DE102005028578A1 - Pretreatment of collagen-containing material such as bones or pig skin for production of gelatin, involves cleavage of crosslinks by treatment with liquid ammonia, optionally in presence of ammono-acid or -base - Google Patents

Abstract

A method for the pre-treatment of collagen-containing raw materials (I) for the production of gelatin, involves treating (I) with liquid ammonia, optionally in presence of an ammono acid or ammono base as catalyst for ammonolysis, so as to bring about cleavage of intermolecular and intramolecular crosslinks in the triple-helical collagen structure.

Description

The The invention relates to a method for the treatment of collagen-containing animal raw materials such as demineralized bone, pigskin, Bovine cleft etc. with the aim of intra- and intermolecular cross-linking partially split between the collagen chains. This split is done by contacting the raw materials with liquid ammonia at opposite Atmospheric pressure increased pressure in a pressure vessel and subsequent relaxation of the pressure to normal pressure.

collagen-containing animal raw materials from which gelatine is produced should, have to the extraction of the gelatin are subjected to pretreatments.

These serve to swell and soften the collagen and intermolecular Peptide bonds and cross-links between the helical polypeptide strands - partially - hydrolytic to solve.

For the production of collagen gelatin is treated by two methods (Ullmann's Encyclopedia of Industrial Chemistry, ^© 2000-2004, Vol. 15, 471 ff.).

The acidic process that developed in the thirties in the US was used to produce type A gelatin (A = acid processed). It will be mainly used to produce gelatin from pork rinds. at This raw material is due to the degree of cross-linking of the collagen of low age of animals not so high. Therefore, one is enough Acid pretreatment for 24-48 hours at pH values around 1-2, for a later to achieve good gelatin extractability.

The classical, alkaline methods for obtaining type B gelatin (B = basic processed) finds mainly for the production of gelatin from cattle and bone use. This will be Ossein or Rinderspalt a 8-12 Weekly treatment subjected to a suspension of calcium hydroxide (called "shearing"). During this process step, which expires at 15-20 ° C, that will Reaction medium renewed several times, and by gentle mechanical Movement becomes even Distribution of the material guaranteed. In addition, a one to two-week "shearing" with dilute sodium hydroxide solution is usual in cattle skin.

• • Extraktion von alkalilöslichen, nicht kollagenen Proteinen (Proteoglycane, Blutserumalbumine)
• • Entfernung unerwünschter Komponenten des Bindegewebes (Nukleinsäuren, Kohlenhydrate)
• • Verseifung des Restfettgehaltes
• • Hydrolyse von kovalenten Quervernetzungen des Kollagens („reife", nicht reduzierbare Quervernetzungen).

The pretreatment of the raw materials at pH values of 12-13 in the Type B process pursues the objectives:

• • Extraction of alkali-soluble, non-collagenous proteins (proteoglycans, blood serum albumins)
• Removal of unwanted connective tissue components (nucleic acids, carbohydrates)
• • saponification of the residual fat content
• • Hydrolysis of covalent cross-links of collagen (mature, non-reducible crosslinks).

collagen consists of three polypeptide chains in the form of special left-handed Helices, which turn right rotated around each other (triple helix).

collagens take - once formed - not further participate in the metabolism and age through regular increase in cross-linking due to formation of hydrogen bonds, ester bonds of Amino acid- with sugar residues and isopeptide bonds between elongated ones Amino acid chains.

These to lead to the cross-linking mentioned above, in turn for the stability of collagen responsible for thermal, mechanical and enzymatic stress are.

In front The actual gelatin extraction will be the pretreated raw materials acid-free (type A process) or alkali-free washed (Type B method). From the thus obtained collagen rich Raw material is obtained in several steps gelatin. The raw gelatin is batchwise from the largely salt-free washed starting material extracted.

The Prior art pretreatments have some disadvantages on. So the treatments are in the alkaline process time very expensive. The long residence times require the use relatively large-volume reactors. The multiple renewal of the reaction medium causes costs in the processing of the extracts.

The Use of strong alkalis gives rise to the elimination of ammonia under aldimine formation.

Of the Use of strong alkalis requires their neutralization with acids. The thereby formed salts must be washed out before extraction of the crude gelatin.

The invention is therefore based on the object to provide a method for the pretreatment of collagen-containing raw materials for the production of gelatin, which reduce or eliminate the disadvantages of the prior art is able to.

• – die tierischen Materialien einen hohen Wassergehalt (> 50 Masse %) aufweisen
• – die tierischen Materialien in zerkleinerter Form eingesetzt werden
• – man das Ammoniak bei Raumtemperatur oder bei einer höheren Temperatur als Raumtemperatur auf die Rohmaterialien einwirken lässt
• – man nach der Entspannung das im Druckgefäss dann noch verbliebene Ammoniak bis auf einen Minimalgehalt entfernt
• – man wahlweise dem flüssigen Ammoniak vor dem Beginn der Behandlung eine Ammonobase oder Ammonosäure als Katalysator für die Ammonolyse der intermolekularen und intramolekularen Quervernetzungen beigibt.

This object is achieved according to the invention by a method for treating collagen-containing animal raw materials by contacting these materials with liquid ammonia in relation to amospheric pressure increased pressure in a pressure vessel and subsequent relaxation of the pressure to atmospheric pressure, said

• - The animal materials have a high water content (> 50% by mass)
• - The animal materials are used in crushed form
• - The ammonia is allowed to act on the raw materials at room temperature or at a higher temperature than room temperature
• - After the expansion, the remaining in the pressure vessel then ammonia removed to a minimum level
• - It is optionally added to the liquid ammonia before the start of treatment, an ammonia or ammonio acid as a catalyst for the ammonolysis of the intermolecular and intramolecular cross-links.

As a result of the self-ionization of liquid ammonia (p _Ka = 34), ammonium salts in liquid ammonia are protic acids (ammonic acids) and amides are ammonobases. Since water has a p _Ka value of 14, substances which are not acids in water show p _Ka values in the range of 14 to 34 acid character in liquid ammonia (G.Jander, H. Spandau and CC Addison "Chemie in non-aqueous ionizing solvents "Friedr. Vieweg and Sohn, Braunschweig 1963, sub-band 2 by Herchel Smith)

Prefers you choose as quantity ratio 5 mass units of ammonia to 10 mass units of collagen-containing Raw material up to 20 mass units ammonia to 10 mass units collagen-containing raw material (mass units of raw material are here to be understood as dry matter).

One Too high a water content may occur in an upstream treatment step by adding liquid Ammonia to the highly hydrous raw materials and stripping the aqueous ammonia solution the wished Mass be reduced.

Further It is preferable to consider the distance of the after relaxation in the pressure vessel Remaining ammonia by suction, pumping, blowing or by Heat the contents of the pressure vessel to a temperature that is at least room temperature, accomplished.

After all it is still preferable that the escape during the relaxation gaseous Ammonia collected and compressed again to liquid ammonia becomes. The same applies the gaseous Ammonia, which after relaxation from the treated raw material is still removed.

For the inventive method becomes a pressure vessel, So a pressure-resistant vessel used. On the nature of this pressure vessel are no special To make demands. The term "pressure vessel" as far as possible in the context of the invention be understood. The pressure vessel may be for example an autoclave.

The Use of ammonia as a base instead of calcium hydroxide or Sodium hydroxide has the advantage that ammonia is above its boiling point of -33 ° C as gas can be easily expelled from the raw material to be treated. On a neutralization with the addition of acids can therefore largely be waived. ammonia solutions in water, from 60% by mass, ammonia has pH values from more than 12.4 up.

• – Flüssiges Ammoniak ist ein hervorragendes Quellmittel. Wasserstoffbrückenbindungen werden durch Ammoniak aufgehoben.
• – Flüssiges Ammoniak ist in der Lage, nicht-kollagene Proteine und Nukleinsäuren zu lösen. Kohlenhydrate niedriger Molmasse werden ebenfalls gut gelöst.
• – Fette können durch Ammoniak verseift werden
• – Ester, wie zwischen Aminosäuren und Zuckerresten, können durch flüssiges Ammoniak ebenfalls ammonolytisch gespalten werden.
• – Isopeptide unter Beteiligung end- oder seitenständiger Diaminocarbonsäuren oder Aminodicarbonsäuren können durch Ammoniak gespalten werden.

Liquid ammonia can affect the cross-linking of collagen in several ways:

• - Liquid ammonia is an excellent swelling agent. Hydrogen bonds are abolished by ammonia.
• - Liquid ammonia is able to dissolve non-collagenous proteins and nucleic acids. Carbohydrates of low molecular weight are also dissolved well.
• - Fats can be saponified by ammonia
• - Esters, as between amino acids and sugar residues, can also be split ammonolytically by liquid ammonia.
• Isopeptides with the participation of terminal or pendant diaminocarboxylic acids or aminodicarboxylic acids can be cleaved by ammonia.

For example, ammonia is capable of complete cleavage of amide bonds US 5,302,756 (Depolymerization of polyamides).

• – da das erfindungsgemässe Verfahren nicht bei tiefen Temperaturen stattfindet, kann auf aufwendige Kühlapparaturen verzichtet werden
• – mit dem erfindungsgemässen Verfahren können wesentlich kürzere Behandlungsdauern erreicht werden
• – mit dem erfindungsgemässen Verfahren findet keine Deaminierung des Kollagens unter Ammoniakentwicklung statt
• – mit dem erfindungsgemässen Verfahren wird die Salzbildung stark verringert
• – mit dem erfindungsgemässen Verfahren wird die Menge an Waschwasser stark verringert, was wiederum den Aufwand für die Aufarbeitung der wässrigen Waschextrakte zu minimieren ermöglicht
• – mit dem erfindungsgemässen Verfahren werden die Kosten für die Gelatineproduktion deutlich verringert

The invention achieves the following advantages:

• - Since the inventive method does not take place at low temperatures, can be dispensed with expensive cooling equipment
• - With the inventive method much shorter treatment periods can be achieved
• - With the inventive method no deamination of the collagen takes place under evolution of ammonia
• - With the inventive method is the Salt formation greatly reduced
• - With the inventive method, the amount of wash water is greatly reduced, which in turn allows to minimize the effort for the workup of the aqueous washing extracts
• - With the inventive method, the cost of gelatin production are significantly reduced

For the procedure According to the invention, a cylindrical autoclave with a capacity of 750 ml used. The autoclave was with an electric heater equipped with thermostatic control. In this autoclave were 50 g Collagenous material (pork rind) with a water content given by 80%. Through a valve on the top of the autoclave were 100 g of liquid Ammonia introduced into the now closed autoclave, after which the valve was closed. The temperature in the autoclave was 20 ° C. After introduction of the ammonia, the temperature dropped slightly, the pressure in the autoclave was 5 bar. By means of the regulated electric heating was the Autoclave at 70 ° C (30 bar) heated up. Under these conditions became the autoclave for 2 days and leave for 16 hours. At the end of this period, the previously mentioned Valve on autoclave open, whereby the ammonia abruptly escaped and the contents of the autoclave relaxed to atmospheric pressure was. After opening of the autoclave, the ammonia-treated raw material was taken out. Unlike untreated raw material, this was ammonia-treated Raw material partially soluble in cold water.

Claims (6)

Process for the pretreatment of collagen-containing raw materials for the production of gelatin, characterized in that collagen-containing raw materials are subjected to treatment with liquid ammonia, optionally in the presence of an ammonic acid or an ammonobase as a catalyst for the ammonolysis, to cleave intermolecular and intramolecular cross-links of the triple helical collagen structure , The method of claim 1, wherein the cleavage of the intermolecular and intramolecular cross-linking of triple helicals Collagen structure with the addition of ammonium salts of inorganic acids as Catalyst performed becomes. Process according to claims 1 and 2, whereby the cleavage at temperatures between -33 ° C and 100 ° C is performed. Method according to one of the preceding claims, according to which the cleavage is carried out at ammonia pressures between 0 and 60 bar. The method of claim 2, wherein the catalyst an ammonium chloride, ammonium bromide, ammonium iodide or a diammonium hydrogen phosphate is. The method of claim 1, wherein the mass ratio of liquid Ammonia to collagen-containing material (as dry matter) is the same 10: 1, preferably 6: 1 and most preferably 4: 1.