How is fishmeal quality assessed? A few practical identification methods
How to assess fishmeal quality
Generally, fishmeal quality is judged from two aspects. The first step is to identify whether the fishmeal has been adulterated. If it is genuine fishmeal, then proceed to the second step and examine its intrinsic quality.
1. Whether fishmeal has been adulterated can be identified through two methods: physical and chemical.
1. Physical methods: mainly sensory evaluation.
Sight: that is, look at the fineness. High-quality fishmeal is finer, uniform in color, evenly dispersed without clumping, soft when squeezed by hand, and free of impurities; poor-quality fishmeal is coarser, with little or no oiliness.
Smell: that is, smell the odor. Fresh high-quality fishmeal has a pure odor, that is, a pleasant fishy smell with no off-odor; fishmeal that has been stored too long, become damp, spoiled, or deteriorated often has a fishy stench and a pungent musty odor, and if adulterated, it has the smell of the adulterant.
Taste: that is, taste the saltiness. Salt content is one criterion for judging the quality of fishmeal. High-quality fishmeal has low salt content and tastes like fresh fish floss, slightly salty; conversely, if it tastes rather salty, this indicates that the fishmeal is of poor quality.
Burning: that is, the ignition test. Some distributors add inorganic nitrogen urea to fishmeal to pass it off as high-grade fishmeal. The nitrogen in urea is ammoniacal nitrogen, accounting for about 46%, and can be identified by the burning method. The method is: take 20 grams of fishmeal, place it on a clean piece of iron, then heat it with an electric stove or coal stove. When the temperature of the iron reaches about 70 degrees, if the fishmeal gives off a slight pungent ammonia odor, it can be determined to be nitrogen-adulterated fishmeal.
Washing: that is, identification by water washing. Some fishmeal is adulterated with animal and plant proteins and sand, which can be identified by the water washing method. Choose a highly transparent glass cup, put in about 40 grams of fishmeal, then add more than half a cup of water, use a chopstick to stir quickly in one direction, and after stopping stirring, quickly pick up the cup and look through it against sunlight. If there is sand at the bottom of the cup, it proves that sand has been added. Next, wash the fishmeal several times until almost all of the fishmeal has been washed out, then use a pipette to draw out the sediment on the bottom of the cup and place it on a flat glass for careful observation: if there are tiny dark reddish-brown flakes, it proves that cottonseed cake, etc. has been added; if there are tiny flesh-pink particles or filamentous substances, it proves that meat meal or feather meal, etc. has been added.
Microscopic examination: microscopic examination is fast and economical, but depending on the inspector's experience, accuracy varies greatly. To improve the accuracy of microscopic examination, inspectors should conduct extensive observation under the microscope of substances that may be added, memorize their shape characteristics, and conduct intensive training by adding them to fishmeal. Only after long-term, extensive practical operation can the accuracy of microscopic examination be improved.
2. Chemical methods: generally determine items such as protein, fat, calcium and phosphorus, and moisture content. However, with the improvement of adulteration methods, conventional methods may not be able to detect whether adulteration has occurred. At present, the relatively accurate method is to determine the amino acid content in fishmeal, mainly lysine and methionine. Fishmeal with lysine reaching 5% and methionine reaching 2% or more is relatively high quality. After general adulteration, these two indicators are very difficult to meet. But testing amino acids is generally costly and time-consuming, and some places do not have the instruments for testing. In addition, methionine content may vary greatly depending on machinery, equipment, and technical level. Chemical methods can be combined with microscopic examination to carry out specialized chemical determination of substances suspected of being added during microscopic examination. Such as feather meal, blood meal, urea, leather powder, sawdust, stone powder, etc. The testing methods can follow national standards.
2. Although some fishmeal is not adulterated, due to the influence of production raw materials, processing technology, packaging, transportation, and storage, its quality also varies greatly. The key is the freshness of the fishmeal. Especially white fishmeal. Freshness directly affects the amino acid content in fishmeal, the palatability of the feed, and the content of toxic substances. We generally use histamine, volatile basic nitrogen, and acid value as indicators for evaluating the freshness of fishmeal.
1. Histamine. Histamine is a biologically sensitive toxin that has a strong stimulating effect on the digestive tract and can cause gastrointestinal bleeding and erosion, also known as erosive factor. Histamine is a product of microbial decomposition of raw materials before processing. The more severely rotted the fish processed, the higher the histamine content in the resulting fishmeal. Therefore, histamine is an indicator for evaluating the quality of raw materials.
2. Volatile basic nitrogen. A product of amino acid degradation. The higher its content, the more amino acids have been destroyed, especially methionine and tyrosine. Therefore, the nutritional value of fishmeal is greatly affected.
3. Acid value. Acid value evaluates the degree of oxidation of fat in fishmeal. The higher the acid value, the more severe the fat oxidation. The result is that a large amount of unsaturated fatty acids is destroyed, and the nutritional value of fishmeal is reduced; unpleasant odors are produced, affecting feed palatability; and many harmful substances are produced, harming fish. For example, lean-back disease is a fish disease caused by long-term feeding of oxidized oils. High volatile basic nitrogen and acid value are mostly due to changes in fishmeal during processing, packaging, storage, and transportation. Histamine, volatile nitrogen, and acid value all have clear testing methods, so they will not be described further here.
Fishmeal is one of the most important and most costly raw materials in feed, and is also the most likely target for adulteration. Therefore, great effort should be invested in testing fishmeal quality in order to guarantee the quality of the entire finished feed product.
--------------------------------------
Excellent first-class.
Only first-class raw materials can make first-class products.
--------------------------------------
The techniques for adulterating fishmeal are now becoming more and more advanced, and identification is becoming more difficult.
--------------------------------------
These past few days I have been busy with testing issues, and suddenly many unstable factors have increased.
For the problem of fishmeal adulteration, testing one amino acid and microscopic examination can solve the problem.
As for its freshness, it can depend on the company's situation, comprehensively considering histamine, TVBN, acid value, peroxide value, TBA, etc.
In addition, some countries' 2002 hygiene indicators can also be referenced.
In this way, fishmeal will definitely have nowhere to go, and we will firmly grasp it.
There are now too many things to test for a single fishmeal!
We should still evaluate the distributor first.
--------------------------------------
For 'volatile basic nitrogen', could this situation occur: just after entering the warehouse it reaches 130, and after 2 months it instead drops to around 110?
--------------------------------------
No way, it should rise.
--------------------------------------
Learned something, I'll introduce it to customers when I have the chance.
--------------------------------------
--------------------------------------
Volatile basic nitrogen (VBN). VBN mainly occurs in feed with high protein content. In order to obtain energy during growth, microorganisms decompose protein into amino acids, and through deamination convert amino groups into carbonyl groups, which enter the tricarboxylic acid cycle, releasing NH3 while producing energy. VBN is only suitable for detection in the early stage of microbial reproduction in fishmeal, because non-essential amino acids such as aspartic acid are the main source of ammonia in fishmeal. There is a corresponding relationship between the histamine content and VBN content in fishmeal: that is, the higher the histamine, the higher the VBN, and conversely, the lower the histamine, the lower the VBN. The VBN of fresh fishmeal generally does not exceed 110mg/100g.
--------------------------------------
Actually, if you want to buy good fishmeal, the main thing is to find a good supplier, and do not covet a temporary bargain.
Some people in China are really formidable at counterfeiting.
--------------------------------------
Thank you! OP, the information is very detailed, I learned a lot.
--------------------------------------
Very detailed. Shared, thank you!
1. Whether fishmeal has been adulterated can be identified through two methods: physical and chemical.
1. Physical methods: mainly sensory evaluation.
Sight: that is, look at the fineness. High-quality fishmeal is finer, uniform in color, evenly dispersed without clumping, soft when squeezed by hand, and free of impurities; poor-quality fishmeal is coarser, with little or no oiliness.
Smell: that is, smell the odor. Fresh high-quality fishmeal has a pure odor, that is, a pleasant fishy smell with no off-odor; fishmeal that has been stored too long, become damp, spoiled, or deteriorated often has a fishy stench and a pungent musty odor, and if adulterated, it has the smell of the adulterant.
Taste: that is, taste the saltiness. Salt content is one criterion for judging the quality of fishmeal. High-quality fishmeal has low salt content and tastes like fresh fish floss, slightly salty; conversely, if it tastes rather salty, this indicates that the fishmeal is of poor quality.
Burning: that is, the ignition test. Some distributors add inorganic nitrogen urea to fishmeal to pass it off as high-grade fishmeal. The nitrogen in urea is ammoniacal nitrogen, accounting for about 46%, and can be identified by the burning method. The method is: take 20 grams of fishmeal, place it on a clean piece of iron, then heat it with an electric stove or coal stove. When the temperature of the iron reaches about 70 degrees, if the fishmeal gives off a slight pungent ammonia odor, it can be determined to be nitrogen-adulterated fishmeal.
Washing: that is, identification by water washing. Some fishmeal is adulterated with animal and plant proteins and sand, which can be identified by the water washing method. Choose a highly transparent glass cup, put in about 40 grams of fishmeal, then add more than half a cup of water, use a chopstick to stir quickly in one direction, and after stopping stirring, quickly pick up the cup and look through it against sunlight. If there is sand at the bottom of the cup, it proves that sand has been added. Next, wash the fishmeal several times until almost all of the fishmeal has been washed out, then use a pipette to draw out the sediment on the bottom of the cup and place it on a flat glass for careful observation: if there are tiny dark reddish-brown flakes, it proves that cottonseed cake, etc. has been added; if there are tiny flesh-pink particles or filamentous substances, it proves that meat meal or feather meal, etc. has been added.
Microscopic examination: microscopic examination is fast and economical, but depending on the inspector's experience, accuracy varies greatly. To improve the accuracy of microscopic examination, inspectors should conduct extensive observation under the microscope of substances that may be added, memorize their shape characteristics, and conduct intensive training by adding them to fishmeal. Only after long-term, extensive practical operation can the accuracy of microscopic examination be improved.
2. Chemical methods: generally determine items such as protein, fat, calcium and phosphorus, and moisture content. However, with the improvement of adulteration methods, conventional methods may not be able to detect whether adulteration has occurred. At present, the relatively accurate method is to determine the amino acid content in fishmeal, mainly lysine and methionine. Fishmeal with lysine reaching 5% and methionine reaching 2% or more is relatively high quality. After general adulteration, these two indicators are very difficult to meet. But testing amino acids is generally costly and time-consuming, and some places do not have the instruments for testing. In addition, methionine content may vary greatly depending on machinery, equipment, and technical level. Chemical methods can be combined with microscopic examination to carry out specialized chemical determination of substances suspected of being added during microscopic examination. Such as feather meal, blood meal, urea, leather powder, sawdust, stone powder, etc. The testing methods can follow national standards.
2. Although some fishmeal is not adulterated, due to the influence of production raw materials, processing technology, packaging, transportation, and storage, its quality also varies greatly. The key is the freshness of the fishmeal. Especially white fishmeal. Freshness directly affects the amino acid content in fishmeal, the palatability of the feed, and the content of toxic substances. We generally use histamine, volatile basic nitrogen, and acid value as indicators for evaluating the freshness of fishmeal.
1. Histamine. Histamine is a biologically sensitive toxin that has a strong stimulating effect on the digestive tract and can cause gastrointestinal bleeding and erosion, also known as erosive factor. Histamine is a product of microbial decomposition of raw materials before processing. The more severely rotted the fish processed, the higher the histamine content in the resulting fishmeal. Therefore, histamine is an indicator for evaluating the quality of raw materials.
2. Volatile basic nitrogen. A product of amino acid degradation. The higher its content, the more amino acids have been destroyed, especially methionine and tyrosine. Therefore, the nutritional value of fishmeal is greatly affected.
3. Acid value. Acid value evaluates the degree of oxidation of fat in fishmeal. The higher the acid value, the more severe the fat oxidation. The result is that a large amount of unsaturated fatty acids is destroyed, and the nutritional value of fishmeal is reduced; unpleasant odors are produced, affecting feed palatability; and many harmful substances are produced, harming fish. For example, lean-back disease is a fish disease caused by long-term feeding of oxidized oils. High volatile basic nitrogen and acid value are mostly due to changes in fishmeal during processing, packaging, storage, and transportation. Histamine, volatile nitrogen, and acid value all have clear testing methods, so they will not be described further here.
Fishmeal is one of the most important and most costly raw materials in feed, and is also the most likely target for adulteration. Therefore, great effort should be invested in testing fishmeal quality in order to guarantee the quality of the entire finished feed product.
--------------------------------------
Excellent first-class.
Only first-class raw materials can make first-class products.
--------------------------------------
The techniques for adulterating fishmeal are now becoming more and more advanced, and identification is becoming more difficult.
--------------------------------------
These past few days I have been busy with testing issues, and suddenly many unstable factors have increased.
For the problem of fishmeal adulteration, testing one amino acid and microscopic examination can solve the problem.
As for its freshness, it can depend on the company's situation, comprehensively considering histamine, TVBN, acid value, peroxide value, TBA, etc.
In addition, some countries' 2002 hygiene indicators can also be referenced.
In this way, fishmeal will definitely have nowhere to go, and we will firmly grasp it.
There are now too many things to test for a single fishmeal!
We should still evaluate the distributor first.
--------------------------------------
For 'volatile basic nitrogen', could this situation occur: just after entering the warehouse it reaches 130, and after 2 months it instead drops to around 110?
--------------------------------------
No way, it should rise.
--------------------------------------
Learned something, I'll introduce it to customers when I have the chance.
--------------------------------------
For 'volatile basic nitrogen', could this situation occur: just after entering the warehouse it reaches 130, and after 2 months it instead drops to around 110?Generally it is unlikely. VBN gradually rises. Perhaps it is caused by uneven sampling. For the same batch of fishmeal, it is normal to have different indicators.
Dog Dad posted on 2009-3-16 20:20
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Volatile basic nitrogen (VBN). VBN mainly occurs in feed with high protein content. In order to obtain energy during growth, microorganisms decompose protein into amino acids, and through deamination convert amino groups into carbonyl groups, which enter the tricarboxylic acid cycle, releasing NH3 while producing energy. VBN is only suitable for detection in the early stage of microbial reproduction in fishmeal, because non-essential amino acids such as aspartic acid are the main source of ammonia in fishmeal. There is a corresponding relationship between the histamine content and VBN content in fishmeal: that is, the higher the histamine, the higher the VBN, and conversely, the lower the histamine, the lower the VBN. The VBN of fresh fishmeal generally does not exceed 110mg/100g.
--------------------------------------
Actually, if you want to buy good fishmeal, the main thing is to find a good supplier, and do not covet a temporary bargain.
Some people in China are really formidable at counterfeiting.
--------------------------------------
Thank you! OP, the information is very detailed, I learned a lot.
--------------------------------------
Very detailed. Shared, thank you!