CN106261493A - A kind of corn powder and preparation method thereof - Google Patents

Abstract

The invention discloses a kind of corn powder and preparation method thereof.The step of the method includes: soaking sterilization after corn kernel cleaning, after soaking water suction, enters under low temperature, low humidity, non-illuminated conditions, carries out cultivation of sprouting, and after preparing coarse powder, regulates moisture, carries out gentle extrusion process, after finely divided, can obtain corn powder.The present invention limits to sprout to extrude with gentleness and combines, the corn powder the first limiting amino acids lysine content obtained is increased to 29.85mg/g protein by 21.33mg/g, water soluble dietary fiber/total dietary fiber is increased to 50.88% by 15.11%, fat content is reduced to 1.83% by 3.62%, nutrient health be worth be improved significantly.

Description

A kind of whole corn flour and preparation method thereof

technical field

The invention relates to a whole corn flour and a preparation method thereof, in particular to a whole corn flour prepared by combining germination technology and extrusion technology and a preparation method thereof, belonging to the field of food processing.

Background technique

Corn kernels are rich in nutrients. According to reports, dry corn grains contain protein: 5.8% to 9.0%, fat: 3.9% to 4.6% (of which essential linoleic acid accounts for 19% to 71%), starch: 70.6% to 76.5%, and are also rich in Dietary fiber, vitamin B, vitamin E, and trace elements necessary for the human body. Corn food has important functions of anti-aging, anti-oxidation, lowering serum cholesterol level, and promoting cardiovascular health. The development and utilization of corn food are attracting more and more attention.

The health value of whole grain foods has been widely recognized. The FDA of the United States clearly stipulates that foods containing more than 51% whole grains can be labeled with the following health claims: a diet rich in whole grains has low fat, low saturated fatty acid and low cholesterol content, which can reduce the risk of heart disease and specific cancers. Due to the rich nutritional value and special health effects of corn, the use of corn to prepare whole grain products has broad application prospects.

After the grain is damp and absorbs water, various enzymes start to activate, and the respiration and metabolism are enhanced; the embryo begins to grow, and the nutrients stored in the seed begin to decompose and consume; after a certain period of time, the seed embryo breaks through the seed coat, exposes the radicle, and grows a germ. During the process of grain germination, its nutritional composition and physical and chemical properties will undergo major changes. Germination helps to improve the nutritional value of grains, reduce and eliminate harmful substances and anti-nutritional substances. The application of grain seed germination technology in food processing has become a research hotspot at home and abroad.

At present, the main way of eating corn is to break the ballast or grind it after peeling, but because of the lack of essential amino acids such as lysine in the protein composition, corn is mainly eaten by people as an auxiliary staple food, which makes the nutritional and health value of corn unable to reach. be fully utilized. Using germination technology to promote the effective transformation of dietary fiber in corn into soluble dietary fiber, increase the content of essential amino acids and B vitamins, and promote the absorption of trace elements such as zinc and iron will be an effective way to improve the utilization of corn.

There have been some methods for preparing germinated whole grains at home and abroad. It is to germinate the grains to a certain sprout length to obtain a product composed of young sprouts and endosperm with cortex, then dry it and make powder, and mix it with other functional components. Combine with whole grain products. However, sprouted food also has certain defects. For example, after the buds grow out, the degradative enzyme activity is usually strong, and the starch is converted into reducing sugar in a large amount (starch degradation rate > 20%), so it is difficult to be used for the preparation of low glycemic index (GI). Grain products; in addition, there is also the problem of deterioration of processing quality due to excessive germination, and it is also accompanied by a certain raw green odor.

Extrusion is a widely used technology in the current food processing industry. Materials are restructured through mixing, stirring and friction under high temperature and high pressure, as well as high shear force. Extrusion technology mostly uses high temperature, high pressure, and high moisture content to promote the gelatinization of corn starch, which degrades part of the starch and generates dextrin and soluble reducing sugar. This is an effective process for preparing traditional extrusion puffed foods, but it is applied to When preparing whole grain flour, due to excessive starch degradation (starch degradation rate > 20%) and a large amount of reducing sugar, the application value of whole grain flour with low GI is lost. Therefore, choosing a reasonable extrusion process is the key to preparing whole grain with low GI The important direction of powder.

Contents of the invention

The invention overcomes the disadvantages of the above-mentioned prior art, and provides a whole corn flour and a preparation method thereof. In the method, corn is used as raw material, and a low GI corn whole flour product is prepared by using restricted germination + mild extrusion technology. The germination technology of the present invention controls the appropriate temperature and humidity conditions, only promotes the germination of grains, and avoids the problem of quality deterioration caused by bud growth. The invention adopts gentle extrusion technology, degrades insoluble dietary fiber (IDF) into soluble dietary fiber (SDF) on the basis of germination, reduces fat content, improves the composition of healthy components of corn flour, and improves the edibility of whole corn flour , while avoiding the problem of high GI value caused by excessive starch degradation. The preparation method of the invention is simple and easy for industrialized production.

The technical scheme of the present invention is: a kind of whole corn meal preparation method, it is characterized in that,

(1) Soak the corn grains with a concentration of 0.3-0.6% sodium hypochlorite solution for 30-60 minutes, sterilize them, and then clean them with distilled water to avoid residual sodium hypochlorite; preferably, the sodium hypochlorite concentration is 0.5%, and the soaking time is 30 minutes;

(2) Then add water to soak for 6-12 hours; preferably, the soaking temperature is 24-30°C (more preferably 25°C), and the soaking time is preferably 8h;

(3) Put the soaked corn kernels into a germination tray with a filter cloth at the bottom, place the germination tray in a constant temperature and humidity incubator with a temperature of 15-20°C and a humidity of 70%-80%, without light Cultivate for 28-36 hours to obtain germinated corn kernels (no obvious corn sprouts grow); during the germination process, keep the temperature and humidity constant, and do not add water to the germination tray;

(4) The water content of the germinated corn kernels is 14-16%, and it does not need to be dried, and it is directly coarsely crushed, and the fineness is 40-80 mesh;

(5) Add water, adjust the moisture content of coarse corn flour to be 12-18% (preferably 16%), and stir evenly;

(6) The above materials are extruded by a twin-screw extruder, the screw speed is 90-130rpm, and the extrusion temperature is ≤120°C. During the specific operation, the temperature of the first section is 70-80°C; the temperature of the second section is 90°C. ～110℃; the temperature of the third stage is 100～120℃;

The screw speed is preferably 100 rpm; the temperature in the first stage is preferably 70°C, the temperature in the second stage is 95°C, and the temperature in the third stage is 110°C.

(7) Finely pulverize the extruded material and pass through an 80-mesh sieve to obtain whole corn flour.

The whole corn powder prepared by the above method has a soluble dietary fiber/total dietary fiber content of ≥50.0%, a fat content of ≤2.0%, and a reducing sugar content of ≤8%. Compared with whole corn flour without germination and extrusion treatment, the content of lysine increased by >60%, the content of soluble dietary fiber/total dietary fiber increased by >200%, the content of fat decreased by >45%, and the nutritional and health value was significantly improved.

The corn kernels used in the present invention are commonly harvested corn kernels, which are used after removing moldy and broken kernels and removing impurities in the corn kernels.

The present invention uses low temperature and suitable humidity to control the growth of buds. The main difference between germination and germination is that germination only starts catabolism and is controlled to avoid excessive catabolism, large consumption of substrates, and product quality degradation. No water is added during the cultivation process to control the germination state and prevent the germ growth from breaking through the seed coat. At the same time, by controlling a reasonable humidity environment, the water absorbed by the corn kernels during the soaking process is gradually lost to the surrounding environment with germination. At the end of germination, The moisture content of the corn kernels reaches the level that can be directly put into the mill without adding a drying process.

Among them, the main purpose of twin-screw extrusion is to further degrade dietary fiber into soluble dietary fiber, while reducing fat content, so that whole corn flour can be stored safely. The extruding process of the present invention is gentle extruding, adopts lower material moisture content, low rotational speed, and low temperature, protects the essential amino acids produced by germination from being damaged; reduces starch gelatinization degree, and avoids excessive reducing sugar generation.

The beneficial effects of the present invention are:

1. The preparation method of whole corn flour of the present invention combines germination technology with extrusion technology, adopts germination technology to moderately degrade dietary fiber, strengthens restrictive amino acids, and further degrades dietary fiber and fat content in combination with extrusion technology, changing the method of simply relying on The disadvantage of deteriorating product quality due to germination and strengthening of nutritional components, or the problem of a decrease in essential amino acids caused by simply relying on extrusion;

2. The germination method of the whole corn flour of the present invention before extrusion adopts a limited germination process, adopts measures such as low temperature and low humidity conditions, and does not add water to control the conversion of starch into reducing sugars in large quantities due to the high activity of amylase, which leads to the later stage The glycemic index is too high during consumption, and the hypoglycemic effect of whole corn flour is lost; by controlling the activity of lipoxygenase and peroxidase, excessive germination and green taste are avoided;

3. The germination method of the whole corn flour of the present invention before extrusion gradually reduces the moisture content in the germination process until the moisture is reduced to 14-16% when the germination is completed, and can directly enter the milling process without using the current germination process. The drying process realizes process simplification and reduces energy consumption;

4. The extruding method of whole corn powder of the present invention after germination continues the defects of low dietary fiber degradation caused by limited germination and basically no change in fat content, and promotes the degradation of part of the insoluble dietary fiber into soluble dietary fiber by extrusion ; At the same time, the fat content is reduced to facilitate the safe storage of whole corn flour;

5. The germination extrusion method of whole corn flour of the present invention adopts a gentle extrusion process, the moisture content of the material is low, the screw speed is low, the extrusion temperature does not exceed 120°C, basically has no destructive effect on essential amino acids, and reduces starch The degree of gelatinization and the content of amylose are basically unchanged, which ensures the low glycemic index of whole corn flour;

6. The whole corn flour preparation method of the present invention, the first limiting amino acid lysine content of the whole corn flour obtained increases from 21.33mg/g to 29.85mg/g protein, and the soluble dietary fiber/total dietary fiber increases by 15.11% to 50.88%, the fat content was reduced from 3.62% to 1.83%, and the nutritional and health value was significantly improved.

Description of drawings

Fig. 1 is the schematic diagram that the present invention adopts the combination of germination and extrusion to prepare high nutritional value corn flour;

Fig. 2 is the change figure of soluble dietary fiber/total dietary fiber (SDF/TDF) during (different germination time) corn grain germination of the present invention;

Fig. 3 is the change figure of protein content (different germination time) during corn grain germination of the present invention;

Fig. 4 is a graph showing changes in lysine content during the germination period (different germination time) of corn grains of the present invention.

detailed description

The present invention will be described in detail below in combination with specific embodiments. The following examples are used to illustrate the present invention, but are not intended to limit the scope of the present invention. Unless otherwise specified, the technical means used in the examples are conventional means well known to those skilled in the art, and the raw materials used are all commercially available products.

In the following examples, the determination of soluble dietary fiber, insoluble dietary fiber and total dietary fiber adopts the GB/T5009.88-2008 enzyme mass method; the determination of protein content adopts the Kjeldahl method; the determination of lysine content adopts the ninhydrin method; Amino acid determination adopts GB/T 5009.124-2003 method; fat content determination adopts GB/T 5009.6-2003 method; starch content determination adopts GB/T 5009.9-2008 method; reducing sugar content determination adopts GB/T 5009.7-2008 method.

Example 1

(1) Take 5000g corn kernels, select, remove moldy and broken kernels, remove impurities in the corn kernels, soak in 0.4% sodium hypochlorite solution for 40min, sterilize, then wash 3 times with distilled water to avoid sodium hypochlorite residues;

(2) Add pure water and soak for 8 hours at 25°C;

(3) Spread the soaked corn evenly in a germination tray that has been sterilized and covered with a filter cloth at the bottom, and place it in a constant temperature and humidity incubator with a temperature of 16°C and a humidity of 70%-80%, and carry out under the condition of no light. During the cultivation and germination process, the temperature and humidity were kept constant, no water was added to the germination tray, and the cultivation time was 0-48 hours to obtain germinated corn kernels, and no obvious corn sprouts were seen.

(4) Coarsely pulverize the germinated corn kernels with a fineness of 40-80 meshes; determine the dietary fiber, protein and lysine contents of the corn meal. The results are shown in Figure 2, Figure 3 and Figure 4. It can be seen from the figure that with the increase of germination time, the content of soluble dietary fiber (SDF)/total dietary fiber and lysine gradually increased, while the protein content decreased slightly. Among them, the soluble dietary fiber/total dietary fiber reached the maximum at 28-32h, which was 30.97±0.99%, and then began to decline, and the lysine content also reached a high 0.676±0.041%, so it is more appropriate to choose 28-36h.

Example 2

(1) Take 5000g corn kernels, select, remove moldy and broken kernels, remove impurities in the corn kernels, soak in 0.4% sodium hypochlorite solution for 40min, sterilize, then wash 3 times with distilled water to avoid sodium hypochlorite residues;

(2) Add pure water and soak for 8 hours at 25°C;

(3) Spread the soaked corn evenly in a germination tray that has been sterilized and covered with a filter cloth at the bottom, and place it in a constant temperature and humidity incubator with a temperature of 16°C and a humidity of 70%-80%, and carry out under the condition of no light. Cultivate, during the cultivation process, keep the temperature and humidity constant, do not add water to the germination tray, and cultivate for 32 hours to obtain germinated corn kernels, no obvious corn sprouts grow, and there is no raw green smell;

(4) Coarsely pulverizing the germinated corn kernels with a fineness of 40-80 mesh;

(5) adding the coarse corn flour to pure water by weight to adjust the water content to 18%, and stirring evenly;

(6) The above materials are extruded by a twin-screw extruder, the screw speed is 100rpm, the temperature of the first section is 70°C; the temperature of the second section is 100°C; the temperature of the third section is 110°C;

(7) After drying and pulverizing the extruded material, pass through an 80-mesh sieve, and the gained is corn flour; the dietary fiber, protein, and lysine contents of the corn flour are measured, and the results are shown in Table 1. The obtained whole corn flour was taken to determine the amino acid composition, and the results are shown in Table 2. The fat content, reducing sugar and starch content of the whole corn flour were measured, and the results are shown in Table 3.

Table 1 Effect of germination-extrusion treatment on soluble dietary fiber, lysine and protein content of whole corn flour

deal with SDF/TDF(%) Lysine (mg/g protein) Protein content (%) Whole Corn Meal 15.11±1.09 21.33±2.36 9.96±0.13 Whole sprouted corn flour 30.97±0.99 30.85±1.17 9.88±0.09 Sprout - Whole Extruded Corn Flour 50.88±2.74 29.85±1.26 9.65±0.17

It can be seen from Table 1 that the content of SDF/TDF increased significantly after extrusion treatment, reaching more than 3 times that of untreated whole corn flour, and the content of lysine was also significantly higher than that of whole corn flour without germination-extrusion treatment. The protein content did not change much, showing that the germination-extrusion treatment did not significantly reduce the protein content of whole corn flour, and maintained a good nutritional composition of whole corn flour. At the same time, it can be seen from Table 1 that the content of SDF/TDF increases significantly by about 65% after extrusion.

Table 2 The effect of germination-extrusion treatment on the amino acid composition of whole corn flour (unit: mg/g protein)

It can be seen from Table 2 that the germination-extrusion treatment changed the amino acid composition of corn gluten, and among the 8 essential amino acids, leucine, isoleucine, and threonine decreased, but they were still higher than the essential amino acids recommended by FAO/WHO Mode, sulfur-containing amino acids and aromatic amino acids did not change much, and were higher than the essential amino acid mode recommended by FAO/WHO. The content of limiting amino acids lysine and tryptophan was greatly increased, indicating that the sprouting-extrusion technology improved protein nutritional value.

Table 3 Effects of germination-extrusion treatment on fat content, reducing sugar and starch content of whole corn flour

deal with Fat content (%) Reducing sugar content (%) Starch content (%) Whole Corn Meal 3.62±0.08 4.12±0.09 68.91±2.78 Whole sprouted corn flour 3.36±0.08 4.95±0.11 66.24±2.82 Sprout - Whole Extruded Corn Flour 1.83±0.05 7.73±0.15 62.16±2.53

It can be seen from Table 3 that the fat content decreased significantly after extrusion treatment, from 3.62% to 1.83%. After germination treatment, the starch content did not change significantly; after extrusion treatment, the starch content decreased slightly, with a decrease rate of <10%, and the obtained product was a whole grain product with low GI.

Example 3

(1) Take 8000g corn kernels, select, remove moldy and broken kernels, remove impurities in the corn kernels, soak in 0.5% sodium hypochlorite solution for 30 minutes, sterilize, then wash 3 times with distilled water to avoid sodium hypochlorite residues;

(2) Add pure water and soak for 7 hours at 28°C;

(3) Spread the soaked corn evenly in a germination tray that has been sterilized and covered with a filter cloth at the bottom, and place it in a constant temperature and humidity incubator with a temperature of 18°C and a humidity of 70%-80%, and carry out under the condition of no light. Cultivate, during the germination process, keep the temperature and humidity constant, do not add water to the germination tray, and cultivate for 28 hours to obtain germinated corn kernels without green taste;

(4) Coarsely pulverizing the germinated corn kernels with a fineness of 40-80 mesh;

(5) adding coarse corn flour to purified water to adjust the water content to 16%, and stirring evenly;

(6) The above materials are extruded by a twin-screw extruder, the screw speed is 90rpm, the temperature of the first section is 80°C; the temperature of the second section is 100°C; the temperature of the third section is 120°C;

(7) After drying and pulverizing the extruded material, pass through an 80-mesh sieve to obtain whole corn flour.

After testing, the obtained whole corn powder has a soluble dietary fiber/total dietary fiber content of ≥50.0%, a fat content of ≤2.0%, and a reducing sugar content of ≤8%.

Although the present invention has been described in detail with general descriptions and specific embodiments above, it is obvious to those skilled in the art that some modifications or improvements can be made on the basis of the present invention. Therefore, the modifications or improvements made on the basis of not departing from the spirit of the present invention all belong to the protection scope of the present invention.

Claims (10)

1. a corn powder preparation method, is characterized in that,

(1) corn kernel is sterilized, then clean up with water；

(2) water soaking 6～12h it is subsequently adding；

(3) soaked corn kernel being put into bottom to be covered with in the germination dish of filter cloth, it is 15～20 DEG C that germination dish is placed in temperature, wet In the degree constant temperature and humidity incubator for 70%-80%, carry out cultivating 28～36h under non-illuminated conditions, it is thus achieved that niblet of sprouting；Send out During bud, keep temperature, humidity constant, do not add water in germination dish；

(4) niblet of sprouting need not be dried, and directly carries out coarse pulverization, and fineness is 40～80 mesh, it is thus achieved that grits；

(5) adding water, adjusting grits moisture is 12～18%, stirs；

(6) above-mentioned material employing twin (double) screw extruder being carried out extrusion process, screw speed is 90～130rpm, extrusion temperature≤ 120℃；

(7) extruding gained material is carried out finely divided after, gained is corn powder.

2. a kind of corn powder preparation method as claimed in claim 1, is characterized in that, described twin (double) screw extruder, first paragraph Temperature is 70～80 DEG C；Second segment temperature is 90～110 DEG C；3rd section of temperature is 100～120 DEG C.

3. a kind of corn powder preparation method as claimed in claim 2, is characterized in that, described twin (double) screw extruder, first paragraph Temperature is 70 DEG C, and second segment temperature is 95 DEG C, and the 3rd section of temperature is 110 DEG C.

4. a kind of corn powder preparation method as claimed in claim 1, is characterized in that, described screw speed is 100rpm.

5. a kind of corn powder preparation method as claimed in claim 1, is characterized in that, the sterilization of described step (1) is for dense Degree be 0.3～0.6% liquor natrii hypochloritis soak 30～60min.

6. a kind of corn powder preparation method as claimed in claim 1, is characterized in that, described step (2) soaking temperature is 24 ～30 DEG C.

7. a kind of corn powder preparation method as claimed in claim 1, is characterized in that, described step (3) cultivation temperature is 16 DEG C, incubation time is 32h.

8. a kind of corn powder preparation method as claimed in claim 1, is characterized in that the corn kernel of described step (1) removes Remove seed mouldy, broken, remove in corn kernel and use after impurity.

9. the corn powder that in claim 1-8 prepared by method described in any one.

10. corn powder as claimed in claim 9, is characterized in that, water soluble dietary fiber/total dietary fiber >= 50.0%, fat content≤2.0%, content of reducing sugar≤8%.