Gelatin is obtained by purifying the collagen of the animal skin, bone, tendon and ligament after incomplete acid hydrolysis, alkaline hydrolysis or enzymatic degradation.
Character
This product is sheet or powder of which the color is from lightly yellowish to yellow, transparent or translucent, slightly lustrous; odorless; It swells and softens when it is immersed in water and can absorb water which is 5-10 times as weigh as its own mass.
This product is freely soluble in hot water, soluble in hot mixture of water and acetic acid or glycerin, and insoluble in ethanol.
Identification
Take the 0.5g of the product, add 50 ml of water, heat to make the product dissolve in the water. Then take 5ml of the solution, add a few drops of the mixture of Potassium dichromate test solution and dilute hydrochloric acid (4:1), then orange-yellow flocculent precipitate is produced.
Take 1ml of the remaining solution, add 100ml of water, shake well, add a few drops of the citrate test solution, and turbidity occurred.
Take about 0.3g of the product, put it in a test tube, add a little sodium lime, heat it, and the generated gas can make the wet red litmus paper blue.
Freezing strength
Take two test samples, 7.50g each, and put them in the frozen bottles respectively. Add water to make for the glue of 6.67%, cover it and put them aside for 1-4 hours. After that, heat and stir the mixture in the water bath of 65 ° C ± 2 ° C for 15 minutes to make the tested sample evenly. After putting them under room temperature for 15 minutes, place the frozen bottle horizontally in a constant temperature water bath at 10 °C ± 0.1 °C for 17 hours ± 1 hour, sealed by a rubber. Then quickly remove the frozen bottle, dry the outer wall, and put the frozen bottle on the test bench, calculate the average of the two results, the freezing strength should not be lower than 180Bloom g.
PH
Take the product of 1.0g, add hot water of 100ml, shake to make it dissolve, then make the solution cool to 35 ° C, the PH should be 4.0~7.2.
Transmittance
Take the product of 2.0g, add water of 50 ~ 60 ° C to dissolve and make for the glue of 6.67%, then cool the glue to 45 ° C. According to the ultraviolet-visible spectrophotometry, the light transmittances shall not be lower 50% and 70%, when it is measured at wavelengths of 450 nm and 620 nm.
Conductivity
Take 1.0g of the product, add water of which the temperature is lower than 60 °C to dissolve and make a solution of 1.0%, as the test solution and take the water of 100ml as a blank solution. Place the test solution and the blank solution in a water bath at 30 ° C ± 1 ° C for 1 hour, then test the conductivity with a conductivity meter, using the platinum black electrode as the measuring electrode. Swash the electrode with a blank solution for 3 times, for the conductivity of the blank solution, and it should not exceed 5.0 μs/cm. Then take out the electrode and swash the electrode with a test solution for 3 times, the conductivity of the test solution shall not exceed 0.5 ms/cm.
Sulfite (calculated as SO2)
Take 1.0g of the product, place it in a long neck round bottom flask, add 150ml of water, leave it for 1 hour, then heat it in a water bath at 60 °C for dissolution. Add 5ml of phosphoric acid and 1g of sodium bicarbonate, and connect the condenser immediately. (When an excessive amount of foam is generated, add some defoaming agent such as silicone oil). heat and distill the solution. Then use 15 ml iodine solution of 0.05mol/L as the receiving liquid to collect 50 ml of distillate. Dilute the solution to 100ml with water, shake well. Take out 50ml, and evaporate it in a water bath. Add some water at any time until the solution is almost colorless. Dilute the solution to 40ml with water and check it according to the sulfate test method, if it is turbid, If it is turbid, it should not be more concentrated (0.01%) than the control solution made of 7.5 ml of standard potassium sulfate solution.
Peroxide
Take 10g of the product, place it in a 250ml stoppered flask, add 140ml of water, leave it for 2 hours, and heat it in a water bath at 50 °C. to dissolve quickly, then immediately cool the solution down. Add sulfuric acid solution (1 → 5) of 6ml, potassium iodide of 0.2g, 1% starch solution of 2ml and 0.5% ammonium molybdate solution of 1ml. Seal, and shake well, place in a dark place for 10 minutes, the solution should not be blue.
Loss on drying
Take this product and dry it at 105 °C for 15 hours. The weight loss should not exceed 15.0%.
Viscosity
Instruments and reagents: Pinkler viscometer tube: φ2.0mm, Water bath: adjustable temperature 60 ° C ± 1 ° C, Constant temperature incubator: adjustable temperature 60 ° C ± 1 ° C, Beaker: 150ml, Erlenmeyer flask: 150 ml, Constant temperature water bath: adjustable temperature 40.0 ° C ± 0.1 ° C, Stopwatch: Indexing 0.2 seconds.
Testing steps
Take 15.0g sample into a 150ml sterilized beaker of which the weight is known weight. Add about 70ml of cooled sterilized water, swell for 2~3h at room temperature. Then put the beaker in a water bath of 60°C±1°C for dissolution. Take out the solution out to make for the glue of 15% of [(100-moisture) × 15.0/15] g. Filter the glue through a sterile screen of 80 mesh, into a 150 ml sterilized flask. Invert the capillary viscometer to absorb the solution as required, and then turn over the viscosity meter quickly, and wipe off the solution adhered to the outside of the tube. Vertically fix the capillary viscometer into a constant temperature water bath, and the liquid level of the water bath should be higher than the middle of the measuring ball, and then leave them for 15 minutes, and the solution is taken up beyond the measuring ball scale line to make the solution naturally falls inside the tube. With a stopwatch, record the outflow time that the liquid level drop from the measurement line 1 to the measurement line 2. Repeat above steps for 3 times or more, and the difference between each measured value and the average value shall not exceed ±0.25% of the average value. Record the kinematic viscosity A1 and calculate: A1(mm2/s) = Kt
In the formula:
K - the coefficient of the Pinkler viscometer, mm2/s2;
T - glue outflow time, s;
The difference between the parallel testing results is not more than 2 mm2/s, and the arithmetic mean is taken as the report result. The viscosity is not less than 70 mm2/s.
Viscosity dropping
Weigh the Erlenmeyer flask and remaining glue of 3.8.2. Stuff the bottle opening with the sterile cotton, culture in an incubator at 60 °C ± 1 °C for 17h ± 1h, then take out and weigh. Make up the lost water, and test the kinematic viscosity A2. Calculate viscosity dropping: Viscosity dropping (%) = (A1-A2) / A1 × 100%
In the formula:
A1 - original viscosity of the sample, mm2/s;
A2 - viscosity after 17h incubation at a constant temperature, mm2/s.
The difference between parallel testing results should be less than 3%, and the arithmetic mean is taken as the report result. The viscosity shall not be reduced by more than 24%.
Ignition residue
Take the test sample 1.0~2.0g, place it in the crucible that has been burned to constant weight, slowly burn the sample until it is completely carbonize, then cool it down; unless otherwise specified, add 0.5~1ml of sulfuric acid to make it moist, and heat it with low temperature to remove all the sulfuric acid vapor, and then make it completely ashed at 700-800 °C. After that, move it to a desiccator, and make it cool down. After precise weighing, burn at 700~800 °C until the weight is constant. The ignition residue shall not exceed 2.0%.
Chromium
Take 0.5g of the product, and put it in the tetrafluoroethylene disintegration tank, add 5~10ml of nitric acid, mix well, and pre-dissolve for 2 hours at 100°C. Cover the inner lid, tighten the outer cover, and place it in a suitable microwave digestion furnace for disintegration. After the disintegration is completed, place the inner disintegration tank on the electric heating plate to heat slowly until reddish brown steam are all removed. Transfer it to a 50ml Teflon bottle with 2% nitric acid, and dilute it with water until the liquid level reach the scale, and then shake well, then it comes out the test solution. Make blank solution with the same method. Then, take the chrome element standard solution and dilute it with 2% nitric acid to make Chromium standard stock solution of which there is 1.0μg of chromium standard stock solution per 1ml of solution.
When using, accurately measure for an appropriate amount, and make reference solution containing 0~80 ng of chromium per 1 ml, with 2% nitric acid solution. was made into a reference solution containing 0 to 80 ng of chromium per 1 ml. Take test solution and reference solution, use graphite furnace as an atomizer, and test according to atomic absorption spectrometry or inductively coupled plasma mass spectrometry. The Chromium should not exceed two parts per million.
Heavy metals
Take the remaining residue of Ignition residue, test the heavy metal content, the value shall not exceed 30 parts per million.
Arsenic salt
Take the product of 2.0g, add starch of 0.5g and calcium hydroxide of 1.0g, add a small amount of water, stir evenly. After drying, carbonize the solution with a small fire, and then burn at 500 ~ 600 °C to make it ash completely. Cool it down, add 8 ml of hydrochloric acid and 20 ml of water, and test according to the Eguer's method or the silver diethyldithiocarbamate method, and the value should be 0.0001%.
Microbial limits
The total amount of aerobic bacteria in each 1g of test sample should not exceed 1000cfu, the total amount of mold and yeast should not exceed 100cfu, Escherichia coli should not be detected; Salmonella should not be detected in every 10g test sample.
Storage
Protect from light and keep it sealed.
