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Properties of gelatin and its application in food industry

Nov. 17. 2022

Edible gelatin has many excellent physical and chemical properties, such as forming reversible gel, cohesiveness, surface activity, etc. In the food industry, it is widely used as peptone agent, emulsifier, stabilizer, binder and clarifier etc., are food additives often used in food production such as cold drinks, jellies, high-grade candies and canned meat.

  The source and characteristics

  of gelatin Gelatin is a protein hydrolyzed from the collagen part of the connective or epidermal tissue of animals. It is a natural protein product containing 18 kinds of amino acids and is easily digested and absorbed by the human body. Therefore, gelatin is a food raw material with high nutritional value.

  Gelatin is a product processed from pigskin, cowhide, etc. The production principle is: the collagen in pigskin and cowhide is converted into gelatin through hydrolysis and other processes. Collagen is the most important protein component in the skin and bone of animals, such as the collagen present in the collagen fibers of the connective tissue of the dermis, which accounts for about 98% of the dry dermis.

  Gelatin is a biological macromolecule with some properties of macromolecules. When dry gelatin is mixed with the right amount of water, the outer layer of gelatin will slowly swell. Over time, swelling occurs towards the inner layer of gelatin, a phenomenon known as "swelling". The expanded gelatin will form a uniform solution with water when heated above 35°C.

  Gelatin solution (accurately, it should be called a mixture of gelatin and water) is in a solid state below 25°C; when it is above 25°C, the gelatin solution will become liquid. If gelatin is decomposed by microorganisms or certain enzymes, it will lose this temperature-accompanied characteristic. Even at 4 degrees Celsius, the gelatin solution will still be liquid.

  Practitioners of food microbiology can use the temperature change characteristics of gelatin solution to detect whether a certain microorganism contains gelatin decomposing enzyme. The detection steps are as follows: 1. Put the microorganisms into the medium containing 12% gelatin, and strictly follow the method of microorganism inoculation. 2. The gelatin solution containing the bacterial species was incubated at 37°C for 24 hours. 3. Put the gelatin solution in a refrigerator at 4°C, keep it warm for 30 minutes, and observe whether the solution is liquid or solid. If the solution is liquid, it indicates that the gelatin has been decomposed, which also means that the microorganism used to test contains gelatinase.

  Gelatin is easy to absorb moisture and should be stored in a dry and cool place; if stored in a humid environment for a long time, gelatin will absorb moisture and agglomerate, affecting the use effect.

  Production method of gelatin There are

  a lot of pigskin and cowhide in China. The production of gelatin from pigskin and cowhide can not only increase the added value of livestock products and the income of farmers and herdsmen, but also provide good raw materials for the food industry. There are four main production processes of gelatin. At present, the gelatin enterprises at home and abroad generally adopt the alkaline production process. The production steps are as follows——

  1. Lime water presoak. Put clean and qualified pigskin or cowhide and other raw materials into about 1% lime water and soak for 1 to 2 days, then cut into small pieces and set aside.

  2. Decontamination. Add the skin and water continuously into the hydraulic degreasing machine, and use the hydraulic impact and the mechanical impact of the high-speed hammer to clean and remove fat and residual dirt.

  3. Soak in lime water. Put the fat-removed skin into the immersion pool and soak it with lime water (specific gravity 1.015-1.035) with a concentration of 2% to 4%. The ratio of wet leather to water is about 1:3 to 1:4, and the pH value is controlled between 12.0 and 12.5. The soaking temperature is preferably controlled at about 15°C, and the soaking time is 15 to 90 days. When the ambient temperature is high, the concentration of lime water can be lower; when the ambient temperature is low, the concentration of lime water can be larger. Soaking skins in lime water is one of the key steps in gelatin production.

  4. Rinse to neutralize. After the skin block swells, remove it, rinse it with water, and finally make the pH value of the skin block 9.0-9.5.

  After rinsing, neutralize the remaining lime with acid, first add water to submerge the skin, and adjust the pH value of the mixture with 6mol/L hydrochloric acid to 2.5-3 while stirring continuously. between 5. Add acid at regular intervals to adjust the pH value. After 8 hours, you can no longer add hydrochloric acid to balance the acid-base.

  After the acid-base balance of the mixed solution, discharge the waste acid water, and wash the skin with water under full stirring. This process is generally completed within 8 to 12 hours.

  5. Boil glue. First add hot water into the glue pot, and then pour the materials in. During this process, the glue blocks will not stick together. At the same time, slowly raise the temperature of the material to 55-65°C, and after soaking for 6-8 hours, release the glue juice; Repeat this operation process again and again, each time the temperature is gradually increased accordingly, and it can be boiled for the last time.

  6. Filter out impurities. Filter the obtained thin glue juice at about 60°C with filter cotton, activated carbon or diatomaceous earth, etc., and filter it with a plate and frame filter press to obtain a clear glue solution. The glue is then separated by a centrifuge to further remove impurities such as grease.



  7. concentrate. Put the thin glue solution into a vacuum concentration tank, control the temperature between 65-70°C, and carry out evaporation and concentration. When the glue becomes thicker, it can be changed to about 60-65°C, and continue to concentrate under reduced pressure. According to the glue quality and drying equipment and other conditions, grasp the concentrated concentration of the glue, such as drying with hot and cold air, the glue is concentrated to a specific gravity of 1.050-1.080 (50°C) and a glue content of 23%. ~33%, the operation of this link can be stopped.

  8. The gel dries. Add a certain amount of hydrogen peroxide, sulfurous acid or paraben to the concentrated glue while it is hot, in order to bleach and preserve the material. Put the thick gel solution into the mold to cool, and after it is completely gelled to form gel peptone, take it out, cut it into thin slices or pieces of appropriate size, dry it with hot and cold air until the gel moisture is 10% to 12%, and then After crushing, it is the finished product. Some companies do not use the glue cutting process, but spray the thick glue solution on the drum dryer, and after drying, they can make granular gelatin products.

  Main technical indicators of edible gelatin:

  (1) Viscosity (oE): first-grade gelatin, ≥12; second-grade gelatin, ≥10; third-grade gelatin, ≥8.

  (2) Freezing power: first-grade gelatin, ≥175; second-grade gelatin, ≥160; third-grade gelatin, ≥115.

  (3) Transparency (mm): first grade gelatin, 100; second grade gelatin, 80; third grade gelatin, 50.

  (4) Moisture: first grade gelatin, ≤14%; second grade gelatin, ≤14%; third grade gelatin, ≤14%.

  (5) Ash content: first grade gelatin, ≤2.0%; second grade gelatin, ≤2.0%; third grade gelatin, ≤2.0%.

  (6) The total number of bacteria: first-grade gelatin, ≤10,000/g; second-grade gelatin, ≤10,000/g; third-grade gelatin, ≤10,000/g.

  (7) Coliform bacteria: first-grade gelatin, ≤150/100g; second-grade gelatin, ≤150/100g; third-grade gelatin, ≤150/100g.

  (8) Salmonella: Salmonella is not allowed to be detected in all kinds of edible gelatin.

  (9) Viscosity drop: first-grade gelatin, ≤20%; second-grade gelatin, ≤20%; third-grade gelatin, ≤25%.

  (10) Insoluble matter: first grade gelatin, ≤0.2%; second grade gelatin, ≤0.2%; third grade gelatin, ≤0.2%.

  (11) Arsenic: first-grade gelatin, ≤1.0 mg/kg; second-grade gelatin, ≤1.0 mg/kg; third-grade gelatin, ≤1.0 mg/kg.

  (12) Heavy metals: first-grade gelatin, ≤50 mg/kg; second-grade gelatin, ≤50 mg/kg; third-grade gelatin, ≤50 mg/kg.

  (13) pH value: The pH value of grade 1, 2 and 3 gelatin is all stipulated between 5.5 and 7.

  (14) Color: yellow translucent, slightly shiny.

  The application range and usage

  of edible gelatin is very wide, and can be used in meat products, meat stuffing, frozen meat, toffee, marshmallow, nougat, toffee, ice cream, yogurt products, beer Clarifying agent, compound emulsion stabilizer, health food, salad, pudding, icing, egg yolk juice, gelatin fudge, pastry, canned meat, ham sausage and other food production.

  In different foods, gelatin is used in different amounts. In meat products, meat stuffing products, frozen meat and other foods, the dosage of gelatin is 2% to 9%; in the production of marshmallows, the dosage of gelatin is 2%; in the production process of toffee, the dosage of gelatin is The dosage is 0.4% to 1.5%; in the production process of ice cream, the dosage of gelatin is 0.1%.



  In the process of using edible gelatin, pay attention to the method of use. When food companies use gelatin, they generally soak the gelatin in cold water for 60 minutes to make it fully absorb water and swell; then, melt the gelatin in a water bath environment below 80°C. When melting, the temperature should not be too high, because the viscosity of gelatin will be reduced if the temperature is too high. When melting gelatin, the principle of "how much to use, how much to soak, and how much to melt" should be adhered to. The gelatin solution should not be left for more than half a day, so as not to affect the quality characteristics such as viscosity, emulsification, and stability. When melting gelatin, the time should not be too long, otherwise, the quality of gelatin will also be reduced.

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