How to identify the quality of fishmeal

Generally speaking, the quality of fishmeal is judged from two aspects. The first step is to identify whether fish meal is adulterated or not. If it is real fishmeal, proceed to the second step to examine its inherent quality. First, whether fish meal is adulterated or not can be identified by physical and chemical methods. 1. Physical methods: mainly for sensory identification. Vision: that is, to look at the thickness. High-quality fishmeal is fine and consistent in color, evenly dispersed without caking, hand-pinched soft, without impurities, while inferior fishmeal is coarser, less oily or oil-free. Sense of smell: smell. The smell of fresh high-quality fishmeal is pure, that is, very fragrant fishy smell, no peculiar smell, while too long stored damp spoiled fish meal often has fishy smell and pungent mildew smell, such as adulteration has the smell of adulteration. Taste: the taste is salty and light. Salt content is a standard to judge the quality of fishmeal. High-quality fishmeal has low salt content, fresh fish is loose, slightly salty; on the contrary, if the taste is more salty, it shows that the quality of fishmeal is poor. Burning: that is, burning test. Some distributors mix inorganic nitrogen and urea into fish meal and pass it off as high-grade fish meal. The nitrogen in urea belongs to ammonia nitrogen, accounting for about 46%, which can be identified by burning method. The method is to take 20 grams of fish meal, put it on a clean piece of iron, and then heat it with an electric furnace or coal stove. When the temperature of the iron sheet reaches about 70 degrees, if the fish meal emits a slightly pungent ammonia smell, it can be determined to be nitrogen-mixed fish meal. Washing: that is, washing identification. Some fish meal is mixed with animal and plant protein and sand, which can be identified by washing method. Choose a glass with high transparency, put in about 40 grams of fish meal, then add more than half of the water, stir quickly with a chopstick in one direction, and quickly pick up the cup and look at it in the sun if there is sand at the bottom. Then wash the fishmeal several times, until almost all the fishmeal is washed out, suck out the sediment from the bottom of the cup with a straw and put it on the flat glass for careful observation: if there is a small piece of sauce red, it is proved to be mixed with cottonseed cake, etc.; if there are tiny fleshy red particles or silk, it is proved to be mixed with meat powder or feather powder, etc. Microscopic examination: microscopic examination is fast and economical, but depending on the experience of the examiner, the accuracy varies greatly. In order to improve the accuracy of microscopic examination, inspectors should observe a large number of substances that may be mixed in the mirror, memorize their shape characteristics, and mix them with fish meal for intensive training. After a long time and a large number of practical operations, the accuracy of microscopic examination can be improved. 2. Chemical methods: general determination of protein, fat, calcium and phosphorus, water content and other items. However, with the improvement of adulteration methods, conventional methods may not be able to detect adulteration. At present, the more accurate method is to determine the content of amino acids in fish meal, mainly lysine and methionine. When lysine reaches 5% and methionine reaches more than 2%, it is relatively high quality fishmeal. In general, these two indicators are difficult to meet after adulteration. However, the detection of amino acids is generally expensive and takes a long time, and some places do not have the equipment for detection. In addition, methionine content may vary greatly with the level of machinery, equipment and technology. Chemical methods can cooperate with microscopic examination to carry out special chemical determination of substances suspected to be adulterated in microscopic examination. Such as feather powder, blood powder, urea, leather powder, sawdust, stone powder and so on. The detection method can be in accordance with the national standard. Second, although some fishmeal is not adulterated, its quality varies greatly due to the influence of production raw materials, processing technology, packaging, transportation and storage, and the key is the freshness of fishmeal. Especially white fish meal. Freshness directly affects the content of amino acids in fish meal, the palatability of feed and the content of toxic substances. Histamine, volatile base nitrogen and acid value are generally used as indicators to evaluate the freshness of fishmeal. 1, histamine histamine is a biological sensitive toxin, has a strong stimulating effect on the digestive tract, can cause gastrointestinal bleeding, erosion, also known as erosion. Histamine is the product that the raw material is decomposed by microorganisms before processing. the more serious the decay, the higher the content of histamine in fish meal. Therefore, histamine is an index to evaluate the quality of raw materials. 2. The degradation products of volatile base nitrogen amino acids. The higher its content, the more amino acids are destroyed, especially methionine and tyrosine. Therefore, the nutritional value of fishmeal is greatly affected. 3. Acid value is to evaluate the oxidation degree of fat in fishmeal. The higher the acid value, the more serious the fat oxidation. The result is that a large number of unsaturated fatty acids are destroyed, the nutritional value of fishmeal is reduced, unpleasant smell is produced, which affects the palatability of feed, and many harmful substances are produced, which harm fish, such as lean back disease, which is caused by long-term feeding of oxidized oil. The high volatile base nitrogen and acid value are mainly due to the changes of fishmeal in the processing, packaging, storage and transportation stages. Histamine, volatile nitrogen and acid value all have clear detection methods, so I will not repeat them here. Fishmeal is one of the most important and expensive raw materials in feed, and it is also the most easily adulterated object, so great efforts should be made to detect the quality of fishmeal in order to ensure the quality of the whole feed product. -- A top of excellence. First-class raw materials can make first-class products.-- now the technology of fishmeal counterfeiting is getting higher and higher, and it's more difficult to identify-- I've been busy testing problems these days. All of a sudden, a lot of unstable factors have been added. Fishmeal adulteration problem, testing an amino acid and microscopic examination can solve the problem. As for his freshness, we can comprehensively consider histamine, TVBN, acid value, peroxide value, TBA and so on. In addition, we can refer to the 2002 health indicators of some countries, so fishmeal must have no way to go, let us firmly grasp. Now there are too many things to test for a fishmeal! We should still evaluate the dealer for the best. -- is there such a situation as' volatile base nitrogen': when it first entered the warehouse, it reached 130 minutes and dropped to about 110 two months later? -- No way, it should go up.-- study. Have the opportunity to introduce to the customer-- is there such a situation as' volatile base nitrogen': when it first entered the warehouse, it dropped to about 110 after two months? Dog Dad published in 2009-3-16 20:20 is generally unlikely, VBN is gradually increased, perhaps caused by uneven sampling, the same batch of fishmeal, it is normal to have different indicators. -- volatile salt ground state nitrogen (VBN) VBN mainly occurs in feeds with high protein content. In order to obtain energy, microorganisms decompose protein into amino acids during growth. After deamination, amino groups are transformed into carbonyl groups into tricarboxylic cycle, energy is generated and NH3 is released at the same time. VBN is only suitable for the detection 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 histamine content and VBN content in fishmeal, that is, the higher the tissue ammonia, the higher the VBN, on the contrary, the lower the tissue ammonia, the lower the VBN. The VBN of fresh fish meal generally does not exceed 110mg/100g. In fact, the main way to buy good fishmeal is to find a good supplier. Don't be greedy for temporary bargains. Some capable people in China are really good at counterfeiting. Thank you! Landlord, the information is very detailed, learned-- very detailed. Shared, thank you!