WO2007068753A1

WO2007068753A1 - Process for the production of hydrolyzed-protein based products in composition with zinc

Info

Publication number: WO2007068753A1
Application number: PCT/EP2006/069754
Authority: WO
Inventors: Oreste Odelli; Massimo Neresini; Manuela Cinzia Candido
Original assignee: Sicit Chemitech S.P.A.
Priority date: 2005-12-15
Filing date: 2006-12-15
Publication date: 2007-06-21
Also published as: ITRM20050629A1

Abstract

A process for obtaining protein hydrolysates in composition with zinc salts employing, as starting material, a protein organic material, comprising the steps of hydrolysis by action of bases and/or acids and/or enzymes; addition of calcium hydroxide and one or more zinc salts solubilised beforehand in an acid solution, with promotion of the exchange reaction between the amino acids and peptides salified with calcium and the zinc salts at a temperature higher than or equal to 90°C; and treatment with a precipitating agent to eliminate excess calcium, to obtain hydrolyzed-protein based products in composition with zinc having specific peculiarities as catalyst, activator, reducing agent, coagulating or precipitating agent, fungicide, antiseptic, co-formulant of inks, paints, pigments and dyes, and that may advantageously be used by exploiting the availability of this element in a peculiar form thereof, e.g. for detergent compositions.

Description

PROCESS FOR THE PRODUCTION OF HYDROLYZED-PROTEIN BASED PRODUCTS IN COMPOSITION WITH ZINC

DESCRIPTION

The invention refers to a process for the production of protein hydrolysates in composition with zinc, in particular of the type obtainable from by-products of animal origin and/or from waste and/or from leather tanning industry residues obtained before and after the tanning step.

The same products may be obtained from by-products or products of plant origin, like, e.g., soy and gluten, which are characterised by having high protein content, and/or from agroindustrial waste or other by-products or products of animal origin, like, e.g., milk, dairy products, meat, etc.

Hereinafter, by the wording "protein organic material" it will be meant one of the above-mentioned starting products or a mixture thereof. By "zinc" instead it is meant any one form in which this metal is available: pure salt or mixed salts. Zinc-containing inorganic-based compounds are used in several industrial fields, in agriculture and zootechnics. The association with an organic molecule having specific peculiarities makes zinc particularly active for industrial uses and characterised by bioavailability for use in the agricultural and zootechnical field.

Hence, the products deriving from the process subject-matter of this invention are useful where there is a need to have available innovative absorption technologies involving the use of zinc sources in forms not alien to plant or animal physiology, bioavailable in the absorption system and that may avoid toxicity problems due to overdosage.

These products are useful, e.g. in zootechnics, as zinc supplements that are usually added to diets in order to best perform the functions vital to animal organisms, providing a coverage for the requirements of the zinc element with a dosage lower than those commonly used, and avoiding overdosage in the animal diet, reducing any phenomena of interference with other elements.

Inorganic salts, used in food ration in order to contribute the required micronutrients, are added in remarkable amounts, not only because they are absorbed to a lesser extent as not being carried by a biologically active entity, but also because they can easily be made unavailable to absorption by some natural constituents of diets.

Farming tests on Rainbow trout (Oncorhyncus mykiss) carried out using for comparison diets based on inorganic zinc salts and based on zinc salts in composition with protein hydrolisates, highlighted that, besides an improved conversion index, there is higher zinc deposition in carcasses for animals fed with one-third of the amount envisaged in the formula for the inorganic form. This demonstrates not merely the improved absorption at intestinal level of the zinc associated to an organic molecule, but also the option of performing zinc enrichment. This may entail an interesting development for the future if, rather than "integrated", "functional" foods will be preferred, i.e. foods specifically developed to bring benefits in terms of health and disease prevention, and to be assumed in amounts usually provided with the diet. Innovative technologies for the in vitro study of intestinal absorption of metals present in traces at the intestinal level, such as the Ussing Chambers technique, highlighted elevated bioavailability of zinc-based products in composition with protein hydrolysates with respect to zinc salts, carried out with a higher picking-up by the intestinal mucosa.

Experiments conducted on fattening bovines, lactating cows, weaning piglets, demonstrated the potential reduction of up to one- fifth of the requirements recommended for each mineral element, in case of use of metals in composition with protein hydrolysates, productive performances being equal.

Foliar fertilization with inorganic microelements represents a well-established technique for the provision of nutritive elements to plants, and it is more effective when associated to protein hydrolysates and under conditions of nutritional deficiencies.

In general, mineral elements, when associated to natural organic structures, are recognised by plant and animal organisms as being part of their system and therefore readily used without any biochemical reprocessing to make the elements biocompatible.

The zinc dosages employed in case of use of said products deriving from the process subject-matter of this invention are remarkably reduced with respect to traditional zinc compounds, with the consequent lesser release and accumulation in the environment and with a consequent advantage of a lesser environmental impact.

Said products are useful also where there is a need to avail of zinc sources in innovative forms, not necessarily in a zootechnical or agricultural field. E.g., in the detergency field there is remarkable interest for innovative zinc-based products useful in the cleaning of silver, with the feature of inhibiting tarnishing, and in the cleaning of glass surfaces, with the feature of preserving the glass and decorations from corrosion.

Products are known in the state of the art made of mixtures of amino acids and peptides, or also of protein hydrolysates deriving, e.g., from material containing connective tissues deriving from hide processing in a tannery, obtained with hydrolysis processes envisaging the use of lime even at high temperatures and pressures. They are described, e.g., in the exemplary embodiment of Italian Pat. Appl. N°. 85511/A/82 and in European Pat. Appl. N° 99101295.6. However, it has not yet been contrived a process for obtaining protein hydrolysates in composition with zinc such as to obtain a product of adequate quality, ready for use in one of the abovementioned fields. Hence, the technical problem underlying the present invention is to provide such a process.

Such a problem is solved by a process for obtaining protein hydrolysates in composition with zinc employing, as starting material, a protein organic material as defined in the foregoing, which is subjected to a step of hydrolysis by action of bases and/or acids and/or enzymes, and providing the exchange reaction between the amino acids and peptides salified with calcium and zinc sulphate or other zinc salts at high temperatures, solubilised beforehand in sulphuric acid solutions.

Lastly, it is provided the precipitation of any residual calcium salified by the amino acids and peptides by action, e.g., of ammonium bicarbonate, sodium bicarbonate or directly with carbon dioxide and/or other precipitating agents, like, e.g., oxalic acid and phosphoric acid.

The process according to the invention is defined in the appended claim 1. The annexed figure 1 shows a general diagram, by way of example and without limitative purposes, of the industrial process for obtaining the protein hydrolysate in composition with zinc.

With reference to the abovedefined process, it is carried out by a step of hydrolysis of protein based organic material.

The hydrolysis, as it will be illustrated in the following examples, may be carried out with bases, by treating the organic material e.g. with lime; with acid, by treating it e.g. with sulphuric acid, that along the process may advantageously be recycled; or enzymatically, by employ of a proteolytic enzyme.

Conveniently, there could be employed first an exoproteolytic enzyme, to cleave the peptide structures externally thereto, and then an endoproteolytic enzyme, to cleave the inside of said structures. To the mixture of hydrolysis it is added calcium hydroxide, for example yet not exclusively in the form of lime or lime milk. According to a preferred embodiment, zinc sulphate is then added in order to carry out an exchange reaction between the amino acids and the peptides salified with calcium and zinc sulphate. The latter may have been solubilised beforehand in sulphuric acid solutions. This step occurs at a temperature preferably higher than or equal to 90 ⁰C.

Preferably, the treatment with one or more zinc salts and/or zinc solubilised beforehand in acid solution occurs under conditions of: temperature> 120⁰C, pressure > 2.0 bar and time> 1 hour.

Lastly, it is provided the precipitation of any residual calcium (CaSOzi) salified by the amino acids and the peptides, by action of a precipitating agent, like e.g. ammonium bicarbonate, sodium bicarbonate, oxalic acid or phosphoric acid, or carbon dioxide scrubbed in the solution. - A -

The acid solution obtained after filtration may be added with zinc sulphate and used on another aliquot of medium to be subjected to treatment. Any carbon dioxide developed during the acid treatment step is used for the precipitation of residual calcium after the treatment with zinc sulphate solubilised by action of sulphuric acid. The mixture of amino acids and peptides in composition with zinc, in order to be advantageously used in agricultural, zootechnical and industrial fields is characterised by an average molecular weight of <2000 Daltons.

These analytical features are those making it particularly apt to give a greater activity to zinc. Associated to the low molecular weight and to the peculiar distribution of molecular weights of the mixture of amino acids and/or peptides there is an amount of free amino acids equal to at least 1% per each percent point of organic nitrogen.

The actual amount of zinc binding by salification, complexing or chelation with the amino acids and peptides depends on the reaction conditions between the amino acids, the peptides salified with calcium and the zinc salt added in acid solution (temperature, pressure, reaction times, pH, salt addition modes).

The products obtained according to the processes described in this patent application may optionally be dried and/or added with acids or bases or other salts in order to assure greater stability over time and to thermal shocks.

The result of the abovedescribed process may then be subjected to filtration and concentration. The starting protein organic material may optionally be integrated with amino acids or peptides of synthetic or fermentative origin and/or with other organic and inorganic zinc compounds.

The product thus obtained is useful in the zootechnical field as zinc supplement, as nutrient in the agricultural field, as protective agent for metal, glass surfaces and tissues and activator in detergency, as additive for foaming agents in the industrial field. Other industrial uses are viable in substitution to simple inorganic zinc salts, like e.g. zinc sulphate and zinc chloride, as thanks to the peculiar structure they can give particular improving properties with regard to the specific activity.

The FT-IR (Fourier Transform Infrared Spectrophotometry) technique is used for composition investigations, as any covalent bond is characterised by specific vibration sequences depending on the bond strength, therefore on its energy and on the mass of the atoms involved, and is influenced by the variations of the chemical neighbourhood. Hence, by this technique it is highlighted the presence of functional groups, obtaining information on the chemical bonds and the molecular structure. The obtained vibrational spectra offer some information about the variations of the chemical neighbourhood of the hydrolysed protein product determined by the presence of zinc, and therefore the peculiarity of these products. Due to the complexity characterizing mixtures of amino acids and peptides, specific secondary features cannot be highlighted; yet, by this technique there can be highlighted the spectral variations corresponding to the coordination of amino acids and peptides with elements. The obtained FT-IR spectra confirm the presence of coordination bonds, thereby confirming the presence of compounds justifying the peculiarity of their action.

Preparation examples Example 1 (Basic hydrolysis)

To 400 g industrial waste consisting of shaving and trimmings, 28 g lime and 2 1 water are added; then, the mass is brought to a temperature of 90⁰C, the material is left at said temperature for 6 hours and filtered, yielding 360 g cake and 2 1 medium.

The hydrolysed protein solution thus obtained (21) is added with 40 g lime and subjected to heat treatment, so as to assure the conditions: temperature =140°C, pressure = 3.6 bars; time > 30 min, finally obtaining a solution with 92g/l dry matter and 8.8 g/1 calcium content

A sample is collected to analyze molecular weight distribution, and it is checked the agreement of the analytical parameters that have been identified as optimal for obtaining these products; i.e. average molecular weight of <2000 Daltons with the entailed high content of free amino acids.

After filtration, the solution is added with a solution containing 129.6 g technical grade zinc sulphate with 22.2% zinc dissolved in an acid solution containing 70 g 50% sulphuric acid and 14O g water. The solution is subjected to the treatment under pressure at high temperatures (T > 140⁰C, p > 3.6 bar absolute) for a 30-min time. 101.4 g calcium sulphate with 63.2% dry matter is separated from the solution and the residual calcium is eliminated by carbon dioxide scrubbing, at the temperature of 80⁰C and for a 40-min time.

After filtration and concentration, there are obtained 470 g of product with a 4.5% w/w organic nitrogen, 6.0% w/w zinc and 43% w/w dry matter content.

The calcium sulphate cake obtained after the heat treatment with the acid solution of zinc sulphate is suspended with 14O g water and 70 g sulphuric acid 50% and brought to the temperature of 80 ⁰C. The solution is filtered, and the solution containing the residual zinc

(2.0% with respect to the zinc introduced) is added with 127 g zinc sulphate and used for the subsequent test, that envisaged the obtaining of another aliquot of sample.

In figure 1 it is reported by way of example a process diagram indicating the operative conditions for obtaining the abovedescribed zinc-based product. Example 2 (Acid hydrolysis)

To 2000 g ground fleshings (by-product of animal origin from category 3 hides, according to the Regulation EC 1774/2002 currently in force) there are added 280 g sulphuric acid 50% in order to attain pH < 2; the mass is brought to the temperature of 90 ⁰C and left at said temperature for 5 hours. Surfaced fat (205 g) is separated from the mass. The obtained acid suspension is added with 400 g lime milk (containing 28% lime) to attain a pH value > 11. The obtained mass is added with 250 g lime milk and subjected to a heat treatment providing continual presence under conditions: temperature > 140⁰C, pressure > 3.6 bar abs, time > 30 min. The resulting suspension is filtered, obtaining 470 g cake with 64.1% dry matter containing calcium sulphate and 2.2 1 medium with 63 g/1 dry matter and calcium content equal to 9.2 g/1.

A sample is collected to analyze molecular weight distribution, and it is checked the agreement of the analytical parameters that have been identified as optimal for obtaining these products, i.e. average molecular weight of <2000 Daltons.

Then, after filtration the solution is added with a solution containing 149.0 g technical grade zinc sulfate with 22.2% zinc dissolved in an acid solution containing 80 g sulphuric acid 50% and 16O g water.

The process provides this solution to be due to the recovering and washing of the cake obtained in a subsequent step of the process.

The solution is subjected to the treatment under pressure at high temperatures (T > 140⁰C, p > 3.6 bar abs.) for a 30-min time. Calcium sulphate is separated from the solution by filtration, and it is obtained a solution containing 13.9 g/1 zinc and 0.23 g/1 calcium. Calcium is eliminated by treatment with oxalic acid in stoichiometric amount (1.19 g) at 80⁰C for 20 min. The cake obtained in this step is treated with sulphuric acid solutions in order to redissolve the residual and filtered zinc.

The solution obtained is of course reunited to the acid solution obtained in the washing with water and sulphuric acid of the cake obtained after heat treatment with acid zinc sulphate solution and suitably added with sulphuric acid and zinc sulphate for the subsequent preparation of another aliquot of sample. The obtained calcium oxalate cake is discarded.

After filtration and concentration, there are obtained 343 g of a product with a 46.5% dry matter, 3.8% w/w organic nitrogen, 8.9% w/w zinc content. Example 3 (Enzymatic hydrolysis)

To 400 g industrial waste consisting of shaving and trimmings containing connective material, 2 1 water are added; the mass is brought to pH = 8 by addition of lime and to the temperature of 55 ⁰C, then 2 g Alcalase^® are added, the material is left at said temperature for 24 h and filtered obtaining 360 g cake and 2 1 medium.

The protein solution thus obtained (2 1) is added with 40 g lime and subjected to heat treatment so as to ensure the conditions: temperature = 140⁰C, pressure = 3.6 bar, time > 30 min, finally obtaining a solution with 89 g/1 dry matter and 10.5 g/1 calcium content.

A sample is collected to analyze molecular weight distribution, and it is checked the agreement of the analytical parameters that have been identified as optimal for obtaining these products; i.e. average molecular weight of <2000 Daltons.

Then, after filtration, the solution is added with a solution containing 154.7 g technical grade zinc sulphate with 22.2% zinc dissolved in an acid solution containing 70 g sulphuric acid 50% and 12O g water. The solution is subjected to the treatment under pressure at high temperatures (T > 140⁰C, p > 3.6 bar abs.) for a 30-min time. Calcium sulphate is separated from the solution, and the residual calcium is eliminated by addition of ammonium sulphate at the temperature of 74°C and for a 10-min time.

After the filtration, the calcium carbonate cake is treated with a solution of sulphuric acid 20% and the carbon dioxide developed is used in the step of precipitating the residual calcium.

After concentration of the filtered solution, there are obtained 513 g of a product with a 4.4% w/w organic nitrogen, 6.2% w/w zinc and 44.5% w/w dry matter content. Example 4

To 2310 g ground fleshings (Category 3 by-product of animal origin material) there are added 240 g water and 460 g sulphuric acid 40%; the mass is brought to the temperature of 90 ⁰C and left at said temperature for 5 hours. Surfaced fat (236 g) is taken out by suction. Then, to the protein medium 462 g sulphuric acid 50% are added, so as to attain pH < 1. The obtained mass is subjected to a heat treatment providing continual presence under conditions: temperature = 120⁰C, pressure = 2.0 bar abs., for a time = 8 hours. To the hydrolysed solution thus obtained there are repeatedly added 314 g lime milk at the temperature of 80⁰C allowing to attain pH > 11.

The resulting solution is filtered, obtaining 914 g cake with 68.2% dry matter containing calcium sulphate and 2.3 1 medium with 63 g/1 dry matter and a calcium content equal to 6.9 g/1. A sample is collected to analyze molecular weight distribution, and it is checked the agreement of the analytical parameters that have been identified as optimal for obtaining these products, i.e. average molecular weight of <2.000 Daltons.

Then, after filtration the solution is added with a solution containing 116.9 g technical grade zinc sulphate with 22.2% zinc dissolved in an acid solution containing 70 g sulphuric acid 50% and 140 g water. The solution is subjected to heat treatment at 100⁰C under room pressure for one hour. Calcium sulphate is separated from the solution, and it is obtained a solution containing 11.3 g/1 zinc and 0.4 g/1 calcium. Calcium is eliminated by carbon dioxide treatment at 74°C for 40 min, adjusting pH to the value of 7.5 with sodium hydroxide.

After filtration and concentration there are obtained 475 g of a product with a 41.2% w/w dry matter, 3.7% w/w organic nitrogen, 4.7% w/w zinc content. The products obtained according to this process essentially consist of amino acids and peptides salified and/or complexed and/or chelated with zinc and generally definable as containing an effective amount of zinc, which may find application in various fields. The element zinc, when associated to natural organic structures, is recognised by plant and animal organisms as being part of their system and therefore readily useful without any biochemical reprocessing to make the zinc biocompatible. In general, the organic structures associated to zinc exhibit an action that may be described as of mere carrier or are capable of activating specific processes with a remarkable metabolic saving.

The products described in this patent application, by containing zinc, may advantageously be used as zinc supplements in zootechnics, where complexes characterised by an improved biological effectiveness are required. In fact, it is known in literature that with oligoelements linked to natural organic compounds an easier absorption is attained; therefore, their contribution through food and their excreted amount can be reduced, optimizing the dosages.

The zinc element, known not merely as a biological catalyst but also as an industrial one, when associated to organic structures such as amino acids and peptides originates peculiar structures capable of performing specific functions. Let us mention, e.g., an activator function for whitening agents in detergents, a protective function as inhibitor of the corrosion of metal and glass surfaces for manual washing or for dishwashers, and in products for general cleaning, and a protective function towards fabrics and fabric dyes in detergents for washing, manually or in a washing machine. Moreover, there may be mentioned the function of foaming power enhancer, in particular for increasing foam consistency and permanence, and therefore the possible use as additive for foaming agents used in building and fire- fighting.

In particular, the products according to the present invention can act as protective agents for silver and glass and for metal surfaces in general, by performing a surface effect that inhibits the corrosion process, and thereby being useful in this field. Hence, said properties make them useful in formulations of dishwasher detergents and of detergents for cleaning metal and glass surfaces.

Moreover, the products according to the present invention may be widely useful in formulations of products for the cleaning of surfaces, for the manual cleaning of dishes and cutlery and for preparing dishwasher products, characterised by innovative whitening systems envisaging oxygen development in low-alkalinity reaction environments that require a protective agent for surfaces more exposed to corrosion.

The products according to the present invention may also be useful in laundry detergents, which are continually evolving from a formulation standpoint, as the former are catalysts of oxidizer-based whitening systems and perform a protective action on fabrics from the standpoint of dye preservation, and of reduction of damages intrinsically linked to repeated washing.

Experimental tests conducted could highlight that these products are apt to be used as additives for eliminating stains on fabrics.

Moreover, further tests highlighted that these products are useful as enhancers of the foaming activity of protein hydrolysates that, as it is well-known, are used as foaming agents for cellular concrete and fire-fighting foaming agents. At industrial level, zinc sulphate is present in several fields, like, e.g., in galvanic technology, since it is used in electrodeposition processes, in viscose rayon production as coagulating agent, in fabric dyeing and in the preparation of some inks, as catalyst of paper whitening processes used years ago and of several organic reactions. As it is well-known, zinc sulphate exhibits fungicidal and antiseptic activities; therefore, it is used as preserving agent for wood and hides. The products subject-matter of this patent that provide zinc in composition with protein hydrolysates are apt to be used as an alternative to the mere salt thereof, as the protein hydrolysates act as dispersing agents and as biological carrier, have affinity to the substrate and oppose a possible aggressiveness of the chemical environment on the materials involved in the reactions, with the further advantage of being biodegradable. The zinc element, present in several industrial applications as catalyst, activator, coagulating or precipitating agent, may advantageously be used by exploiting the availability of this element in the peculiar form thereof characterising the products of the present invention. In particular, they can in fact be used as fungicides, antiseptics, as co-formulants of paints, varnishes, vitreous enamels, vitreous varnishes, dyes for the printing, colouring, treating and processing of ceramics, glass, metal surfaces, wood, leather, fabrics and surfaces of building materials and artefacts.

To the above-described process a person skilled in the art, in order to satisfy further and contingent needs, may effect several further modifications and variants, all however falling within the protective scope of the present invention, as defined by the annexed claims.

Claims

I. A process for obtaining protein hydrolysates in composition with zinc salts employing, as starting material, a protein organic material, comprising the steps of hydrolysis by action of bases and/or acids and/or enzymes; addition of a calcium hydroxide and one or more zinc salts solubilised beforehand in an acid solution, with promotion of the exchange reaction between the amino acids and peptides salifϊed with calcium and the zinc salts at a temperature higher than or equal to 90°C; and treatment with a precipitating agent to eliminate excess calcium.

2. The process according to claim 1, wherein said protein organic material comprises by-products of animal origin and/or from waste and/or from leather tanning industry residues obtained before and after the tanning step, by-products or products of plant origin with a high protein content, agroindustrial waste, by-products or products of animal origin.

3. The process according to claim 2, wherein said protein organic material comprises leather tanning industry residues, obtained before and after the tanning step.

4. The process according to claim 2, wherein said protein organic material comprises soy and/or gluten.

5. The process according to claim 2, wherein said protein organic material comprises milk, milk derivatives, meat.

6. The process according to any one of the preceding claims, wherein the basic hydrolysis is carried out by addition of lime.

7. The process according to any one of the preceding claims, wherein the acid hydrolysis is carried out by addition of sulphuric acid, the zinc being subsequently provided by zinc sulphate.

8. The process according to any one of the preceding claims, wherein the enzymatic hydrolysis is carried out by employ of a proteolytic enzyme.

9. The process according to claim 8, wherein it is employed, in sequence, an exoproteolytic enzyme and an endoproteolytic enzyme.

10. The process according to claim 7, wherein a cake made of insoluble calcium salts and a zinc-containing protein solution is treated to boil with diluted sulphuric acid, in order to selectively wash the separated cake, obtaining an acid solution that, after filtration, is added with zinc sulphate and used on another aliquot of protein solution to be subjected to a new treatment.

I 1. The process according to claim 7, wherein carbon dioxide developed during the step of acid treatment is used for the precipitation of residual calcium after the treatment with zinc sulphate solubilised by action of sulphuric acid.

12. The process according to claim 1, wherein the precipitating agent is selected from - l i the group consisting of ammonium bicarbonate, sodium bicarbonate, oxalic acid, phosphoric acid, carbon dioxide scrubbed in the solution.

13. The process according to any one of the preceding claims, wherein the protein hydrolysate is defined by a mixture of amino acids and peptides characterised by average molecular weights of <2000 Daltons.

14. The process according to claim 13, wherein the content of free amino acids is in an amount of >1% per each percent point of organic nitrogen.

15. The process according to claim 1, wherein the treatment with one or more zinc salts and/or zinc solubilised beforehand in an acid solution occurs under conditions of > 120⁰C temperature, pressure > 2.0 bar and time > 1 hour.

16. The process according to any one of the preceding claims, wherein the resulting process is subjected to filtration and concentration.

17. The process according to any one of the preceding claims, wherein the organic material is added with amino acids or peptides of synthetic or fermentative origin.

18. The process according to any one of the preceding claims, wherein the organic material is added with other organic and inorganic zinc compounds.

19. Use of protein hydrolysate products in composition with zinc according to the process of any one of the preceding claims in the zootechnical field as zinc supplement.

20. The use of protein hydrolysate products in composition with zinc according to the process of any one of the claims 1 to 18 as nutrient, preserving agent, fungicide and antiseptic.

21. The use of protein hydrolysate products in composition with zinc according to the process of any one of the claims 1 to 18 as additive in the formulation of detergents.

22. The use of protein hydrolysate products in composition with zinc according to the process of any one of the claims 1 to 18 as catalyst and activator.

23. The use of protein hydrolysate products in composition with zinc according to the process of any one of the claims 1 to 18 as additive for foaming products.

24. The use of protein hydrolysate products in composition with zinc according to the process of any one of the claims 1 to 18 as co-formulant of paints, varnishes, vitreous enamels, vitreous varnishes, dyes for the printing, colouring, treating and processing of ceramics, glass, metal surfaces, wood, fabrics and surfaces of building materials and artefacts.