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Protein is one of the three essential elements of human beings and it is an indispensable material for sustaining life. The human body cannot synthesize proteins that can only be ingested from various foods. Therefore, the determination of crude protein content in foods is performed to evaluate the nutritional value of foods, so as to make rational use of food resources, arrange diets scientifically and reasonably, and improve people's physical fitness. The determination of protein content in foods is generally performed by the Kjeldahl method.
In general, the nitrogen content of protein in foods is about 15-19%, of which the nitrogen content of protein in wheat is high, about 1715%, while the nitrogen content of protein in other grains and beans is about About 16%, according to this percentage of nitrogen, by measuring the nitrogen content in food can be converted to the percentage of protein content. The Kjeldahl method is based on measuring the content of nitrogen in a sample and converting it into protein content.
The determination process of this method requires the digester to digest the sample. Digestion of the sample is an important factor influencing the determination of crude protein. Because there are few samples during digestion, the temperature is high, the reaction is fierce, and the digestion conditions are not good enough. It is also likely to cause increased digestion time, incomplete digestion, or loss of some of the nitrogen in the sample. With the author's many years of practical experience, samples should pay attention to the following aspects when digesting: 1 The addition of copper sulfate and potassium sulfate in the sample is to increase the reaction temperature and accelerate the reaction rate, but the added potassium sulfate can not be too much, because potassium sulfate Too much of the added amount can cause the boiling point of the digestive fluid to be too high, which can make the temperature of the digestive fluid too high. At an excessively high temperature, sulfuric acid forms small droplets to carry the sample and is distilled out, resulting in the loss of nitrogen. Low.
Digestion furnaces must be strictly controlled when they begin to digest. They can only do the heating at a lower temperature, but they should not be too high. It is better to use adjustable furnaces or to add more layers of asbestos mesh on the electric furnace to avoid overheating. Because when digestion was started, the digestion was fierce, the foam was relatively high, the temperature was high, the digestion was too intense boiling, and the sample was easily splashed with the liquid, or the foam was spilled over the flask, causing the loss of the sample, especially the high fat content. The sample, the sample in the heating can easily produce a lot of foam and overflow. When the digestion is too fast, it may cause side reactions, which may cause some of the nitrogen to be oxidized to become volatile in the molecular state and cause the result to be low; when the digestion is too intense, the foam will splash the sample on the bottle wall and the bottleneck. , High-temperature coking is not easy to elute, especially splashed at the bottleneck, it is more difficult to elute down, it is also likely to cause late digestion difficulties and incomplete digestion, resulting in low results. Therefore, when digesting, it is generally necessary to slightly heat (10~20) minutes, the foam is reduced, most of the digestive fluid is grayish black, and sulfur dioxide and white smoke increase, the temperature can be increased, so that the solution remains in a micro-boiling state, because There are many carbonized particles formed by the sample in the digestive juice.
Although the early digestion time is longer, less carbonized particles are formed, which can greatly reduce the time of the later digestion and complete digestion. In the digester's late stage of digestion, the black coking material splashed on the wall of the flask must be turned to shake off the flask to avoid sample loss. In the digestion process, if the consumption of sulfuric acid, hydrogen peroxide water mixture is large, it should be added as appropriate to continue to digest part of the mixture to avoid the flask dry, the temperature is too high, resulting in overheat decomposition of ammonium sulfate, resulting in loss of ammonia.
Therefore, when digesting the sample with the digestion furnace, it is necessary to pay close attention to it, control the digestion temperature, ensure the accuracy of the sample digestion, and ensure an accurate sample for the determination of the protein content, so as to ensure that the measured result can be accurately and accurately , to provide accurate scientific evidence for the test.
In general, the nitrogen content of protein in foods is about 15-19%, of which the nitrogen content of protein in wheat is high, about 1715%, while the nitrogen content of protein in other grains and beans is about About 16%, according to this percentage of nitrogen, by measuring the nitrogen content in food can be converted to the percentage of protein content. The Kjeldahl method is based on measuring the content of nitrogen in a sample and converting it into protein content.
The determination process of this method requires the digester to digest the sample. Digestion of the sample is an important factor influencing the determination of crude protein. Because there are few samples during digestion, the temperature is high, the reaction is fierce, and the digestion conditions are not good enough. It is also likely to cause increased digestion time, incomplete digestion, or loss of some of the nitrogen in the sample. With the author's many years of practical experience, samples should pay attention to the following aspects when digesting: 1 The addition of copper sulfate and potassium sulfate in the sample is to increase the reaction temperature and accelerate the reaction rate, but the added potassium sulfate can not be too much, because potassium sulfate Too much of the added amount can cause the boiling point of the digestive fluid to be too high, which can make the temperature of the digestive fluid too high. At an excessively high temperature, sulfuric acid forms small droplets to carry the sample and is distilled out, resulting in the loss of nitrogen. Low.
Digestion furnaces must be strictly controlled when they begin to digest. They can only do the heating at a lower temperature, but they should not be too high. It is better to use adjustable furnaces or to add more layers of asbestos mesh on the electric furnace to avoid overheating. Because when digestion was started, the digestion was fierce, the foam was relatively high, the temperature was high, the digestion was too intense boiling, and the sample was easily splashed with the liquid, or the foam was spilled over the flask, causing the loss of the sample, especially the high fat content. The sample, the sample in the heating can easily produce a lot of foam and overflow. When the digestion is too fast, it may cause side reactions, which may cause some of the nitrogen to be oxidized to become volatile in the molecular state and cause the result to be low; when the digestion is too intense, the foam will splash the sample on the bottle wall and the bottleneck. , High-temperature coking is not easy to elute, especially splashed at the bottleneck, it is more difficult to elute down, it is also likely to cause late digestion difficulties and incomplete digestion, resulting in low results. Therefore, when digesting, it is generally necessary to slightly heat (10~20) minutes, the foam is reduced, most of the digestive fluid is grayish black, and sulfur dioxide and white smoke increase, the temperature can be increased, so that the solution remains in a micro-boiling state, because There are many carbonized particles formed by the sample in the digestive juice.
Although the early digestion time is longer, less carbonized particles are formed, which can greatly reduce the time of the later digestion and complete digestion. In the digester's late stage of digestion, the black coking material splashed on the wall of the flask must be turned to shake off the flask to avoid sample loss. In the digestion process, if the consumption of sulfuric acid, hydrogen peroxide water mixture is large, it should be added as appropriate to continue to digest part of the mixture to avoid the flask dry, the temperature is too high, resulting in overheat decomposition of ammonium sulfate, resulting in loss of ammonia.
Therefore, when digesting the sample with the digestion furnace, it is necessary to pay close attention to it, control the digestion temperature, ensure the accuracy of the sample digestion, and ensure an accurate sample for the determination of the protein content, so as to ensure that the measured result can be accurately and accurately , to provide accurate scientific evidence for the test.
it is the Cylinder in an engine where the combustion takes place-..in bikes the cylinder is just above the transmission. think of it as a syringe. the piston moves up and compresses the air fuel mixture and as a result combustion takes place. the piston is then pushed down. this up and down motion of the piston rotates the crankshaft which is connected to the transmission which transmits power to the wheels. there are various configurations of cylinders in an engine. in bikes you have single cylinder, parallel twin, v twin, L twin, inline 4, inline 3, inline 6, v4, flat twin. similarly in cars you get inline 3, inline4, inline6 , v6, v8, v10, w12. the number represents the no. of cylinders and the letter or prefix represents the configuration.
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