JP2008306998A - Solid compounded feed for aquaculture, method for aquaculture, and toxic substance-reduced cultured marine animals - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To inexpensively obtain a compounded feed for aquaculture having a low content of dioxins and to efficiently produce cultured marine animals having a lower content of accumulated dioxins and being safe and high in quality by using the compounded feed. <P>SOLUTION: The solid compounded feed for aquaculture mainly consists of a liquid fish oil treated with at least activated charcoal, and mush. When molded into pellets, this feed becomes an easy-to-feed high-energy and highly safe one because the liquid fish oil is made free from toxic substances, especially dioxins by treatment with at least activated charcoal. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a solid feed for aquaculture that has a low content of harmful substances, particularly dioxins and impurities including coplanar PCB, and is suitable for aquaculture, aquaculture method using the same, and aquaculture fish that reduce harmful substances About.

  In recent years, various seafood such as yellowtail, hamachi, and tuna have been cultivated actively, and the demand for food that can be obtained at a relatively affordable price compared to high-quality natural seafood is increasing. These farmed fish are generally fattened in fish farms from juvenile or juvenile fish to a size suitable for shipping. The feed that is given at that time is a mixed feed that has a smaller environmental impact than raw and mixed feeds, and it is becoming the mainstream by adding nutritional ingredients to the raw fish meal and fish oil. There is an advantage that a corresponding mixed feed can be easily prepared.

Cultured mixed feed is usually fed after being formed into moist pellets having a relatively high water content or dry pellets having a low water content. For example, Patent Documents 1 to 3 include conventional techniques relating to blending and molding of feed, and a binder for moist pellet feed that is easily dissipated in water, an additive for promoting growth and improving productivity, and an extruder. Techniques relating to pellets (EP pellets) formed by processing are disclosed.
JP-A-3-281873 JP-A-6-54652 JP 2000-287628 A

  On the other hand, there is a growing interest in food safety, and the accumulation of harmful substances, such as dioxins, that are ingested through foods has become a major problem. Dioxins are a general term for substances such as polychlorinated dibenzo-para-dioxin (PCDD) and polychlorinated dibenzofuran (PCDF), and coplanar PCB (Co-PCB). kg body weight / day (TEQ: toxicity equivalent amount calculated using a toxicity equivalent coefficient as a conversion coefficient). According to a survey by the Ministry of Health, Labor and Welfare, the amount of dioxins taken in in general eating habits is considered to be well below the daily intake of tolerable food and is not considered to affect health. There is a concern that the ratio of intake from sardines is high.

  This is because dioxins have been reported to accumulate in natural fish and shellfish due to marine pollution, etc., and since mixed feed is naturally derived, accumulation of dioxins in farmed fish is also expected through this. Because. Therefore, it is desired to produce aquaculture fish with lower accumulation of dioxins and to further increase the safety and security of the aquaculture fish.

  As a conventional technique related to the reduction of dioxins, for example, Patent Document 4 discloses that chlorella having a high chlorophyll content that promotes the excretion of dioxins can be used as a bait for fish rotifer to reduce the contamination of cultured fish. It has been proposed to add a carbon material capable of adsorbing dioxins into feed for fish farming or livestock. Patent Documents 6 to 8 disclose methods for removing dioxins contained in oil by performing various treatments on oil extracted from seafood and the like.

Special Table 2000-175680 WO05 / 39312 pamphlet JP 2005-532460 A JP-T-2004-504442 JP-T-2005-517601

  However, Patent Document 4 is intended for aquaculture using rotifer as a bait, and the effect of addition to the mixed feed is unknown and the cost is also increased. The method of Patent Document 5 is also only described in the examples of the feed for rats, and the effect on the cultured fish is unclear, and since dioxins remain in the mixed feed, contamination of the farm by leftovers There are concerns.

  Since the methods of Patent Documents 6 to 8 enable application to foodstuffs, pharmaceutical preparations, and the like, the process is complicated and takes time and effort to manufacture. In addition, in the case of having a deodorization step, there is a problem that the cost is increased, such as being unsuitable for fish farming where it is desirable to leave a fish odor, and a vacuum pump and a decompression vessel are required in the decompression step.

  Accordingly, an object of the present invention is to obtain a cultured feed for aquaculture with a low dioxin content at low cost, and to use the blended feed to produce a safe and high-quality cultured fish and shellfish with a lower accumulation of dioxins. It is to produce efficiently.

  The present invention has been made in view of the above circumstances, and the solid feed for aquaculture according to claim 1 contains, as main components, liquid fish oil in which harmful substances are reduced by treatment with activated carbon and mash. It is formed into a pellet shape.

  Hazardous substances in fish oil as raw materials, such as dioxins, are adsorbed by contacting with activated carbon. Since activated carbon is easily removed by subsequent filtration, liquid fish oil with reduced harmful substances can be obtained. This liquid fish oil is added and blended with mash containing fish meal etc., and the solid blended feed for aquaculture formed into pellets is easy to manufacture and low cost, and by making it the optimal blend according to the fish species and fish weight, By suppressing the accumulation of harmful substances and promoting growth, it is possible to produce cultured seafood with good meat quality, high quality and high safety. In addition, it is easier to feed compared to raw and pasteurized foods, and since it contains the necessary nutrients at a high concentration, the total amount of feed can be reduced. Production efficiency can be greatly improved.

  In the invention of claim 2, the solid feed for aquaculture is a dry pellet having a water content of 15% by weight or less. The dry pellet has a large effect of applying the present invention because most of the crude fat component is derived from liquid fish oil and the amount of liquid fish oil used is large. In addition, a necessary nutrient can be arbitrarily blended according to the fish species to obtain a feed with a high nutritional value in a small amount, and the influence on environmental pollution is small.

  In the invention of claim 3, the solid feed for aquaculture is EP pellets granulated with an extruder. EP pellets have more fish oil that can be added than normal dry pellets, and can be made into high-fat feed, greatly reducing the weight of the feed required for a single feed and improving work efficiency. it can. Moreover, since there is much oil content, the effect which applies this invention is high, and it can be set as the safe feed in which the harmful substance was reduced more.

  In the invention of claim 4, the solid mixed feed for aquaculture has a liquid fish oil content of 5% by weight or more. When dry pellets or EP pellets are used, the content of liquid fish oil is preferably 5% by weight or more, and harmful substances derived from fish oil can be reduced to obtain a safe and high-energy feed.

  In the invention of claim 5, harmful substances in the fish oil used as a raw material are mainly dioxins. Hazardous substances in fish oil, especially dioxins, are accumulated in the fish body and there is concern about its growth and the effect on the human body that eats fish. The solid mixed feed for fish farming of the present invention adsorbs and removes dioxins by contacting with activated carbon, and can be a safe feed with reduced dioxins.

  In the invention of claim 6, the liquid fish oil contained in the solid mixed feed for aquaculture is obtained by subjecting fish oil having an acid value of 20 or less as a raw material to an alkali treatment and adsorbing with activated carbon and activated clay. Preferably, when free fatty acids and other impurities are removed by alkali treatment and then treated with activated clay in addition to activated carbon, the effect of removing dioxins and the like is enhanced, and a safer feed can be obtained.

  The invention of claim 7 is a culture method characterized in that the solid mixed feed for fish farming according to any one of claims 1 to 6 is fed to seafood for 100 days or more. By providing the solid mixed feed for fish farming of the present invention to, for example, juvenile fishery products, safety and productivity can be improved. Preferably, when the animals are reared for 100 days or more, an effect of reducing dioxins and the like in the fish body can be obtained.

  In the invention of claim 8, the fish and shellfish cultivated by the culture method of claim 7 are juvenile fish, young fish or adult fish, or farmed fish grown for a certain period in the farm. The solid mixed feed for fish farming of the present invention may be given not only to juvenile fish but also to young fish or adult fish, and also to young fish or adult fish bred with normal blended feed or live feed, etc. at a farm, for a predetermined period of time. Dioxins and the like can be reduced by rearing them.

  The invention according to claim 9 uses the culture method according to claim 7 or 8 for the culture of yellowtail, yellowtail, amberjack, tuna, hiramasa, Thailand, flounder, sea bass, rainbow trout, tiger puffer, shrimp or eel. The solid mixed feed for fish farming of the present invention can be applied to any of these fish and shellfish that have been conventionally cultivated in farms, and the effect of reducing harmful substances such as dioxins can be obtained.

  The invention of claim 10 is a cultivated seafood with reduced harmful substances cultivated by the culture method according to any one of claims 7 to 9. The cultured fish and shellfish bred by the above-described solid mixed feed for aquaculture of the present invention are cultured fish and shellfish that are high in quality, high in safety, have a good accumulation of harmful substances, particularly dioxins, and have good meat quality.

  The solid mixed feed for aquaculture of the present invention uses crude oil collected from fish that are marine animals, contains liquid fish oil in which harmful substances are reduced by treating with at least activated carbon, and fish meal as a main component, and is in a pellet form It is molded into. Liquid fish oil crude oil is oil extracted from fish that are marine animals, such as bones, skin, and built-in materials that are produced when fish are processed at fisheries processing plants, fish markets, supermarkets, etc. ) Is extracted from fish oil obtained when it is separated into fish waste and fish oil at a sorting plant, and fish oil imported from around the world such as South America, North America and Northern Europe. The fish species is not particularly limited, and for example, fish oil obtained from various fishes such as horse mackerel, sardine, cod, tuna, and miscellaneous fish can be used.

  By treating this crude oil with activated carbon, it is possible to remove harmful substances such as dioxins including coplana PCB, impurities and foreign matters, and to produce high-quality liquid oil for feed. The quality of fish oil used as a raw material varies, and generally, the acid value indicating the fatty acid content in fats and oils is used as an index for quality evaluation. If it is a relatively good quality fish oil with an acid value of 5 or less, it may be sufficient to remove harmful substances in the adsorption treatment process using activated carbon described later, but even a fish oil with a higher degree of damage can be treated sufficiently. is there. Examples of the processable raw material oil include fish oil having an acid value of 20 or less. In this case, preferably, fish oil having an acid value of 20 or less as a raw material is alkali-treated and adsorbed with activated carbon and activated clay to remove harmful substances and impurities, and to have sufficient quality as feed fats and oils. It is possible to obtain a refined oil. In addition, FFA is used as an international index corresponding to the acid value, and the acid value of 20 generally corresponds to about 10% in FFA.

Preferably, in order to obtain a high-quality refined oil for mixed feed, it is desirable to obtain a liquid fish oil from which harmful substances, impurities, and foreign substances have been removed through the following steps 1) to 6).
1) 1st water washing process: The fish oil of the acid value 20 or less used as raw material oil is heated, and it wash | cleans using water or warm water lower than this.
2) Alkali treatment step: The fish oil washed with water is brought into contact with an alkali solution.
3) Second water washing step: The alkali-treated oil is separated, heated, and washed with water or warm water having a lower temperature.
4) Dehydration step: Heat the water-washed oil to evaporate the water.
5) Adsorption treatment process: Activated carbon and activated clay are added to the dehydrated oil, and the mixture is stirred to remove harmful substances by adsorption.
6) Filtration step: Filter the adsorbed oil to separate activated carbon and activated clay.
Below, these each process is explained in full detail.

1) First water washing step In addition to harmful substances to be removed, the raw fish oil contains various impurities that are mixed or generated during the process of obtaining fish oil. Here, the purpose of washing the fish oil as the first washing step is to wash off foreign matters such as solid matter and dust, protein, water-soluble impurities, etc. contained in the fish oil (neutral). In the water washing method, the fish oil is heated to 40 to 80 ° C. while stirring, and water is added. When the temperature of the fish oil is higher than 80 ° C., it is difficult to work by separating into floating and sinking objects due to the difference in specific gravity of substances other than oil. Preferably, the temperature of the fish oil is about 70 ° C.

  The water to be used is warm water or cold water (room temperature water), and is set to be 10 ° C. lower than the temperature of the fish oil. By providing a temperature difference, water and oil can be easily separated, and impurities and water-soluble impurities can be allowed to settle in water. Preferably, it is more effective to set the temperature lower by 40 ° C. or more. The amount of water used is in the range of 10 to 50%, preferably around 10%, based on the weight or volume of fish oil. Moreover, the salt water which melt | dissolved 1-5% of salt (salt) in the warm water or water to be used can also be used. The purpose of using salt water is to improve drainage in oil.

  The showering method is effective for adding water. While warming or stirring the fish oil to around 70 ° C., the hot water or water is added by the showering method and then stirred for about 3 to 15 minutes to be stationary. The resting time is about 30 to 120 minutes or more. In the work process, it may be left overnight. In a stationary state, oil is located in the upper layer portion, impurities and foreign matters are separated in the intermediate layer portion, and flush water is separated in the lower layer portion.

2) Alkali treatment process Next, the fish oil washed with water is alkali-treated.
The alkali treatment is performed not only to remove free fatty acids in fish oil but also to remove phospholipids, gums, pigment components, oil-soluble proteins, metal components, and other impurities. If the alkali treatment is not appropriate, the yield will be deteriorated, the decoloring effect will not be obtained, and quality defects will be caused. In the present invention, the acid value of crude oil is regulated by the fact that when the acid value is high, the amount of alkali necessary for neutralization increases, so that the soap neutralized during the treatment also contains deoxidized oil. This is because there may be a case where everything is soaped.

  In the treatment method, after the water washing step of 1), the intermediate layer portion and the lower layer portion are extracted and only the oil in the upper layer portion is left, and the mixture is heated to 40 to 80 ° C. with stirring, and the alkali is added. At this time, the acid value of the oil is measured to calculate the required alkali amount, and the alkali concentration is adjusted. As the alkali, potassium hydroxide or sodium hydroxide is generally used, and a Baume specific gravity of 8 to 30 degrees Be may be used. Although it varies depending on the type of the raw material oil, one having 12 to 26 degrees Be is preferably used.

  The oil is heated to 70 ° C., for example, and an alkaline solution is added in a showering manner while stirring. Stir for 5 to 15 minutes and then let stand. In this process, free fatty acids in fish oil are neutralized by alkali to produce soap. The resting time is 60 minutes or more.

3) Second water washing step Next, the alkali-treated oil is washed again with water.
In the oil subjected to alkali treatment, the upper oil becomes deoxidized oil (alkaline), and the lower part is divided into deoxidized foots (metal soap formed by saponification neutralization of fats and oils by alkali). The purpose of the second water washing step is to wash away metal soaps, pigments, excess alkalis, etc. generated by the alkali reaction. In the water washing method, after the lower deoxidized foot is taken out, the deoxidized oil is stirred and heated to 40 to 90 ° C., and warm water or water is added.

  The water to be used is warm water or cold water (room temperature water), and is set to be 20 ° C. lower than the temperature of fish oil. By providing a larger temperature difference, it becomes easier to separate water and oil, effectively washing with water to settle and remove foreign substances such as metal soap, and preventing the deoxidized oil from saponifying due to the action of soap. be able to. Preferably, it is more effective to set the temperature lower by 40 ° C. or more. The amount of water used is 10 to 100% of the oil. “For example, assuming that the water temperature is around 20 ° C., the temperature difference of 40 ° C. or more can be maintained even when the temperature is lowered by washing with water by heating the fish oil to around 70 ° C. or higher.

  The rinsing method is almost the same as the rinsing in the first step described above, and is stirred for about 3 to 15 minutes after being put in by a shower ring method, and is allowed to stand still. The lower layer water and the middle layer are drawn every 30 to 60 minutes. In a stationary state, oil is located in the upper layer portion, impurities and foreign matters are separated in the intermediate layer portion, and flush water is separated in the lower layer portion.

  This water washing is preferably repeated 2-3 times until the pH of the lower layer water becomes neutral. Here, the purpose of washing with water is to wash away the alkali and trace soap remaining in the oil by alkali treatment. Without washing with water, there is a risk that these debris will cause bubbles to blow up during subsequent dehydration. It is important that the second water washing step is sufficiently performed, which may lead to quality defects.

4) Dehydration process The oil washed with water is heated to evaporate water.
The oil, which has been completely washed with water, is dehydrated by heating to 90 to 130 ° C. while stirring.
The purpose of the dehydration process is to increase the efficiency of the adsorption process in the next step. If activated carbon for adsorption treatment is added without dehydration, moisture in the oil is adsorbed and it becomes difficult to exhibit its original effect, so dehydration is an essential step. Moreover, there exists an effect which decomposes | disassembles and removes the peroxide contained in oil by processing at high temperature.

5) Adsorption treatment step After dehydration, activated carbon and activated clay are added and stirred.
In this step, an additive aid is used to adsorb and remove harmful substances. Among the additive aids, activated carbon exhibits a high effect on adsorption of dioxins including coplanar PCB. In addition, activated clay completely absorbs trace components and pigments, removes heavy metal fatty acids that cannot be removed by alkali treatment, soaps, oil-promoting substances such as gums, and improves filterability in the next step. Used for.

  Here, in general oil refining, it is known to add activated carbon, activated clay, etc., for example, in order to produce a decolorizing effect, but in the present invention, it is used for the purpose of adsorbing and removing harmful substances. At this time, the activated carbon mainly contributing to the adsorption of dioxins including coplanar PCB is added first, and then by adding activated clay, the dioxins removal rate is increased and other impurities are removed, The effect of producing a higher quality refined oil is seen, and it is effective to use these in combination.

  In the adsorption treatment, activated carbon is first added to the dehydrated oil and then laterally stirred for about 20 to 120 minutes. The addition amount of the activated carbon is usually 0.1% by weight or more, and the dioxins removal effect cannot be obtained unless the addition amount is less than 0.1% by weight. The amount of added activated carbon is preferably increased or decreased within a range of 1.0 to 8.0% by weight according to the dioxin value including coplanar PCB in fish crude oil. If it is normal fish crude oil, sufficient effect which removes dioxins will be acquired by adjusting the addition amount in the range of 1.0 wt%-8.0 wt%.

  In general, there are various types of activated carbon produced using coal, coconut shell, bamboo, wood, etc. as raw materials, and the particles are classified into granules, powders, granules and the like. These are conventionally used for applications such as water purification, air purification, and deodorizing agents. In the present invention, as the activated carbon used for the treatment of dioxins, it is more effective to use a powdery one rather than a granular one. Further, activated carbon generally used for water treatment or the like can be adequately handled, but a type having a large iodine adsorption amount and a large specific surface area is preferable. If this activated carbon is added first, only the oil is adsorbed on the adsorption area of the activated carbon, so that dioxins can be efficiently adsorbed and removed.

  After the activated carbon is added, activated clay is usually added in an amount of 0.1% by weight or more and stirred for about 30 to 120 minutes. Activated clay is a safe substance designated as a food additive and is used as a decolorizing agent for fats and oils, to remove pigments such as carotene, fatty acids of heavy metals, soaps, gums, etc. and lipid peroxides in fats and oils. Used for. In addition to these effects, the present invention has the effect of increasing the removal rate of dioxins and improving the filterability of powdered activated carbon. Activated clay has a large expansion of particles in the oil, so if it is added first, it will be covered with activated carbon, and the activated carbon adsorption area may not be effectively utilized.

  The addition amount of the activated clay is preferably increased or decreased in the range of 1.0 to 5.0% by weight, and the amount of the activated clay added to this value is adjusted to be in the above range. If the amount added is less than 1.0% by weight, in the next filtration step, in the case of a type having a large processing capacity of the filter, the auxiliary agent does not spread over the entire filter cloth, and filtration may be difficult. If the type has a small processing capacity, there is usually no problem. On the other hand, if the amount exceeds 5.0% by weight, the effect is the same no matter how much the amount is increased, and the decoloring effect may be worsened.

  There are continuous and batch processing methods. At this time, it is more effective to use a new circulation type stirring in addition to the conventional lateral rotation stirring as a batch type stirring device. Horizontal rotation agitation is agitation performed by rotating a rotating blade arranged in a container in the horizontal direction. Circulation type agitation is performed by providing a take-out port at the bottom of the container, sucking it with a pump, and dropping it from the top of the container. Stirring. Thereby, the contact of activated carbon and activated clay with harmful components and trace components in the oil increases, and the adsorption treatment can be performed more effectively in a short time.

  Although this step can be performed under reduced pressure, a sufficient adsorption effect can be obtained at normal pressure (atmospheric pressure). In particular, it is effective to employ a stirring method in which horizontal stirring and circulation stirring are combined, and processing can be performed efficiently without deterioration in a relatively short time. In addition, it is not necessary to have a special apparatus configuration such as a vacuum pump necessary for decompression processing or a stirring vessel that can withstand decompression, but the same series of steps from the first water washing step to the adsorption treatment step is performed. It can be done with the equipment, so it is very economical.

  In this step, auxiliary agents other than activated carbon and activated clay may be used together. For example, since activated clay is acidic, if the amount used is large, the acid value of the refined oil will increase, and in order to avoid this, pearlite or the like can be used in combination as a filtering agent. Perlite has no effect on the product and can improve filterability.

6) Filtration process Finally, the activated carbon and activated clay adsorbed with dioxins are removed by filtration. As the filter, for example, the most frequently used filter press can be used. In addition, there are filters such as a cartridge type and a spatula filter using centrifugal force, and any filter can be used as long as it can remove the auxiliary in the liquid.

  Vitamins, antioxidants and the like are added to the filtrate thus obtained as necessary to obtain liquid purified fish oil for mixed feed.

  A blended feed to be provided to cultured seafood is prepared with the liquid purified fish oil and mash as the main components. Mash is made of animal feed, mainly fish meal, with vegetable oil meals such as soybean oil meal, corn gluten meal, rice bran oil meal, grains such as wheat flour, and other additives. Therefore, it can be formed into pellets by appropriately blending the binder component with the necessary nutrients. Fish meal is obtained by making the remainder of oil extracted from fish as a raw material into powder form, and is obtained from the various fish described above.

  Here, dioxins are oil-soluble, and the fish meal consisting of the remainder obtained by extracting oil from fish as a raw material does not contain dioxins. Therefore, a treatment for removing dioxins such as fish oil is not particularly required. In addition, vegetable fats and oils may be used as fat in conventional blended feeds. In this case, fish-derived dioxins are not mixed, but the feed and nutrient components in the fish's original ecosystem differ, so that it grows. May be affected. Therefore, in the present invention, fats and oils mainly composed of fish oil are used, but a small amount of vegetable oils and fats such as soybean oil, palm oil, corn oil and the like can be added.

  When preparing a mixed feed, consider the nutritional requirements according to the fish species and fish weight, and add fish oil and mash so that components such as crude protein, crude fat, crude fiber, and crude ash are in the desired ratio. It mix | blends and shape | molds in a desired pellet form, It is set as the solid mixing feed for aquaculture of this invention. In general, it is preferable to add 5% by weight or more of purified fish oil to the mixed feed. Preferably, it can prepare suitably in the range of 10-30 weight% of refined fish oil, and 70-90 weight% of mash. The pellets may be dry pellets (usually water content of 15% by weight or less) dried by adding water vapor to the raw material and then mechanically compressed and solidified, or may be moist pellets obtained by mixing fish meat in a minced form. In the case of moist pellets, it is usually more preferable to use semi-moist pellets having a water content of about 30% by weight.

  Preferably, dry pellets, particularly EP pellets granulated with an extruder, can increase the amount of refined fish oil, so that the harmful substance reducing effect of the present invention can be easily obtained. When using an extruder, it is mixed with a larger amount of water vapor and high temperature and pressure than usual dry pellet production conditions, so sterilization proceeds, digestibility improves, and the ingredients are organized and water resistant. It is a pellet suitable for aquaculture feed. Furthermore, when it is injected from the extruder, it expands due to a pressure difference between the inside and outside and becomes an expanded pellet containing a large number of air bubbles inside, and has a floatability due to its low specific gravity.

  Since this expanded pellet is excellent in absorption and adsorption, it can contain a larger amount of purified fish oil (for example, 25 to 30% by weight) than ordinary dry pellets. In addition, after forming into pellets, fats and oils, nutrients and other components can be easily added, so that the component adjustment is easy and a highly nutritious and high fat feed can be obtained. Therefore, with a small amount of supply, a great effect on the growth of fish can be obtained, and labor and time for feeding at the farm can be greatly reduced. In addition, despite the high fish oil content, harmful substances such as dioxins that were inevitably contained in conventional refined fish oil have been greatly reduced, thus suppressing the accumulation of harmful substances in farmed fish High effect.

  The dioxin-reduced fish oil-containing feed obtained in this way has a very low content of dioxins including coplanar PCB, and is a solid feed for aquaculture that has high safety for aquaculture. Moreover, since a complicated manufacturing process and manufacturing apparatus for refining raw material fish oil are not required and expensive additives are not used, the manufacturing cost is low and the industrial utility value is high.

  The solid feed for aquaculture of the present invention can be used for any fry, young fish, young fish or adult fish at a farm, and can produce cultured seafood with reduced dioxin content. it can. In particular, when the mixed feed of the present invention is given to juvenile fish or juveniles that have a large amount of feed intake compared to the fish weight, the effect of suppressing the accumulation of dioxins is high. However, even young fish and adult fish can suppress the accumulation of further dioxins, while the content of harmful substances relative to the fish weight relatively decreases with growth. For this reason, the effect which reduces a harmful | toxic substance compared with the case where it grows using a normal mixed feed is acquired by growing by the mixed feed of this invention for a fixed period, for example, 50-100 days or more.

  These fishery products to which the aquaculture method of the present invention is applied may be natural ones captured in natural fishing grounds, or ones cultured in other aquaculture grounds for a certain period of time. The type of seafood is not particularly limited. It can be used for any seafood.

A test for confirming the effect of the present invention was conducted. First, purified fish oil with reduced harmful substances was produced by the following steps.
As raw material oil, 3470 kg of fish crude oil extracted and fractionated from walleye pollock, saury, mackerel, flounder and the like caught in the waters around Hokkaido was used.
・ Use equipment Stainless steel 10-ton reaction can, steam heating coil, stirrer, circulating gear pump, filter press horizontal type, product receiving tank ・ Processing process Crude oil loading → hot water washing once → alkali treatment → water washing twice → dehydration → Adsorption treatment (addition of auxiliary agent) → Filtration → Refined fish oil

(Crude oil charging → hot water washing)
First, fish crude oil was charged into a stainless steel reactor, heated with steam while stirring, and heated to a temperature of 80 ° C. Next, warm water at 70 ° C. for washing was prepared, and 500 kg of the fish oil charged was added by showering while stirring, and allowed to stand still after 5 to 10 minutes. After resting after about 60 minutes, the lower layer water and the intermediate layer were extracted.

(Alkali treatment)
Fish crude oil oxidation: 1.3, feed amount 3470 kg, alkali required amount calculated by factor of alkali reagent KOH and excess ratio of alkali is 8.21 kg (sodium hydroxide-solid conversion). The alkali for processing was adjusted by diluting with water so that it would be 21 degrees Be with a Baume meter.

  The washed oil was heated to 70 ° C., and the alkali solution was added by showering while stirring. After the addition, the mixture was stirred for 2 to 5 minutes and allowed to stand still. After standing still for about 60 minutes or more, the deoxidized foot of the lower layer was extracted.

(Washing in water)
The alkali-treated oil was heated to 80 ° C., and about 20% by volume of 700 L of water was added to the deoxidized oil at 40 ° C. with showering while stirring. After stirring for 5 minutes, it was allowed to stand still, and after 60 minutes from the start of the rest, the lower layer water was extracted. This washing with water was repeated three times until the pH of the lower layer water became neutral.

(Dehydration → Adsorption treatment (addition of auxiliary agent))
While stirring the washed oil, the oil was heated stepwise to 90 ° C, 100 ° C, 110 ° C and 130 ° C to evaporate the water. At this time, if the previous water washing process is not performed well, it may cause bubbles to blow and there is a risk in work, but in the present invention, the safety can be improved by repeating the water washing. When dehydration is complete, add auxiliary.

First, 40 kg of powdered activated carbon was gradually added while stirring and stirred for 30 minutes or more. Here, the addition amount of the activated carbon was 1.15% by weight with respect to the fish crude oil.
Activated carbon: Diamond Hope PXO (trade name: manufactured by Mitsubishi Chemical Calgon Co., Ltd.), particle size 44 μm, iodine adsorption amount 1000 mg / g

  Further, 50 kg of activated clay (Galleon Earth: product name, manufactured by Mizusawa Chemical Co., Ltd.) was gradually added while stirring, and then 20 kg of pearlite was added, and stirring was continued for 60 minutes or more. The amount of activated clay added was 1.44% by weight based on the fish crude oil. At this time, in addition to horizontal rotation stirring, circulation type stirring that was sucked up from the bottom of the reactor 1 and dropped from above was used in combination.

(Filtration)
Then, it filtered using the filter press machine (horizontal type), and obtained liquid fish oil for compound feed. The analysis results of the obtained product are shown below.
Product analysis: Analysis value Acid value Dioxins (pg-TEQ / g)
Crude oil 1.3 1.6
Product 1.6 0.7
Thus, the content of dioxins in the product can be greatly reduced by the above-described process, and the TEQ concentration can be reduced to 1 pg-TEQ / g or less. In addition, impurities and other impurities were also removed, and liquid oil with excellent quality was obtained for feeds with reduced harmful substances such as dioxins.

Next, using this dioxin-reduced fish oil, the raw materials are prepared so as to have the blending ratios and component values shown in Tables 1 and 2 in detail, and the extruder is used as the solid blended feed for aquaculture of the present invention. Pellets were produced (test feed). Moreover, for comparison, EP pellets (comparative feed) for comparison were produced in the same manner except that the fish oil refined by the conventional method without treatment with activated carbon and activated clay was used. Table 3 shows the analysis results of these test feed and comparative feed. In addition to the dioxin concentration, there was no significant difference in the general analysis values of the test feed and the comparative feed.

Using the obtained test feed and comparative feed, yellowtail was bred for a predetermined period under the breeding experiment conditions shown in Table 4. Both the yellowtails raised on the test feed (test zone) and the yellowtails raised on the comparative feed (target zone) had a fish weight of 680 g at the start of the experiment, enough to stop feeding the test feed twice a day. Gave a quantity. The breeding period was 250 days, and sampling for analysis was performed every 50 days. During the breeding period, the water temperature was 16.5 to 31 ° C., the salinity was 31 to 35 per mil, and 10 liters per minute. Sampling was conducted to examine changes in dioxin concentrations in fish for each of the test and target areas. In addition, the effects on fish growth and survival and the effects on fatty acids (DHA, EPA) in the fish were examined.

  FIG. 1 and FIG. 2 show the results of examining changes in the dioxin content in the whole yellowtail fish over time and changes in the amount of dioxins accumulated in the whole fish after the test, respectively. From FIG. 1, the dioxin content in the test group and the comparative group shows a difference after 100 days after the start of the breeding, and in the yellowtail of the test group ingested the solid mixed feed for aquaculture of the present invention until 250 days, Dioxin level remained at a low level. As shown in FIG. 1, dioxins after 250 days of breeding showed a clear decrease in all the amounts of polychlorinated dibenzo-para-dioxin (PCDD), polychlorinated dibenzofuran (PCDF), and coplanar PCB (Co-PCB). It can be seen that the mixed feed using dioxin-reduced fish oil is effective in reducing dioxins in farmed fish.

Specifically, the dioxin content in cultured yellowtail fish changed as follows.
At start of experiment: 3.81 pg-TEQ / g
150 days from the start of the experiment Target area: 0.83pg-TEQ / g
Test plot: 0.48pg-TEQ / g
Thus, the dioxin content which was 3.81 pg-TEQ / g at the start of the experiment was decreased by administration of the test feed for 150 days, and as a result, in the yellowtail which ingested the mixed feed using dioxin-reduced fish oil, A decrease of about 0.4 pg-TEQ / g was observed compared to the comparative feed using the contained fish oil. This trend continued until the 250th day, and was as follows when it was finally taken up.
Target area: 0.97pg-TEQ / g
Test section: 0.75 pg-TEQ / g
As described above, the present invention succeeded in cultivating yellowtail in which the dioxin amount (total TEQ value) in the fish body was reduced by 20 to 40%.

  3 and 4 show the results of examining the time-dependent change in the weight of the yellowtail fish and the survival rate, respectively. 3 and 4, from about 100 days of breeding, there was a difference in growth between the test group and the comparison group, and finally, the test group using the mixed feed of the present invention showed rapid growth. There was no difference in survival rate during the breeding period. This is because dioxins, which are harmful substances, do not have a fatal effect at the concentrations contained in the conventional mixed feed used in the target area, but there is a possibility that they may inhibit growth, and dioxins are reduced. In the test plot where the mixed feed of the present invention using fish oil was ingested, dioxins were reduced, and it was estimated that a good effect on the growth of the fish body was also exhibited.

  FIG. 5 is a diagram showing the fatty acid composition in fish oil blended in the test feed and the comparative feed. From the figure, the amounts of docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are almost the same. It can be said that the fatty acid composition was not affected by the treatment. When the lipid class composition was examined, there was no significant difference between the two.

  FIG. 6 is a diagram comparing the fatty acid composition in the fish after the test, where (a) is a neutral lipid and (b) is a fatty acid composition in a polar lipid. 6 (a) and 6 (b), although there was some variation in the fatty acid composition in the neutral lipid, there was no significant difference between the test group and the target group. Thus, even if it ingests the compound feed of this invention using dioxin reduced fish oil, it can be said that there is almost no big influence on the fatty acid (DHA, EPA) of a fish body.

  Table 5 shows the general analysis results of the muscle back, abdomen and liver at the end of the breeding test. From the table, the protein, ash content, and water content showed a tendency that the yellowtail in the test section to which the mixed feed of the present invention using the dioxin-reduced fish oil was administered showed a high tendency, and the lipid content showed a low tendency. As shown in FIG. 1 above, since the growth in the test area is improved by dioxin reduction, the movement of the fish becomes active, the protein and the like increase, and the lipid is estimated to burn and decrease. When the lipid class composition of the muscle back, abdomen and liver were analyzed and compared, no significant difference was found.

  As described above, the use of the solid mixed feed for aquaculture of the present invention not only can reduce the dioxin content of the cultured fish and shellfish, but also improves the quality of the edible part by improving the growth and providing a safe and high-quality aquaculture. Seafood can be produced. The aquaculture target may be not only juvenile and juvenile fish, but also young fish and adult fish, and even fish and shellfish cultivated with conventional blended feed, the solid blended feed for aquaculture of the present invention for a certain period or longer By ingesting, cultured fish and shellfish with reduced harmful substances can be obtained. Moreover, since the blended feed is easy to manufacture and the cultivation method is simple, the production cost can be greatly reduced and the utility value is high.

It is a figure which shows the time-dependent change of dioxin content in the fish body in this invention Example. It is a figure which shows the accumulation amount change of the dioxins after the test in an Example of this invention. It is a figure which shows the time-dependent change of the fish body weight in the Example of this invention. It is a figure which shows the change of the fish survival rate in this invention Example. It is a figure which shows the fatty-acid composition in the fish oil in this invention Example. It is a figure which shows the fatty acid composition in the fish body after the test in this invention Example.

Claims (10)

  A solid feed for aquaculture, characterized in that it contains liquid fish oil whose toxic substances are reduced by treatment with activated carbon and mash as main components and is formed into pellets.   2. The solid feed for aquaculture according to claim 1, wherein the dry pellets have a moisture content of 15% by weight or less.   The solid blended feed for aquaculture according to claim 2, which is an EP pellet granulated with an extruder.   The solid mixed feed for aquaculture according to claim 2 or 3, wherein the content of liquid fish oil is 5% by weight or more.   The solid mixed feed for aquaculture according to any one of claims 1 to 4, wherein the harmful substances are mainly dioxins.   The liquid fish oil is a solid mixed feed for aquaculture according to any one of claims 1 to 5, which is obtained by subjecting a fish oil having an acid value of 20 or less as a raw material to an alkali treatment and adsorption treatment with activated carbon and activated clay.   A culture method, comprising feeding the fish and shellfish with the solid mixed feed for aquaculture according to any one of claims 1 to 6 for 100 days or more.   The aquaculture method according to claim 7, wherein the seafood is fry, young or adult fish, or cultured seafood grown for a certain period in a farm.   The aquaculture method according to claim 7 or 8, which is used for aquaculture of yellowtail, hamachi, amberjack, tuna, hiramasa, Thailand, flounder, sea bass, rainbow trout, tiger puffer, shrimp or eel.   A toxic substance-reduced cultured seafood cultivated by the aquaculture method according to any one of claims 7 to 9.