CN116390650A

CN116390650A - Edible eel culture

Info

Publication number: CN116390650A
Application number: CN202180067858.8A
Authority: CN
Inventors: 稻叶博之; 内山蓝
Original assignee: Ai Zhixian; Kyoritsu Seiyaku Corp
Current assignee: Ai Zhixian; Kyoritsu Seiyaku Corp
Priority date: 2020-10-02
Filing date: 2021-10-01
Publication date: 2023-07-04
Also published as: TW202228527A; JPWO2022071589A1; KR20230075462A; WO2022071589A1

Abstract

The invention aims to provide high-quality edible cultured eels with high lipid content in skeletal muscle. The present invention provides high quality edible cultured eels having a high level of lipid content in skeletal muscle, edible cultured eel populations containing such eel individuals, and the like. According to the lipid content degree in skeletal muscle of eel, the present invention includes edible cultured eel satisfying the formula I when the body of eel is reset to X (g) and the lipid/protein ratio is set to Z. Even after the eels grow to be large, the meat of the eels is not hardened, and the soft tenderness, quality and taste of the meat are still good. Z > -0.001X+1.95 (250 < X < 1,800) (I).

Description

Edible eel culture

Technical Field

The present invention relates to a high-quality edible cultured eel having a high lipid content in skeletal muscle, an edible cultured eel population containing such eel individuals, and the like.

Background

Eel is a generic term for fishes belonging to the genus anguilla of the family anguilla, and 19 species of anguilla japonica, anguilla marmorata, etc. are known in the world. Since ancient times, eel has been used as a food in europe, eastern asia, etc., and especially in japan, has become a popular food material conventionally.

For example, japanese eel (school name "Anguilla japonica") living in the east Asia including Japan is considered to spawn in the vicinity of the Mariana islands in Pacific ocean, and then to become a larvae called Threeds (Leptophalus), which are then transformed into glass eels having a total length of 5 to 6cm and a weight of about 0.2 to 0.3g, which are almost transparent, and which reach coastal areas in east Asia by the flow of black tides. Then, it is presumed that eels (black fries and the like) grow to become due to colonization in inland water areas, coastal areas, brackish water areas and the like, mature for five to more than ten years, and return to the spawning area again. There are almost the same lifestyles as for other eels, although spawning sites, colonisation sites, etc. may be different.

Eel is widely cultivated due to large demand, high profit, etc., and it is said that more than 99% of the total consumption is cultivated eel. At present, the mainstream eel breeding method is a method for capturing natural glass eel which swims to coastal areas as breeding seedlings, releasing the natural glass eel into a breeding pond for breeding, and enabling the natural glass eel to develop. In addition, it has been reported that the complete breeding of the next-generation fries is achieved by growing the fries obtained by artificial hatching into parent eels, but mass production has not been achieved in a commercial scale.

In general, male eels grow slowly after weighing over 300g, and meat becomes hard and the quality and taste become poor. On the other hand, female eels had a growth limit greater than that of male eels, and even if the weight exceeded 300g, the growth did not slow down, and the meat tenderness was maintained, and the quality and taste remained unchanged. However, if raising is performed in a breeding environment at a period from glass eel to small eel, most of male eel becomes, and thus it is difficult to obtain female eel. Therefore, edible eel breeding is carried out on the premise that the edible eel is male eel. That is, in the case where it grows too much, meat becomes hard and quality and taste become poor, thereby losing commercial value, so that the edible cultured eels are usually shipped before their body weight reaches 250 g.

In addition, as a method for female eel, it is known that female eel can be induced by feeding a formula feed with a female hormone (estradiol 17 β) at the time of growing from glass eel to small eel. As a method for female eel without using a hormone, for example, patent document 1 describes a method for promoting female eel by raising eel before sexual differentiation in a water tank in which a hollow housing member is disposed so as to cover the whole body of eel that has entered inside.

Here, soybean isoflavone will be described below as a relevant matter of the present invention.

Soy isoflavones are a general term for flavonoid compounds having isoflavone as a basic skeleton, and are mainly contained in soybean germs and the like in large amounts. Soy isoflavones are classified into 4 types of glycosides (glycoside; structure covalently bound to sugar), aglycones (non-glycoside; structure with sugar moiety of glycoside detached), acetylated forms of glycoside, and malonyl forms of glycoside. There are 3 compounds in each classification, and there are 12 compounds in total for soybean isoflavone. Wherein the 3 kinds of isoflavone are genistin, daidzin and glycitin, and their aglycone (sugar part is separated) is genistein, daidzein and glycitein. The composition and content of each compound vary depending on the type of soybean or the like as a raw material, extraction, purification, treatment methods, and the like. Further, as a method for separating a specific compound in soybean isoflavone, for example, patent document 2 discloses a method for separating high purity genistein from an isoflavone mixture using a solvent.

Soy isoflavones have a chemical structure similar to female hormones (estrogens), also known as phytoestrogens. Furthermore, aglycone type soybean isoflavone has estrogen-like action and is said to be effective for preventing heart disease, climacteric disturbance, osteoporosis, breast cancer, etc.

In addition, non-patent document 1 describes that 55% of the eels are female when fed with 2mg/kg (dry feed) of genistein per day for 100 days, whereas only 15% are female when fed with a relatively high amount of 20mg/kg (dry feed) per day.

Patent document 1 Japanese patent laid-open publication No. 2018-143182

[ patent document 2] Japanese patent laid-open No. 7-173148

[ non-patent document 1]Itai Tzchori,et al, "The influence of phytoestrogens and oestradiol-17β on growth and sex determination in the European eel (Anguilla Anguilla)", aquaculture Research,2004,35,1213-1219.

Disclosure of Invention

Problems to be solved by the invention

As described above, when raising is performed in a breeding environment at a period from glass eel to small eel, most of the male eel is obtained. Since male eels are difficult to grow to medium or more and meat becomes hard and quality and taste are deteriorated as they grow, edible cultured eels circulated in the market are basically small in size and weight of 200 to 250g, and even medium or more edible cultured eels have a low level of lipid content in skeletal muscle and deteriorated quality and taste as compared with natural eels, especially those natural female eels, which are caught and consumed after growing in natural environment.

On the other hand, at present, no technology for producing female eels simply, safely and stably in a breeding environment has been established, and therefore, it has not been possible to produce and supply to the market edible breeding eels with high lipid content in large and medium skeletal muscles and good quality and taste.

Accordingly, an object of the present invention is to provide a high-quality edible cultured eel having a high lipid content in skeletal muscle in medium or above.

Means for solving the problems

The inventors of the present invention succeeded in realizing simple and stable female eel production in a breeding environment by feeding eel feeds or the like containing soybean isoflavone to glass eels and eels in the period of time of small eels, thereby realizing production and mass production of high-quality edible breeding eels with a medium or higher lipid content in skeletal muscle for the first time.

Accordingly, the present invention provides a high-quality edible cultured eel having a high lipid content in skeletal muscle, which is medium or more, and an edible cultured eel population or the like containing such eel individuals.

According to the degree of lipid content in skeletal muscle of eel, the present invention comprises an edible cultured eel which satisfies the following formula I when the body of eel is reset to X (g) and the lipid/protein ratio is set to Z.

Z＞-0.001X+1.95(250＜X＜1,800)(I)

The food-cultured eel also contains a cultured eel having a body weight of more than 250g, and satisfying the following formula II, wherein the BMI is a value obtained according to the following formula A, and the BMI is Y and the lipid/protein ratio is Z.

BMI = body weight (g)/{ full length (mm) } ² (A)

Z＞-Y+2.45(0.2＜Y＜2.0)(II)

Further comprises an edible cultured eel having a body weight of more than 250g, and satisfying the following formula III, wherein a (%) is the gonad weight per unit body weight and b (N) is the breaking load of meat when heat-treated for 10 minutes.

b＜2a+1(0.1＜a＜4)(III)

By allowing the eel to ingest the soybean isoflavone-added eel feed or the like during a predetermined period of time during which the glass eel grows into the small eel, for example, during a period when the sex or sex plasticity is not specified, a simple, efficient and stable female eel production can be realized in a breeding environment. Thus, the production and mass production of high-quality edible cultured eels with high fat tissue ratio in skeletal muscle can be realized.

In the present invention, the term "small eel" means an eel fry which grows larger than a glass eel. For convenience, the eels having a weight of less than 0.5g will be hereinafter referred to as glass eels, and eels having a weight of 0.5g or more will be hereinafter referred to as small eels.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, it is possible to provide high-quality edible cultured eels and the like having a high lipid content in skeletal muscle.

Detailed Description

< edible cultured eel of the present invention >

The invention widely comprises medium-sized or above high-quality edible cultured eels with high lipid content in skeletal muscle.

The edible cultured eel of the present invention has a size of medium or more, specifically, a body weight of preferably more than 250g, more preferably more than 300g, and most preferably more than 350g. Furthermore, the eel weight is preferably less than 1,800g, more preferably less than 1,500g, most preferably less than 1,200g.

Furthermore, the edible cultured eels of the present invention broadly include eels having a body weight within the above-mentioned range and a high level of lipid content in skeletal muscle, i.e., those eels whose meat is not hardened even after growing to a body weight of, for example, more than 250g, and whose soft tenderness, quality and taste remain good.

In the present invention, it was newly found that there is a prescribed correlation between the weight of eel and the lipid/protein ratio, depending on the degree of lipid content in skeletal muscle of eel. Based on this finding, the present invention also includes edible cultured eels satisfying the following formula I' when the body of eels is reset to X (g) and the lipid/protein ratio is set to Z.

Z＞-0.001X+1.95(I’)

In formula I', the range of eel body weight X is as described above.

In the formula I', the lipid/protein ratio Y can be obtained by a known nutrient analysis method or the like. For example, skeletal muscle such as the back and abdomen of eel can be extracted, and the protein and lipid amounts can be measured by known nutrition analysis to calculate the lipid/protein ratio.

In the present invention, it was also newly found that there was a predetermined correlation between BMI (body mass index) value of eel and lipid/protein ratio, depending on the degree of lipid content in skeletal muscle of eel. Based on this finding, the present invention also includes edible cultured eels satisfying the following formula II' when the BMI is defined as a value obtained according to the following formula a, the BMI value is defined as Y, and the lipid/protein ratio is defined as Z.

BMI = body weight (g)/{ full length (mm) } ² (A)

Z＞-Y+2.45(II’)

In formula II', the BMI value Y is preferably greater than 0.2, more preferably greater than 0.5, and most preferably greater than 0.8. Furthermore, the BMI value Y is preferably less than 2.0, more preferably less than 1.8. The lipid/protein ratio is the same as described above.

In the present invention, it has been newly found that the lipid content in skeletal muscle of eel has a predetermined relationship with the breaking load of meat during heat processing. Based on this finding, the present invention also includes edible cultured eels satisfying the following formula III' when the gonad weight per body weight is a (%), and the breaking load of the meat at 10 minutes of heat treatment is b (N).

b＜2a+1(III’)

The gonad weight per body weight, i.e., the gonad weight index a (%), can be calculated by a known method, for example, the gonad is extracted from an individual eel and the weight is measured, divided by the body weight multiplied by 100. In formula III', the gonadal weight index a is preferably greater than 0.1%, more preferably greater than 0.35%. Furthermore, the gonadal weight index a is preferably less than 4%, more preferably less than 3%, most preferably less than 2%.

The breaking load b (N) of the meat at 10 minutes of heat treatment is obtained as an index of hardness of the meat after heat cooking, and can be measured by a known method. For example, one side of eel is cooked at a temperature of 510,000[ deg.C.sec ], and both sides are cooked. The single-sided cooking may be performed at 600 to 1,000 ℃ for 510 to 850 seconds, for example. The cooking apparatus is preferably an electrothermal oven. After the heating and cooking are performed, the breaking load b is measured for a specific portion (abdomen, etc.) of the meat after the heating and cooking by an elastic measuring device such as a rheometer.

In addition, in the case of eating and breeding eel having a high lipid content in the skeletal muscle of large and medium size, the adipose tissue in the skeletal muscle of the back or abdomen is in a net-like local state.

Here, the term "a state in which adipose tissue is present locally in a net" means that adipose tissue is deposited in an irregular net shape in the entire muscle, and the deposition rate is higher than that of a standard eel, and adipose tissue is extremely fine. Although different in species, it corresponds to grade 4 and grade 5 of the meat quality grade in the beef carcass trade criteria defined by the japanese meat grading association of the corporate community. Of the eels which are the subjects of the present invention, those which are more remarkable in the body side muscles can be said to correspond to eels having an adipose tissue area ratio (adipose tissue area/total cross-sectional area) of 35% or more in the body side muscles. The fat tissue area ratio of the body side muscle on the abdominal side is generally higher than that on the dorsal side, and 37% or more of the body side muscle on the abdominal side can be used as an index.

The type of eel to be the subject of the present invention is not particularly limited as long as it belongs to the genus eel of the family eel. For example, japanese eel (school name "Anguilla japonica"), anguilla marmorata (school name "Anguilla marmorata"), european eel (school name "Anguilla anguilla"), american eel (school name "Anguilla rostrata") and the like are also subjects. In the present invention, the eel is most preferably Japanese eel.

< population of edible cultured eel according to the present invention >

As described above, since eels in the raised collar are basically male eels, there are no large concentrations of medium-sized or medium-sized eels with a high level of lipid in skeletal muscle in the market. That is, according to the present invention, such edible cultured eels can be concentrated in the market for the first time, and the present invention includes all of the plurality of populations formed by the individual edible cultured eels described above.

In view of the fact that the female eel production rate in the breeding environment is substantially 0%, for example, an edible breeding eel population containing the edible breeding eel individuals described above at a rate of 12% or more, formed of 10 or more, more preferably an edible breeding eel population containing the edible breeding eel individuals described above at a rate of 15% or more, and most preferably an edible breeding eel population containing the edible breeding eel individuals described above at a rate of 25% or more, is not likely to be produced before the present invention, and is therefore included in the scope of the edible breeding eel population of the present invention.

< production method of edible cultured eel and the like according to the present invention >)

The production method of the edible cultured eel or the like of the present invention is not particularly limited. For example, these edible cultured eels and the population thereof can be produced and mass-produced by taking an eel feed or an eel femaleization inducer, which will be described later, in the period of glass eels and/or small eels. The present invention is not limited narrowly to production and mass production by the methods shown below.

The male/female differentiation is performed at a predetermined period between the growth of the eel from the glass eel to the small eel (for example, during the growth period of 0.2g to 30g in weight), and when the growth reaches the level of 30g in weight or more, the male/female differentiation can be performed by observing the gonad morphology. Furthermore, by taking in these eel feeds or eel females before and after the time of male and female differentiation, for example, in the time of glass eel and/or small eel, it is possible to reliably and efficiently induce eel females, and thereby it is possible to produce and mass-produce high-quality edible cultured eels (populations) having a medium or higher lipid content in skeletal muscle.

The method for making eel ingest eel feed or eel feminization inducer is not particularly limited. For example, they may be fed with a feed for eel or an inducer for eel femaleization, they may be taken separately, they may be administered directly to an individual eel, or the like.

The period for taking in the eel feed or the eel femaleization inducer is not particularly limited as long as it includes a period of male and female differentiation and a period before and after the male and female differentiation. For example, when the eel is continuously taken in the feed or the eel femaleization inducer for eel during 2 to 6 months of the period of glass eel and/or small eel, the eel can be reliably and efficiently induced with a high possibility of being femaleized.

The frequency of intake of the eel feed or the eel femaleization inducer into the eel is not particularly limited as long as the intake can be continued without interruption during the period of intake or the like. For example, when eel is ingested for 3 to 7 days per week, the eel can be reliably and efficiently induced to be female. The amount taken daily can be further divided into 2 to 3 feeds depending on the growth degree of eel, for example, in the period of glass eel to small eel (for example, weight of 0.2g to 20 g), and the amount taken daily can be fed once in the period of small eel (for example, weight of 20g to 30 g).

< feed for eel >)

In the production of the edible cultured eel (or population thereof) of the present invention, for example, eel feed can be used: eel feed containing soybean isoflavone in an amount of 0.05 wt% or more based on dry matter, eel feed containing soybean isoflavone aglycone in an amount of 0.05 wt% or more based on dry matter, eel feed containing genistein in an amount of 0.006 wt% or more based on dry matter, etc.

By adding soybean isoflavone (or soybean isoflavone aglycone, or one or more specific compounds such as genistein) to the eel feed, the feed can be fed for a certain period of time during which the eel is glass and/or small eel, and the female eel can be induced, thereby enabling production and mass production of high-quality edible cultured eel having a medium or higher fat tissue ratio in skeletal muscle.

The formula feed used as the feed for eel is often fed to eel after being kneaded into paste by adding water, feed oil (fish oil) and the like.

In the eel feed, the soybean isoflavone is preferably contained in an amount of 0.05 wt% or more, more preferably 0.2 wt% or more, and most preferably 1.0 wt% or more, based on the dry feed (hereinafter, the same applies) ratio, that is, based on the weight of the feed before the preparation (addition of water or the like) in use. The upper limit of the soybean isoflavone content is not particularly limited, but is preferably 20% by weight or less, more preferably 8.0% by weight or less, and most preferably 4.0% by weight or less from the viewpoint of feed efficiency.

The soybean isoflavone is not particularly limited, and can be widely used. For example, an off-the-shelf product may be used, or soybean isoflavone prepared by extracting, purifying, treating from raw soybean or the like by a known method may be used.

From other points of view, in the eel feed, the soybean isoflavone aglycone is preferably contained in an amount of 0.05% by weight or more, more preferably 0.2% by weight or more, and most preferably 1.0% by weight or more, based on the dry matter, that is, based on the weight of the feed before the preparation (addition of water or the like) in use. The upper limit of the soybean isoflavone aglycone content is not particularly limited, but is preferably 20% by weight or less, more preferably 8.0% by weight or less, and most preferably 4.0% by weight or less from the viewpoint of feed efficiency or the like. The term "soybean isoflavone aglycone" is a non-sugar moiety in soybean isoflavone (hereinafter, the same applies), and the weight of the non-sugar moiety can be obtained by, for example, converting the ratio of the molecular weight of the glycoside to the molecular weight of the aglycone based on the weight of soybean isoflavone to be added, and can be obtained by analyzing the resultant by a known test method.

From another viewpoint, in the eel feed, when the weight of the feed before the preparation (addition of water or the like) in terms of the dry matter is 100%, genistein is preferably contained in an amount of 0.006% by weight or more, more preferably 0.02% by weight or more, and most preferably 0.1% by weight or more. The upper limit of the genistein content is not particularly limited, but is preferably 5.0 wt% or less, more preferably 2.0 wt% or less, and most preferably 1.0 wt% or less from the viewpoint of feed efficiency or the like.

The method for adding genistein to eel feed is not particularly limited. For example, genistein can be contained in eel feed by adding genistein-containing soybean isoflavone to eel feed; genistein can also be directly added into eel feed; the soybean isoflavone or genistein may also be contained in advance in the production stage of the feed.

Genistein is not particularly limited, and any known genistein can be used. For example, a ready-made product, soybean isoflavone containing genistein as it is, genistein isolated or purified by extraction, purification, treatment from soybean isoflavone or the like by a known method, genistein obtained by separation, extraction, fermentation or the like from beans or processed products thereof by a known method, and genistein synthesized by a known method may be used. For example, in the case where the soybean isoflavone contains genistein in an amount of 10% by weight or more, there are the following advantages: is easy to obtain, manufacture and prepare, and can reliably and efficiently induce female eel, thereby being capable of producing and mass-producing high-quality edible cultured eel with medium or higher fat tissue ratio in skeletal muscle.

In addition, the genistein herein also includes a pharmacologically acceptable salt thereof and a derivative of genistein, as long as the effect of inducing female eel is maintained.

The eel feed contains at least soybean isoflavone (or soybean isoflavone aglycone, or one or more specific compounds such as genistein), and optionally other ingredients, components, etc.

For example, the formulation and the component composition other than soybean isoflavone (or soybean isoflavone aglycone, or one or more specific compounds thereof) in the eel feed may be the same as those of the commonly used formulation feed. The formula feed is a feed in which nutrients necessary for eel growth are mixed in a proper ratio, for example, 50% by weight or more of fish meal in terms of the ratio in dry matter, and further contains starch, calcium phosphate, salt, yeast, herbal extract, etc.

The fish meal in the formula feed may be widely used, and is not particularly limited, and may be, for example, a powder obtained by processing sardine, mackerel, herring, horse mackerel, and the like. The fish meal may be fish meal of other fish species, or may be a mixed powder of fish meal of a plurality of fish species. The type, growth state, cost, etc. of eel can be appropriately selected.

In addition, for example, components for improving the growth efficiency of eel such as lactic acid bacteria, butyric acid bacteria, digestive enzymes, dried vegetables and the like may be suitably contained.

< inducer for eel feminization >)

In the production of the edible cultured eel (or population thereof) of the present invention, for example, an eel femaleization inducer may be used: an eel femaleization inducer containing soybean isoflavone of 10mg/kg or more (weight of eel, hereinafter the same) per day as an active ingredient, an eel femaleization inducer containing soybean isoflavone aglycone of 10mg/kg or more per day as an active ingredient, an eel femaleization inducer containing genistein of 1.2mg/kg or more per day as an active ingredient, and the like.

By incorporating soybean isoflavone (or soybean isoflavone aglycone, or one or more specific compounds such as genistein) as an active ingredient into an eel female inducer, eel female can be induced reliably and efficiently in a glass eel and/or a small eel stage by taking soybean isoflavone or the like, and thus a high-quality edible cultured eel having a medium or higher fat tissue ratio in skeletal muscle can be produced and mass produced.

In the case of the formula feed, the standard of the feed amount is usually 5 to 8% of the weight of the glass eel to the small eel (for example, the weight of the small eel is on the order of 0.2g to 20 g), and 2 to 3% of the weight of the small eel (for example, the weight of the small eel is on the order of 20g to 30 g) depending on the growth condition. The amount of soybean isoflavone to be fed is preferably at least 10mg/kg per day, more preferably at least 40mg/kg per day, and most preferably at least 200mg/kg per day, based on 2% of the body weight. From the viewpoint of feed efficiency, the amount of soybean isoflavone to be fed is preferably 16g/kg or less per day, more preferably 6.4g/kg or less per day, and most preferably 3.2g/kg or less per day, based on 8% of the body weight.

For example, according to the growth degree of eel, soybean isoflavone of 25mg/kg to 16g/kg (eel body weight) is taken daily in the period of glass eel to small eel (for example, the body weight is slightly more than 0.2g and slightly less than 20 g), more preferably 100mg/kg to 6.4g/kg, most preferably 500mg/kg to 3.2g/kg daily; in the period of about 20g or more to about 30g of the small eel, 10mg/kg to 16g/kg (eel weight) of soybean isoflavone, more preferably 40mg/kg to 6.4g/kg, and most preferably 200mg/kg to 3.2g/kg are taken daily.

From another viewpoint, in the eel femaleization inducer, the feed amount is set to 2% of the body weight, preferably 10mg/kg or more of soybean isoflavone aglycone is taken daily, more preferably 40mg/kg or more is taken daily, and most preferably 200mg/kg or more is taken daily. From the viewpoint of feed efficiency, the intake amount of soybean isoflavone aglycone is preferably 16g/kg or less per day, more preferably 6.4g/kg or less per day, and most preferably 3.2g/kg or less per day, with the feed amount being 8% of the body weight.

For example, according to the growth degree of eel, for example, 25mg/kg to 16g/kg (eel weight) of soybean isoflavone aglycone is taken daily in the period of glass eel to small eel (for example, the weight is slightly more than 0.2g and slightly less than 20 g), more preferably 100mg/kg to 12g/kg, most preferably 500mg/kg to 8g/kg daily; in the period of about 20g or more to about 30g of the small eel, 10mg/kg to 16g/kg (eel weight) of soybean isoflavone aglycone is taken daily, more preferably 40mg/kg to 6.4g/kg daily, and most preferably 200mg/kg to 3.2g/kg daily.

From another aspect, in the eel femaleization inducer, the feed amount is set to 2% of the body weight, preferably 1.2mg/kg or more of genistein is taken daily, more preferably 4.0mg/kg or more, and most preferably 20mg/kg or more is taken daily. From the viewpoint of feed efficiency, the amount of fed is 8% by weight, and the amount of genistein taken is preferably 4.0g/kg or less per day, more preferably 1.6g/kg or less per day, and most preferably 0.8g/kg or less per day.

For example, according to the growth degree of eel, for example, 3mg/kg to 4.0g/kg (eel body weight) of genistein is taken daily in the period of glass eel to small eel (for example, the body weight is slightly 0.2g or more and slightly less than 20 g), more preferably 10mg/kg to 1.6g/kg, most preferably 50mg/kg to 800mg/kg daily; the genistein is preferably taken at a daily dose of 1.2 to 1.5 mg/kg (eel body weight), more preferably at a daily dose of 4 to 600mg/kg, most preferably at a daily dose of 20 to 300mg/kg, in the period of about 20g or more to about 30g of eel body weight.

The eel femaleization inducer may be appropriately added with excipients, lubricants, binders, disintegrants, solvents, dissolution aids, suspending agents, buffers, isotonic agents, preservatives, antioxidants, pH adjusters, dispersants, colorants, antifoaming agents and the like according to purposes, uses, dosage forms and the like.

Preferable examples of the excipient include lactose, white sugar, D-mannitol, starch, crystalline cellulose, and light anhydrous silicic acid.

Preferable examples of the lubricant include magnesium stearate, calcium stearate, talc, and colloidal silica.

As preferable examples of the binder, crystalline cellulose, white granulated sugar, D-mannitol, dextrin, hydroxypropyl cellulose, hydroxypropyl methylcellulose, polyvinylpyrrolidone, and the like can be used.

As preferable examples of the disintegrating agent, starch, carboxymethyl cellulose, calcium carboxymethyl cellulose, croscarmellose sodium, sodium carboxymethyl starch and the like can be used, for example.

As preferable examples of the solvent, water for injection, alcohol, propylene glycol, polyethylene glycol (MACROCOL), sesame oil, corn oil and the like can be used.

As preferable examples of the dissolution aid, polyethylene glycol, propylene glycol, D-mannitol, benzyl benzoate, ethanol, triaminomethane, cholesterol, triethanolamine, sodium carbonate, sodium citrate, and the like can be used, for example.

Preferable examples of the suspending agent include surfactants (e.g., stearyl triethanolamine, sodium lauryl sulfate, lauryl aminopropionic acid, lecithin, benzalkonium chloride, benzethonium chloride, and glyceryl monostearate), hydrophilic polymers (e.g., polyvinyl alcohol, polyvinylpyrrolidone, sodium carboxymethyl cellulose, methylcellulose, hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose), and the like.

As preferable examples of the buffer, for example, a buffer such as phosphate, acetate, carbonate, citrate, tartrate, tris, HEPES and the like can be used.

As preferable examples of the isotonic agent, sodium chloride, glycerol, D-mannitol and the like can be used.

Examples of the agents for the purpose of preservation include thimerosal, parabens, phenoxyethanol, chlorobutanol, benzyl alcohol, phenethyl alcohol, dehydroacetic acid, sorbic acid, various other preservatives, antibiotics, and synthetic antibiotics.

As preferable examples of the antioxidant, sulfite, ascorbic acid, and the like can be used.

Preferable examples of the pH adjuster include acids such as hydrochloric acid, carbonic acid, acetic acid, citric acid, phosphoric acid, boric acid, and sulfuric acid, alkali metal hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, and magnesium hydroxide, alkali metal carbonates and hydrogencarbonates such as sodium carbonate, alkali metal acetates such as sodium acetate, alkali metal citrates such as sodium citrate, bases such as tromethamine (tromamol), monoethanolamine, and diisopropanolamine.

Preferable examples of the dispersant include sodium carboxymethyl cellulose, hydroxypropyl methyl cellulose, polyvinylpyrrolidone, and Polysorbate (Polysorbate) 80.

Preferred examples of the coloring agent include caramel color, gardenia color, anthocyanin color, annatto color, red pepper color, safflower color, monascus color, carotene color, carotenoid color, flavonoid color, cochineal color, amaranth (red No. 2), erythrosin (red No. 3), allura red AC (red No. 40), carmine (red No. 102), fluorescent pink (red No. 104), rose bengal (red No. 105), acid red (red No. 106), tartrazine (yellow No. 4), sunset yellow FCF (yellow No. 5), fast green FCF (green No. 3), brilliant blue FCF (blue No. 1), indigo carmine (blue No. 2), copper chlorophyll, sodium copper chlorophyll, and the like.

Examples of the defoaming agent include dimethicone (dimethicone), simethicone (Simethicone), silicone emulsion, sorbitan sesquioleate, and nonionic substances.

In addition to the above, the present agent may suitably contain auxiliary components such as light-absorbing pigments (riboflavin, adenine, adenosine, etc.), chelating agents and reducing agents (vitamin C, citric acid, etc.) for stabilization, carbohydrates (sorbitol, lactose, mannitol, starch, sucrose, glucose, dextran, etc.), casein digests, various vitamins, lactic acid bacteria, butyric acid bacteria, digestive enzymes, dried vegetables, etc., as storage and efficacy aids.

Example 1

In example 1, it was investigated whether soybean isoflavone could be used to induce female eel.

The glass eels (average weight: 0.4 g) of undetermined sex were placed in 150L FRP water tanks, fed with the formula feed containing soybean isoflavone at each ratio in a saturated state, and fed at 28℃in water.

The feeding frequency of the formula feed added with the soybean isoflavone is 5 times per week. The initial two months of feed was 7-8% of body weight, followed by about 2.5% of body weight.

After about 6 months from the start of feeding, individuals who had grown into small eels weighing about 30g or more were sampled appropriately, and a determination of the sex was made.

The sex determination is to determine that an individual having an ovary is female and an individual having a testis is male based on morphological observation of gonads.

The results are shown in tables 1 and 2. In each table, "the number of individuals of the sampled eel," the ratio of soybean isoflavone addition "means the ratio of the soybean isoflavone addition amount (wt%) when the weight of the formula feed before soybean isoflavone addition and before preparation at the time is 100%, the" aglycone content ratio "means the ratio of the soybean isoflavone aglycone content weight (wt%) when the weight of the formula feed before soybean isoflavone addition and before preparation at the time is 100%, the" genistein content ratio "means the ratio of the genistein content weight (wt%) when the weight of the formula feed before soybean isoflavone addition and before preparation at the time is 100%, and the" ratio of female "means the ratio of female in the sampled individual number. In addition, "soybean isoflavone aglycone containing weight" means the weight of the non-sugar part in the added soybean isoflavone, and an analytical value obtained based on a known test method is used. The "control" is the result of feeding the normal formula feed without soybean isoflavone instead of the above.

TABLE 1

TABLE 2

As shown in Table 1, femaleization of eel was induced by feeding eel with soybean isoflavone in an amount of 1 wt% or more in the feed for eel at the time of glass eel to small eel. As shown in table 2, when the eel feed was fed with the feed containing 0 to 0.040 wt% of aglycone based on the weight of the feed, all individuals differentiated to males, whereas when the aglycone content was 0.100 wt% or more, 46% of individuals were induced to females, 0.336 wt% of individuals were induced to females, and 1.076 wt% or more, all individuals were induced to females. From another viewpoint, attention is paid to genistein contained in a feed by adding soybean isoflavone, and when feeding a feed for eel having a genistein content ratio of 0 to 0.004 wt% in the period of glass eel to small eel, all individuals are differentiated into males, when the genistein content ratio is 0.01 wt%, 46% of individuals are induced into females, when 0.031 wt%, 95% of individuals are induced into females, and when the genistein content ratio is 0.155 wt% or more, all individuals are induced into females.

According to the feeding amount of each of the experiments, the amount of soybean isoflavone was about 700 to 800mg/kg body weight for the first two months, and the amount of soybean isoflavone was about 250mg/kg body weight for the second two months, in terms of conversion to 7 to 8% by weight for the first two months and about 2.5% by weight for the second month, when the soybean isoflavone addition ratio was 1% by weight. Similarly, when the content ratio of aglycone to the weight of the feed is 0.100% by weight, the amount of aglycone taken in each of the first two months is about 70.0 to 80.0mg/kg body weight, and thereafter the amount of aglycone taken in each of the two months is about 25.0mg/kg body weight; in the case where the content ratio of the aglycone relative to the weight of the feed is 0.336 wt%, the intake amount of the aglycone is about 235.2 to 268.8mg/kg body weight for each of the first two months, and thereafter, the intake amount of the aglycone is about 84.0mg/kg body weight for each of the two months; in the case where the content ratio of aglycone to the weight of the feed is 1.076 wt%, the amount of aglycone taken in each of the first two months is about 753.2 to 860.8mg/kg body weight, and thereafter the amount of aglycone taken in each of the two months is about 269.0mg/kg body weight. Further, in the case where the genistein content ratio is 0.01% by weight, the amount of genistein taken up each time for the first two months is about 7 to 8mg/kg body weight, and thereafter the amount of genistein taken up each time is about 2.5mg/kg body weight; in the case where the genistein content ratio is 0.031 wt%, the amount of genistein taken up each time for the first two months is about 21.70 to 24.8mg/kg body weight, and thereafter about 7.75mg/kg body weight; in the case where the genistein content ratio is 0.155% by weight, the uptake amount of genistein per time for the first two months is about 108.5 to 1,240mg/kg body weight, and thereafter the uptake amount of genistein per time is about 38.75mg/kg body weight.

Example 2

In example 2, male and female were compared based on analysis of the overall length and weight of eel and nutrient content.

Full length and body weight were measured for eels not induced to be feminized with soy isoflavones (male eels, n=7) and eels induced to be feminized with soy isoflavones (female eels, n=5), respectively. Then, for each individual, a BMI value was calculated using the above formula a.

Next, skeletal muscles of the back and abdomen were extracted, analyzed for nutritional components, the protein mass and the lipid mass were measured, and the lipid/protein ratio in skeletal muscles of the back and abdomen was calculated.

FIG. 1 is a graph comparing body weight and lipid/protein ratio between male and female. In the figure, the horizontal axis represents body weight (g), and the vertical axis represents lipid/protein ratio.

As shown in fig. 1, when the body of eel is reset to X (g) and the lipid/protein ratio is Z, the female and male eel can be clearly identified by using the following formula i″ as a boundary.

Z＝-0.001X+1.95(I”)

FIG. 2 is a graph comparing BMI values and lipid/protein ratios between females and males. In the figure, the horizontal axis represents the BMI value, and the vertical axis represents the lipid/protein ratio.

As shown in fig. 2, when the BMI value is Y and the lipid/protein ratio is Z, the male and female can be clearly identified by using the following formula ii″ as a boundary for the cultured eel.

[ number 10]

Z＝-Y+2.45(II”)

Example 3

In example 3, the gonadal weight index (GSI; gonadal weight/body weight) of eel that was induced to female with soybean isoflavone was calculated, and the relationship between the gonadal weight index and the hardness of cooked meat was evaluated.

First, weights of eels (male eels, n=12, weights of 200 to 350 g) not having been subjected to the soybean isoflavone-induced female formation and eels (female eels, n=15, weights of 200 to 530 g) having been subjected to the soybean isoflavone-induced female formation were measured separately, and genitals were extracted to measure the weights. Furthermore, the gonadal weight per body weight (unit:%) was calculated as the gonadal weight index.

As a result, the gonad weight per unit weight of all male eels was 0.35% or less, whereas the gonad weight per unit weight of all female eels whose femaleization was induced by soybean isoflavone was more than 0.35%.

Then, each eel was cut along the center of the ventral side, each eel was subjected to heat treatment at 850℃for 600 seconds on the skin side and 600 seconds on the meat side using an electric oven 3H-210 (manufactured by Higo Griller Co.), each dried eel was prepared, the skin was peeled off, fish pieces having a width of about 1cm were prepared from 3 portions on the ventral side, and then the breaking load at the time of cutting the meat at the tip portion of each wedge-shaped fitting was measured by a rheometer for 3 samples of 1 individual, and the average value was used as an index of the hardness of the meat.

Fig. 3 is a graph showing the relationship between the gonadal weight index and the breaking load of the ventral meat after heat cooking. In FIG. 3, the horizontal axis represents the gonadal weight index (GSI; gonadal weight per body weight:%) of eel, and the vertical axis represents the breaking load (unit: N) of the belly side meat after cooking by heating.

As shown in fig. 3, when the gonad weight index is a (%) and the breaking load of the abdominal side meat after the heating and cooking is b (N), the male and female eel can be clearly identified by using the following formula III "as a boundary.

Y＝2X+1(III”)

Drawings

FIG. 1 is a graph showing comparison of body weight and lipid/protein ratio between the male and female in example 2.

FIG. 2 is a graph showing comparison of BMI values and lipid/protein ratios between the male and female in example 2.

Fig. 3 is a graph showing the relationship between the gonadal weight index and the breaking load of the ventral meat after the heat cooking in example 3.

Claims

1. An edible cultured eel satisfying the following formula I when the body of the eel is reset to X (g) and the lipid/protein ratio is set to Z:

Z＞-0.001X+1.95(250＜X＜1,800) (I)。

2. an edible eel for breeding with weight of more than 250g

When a value obtained according to the following formula a is defined as BMI, and the BMI value is defined as Y and the lipid/protein ratio is defined as Z, the following formula II is satisfied:

BMI = body weight (g)/{ full length (mm) } ² (A)

Z＞-Y+2.45(0.2＜Y＜2.0) (II)。

3. An edible eel for breeding with weight of more than 250g

When the gonadal weight per unit body weight is a (%) and the breaking load of meat at the time of heat treatment for 10 minutes is b (N), the following formula III is satisfied:

b＜2a+1(0.1＜a＜4) (III)。

4. a food-cultured eel according to any one of claims 1 to 3, wherein adipose tissue in skeletal muscle of the back or abdomen is present locally in a net shape.

5. The edible cultured eel according to any one of claims 1 to 4, wherein during a glass eel and/or a small eel period,

the eel feed containing soybean isoflavone in an amount of 0.05 wt% or more based on the dry matter is ingested.

6. An edible cultured eel population formed from 10 or more, containing the edible cultured eel individual according to any one of claims 1 to 5 at a ratio of 12% or more.