Key Points and Methods for Quality Control of Shrimp Meal and Squid Paste
Quality Control of Shrimp Meal and Squid Paste
Liu Xingwang, Wang Hualang
(Research Center of Guangdong Hengxing Group, Zhanjiang 524094)
Abstract: This paper reviews the quality control standards and the current situation of adulteration of shrimp meal and squid paste, and proposes corresponding identification and detection methods. It has certain guiding significance for the trade of feed ingredients and the management and control of feed quality.
Author profile:
Liu Xingwang (1979-): male, native of Jinan, Shandong, doctoral student, mainly engaged in research on aquatic animal nutrition and the development of aquatic feed, Tel: 0759-2711372,
Email：[email protected]
Author correspondence address: Research Center of Guangdong Hengxing Group Co., Ltd., Jinkang Middle Road, Mazhang Economic Development Zone, Zhanjiang City, Guangdong Province. Postcode: 524094
Shrimp meal and squid paste are important aquatic feed ingredients. With the vigorous development of the aquatic feed industry, the demand for shrimp meal and squid paste has also grown rapidly. However, both are made from processing scraps of marine animals, so problems such as unstable quality and large quality differences among different manufacturers exist. Moreover, as demand increases, problems such as adulteration and fraud have become increasingly serious. Based on the author's practical experience, the following discusses some issues concerning the quality control and adulteration identification of shrimp meal and squid paste.
1. Quality control and adulteration identification of shrimp meal
1.1 Sources and feeding value of shrimp meal
Shrimp meal is a by-product after shrimp processing. Processing plants for prawns, lobsters and mantis shrimp in China's coastal areas can produce about 60,000 tons of shrimp meal annually. The main components are generally a mixture of shrimp shells and shrimp scraps. According to differences in composition, it can also be divided into shrimp powder, shrimp shell powder, shrimp head powder, whole shrimp powder, etc. In addition to being rich in chitin and protein, shrimp meal is also rich in DHA, EPA, choline, phospholipids, cholesterol, astaxanthin, shrimp red pigment, and various beneficial elements such as phosphorus, calcium, iron, manganese, zinc and copper.
The protein, choline, phospholipids and cholesterol in shrimp meal are mainly concentrated in the head cavity, chelipeds and walking legs. They are indispensable substances for animals and have the effect of improving animal fat metabolism and enhancing immunity. The EPA and DHA rich in shrimp oil can improve animal blood circulation and promote nervous function and the reproductive system. Astaxanthin and shrimp red pigment can slow down the process of lipid peroxidation and prevent animal cells from being damaged by free radicals. They are also natural non-toxic food colorants and have a coloring effect on animals. In addition, the abundant active calcium contained in shrimp shells is very easily absorbed and utilized by livestock and poultry. Therefore, shrimp meal can be said to be a feed ingredient with very high usable value.
Tests have proved that shrimp meal has good feeding value in livestock, poultry and aquatic feed. Shrimp meal can improve feed palatability and help with the coloring of broiler shanks and egg yolks. It can promote the appetite of pigs. Adding 3-5% to finishing pigs can significantly improve meat color. Shrimp meal is the most commonly used and most appropriately priced attractant and colorant in fish and shrimp feed. Adding 5% to shrimp feed has good effects on attractability, growth promotion and body color improvement. It also contains a molting stimulant that can effectively promote molting in crustaceans.
1.2 Quality indicators of shrimp meal
The sources of raw materials for making shrimp meal are uncertain and vary greatly in quantity, and its quality components vary greatly with raw materials, varieties, processing methods and freshness. Therefore, how to control the quality of shrimp meal, improve its feeding value and improve processing technology are issues urgently needing solutions at present.
The nutritional components of shrimp meal vary greatly due to multiple influencing factors, and salt is often added during processing for preservation, so the salt content is relatively high. Generally speaking, if the salt content is greater than 7%, it is best not to use it in compound feed. Therefore, when using it, various components must be tested in detail before it can be used for formula calculation. Good-quality shrimp meal should have moisture below 12%, crude fat below 10%, hydrochloric acid-insoluble matter below 3%, and salt content less than 7%. Crude protein and crude ash vary greatly with different processing techniques. Generally, the crude protein content is around 30%, and the crude ash content should be below 42%. The general nutritional components of shrimp meal with different compositions can be seen in Table 1.
Table 1 Nutritional components of shrimp meal-type raw materials
Shrimp shell powder (CNS) Shrimp shell powder Shrimp powder (shrimp shell + shrimp scraps) Shrimp head powder Whole shrimp powder
Moisture % below 12.0 12.0 7.5 3.2 ---
Crude protein % --- 24.9 37.2 58.2 73.6
Crude fat % below 2.5 2.6 5.3 8.9 6.3
Crude fiber % --- 13.6 21.4 11.9 ---
Crude ash % below 42 39.4 38.2 22.6 18.6
Calcium % --- 12.9 15.0 --- 3.0
Phosphorus % --- 1.4 2.2 --- 1.1
Total nitrogen % below 4.02 --- 5.97 9.32 ---
Salt % below 7.0 --- --- --- ---
Hydrochloric acid-insoluble matter % below 3.0 --- --- --- ---
Therefore, after shrimp meal generally arrives, the physicochemical items that need to be tested include moisture, sand content, salt content, ash, crude protein, crude fat, calcium and phosphorus content, etc. Because protein, fat, ash, etc. vary greatly, quality inspection personnel need to determine the standards for these indicators according to the requirements of the formula. Particular attention should be paid to the moisture, sand and salt content of shrimp meal. If they exceed the control standards, weight deduction, price reduction or return should be handled according to certain standards.
In addition, because the production of shrimp meal is generally dried by sun-drying, it is prone to bacterial contamination, spoilage and oxidation. Therefore, before use, volatile basic nitrogen needs to be tested to judge its freshness. In addition, microbial indicators such as total bacterial count and intestinal pathogenic bacteria such as Salmonella also need to be tested. The acceptable standards are generally volatile basic nitrogen less than 0.3 mg/g, pH less than 7.8; total bacterial count less than 1 x 107 per gram, and Salmonella must not be detected. If further testing is necessary, items such as arsenic, mercury, peroxide value and nitrite can also be tested. General feed enterprises do not have the conditions for detecting bacteria and other microorganisms, so testing items such as bacteria and heavy metals can be detected and controlled through regular sample submission.
It is worth mentioning here that part of the protein in the crude protein value of shrimp meal comes from the nitrogen of crustacean chitin; the chitin content of shrimp powder is very close to the crude fiber content. In addition to being in the shell, it is also formed in the inner layer of the stomach wall and has no utilization value. Therefore, when calculating the formula, the non-protein nitrogen from chitin should be removed to obtain true protein. Chitin content is not easy to detect, so a rough estimation method can be used for calculation. Taking shrimp shell powder as an example, it contains about 35% crude protein, and shrimp shells contain about 50% chitin, of which inorganic nitrogen accounts for about 7%. Therefore, the protein content from non-protein nitrogen is about 21.9% (50 x 7% x 6.25), so the true protein content should be 13.1%.
1.3 Appearance inspection and adulteration identification of shrimp meal
After shrimp meal arrives, the sample should first be spread flat on a white porcelain dish for appearance inspection to check whether the odor is normal and whether there is obvious putrid ammonia odor and impurities. Shrimp shell powder is brittle and easily broken, mostly flaky, and contains broken black shrimp eye particles. Shrimp shells vary in color depending on the shrimp body pigments, from light yellow, pink to orange-red. It has an obvious dried shrimp fishy odor.
Under a microscope, horizontal lines, cross-shaped lines and other marks caused by parasites can be seen on the shrimp shell. The hairs on shrimp legs are relatively short, rarely branched, and the tips do not have feather-like small hooks. Under a stereo microscope, fragments of shrimp antennae can be seen, appearing as long tubular shapes with spiral parallel lines. Shrimp eyes are compound eyes, appearing as shrunken small flakes, dark purple or black, with horizontal shadow lines on the surface. Shrimp meat particles vary in size, have a dull luster, are translucent, and appear yellow, orange-yellow or pink. Sometimes the texture is relatively hard, or the muscle fibers easily break into small pieces. Continuous shell pieces from the shrimp body are thin and transparent, while shell pieces from the head are quite thick and opaque. Shrimp leg fragments are wide tubular, with or without hairs, flat and glossy, translucent.
The adulterants in shrimp meal come, on the one hand, from non-feed substances such as quicklime and sawdust added during processing for preservation and water absorption. On the other hand, they are toxic and harmful substances illegally added purely for huge profits, such as ammonium salts, urea, stone powder, shell powder, mud and sand, and dyes. Generally, the following methods can be used for identification:
Hydrochloric acid dissolution identification method: Place a small amount of sample on a white porcelain dish and add 8-10 drops of 1:3 hydrochloric acid. If bubbles are produced, it indicates the incorporation of carbonate substances such as quicklime, stone powder and shell powder.
Water washing identification method: Add about 150 ml of water to a 200 ml beaker, take about 5 g of sample and slowly sprinkle it onto the water surface for observation. Mud and sand sink to the bottom faster than the sample. Then carefully rinse the sediment with water to observe sand and stones. Separately take 10 g of sample, place it in a 100 ml tall beaker, add 80 ml of carbon tetrachloride, stir evenly and let stand for 1 minute. Filter out the floating matter, dry it and sieve it. Filter out the sediment and dry it. Powdered plant matter mostly remains on the 10-20 mesh sieve surface. The water washing suspension method can also observe whether the solution has color to determine whether substances such as dyes have been added.
Lignin qualitative method: Place a small amount of sample on a white porcelain dish, wet the sample with phloroglucinol (5% ethanol solution), and after 2 minutes add hydrochloric acid dropwise. A deep red color proves the incorporation of plant substances such as sawdust.
Urea qualitative method: Place a small amount of sample on a white porcelain dish, add 2-3 drops of cresol red (0.1% aqueous solution) and 2-3 drops of urease (0.4% aqueous solution), and observe after 5 minutes. If purplish red appears, it indicates the incorporation of urea.
Ammonium salt qualitative method: Place a small amount of sample into a test tube, add about 5 ml of water and shake well, then add 1:3 dilute hydrochloric acid and several drops of 10% barium chloride solution. If a white precipitate appears, it indicates the incorporation of ammonium sulfate. Separately place a small amount of sample on a white porcelain dish, add 3 crystals of diphenylamine and 2 drops of water, then add 1 drop of sulfuric acid. If a deep blue color appears, it indicates the incorporation of ammonium nitrate.
In short, shrimp meal inspection is a complex and changeable process. Microscopic examination is intuitive and clear, but requires high skill and rich experience. Although qualitative identification is simple and rapid, it can only indirectly indicate the presence of a certain substance, and it is difficult to determine the amount. Sanitary indicators are the prerequisite for judging whether a product is good or bad and whether it can be used as livestock and poultry feed. Physicochemical testing is an indispensable step in formula calculation and is also a reliable basis for truly judging product quality. Raw material purchasers and quality inspection staff should fully understand and master the above methods, and only by continuously learning and communicating with each other can they minimize the harm and unnecessary losses brought by inferior raw materials.
2. Quality control and adulteration identification of squid paste
2.1 Sources and feeding value of squid paste
Squid paste is a paste made from squid (cuttlefish) viscera as raw material through processes such as refining, filtration, sterilization and drying. It is an excellent attractant and nutritional supplement in aquatic, livestock and poultry feed.
Tests have proved that adding squid paste to aquatic feed has an obvious attractant effect on fish and shrimp and can improve feed palatability and utilization. This is because the amino acid composition of squid paste is good, and the amino acids it contains have a very strong attracting effect on fish and shrimp. The highly unsaturated fatty acids and cholesterol it contains are indispensable nutritional elements for promoting digestion, absorption and growth of shrimp and crabs. At the same time, squid paste is rich in sterol molting stimulants and some other unknown nutritional factors, which can effectively promote molting in crustaceans and improve the immunity of aquatic animals. In addition, the appropriate addition of squid paste to feed has an auxiliary binding effect on pellet feed granulation, can improve pellet mill granulation efficiency, and reduce wear on ring dies and press rolls. Therefore, squid paste is widely used in aquatic feed, and market demand has risen year after year.
2.2 Quality indicators and control of squid paste
Squid paste appears as a black or brown paste-like substance with a strong cuttlefish fishy aroma, generally packed in barrels. Therefore, quality inspection of squid paste must be sampled from the middle of the barrel.
Because the viscera of squid and other cephalopods have a very high moisture content, mostly above 75%, the moisture content of squid paste is still very high after processing and drying, generally around 35%. Excessive moisture content easily causes problems such as rancidity of raw materials and affects moisture control in the production process, increasing production costs. Therefore, when feed enterprises purchase squid paste, they should negotiate with the manufacturer to reduce the moisture content in the product as much as possible, preferably controlling moisture below 30%.
The protein content of squid paste varies with its moisture content and is generally required to be above 30%. It should be pointed out that the amino acid content in squid paste is very balanced. The essential amino acids such as lysine, methionine and histidine are very abundant and reasonably proportioned, so it is a high-quality protein source. Enterprises with the conditions should determine the amino acid composition of the squid paste used, as this is the most effective way to control its quality.
Due to differences in processing and treatment methods, the fat content of squid paste also varies greatly. The fat in squid paste is rich in various essential fatty acids, such as EPA and DHA, which are necessary for animal growth and can improve animal immunity. Many aquatic product processing enterprises process squid paste to extract the oil in it and make squid oil, which has very high economic value. Therefore, after squid paste enters a feed enterprise, its fat content must be tested. The fat content of high-quality squid paste should be controlled at around 20%. If too low, it indicates losses during processing; if too high, it affects protein and other nutritional indicators.
In all links such as processing, transportation and storage, squid paste must strictly comply with the Measures for the Administration of Safety and Hygiene of Animal-Derived Feed Products. To control its quality, processing and feed enterprises should regularly or batch-by-batch test safety and hygiene indicators such as total bacterial count, Escherichia coli, Salmonella, heavy metals and specific pathogenic bacteria. Only after meeting the standards specified by the state can it be purchased or used. In addition, squid paste is highly prone to rancidity and deterioration during storage and transportation. Therefore, indicators such as volatile basic nitrogen and acid value must be tested regularly. The acceptable standards are generally volatile basic nitrogen less than 4 mg/g and acid value less than 40 mgKOH/g.
Because the physical properties of squid paste are paste-like, adulteration is also difficult to identify if it occurs. Therefore, feed enterprises should choose excellent and honest suppliers and manufacturers for purchase. Common adulteration generally involves adding sea sand, salt, etc. Therefore, after squid paste arrives, the ash and salt contents must be determined. Salt content is generally controlled below 10%, while salt content should be controlled below 7%. In addition, using high-performance liquid chromatography to detect the amino acid composition of squid paste is the most effective method for controlling its quality.
2.3 Squid powder
Squid powder (also called squid viscera powder) is a product made by aquatic product processing enterprises after separating oil from squid paste or squid heads, feet and viscera, mixing with soybean meal and fish soluble paste, and then drying and crushing. It has the characteristics of simple addition and low moisture, plays the same role in feed as squid paste, and is also often used by feed enterprises. However, its quality is also very difficult to control because it is affected by the quality of squid paste and the mixing ratio with soybean meal. Moreover, many illegal manufacturers mix deteriorated squid paste with rapeseed meal, bran and other substances, seriously damaging the quality of this raw material and leading to poor utilization. At present, most feed enterprises do not have effective methods to control its quality, so it can be used as a supplement to squid paste, but its use should be controlled as much as possible.
References:
Qin Yi. Using simple methods to identify whether feed is adulterated. Modern Fisheries Information, 2003, 18(1), 32-32.
Wang Youming. Some thoughts on preventing adulteration of feed ingredients. Feed China, 2002(12), 19-19.
Peng Jinrui. Some thoughts on the problem of feed adulteration. Feed China, 2001(13), 9-10.
Nie Qingping. A brief discussion on the utilization and inspection of shrimp meal. Guangdong Feed, 1996(1), 42-43.
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Very glad to see this article here!
Dr. Liu is really so talented!
The article is very valuable for reference!
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Not bad, not bad! Thanks!
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I have a different view on the quality indicators of squid paste in this article.
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Good, very good.
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I have not used these two things yet, but it is necessary to learn about them.
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Those with different views should share them with everyone. Looking forward to it.
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Thanks for sharing, I will study it first.
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The original poster has worked hard.
(Research Center of Guangdong Hengxing Group, Zhanjiang 524094)
Abstract: This paper reviews the quality control standards and the current situation of adulteration of shrimp meal and squid paste, and proposes corresponding identification and detection methods. It has certain guiding significance for the trade of feed ingredients and the management and control of feed quality.
Author profile:
Liu Xingwang (1979-): male, native of Jinan, Shandong, doctoral student, mainly engaged in research on aquatic animal nutrition and the development of aquatic feed, Tel: 0759-2711372,
Email：[email protected]
Author correspondence address: Research Center of Guangdong Hengxing Group Co., Ltd., Jinkang Middle Road, Mazhang Economic Development Zone, Zhanjiang City, Guangdong Province. Postcode: 524094
Shrimp meal and squid paste are important aquatic feed ingredients. With the vigorous development of the aquatic feed industry, the demand for shrimp meal and squid paste has also grown rapidly. However, both are made from processing scraps of marine animals, so problems such as unstable quality and large quality differences among different manufacturers exist. Moreover, as demand increases, problems such as adulteration and fraud have become increasingly serious. Based on the author's practical experience, the following discusses some issues concerning the quality control and adulteration identification of shrimp meal and squid paste.
1. Quality control and adulteration identification of shrimp meal
1.1 Sources and feeding value of shrimp meal
Shrimp meal is a by-product after shrimp processing. Processing plants for prawns, lobsters and mantis shrimp in China's coastal areas can produce about 60,000 tons of shrimp meal annually. The main components are generally a mixture of shrimp shells and shrimp scraps. According to differences in composition, it can also be divided into shrimp powder, shrimp shell powder, shrimp head powder, whole shrimp powder, etc. In addition to being rich in chitin and protein, shrimp meal is also rich in DHA, EPA, choline, phospholipids, cholesterol, astaxanthin, shrimp red pigment, and various beneficial elements such as phosphorus, calcium, iron, manganese, zinc and copper.
The protein, choline, phospholipids and cholesterol in shrimp meal are mainly concentrated in the head cavity, chelipeds and walking legs. They are indispensable substances for animals and have the effect of improving animal fat metabolism and enhancing immunity. The EPA and DHA rich in shrimp oil can improve animal blood circulation and promote nervous function and the reproductive system. Astaxanthin and shrimp red pigment can slow down the process of lipid peroxidation and prevent animal cells from being damaged by free radicals. They are also natural non-toxic food colorants and have a coloring effect on animals. In addition, the abundant active calcium contained in shrimp shells is very easily absorbed and utilized by livestock and poultry. Therefore, shrimp meal can be said to be a feed ingredient with very high usable value.
Tests have proved that shrimp meal has good feeding value in livestock, poultry and aquatic feed. Shrimp meal can improve feed palatability and help with the coloring of broiler shanks and egg yolks. It can promote the appetite of pigs. Adding 3-5% to finishing pigs can significantly improve meat color. Shrimp meal is the most commonly used and most appropriately priced attractant and colorant in fish and shrimp feed. Adding 5% to shrimp feed has good effects on attractability, growth promotion and body color improvement. It also contains a molting stimulant that can effectively promote molting in crustaceans.
1.2 Quality indicators of shrimp meal
The sources of raw materials for making shrimp meal are uncertain and vary greatly in quantity, and its quality components vary greatly with raw materials, varieties, processing methods and freshness. Therefore, how to control the quality of shrimp meal, improve its feeding value and improve processing technology are issues urgently needing solutions at present.
The nutritional components of shrimp meal vary greatly due to multiple influencing factors, and salt is often added during processing for preservation, so the salt content is relatively high. Generally speaking, if the salt content is greater than 7%, it is best not to use it in compound feed. Therefore, when using it, various components must be tested in detail before it can be used for formula calculation. Good-quality shrimp meal should have moisture below 12%, crude fat below 10%, hydrochloric acid-insoluble matter below 3%, and salt content less than 7%. Crude protein and crude ash vary greatly with different processing techniques. Generally, the crude protein content is around 30%, and the crude ash content should be below 42%. The general nutritional components of shrimp meal with different compositions can be seen in Table 1.
Table 1 Nutritional components of shrimp meal-type raw materials
Shrimp shell powder (CNS) Shrimp shell powder Shrimp powder (shrimp shell + shrimp scraps) Shrimp head powder Whole shrimp powder
Moisture % below 12.0 12.0 7.5 3.2 ---
Crude protein % --- 24.9 37.2 58.2 73.6
Crude fat % below 2.5 2.6 5.3 8.9 6.3
Crude fiber % --- 13.6 21.4 11.9 ---
Crude ash % below 42 39.4 38.2 22.6 18.6
Calcium % --- 12.9 15.0 --- 3.0
Phosphorus % --- 1.4 2.2 --- 1.1
Total nitrogen % below 4.02 --- 5.97 9.32 ---
Salt % below 7.0 --- --- --- ---
Hydrochloric acid-insoluble matter % below 3.0 --- --- --- ---
Therefore, after shrimp meal generally arrives, the physicochemical items that need to be tested include moisture, sand content, salt content, ash, crude protein, crude fat, calcium and phosphorus content, etc. Because protein, fat, ash, etc. vary greatly, quality inspection personnel need to determine the standards for these indicators according to the requirements of the formula. Particular attention should be paid to the moisture, sand and salt content of shrimp meal. If they exceed the control standards, weight deduction, price reduction or return should be handled according to certain standards.
In addition, because the production of shrimp meal is generally dried by sun-drying, it is prone to bacterial contamination, spoilage and oxidation. Therefore, before use, volatile basic nitrogen needs to be tested to judge its freshness. In addition, microbial indicators such as total bacterial count and intestinal pathogenic bacteria such as Salmonella also need to be tested. The acceptable standards are generally volatile basic nitrogen less than 0.3 mg/g, pH less than 7.8; total bacterial count less than 1 x 107 per gram, and Salmonella must not be detected. If further testing is necessary, items such as arsenic, mercury, peroxide value and nitrite can also be tested. General feed enterprises do not have the conditions for detecting bacteria and other microorganisms, so testing items such as bacteria and heavy metals can be detected and controlled through regular sample submission.
It is worth mentioning here that part of the protein in the crude protein value of shrimp meal comes from the nitrogen of crustacean chitin; the chitin content of shrimp powder is very close to the crude fiber content. In addition to being in the shell, it is also formed in the inner layer of the stomach wall and has no utilization value. Therefore, when calculating the formula, the non-protein nitrogen from chitin should be removed to obtain true protein. Chitin content is not easy to detect, so a rough estimation method can be used for calculation. Taking shrimp shell powder as an example, it contains about 35% crude protein, and shrimp shells contain about 50% chitin, of which inorganic nitrogen accounts for about 7%. Therefore, the protein content from non-protein nitrogen is about 21.9% (50 x 7% x 6.25), so the true protein content should be 13.1%.
1.3 Appearance inspection and adulteration identification of shrimp meal
After shrimp meal arrives, the sample should first be spread flat on a white porcelain dish for appearance inspection to check whether the odor is normal and whether there is obvious putrid ammonia odor and impurities. Shrimp shell powder is brittle and easily broken, mostly flaky, and contains broken black shrimp eye particles. Shrimp shells vary in color depending on the shrimp body pigments, from light yellow, pink to orange-red. It has an obvious dried shrimp fishy odor.
Under a microscope, horizontal lines, cross-shaped lines and other marks caused by parasites can be seen on the shrimp shell. The hairs on shrimp legs are relatively short, rarely branched, and the tips do not have feather-like small hooks. Under a stereo microscope, fragments of shrimp antennae can be seen, appearing as long tubular shapes with spiral parallel lines. Shrimp eyes are compound eyes, appearing as shrunken small flakes, dark purple or black, with horizontal shadow lines on the surface. Shrimp meat particles vary in size, have a dull luster, are translucent, and appear yellow, orange-yellow or pink. Sometimes the texture is relatively hard, or the muscle fibers easily break into small pieces. Continuous shell pieces from the shrimp body are thin and transparent, while shell pieces from the head are quite thick and opaque. Shrimp leg fragments are wide tubular, with or without hairs, flat and glossy, translucent.
The adulterants in shrimp meal come, on the one hand, from non-feed substances such as quicklime and sawdust added during processing for preservation and water absorption. On the other hand, they are toxic and harmful substances illegally added purely for huge profits, such as ammonium salts, urea, stone powder, shell powder, mud and sand, and dyes. Generally, the following methods can be used for identification:
Hydrochloric acid dissolution identification method: Place a small amount of sample on a white porcelain dish and add 8-10 drops of 1:3 hydrochloric acid. If bubbles are produced, it indicates the incorporation of carbonate substances such as quicklime, stone powder and shell powder.
Water washing identification method: Add about 150 ml of water to a 200 ml beaker, take about 5 g of sample and slowly sprinkle it onto the water surface for observation. Mud and sand sink to the bottom faster than the sample. Then carefully rinse the sediment with water to observe sand and stones. Separately take 10 g of sample, place it in a 100 ml tall beaker, add 80 ml of carbon tetrachloride, stir evenly and let stand for 1 minute. Filter out the floating matter, dry it and sieve it. Filter out the sediment and dry it. Powdered plant matter mostly remains on the 10-20 mesh sieve surface. The water washing suspension method can also observe whether the solution has color to determine whether substances such as dyes have been added.
Lignin qualitative method: Place a small amount of sample on a white porcelain dish, wet the sample with phloroglucinol (5% ethanol solution), and after 2 minutes add hydrochloric acid dropwise. A deep red color proves the incorporation of plant substances such as sawdust.
Urea qualitative method: Place a small amount of sample on a white porcelain dish, add 2-3 drops of cresol red (0.1% aqueous solution) and 2-3 drops of urease (0.4% aqueous solution), and observe after 5 minutes. If purplish red appears, it indicates the incorporation of urea.
Ammonium salt qualitative method: Place a small amount of sample into a test tube, add about 5 ml of water and shake well, then add 1:3 dilute hydrochloric acid and several drops of 10% barium chloride solution. If a white precipitate appears, it indicates the incorporation of ammonium sulfate. Separately place a small amount of sample on a white porcelain dish, add 3 crystals of diphenylamine and 2 drops of water, then add 1 drop of sulfuric acid. If a deep blue color appears, it indicates the incorporation of ammonium nitrate.
In short, shrimp meal inspection is a complex and changeable process. Microscopic examination is intuitive and clear, but requires high skill and rich experience. Although qualitative identification is simple and rapid, it can only indirectly indicate the presence of a certain substance, and it is difficult to determine the amount. Sanitary indicators are the prerequisite for judging whether a product is good or bad and whether it can be used as livestock and poultry feed. Physicochemical testing is an indispensable step in formula calculation and is also a reliable basis for truly judging product quality. Raw material purchasers and quality inspection staff should fully understand and master the above methods, and only by continuously learning and communicating with each other can they minimize the harm and unnecessary losses brought by inferior raw materials.
2. Quality control and adulteration identification of squid paste
2.1 Sources and feeding value of squid paste
Squid paste is a paste made from squid (cuttlefish) viscera as raw material through processes such as refining, filtration, sterilization and drying. It is an excellent attractant and nutritional supplement in aquatic, livestock and poultry feed.
Tests have proved that adding squid paste to aquatic feed has an obvious attractant effect on fish and shrimp and can improve feed palatability and utilization. This is because the amino acid composition of squid paste is good, and the amino acids it contains have a very strong attracting effect on fish and shrimp. The highly unsaturated fatty acids and cholesterol it contains are indispensable nutritional elements for promoting digestion, absorption and growth of shrimp and crabs. At the same time, squid paste is rich in sterol molting stimulants and some other unknown nutritional factors, which can effectively promote molting in crustaceans and improve the immunity of aquatic animals. In addition, the appropriate addition of squid paste to feed has an auxiliary binding effect on pellet feed granulation, can improve pellet mill granulation efficiency, and reduce wear on ring dies and press rolls. Therefore, squid paste is widely used in aquatic feed, and market demand has risen year after year.
2.2 Quality indicators and control of squid paste
Squid paste appears as a black or brown paste-like substance with a strong cuttlefish fishy aroma, generally packed in barrels. Therefore, quality inspection of squid paste must be sampled from the middle of the barrel.
Because the viscera of squid and other cephalopods have a very high moisture content, mostly above 75%, the moisture content of squid paste is still very high after processing and drying, generally around 35%. Excessive moisture content easily causes problems such as rancidity of raw materials and affects moisture control in the production process, increasing production costs. Therefore, when feed enterprises purchase squid paste, they should negotiate with the manufacturer to reduce the moisture content in the product as much as possible, preferably controlling moisture below 30%.
The protein content of squid paste varies with its moisture content and is generally required to be above 30%. It should be pointed out that the amino acid content in squid paste is very balanced. The essential amino acids such as lysine, methionine and histidine are very abundant and reasonably proportioned, so it is a high-quality protein source. Enterprises with the conditions should determine the amino acid composition of the squid paste used, as this is the most effective way to control its quality.
Due to differences in processing and treatment methods, the fat content of squid paste also varies greatly. The fat in squid paste is rich in various essential fatty acids, such as EPA and DHA, which are necessary for animal growth and can improve animal immunity. Many aquatic product processing enterprises process squid paste to extract the oil in it and make squid oil, which has very high economic value. Therefore, after squid paste enters a feed enterprise, its fat content must be tested. The fat content of high-quality squid paste should be controlled at around 20%. If too low, it indicates losses during processing; if too high, it affects protein and other nutritional indicators.
In all links such as processing, transportation and storage, squid paste must strictly comply with the Measures for the Administration of Safety and Hygiene of Animal-Derived Feed Products. To control its quality, processing and feed enterprises should regularly or batch-by-batch test safety and hygiene indicators such as total bacterial count, Escherichia coli, Salmonella, heavy metals and specific pathogenic bacteria. Only after meeting the standards specified by the state can it be purchased or used. In addition, squid paste is highly prone to rancidity and deterioration during storage and transportation. Therefore, indicators such as volatile basic nitrogen and acid value must be tested regularly. The acceptable standards are generally volatile basic nitrogen less than 4 mg/g and acid value less than 40 mgKOH/g.
Because the physical properties of squid paste are paste-like, adulteration is also difficult to identify if it occurs. Therefore, feed enterprises should choose excellent and honest suppliers and manufacturers for purchase. Common adulteration generally involves adding sea sand, salt, etc. Therefore, after squid paste arrives, the ash and salt contents must be determined. Salt content is generally controlled below 10%, while salt content should be controlled below 7%. In addition, using high-performance liquid chromatography to detect the amino acid composition of squid paste is the most effective method for controlling its quality.
2.3 Squid powder
Squid powder (also called squid viscera powder) is a product made by aquatic product processing enterprises after separating oil from squid paste or squid heads, feet and viscera, mixing with soybean meal and fish soluble paste, and then drying and crushing. It has the characteristics of simple addition and low moisture, plays the same role in feed as squid paste, and is also often used by feed enterprises. However, its quality is also very difficult to control because it is affected by the quality of squid paste and the mixing ratio with soybean meal. Moreover, many illegal manufacturers mix deteriorated squid paste with rapeseed meal, bran and other substances, seriously damaging the quality of this raw material and leading to poor utilization. At present, most feed enterprises do not have effective methods to control its quality, so it can be used as a supplement to squid paste, but its use should be controlled as much as possible.
References:
Qin Yi. Using simple methods to identify whether feed is adulterated. Modern Fisheries Information, 2003, 18(1), 32-32.
Wang Youming. Some thoughts on preventing adulteration of feed ingredients. Feed China, 2002(12), 19-19.
Peng Jinrui. Some thoughts on the problem of feed adulteration. Feed China, 2001(13), 9-10.
Nie Qingping. A brief discussion on the utilization and inspection of shrimp meal. Guangdong Feed, 1996(1), 42-43.
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Thanks for sharing, very good material.
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Very good material, thanks for sharing.
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Very glad to see this article here!
Dr. Liu is really so talented!
The article is very valuable for reference!
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Very good material, thanks for sharing, thank you.
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Not bad, not bad! Thanks!
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I have a different view on the quality indicators of squid paste in this article.
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Good, very good.
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I have not used these two things yet, but it is necessary to learn about them.
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Those with different views should share them with everyone. Looking forward to it.
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Thanks for sharing, I will study it first.
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The original poster has worked hard.