Cod liver oil processing technology

The liver of a shark is larger than that of other fish. The liver of most fishes only accounts for about 1-3% of the body weight, and the shark's liver accounts for about 10-15% of body weight. The oil content of shark liver is also very high. Generally, the liver oil content of fish is about 3-20%, while shark liver oil content is about 30-70%. Cod liver oil is rich in vitamins A and D. Vitamin A has the function of preventing night blindness and promoting the growth and development of animals. Vitamin D has the function of preventing rickets. The substance containing these two vitamins in nature is the most common one. So far, in addition to artificial synthesis, cod liver oil is the main source of vitamins A and D. Shark liver is a good raw material for the production of cod liver oil fish liver oil pills, wheat essence cod liver oil and milk white cod liver oil. When processing canned fish for the frying process, shark liver oil is used instead of or in combination with vegetable oils. The effect is very satisfactory. In the family life, shark liver oil is also good for frying fish and certain foods. Fats and oils exist in the liver in two forms, one is in the free state in the cells, and the other is combined with proteins to form the cell protoplasm. Therefore, in liver oil production, in order to fully lick the vitamin oil in the raw materials, it is necessary to design the connection between the oil and the protein. If the liver tissue is not hydrolyzed or extracted with a strong solvent, it is not easy to extract all the vitamin oils. come out. 1. The preservation of fresh fish liver raw materials is a prerequisite for obtaining good finished products. In order to maintain a high freshness of fish liver, liver must be dissected and processed properly. If it cannot be processed at the time, it must be properly stored. The commonly used methods are frozen and salted. The freezing method can be performed according to the method of fish freezing. The method of salt collection is not limited by conditions, and its application is more common. The specific operation method is as follows: When the shark is dissected, remove the liver, remove the gallbladder, cut into large pieces with a knife, and put it in clean water. Gently squeeze in both hands. Press the liver block, discharge the bloody blood in the liver, then remove it, cut it into 3cm squares with a knife, mix 10-15% salt, seal in the cylinder or barrel, and put it in the shade. 2. Slightly alkaline hydrolysis method to prepare cod liver oil by light lye in the case of heating, so that the fish liver protein cell decomposition, thereby separating the method of cod liver oil, said light alkali hydrolysis. This method is used mostly in the production of cod liver oil at home and abroad. The reason why the alkali hydrolysis method is widely used is that it decomposes the liver fast, the production of cod liver oil and vitamins is high, the finished cod liver oil is of good color, and the acid price is low. Although alkali oil can saponify part of the oil, it makes the extracted cod liver oil vitamins. The concentration increases. The process of the alkali hydrolysis method: raw material→inspection→shredding→alkali decomposition→first centrifugation→saline wash→second centrifugation→crude liver oil→cooling→pressure filtration→clean fish liver oil. (1) Inspection and shredding: The fish liver must be placed on an inspection table before being shredded to remove the fish liver (such as a corrupt fish liver) and other inclusions that are not suitable for oil extraction. Frozen fish liver should be thawed ahead of schedule. Salty fish liver should be washed beforehand to remove some salt. The purpose of chopping the fish liver is to make it fully contact with the alkaline solution to achieve effective decomposition, and at the same time, the partial cod liver oil can be separated out first. Chopped meat generally uses a special liver machine. (2) Hydrolysis of fish liver: After the disruption of the cell membrane of the fish liver by ordinary methods, only the oil in the free state is separated, and for those oils that combine with the protein to form the cell's protoplasm, it is necessary to try to This association destroys the protein after it is hydrolyzed. The purpose of protein separation can be achieved by co-cooking with alkali and fish liver. Because alkali is easy to saponify oils and has a destructive effect on vitamins, light alkali can only be used. When the fish liver is cooked in lye, the alkali neutralizes the free fatty acids in the liver oil, and there is also a decoloring effect on the oil, so the method of light alkali hydrolysis is used, and the effect of deacidification and decolorization is obtained at the same time. The hydrolysis process is the main process of this method, and the conditions are more complicated. Now it is divided into the following: 1 The amount of alkali: The amount of alkali used to hydrolyze the fish liver varies depending on the type, freshness, and salt content of the fish liver. In general, the amount of alkali required to maintain the PH 9-10 during heating hydrolysis (fresh liver control at pH 9 and salt liver control at PH 10). Because of the decomposition of fish liver, this is the most appropriate PH value. Normal fresh shark livers use caustic soda shark liver 0.3%, shark liver 0.8-1.5%; salt shark liver caustic soda amount: 0.4-0.8% shark liver, 1.8-3.3% shark liver . 2 Alkaline solution concentration: The base used must be added as a solution. The lye concentration also varies depending on the type of fish liver. Generally, shark livers have a lye concentration of 1.5-2.0%, shark liver 3-5%, and large yellow croaker liver and cod liver about 10%. 3 The amount of water added: The amount of water when the fish liver is hydrolyzed has a great influence. When the amount of water is insufficient, the protein hydrolysis is slow and uneven, and the oil is easily hydrolyzed. When the amount of water is too high, it will dilute the lye, in order to maintain the concentration required by the alkali. The consumption of alkali is bound to increase, and the ratio of liver and water is generally about 1:1. 4 Hydrolysis temperature and time: In the hydrolysis process, heating can promote the decomposition rate of the protein, and in the hot state, the viscosity of the oil is low, easy to separate, and the lipase and odor contained in the liver can also be heated. When destroyed and repelled. The hydrolysis temperature can not be too high, generally controlled at 80-90 °C, the temperature is high, it will promote a lot of grease saponification and vitamin destruction, in addition, the protein is solidified more closely, it is necessary to consume more alkali, and prolong the hydrolysis time . Not only that, but also in the high temperature, suddenly contact with the base of the oil, it will have to produce a lot of soap, increase the consumption of liver oil, and the formation of emulsion, it is difficult to separate liver oil. Therefore, in the production of secondary temperature system, first heated to about 50 °C, then add alkali, and finally increase the temperature to 80-90 °C. The addition of lye should be divided into two, so as to prevent the saponification of a large number of alkalis and oils and to make the pH of the solution exceed the required range due to excessive alkali addition. The addition of the lye should be divided into two times so as to prevent the saponification of a large amount of alkalis and oils and to make the pH of the solution exceed the required range due to too much alkali addition at one time. The time for hydrolyzation of fish liver differs depending on the type of liver, usually 1-1.5 hours, and it sometimes takes 2-3 hours for the less-diet fatty liver. Hydrolysis pan generally uses a sandwich stainless steel pan. (3) Separation and washing of liver oil: The liquid juice that comes out of the hydrolysis kettle is mainly composed of oil, aqueous solution and liver residue. During centrifugation, the specific gravity of the liver residue is divided into three layers. The heavier liver residue is attached to the inner wall of the centrifuge at the outermost layer. The oil is in the innermost layer while the aqueous solution is in the middle layer. The oil and the aqueous solution are continuously Separately from the catheter, and liver residue needs to be removed by washing. Heating is required before centrifugation, but the temperature should not be too high, generally not exceeding 90°C. When it was found that the emulsion of the hydrolyzate was not capable of separating the oil, salt water could be added to achieve the purpose of separation. The liver oil that was isolated for the first time still contains some water, liver residue, soap, and other impurities, and therefore it is quite turbid. It needs to be washed with salt water 2-3 times. The salt damages the latex, salting out the soap, and also increases the specific gravity of the aqueous solution. Adding water can wash the alkali and liver residue in the oil. The first wash was done with 5% saline, the ratio of brine to oil was 1:1, and the water temperature was about 80°C. For the second wash, the brine can be concentrated to 5-10%, and the amount of brine is 1/2 of the oil. Temperature 80 °C. The number of washes depends on the quality of the cod liver oil, and a third wash may be performed if necessary. Liver oil after the proposed liver residue, can be used to make liver residue, soy sauce, amino acids and other hydrolyzed products, but also can be used directly as feed or fertilizer. (4) Low-temperature treatment of cod liver oil: This is an important purification step, which is the cryogenic treatment of cod liver oil (de- stearin). As the cod liver oil is stored during the storage period and reaches a low temperature season, some of the oil contained in the higher freezing point will crystallize, which reduces the commercial value of cod liver oil. Therefore, before packaging of liver oil, it is necessary to carry out low-temperature treatment, so that a certain oil in the higher freezing point can be filled and analyzed. The liver oil obtained after pressure filtration can still be maintained in the clear state in winter. According to the “Pharmacopoeia of the People's Republic of China”, cod liver oil must not precipitate at 0°C, but the pressure filtration effect is poor, and when cooling slowly, the crystalline particles are large and the pressure filtration effect is high. Therefore, in actual production, cod liver oil needs to gradually cool down to 1-2°C in 5-7 days, and then be placed in a lower cold room to -2 to -3°C, which takes 3-5 days. . The precipitated liver oil has cooled and precipitated, and the oil is separated using a frame and frame machine. The stearic acid glyceride obtained after pressure filtration is an extremely useful industrial raw material, such as soaps, candles, paints, etc., and can also be eaten. 3. Straight fire fusion method to make cod liver oil Although this method is a relatively primitive method of melting oil, but due to simple equipment, low production costs, in particular, fresh raw materials can be processed in time, improve the quality of cod liver oil is good, so the use of fishermen in our country This method smelts dolphin oil and fish internal organs. The principle is to remove the oil and fat by heating the tissue cells of the oil and fat. Since the adipose tissue contains most of the fat in its cells, and this oil is mainly present in free form, the oil can be easily separated once the cell breaks. There are many ways to rupture a cell, but the most basic and most practical method is heat treatment. Straight fire out of the law can be divided into dry fried and decoction two. Dry frying easily burns the raw material to reduce the quality of the oil, and in the absence of water, it is difficult for the oil to fully melt out. The advantage of the water frying method is not only that the raw material is not charred, but also that the surface of the raw material has hydrophilic properties. When sufficient water is present, it can reduce the moisture content of the material and its properties. Generally, the amount of water added is 25-30% of the weight of the raw material, and the effect of melting out with seawater can be improved. In the process of melting the oil, in order to avoid the overflow of water when boiling, the feeding to the pot should not be too full, generally the water in the pot should be kept 15-20 cm below the edge of the pot. The heating temperature should be gradually increased, stirring should not be too fast, so as not to form gels between oil and protein. In general, there are three stages of melting. The first stage is to heat the contents of the pot to about 50°C in one hour. Then warm up 65-75 °C, and maintain about 2 hours, during this period should be constantly stirring, which belongs to the second stage. The final stage is the stage of oil precipitation, and the temperature must reach the boiling point. The time is usually about 1 hour. In order to effectively separate the resin, the mixture should be allowed to stand for about 2 hours after melting. If the oil is not allowed to float or float slowly during the standing process, some salt may be added in an amount of 2-7% of the raw material. 4. Fermentation method for cod liver oil This method is a method for separating oils by decomposing protein cells by enzymes, which is suitable for the extraction of various cod liver oils. When cutting the shark or other fish, remove the liver, remove the gallbladder first, cut into larger pieces with a knife, put it in clean water and squeeze it gently to discharge the blood, and then cut it into 3 cm with a knife. The small cubes, plus 15-20% of the fine salt, into the barrel or cylinder to mix, sealed, to prevent direct sunlight, to avoid oxidative rancidity, after several months of fermentation, liver oil will be separated and float in the upper layer, residue and salt The liquid sinks to the bottom. The purpose of adding salt is mainly to prevent the non-fat organic components in the fish liver from corrupting and affect the quality of liver oil.

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