a step of liming the skin of smoked salmon in an aqueous solution comprising sodium sulphide in a content of at least 1% by weight relative to the weight of the skin of smoked salmon and calcium hydroxide at a content of at least 1% by weight relative to the weight of the skin of smoked salmon. This combination, used in the step of preparing the skin prior to the tanning step, helps the skin to relax.
• the aqueous solution used during the liming step comprises sodium hydrogen sulfide. This compound allows the elimination of impurities still present on the skin and improves the effect of liming.
• it comprises a step of deliming the smoked salmon skins, said deliming step comprising the use of strong acids having a pKa 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, said softening step comprising soaking the smoked salmon skins in an aqueous solution comprising a protease.
• the process comprises, prior to the tanning step, a preparation of the skin including a step of pickling in an aqueous solution comprising an organic acid and sodium chloride. This lowers the pH of the smoked salmon skin and prepares it to receive the tannins.
• the pickling step comprises soaking carried out with stirring in an aqueous solution to which sodium chloride has been added until a density in Baumé degree greater than 10 is reached. Such a density allows better preparation of the skin for tanning.
• the pickling step comprises the addition to the aqueous solution of sodium chlorite then of sodium thiosulphate. The addition of this combination helps improve the performance of the pickling step.
• the process comprises, after the tanning step, a step of retanning the smoked salmon skin carried out using a tanning agent of vegetable origin. This step allows improvement of the product while maintaining great respect for the environment.
• It comprises a step of fattening the tanned smoked salmon skins, said fattening step 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 obtainable 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 human health. Indeed, a low concentration of chromium makes it possible to overcome the problems associated with ingestion, inhalation, absorption and contact with the skin. Thus, the invention offers better safety for operators and consumers by reducing the health risks associated with Chromium. In addition, since Chromium is a soil and water pollutant, reducing its use is therefore beneficial for the environment, by limiting the impact of Chrome on the environment. In addition, preferably, a skin of smoked salmon tanned 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 respects 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 become apparent on reading the following description given by way of illustrative and non-limiting example, with reference to the appended figures which represent:

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

[Description of the invention

In the remainder of the description, the term “tanning process” is understood to mean a process consisting in transforming hides 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 strengthening the collagen fibers.

For the purposes of the invention, the term “smoking” is understood to mean a process by which a salmon, preferably whole and not scaled, is subjected to a combustion product 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 salmon skin that has been smoked.

For the purposes of the invention, the term “heavy metals” is understood to mean 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.

For the purposes of the invention, the term “Polycyclic Aromatic Hydrocarbon” (PAH) is understood to mean 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 imbibing 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 rotating drums, perforated or not.

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

For the purposes of the invention, the term “substantially” is understood to mean a value varying by less than 30% relative to the compared value, preferably less than 20%, even more preferably less than 10%.

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

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

Most of the methods of producing 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 skin diseases. In addition, the sources of fresh salmon skins are dispersed and produce relatively small and very heterogeneous volumes. Smoked salmon is a secondary product whose skin is considered as waste and which represents on the European market around 320,000 tonnes in 2016, or nearly 35,000 tonnes of smoked salmon skins. The valuation 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 make it possible to obtain satisfactory results on smoked salmon skins. In addition, these conventional tanning processes use high concentrations of chromium which it is desirable not to use. Thus, the inventor has developed a new method of tanning salmon skin specially adapted to salmon having undergone a smoking step.

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

• 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 skins generally requires a plurality of steps making it possible to obtain, at the end of the process, a quality product that meets consumer 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:

• Steps in preparing 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 remainder of the 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 that they are skins obtained from salmon which have undergone a smoking step.

The smoking is preferably bringing the salmon skin into contact with fumes, pretreated or not, which are released during the combustion of certain plants. Advantageously, the fumes used have a reduced concentration of PAH and in particular of benzo (a) pyrene. The reduction of this PAH concentration can, for example, be achieved by using liquid fumes in which the PAH concentrations and in particular of 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 method according to the invention comprises a concentration of less than or equal to 1 ppm of heavy metals, more preferably a concentration of 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 of less than or equal to 10 ppb of PAH, more preferably a concentration of 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 comprises a benzo (a) pyrene concentration 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 of less than or equal to 75 ppb of polychlorinated biphenyls, more preferably a concentration of less than or equal to 50 ppb of polychlorinated biphenyls, and even more so. more preferably 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 of 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 Regulation EC n ° 1881/2006.

In the remainder of the description, the contents of compounds are expressed by weight of the tanned salmon skin (s). Preferably, this corresponds to the weight of the skinned salmon except for the cleaning step where it corresponds to the weight of the salmon skin after smoking and cutting. Furthermore, the method is described here for a salmon skin for the sake of simplicity. Nevertheless, the method according to the invention is preferably used on a plurality of salmon skins as is presented in the examples.

Cleaning step for smoked salmon skins

The method according to the invention may include a first cleaning step 110. The objective 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 mixtures thereof. 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 a 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 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 agitation. Preferably, it lasts at least one 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 step of smoked salmon skins

The method according to the invention may include a liming step 120 of the smoked salmon skins. The main objective of this step is to destroy the 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 sulphide 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 content of calcium hydroxide is at least 1%, more preferably at least 2%, by weight based on the weight of the smoked salmon skin.

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

Advantageously, the aqueous solution used during the liming stage can comprise sodium hydrogen sulphide (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 skin of smoked salmon.

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

Liming step

The process according to the invention may include a liming step 130 of the smoked salmon skins. The liming 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.

Liming 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 soaking 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 a 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 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 contain an ammonium salt. The ammonium salt is for example selected from: ammonium sulphate, ammonium chloride, ammonium nitrate, ammonium bicarbonate and their mixtures. 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 per relative to the weight of the skin of smoked salmon.

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

Relaxation step

The method according to the invention may include a step 140 for softening the smoked salmon skins. The purpose of the softening step 140 is in particular to produce a supple leather, for example by altering the collagen structure. For this purpose proteolytic enzymes can be used. It is carried out before the pickling step 150 and in the presence of a liming step 120, it is carried out between the liming step 130 and the pickling step 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 smoked salmon skin, 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 in the context of the softening step can 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 one hour and can last up to several days. Advantageously, the softening step 140 can be repeated one or more times.

Pickling step

The method according to the invention may include a step of pickling 150 the smoked salmon skins. The purpose of the pickling step 150 is in particular to lower the pH of the skin of smoked salmon and to prepare it to receive 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, preferably limed, salmon skins 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 a density in Baumé degrees greater than 10 is reached and preferably until a Baumé density in between 10.5 and 15 is reached, 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 makes it possible to express the density and density. It can be obtained via tables of correspondence with the densimetric degrees.

Once the desired Baumé density has been reached, the soaking is followed by a step of acidifying the aqueous solution by adding an organic acid until a pH 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 smoked salmon skin. In this case, the pickling step can also comprise the addition to the aqueous solution of sodium thiosulphate, preferably in a sufficient content to neutralize the chlorine dioxide formed during the addition of sodium chlorite. Sodium thiosulphate 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 be done 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 one hour and can last up to several days. Advantageously, the pickling step 150 can be repeated one or more times.

The Tanning Step

The process according to the invention comprises a step 160 of tanning 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:

• dipping 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 of 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.

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 of between 2 and 4. The aqueous solution is preferably at a temperature of between 10 and 20 ° C.

A phosphonium ion is a cation of formula PR ₄ ⁺ with R which can be independently selected from hydrogen or a group composed of 1 to 20 carbons, branched or linear or cyclic, unsaturated or not, for example of alkyl, aryl, heteroaryl type, cycloalkyl, arylalkyl or alkylaryl and may contain one or more heteroatoms. The phosphonium ion can for example be selected from: PH ₄ ⁺ , tetraphenylphosphonium, methyltriphenylphosphonium, tetrakis (hydroxymethyl) phosphonium, and their mixtures. The phosphonium can of course 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 soak 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 skin of smoked salmon, preferably at a content of between 0 , 5% and 5% by weight based on the weight of the smoked salmon skin.

The first soak 161 can be performed with or without agitation. Preferably, it lasts at least 30 minutes and can last several hours.

The tanning step 160 can also comprise 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 sodium bicarbonate.

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

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 skin of smoked salmon.

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

This step of retanning 170 the skin of smoked salmon is carried out using a tanning agent of natural origin, preferably using a tannin of vegetable origin. The step of retanning 170 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 from 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 preservation 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 smoked salmon skin, preferably at a content of 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 plant origin can also comprise one or more synthetic tannins. More preferably, the aqueous solution comprising the tanning agent of plant 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 can also comprise the addition of 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 methyl acrylate or ethyl acrylate 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 agitation, preferably with agitation. Preferably, it lasts at least one 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 less than or also less than 10,000 ppm, preferably less than or equal to 1,000 ppm and of 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 less than or also less than 10,000 ppm, preferably less than or equal to 1000 ppm and of even more preferably less than or equal to 500 ppm.

The fattening stage

The method according to the invention may comprise a step 180 for fattening the tanned smoked salmon skins. The purpose of the fattening step 180 is in particular to introduce grease 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 exhibiting 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.

Fats can be natural or synthetic fats, or oils. Natural fats are preferably derived from animals or plants which can for example be selected from: castor oil, linseed oil, coconut oil, palm oil, oil soybeans, olive oil, beef fat and mixtures thereof. 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 else a sulfonated fatty acid. The fatty acid can be saturated or unsaturated and substituted or unsubstituted. The fatty acid generally has a number of carbon atoms of 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 skin of smoked salmon.

The fats used in the context of the fattening step can also be fats which have undergone a transformation to improve their stability and / or their interaction with the tanned smoked salmon skin. Thus, the fats can advantageously be fats which have undergone a transformation and correspond to compounds selected from: sulphonated fats, sulphated 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 of a microemulsion.

The fattening step 180 can be carried out with or without agitation, preferably with agitation. Preferably, it lasts at least one 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 heated plates, 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 skin of tanned smoked salmon.

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 process according to the invention.

As shown in figure 2A and 2B , the process has been specially adapted to transform smoked salmon skin into quality leather and this objective has been 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 resistance to breaking, of its elasticity and of these chemical properties. The invention therefore also relates to a tanned smoked salmon skin obtained by the process 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 in which the amount of Chromium VI is not detectable by conventional methods. Thus, the invention also relates to a tanned smoked salmon skin obtainable by the process according to the invention having a Chromium VI concentration 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 heavy metal concentration 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 obtainable by the process according to the invention and having a breaking strength in the direction of the length (direction of the scales) greater 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 tensile 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 tensile 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 exhibiting a percentage of elongation at break measured according to standard NF EN ISO 3376 01-2012. in the direction of the length (direction of the 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 has a thickness that is preferably 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 skin of the smoked salmon is cut in such a way as to include part of the flesh 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 achieve 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 an item of clothing, a shoe, or an article of leather goods such as bag, wallet, purse, belt, binding or jewelry.

In particular, the article can be selected from: a case for tablets or for a cell phone, an orthopedic insole, a key ring, a watch strap, a piece of jewelry such as a necklace, a dust jacket, a cover of book, pencil case, leather cardboard, suitcase, wallet, bag, pouch, shoulder strap, shoe, document holder, for example briefcase type, harness, tag, leather strap, a box, a wallet, a strap intended for saddlery, an attaché case, a handbag, a piece of furniture or furniture covering, a key case, a card holder, a bag for travel clothes, a jumpsuit, vest, pants, slipper, suit, coat, jacket, hat, belt, leg warmer, sandal and glove.

Examples

Below is an example of tanning 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 Measure 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 Dioxins and Dioxin-like Polychlorinated Biphenyls (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 sulphide, 4 kg of calcium hydroxide and 1 kg of sodium hydrogen sulphide.

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

The liming 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 of 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 together 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 of 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 acidic solution is then gradually neutralized by adding baking soda.

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

After two hours of 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 DYECO BIO VF (Codyeco®) solution, 1 kg of lanolin, 2 kg of esterified animal fats and 2 kg of lauric acid.

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

The physico-chemical characteristics of the smoked salmon leather pieces obtained were then studied and are presented in Table 2 below: Table 2 Amplitude Average Average observed in the prior art on non-smoked fish skins ¹ tanned with chromium Thickness (mm) 0.50 - 0.64 0.56 0.5 Tensile strength ² (lengthwise, in N / mm ² ) 10.3 - 22.5 16.25 14.11 Tensile strength (across width, in N / mm ² ) 24 - 30.3 26.5 nd Elongation at break ² (over length, in%) 70.6 - 105.1 75.1 71.7 Elongation at break (across width, in%) 41.8 - 49.8 45.7 nd Chromium concentration (ppm) 45 - 47 46 14400 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 hides while having a much lower chromium content.

Thus, the process 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)

1. A process (100) for tanning a smoked salmon skin wherein a step for tanning (160) said skin comprises:

   - soaking (161) the smoked salmon skin in a solution comprising a phosphonium ion in an amount greater than or equal to 4% by weight based on the weight of the smoked salmon skin, and

   - soaking (162) the smoked salmon skin in a solution comprising hydrogen peroxide in an amount greater than or equal to 0.5% by weight based on the weight of the smoked salmon skin.
2. The process (100) for tanning a smoked salmon skin as claimed in claim 1, characterized in that, prior to the tanning step (160), the process 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 comprised between 10 and 20°C.
3. The process (100) for tanning a smoked salmon skin as claimed in one of claims 1 or 2, characterized in that, prior to the tanning step, the process comprises a preparation of the skin, including a step of liming (120) the smoked salmon skin in an aqueous solution comprising sodium sulfide in an amount of at least 1% by weight based on the weight of the smoked salmon skin and calcium hydroxide in an amount of at least 1% by weight based on the weight of the smoked salmon skin.
4. The process (100) for tanning a smoked salmon skin as claimed in claim 3, characterized in that the aqueous solution used in the liming step (120) comprises sodium hydrogen sulfide.
5. The process (100) for tanning a smoked salmon skin as claimed in any one of claims 1 to 4, characterized in that it comprises a step of deliming (130) the smoked salmon skins, said deliming step (130) comprising the use of strong acids having a pKa less than or equal to -4 and/or weak acids having a pKa comprised between -2 and 5.
6. The process (100) for tanning a smoked salmon skin as claimed in any one of claims 1 to 5, characterized in that it comprises a step of softening (140) the smoked salmon skins, said softening step (140) comprising soaking the smoked salmon skins in an aqueous solution comprising a protease.
7. The process (100) for tanning a smoked salmon skin as claimed in any one of claims 1 to 6, characterized in that, prior to the tanning step, the process comprises a preparation of the skin including a pickling step (150) in an aqueous solution comprising an organic acid and sodium chloride.
8. The process (100) for tanning a smoked salmon skin as claimed in claim 7, characterized in that the pickling step (150) comprises a soaking carried out under stirring to which sodium chloride is added until a density in degrees Baume greater than 10 is reached.
9. The process (100) for tanning a smoked salmon skin as claimed in one of claims 7 or 8, characterized in that the pickling step (150) comprises the addition to the aqueous solution of sodium chlorite then sodium thiosulfate.
10. The process (100) for tanning a smoked salmon skin as claimed in any one of claims 1 to 9, characterized in that the process comprises, after the tanning step (160), a step of retanning (170) the smoked salmon skin carried out using a tanning agent of vegetable origin.
11. The process (100) for tanning a smoked salmon skin as claimed in any one of claims 1 to 10, characterized in that the process comprises a step of fattening (180) the tanned smoked salmon skins, said fattening step (180) comprising soaking the tanned smoked salmon skins in an aqueous solution comprising one or more fats.
12. The process (100) for tanning a smoked salmon skin as claimed in 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.
13. A tanned smoked salmon skin obtainable by a tanning process as claimed in one of claims 1 to 12, characterized in that it has a chromium concentration of less than or equal to 10 000 ppm.
14. The tanned smoked salmon skin as claimed in claim 13, characterized in that it has a thickness comprised between 0.4 and 5 mm.
15. An article comprising a tanned smoked salmon skin as claimed in one of claims 13 or 14.

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