First, fish meal is commonly blended with cottonseed cake, rapeseed cake, urea, and sediment. It's an essential ingredient in animal feed, widely used in the Chinese feed industry to support livestock farming. When selecting high-quality fish meal, it should have a uniform texture with visible fish muscle fibers, scales, bones, and eyes. The color is typically yellow, yellowish-green, or yellowish-brown, and it should feel loose when held in your hand. If it feels sticky, clumpy, or lacks a strong fishy smell, it may be adulterated. Fake products often show inconsistencies in color and shape, with missing fish parts and a weaker odor.
To detect the presence of urea, a simple test can be done: take 20 grams of fish meal and 10 grams of soybean cake, place them in a bottle, add some water, cover it, and heat for 15-20 minutes. If you detect an ammonia-like smell upon opening, it indicates that urea has been added.
Second, bran is often mixed with talcum powder or rice bran. To check, insert your hand into the pile of bran and pull it out. If white residue remains and doesn't easily fall off, it might contain talcum powder. If the bran feels bulgy when held tightly, it could be mixed with rice bran.
Third, soybean meal is frequently adulterated with sediment, crushed corn, or stone powder. A common method to identify this is by soaking 25 grams of the sample in 250 ml of water for 2-3 hours. If sediment is present, it will settle at the bottom, leaving a clear layer of soybean meal on top. Another test involves using iodine: apply a few drops to a small sample on a white dish. If it turns blue-black, it suggests the presence of corn or rice husk.
Fourth, methionine, an essential amino acid, is often diluted with starch, glucose, or stone powder. Genuine methionine appears as pure white or slightly yellow crystals with a sweet taste. Counterfeit versions are usually grayish or dull, lack crystal structure, and emit an odd smell. Burning a small amount of the sample in a porcelain dish at 550°C for an hour should leave minimal residue if it's real. Additionally, dissolving it in water should result in complete dissolution, while fake products tend to remain undissolved.
Fifth, shell powder is often faked with flour or bone, resulting in low calcium content. High-quality shell powder should consist of more than 70% small shells, with at least 30% being large shells after processing. These should contain at least 36% calcium once ground.
Sixth, bone powder is commonly mixed with stone powder, shell powder, or fine sand. Visually, pure bone powder appears as grayish-white granules or powder, sometimes with honeycomb-like structures. Adulterated samples may have fewer or no honeycombs, and the color may appear whiter compared to genuine bone powder. A simple test involves adding dilute hydrochloric acid to the sample. Real bone powder will dissolve, creating a cloudy solution, while fake ones may not react as effectively. Another method is burning a small sample: real bone powder emits steam and a burnt hair smell, whereas fake ones produce less odor and vapor.
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