Potato protein composition, and feed composition for aquatic animals which contains said potato protein composition

Abstract

The purpose of the present embodiment is to provide: a protein source having high feed ingestion properties and digestibility; and a feed composition for aquatic animals, which contains the protein source. Specifically, the present embodiment relates to a potato protein having a potato glycoalkaloid content of 300 ppm or less and a free amino acid content of 10,000-75,000 ppm.

Description

Potato protein composition and aquatic animal feed composition containing said potato protein composition

[0001] The present disclosure relates to potato protein compositions and aquatic animal feed compositions containing the potato protein compositions.

[0002] Traditionally, fish meal has often been used as the main protein source for animal feeds, such as aquatic animal feeds, because of its high protein content, good amino acid balance, and good feedability and digestibility, which contributes greatly to animal weight gain.

[0003] However, factors such as climate change, overfishing of wild fish, and an increase in the global trade of fishmeal have caused fishmeal prices to soar, putting pressure on aquaculture businesses. Therefore, there is a need for a stable, inexpensive protein source that is high in protein, has a good amino acid balance, is easy to feed and digest, and can be supplied in place of fishmeal. The "Green Food System Strategy" promoted by the Ministry of Agriculture, Forestry and Fisheries also calls for a fishmeal substitution rate of 80% or more in freshwater fish feed and 50% or more in saltwater fish feed.

[0004] Given these circumstances, plant proteins, which have relatively stable production volumes and prices, are expected to replace fishmeal as an alternative protein source. Among these, soybean oil meal, corn gluten meal, and potato protein have attracted attention due to their high protein content. However, soybean oil meal has a low content of the essential amino acid methionine, and corn gluten meal has a low content of the essential amino acid lysine, making them incapable of replacing fishmeal alone. On the other hand, potato protein contains sufficient amounts of all essential amino acids. However, like other plant proteins (including soybean oil meal and corn gluten meal), potato protein's molecular weight distribution is higher than that of fishmeal, and its free amino acid content is also low. Therefore, potato protein has the disadvantage of being inferior in feed intake (daily feeding rate) and digestibility (feed efficiency) compared to fishmeal. Furthermore, it contains potato glycoalkaloids, an antinutritional factor that inhibits feed intake (daily feeding rate) in fish.

[0005] To date, methods proposed to improve the feedability (daily feeding rate) and digestibility (feed efficiency) of potato protein have included using potato protein with a reduced potato glycoalkaloid content or potato protein with physical properties controlled within a certain range as a feed ingredient.

[0006] For example, Patent Document 1 discloses a potato protein with a reduced potato glycoalkaloid content, and Patent Document 2 discloses a potato protein that exhibits high feed efficiency by controlling the endothermic and exothermic temperatures measured with a differential scanning calorimeter within a certain range.

[0007] JP 2020-5606 A

[0008] Although the potato protein described in Patent Documents 1 and 2 can replace approximately 30% of fish meal, increasing the fish meal replacement rate further reduces feedability and digestibility. Therefore, there has been a need for further development of alternative proteins that can be used in place of fish meal.

[0009] Therefore, an object of the present disclosure is to provide a protein source that can be used as a high substitute for fish meal, i.e., can be used at a high rate in place of fish meal, and can exhibit high feedability and digestibility.

[0010] The present inventors have conducted extensive research to solve the above-mentioned problems and have surprisingly found that a potato protein composition having a potato glycoalkaloid content and a free amino acid content within a specified range exhibits high feedability (daily feeding rate) and digestibility (feed efficiency) even when used in high proportions in place of fish meal, leading to the present disclosure.

[0011] That is, example embodiments of the present invention include the following: (1) A potato protein composition having a potato glycoalkaloid content of 300 ppm or less in the dry matter and a free amino acid content of 10,000 ppm or more and 75,000 ppm or less in the dry matter. (2) The potato protein composition according to (1), having a crude protein content of 70% by weight or more in the dry matter. (3) The potato protein composition according to (1) or (2), having a potato-derived crude protein content of 90% by weight or more in the crude protein in the potato protein composition. (4) The potato protein composition according to any one of (1) to (3), which contains fermented potato protein. (5) A feed composition for aquatic animals containing the potato protein composition according to any one of (1) to (4). (6) An aquatic animal feed composition containing potato protein, wherein the potato glycoalkaloid content in the dry matter is 100 ppm or less and the free amino acid content in the dry matter is 4,000 ppm or more and 35,000 ppm or less. (7) The aquatic animal feed composition according to (6), wherein the crude protein content in the dry matter is 30% by weight or more. (8) The aquatic animal feed composition according to (6) or (7), wherein the proportion of potato-derived crude protein in the crude protein in the aquatic animal feed composition is 40% by weight or more. (9) The aquatic animal feed composition according to any one of (6) to (8), further comprising fish meal, wherein the fish meal content is 50% by weight or less. (10) The aquatic animal feed composition according to (9), wherein the fish meal content is 30% by weight or less.

[0012] This specification includes the disclosure of Japanese Patent Application No. 2024-045234, from which the present application claims priority.

[0013] According to the present disclosure, it is possible to provide a protein source that can exhibit high feedability and digestibility even when used at a high rate in place of fish meal.

[0014] Hereinafter, embodiments of the present invention will be described in detail.

[0015] <Potato Protein Composition> This embodiment is a potato protein composition having a potato glycoalkaloid content in the dry matter of 300 ppm or less and a free amino acid content in the dry matter of 10,000 ppm or more and 75,000 ppm or less.

[0016] As used herein, "potato protein" refers to a protein derived from potatoes, extracted and separated from potatoes. Potato proteins are usually polypeptides with a molecular weight of 1,500 or more, typically 5,000 or more. Potato proteins may be chemically modified, for example, with a sugar chain, as appropriate. Potato proteins are not limited to those in their natural state, and may also be denatured. For example, potato proteins can be obtained by extraction and separation from the juice obtained as a by-product during the production of starch from potatoes.

[0017] A potato protein composition refers to a composition that contains potato protein extracted and separated from potatoes and may optionally contain water, impurities, and the like. Substances other than protein components typically have a molecular weight of 5,000 or less, and preferably have a molecular weight of 1,500 or less. Furthermore, the potato protein composition may contain one type of potato protein or two or more types of potato proteins. That is, the potato protein composition may also contain a mixture of two or more types of potato proteins.

[0018] The method for extracting and separating potato protein from potatoes is not particularly limited, but examples thereof include the following methods.

[0019] (1) A coagulation step is performed using potato juice (potato juice) to coagulate potato proteins by heating, salting out, or the like. In the case of coagulation by heating, the heating temperature and heating time are not particularly limited, but examples include a heating temperature of 90 to 120°C and a heating time of 1 to 60 minutes. Heating can be performed using electricity, steam, or the like. In the case of coagulation by salting out, for example, lime solution is added to the squeezed juice, followed by blowing in carbon dioxide gas, to produce calcium carbonate, which allows the potato proteins to be adsorbed onto the resulting calcium carbonate. (2) The coagulated potato proteins are dried in a dryer. The drying time is not particularly limited and can be adjusted as needed to achieve the desired moisture content. If necessary, the coagulated potato proteins can be dehydrated in a dehydrator before drying. (3) Furthermore, if necessary, the potato proteins can be washed. If washing is performed after the drying step (2), the potato proteins are dried again in a dryer after washing. The drying time is not particularly limited and can be adjusted as needed to achieve the desired moisture content.

[0020] The potato glycoalkaloid content in the potato protein composition according to this embodiment is 300 ppm or less.

[0021] Potato glycoalkaloids are a type of neurotoxic steroid alkaloid, and examples of glycoalkaloids contained in potatoes include solanine and chaconine.

[0022] The potato glycoalkaloid content in the potato protein composition according to this embodiment may be 300 ppm or less, preferably 200 ppm or less, and more preferably 100 ppm or less, based on the dry matter. By ensuring that the potato glycoalkaloid content falls within this range, the potato glycoalkaloid content is more suitable for use as feed, as it improves the feedability and digestibility for aquatic animals. The potato glycoalkaloid content can be measured by liquid chromatography mass spectrometry (LC / MS). The following method is exemplified as a specific measurement method. The potato protein composition to be measured is finely pulverized and sieved to obtain a permeate. An 80% methanol solution is added to the obtained permeate and stirred to extract the potato glycoalkaloids into the methanol solution. The extracted liquid is recovered and centrifuged for solid-liquid separation. Impurities are filtered out, and the resulting solution is then placed in an HPLC vial to prepare a sample. The obtained sample is subjected to HPLC analysis under the following conditions to measure the potato glycoalkaloid content. Column: Cosmosil 5C18 AR-II (4.6 mm i.d. x 250 mm) manufactured by Nacalai Tesque, Inc. Mobile phase: 55% acetonitrile-containing 10 mM sodium phosphate aqueous solution 0.9 ml / min Column temperature: 40°C Detection wavelength: 202 nm Injection volume: 20 μL

[0023] For example, the potato glycoalkaloid content in potato protein can be reduced by including a washing step when separating and extracting potato protein from potatoes. Potato protein whose potato glycoalkaloid content has been reduced by washing can be used to prepare a potato protein composition having a potato glycoalkaloid content of 300 ppm or less. Potato protein whose potato glycoalkaloid content has been reduced to 300 ppm or less by washing can also be used as is as a potato protein composition. Potato protein that has been subjected to a washing step and potato protein that has not been subjected to a washing step can also be appropriately combined to prepare a potato protein composition having a potato glycoalkaloid content of 300 ppm or less.

[0024] The washing step may be, for example, a method comprising washing potato protein with one or more selected from an aqueous acid solution and / or an alcohol.

[0025] First, the cleaning step using an acid aqueous solution will be described.

[0026] Dried or undried potato protein is washed with an aqueous acid solution in a stirring tank. From the viewpoint of washability, fine potato protein particles are preferred. Examples of acids used for washing include sulfuric acid, hydrochloric acid, and acetic acid. One acid may be used alone, or two or more acids may be used in combination.

[0027] The total amount of aqueous acid solution used in the washing step is not particularly limited, but can be, for example, 10 times or more, preferably 20 times or more, preferably 30 times or more, and preferably 35 times or more, relative to the weight of the potato protein. When washing is performed multiple times, the amount of aqueous acid solution used in each washing step can be, for example, 5 times or more, preferably 8 times or more, relative to the weight of the potato protein.

[0028] The pH of the aqueous acid solution used for washing is preferably 0.5 to 4.0, preferably 0.5 to 3.5, and preferably 0.5 to 3.3. If the pH increases due to a reaction during stirring, an aqueous acid solution may be appropriately added.

[0029] The washing time with the acid aqueous solution is, for example, 2 to 12 hours, and the washing temperature is, for example, 20 to 80°C.

[0030] After washing with an acidic aqueous solution, the protein is dehydrated to obtain wet protein.

[0031] To improve the degree of cleaning, it is preferable to repeat the cleaning with the acid aqueous solution two or more times.

[0032] After the washing step using an acidic aqueous solution is completed, a pH adjustment step is preferably carried out to adjust the pH of the potato protein in water. The pH of the potato protein in water is preferably 4.0 or higher, preferably 5.0 or higher, preferably 6.0 or higher, preferably 6.5 or higher, and preferably 7.0 or higher. The pH of the potato protein in water is not particularly limited, but is, for example, 10.0 or lower, preferably 9.0 or lower, and preferably 8.5 or lower. The pH can be adjusted by adding an appropriate amount of an alkaline substance such as caustic water to a dispersion obtained by thoroughly dispersing the potato protein after the washing step in an appropriate amount of water. If the pH fluctuates during the pH adjustment step, an alkaline substance can be supplied as needed.

[0033] After the washing step or, if necessary, after the pH adjustment step, a dehydration treatment and / or a drying treatment can be carried out. The drying treatment can be carried out in a dryer. The temperature and time of drying are not particularly limited and can be appropriately adjusted to achieve the desired moisture content. After drying, a pulverization treatment can be carried out as necessary.

[0034] Next, the cleaning step using alcohol will be described.

[0035] Dried or undried potato protein is washed with alcohol in a stirring tank. From the viewpoint of washability, fine potato protein particles are preferred. Examples of alcohols used for washing include methanol and ethanol. One type of alcohol may be used alone, or two or more types may be used in combination.

[0036] The cleaning using alcohol may be performed using only alcohol, or may be performed using an aqueous alcohol solution (a mixture of alcohol and water). The aqueous alcohol solution is preferably a mixture of alcohol and water to a concentration of 50% by weight or more.

[0037] The total amount of alcohol or aqueous alcohol solution used in the washing step is not particularly limited, and can be, for example, 10 times or more, preferably 20 times or more, preferably 30 times or more, or preferably 50 times or more relative to the weight of the potato protein. When washing is performed multiple times, the amount of alcohol or aqueous alcohol solution used in each washing can be, for example, 5 times or more, preferably 8 times or more relative to the weight of the potato protein.

[0038] The washing time with alcohol is, for example, 2 to 12 hours, and the washing temperature is, for example, 20 to 50°C.

[0039] After washing with alcohol, the protein is dehydrated to obtain wet protein.

[0040] To improve the degree of cleaning, it is preferable to repeat the cleaning with alcohol two or more times.

[0041] After the washing treatment, the potato protein is preferably washed with water to reduce the amount of alcohol remaining in the potato protein. Thereafter, the potato protein is preferably dehydrated and then dried in a dryer. The drying temperature and time are not particularly limited and can be appropriately adjusted to achieve the desired moisture content. After drying, the potato protein can be appropriately pulverized, if necessary.

[0042] The potato protein composition according to this embodiment has a free amino acid content of 10,000 ppm to 75,000 ppm on a dry basis. The term "free amino acids" refers to 20 types of free amino acids that exist in a free state, separate from the amino acids that constitute proteins, specifically alanine, asparagine, cystine, glutamine, glycine, isoleucine, leucine, methionine, phenylalanine, proline, serine, threonine, tryptophan, tyrosine, valine, aspartic acid, glutamic acid, arginine, histidine, and lysine. The free amino acid content of the potato protein composition is preferably 15,000 ppm or more, preferably 20,000 ppm or more, preferably 25,000 ppm or more, preferably 30,000 ppm or more, preferably 35,000 ppm or more, and preferably 40,000 ppm or more on a dry basis. The potato protein composition preferably has a free amino acid content of 70,000 ppm or less, preferably 65,000 ppm or less, and preferably 60,000 ppm or less, based on dry matter. By keeping the free amino acid content within this range, the potato protein composition is more suitable for use as feed, as it improves the intake and digestibility of aquatic animals.

[0043] The free amino acid content in the potato protein composition can be adjusted to within a predetermined range, for example, by adding free amino acids. Alternatively, it can be adjusted using fermented potato protein containing free amino acids, which is obtained by fermenting potato protein. Alternatively, potato protein whose free amino acid content has been increased by fermentation can be used as is as the potato protein composition. When fermented potato protein is used, the free amino acid content of the fermented potato protein can be appropriately adjusted by adjusting the fermentation conditions. For example, the free amino acid content of the fermented potato protein can be adjusted by the timing of terminating fermentation. That is, the free amino acid content can be controlled within a predetermined range by terminating the fermentation of potato protein during fermentation, for example, by heat-treating the fermentation-initiated potato protein at 80°C for 30 minutes. The free amino acid content can be measured by an automated amino acid analysis method.

[0044] The fungus used for fermentation is not particularly limited, but it is preferable to use koji mold. As the koji mold, any fungus belonging to the genus Aspergillus can be used. Examples of fungi belonging to the genus Aspergillus include Aspergillus oryzae, Aspergillus sojae, Aspergillus luchuensis, Aspergillus glaucus, and Aspergillus tamarii, but it is preferable to use Aspergillus oryzae. One type of koji mold may be used alone, or two or more types may be used in combination. As the koji mold, publicly available strains or strains contained in koji starters commercially available from koji starter makers can be used.

[0045] Fermented potato protein can be obtained by adding bacteria to potato protein and fermenting it. Fermentation conditions such as fermentation temperature and fermentation time are not particularly limited, and can be carried out under conditions typically used in the art. The fermentation temperature is preferably 20 to 40°C, and more preferably 25 to 35°C. The fermentation time is preferably 12 hours to 7 days, and more preferably 1 to 4 days.

[0046] The crude protein content of the potato protein composition according to this embodiment is preferably 70% by weight or more, preferably 75% by weight or more, and preferably 80% by weight or more, based on the dry matter. A crude protein content in the dry matter within this range results in fewer impurities, making the composition suitable as a protein source for animal feed. The crude protein content can be measured by a combustion method.

[0047] Furthermore, the proportion of potato-derived crude protein in the crude protein in the potato protein composition is preferably 90% by weight or more, preferably 95% by weight or more, and preferably 98% by weight or more.

[0048] The moisture content of the potato protein composition according to this embodiment is preferably 15% by weight or less, preferably 10% by weight or less, preferably 9% by weight or less, and preferably 8% by weight or less. A moisture content within this range is low, making it suitable as a protein source for animal feed and also excellent in storage stability. The moisture content of potato protein can be measured, for example, using an infrared moisture meter that measures the heat-dry mass at 105°C (normal pressure heat-drying method).

[0049] The crude fat content of the potato protein composition according to this embodiment is preferably 0.5% by weight or less, preferably 0.2% by weight or less, and preferably 0.1% by weight or less, based on the dry matter. A crude fat content within this range is preferred as a protein source for animal feed. The crude fat content can be measured, for example, by the diethyl ether method.

[0050] The potato protein composition according to this embodiment has a pH in water of preferably 4.0 or higher, preferably 5.0 or higher, preferably 6.0 or higher, preferably 6.5 or higher, or preferably 7.0 or higher. The pH of the potato protein composition in water is not particularly limited, but can be, for example, 10.0 or lower, preferably 9.0 or lower, and preferably 8.5 or lower. When the potato protein composition has a pH in water within this range, its use as feed improves its intake and digestibility for aquatic animals, making it more suitable.

[0051] The pH of potato protein or potato protein composition in water can be determined, for example, by adding 40 g (dry weight) of potato protein or potato protein composition to 360 g of water, thoroughly dispersing the potato protein or potato protein composition, and measuring the pH of the resulting dispersion.The pH of fermented potato protein in water can be determined, for example, by adding 40 g (dry weight) of fermented potato protein to 360 g of water, thoroughly dispersing the potato protein or potato protein composition, and measuring the pH of the resulting dispersion.

[0052] The potato protein composition according to the present embodiment is particularly suitable as a protein source for feeding to animals. Here, "animal" refers to animals including humans, typically aquatic animals or livestock animals, and preferably aquatic animals. Examples of aquatic animals include fish such as yellowtail, sea bream, salmon, flounder, tiger pufferfish, amberjack, striped jack, yellowtail amberjack, eel, carp, crucian carp, and rainbow trout, as well as crustaceans such as shrimp and crab.

[0053] When the potato protein composition according to this embodiment is used in an aquatic animal feed composition, the content of the potato protein composition in the aquatic animal feed composition is preferably 3% by weight or more, preferably 5% by weight or more, preferably 10% by weight or more, preferably 15% by weight or more, preferably 20% by weight or more, preferably 25% by weight or more, preferably 30% by weight or more, preferably 35% by weight or more, preferably 40% by weight or more, based on the dry matter. The content of the potato protein in the aquatic animal feed composition is preferably 80% by weight or less, preferably 75% by weight or less, preferably 70% by weight or less, based on the dry matter.

[0054] The potato protein composition according to this embodiment preferably contains fermented potato protein, and more preferably contains a fermented potato protein obtained by fermenting potato protein that has been subjected to the above-described washing treatment to reduce its potato glycoalkaloid content (hereinafter also referred to as washed potato protein). Furthermore, the potato protein composition according to this embodiment preferably contains washed potato protein and a fermented potato protein obtained by fermenting the washed potato protein. Furthermore, the potato protein composition according to this embodiment may be a mixture of washed potato protein and a fermented potato protein obtained by fermenting the washed potato protein. The weight ratio of washed potato protein to fermented potato protein in the potato protein composition is, for example, 1:0.1 to 1:10, preferably 1:0.1 to 1:5, and more preferably 1:0.1 to 1:4.

[0055] <Feed composition for aquatic animals> This embodiment is a feed composition for aquatic animals containing potato protein, in which the potato glycoalkaloid content in the dry matter is 100 ppm or less and the free amino acid content in the dry matter is 4,000 ppm or more and 35,000 ppm or less.

[0056] Details of potato protein are as described above.

[0057] The potato glycoalkaloid content of the aquatic animal feed composition according to this embodiment may be 100 ppm or less, preferably 80 ppm or less, more preferably 60 ppm or less, and even more preferably 50 ppm or less, based on the dry matter. By ensuring that the potato glycoalkaloid content falls within this range, the feed composition's intake and digestibility for aquatic animals is improved, making it even more suitable. The potato glycoalkaloid content can be measured by liquid chromatography-mass spectrometry (LC / MS).

[0058] The potato glycoalkaloid content of the aquatic animal feed composition can be adjusted as appropriate by adjusting the potato glycoalkaloid content in raw materials containing potato glycoalkaloids, i.e., the potato protein composition described above and other potato-derived raw materials.

[0059] The free amino acid content in the aquatic animal feed composition according to this embodiment may be from 4,000 ppm to 35,000 ppm, based on the dry matter. The free amino acid content in the aquatic animal feed composition is preferably from 5,000 ppm to 6,000 ppm, based on the dry matter, preferably from 7,000 ppm to 8,000 ppm, preferably from 10,000 ppm to 12,000 ppm, preferably from 14,000 ppm to 16,000 ppm, preferably from 18,000 ppm to 20,000 ppm. The free amino acid content in the feed composition for aquatic animals is preferably 34,000 ppm or less, preferably 33,000 ppm or less, preferably 32,000 ppm or less, preferably 31,000 ppm or less, preferably 30,000 ppm or less, preferably 29,000 ppm or less, and preferably 28,000 ppm or less, based on dry matter. By setting the free amino acid content within the above range, the feed intake and digestibility of aquatic animals are improved when used as feed, making it more suitable.

[0060] The free amino acid content of the aquatic animal feed composition can be appropriately adjusted by adjusting the content of the potato protein composition and other raw materials containing free amino acids. The free amino acid content can be measured by an automated amino acid analysis method.

[0061] The crude protein content of the aquatic animal feed composition according to this embodiment is preferably 30% by weight or more, preferably 35% by weight or more, preferably 40% by weight or more, preferably 45% by weight or more, based on the dry matter. When the crude protein content in the dry matter is within this range, the feed intake and growth performance of aquatic animals are improved when used as feed, making it more suitable. The crude protein content can be measured by a combustion method.

[0062] Furthermore, the proportion of potato-derived crude protein in the crude protein in the aquatic animal feed composition is preferably 40% by weight or more, preferably 50% by weight or more, preferably 60% by weight or more, preferably 70% by weight or more.

[0063] The aquatic animal feed composition according to this embodiment further contains fish meal, and the fish meal content in the aquatic animal feed composition according to this embodiment is preferably 50% by weight or less, preferably 45% by weight or less, preferably 40% by weight or less, preferably 35% by weight or less, preferably 30% by weight or less, preferably 25% by weight or less, preferably 20% by weight or less, preferably 15% by weight or less. By setting the fish meal content within this range, a higher fish meal replacement rate can be achieved.

[0064] The aquatic animal feed composition according to this embodiment may further contain other ingredients acceptable as feed. Examples of other ingredients acceptable as feed include all the nutritional components commonly used in the aquaculture industry that are necessary for the growth of aquatic animals, such as rotifers, Artemia, and Chlorella; grain flours such as soybean flour, rice flour, defatted soybean meal, corn gluten meal, and wheat flour; lipids such as soybean oil and fish oil; seafood feeds such as fish meal, pupa meal, and raw minced fish meat; wheat gluten; pregelatinized starches such as α-tapioca starch, wheat gluten, sodium caseinate, sodium alginate, sodium polyacrylate, and carboxymethylcellulose. Examples of suitable raw materials include, but are not limited to, known thickening agents such as sodium cellulose, various vegetable gums, and soy whey; various vitamin sources such as vitamin mix, ascorbic acid, and α-tocopherol; various mineral sources such as monocalcium phosphate, mineral mix, and calcium carbonate; various protein sources; prebiotic components such as fructooligosaccharides, lactose, oligosaccharides, and galactooligosaccharides; and amino acids such as DL-methionine, taurine, L-lysine hydrochloride, and monosodium glutamate. When multiple raw materials are used, the composition ratio of each raw material is not particularly limited and can be appropriately selected by one skilled in the art.

[0065] Aquatic animals can be farmed by feeding them the aquatic animal feed composition of this embodiment. The aquatic animals are not particularly limited, and examples include fish such as yellowtail, sea bream, salmon, flounder, tiger pufferfish, amberjack, striped jack, yellowtail amberjack, eel, carp, crucian carp, and rainbow trout; crustaceans such as shrimp and crab; and primarily aquatic reptiles such as soft-shelled turtles and green turtles. The aquatic animals are preferably fish or crustaceans, and are preferably yellowtail, sea bream, salmon, or shrimp. The aquatic animal feed composition of this embodiment has particularly high daily feed intake rates and feed efficiency for aquatic animals, allowing for efficient rearing (farming) of aquatic animals.

[0066] The present embodiment will be described in more detail below with reference to examples, but the present embodiment is not limited to these examples. In the examples, "parts" and "%" are by weight.

[0067] <Composition analysis> The contents of crude protein, free amino acids, and potato glycoalkaloids were analyzed by the following methods. (Crude protein: combustion method) Crude protein composition analysis was outsourced to the Japan Food Research Center, and measurements were made by the combustion method. (Free amino acids: automated amino acid analysis method) Free amino acid composition analysis was outsourced to the Japan Food Research Center, and measurements were made by the automated amino acid analysis method. (Potato glycoalkaloids: liquid chromatography-mass spectrometry) Potato glycoalkaloid composition analysis was outsourced to the Japan Food Research Center, and measurements were made by liquid chromatography-mass spectrometry.

[0068] <Sample Preparation> (Potato Protein Separation and Extraction) (1) Potato juice obtained by squeezing potatoes was heated to aggregate the potato proteins in the potato juice. (2) The aggregated potato proteins were dehydrated in a dehydrator. (3) The dehydrated potato proteins were dried in a dryer. (4) The dried potato proteins were pulverized in a benchtop pulverizer (mill) to obtain a pulverized product.

[0069] The crushed potato protein was used as "unwashed potato protein" in the following experiments.

[0070] Washing of Potato Proteins The resulting unwashed potato proteins were used to wash with acid in a stirred tank according to the following procedure.

[0071] Unwashed potato protein was placed in a container, and water was added to prepare a potato protein dispersion with a content of 10% by weight. Sulfuric acid was added to the dispersion while stirring to adjust the pH to within the range of 3.0 to 3.5. The temperature of the dispersion was kept at room temperature (20 to 30°C). Dilute sulfuric acid of 10% by weight or less was used as the sulfuric acid.

[0072] Since the pH began to rise immediately after the addition of the acid, acid was added as needed to maintain the pH within the range of 3.0 to 3.5. Stirring was continued for approximately 3 hours, and it was confirmed that the pH remained steady. Thereafter, stirring was stopped, and the potato was dehydrated under vacuum to obtain wet potato protein.

[0073] To increase the degree of washing, the washing procedure from the step of preparing a 10% by weight dispersion of potato protein to the step of obtaining wet potato protein was repeated three more times, for a total of four times.

[0074] After the washing treatment was completed, an appropriate amount of aqueous sodium hydroxide solution with a concentration of 5% or less was added to the dispersion obtained by thoroughly dispersing the potato protein in water, and the pH of the dispersion was neutralized to a range of 7.0 to 7.5. Since the pH fluctuated even during neutralization, aqueous sodium hydroxide solution was supplied as needed.

[0075] The neutralized dispersion was dehydrated under vacuum, and the resulting wet potato protein was dried by heating in a dryer at a temperature of 90 to 200° C. until the moisture content reached 5 to 10%.

[0076] The potato protein obtained after drying was used in the following experiments as "washed potato protein."

[0077] (Koji fermentation treatment of washed potato protein) Washed potato protein was pulverized using a benchtop mill. The pulverized washed potato protein was steamed, and then 0.02 parts by weight of koji starter (manufactured by Bioc, for soybean miso) and 3 parts by weight of potato starch were thoroughly mixed and sprinkled over 100 parts by weight of the steamed potato protein, and the mixture was left at 30°C for 3 days to produce potato protein koji. The potato protein koji was stored frozen.

[0078] The potato protein koji was added to the steamed washed potato protein in an amount of 25% or 50% by weight of the washed potato protein, and after thorough mixing, the mixture was fermented at 30°C for 7 days. After fermentation, the mixture was heated at 80°C for 30 minutes to terminate the fermentation. The resulting fermented potato protein was used in the following experiments as "fermented potato protein."

[0079] (Preparation of potato protein compositions used) The resulting unwashed potato protein, washed potato protein, and fermented potato protein were mixed in the proportions shown in Table 1 and used as potato protein compositions. The crude protein content, free amino acid content, and potato glycoalkaloid content of each potato protein composition are shown in Table 1.

[0080] (Preparation of Aquatic Animal Feed Compositions) The potato protein composition and other ingredients were mixed in the proportions shown in Table 1 and then molded into pellets with a diameter of approximately 4 mm using a compound feed pelletizer (manufactured by JIAWANSHUN Co., Ltd.). After molding, the pellets were heated and dried in a dryer until the moisture content reached 5-10%, producing the aquatic animal feed compositions of Examples 1 to 4 and Comparative Examples 1 and 2. As a reference example, an aquatic animal feed composition was also prepared in the same manner, using fish meal alone as a protein source without the potato protein composition. Note that in Examples 1 to 4 and Comparative Examples 1 and 2, the fish meal content was reduced and an equivalent protein amount of potato protein composition was added instead to achieve the same crude protein content. The weight deficit resulting from the substitution of the potato protein composition for fish meal was compensated for by adding pregelatinized starch to make up the equivalent weight, adjusting the missing ω-3 unsaturated fatty acids to an equal amount with fish oil, and adjusting the missing ash and taurine to an equal amount with a commercially available mineral mix. The crude protein content of the prepared aquatic animal feed composition, the potato-derived crude protein content, the proportion of potato-derived crude protein in the crude protein of the aquatic animal feed composition, the free amino acid content, and the potato glycoalkaloid content are shown in Table 1.

[0081] <Evaluation of Feed Efficiency of Samples> (Rearing Method) Rainbow trout were used as test fish, and 144 L aquaria containing 10 test fish were prepared for each Example. Rearing was performed using running water with a constant supply of fresh water (filtered river water) at a temperature of approximately 9°C. For all Examples, the fish were placed in the aquaria and pre-reared for approximately one week in all test groups with the fish meal formulated feed used in the Reference Example. After confirming that there was no variation in feed intake between the aquaria, the test of feeding the aquatic animal feed composition of each Example began.

[0082] The test feed was fed twice daily until satiation (until the fish stopped instantly consuming food that had fallen to the bottom of the tank), and the amount of feed fed up to that point was considered the daily feed intake. The feeding test was carried out for 8 weeks. The weight of the fish one week after preliminary rearing was measured as the initial fish weight, and the weight of the fish eight weeks after the feeding test was measured as the final fish weight. The increase in the final fish weight from the initial fish weight was calculated as the total weight gain. The daily feed intake rate (% / day) and feed efficiency (%) were calculated using the following formulas, and the results are shown in Table 1. Daily feed intake rate (% / day) = total feed intake (g, wet weight) / ((initial fish weight + final fish weight) / 2) / number of rearing days × 100 Feed efficiency (%) = total fish weight gain (g, wet weight) / total feed amount (g, dry weight) × 100

[0083]

[0084] As is clear from Table 1, Examples 1 to 4, which used potato protein compositions with a potato glycoalkaloid content of 300 ppm or less and a free amino acid content of 10,000 to 75,000 ppm, showed feed intake rates equivalent to that of the Reference Example, which used fish meal as the only protein source, and also showed higher feeding efficiency than Comparative Examples 1 and 2, which used potato protein compositions outside these numerical ranges. In particular, Examples 2 and 3 showed feeding efficiency equivalent to that of the Reference Example, which used fish meal as the only protein source. These results demonstrate that the potato protein composition and aquatic animal feed composition according to the present embodiments are particularly useful as feed ingredients or feeds that can significantly reduce the amount of fish meal used.

[0085] (Preparation of aquatic animal feed compositions) The potato protein composition consisting solely of the fermented potato protein described above was mixed with other ingredients in the proportions shown in Table 2, and then molded into pellets with a diameter of approximately 1.6 to 3.5 mm using a granulator (12VR-750SDX, manufactured by Alfa Royal). After molding, the pellets were dried for 24 hours in a dryer set at 60°C and sieved to remove the powder, thereby preparing the aquatic animal feed compositions of Examples 5 to 8. In addition, as Reference Example 2, an aquatic animal feed composition not containing the potato protein composition was similarly prepared. The crude protein content, potato-derived crude protein content, proportion of potato-derived crude protein in the crude protein of the aquatic animal feed composition, free amino acid content, and potato glycoalkaloid content of the prepared aquatic animal feed compositions are shown in Table 2.

[0086] <Evaluation of Feed Efficiency of Samples> (Rearing Method) Red sea bream were used as test fish, and 500 L aquaria containing 25 test fish were prepared for each example. Rearing was performed using running water with a constant supply of seawater (filtered seawater) at a temperature of approximately 24°C. For all examples, the fish were pre-reared for one week on a commercially available compound feed (Pear Gold, manufactured by Nisshin Marubeni Feed Co., Ltd.) before being placed in the aquaria. After the fish reached an average weight, the test was started by feeding them the aquatic animal feed composition of each example.

[0087] The test feed was fed twice daily until satiation (until the fish stopped instantly consuming food that had fallen to the bottom of the tank), and the amount of feed fed up to that point was considered the daily feed intake. The feeding test was carried out for 10 weeks. The weight of the fish one week after preliminary rearing was measured as the initial fish weight, and the weight of the fish 10 weeks after the feeding test was measured as the final fish weight. The increase in the final fish weight from the initial fish weight was calculated as the total weight increase. The daily feed intake rate (% / day) and feed efficiency (%) were calculated using the following formulas, and the results are shown in Table 2. Daily feed intake rate (% / day) = total feed intake (g, wet weight) / ((initial fish weight + final fish weight) / 2) / number of rearing days × 100 Feed efficiency (%) = total fish weight increase (g, wet weight) / total feed amount (g, dry weight) × 100

[0088]

[0089] As is clear from Table 2, red sea bream, like rainbow trout, showed a high feeding rate when a potato protein composition with a potato glycoalkaloid content of 300 ppm or less and a free amino acid content of 10,000 to 75,000 ppm was used.

[0090] The upper and / or lower limits of the numerical ranges described herein can be arbitrarily combined to define a preferred range. For example, the upper and lower limits of the numerical ranges can be arbitrarily combined to define a preferred range, the upper limits of the numerical ranges can be arbitrarily combined to define a preferred range, and the lower limits of the numerical ranges can be arbitrarily combined to define a preferred range.

[0091] Although the present embodiment has been described in detail above, the specific configuration is not limited to this embodiment, and even if there are design changes within the scope that do not deviate from the gist of this disclosure, they are included in this disclosure.

[0092] All publications, patents, and patent applications cited herein are hereby incorporated by reference in their entirety.

Claims

1. A potato protein composition having a potato glycoalkaloid content of 300 ppm or less in dry matter and a free amino acid content of 10,000 ppm or more and 75,000 ppm or less in dry matter.

2. The potato protein composition according to claim 1, wherein the crude protein content in dry matter is 70% by weight or more.

3. A potato protein composition according to claim 1 or 2, wherein the proportion of potato-derived crude protein in the crude protein in the potato protein composition is 90% by weight or more.

4. A potato protein composition according to claim 1 or 2, which contains fermented potato protein.

5. A feed composition for aquatic animals, comprising the potato protein composition according to claim 1 or 2.

6. A feed composition for an aquatic animal containing potato protein, wherein the content of potato glycoalkaloids in the dry matter is 100 ppm or less, and the content of free amino acids in the dry matter is 4,000 ppm or more and 35,000 ppm or less.

7. The feed composition for aquatic animals according to claim 6, wherein the crude protein content in dry matter is 30% by weight or more.

8. The feed composition for aquatic animals according to claim 6 or 7, wherein the proportion of potato-derived crude protein in the crude protein in the feed composition for aquatic animals is 40% by weight or more.

9. The feed composition for aquatic animals according to claim 6 or 7, further comprising fish meal, the fish meal content being 50% by weight or less.

10. The feed composition for aquatic animals according to claim 9, wherein the fish meal content is 30% by weight or less.

Images