JP7798262B2 - Grain husks, gluten feed, method for producing grain husks, method for producing gluten feed, feed for raising insects, and method for raising insects - Google Patents

Description

The present invention relates to grain husks obtained by processing grains by wet milling, gluten feed, a method for producing grain husks, a method for producing gluten feed, insect feed, and an insect rearing method.

Wet milling, also known as wet grinding, is a method of separating grains, primarily corn, into their constituent components, such as husks, germ, protein, and starch. In wet milling, the grains are soaked in an acidic solution, swelled, and then crushed to promote the separation of the constituent components. The husks, also known as bran, are a by-product of wet milling grains and are used as livestock feed and fuel. Gluten feed is made by mixing the husks with the liquid in which grains have been soaked, also known as steep liquor, and then dehydrating and/or drying them. Because gluten feed has a higher nutritional value than the husks, it is primarily used as livestock feed.

Like husks and gluten feed, the protein obtained from wet milling is called gluten meal and is used as livestock feed. When a sulfite solution is used in wet milling, sulfites such as sulfur dioxide remain in the gluten meal. Therefore, heat-treated corn gluten meal (sulfur dioxide content less than 30 ppm, protein content 50-99% by weight on a dry weight basis) is known for use as human food or feed, with sulfites removed from gluten meal (see Patent Document 1).

Patent No. 4750901

According to Patent Document 1, gluten meal contains sulfites primarily in the form of bonds. However, it is not known whether acids such as sulfites are present in grain husks or gluten feed, which is primarily made up of husks.

Since grain husks and gluten feed are primarily composed of fiber, they have low nutritional value and have no uses other than as feed or fuel. Furthermore, even when grain husks and gluten feed are used as animal feed, no significant effects have been found compared to other feed ingredients, and no valuable uses for grain husks or gluten feed have been found.

In recent years, insects have been attracting attention as a source of animal protein for food and animal feed, but when insects are raised using grain husks or gluten feed as feed, they barely grow, making them insufficient as feed for insect rearing.

The present invention relates to grain husks obtained by wet milling, which have a pH in the weakly acidic or neutral range. Another aspect of the present invention relates to a gluten feed comprising grain husks obtained by wet milling and a grain soaking liquid obtained by wet milling, which has a pH in the weakly acidic or neutral range.

Furthermore, the grain husks or gluten feed of the present invention have a pH of 4 to 8 in the water in which the grain husks or gluten feed are soaked. Furthermore, when the grain husks or gluten feed are soaked in water with a weight four times that of the grain husks or gluten feed, the electrical conductivity of the water may be less than 10 mS/cm, for example, 2 to 9 mS/cm. The grain in the present invention may be corn.

The present invention provides a method for producing grain husks, which includes an adjustment step of increasing the pH and/or decreasing the electrical conductivity of the husks. The method for producing grain husks of the present invention may include a soaking step of soaking grains in an acidic solution to obtain a soaked substance, a first separation step of separating a grain soaking liquid and a solid material containing the grain germ and husks from the soaked substance, a second separation step of separating the germ and the husks from the solid material, and an adjustment step of increasing the pH and/or decreasing the electrical conductivity of the husks.

The present invention further provides a method for producing gluten feed, which includes an adjusting step of increasing the pH and/or decreasing the electrical conductivity of one or more selected from the gluten feed. The method for producing gluten feed of the present invention may include a soaking step of soaking grains in an acidic solution to obtain a soaked product, a first separation step of separating a grain soaking liquid and a solid material containing the germ and husk of the grain from the soaked product, a second separation step of separating the germ and the husk from the solid material, a mixing step of mixing the husk with the grain soaking liquid to obtain gluten feed, and an adjusting step of increasing the pH and/or decreasing the electrical conductivity of one or more selected from the grain soaking liquid, the husk, and the gluten feed.

In the method for producing grain husks or gluten feed of the present invention, the conditioning step may be a step of mixing with an alkaline solution or a step of washing with an alkaline solution and/or water.

The present invention provides a feed for growing insects, comprising cereal husks or gluten feed.
The present invention further provides a feed for raising insects, comprising wheat bran. The insects may be beetles. The present invention also provides a method for raising insects on grain husks or gluten feed. The insects may be beetles.

The pH of grain husks and gluten feed obtained by wet milling is acidic, but adjusting the pH to a slightly acidic or neutral range can significantly promote the growth of insects and other animals.

1 shows the results of rearing insects in this example, in which different letters indicate a significant difference of p<0.01 as determined by statistical testing (One-way ANOVA with Bonferroni correction). 1 shows the results of rearing insects in this example. 1 shows the results of rearing insects in this example, with asterisks indicating that a significant difference was found between the example and the comparative example by statistical testing (One-way ANOVA with Dunnett's multiple comparisons test).

The following describes embodiments for implementing the present invention, but the present invention is not limited to the following embodiments.

The present invention relates to grain husks obtained by wet milling, which have a pH in the weakly acidic to neutral range.

Wet milling, also known as wet grinding, was developed as a method for producing starch from grains with hard outer skins (or pericarp), such as corn and rice. Wet milling is primarily used in processing corn, where the grain is soaked in an acidic solution to swell, the soaking liquid is separated and removed, and the swollen grain is ground to separate the grain into its outer skin, germ, protein, and starch.

The grain referred to in the present invention is preferably corn. The corn used for wet milling is preferably dent corn, as it has a higher starch content than other types of corn.

Here's a specific example of corn wet milling: Corn is soaked in a 0.1-0.3% by volume aqueous solution of sulfurous acid at a temperature of 45-55°C for 30-48 hours. Then, solid-liquid separation is performed to obtain a solid fraction consisting mainly of swollen corn and the soaking liquid with the solid fraction removed.

The swollen corn is crushed and then separated into a liquid and a solid portion. The solid portion consists of the germ and husk, and the husk is obtained by classification methods such as sieving. The corn husk, also known as corn bran, is primarily composed of arabinoxylan, a type of hemicellulose. The liquid portion remaining after the germ and husk are separated is primarily composed of protein and starch.

The steeping liquid is called steep liquor. Steep liquor can also refer to steeping liquid concentrated to about 50% solids. Steep liquor contains nucleic acids such as inositol and their decomposition products, water-soluble vitamins, amino acids, etc. Steep liquor is mixed with husks, then dehydrated and dried to create gluten feed. In other words, gluten feed is made by mixing grain husks obtained primarily by wet milling with grain steeping liquid obtained by wet milling.

The grain husks and/or gluten feed obtained by wet milling may be washed with water, but the pH is in the acidic range. Here, "the pH of the grain husks and/or gluten feed is in the acidic range" means that the pH of the water in which the grain husks and/or gluten feed are soaked is in the acidic range; specifically, the pH may be less than 3.9. The water is preferably distilled water, ion-exchanged water, or pure water, and tap water is also acceptable. The pH of the grain husks and/or gluten feed can be determined by soaking the grain husks and/or gluten feed in water that is 3 to 100 times its weight and measuring the pH of the supernatant.

The pH of the grain husks and/or gluten feed of the present invention is in the weakly acidic or neutral range, and should be at least higher than the pH of conventional grain husks and/or gluten feed. Specifically, the pH of the distilled water in which the grain husks and/or gluten feed are soaked is 4 or higher, with preferred pH values being 4.1 or higher, 4.2 or higher, 4.3 or higher, 4.4 or higher, or 4.5 or higher, preferably in the range of 4.1 to 8.0, and more preferably 5.0 to 7.5.

The grain husks and/or gluten feed of the present invention are preferably soaked in water with a lower electrical conductivity than conventional grain husks and/or gluten feeds. This is because the electrolytes contained in the grain husks and/or gluten feed are lost during the washing process described below. When conventional gluten feed is soaked in four times its weight of water, the electrical conductivity of the water is 12 to 13 mS/cm. When the grain husks and/or gluten feed of the present invention is soaked in four times its weight of water, the electrical conductivity of the water is preferably less than 10 mS/cm, and more preferably 2 to 9 mS/cm. Examples of water that can be used include tap water, distilled water, ion-exchanged water, and pure water.

Another aspect of the present invention provides a method for producing grain husks. This method includes a soaking step in which grains are soaked in an acidic solution to obtain a soaked product; a first separation step in which the soaked product is separated into a grain soaking liquid and a solid mixture containing the grain germ and husk; a second separation step in which the solid mixture is separated from the germ and husk; and an adjustment step in which the pH of the husk is increased and/or the electrical conductivity of the husk is decreased. Here, the soaking step, first separation step, and second separation step are included in wet milling, and the solid refers to swollen grains, such as the swollen corn described above.

The adjustment step is a step of increasing the pH of the exine shell, preferably a step of adjusting the pH of the exine shell to a weakly acidic or neutral range. Another adjustment step is a step of decreasing the electrical conductivity of the exine shell, preferably a step of adjusting the electrical conductivity of the water when the exine shell is immersed in water four times its weight to less than 10 mS/cm. Hereinafter, electrical conductivity refers to the electrical conductivity of the water when the object to be measured is immersed in water four times its weight.

Furthermore, the present invention provides a method for producing gluten feed. Specifically, the method includes a soaking step in which grains are soaked in an acidic solution to obtain a soaked product; a first separation step in which a grain soaking liquid and a solid mixture containing the grain germ and husk are separated from the soaked product; a second separation step in which the germ and husk are separated from the solid mixture; a mixing step in which the husk is mixed with the grain soaking liquid; and an adjustment step. Here, the soaking step, first separation step, and second separation step are included in wet milling, and the solid refers to swollen grains, such as the swollen corn described above.

The gluten feed production method of the present invention can be one or more of the following: a method in which the pH of the husks and/or grain soaking liquid is increased before mixing, preferably to a weakly acidic or neutral range, and then the husks and grain soaking liquid are mixed to obtain gluten feed; a method in which the husks and grain soaking liquid are mixed to obtain gluten feed, and then the pH of the gluten feed is increased, preferably to a weakly acidic or neutral range; a method in which the electrical conductivity of the husks and/or grain soaking liquid before mixing, preferably to less than 10 mS/cm, and then the husks and grain soaking liquid are mixed to obtain gluten feed; and a method in which the electrical conductivity of the gluten feed is decreased after obtaining the gluten feed, preferably to less than 10 mS/cm. It is desirable to dehydrate and/or dry the husks directly or after mixing them with the grain soaking liquid, and obtain dried husks or gluten feed.

The conditioning process for grain husks and/or gluten feed involves increasing the pH and/or decreasing the electrical conductivity of the acidic grain husks and/or gluten feed, and the method is not limited. Specific examples include heating to remove remaining components such as sulfur dioxide, mixing with an alkaline solution, and washing with an alkaline solution and/or water. The conditioning process can preferably bring the pH of the grain husks and/or gluten feed into the neutral or weakly acidic range. Furthermore, the conditioning process can reduce the electrical conductivity of the grain husks and/or gluten feed to less than 10 mS/cm.

Among these, the method of mixing with an alkaline solution and the method of washing with an alkaline solution and/or water are advantageous over the method of heating in that they are less likely to cause denaturation of the components and have lower energy costs. Examples of alkaline solutions include aqueous sodium hydroxide, aqueous potassium hydroxide, aqueous calcium hydroxide, and aqueous ammonia.

Specific examples of methods for washing with an alkaline solution and/or water include adding an alkaline solution and/or water to the grain husks and/or gluten feed, preferably stirring, and separating the alkaline solution and/or water from the grain husks and/or gluten feed. Examples of water that can be used include tap water, distilled water, ion-exchanged water, and pure water.

The grain steeping liquid adjustment process involves increasing the pH of the grain steeping liquid, i.e., bringing the acidic grain steeping liquid to a weakly acidic or neutral pH range, and the method for doing so is not limited. Specific examples include neutralizing the liquid with an alkali such as sodium hydroxide, potassium hydroxide, or calcium hydroxide.

The present invention also provides insect feed containing grain husks and/or gluten feed, and a method for raising insects using the insect feed. Here, the insects preferably used are insect species that can be easily and efficiently raised, or insect species for which artificial rearing techniques have been established.

Specific examples include insects belonging to the orders Diptera, Coleoptera, and Orthoptera. Examples of insects in the Diptera order include the house fly (Musca domestica) in the family Muscidae, the flesh fly (Sarcophaga peregrina) in the family Sarcophagidae, the citrus fly (Tetradacus tsuneonis), the oriental fruit fly (Strumeta dorsalis), and the melon fly (Bactrocera cucurbitae/Zeugodacus cucurbitae) in the family Tephritidae, and the American soldier fly (Hermetia illucens) and the black soldier fly (Ptecticus tenebrifer) in the family Stratiomyiidae.

Beetles, i.e., in the order Coleoptera, include so-called mealworms such as Tenebrio obscurus, Tenebrio molitor, and Zophobas atratus, which belong to the superfamily Tenebrionoidea and family Tenebrionidae, and in the order Orthoptera, include Gryllus bimaculatus and Acheta domesticus, which belong to the family Grylloidea. Insects raised on the insect feed of the present invention are preferably beetle larvae known as mealworms.

The present invention will be described in more detail with reference to examples, but the present invention is not limited to the following examples.

1. Production of corn husk and/or gluten feed (1)

One cubic meter of an aqueous solution containing 0.1% by weight of sulfurous acid was added to 1 ton of dried corn (dent corn), and the corn was soaked at 50°C for 35 hours. The soaking liquid and solids were separated, and the solids were crushed. The husk was separated from the germ using a screen and washed with water to obtain the corn husk. 30 mL of ion-exchanged water was added to 1 g of the corn husk, and the husk was left to soak at room temperature for 1 hour. The pH of the supernatant obtained by centrifugation was measured and found to be 3.9.

The corn husks were then mixed with steep liquor concentrated to approximately 50% solids, dehydrated, and dried to obtain gluten feed. 30 mL of ion-exchanged water was added to 1 g of this gluten feed, and after soaking at room temperature for 1 hour, the pH of the supernatant obtained by centrifugation was measured and found to be 3.9.

The pH of this corn husk or gluten feed was adjusted. 161 mL of 1N aqueous sodium hydroxide solution and 100 mL of distilled water were added to 200 g of corn husk or gluten feed, mixed, and soaked at 50°C for 12 hours, then dried at 70°C. 30 mL of ion-exchanged water was added to 1 g of the corn husk or gluten feed, and after soaking at room temperature for 1 hour, the pH of the supernatant obtained by centrifugation was measured and found to be 7.0.

2. Production of corn husk and/or gluten feed (2)
The acidic corn husks were washed with running tap water. 300 mL of 6N sodium hydroxide solution was added to 1 L of steep liquor (pH 3.9) and the pH was measured, which was 6.5. The precipitate was then removed by centrifugation. The corn husks and steep liquor (2) were mixed and dried to produce gluten feed. The gluten feed was immersed in distilled water for 1 hour, and the pH of the supernatant obtained by centrifugation was measured, which was 5.1. The electrical conductivity was measured, which was 5.7 mS/cm.

3. Production of corn husk and/or gluten feed (3)
Gluten feed that showed a pH of 3.9 was mixed with four times its weight of distilled water and soaked in it. After leaving it for one hour, it was centrifuged and the supernatant was discarded. This was counted as one wash, and washing was carried out four times in total. The pH and electrical conductivity of the supernatant were measured at room temperature after each wash. The measurement results are shown in Table 1. Compared to before washing, the pH of the gluten feed after washing increased, and the electrical conductivity of the supernatant of the distilled water in which it was soaked decreased.

4. Insect rearing test using gluten-containing diet (1)
A rearing test was conducted using larvae of the beetle mealworm (T. molitor). The comparative example used gluten feed with a pH of 3.9, while the example 1 used gluten feed with a pH of 7, produced by the method described in 1. above. The example 2 used a 1:1 weight mixture of the gluten feed from example 1 and wheat bran. Twenty mealworm larvae (average weight per individual: 12.6 mg) were added to 10 g of each feed and reared at 25°C for 28 days. The weights per individual measured at the start and after 28 days of rearing are shown in Figure 1. The comparative example showed significantly lower growth than wheat bran (positive control), while example 1 showed growth equivalent to wheat bran. Furthermore, example 2 showed significantly more favorable growth than wheat bran (positive control). The survival rate was over 90% under all conditions.

5. Insect rearing test using gluten-containing feed (2)
A rearing test was conducted using larvae of the beetle mealworm (T. molitor). In the example, gluten feed produced by the method described in 2. above was used as insect rearing feed, while wheat bran served as a control. Twenty mealworm larvae (average weight per individual: 8.3 mg) were added to 10 g of each feed, and reared at 25°C for 28 days. Measurements of the weight per individual at the start and after 28 days of rearing are shown in Figure 2. The growth of the example was comparable to that of the positive control (wheat bran), with no significant difference. The survival rate was 100% in both cases. As shown in Figure 1, larvae reared on unadjusted gluten feed showed significantly lower growth than those on wheat bran, demonstrating that the example promotes larval growth compared to unadjusted gluten feed.

6. Insect rearing test using gluten-containing feed (3)
A rearing test was conducted using larvae of the beetle mealworm (T. molitor). In the examples, gluten feed produced by the method described in 4. above was used as insect rearing feed, while in the comparative example, gluten feed with a pH of 3.9 was used. Twenty-two mealworm larvae (average weight per individual: 5.7 mg) were added to 10 g of each feed, and the larvae were reared at 25°C for 28 days. Measurements of the weight per individual at the start and after 28 days of rearing are shown in Figure 3. Larval growth was significantly promoted by using gluten feed that had been washed one to four times. Larval growth was greatest when gluten feed that had been washed three times (soaking water pH 4.2, electrophoretic mobility 3.2 mS/cm) was used.

Table 2 also shows the larval survival rate during the test period. By using gluten feed that had been washed one to four times, the larval survival rate improved compared to the comparative example.

Claims (6)

It is a feed for raising beetles that contains gluten feed,
The gluten feed contains corn husks obtained by wet milling and corn steeping liquid obtained by wet milling, and when steeped in 4 times its weight of distilled water, the pH of the distilled water after steeping is 4 to 8.
Food for raising beetles. 2. The beetle rearing feed according to claim 1, wherein when the gluten feed is soaked in four times its weight of distilled water, the electrical conductivity of the distilled water after soaking is less than 10 mS/cm. The feed for raising beetles according to claim 1 or 2, further comprising wheat bran. A method for producing the feed for raising beetles according to any one of claims 1 to 3,
The corn husk or gluten feed is prepared by:
The adjusting step
removing sulfur dioxide from the corn husks or the gluten feed;
mixing the corn husks or the gluten feed with an alkaline solution; or
washing the corn husks or gluten feed with an alkaline solution and/or water;
Manufacturing method. A method for producing the feed for raising beetles according to any one of claims 1 to 3,
The method includes adjusting the pH of the corn steep liquor to increase the pH and/or decrease the electrical conductivity. A beetle rearing method for rearing beetles using the beetle rearing feed described in any one of claims 1 to 3.