Gelatin

Description

Brief Overview

Gelatin is a mixture of peptide and protein substance derived from collagen, a natural protein present in the tendons, ligaments, and tissues of mammals. Gelatin is able to from strong and transparent gels which is capable of forming a positive binding action in the food processing applications. Gelatin forms a viscous solution when dissolved in hot water and is soluble in most of the polar solvents.

Manufacturing Process

There are mainly three methods to produce gelatin -  the lime cream method, hydrochloric acid method and enzymatic method.

1. Lime Cream Method

Inner layer of grease of a degenerated foot skin of cowhide and pigskin is cut into small pieces and soaked in 3.5%-4.0% lime cream for about 30-40 days. The soaked raw hides are then washed with water and neutralized with 10% hydrochloric acid for 3-4h under stirring. The pork skin is then added into water in a 1:1 ratio and cooked at 60-70℃. The glue water is extracted at regular intervals and filtered with clean gauze while hot. This process is repeated for 5-6 times. The thin glue water is concentrated to a relative density of 1.03-1.07gcm^-3. The hot glue is then cooled and dried. The dried film is crushed to obtain the gelatin with a yield of about 22% by weight.

2. Hydrochloric Acid Method

Miscellaneous bone, spine and small bone are crushed, and benzene is used to extract the oil in 45-50°C before washing with water. The washed bone is soaked in 3.5-4.0% hydrochloric acid for softening. The crude ossein obtained is washed with water to obtain a pH of around 3.5. It is further soaked in 3.0%-3.5% lime cream for 30-50 days. The ossein is cleaned and neutralized with hydrochloric acid to obtain a pH of 3.5-4.0. The ossein is then cleaned and washed with water before de-gelatinization to obtain the glue. The thin glue water obtained is then filtered and concentrated to a density of 1.025-1.075gcm^-3. It is then frozen, sliced and dried to yield gelatin.

3. Enzymatic Method

Protease is used to hydrolyze the collagen into gelatin. Dilute hydrochloric acid is added to dissolve it. Acetone, sodium sulfate and sodium chloride is then used to precipitate out the gelatin. This method is not yet mature with the current production shortening the soaking time. The raw material is washed with NaOH solution (pH = 11~12) for 24 hours, then subjected to enzymatic hydrolysis with alkaline protease at 40 ℃ for 6 h. After water washing, it is soaked and washed with acid. The finished skin raw material is soaked in 1% lime water for 1-2h, cut into pieces and dewatered to obtain the degreased broken skin. The degreased broken skin is soaked with 2%-4% lime water with the ratio of wet skin and water of 1:3-1:4 and pH of 12-12.5 at 15 ℃ for 15-90 days. Neutralization, followed by concentration of the product, would form gelatin.