Nutrient enrichment type low-GI whole wheat flour and preparation method thereof

Abstract

The invention belongs to the technical field of food processing, and particularly relates to nutrient enrichment type low-GI whole wheat flour and a preparation method thereof. The method comprises the following steps: putting wheat grains into superheated steam for inactivation treatment, and performing superfine grinding by adopting a low-temperature impact mill to obtain whole wheat flour; and uniformly mixing the whole wheat flour, soluble polysaccharide, transglutaminase and natural active substances, and grinding by adopting a low-temperature medium mill to obtain the nutrient enrichment type low-GI whole wheat flour. The whole wheat flour, the soluble polysaccharide, the transglutaminase and the natural active substances are jointly ground by adopting a low-temperature medium mill, and the generated mechanochemical effect promotes the interaction among the components, so that the structural properties of the components such as wheat starch and gluten protein are improved; the texture formation of the whole wheat flour in the processing and application process is facilitated, the GI (glycemic index) is reduced, and the nutritional quality is improved.

Description

Technical Field

[0001] This application belongs to the field of food processing technology, specifically relating to a nutritionally fortified low-GI whole wheat flour and its preparation method. Background Technology

[0002] Wheat is one of my country's important staple grain crops, and wheat flour is its main processed product. In recent years, the number of diabetic patients has been increasing annually. As a crucial staple food ingredient, wheat flour is essential for the daily healthy diet of people with diabetes and other special needs. Low-GI wheat flour has attracted much attention due to its outstanding nutritional advantages. Furthermore, with increasing health awareness, the development of whole-grain foods such as whole wheat flour has become an urgent need for the development of the grain industry. However, whole wheat flour retains the bran and germ, containing abundant insoluble dietary fiber and highly active endogenous enzymes such as lipase and lipoxygenase. This leads to problems such as easy rancidity during storage, short shelf life, and difficulties in the formation of gluten structure during processing, resulting in a coarse product texture. Therefore, it is necessary to improve the storage stability and processing adaptability of whole wheat flour. In addition, ordinary whole wheat flour, due to its limited nutritional components and flavor, can no longer meet consumer demands. Developing whole wheat flour with nutritional and health benefits is more in line with the health trend of dietary therapy.

[0003] Currently, the processing of fortified and low-GI wheat flour mainly involves simply mixing wheat flour with functional active substances, soluble polysaccharides, and other adjuvants. This primarily improves the nutritional quality of wheat flour and its products by adding these adjuvants. However, this simple mixing of raw and auxiliary materials fails to alter the chemical structure, resulting in minimal improvement in the sensory quality and health benefits of wheat flour and its processed products. Therefore, it is necessary to improve existing processes to produce high-quality whole wheat flour with superior sensory quality, lower GI values, and enhanced health benefits. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a nutritionally fortified low-GI whole wheat flour and its preparation method, specifically adopting the following technical solution: In a first aspect, the present invention provides a method for preparing nutritionally fortified low-GI whole wheat flour, comprising the following steps: Wheat grains are inactivated by superheated steam and then ultra-finely pulverized using a low-temperature impact mill to obtain whole wheat flour. The whole wheat flour, soluble polysaccharide, transglutaminase and natural active substances are mixed evenly to obtain a mixture, which is then ground using a low-temperature media mill to obtain the nutritionally fortified low-GI whole wheat flour.

[0005] This invention addresses the problems of rancidity and short shelf life of whole wheat flour during storage by treating wheat grains with superheated steam to inactivate enzymes (lipases and lipoxygenases) and stabilize the raw materials. It also utilizes a low-temperature impact mill to prepare ultrafine whole wheat flour, achieving ultra-fine grinding of wheat dietary fiber and resolving the issue of a coarse texture. Furthermore, by co-grinding whole wheat flour with soluble polysaccharides, transglutaminase (TG), and natural active substances in a low-temperature media mill, the mechanical chemical effect induces interactions between components, altering the structural properties of wheat starch, gluten protein, and other components, and further reducing the particle size of the product. This improves the processing adaptability of whole wheat flour, enhances the sensory and nutritional quality of processed products, and reduces the hematopoietic index (GI).

[0006] As a further preferred embodiment, the temperature of the superheated steam is 110℃-120℃, and the inactivation treatment time is 1min-5min.

[0007] As a further preferred embodiment, the temperature during ultrafine pulverization using a low-temperature impact mill is 10℃-20℃; The particle size D90 of the whole wheat flour is ≤80μm.

[0008] As a further preferred embodiment, the soluble polysaccharide includes at least one of pectin, β-glucan, gum arabic, xanthan gum, soluble soybean polysaccharide, tremella polysaccharide, shiitake mushroom polysaccharide, and wolfberry polysaccharide.

[0009] As a further preferred embodiment, the amount of soluble polysaccharide used is 3%-8% of the mixture.

[0010] As a further preferred embodiment, the natural active substance includes at least one of anthocyanins, carotenoids, betaine, and chlorophyll.

[0011] As a further preferred embodiment, the amount of the natural active substance is 0.01%-1% of the mixture.

[0012] As a further preferred embodiment, the initial enzyme activity of the transglutaminase is 100-130 U / g, the amount of the transglutaminase is 0.02%-0.3% of the mixture, and the amount of whole wheat flour is 90.7%-96.97% of the mass of the mixture.

[0013] Secondly, the present invention provides a nutritionally fortified low-GI whole wheat flour, which is prepared by the above-described preparation method.

[0014] As a further preferred embodiment, the particle size D90 of the fortified low-GI whole wheat flour is ≤10μm.

[0015] This invention pretreats wheat with superheated steam and a low-temperature impact mill to prepare ultrafine whole wheat flour with inactivated enzymes. Then, the whole wheat flour, soluble polysaccharides, transglutaminase (TG), and natural active substances are co-ground in a low-temperature media mill. The mechanochemical effect causes interactions between the components, altering the structural properties of wheat starch, gluten, and other components, and further reducing the particle size of the product. This improves the processing adaptability of the whole wheat flour, enhances the sensory and nutritional quality of the processed products, and reduces the glycemic index (GI), producing a nutritionally fortified low-GI whole wheat flour with excellent sensory quality.

[0016] The beneficial effects of this invention are as follows: (1) The present invention uses a low-temperature media mill to grind the whole wheat flour, soluble polysaccharides, transglutaminase (TG), and natural active substances together. The resulting mechanochemical effect promotes non-covalent interactions between components and improves the structural properties of components such as wheat starch and gluten protein, thereby facilitating the formation of texture, reduction of glycemic index (GI), and improvement of nutritional quality of whole wheat flour during processing and application.

[0017] (2) The present invention significantly reduces the particle size of whole wheat flour by using low-temperature impact milling and low-temperature media milling to perform secondary grinding of whole wheat flour, thereby improving the problem of rough texture of insoluble dietary fiber. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 The diagram shows the production process flow of nutritionally fortified low-GI whole wheat flour. Detailed Implementation

[0020] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0021] Example 1 A method for preparing a nutritionally fortified low-GI whole wheat flour, specifically including the following steps: (1) Wheat grains were placed in superheated steam at 120℃ for 3 minutes, and then crushed using a low-temperature impact mill at 15℃, main machine frequency of 35Hz, classifier frequency of 40Hz, and induced draft fan frequency of 30Hz to obtain a particle size D. 90 Whole wheat flour with a particle size of 80μm; (2) Add 5% by mass of β-glucan, 0.02% by mass of proanthocyanidins, 0.1% by mass of TG enzyme (initial enzyme activity 120 U / g), and 94.88% by mass of whole wheat flour to a powder mixer and mix for 5 min. Then add the powder mixture to a low-temperature media mill, set the temperature of the low-temperature media mill to 5℃, the diameter of the grinding media to 2 mm, the media filling amount to 55%, and the grinding time to 2 h to obtain D. 90 It is a nutritionally fortified low-GI whole wheat flour with an 8μm particle size.

[0022] Example 2 A method for preparing a nutritionally fortified low-GI whole wheat flour, specifically including the following steps: (1) Wheat grains were placed in superheated steam at 110℃ for 5 minutes, and then the wheat grains were crushed by low temperature impact mill at 20℃, main machine frequency of 40Hz, classifier frequency of 50Hz and blower frequency of 50Hz to obtain whole wheat flour with a particle size D90 of 70μm. (2) Add 5% by mass of Tremella polysaccharide, 0.05% by mass of β-carotene, 0.2% by mass of TG enzyme (initial enzyme activity 120U / g), and 94.75% by mass of whole wheat flour to a powder mixer and mix for 5 minutes. Then add the powder mixture to a low-temperature media mill and set the temperature of the low-temperature media mill to 5°C, the diameter of the grinding media to 2 mm, the media filling amount to 55%, and the grinding time to 5 hours to obtain a nutritionally fortified low-GI whole wheat flour with a D90 of 4 μm.

[0023] Example 3 A method for preparing a nutritionally fortified low-GI whole wheat flour, specifically including the following steps: (1) Wheat grains were placed in superheated steam at 110℃ for 5 minutes, and then the wheat grains were crushed by low temperature impact mill at 10℃, main machine frequency of 40Hz, classifier frequency of 50Hz and blower frequency of 50Hz to obtain whole wheat flour with a particle size D90 of 70μm. (2) Add 6% lentinan, 0.08% chlorophyll, 0.3% TG enzyme (initial enzyme activity 120U / g), and 93.62% whole wheat flour to a powder mixer and mix for 5 minutes. Then add the powder mixture to a low-temperature media mill. Set the temperature of the low-temperature media mill to 4℃, the diameter of the grinding media to 2mm, the media filling amount to 55%, and the grinding time to 10h to obtain a nutritionally fortified low-GI whole wheat flour with a D90 of 1μm.

[0024] Comparative Example 1 A method for preparing whole wheat flour, specifically including the following steps: Wheat grains were treated in superheated steam at 120℃ for 3 minutes, and then pulverized using a low-temperature impact mill at 15℃, a main machine frequency of 35Hz, a classifier frequency of 40Hz, and an induced draft fan frequency of 30Hz to obtain a particle size D. 90 Whole wheat flour with a particle size of 80μm.

[0025] Comparative Example 2 A method for preparing compound whole wheat flour, specifically including the following steps: (1) Place wheat grains in superheated steam at 120℃ for 3 minutes, then crush the wheat grains using a common blade-type universal pulverizer for 6 minutes. At this point, the maximum crushing particle size of the equipment is reached, and the particle size D is obtained. 90 It is 500μm whole wheat flour.

[0026] Comparative Example 3 A method for preparing compound whole wheat flour, specifically including the following steps: (1) Wheat grains were placed in superheated steam at 120℃ for 3 minutes, and then crushed using a low-temperature impact mill at 15℃, main machine frequency of 35Hz, classifier frequency of 40Hz, and induced draft fan frequency of 30Hz to obtain a particle size D. 90 Whole wheat flour with a particle size of 80μm.

[0027] (2) Add 5% β-glucan, 0.02% proanthocyanidins, 0.1% TG enzyme (initial enzyme activity 120U / g), and 94.88% whole wheat flour to a powder mixer and mix for 5 minutes to obtain compound whole wheat flour.

[0028] Comparative Example 4 A method for preparing compound whole wheat flour, specifically including the following steps: (1) Wheat grains were placed in superheated steam at 120°C for 3 minutes, and then crushed in a conventional blade mill at a blade speed of 8000 rpm for 6 minutes. At this time, the limit of the equipment was reached and the particle size D was obtained. 90 It is 500μm whole wheat flour.

[0029] (2) Add 5% by mass of β-glucan, 0.02% by mass of proanthocyanidins, 0.1% by mass of TG enzyme (initial enzyme activity 120 U / g), and 94.88% by mass of whole wheat flour to a powder mixer and mix for 5 min. Then add the powder mixture to a regular hammer mill, set the main shaft speed of the hammer mill to 10000 rpm and the grinding time to 2 h. At this time, the limit of the equipment is reached and the particle size D is obtained. 90 It is a blended whole wheat flour with a particle size of 80μm.

[0030] Example 4 The GI value and antioxidant activity of the fortified low-GI whole wheat flour obtained in Examples 1, 2, and 3, the whole wheat flour obtained in Comparative Examples 1 and 2, and the compound whole wheat flour obtained in Comparative Examples 3 and 4 were determined, and their processing adaptability for dough preparation was evaluated. The specific process is as follows: (1) GI value determination Add 1g of whole wheat flour to 5mL of PBS (pH 6.8) buffer, boil in a water bath for 5 min, then cool. The mixture is then subjected to simulated oral, gastric, and small intestinal digestion sequentially. Simulated oral digestion: Add 1mL of pancreatic α-amylase (50U / mL) to the boiled sample and react at 37℃ and 100 rpm for 10 min. Simulated gastric digestion: After oral digestion, add 3mL of simulated gastric digestion solution (7mL of HCl and 2g of NaCl added to distilled water and brought to a final volume of 1 L) and 4mL of pepsin (6000U / mL), adjust the pH to 2.5, and react at 37℃ and 100 rpm for 2 h. Simulated small intestinal digestion: After gastric digestion, the pH was adjusted to 7.0, and 4 mL of simulated intestinal fluid solution (54 mg / mL porcine bile salts, 218.7 mg / mL NaCl, 36.7 mg / mL CaCl2), 2 mL of trypsin (62.5 U / mL), and 0.2 mL of amylase (260 U / mL) were added. The reaction was carried out at 37℃ and 100 rpm for 2 h. During the simulated small intestinal digestion stage, samples were taken every 20 min, boiled in a water bath for 10 min to inactivate the enzymes, cooled, and centrifuged at 10000×g for 5 min. The supernatant was collected, and the glucose concentration in the digestive fluid was measured using a GOPOD method glucose assay kit. The starch hydrolysis rate was calculated using the following formula: Starch hydrolysis rate (%) = (glucose content in digestion solution × 0.9) / starch content in initial sample × 100 Then, the area under the hydrolysis curve is calculated by integration, and the hydrolysis index (HI) is calculated using glucose standard as a reference. HI = Area of ​​sample hydrolysis curve / Area of ​​glucose standard hydrolysis curve The formula for calculating the eGI value is as follows: eGI = 0.862HI + 8.198 The test results show that the GI values ​​of the fortified low-GI whole wheat flour obtained in Examples 1, 2, and 3 are 30, 22, and 16, respectively; the GI values ​​of the whole wheat flour obtained in Comparative Examples 1 and 2 are 70 and 65, respectively; and the GI values ​​of the compound whole wheat flour obtained in Comparative Examples 3 and 4 are 60 and 56, respectively. It can be seen that the GI value of whole wheat flour with added soluble polysaccharides, transglutaminase, and natural active substances is lower than that of whole wheat flour without these additives; and the GI value of fortified whole wheat flour obtained through multi-component co-milling is lower than that of compound whole wheat flour.

[0031] (2) Antioxidant activity assay Add 1g of whole wheat flour to 5mL of water, boil in a water bath for 5 minutes, cool, and dilute with distilled water 100 times before use.

[0032] Add 10 mL of potassium persulfate solution (2.45 mM) to 10 mL of ABTS solution (7 mM) to obtain ABTS stock solution, and incubate at room temperature in the dark for 12 h. Then dilute with ethanol to an absorbance of 0.70 ± 0.05 at 734 nm. Mix whole wheat flour sample solution or vitamin C (VC) standard solutions of different concentrations with the diluted ABTS solution, react at room temperature for 30 min, and then measure the absorbance at 734 nm. Calculate the free radical scavenging activity of the sample using the external standard method, and the results are expressed as mg VC / g whole wheat flour.

[0033] The test results show that the free radical scavenging activities of the fortified low-GI whole wheat flour obtained in Examples 1, 2, and 3 were 2 mg VC / g, 2.4 mg VC / g, and 2.8 mg VC / g, respectively. The free radical scavenging activities of the whole wheat flour obtained in Comparative Examples 1 and 2 were 0.7 and 0.4, respectively. The free radical scavenging activities of the compound whole wheat flour obtained in Comparative Examples 3 and 4 were 1.5 and 1.2, respectively. It can be seen that the free radical scavenging activity of whole wheat flour with added natural active substances is higher than that of whole wheat flour without added substances; the free radical scavenging activity of fortified whole wheat flour obtained through multi-component co-grinding is higher than that of compound whole wheat flour; and the free radical scavenging activity of whole wheat flour ground at low temperatures is higher than that of ordinary ground whole wheat flour.

[0034] (3) Texture properties of the dough Whole wheat flour and water were mixed in a 30:70 ratio by mass, added to a dough mixer, and stirred until flocculent. The mixture was then poured out and kneaded into a dough. The dough was analyzed using a texture analyzer. The analyzer parameters were set as follows: probe model P / 0.5R, probe speed before, during, and after measurement all set to 1 mm / s, sample compression 10 mm, and trigger force 1 g. The dough's hardness, viscosity, elasticity, cohesiveness, and adhesiveness were measured. The results are shown in Table 1.

[0035] Table 1. Texture properties of dough It can be seen that the dough made from the fortified low-GI whole wheat flour obtained in Examples 1, 2, and 3 has lower hardness and higher viscosity, elasticity, cohesion, and adhesiveness, indicating that the processing characteristics of the fortified low-GI whole wheat flour produced by the present invention and the sensory quality of its processed products are better than those of ordinary whole wheat flour.

[0036] The embodiments of this application have been described above with reference to the accompanying drawings. Specific examples have been used to illustrate the principles and implementation methods of this application. The description of the above embodiments is only for the purpose of helping to understand the core ideas of this application. However, this application is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of this application without departing from the spirit and scope of the claims, and all of these forms are within the protection scope of this application.

Claims

1. A method for preparing a nutritionally fortified low-GI whole wheat flour, characterized in that, Includes the following steps: Wheat grains are inactivated by superheated steam and then ultra-finely pulverized using a low-temperature impact mill to obtain whole wheat flour. The whole wheat flour, soluble polysaccharide, transglutaminase and natural active substances are mixed evenly to obtain a mixture, which is then ground using a low-temperature media mill to obtain the nutritionally fortified low-GI whole wheat flour.

2. The preparation method according to claim 1, characterized in that, The temperature of the superheated steam is 110℃-120℃, and the inactivation treatment time is 1min-5min.

3. The preparation method according to claim 1, characterized in that, The temperature used for ultrafine grinding with a low-temperature impact mill is 10℃-20℃. The particle size D of the whole wheat flour 90 ≤80μm.

4. The preparation method according to claim 1, characterized in that, The soluble polysaccharides include at least one of pectin, β-glucan, gum arabic, xanthan gum, soluble soybean polysaccharide, tremella polysaccharide, shiitake mushroom polysaccharide, and wolfberry polysaccharide.

5. The preparation method according to claim 4, characterized in that, The amount of the soluble polysaccharide used is 3%-8% of the mass of the mixture.

6. The preparation method according to claim 1, characterized in that, The natural active substances include at least one of anthocyanins, carotenoids, betaine, and chlorophyll.

7. The preparation method according to claim 6, characterized in that, The amount of the natural active substance used is 0.01%-1% of the mass of the mixture.

8. The preparation method according to claim 1, characterized in that, The initial enzyme activity of the transglutaminase is 100-130 U / g, and the amount of transglutaminase used is 0.02%-0.3% of the mass of the mixture; the amount of whole wheat flour used is 90.7%-96.97% of the mass of the mixture.

9. A nutritionally fortified low-GI whole wheat flour, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.

10. The nutritionally fortified low-GI whole wheat flour according to claim 9, characterized in that, The particle size D of the fortified low-GI whole wheat flour 90 ≤10μm.

Images