GB2066265A - A process for decreasing the phenylalanine content of protein hydrolysates and meat-aroma concentrates prepared therefrom - Google Patents

Abstract

Protein hydrolysates or meat- aroma concentrates are subjected to chromatography on a chromatographical column filled with a beta -cyclodextrin polymer to reduce their phenylalanine content.

Description

SPECIFICATION Process for decreasing the phenylalanine content of protein hydrolysates and meat-aroma concentrate prepared therefrom This invention relates to a process for decreasing the phenylalanine content of protein hydrolysates and meat-aroma concentrates prepared therefrom.

The protein hydrolysates poor in phenylalanine and products prepared therefrom, such as meat-aroma concentrates play an especially important role in the protein supply of patients suffering from phenylketonuria.

More attempts have been made to decrease the quantity of phenylalanine in protein hydrolysates.

S. M. Partridge and R. C. Brinley [Biochem. J., 51, 628(1951)] eliminated phenylalanine and tyrosine from protein hydrolysates by ion exchange displacement chromatographical method (Zeo-Carb 215, DOWEX 2 and sulfonated polystyrol resin), using 0.075 N sodium hydroxide and 0.1 5 N ammonium hydroxide for the elution.

This preparative ion exchange method was further developed by P. N. Campbell, S. Jacobs and T. S. Work [Chem. and Ind., 117, 1975] wo used a Zoo-Karb 225 resin.

P. Celretti, G. Montesi and N. Silipradi [Arch. Science Biol., 11, 554 (1 957)] separated phenylalanine from a protein hydrolysate by a preparative method, on an Amberlite-lRC-50 resin. A common disadvantage of the processes known in the art for preparing protein hydrolysates, which are poor in phenylalanine consists in the fact that they are highly expensive and the taste of the products obtained in unsatisfactory, the products are practically uneatable.

The unfavourable properties of the phenylalanine-free protein hydrolysates prepared by ion exchange chromatography are due to the hydrolysis procedure. To be able to carry out the ion exchange chromatography, protein hydrolysates with a low salt concentration are required, therefore the hydrolysis is performed with sulfuric acid instead of hydrochloric acid, since sulfuric acid can easily be eliminated from the system in the form of its calcium salt.

It is also known that in the protein hydrolysates prepared with sulfuric acid off-flavour components are present [DE-PS 127,693; Predesgast, K. Food Trade 44, 14 to 21(1974)].

According to the GB-PS 1,091,637 ss-cyclodextrin can be cross-linked with different bifunctional compounds, e.g. epichlorohydrine, dichlorophydrine, diepoxy butane, diepoxy propylether, etc., and thus ss-cyclodextrin polymers are obtained.

It is further known that fi-cyclodextrin polymers form complexes with appropriate compounds, for example with aromatic amino acids.

Wiedenhof [Stärke, 21, 163 (1969)] reported that the complex forming properties of cyclodextrin polymers served as a basis for a new method of analytical chomatography, the gelinclusion chromatography.

Zsadon et al. [Stärke, 31, 11 (1979)1 described an analytical method, by which phenylalanine, tryptophan and tyrosine could simultaneously be separated from aliphatic amino acids.

The methods known for the separation of aliphatic and aromatic amino acids have not been used for preparative purposes up to the present time.

The known methods referred to hereinabove all related to the analytical separation and aromatic amino acids from amino acid mixtures by means of cyclodextrin polymers, none of them aimed at the preparation of protein hydrolysates, poor in phenylalanine. On the other hand, the present invention relates to a process for decreasing the phenylalanine content of protein hydrolysates and reaction products thereof, which can be accomplished also in industrial scale.

There is a long-standing need for a method by which phynylalanine can be eliminated from hydrolysates containing 10 to 30% amino acids and 10 to 30% by weight of sodium chloride.

The invention is based on the surprising discovery that under certain, specific conditions phenylalanine can be separated also preparatively from such concentrated solutions, More particularly, the separation must be carried out under conditions, which ensure that the ss cyclodextrin polymer shows a high, specific complex forming activity against phenylalanine.

It is supported by numerous experimental evidences that the absorption of phenylalanine and tyrosine by the ss-cyclodextrin polymer depends on the concentration of the two amino acids in the protein hydrolysate.

The sodium chloride concentration of the protein hydrolysates employed could be decreased by the process disclosed in the DDR-PS 127,693 or by electrodialysis.

The quantity of the phenylalanine absorbed by 1 g. of ss-cyclodextrin depends on the diameter of the separation column filled with the polymer, from the height of the column, the concentration of phenylalanine in the solution to be treated, the elution speed, pH and temperature. It is an interesting observation that the quantity of phenylalanine absorbed by 1 g.

of polymer increases by increasing concentration of phenylalanine.

Generally, the protein hydrolysate to be treated should be adjusted to contain 0.5 to 3 g./lit.

of phenylalanine, 10 to 30%, preferably 20% of amino acid, 20 to 50%, preferably 40% of solid substance. To 100 parts by weight of a protein hydrolysate 10 to 100 parts by weight of a cyclodextrin polymer are added.

The appropriate values of the parameters required for the separation of phenylalanine, e.g.

pH, temperature, dimensions of the column were selected. Details of the separation carried out are to be found in Table 1.

Further details of the inventive process are illustrated by the following Example, which is, however, not intended to limit the scope of the invention in any way.

Example 45 parts by weight of a ss-cyclodextrin polymer (prepared according to DOS 29 27 733) are swollen in water and filled into a chromatographic column of 70 X 2.5 cm. 100 parts by weight of a kazeine hydrolysate containing 40% by weight of solid substances, 20% by weight of amino acid, 20% by weight of sodium chloride and 0. 15% by weight of phenylalanine (pH = 6) were passed through the column. The dead volume was discharged. Using pressure and vacuum the hydrolysate could entirely be pumped or sucked through the column. The composition of the solution leaving the column was as follows: solid substance content 35% amino acid content 17% sodium chloride content 18% phenylalanine content 0.2% Diluting this hydrolysate to a sodium chloride concentration of 1.5% a tasty preparate is obtained, having a meat taste.

The ss-cyclodextrin polymer was prepared from cyclodextrin or cyclodextrin-containing carbohydrate mixture by cross-linking in the presence of polyvinyl alcohol, polyvinyl acetate of a polyvinyl alcohol acetate copolymer, by means of a polyfunctional reactant capable of reacting with the cyclodextrin and the polymer (see the DOS 29 27 733).

Table 1 The formation of cyclodextrin-polymer-phenylalanine complex as a function of phenylalanine concentration in aqueous medium (pH = 7, column diameter = 1 6 mm.) Quantity of ss-cyclodextrin: 6.5 g.

height of column: 2 cm.

concentration of initial quantity of absorbed phenylalanine phenylalanine (mg.) phenylalanine phenylalanine (mg.) [mg.] [%] absorbed by 1 g. of [mg./100 ml.] polymer 50 15 mg. (in 30 ml.) 1.25 8.3 2.5 100 30 mg. (in 30 ml.) 1.70 5.7 3.5 150 45 mg. (in 30 ml.) 2.00 4.4 4.0 Quantity of ss-cyclodextrin: 1.0 g.

height of column: 4 cm.

50 15 mg. (in 30 ml.) 1.75 11.7 1.7 100 30 mg. (in 30 ml.) 2.95 9.8 3.0 150 45 mg. (in 30 ml.) 4.00 8.9 4.0 Quantity of ss-cyclodextrin: 2.0 g.

height of column: 7 cm.

50 15 mg. (in 30 ml.) 3.25 21.7 1.6 100 30 mg. (in 30 ml.) 4.70 15.7 2.4 150 45 mg. (in 30 ml.) 7.75 17.2 3.9 Quantity of ss-cyclodextrin: 3.0 g.

height of column: 10 cm.

50 15 mg. (in 30 ml.) 4.80 32.0 1.6 100 30 mg. (in 30 ml.) 7.00 23.3 2.3 1 50 45 mg. (in 30 ml.) 11.25 25.0 3.8

Claims (5)

1. Process for decreasing the phenylalanine content of protein hydrolysates and meat-aroma concentrates prepared therefrom, which comprises subjecting the protein hydrolysate or meataroma concentrate to chomatograohy on a column filled with a fi-cyclodextrin polymer.

2. A process as claimed in claim 1, which comprises adjusting the phenylalanine concentration to 0.5 to 3 g./lit., the total amino acid content to 10 to 30% by weight and the solid substance content to 20 to 50% by weight on the protein hydrolysate to be treated.

3. A process as claimed in claim 2, which comprises adjusting the total amino acid content to 20% by weight and the solid substance content to 40% by weight in the protein hydrolysate to be treated.

4. A process as claimed in any one of claims 1 to 3, which comprises passing 100 parts by weight of a protein hydrolysate through 10 to 100 parts by weight of a fi-cyclodextrin polymer column.

5. A process as claimed in any one of claims 1 to 4, which comprises preparing the ss- cyclodextrin polymer employed from cyclodextrin or a cyclodextrin-containing carbohydrate mixture, in the presence of polyvinyl alcohol acetate copolymer, by cross-linking with a polyfunctional reactant capable of reacting with cyclodextrin and the polymer.