Preparation method and application of puffed corn with high digestibility

Abstract

The invention provides a preparation method and application of high-digestibility puffed corn, and belongs to the technical field of food processing. The preparation method comprises the specific steps of corn pretreatment, corn moisture content adjustment and extrusion puffing. After the corn is extruded and puffed, the contents of protein and total phosphorus of the corn are remarkably increased, the contents of fat and thermosensitive protein are reduced, the contents of anti-nutritional factors such as phytate phosphorus and arabinoxylan are reduced, and the hydration characteristic of the corn is improved. The prepared high-digestibility puffed corn is applied to beef cattle feed, the energy density of the feed and the digestibility of protein can be effectively improved, the palatability of the feed is improved, meanwhile, the digestibility of beef cattle to feed nutrient substances is improved, the intestinal health of the beef cattle is guaranteed, and the feed quality is improved. And theoretical and practical support is provided for expansion of local breeding industry and sustainable development of animal husbandry.

Description

Technical Field

[0001] The present invention belongs to the technical field of feed processing, and particularly relates to a preparation method and application of expanded corn with high digestibility. Background Art

[0002] Xing'an League annually produces about ten billion catties of corn, which is the most commonly used cereal feed. The corn starch content is about 70-80%, and its nutritional components are superior to most cereals, which can provide the main energy required by ruminant animals. However, the large size, poor taste, and small viscosity of corn grains result in poor palatability, low feed digestibility, and anti-nutritional factors, which limit its application in feed. Therefore, how to improve the palatability and nutritional value of corn-based feed has important research significance. Corn contains a crystal structure that resists acids and enzymes, resulting in low digestibility of corn. Corn contains a large amount of anti-nutritional factors - non-starch polysaccharides (None-starch polysaccharides, abbreviated as NSP). NSP is a polymer formed by connecting several monosaccharides and uronic acids through glycosidic bonds, including most polysaccharide molecules other than starch, and is generally difficult to be hydrolyzed by digestive enzymes secreted by monogastric animals themselves, resulting in low digestion and utilization rate of corn. The NSP in corn is mainly arabinoxylan, also known as pentosan or xylan. According to the solubility of arabinoxylan in water, it can be divided into water-soluble arabinoxylan and water-insoluble arabinoxylan. The arabinoxylan content in corn is 5.2%, accounting for about 63% of the total NSP, and the vast majority of which is water-insoluble arabinoxylan, accounting for about 98% of the total arabinoxylan. Existing research has shown that arabinoxylan has an anti-nutritional effect. When arabinoxylan is added to the diet, the digestibility of protein, fat, and amino acids significantly decreases, and the growth rate, feed conversion rate, and feed intake also significantly decrease. The extrusion processing technology can improve the quality of corn. The starch content is significantly or extremely significantly positively correlated with the extrusion degree of the extrudate. Corn contains 65-72% starch. After extrusion processing, the starch gelatinization degree of corn significantly increases, the palatability is improved, and the digestibility is significantly increased. Research shows that after being processed by the extrusion puffing process, the gelatinization degree of corn starch reaches over 90%, which is significantly improved compared with the traditional process. This process destroys the crystal structure, making the starch granules more easily hydrolyzed by enzymes effectively. It also helps with the organization of plant proteins, reduces the anti-nutritional factors in the feed, enhances the palatability of the feed, and improves the digestibility of nutrients. Although there is already a wealth of research on the processing parameters of corn puffed foods and the improvement of food quality abroad, due to the differences in the types and performances of puffing equipment and the variations in the physical and chemical properties of materials, it is very necessary to study the feed puffing process and the degradation law of its anti-nutritional factors. Therefore, disclosing a preparation method and application of high-digestibility puffed corn can not only provide good technical support for the intensive processing of corn, but also provide high-nutrition raw materials for livestock and poultry feed processing, with broad application prospects. Summary of the Invention

[0003] Technical problems to be solved: In view of the above technical problems, the object of the present invention is to provide a preparation method and application of high-digestibility puffed corn, and its specific steps include corn pretreatment, adjusting the moisture content of corn, and extrusion puffing, belonging to the technical field of food processing. After extrusion puffing, the protein and total phosphorus contents of the corn in the present invention are significantly increased, while the fat and thermosensitive protein contents are reduced. In addition, the contents of anti-nutritional factors such as phytic acid phosphorus and arabinoxylan are reduced, improving the hydration characteristics of corn. The high-digestibility puffed corn prepared by the present invention can be applied to beef cattle feed, effectively improving the energy density and digestibility of protein in the feed, enhancing the palatability of the feed, and at the same time improving the digestibility of feed nutrients by beef cattle, ensuring the intestinal health of beef cattle, and providing theoretical and practical support for the expansion of local aquaculture and the sustainable development of animal husbandry.

[0004] Technical solution: A preparation method of high-digestibility puffed corn includes the following steps: S1. Select good-quality corn, crush and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to make corn puffing raw materials; S3. Extrusion puff, dry, crush and sieve the corn puffing raw materials to obtain high-digestibility puffed corn. Further, in the step S2, the moisture content is 100 - 180 mg / kg. Further, in the step S3, the temperature of extrusion puffing is 130 - 150 °C. Further, in the step S3, the screw speed of extrusion puffing is 125 - 250 rpm. The high-digestibility puffed corn prepared by the method described in any one of the above. Further, the application of the high-digestibility puffed corn in the preparation of feed. Beneficial effects: 1. By subjecting corn to extrusion puffing treatment, the present invention can disrupt the molecular structure of the protein inside the corn, causing the hydrogen bonds and disulfide bonds of the protein to break, resulting in protein denaturation and making its structure become loose; at the same time, the starch crystal structure inside the corn is destroyed, leading to the disintegration of starch granules and the production of gelatinized starch with a reticular spatial structure, further making the structure of the puffed corn loose, which is beneficial to the enzymatic hydrolysis by the corresponding enzymes; in addition, it can significantly reduce the content of anti-nutritional factors such as phytic acid phosphorus and arabinoxylan, as well as the content of amylose, improve the nutritional digestibility of the puffed corn, and thus improve the digestibility of the puffed corn. 2. The high-digestibility puffed corn prepared by the present invention is applied to cattle feed, which can improve the energy density and protein digestibility of cattle feed, improve the palatability of cattle feed, and at the same time improve the digestibility of beef cattle to feed nutrients, providing a good additive choice for feed preparation raw materials, and at the same time providing strong data basis for the intensive processing and research of corn. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is the standard curve of arabinoxylan; Figure 2 are the water absorption index (WAI) and water solubility index (WSI) of Example 1 and Comparative Example 1, where Example 1 is denoted as puffed corn and Comparative Example 1 is denoted as corn; Figure 3 are the swelling potential (SP) of Example 1 and Comparative Example 1, where Example 1 is denoted as puffed corn and Comparative Example 1 is denoted as corn; Figure 4 are the gelatinization characteristic curves of Example 1 and Comparative Example 1, where Example 1 is denoted as puffed corn and Comparative Example 1 is denoted as corn. DETAILED DESCRIPTION OF THE INVENTION The present invention will be further described below in conjunction with embodiments. The following embodiments are explanations of the present invention and the present invention is not limited to the following embodiments: Example 1 A preparation method of high-digestibility puffed corn, comprising the following steps: S1. Select 500 g of good-quality corn, crush and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 140 mg / kg, and make corn puffing raw materials; S3. Extrusion puffing, drying, and crushing and sieving the corn puffing raw materials at 140 °C and a screw speed of 200 rpm to obtain high-digestibility puffed corn. Example 2 A preparation method of high-digestibility puffed corn, comprising the following steps: S1. Select 500 g of good-quality corn, crush and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 140 mg / kg, and make the corn puffed raw material. S3. Extrude, expand, dry, pulverize and sieve the corn puffed raw material at 130 °C with a screw speed of 200 rpm to obtain the high-digestibility puffed corn. Example 3 A preparation method of high-digestibility puffed corn, comprising the following steps: S1. Select 500 g of corn with good quality, pulverize and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 140 mg / kg, and make the corn puffed raw material. S3. Extrude, expand, dry, pulverize and sieve the corn puffed raw material at 150 °C with a screw speed of 200 rpm to obtain the high-digestibility puffed corn. Example 4 A preparation method of high-digestibility puffed corn, comprising the following steps: S1. Select 500 g of corn with good quality, pulverize and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 120 mg / kg, and make the corn puffed raw material. S3. Extrude, expand, dry, pulverize and sieve the corn puffed raw material at 140 °C with a screw speed of 200 rpm to obtain the high-digestibility puffed corn. Example 5 A preparation method of high-digestibility puffed corn, comprising the following steps: S1. Select 500 g of corn with good quality, pulverize and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 180 mg / kg, and make the corn puffed raw material. S3. Extrude, expand, dry, pulverize and sieve the corn puffed raw material at 140 °C with a screw speed of 200 rpm to obtain the high-digestibility puffed corn. Example 6 A preparation method of high-digestibility puffed corn, comprising the following steps: S1. Select 500 g of corn with good quality, pulverize and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 140 mg / kg, and make the corn puffed raw material. S3. Extrude, expand, dry, pulverize and sieve the corn puffed raw material at 140 °C with a screw speed of 150 rpm to obtain the high-digestibility puffed corn. Example 7 A preparation method of high-digestibility extruded corn, comprising the following steps: S1. Select 500 g of corn with good quality, crush and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to 140 mg / kg to make corn extrusion raw materials; S3. Extrude, dry and crush and screen the corn extrusion raw materials at 140 °C and a screw speed of 250 rpm to obtain high-digestibility extruded corn. Comparative Example 1 The difference between this comparative example and Example 1 is that the corn is not subjected to extrusion treatment. A preparation method of corn flour, comprising the following steps: S1. Select 500 g of corn with good quality, crush and dry it to make corn flour; Physical and chemical indexes (1) Nutritional component indexes Measure the moisture content, fat, protein, protein solubility, ash and total phosphorus of Examples 1-7 and Comparative Example 1. Among them, the moisture content is measured according to the method of GB / T6435-20014, the crude fat is measured according to the method of GB / T 6433-2006, the crude protein is measured according to the method of GB / T 6432-2018, the protein solubility is measured according to the method of GB / T 19541-2017, the crude ash is measured according to the method of GB / T 6438-2007, and the total phosphorus is measured according to the method of GB / T6437-2018. (2) Heat-sensitive protein After crushing the extruded corn samples of Examples 1-7 and Comparative Example 1, treat them with an extraction solution with the following formula: 13.6 g of potassium dihydrogen phosphate (KH2PO4), 4.2 g of dipotassium hydrogen phosphate (K2HPO4) and 20 g of sodium chloride (NaCl), and adjust the total volume to 2000 mL; use this extraction solution for oscillating extraction of the extruded corn samples for 3 min, then filter the extraction solution and keep it for subsequent use; take an appropriate amount of the filtered extraction solution and mix it with Coomassie Brilliant Blue staining solution in proportion and react for 15 min. During this process, use pure extraction solution as a blank control to eliminate systematic errors; use a spectrophotometer to measure the absorbance at a wavelength of 595 nm. Using bovine serum albumin as the standard protein, draw a standard curve, and quantitatively calculate the concentration of heat-sensitive protein by comparing the absorbance of the sample with the standard curve. Table 1 Nutritional component indexes of Examples 1-7 and Comparative Example 1 As can be seen from Table 1, the protein and total phosphorus contents of the examples are higher than those of Comparative Example 1, while the moisture, fat, protein solubility, heat-sensitive protein and ash are lower than those of Comparative Example 1, indicating that the extrusion treatment significantly changes the physical and chemical properties of corn through high temperature, high pressure and mechanical shearing: ① The moisture content is greatly reduced due to evaporation and starch gelatinization to form a porous structure; ② The fat combines with amylose to form a complex or volatilizes and is lost, resulting in a decrease in content; ③ The solubility of protein decreases due to heat denaturation, Maillard reaction and shear degradation, and the structure of heat-sensitive protein (such as zein) is damaged; ④ The ash content may decrease due to mineral volatilization or structural changes. At the same time, extrusion promotes complete starch gelatinization and decomposition of crude fiber, improves digestibility and inactivates pathogenic bacteria, ultimately making corn more easily absorbed and more hygienic, and suitable for feeds with high digestion requirements. (3) Phytate phosphorus The determination of phytate phosphorus adopts the precipitation digestion method: after the sample is crushed, it is extracted with 1.2% dilute hydrochloric acid, and after filtration, 1.0% ferric chloride phytate phosphorus precipitate is added to the filtrate. After digestion with nitric acid and sulfuric acid, it reacts with 10% ammonium molybdate to form phosphomolybdic acid; a color reaction is carried out with 2.0% ascorbic acid, and its absorbance value is measured at a wavelength of 660 nm. Finally, the phytate phosphorus content is determined by making a standard curve with a phosphorus standard solution. (4) Arabinoxylan The content of arabinoxylan is determined by the orcinol-hydrochloric acid method, and the operation steps are as follows: Take 100 mg of the sample and place it in a stoppered test tube, add 20 mL of 2 mol / L hydrochloric acid, seal it and heat it in a water bath at 100 °C for 2 h. After cooling, filter it, take 1 mL of the filtrate and transfer it to a 5 mL graduated test tube and dilute it to the mark; then accurately take 1 mL of the diluted solution and put it into a 15 mL graduated test tube, and successively add 2 mL of distilled water, 0.3 mL of 1% orcinol-ethanol solution, and 3 mL of 0.1% FeCl3-concentrated hydrochloric acid solution. After mixing, place the test tube in a boiling water bath and heat it for 30 min, then take it out and quickly cool it to room temperature; Use the double-wavelength method of an enzyme-linked immunosorbent assay (ELISA) reader to measure the absorbance value at a main wavelength of 670 nm and a baseline wavelength of 580 nm, record the absorbance value ΔA of the reaction solution, and draw a standard curve with the xylose concentration (c) as the abscissa as Figure 1 shown. (5) Amylose and amylopectin The determination of amylose and amylopectin contents adopts the double-wavelength colorimetric method, which is specifically as follows: Accurately weigh 0.1 g of amylose standard product into a beaker containing 10 mL of 1 mol / L potassium hydroxide solution, stir it in a water bath at 85 °C for 15 min to fully dissolve it, and after cooling, make the volume up to 50 mL to obtain an amylose standard working solution with a concentration of 2 mg / mL; The preparation method of the amylopectin standard working solution is the same as above; Establishment of starch standard curve: Respectively take 0.3, 0.5, 0.7, 0.9, 1.1, 1.3, 1.5 mL of amylose standard working solution and place them into a beaker containing 25 mL of distilled water. After adjusting its pH value to 3.0, add 0.5 mL of iodine reagent, and make up the volume to 50 mL with distilled water. Let it stand at room temperature for 25 min and conduct spectral analysis; for amylopectin, take 2.0, 2.5, 3.0, 3.5, 4.0, 4.5, 5.0 mL of the standard working solution, and the preparation and testing methods are the same as those for amylose. Table 2 Anti-nutritional factors of Examples 1-7 and Comparative Example 1 As can be seen from Table 2, the amylopectin content in the examples is higher than that in Comparative Example 1, while the phytic acid phosphorus, arabinoxylan, and amylose are lower than those in Comparative Example 1. This shows that after the corn is puffed, under the action of high temperature, high pressure, and mechanical shearing, the amylopectin will be exposed due to particle rupture and structural reorganization. At the same time, the amylose combines with fat to form a complex or degrades into resistant starch, resulting in a relatively reduced content; and the phytic acid phosphorus decreases due to high-temperature decomposition and combination with minerals, and the β-1,4 glycosidic bond of arabinoxylan breaks, dissolving or degrading into oligosaccharides, reducing the anti-nutritional properties. (6) Hydration properties Measure the hydration properties of Example 1 and Comparative Example 1, including water absorption index (WAI), water solubility index (WSI), and swelling potential (SP). The specific operation steps are as follows: Respectively take 1 g of the powder sample and the puffed sample, add an appropriate amount of distilled water to each, and adjust to a concentration of 5% to form an emulsion; place this emulsion in a weighed 50 mL centrifuge tube, and after uniform oscillation, place the centrifuge tube in a 30 °C water bath and maintain it for 30 min, during which it is oscillated every 5 min; after treatment, cool the centrifuge tube to room temperature, centrifuge at a speed of 5000 r / min for 10 min, then take the supernatant into an aluminum box that has been pre-dried to constant weight, put it into an oven at 105 °C and dry it to constant weight, and record the dry weight of the supernatant and the mass of the precipitate. The calculation formulas are as follows: Water absorption index (g / g) = mass of precipitate / dry weight of sample Water solubility index (%) = dry weight of supernatant / dry weight of sample × 100% Swelling potential (g / g) = mass of precipitate / dry weight of sample (1 - water solubility index). The water absorption index (WAI) can characterize the water absorption ability of starch, which is mainly related to the number of hydrophilic groups, while the water solubility index (WSI) can characterize the degradation degree of starch molecules. From Figure 2 and Figure 3It can be seen that the water absorption index and water solubility index of expanded corn are both significantly increased compared to corn. The water absorption index increases from 2.89 g / g to 5.88 g / g. Because during the extrusion process, the sample powder is under the combined action of high temperature, high pressure, and high-speed shear in the barrel cavity, the starch granules are damaged, and more hydrophilic groups are exposed, resulting in an increase in the water absorption index. Additionally, the high temperature decomposes the sample into soluble small molecules, significantly increasing the water solubility index. Moreover, the change trend of the swelling potential (SP) of expanded corn is consistent with the water absorption index, increasing from 2.95 g / g to 7.13 g / g. Because as the moisture content increases or the temperature rises, the starch structure is damaged, and the starch molecules are prone to absorb water and expand, thus increasing their swelling potential. (7) Gelatinization properties The gelatinization properties of Example 1 and Comparative Example 1 were measured as follows: 3 g of the sample was respectively placed into the measuring cup of a rapid viscosity analyzer, and 25 mL of distilled water was added. After placing it in the instrument, the measurement program started: within the first 10 s, the rotation speed was set to 960 r / min, and then the rotation speed was reduced to 160 r / min and continued until the end of the experiment. In terms of temperature control, it started at 50 °C and was maintained for 1 min, then heated to 95 °C at a rate of 12 °C and held for 2.5 min, and finally cooled to 50 °C at the same rate and held for 2 min. The gelatinization curve and related parameters of the starch were recorded and analyzed. Table 3 Gelatinization property indexes of Example 1 and Comparative Example 1 Note: In the subscripts of the same row, * indicates a significant difference (p < 0.05). From Table 3 and Figure 4 it can be seen that the gelatinization property indexes of Example 1 are all significantly lower than those of Comparative Example 1. The peak viscosity can characterize the water-holding capacity of starch granules. The peak viscosity decreased significantly from 4211 ± 48.82 mPa·s to 2389 ± 29.46 mPa·s, indicating that the extrusion expansion treatment significantly reduced the peak viscosity of corn, suggesting that the water-holding capacity of starch granules was affected. The decrease in peak viscosity is due to the action of high temperature and high pressure during the extrusion expansion process, resulting in the destruction of the starch granule structure. Additionally, the gelatinization of starch granules during the heat treatment allows water to penetrate more easily into the granule interior, further affecting its water-holding property. The breakdown value is the difference between the peak viscosity and the trough viscosity, which can characterize the thermal stability of starch granules. A smaller breakdown value means a larger decrease in viscosity during the heating of expanded corn, because the structure of starch granules is damaged, resulting in their easy disintegration during heating and weakened thermal stability. The breakdown value of expanded corn is significantly smaller than that of corn, indicating that the structure of starch granules was damaged during the extrusion expansion treatment, making the thermal stability of corn flour worse and the shear resistance weaker. The retrogradation value is the difference between the final viscosity and the trough viscosity, which is used to characterize the degree of starch molecular aging. The retrogradation value decreased from 2122 ± 4.13 mPa·s to 107 ± 3.74 mPa·s because extrusion treatment inhibited the rearrangement of amylose molecules during the cooling process, preventing the formation of new crystalline structures by starch molecules and effectively inhibiting starch retrogradation. Extrusion puffing treatment inhibited the rearrangement and crystallization processes of starch molecules. During natural cooling, untreated starch molecules tended to rearrange to form a more ordered structure, thus increasing the retrogradation value. However, puffing treatment physically disrupted the structure of starch granules, reducing intermolecular interactions and effectively inhibiting the retrogradation phenomenon. (8) Cattle feeding trial The expanded corn prepared in Example 1 and the corn flour in Comparative Example 1 were used to prepare diets for feeding non-pregnant cows. Two treatment groups (Example 1 group and Comparative Example 1 group) were set up, with 50 non-pregnant cows in each group. The diet ratios are shown in Table 4, and the treatment methods are shown in Table 5. The entire experiment lasted for two years. During the experiment, all cows were weaned early and supplemented with feed, allowed free access to food and water, and received timely hormone treatment according to actual needs. After the experiment, the apparent digestibility of nutrients was measured. Table 4 Diet formula of TMR diet for non-pregnant cows Note: The premix provides 8000 IU of vitamin A, 2400 IU of vitamin D, 30 mg of iron, 10 mg of copper, 40 mg of zinc, 40 mg of manganese, 0.1 mg of cobalt, 0.5 mg of iodine, and 0.5 mg of selenium per 1 kg of concentrate feed. Table 5 Apparent digestibility of nutrients for non-pregnant cows in Example 1 group and Comparative Example 1 group (%) Item Example 1 Group Control Example 1 Group Dry Matter DM 72.08±2.37 65.19±2.03 Crude Protein CP 71.77±5.23 63.77±3.56 Neutral Detergent Fiber NDF 55.22±4.80 43.22±3.23 Acid Detergent Fiber ADF 49.98±4.77 40.98±4.28 Starch Digestibility 74.08±2.17 65.28±2.28 As can be seen from Table 5, in Example 1, expanded corn was used to prepare cattle feed for feeding non-pregnant cows, and the apparent digestibility of dry matter, crude protein, neutral detergent fiber, acid detergent fiber, and starch digestion rate were all higher than those in Comparative Example 1 (corn without extrusion treatment). This shows that extrusion-treated corn can, on the one hand, rupture and gelatinize starch granules, expose amylopectin, and reduce resistant starch, further improving the enzymatic hydrolysis efficiency of the gastrointestinal tract after non-pregnant cows eat the feed and increasing the starch digestion rate. On the other hand, it destroys the β-1,4 glycosidic bond of arabinoxylan and the cellulose structure, increases the fiber surface area, promotes the colonization of rumen fiber-degrading bacteria, and can improve the digestibility of NDF and ADF. In addition, the heat denaturation produced by extrusion treatment loosens the structure of zein, reduces the inhibition of digestion by the degradation of phytic acid phosphorus, and improves the digestibility of crude protein. All in all, expanded corn can lay a foundation for improving the energy supply, digestion and absorption, and reproductive performance of non-pregnant cows. The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Any person skilled in the art can make many possible changes and modifications to the technical solution of the present invention by using the methods and technical contents disclosed above, or modify it into an equivalent embodiment with equivalent changes. Therefore, any simple modification, equivalent replacement, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution of the present invention still fall within the scope of protection of the technical solution of the present invention.

Claims

1. A preparation method of high-digestibility puffed corn, characterized in that, It includes the following steps: S1. Select good-quality corn, crush and dry it to make corn flour; S2. Mix the corn flour with water evenly, adjust the moisture content to make corn puffing raw materials; S3. Subject the corn puffing raw materials to extrusion puffing, drying, crushing and sieving to obtain high-digestibility puffed corn.

2. The preparation method of a highly digestible expanded corn according to claim 1, characterized in that: In step S2, the moisture content is 100-180 mg / kg.

3. The preparation method of a highly digestible expanded corn according to claim 1, characterized in that: In step S3, the temperature of extrusion puffing is 130-150 °C.

4. The preparation method of a highly digestible expanded corn according to claim 1, characterized in that: In step S3, the screw speed of extrusion puffing is 125-250 rpm.

5. High-digestibility puffed corn prepared by the method according to any one of claims 1-5.

6. Use of the high-digestibility puffed corn according to claim 6 in the preparation of feed.

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