Most of the gelatin hollow capsules produced in China are made from raw materials such as cowhide and bovine bone. Here is a process for extracting gelatin from chicken skin:
Pretreatment of chicken skins Fresh frozen chicken skins were cut into 1 cm × 1 cm pieces, and the same concentration of 3.5% hydrochloric acid as the chicken skin was added. The soaking temperature was 15°C to 18°C, and the same time every 6 hours to 8 hours. The concentration of hydrochloric acid solution was changed every 3 days after replacement for 3 times, and the pickling time was 4 days. The chicken skin after pickling becomes white in color, expands in volume and has higher elasticity.
Hydraulic degreasing Chicken skins after acid treatment were rinsed with cold water in a hydraulic degreasing machine to remove most of the hydrochloric acid and fat from the chicken skin until the pH of the chicken skin was 4.5-4.7. At this time, the skin of the chicken is translucent and the structure of the chicken skin can be clearly seen.
Remove the glue Add distilled water of the same volume as the chicken skin to the cleaned chicken skin and put it in a water bath to extract the gum. The first glue gluing temperature is 55°C and the time is 2.5 hours to 3 hours. When the specific gravity of the glue is 1.025, the glue can be put. Distilled water was added to the degummed chicken skin for the next gum extraction. The temperature of the next gluing is 5°C~10°C higher than the previous one, and the time can be extended by half an hour. Note that the gluing temperature should not exceed 80 °C, otherwise the gelatin's viscosity and gel strength will be greatly reduced.
Dividing the grease After removing the grease, the chicken skin after degreasing still has a small amount of oil after cooking. This part of the oil not only reduces the transparency of the glue, but also affects the important qualities such as gelatin viscosity and gel strength and must be removed. The grease is removed by mixing each lane of glue in a water bath at 55° C. and allowing it to stand for several hours. The upper grease is removed by liquid separation using the difference in specific gravity between the glue and the grease.
Concentration and drying of the glue The glue was concentrated in a rotary evaporator to a moisture content of 45% and then dried in a vacuum freezer until the moisture content was below 16%. If using other methods of concentration and drying, the temperature should not exceed 75 °C, otherwise the gel strength will be greatly reduced.
The gelatin film crushes the dried gelatine into a desired thickness to obtain the finished gelatin. In particular, the use of chicken skin as raw material, gelatin prepared by the acid process does not require bleaching, pale color, no odor, and the viscosity is much higher than commercially available gelatin. Therefore, raw material of chicken skin will be a good resource for future gelatin companies to invest in industrial production.
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