High-Bloom Grade Gelatin Manufacturing Process from Poultry (chicken, turkey, duck, goose) Tissues

The invention is related to production of gelatin from the collagen that exists in the tissues of poultry (chicken, turkey, duck, goose).

The mentioned technique ensures low energy and water consumption to manufacture high-bloom grade gelatin within short process lead times at optimized physical conditions by using specified chemicals herein.

No previous invention and technology has been detected in Turkey regading gelatin manufacturing from poultry tissues.

According to the Description of GB2207137 (A);

i. Chicken skin and bones are ground to a size of 25-30 mm.

ii. Sulphuric acid is added to the ground chicken skin and bones at 4% max. By weight and in the first phase waited for 24 hours, acid is replaced by fresh acid after 24 hours and waited for another 24 hours.

iii. After acidic maceration the product is washed with water and hydrolysis is carried out at 55, 65, 75, 85 and 95 °C degrees. Each extraction step is accomplished in 4-5 hours, which means it takes 20-25 hours in total for the entire hydrolysis phase to be completed.

iv. Following the 5 micron ultra filtration, product is dried by air.

Acccording to the aforesaid invention (GB2207137(A)) approximately 120 hours are required to obtain gelatin from raw material by consuming significant amount of water and energy.

The objective of the present invention is to obtain high bloom grade (over 100), odorles, transparent and fat free gelatin from poultry (chicken, turkey, duck, goose) tissues with a total process lead time under 60 hours.

The process flow diagram of the present invention is given in the attachment.

Figure-1: Process Flow Diagram

l Detailed Description of the Present Invention

The present invention cosists of the folowing process steps;

Decreasing the Ph Value of the Poultry (chicken, turkey, duck, goose) Tissues and Rinsing

In the prior art, chicken skins and bones were ground to size between 25 mm and 30 mm

In the present invention poutry tissues are ground to a size between 2 mm and 10 mm at a temperature range of 5 °C (deggre celcius) to -4 °C, 0 °C is preferred.

After grinding the tissues to the above mentioned size range, water and hyrochloric acid at 30-33% concentration is added to tissues. The amount of water is 60 % of the tissues by weight and amount of hydrochloric acid (30-33%) is 2-3% of the tissues by weight. The waiting period is 10 to 12 hours at Ph value between 1.0 to 1.5.

In the description of GB2207137 (A) 1989-01-25 sulphuric acid was used as Ph reducer having a concentration of 2-4 % by weight with an initial waiting period of 24 hours and the acid was replaced by fresh acid after 24 hours and waited for an other 24 hours.

Due to the very low Ph values obtained by sulphuric acid, fat tissues would stick on the skin and bone particules which cause extraction problems and in addition more salt would occur while increasing the Ph value to certain point before hydrolysis and these would increase the process cost and decrease the gelatin quality.

By the present invention, decreased Ph value of poultry tissues (between 1.0 to 1.5) is increased to 2.5-3.0 by rinsing with water, 2.7 is preferred.

Increasing the Ph value of Poultry Tissues by Alkaline Buffer Solution and Rinsing

NH ₄ OH+(NH4) ₂ S0 ₄ alkaline buffer solution is added to the poultry tissues in between 0.5% to 1% by weight then waited for 0.5 hour to 1 hour time period to increase the Ph to 3.5-4.5 range, preferrably to 4.0.

After increasing the Ph value of poultry tissues to 3.5 to 4.5 range, salt is removed from the poultry tissues by rinsing with water at temperature 15 °C to 25 °C. Ph value shall not go over 5.5 during rinsing process.

Hydrolysis of Ph Adjusted Poultry Tissues

As it is mentioned in GB2207137 (A) 1989-01-25 description, hydrolysis is carried out at multiple temperatures (55 °C, 65 °C, 75 °C, 85 °C and 95 °C).

One of the important step of the present invention, 90% of the collagen existing in the poultry tissues is hydrolyized at two temperature points i.e. 61 °C and 81 °C by using the alkaline buffer solution. The hyrolysis takes place ina jacket heater which ensures homogenous heating without direct touch of poultry tissues to heating source. Hydrolysis at two temperature points decreases the operating costs, durations (lead times) and equipment requirements.

First hydrolysis temperature is between 55 °C and 65 °C, preferrably 61 °C and the second hydrolysis temperature is between 70 °C and 90 °C, preferrably 81 °C.

The obtained gelatin solutions are stored in seperate tanks.

Duration of each hydrolysis step is 6 to 10 hours.

Filtration of Gelatin Solution from Hydrolyized Poultry Tissues

Three products are obtained as a result of the hydrolysis process. These are fat, residue (cohed skin and bone particules) and gelatin solution.

35-40 units fat, 15-20 units residue and 50-40 units gelatin solution are typically obtained from a 100 units poultry tissue by weight.

The gelatin solution obtained by the hydrolysis of collagen is then filtered by a filter that has cotton with 1:0.1 volume ratio.

Concentration of the the Filtered Gelatin Solution

After the hydrolysis of poultry tissues, the water content of the obtained gelatin solution is 96-97%

The water content of the gelatin solution is decreased to 20-30% at temperature values between 40 °C to 80 °C by using reverse osmosis filtration.

Typical application for the removal of excess water is evaporation. However this method takes longer times and is more expensive compared to the above mentioned technique. In addition to these, long operating time at high temperatures decreases the quality of gelatin.

Deionization of Concentrated Gelatin Solution

The concentrated gelatin solution is sequentially passed through cationic, anionic and mixed bed resin at temperatures between 40 °C and 70 °C, preferrably 61 °C. The salt content of the gelatin solution is decreased to 300-500 ppm at Ph value under its isoelectric point (4.5-6.5 Ph value range is preferred).

Drying Process of Deionized Gelatin Solution

After removing the excess water of the gelatin solution by reverse osmosis and deionization, remaining gelatin concentration is dried on a band conveyor tunnel at temperatures between 20 °C to 50 °C, preferrably 30 °C.