JP-7855833-B2 - Eel farmed for consumption

Inventors

• 稲葉 博之
• 内山 藍

Assignees

• 愛知県
• 共立製薬株式会社

Dates

Publication Date

20260511

Application Date

20211001

Priority Date

20201002

Claims (4)

1. A group of farmed eels for food consisting of 10 or more individuals, Weight of 530g or less, and, A group of farmed eels for food in which 95% or more of the eels satisfy the following formula I, where X is the weight of the eel (g) and Z is the lipid/protein ratio.
2. A group of farmed eels for food consisting of 10 or more individuals, If the weight is greater than 250g but less than or equal to 530g , A group of farmed eels for food in which 95% or more of the eels satisfy the following formula II, with Y being the BMI value calculated by formula A below and Z being the lipid/protein ratio.
3. A group of farmed eels for food consisting of 10 or more individuals, If the weight is greater than 250g but less than or equal to 530g , A group of farmed eels for food containing 95% or more eels that satisfy the following formula III, where a (%) is the weight of the gonads per unit body weight and b (N) is the breaking load of the flesh during 10 minutes of heat processing.
4. A group of farmed eels for food according to any one of claims 1 to 3, wherein the adipose tissue in the skeletal muscle of the back or abdomen of the farmed eel for food is localized in a reticular pattern.

Description

This invention relates to high-quality farmed eels for food with a high lipid content in their skeletal muscle, and to groups of farmed eels for food containing such eel individuals. Eels are a general term for fish belonging to the genus Anguilliformes in the family Anguilliidae, with 19 species known worldwide, including the Japanese eel, giant eel, and European eel. They have been consumed as food in Europe, East Asia, and other regions since ancient times, and are a particularly popular and traditional food in Japan. For example, the Japanese eel (scientific name "Anguilla japonica"), which inhabits all of East Asia, including Japan, is thought to spawn near the Mariana Islands in the Pacific Ocean. After developing into a larva called a leptocephalus, it metamorphoses into a nearly transparent glass eel about 5-6 cm in length and weighing 0.2-0.3 g, which then travels along the Kuroshio Current to the coastal areas of East Asia. There, it is believed to settle and grow in freshwater, coastal, and brackish water areas, becoming a small eel (such as a black eel), and then mature over a further 5-10 years before migrating again to its spawning grounds. Other eel species generally follow a similar lifestyle, although their spawning and settlement locations may differ. Due to high demand and profitability, eel farming is widespread, with over 99% of total eel consumption attributed to farmed eels. The current mainstream method of eel farming involves capturing wild glass eels that migrate to coastal areas as seed stock, releasing them into aquaculture ponds, and raising them to maturity. While success in complete aquaculture—raising juvenile eels from artificial hatching to adult eels and then producing the next generation of juveniles—has been reported at the laboratory level, it has not yet been achieved in commercial mass production. Generally, male eels slow down in growth once they exceed 300g in weight, and their flesh becomes tougher, resulting in a decline in quality and taste. On the other hand, female eels have a greater growth limit than male eels; their growth does not slow down even beyond 300g, and their flesh remains tender, maintaining quality and taste. However, when eels are raised in aquaculture environments from the glass eel stage to the juvenile stage, most of them become male, making it difficult to obtain female eels. Therefore, farmed eels for consumption are farmed and shipped on the assumption that they will be male. In other words, if they grow too large, their flesh becomes tough, their quality and taste decline, and they lose their commercial value, so farmed eels for consumption are usually shipped before they reach a weight of 250g. It is known that feminization of eels can be induced by adding the female hormone (estradiol 17β) to compound feed during the period when eels grow from glass eels to juvenile eels. In addition, as a means of feminizing eels without using hormones, for example, Patent Document 1 describes a method of promoting feminization by raising eels before sexual differentiation in a tank equipped with a hollow containment member that completely covers the entire body of the eel that enters it. Herein, the details of soy isoflavones related to the present invention will be explained below. Soy isoflavones are a general term for flavonoid compounds with isoflavones as their basic structure, mainly found in the germ of soybeans. Soy isoflavones are classified into four types: glycosides (a structure covalently bonded to sugar), aglycones (non-glycosides; a structure in which the sugar portion of the glycoside has been removed), acetylated glycosides, and malonylated glycosides. Three compounds are known in each classification, resulting in a total of 12 known compounds as soy isoflavones. Of these, the three glycoside soy isoflavones are genistin, daidzin, and glycitin, while their aglycone forms (with the sugar portion removed) are genistein, daidzein, and glycitein, respectively. The composition and content of each compound vary depending on the type of raw soybean, extraction, purification, and processing methods. Furthermore, as a means of separating specific compounds in soy isoflavones, 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 the female hormone estrogen and are also called phytoestrogens. Furthermore, soy isoflavones in the aglycone form have estrogen-like effects and are believed to be effective in preventing heart disease, menopausal symptoms, osteoporosis, and breast cancer. Furthermore, Non-Patent Document 1 states that when European eels were fed 2 mg/kg (dry feed) of genistein for 100 days, 55% became female, whereas when they were fed a higher amount of 20 mg/kg (dry feed), only 15% became female. Japanese Patent Publication No. 2018-143182 Japanese Patent Application Publication No. 7-173148 Itai Tzchori,