What are the key points in determining the protein solubility of soybean meal
Key points on determining the protein solubility of soybean meal
Recently, when determining the protein solubility (PS) of soybean meal, why do I find that the results are all on the low side? How do you test it? What matters need attention during the testing process? In addition, how much allowable error is there in the determination of protein solubility?
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Then it must be that the soybean meal itself is not good. Check the reagents - have they expired, is the concentration accurate, and is the amount correct? There seems to be nothing else, and there is also the sampling issue. Maybe the raw material itself is just this low. Have you compared it with other companies or sent it out for testing?
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Can any expert post a testing method for protein solubility?
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I am not an expert, but I can post one for you!
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Method for determining protein solubility in feed
1. Scope of application:
This standard specifies the method for determining protein solubility in feed.
This standard applies to the degree of heat treatment of soybean cake and meal.
2. Referenced standard: Feed quality inspection
3. Principle of the method:
The trypsin inhibitor activity method can be used to determine over-heated soybean cake and meal, but because it is time-consuming and expensive, it is not widely used. Therefore, the chemical indicator of urease activity is now mostly used, but urease activity can only serve as an evaluation indicator for heating to an appropriate degree, and it has no significance for over-heated cake and meal. The urease value cannot reflect the quality of soybean cake and meal subjected to severe heat treatment.
Rinehart discovered a method using 0.2% KOH solution to determine protein solubility to evaluate the quality of soybean cake and meal, which can overcome the shortcomings of the above urease activity evaluation work. Some feed companies in North America and the poultry industry in Brazil have included protein solubility (PS) as one of the quality control indicators. The PS of raw soybean cake and meal can reach 100%, but with prolonged heat treatment time, the PS value decreases. Even with severe over-heating treatment, the PS value does not approach zero. Tests show that protein solubility more closely reflects the relationship between over-heated soybean cake and meal and chicken production performance. It was further proposed that when PS>85%, it is under-heated; PS<70%时,则为过熟。
4. Reagents
0.2% potassium hydroxide (KOH), equivalent to 0.042 mol/L, pH 12.5: weigh about 0.2 g of potassium hydroxide, dissolve it in water, and dilute to 100 ml.
Other reagents are the standard reagents required for Kjeldahl nitrogen determination.
5. Determination steps
5.1 Weigh 1.5 g of soybean cake and meal powder (passed through a 60-mesh sieve) into a 250 ml beaker, add 75 ml of 0.2% KOH solution, and stir on a magnetic stirrer for 20 min.
5.2 After stirring for 20 min, transfer 50 ml of the liquid to a centrifuge tube and centrifuge at 2700 r per min for 10 min.
5.3 Take 15 ml of supernatant and determine the protein content therein by the Kjeldahl nitrogen method; the amount is equivalent to 0.3 g of the original sample.
6. Calculation:
Crude protein in the 0.3 g sample
Protein solubility (%)=——————————————×100
Crude protein content of the original sample
7. Precautions:
7.1 Particle size has an effect on protein solubility. Therefore, when comparing different soybean cake and meal samples, pay attention to their particle size, which should be comparable.
7.2 Pay attention to controlling the stirring time in 0.2% KOH solution so that it is consistent under all circumstances.
7.3 During digestion in the digestion tube, pay attention not to let any liquid be lost, so as not to affect the test results.
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Yes, there is no problem with the determination method. Look for the reason yourself again, and also send it out for testing to see whether there is a problem with the product.
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Look at the color of the sample. I have done it. Generally, Yantai Yihai soybean meal is yellow, and dark brown is rare. The protein solubility is about 78%, and Longkou Xinlong once had 70%.
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Does the preparation of 0.2% KOH solution need to be very accurate?
--------------------------------------
KOH is not a standard solution, so just prepare it by the normal method.
I feel that just looking at the color is basically enough. If the solubility is low, the color should be on the reddish side. In addition, qualitative determination of urease activity can be used for comparison.
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What are the requirements for crushing the sample?
--------------------------------------
Generally, the finer the crushing, the better the extraction effect. You can compare the effect without crushing and after crushing; the difference is large.
I previously did one with very low solubility. Looking for the reason, it should be related to temperature. The second time I did it, it was normal again.
--------------------------------------
It is the temperature during stirring
--------------------------------------
Then it must be that the soybean meal itself is not good. Check the reagents - have they expired, is the concentration accurate, and is the amount correct? There seems to be nothing else, and there is also the sampling issue. Maybe the raw material itself is just this low. Have you compared it with other companies or sent it out for testing?
--------------------------------------
Can any expert post a testing method for protein solubility?
--------------------------------------
I am not an expert, but I can post one for you!
--------------------------------------
Method for determining protein solubility in feed
1. Scope of application:
This standard specifies the method for determining protein solubility in feed.
This standard applies to the degree of heat treatment of soybean cake and meal.
2. Referenced standard: Feed quality inspection
3. Principle of the method:
The trypsin inhibitor activity method can be used to determine over-heated soybean cake and meal, but because it is time-consuming and expensive, it is not widely used. Therefore, the chemical indicator of urease activity is now mostly used, but urease activity can only serve as an evaluation indicator for heating to an appropriate degree, and it has no significance for over-heated cake and meal. The urease value cannot reflect the quality of soybean cake and meal subjected to severe heat treatment.
Rinehart discovered a method using 0.2% KOH solution to determine protein solubility to evaluate the quality of soybean cake and meal, which can overcome the shortcomings of the above urease activity evaluation work. Some feed companies in North America and the poultry industry in Brazil have included protein solubility (PS) as one of the quality control indicators. The PS of raw soybean cake and meal can reach 100%, but with prolonged heat treatment time, the PS value decreases. Even with severe over-heating treatment, the PS value does not approach zero. Tests show that protein solubility more closely reflects the relationship between over-heated soybean cake and meal and chicken production performance. It was further proposed that when PS>85%, it is under-heated; PS<70%时,则为过熟。
4. Reagents
0.2% potassium hydroxide (KOH), equivalent to 0.042 mol/L, pH 12.5: weigh about 0.2 g of potassium hydroxide, dissolve it in water, and dilute to 100 ml.
Other reagents are the standard reagents required for Kjeldahl nitrogen determination.
5. Determination steps
5.1 Weigh 1.5 g of soybean cake and meal powder (passed through a 60-mesh sieve) into a 250 ml beaker, add 75 ml of 0.2% KOH solution, and stir on a magnetic stirrer for 20 min.
5.2 After stirring for 20 min, transfer 50 ml of the liquid to a centrifuge tube and centrifuge at 2700 r per min for 10 min.
5.3 Take 15 ml of supernatant and determine the protein content therein by the Kjeldahl nitrogen method; the amount is equivalent to 0.3 g of the original sample.
6. Calculation:
Crude protein in the 0.3 g sample
Protein solubility (%)=——————————————×100
Crude protein content of the original sample
7. Precautions:
7.1 Particle size has an effect on protein solubility. Therefore, when comparing different soybean cake and meal samples, pay attention to their particle size, which should be comparable.
7.2 Pay attention to controlling the stirring time in 0.2% KOH solution so that it is consistent under all circumstances.
7.3 During digestion in the digestion tube, pay attention not to let any liquid be lost, so as not to affect the test results.
--------------------------------------
Yes, there is no problem with the determination method. Look for the reason yourself again, and also send it out for testing to see whether there is a problem with the product.
--------------------------------------
Look at the color of the sample. I have done it. Generally, Yantai Yihai soybean meal is yellow, and dark brown is rare. The protein solubility is about 78%, and Longkou Xinlong once had 70%.
--------------------------------------
Does the preparation of 0.2% KOH solution need to be very accurate?
--------------------------------------
KOH is not a standard solution, so just prepare it by the normal method.
I feel that just looking at the color is basically enough. If the solubility is low, the color should be on the reddish side. In addition, qualitative determination of urease activity can be used for comparison.
--------------------------------------
What are the requirements for crushing the sample?
--------------------------------------
Generally, the finer the crushing, the better the extraction effect. You can compare the effect without crushing and after crushing; the difference is large.
I previously did one with very low solubility. Looking for the reason, it should be related to temperature. The second time I did it, it was normal again.
--------------------------------------
It is the temperature during stirring