GB2207137A - Process for the preparation high bloom-grade gelatine from poultry by-products - Google Patents

Abstract

The process comprises macerating poultry by-products e.g. chicken legs, ground to a size of 25-30 mm and processed with an acid having a concentration of 2-4 % by weight at 5-30 DEG C for 24-72 hours; extracting with water in 4-5 steps at a temperature raising step-by-step from 55 DEG C to 95 DEG C at a pH value of 2.5-4.5 and at a reaction time of 4-5 hours by steps until a dry substance content of not more than 7 % by weight is reached and finally working up the extract at a pH value below 7.0.

Description

PRDCESS FOR THE PREPARATION OF GELATINE HAVING HIGH BLOOM-GRADE FROM POULTRY BY-PRODUCTS The invention relates to a processor the preparation of gelatine having a high Bloom-grade (gel -strength) from poultry by-products containing simultaneously skin and bones e.g. from chicken leg.

Fields of application of the product are various branches of food industry, pharmaceutical industry, phototechnical industry and household.

In the Hungarian patent No. 164,372 the prepar tion of aspic-jelly is disclosed. The drawback of the process resides in the fact that the end-product can not be converted into powder-form gelatine from which the original sol-gel state could be restored in addition to water at any time.

According to the Hungarian patent application No.

3406/84 gelatine is prepared by enzymatic processing of chicken leg. According to the Hungarian patent application having a registration number 10,647 chicken leg is worked up at a pH value of 10-11.

The disadvantage of the above methods is that they do not enable the digestion of the complete amount of collagen. For this reason the yields of the processes (generally about 2.5-2.7 %) and the Bloom-grade of the end-product are low. The process disclosed in the Hungarian patent application filed under the registration No. 10,674 is accompanied by the further drawback that due to the high pH value the fat content is not globulated and the separation thereof is comp- licated.

There is a demand for a process which enables the preparation of gelatine having a Bloom-grade of A 4136-5277 at least lBOgthis is the minimal value ordained for alimentary purposes, Hungarian standard No. 08/1159- in a simple manner with high yields.

It is the object of the present invention to elaborate a process whereby the complete collagen content of the processed and digested starting material is extracted and after working-up gelatine having Bloom-grade of at least 220-240 and possessing chemical and microbiological parameters, which meet the heaith regulation, is obtained.

The present invention is based on the recognition that a product complying with the above requirements is obtained if the starting material is not cut into small pieces, the acidic maceration is carried out with diluted acid at ambiant temperature and thereafter the aqueous extraction is carried out in several steps at acidic pH value whereby the temperature is raised step-by-step and finally the extract is worked up at a pH value below 7.0.

According to the present invention there is provided a process for the preparation of gelatine having high Bloom-grade by subjecting poultry by-products to processing, acidic maceration and aqueous extraction and working up the extract, which comprises maccrating poultry by-products ground to a size of 25-30 mm and processed with an acid having a concentration of 2-4 % by weight at 5-30 0C for 24-72 hours, thereafter extracting with water in 4-5 steps at a temperature raising step-by-step from 5S 0C to 95 OC at a pH value of 2.5-4.5 and at a reaction time of 4-5 hours by steps until a dry substance content of not more than 7 % by weight is reached and finally working up the extract at a pH value below 7.0.

According to the process of the present invention by-products obtained by the working-up of animals slaughtered at the age of 7-8 weeks (preferably chicken-leg containing simultaneously both skin and bones) are used as starting material, which by-products have been hitherto either used for fodder purposes or discarded as wastage.

Due to the high collagen content of the said starting material, gelatine can be prepared by hydrolysis with a diluted acid having a low concentration and subsequent extraction carried out by thermal treatment.

The starting material is processed by treating the poultry by-products with water heated to 80-85 OC for 1-5 seconds. Hereby the upper horn layer becomes loose but during the treatment lasting only a few seconds the worm water does not penetrate into thE internal parts of the starting material and consequently does not lyse the collagen. In order to loosen the horn layer completely, the starting material is thereafter treated with water having a temperature of 55-60 OC for 1-2 minutes. The loosened horn layer is removed with the aid of a suitable equipment (e.g.

leg cleaning machine) whereby further impurities of the chicken leg are also removed and the bacterological contamination is reduced to a minimal value.

The purified starting material is disintegrated in a chopper to pieces of 25-30 mm. In the case of a larger particle size the efficiency of aqueous extraction is decreased, while a smaller particle size results in the cutting of the iong-chained collagen molecule which causes a reduction of the yield on the one and and a decrease of the Bloom-grade of the end -product on the other.

It is preferred to carry out disintegration on an industrial meat-chopper equipped with a disc having a hole diameter of 25-30 mm. From the crushed starting material the freely bond fats and a part of protein of non-collagenic character are washed out with water at ambiant temperature. During this treatment further contaminations formed in the course of chopping are also removed.

The chopped poultry by-products are macerated with an acid having a concentration of 2-4 0 by weight at a temperature between 5 and 30 0C for 24-72 hours, depending on the quality of the starting material.

Maceration is carried out by using diluted acid in an amount equal to that of the starting material.

As acid any inorganic or organic acid can be used (e.g. hydrochloric acid, sulfurous acid, sulfuric acid, phosphoric acid, nitric acid, acetic acid or formic acid).

Maceration is preferably accomplished for 48 hours by using 3 % by weight sulfuric acid. Because of a decrease of the concentration, the acid is replaced by fresh acid after 24 hours.

After acidic maceration the product is washed with water until a pH value of 2.5-4.5 - preferably 3.0-3.7 - is reached.

The pH value having been adjusted the product is extracted with water. Aqueous extraction is carried out in 4-5 steps at 55-95 OC until a dry substance content of nct more than 7 % by weight is reached.

Each extraction step is accomplished for 4-5 hours whereby the temperature is raised stepwise. Good results are obtained by carrying out extraction in four steps at 55 Or, 65 OC, 75 0C and 85 OC or in five steps, whereas the temperature of the fifth step is 95 C.

One must take care of keeping the dry substance content of the solution below 7 % by weight, preferably below 6.5 % by weight.

The dry substance content may be determined by any suitable known method (e.g. by a method based on evaporation in vacuo or measuring the refraction).

The product is kept at a pH value between 2.5 and 4.5, preferably at 3.0-3.7 in each step of the extraction, whereby the fat content of the product is globulated and the complete amount thereof forms a supernatant. The said layer may be easily removed from the gelatine phase by separation or overflowing.

After each extraction step the extracts are adjusted to a pH value below 7.0 - preferably to 6.8 with an alkali (preferably ammonium hydroxide), whereupon the extracts are united.

In the course of the multi-step extraction of the present invention the collagen molecules are gradually extracted. Accordingly gelatine having the highest Bloom-grade (generally above 300) is obtained from the extract of the first step, whereby gelatine having the lowest Bloom-grade (generally below 150) is formed in the fourth or fifth step. Extraction of collagen molecules which form gelatine of lower Bloom-grade gives naturally rise to a significant im provement of the yield.

If gelatine having a particularly high 8loom- -grade (e.g. 300-320) is to be prepared for special fields of applications (e.g. in pharmaceutical indust ry for the preparation of gelatine capsules) one may proceed by carrying out only one, two or eventually three extraction steps and uniting the extracts thus obtained. In this case, however, the yield is decreased.

The gelatine phase obtained after uniting the extracts is worked up to forms suitable for commercial piposes by methods of food industry known per se. One must take care,however, of keeping the.pH value below 7.0.

The white precipitate remaining in the gelatine phase after working-up and the minor amount of fats is removed by pre-filtration or microfiltration, whereafter ultrafiltration is carried out whereby in addition to concentrating the sterilization of the gelatine layer is accomplished too. The quality of the gelatine end-product can be controlled by the size of the membrane used for filtration. A properly selected membrane (preferably membrane size 5000) lets collagens cf smaller molecular weight to pass through without considerably affecting the Bloom-grade in an adverse manner, whereby the yield is increased.

Sterilization and final concentrating are accomplished by injecting vapour. Thus a product having a dry substance content of 20-30 % by weight is obtained. In order to obtain a completely pure odourless product this operation is preferably carried out by using activated cbar-coal.

The concentrated and sterilized gelatine layer is converted from sol-state to gel-state by cooling, whereupon it is ground and dried. Drying is started by using cold air having a temperature of about 15 0C and temperature is then gradually raised to 60 C.

On raising the temperature one should take care of keeping the gelatine in the gel-state, i.e. gelatine should not be converted into sol-state.

Further details of the present invention are to be found in the following Examples without limiting the scope of protection to the said Examples.

Example 100 kg of chicken leg are cleaned from the external horn layer and crude impurities. The starting material is ground on a disc having a hole-diameter of 30 mm. The volume of the crushed chicken legs amounts to 0.116 m3. The crushed chicken legs are washed with 0 308 1 of water having a temperature of 10 C until the water becomes slightly pink. The precipitated fats (1.5 kg) are collected.

Acidic maceration is carried out by using 3 % by weight sulfuric acid twice for 2 hours each. After the first 24 hours' period the digested solution is exchanged for fresh sulfuric acid. The substance is then washed with an abundant amount of water (about 1980 1) to a pH value of 3.7.

Aqueous extraction is carried out in four steps at a temperature of 55 OC, 65 Or, 75 OC and 85 C, respectively. Water having the desired temperature is pumped onto the product at a volume that it covers the substance by 10 cm. The product is allowed to stand for the desired period of time, whereby the supernatant fats are separated time by time. The volume of the extracts thus obtained amounts to 140, 100, 70 and 90 1, respectively, while the dry substance thereof is - in the same order of succession -, 4.6, 5.5, 2.6 and 1.5 % by weight, respectively. The residue weights 32.5 kg.

The extracts are adjusted to a pH value of 6.8 with ammonium hydroxide. On increasing the pH value the white flocculent precipitate formed is filtered off, the four extracts.are united and concentrated by ultrafiltration. The said ultrafiltration step is carried GUt with a 5000 membrane,at a temperature of 45-55 OC for 3 hours. Thus from the gelatine layer (359 kg) having a dry substance content of 4 % by weight by ultrafiltration 77 kg of a concentrate having a dry substance content of 13.5 h by weight are obtained. The concentrate thus obtained is further concentrated in vacuo until a dry substance content of 25 % by weight is reached. The product weights 36 kg.

The product thus obtained is cooled, ground and dried on the air for 48 hours. The temperature of the air used for drying is gradually raised from 20 CC to 80 C. Thus 7.5 kg of an end-product having a Bloom -grade of 240-245 are obtained, yield 7.5 %.

Claims (8)

1. Process for the preparation of gelatine having high Bloom-grade by subjecting poultry by-products to processing, acidic maceration and aqueous extraction and working up the extract, which comprises macerating poultry by-products ground to a size of 25-30 mm and processed with an acid having a content ration of 2-4 % by weight at 5-30 0C for 24-72 hours, thereafter extracting with water in 1-5 steps at a temperature raising step-by-step from 55 OC to 95 0C at a pH value of 2.5-4.5 and at a reaction time of 4-5 hours by steps until a dry substance content of not more than 7 % by weight is reached and finally working up the extract at a pH value below 7.0.

2. Process according to Claim 1 which comprises carrying out acidic maceration with an acid having a concentration of 3 % by weight for 48 hours and if desired exchanging the used acid after 24 hours for fresh acid.

3. Process according to Claim 1 or 2 which compri- ses carrying out aqueous extraction at a temperature of 55 OC, 65 C, 75 C, 85 OC and if desired at 95 C, until a dry substance content of not more than 6.5 % by weight is reached.

4. Process according to any of Claims 1-3 which comprises removing the supernatent fats globulated during extraction by separation or overflowing.

5. Process according to any of Claims 1-4 which comprises working up the extract by filtration at a pH value below 6.8, sterilization, concentration, cooling and drying.

6. A process as claimed in any one of claims 1 to 5, wherein four to five extraction steps are conducted.

7. A process substantially as hereinbefore described in the Example.

8. Geltaine when produced by the process as claimed in any one of claims 1 to 7.