Anti-aging whole corn flour with high carotenoid retention rate and preparation method thereof

Abstract

The invention discloses an anti-aging corn powder with high carotenoid retention rate and a preparation method thereof, the preparation method comprising cleaning, threshing, blanching, beating, obtaining corn powder; gelatinization, obtaining corn paste material; adding enzyme for enzymolysis, enzyme inactivation, obtaining corn enzymolysis powder; preparing pectin-chitosan composite electrolyte gel; then mixing corn enzymolysis powder, pectin-chitosan composite electrolyte gel and sodium caseinate, after grinding, dispersion and emulsification, spray drying, and obtaining a finished product. The above-mentioned preparation method combines the spray drying microencapsulation of electrolyte gel and the spiral composite technology of straight-chain starch molecular fragments and emulsifiers to achieve the anti-aging goal of corn powder; through the spray drying process, pectin-chitosan composite electrolyte gel microencapsulation, to achieve the microencapsulation of corn carotenoids. The obtained corn powder has the advantages of high carotene retention rate, high gelatinization degree and good anti-aging effect.

Description

Technical Field

[0001] The invention relates to the technical field of preparation of whole corn flour, in particular to anti-aging whole corn flour with high carotenoid retention rate and a preparation method thereof. Background Art

[0002] Corn is one of the main food crops in my country. As a whole grain food, corn is rich in nutrition, containing starch, protein, amino acids, fat, soluble sugar, dietary fiber, and a variety of vitamins and minerals. It is known as the "golden grain". According to the difference in taste and texture, corn is divided into ordinary corn, glutinous corn, and sweet corn. Among them, ordinary corn has the largest planting area and the highest yield, and is also the most widely used food industry raw material.

[0003] Common corn contains abundant starch, which can reach more than 70% of the dry weight of corn, and is a good raw material for starchy foods. In addition, common corn also contains abundant carotenoids, especially high content of zeaxanthin and lutein, which play a unique role in protecting eyesight. Studies have shown that the macular pigment of the human retina is composed of zeaxanthin and lutein, which have the function of absorbing near-ultraviolet blue light that is most damaging to the retina macula. Therefore, zeaxanthin and lutein play an important role in reducing the occurrence of serious eye diseases such as macular degeneration and cataracts associated with aging. Medical studies have shown that regular consumption of natural foods rich in zeaxanthin and lutein can significantly reduce the risk of age-related macular degeneration and effectively protect eyesight.

[0004] Processing ordinary corn into pre-cooked whole corn flour is a whole-grain convenience food that is popular with consumers. However, the whole corn flour obtained by conventional steaming, cooking, hot air drying and then grinding is prone to starch aging during storage. At the same time, the carotenoids in corn are easily degraded during the thermal processing process, and the carotenoid retention rate in the obtained whole corn flour is low, resulting in reduced nutritional and sensory quality and digestibility of the whole corn flour. Summary of the invention

[0005] In order to overcome the shortcomings of the prior art, one of the purposes of the present invention is to provide a method for preparing anti-aging whole corn flour with a high carotenoid retention rate. The whole corn flour prepared by the preparation method is not prone to starch aging, and the carotenoid retention rate in the whole corn flour is high, so that the nutritional and sensory quality and digestibility of the whole corn flour are good; the second purpose of the present invention is to provide an anti-aging whole corn flour with a high carotenoid retention rate. The whole corn flour can be directly prepared and eaten, and can also be used as the main ingredient of other nutritional paste powders, baked products, pastries and cold drinks.

[0006] One of the purposes of the present invention is achieved by the following technical solution:

[0007] A method for preparing anti-aging whole corn flour with high carotenoid retention rate comprises the following steps:

[0008] 1) taking fresh and ripe corn, removing the husk and washing it, threshing it to obtain corn kernels, and blanching the corn kernels;

[0009] 2) mixing the corn kernels blanched in step 1) with water to obtain corn whole pulp; then gelatinizing the corn whole pulp to obtain corn paste material; lowering the temperature of the corn paste material, adding food α-amylase and maltogenic amylase under heat preservation conditions to perform enzymatic hydrolysis; after completion, heating to perform enzyme inactivation treatment to obtain corn enzymatic whole pulp;

[0010] 3) Preparation of pectin-chitosan composite electrolyte gel: pectin and chitosan with a high degree of deacetylation are respectively prepared into solutions; the pectin solution and the chitosan solution are evenly mixed, and allowed to stand to fully swell, and the anionic polysaccharide properties of pectin polysaccharide and the cationic polysaccharide properties of chitosan are utilized to allow the pectin anions and chitosan cations to fully react to form an electrolyte composite gel, that is, to obtain a pectin-chitosan composite electrolyte gel;

[0011] 4) Compounding and homogenizing raw and auxiliary materials: adding sodium caseinate and the pectin-chitosan composite electrolyte gel obtained in step 3) to the corn enzymatic hydrolyzed whole slurry obtained in step 2), grinding with a colloid mill, and further dispersing and emulsifying to obtain a mixture;

[0012] 5) spray drying: preheating the mixture obtained in step 4) and then spray drying. In this process, the pectin-chitosan composite electrolyte gel is microencapsulated, and the moderately degraded corn starch molecules are fixed by the microencapsulation. On the other hand, the microencapsulation of corn carotenoids is achieved to improve their stability. At the same time, the moderately degraded corn amylose molecules form a spiral complex with the emulsifier sodium caseinate, and the crystallization degree of the starch molecules is reduced from the two aspects of microencapsulation and the formation of the spiral complex, so that the purpose of delaying the aging of starch and reducing the aging degree can be achieved, and the anti-aging whole corn flour with a high carotenoid retention rate is obtained.

[0013] Furthermore, in step 1), the corn kernels are placed in a superheated steam baking microwave oven and blanched with superheated steam at 110°C to 130°C for 60 to 90 seconds to quickly inactivate the biological enzyme activity of the corn kernels, inhibit the browning of the corn enzyme and the degradation of nutrients, so as to maintain the good color and nutritional quality of the product.

[0014] Furthermore, in step 2), the corn kernels blanched in step 1) are mixed with water in a mass ratio of 1:(2-3) to obtain corn whole pulp.

[0015] Further, in step 2), the whole corn slurry is put into a sandwich pot, the stirrer is turned on, and superheated steam at 120-140° C. is introduced while stirring to perform gelatinization treatment for 3-5 minutes, so that the gelatinization degree of the corn starch reaches more than 90%; then the temperature of the sandwich pot is adjusted to reduce the temperature of the corn paste material to 55-60° C., and food α-amylase and maltogenic amylase are added under insulation conditions.

[0016] Furthermore, in step 2), 10 to 15 U / g of α-amylase is added based on the mass of total solids in the whole corn syrup; and 15 to 20 U / g of maltogenic amylase is added based on the mass of total solids in the whole corn syrup.

[0017] Furthermore, in step 2), food α-amylase and maltogenic amylase are added for enzymatic hydrolysis for 20 to 40 minutes, and after completion, the temperature is raised to 80 to 90° C. and the enzyme is inactivated for 1 to 2 minutes to obtain corn enzymatic hydrolyzed whole slurry.

[0018] Furthermore, in step 3), the pectin solution is a pectin aqueous solution with a mass concentration of 1 to 2%; the chitosan solution is a chitosan aqueous solution with a mass concentration of 1 to 2%, the chitosan aqueous solution also contains citric acid with a mass concentration of 1 to 2%, and the chitosan used is a high-deacetylation chitosan with a deacetylation degree of more than 85%; the pectin solution and the chitosan solution are mixed uniformly in a mass ratio of (9 to 11): 1, and allowed to stand for 12 to 24 hours to allow them to fully swell to form an electrolyte composite gel, thereby obtaining a pectin-chitosan composite electrolyte gel.

[0019] Furthermore, in step 4), the amount of sodium caseinate added is 0.5-1% of the total solids in the corn enzymatic hydrolyzed whole pulp; the amount of pectin-chitosan composite electrolyte gel added is 1-2% of the total solids in the corn enzymatic hydrolyzed whole pulp.

[0020] Furthermore, in step 5), the spray drying conditions are: inlet air temperature 150-180°C, feed rate 2.0-2.5 L / h, hot air flow rate 25-30 m 3 / h, the air outlet temperature is 70~90℃.

[0021] The second object of the present invention is achieved by adopting the following technical solution:

[0022] The invention discloses an anti-aging whole corn flour with a high carotenoid retention rate, which is prepared by the preparation method of the anti-aging whole corn flour with a high carotenoid retention rate.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] (1) The method for preparing an anti-aging whole corn flour with a high carotenoid retention rate of the present invention comprises the following steps: using bio-enzyme technology to moderately degrade corn starch, supplemented by a natural food emulsifier that can delay corn starch aging and reduce corn starch aging, and using spray drying microencapsulation technology, so that on the one hand, the moderately degraded corn starch molecules can be immobilized, and on the other hand, the corn carotenoids can be embedded in microcapsules, thereby improving the stability of the carotenoids; and the moderately degraded corn amylose molecules form a spiral complex with the natural emulsifier, thereby preparing the anti-aging whole corn flour with a high carotenoid retention rate.

[0025] (2) The preparation method of whole corn flour of the present invention comprises washing, threshing, blanching, beating to obtain whole corn pulp; gelatinization to obtain corn paste material; adding enzymes for enzymolysis and enzyme inactivation to obtain whole corn enzymatic pulp; preparing pectin-chitosan composite electrolyte gel; then mixing whole corn enzymatic pulp, pectin-chitosan composite electrolyte gel and sodium caseinate, grinding, dispersing and emulsifying, and then spray drying to obtain a finished product. The above preparation method combines the spray drying microencapsulation of electrolyte gel and the spiral composite technology of amylose molecular fragments and emulsifiers to achieve the goal of anti-aging of whole corn flour; during the spray drying process, the pectin-chitosan composite electrolyte gel is microencapsulated to achieve microencapsulation of carotenoids in corn, thereby improving the stability of carotenoids and effectively maintaining the nutritional and sensory quality of whole corn flour. Compared with the conventional whole corn flour obtained by grinding after steaming, cooking and hot air drying, the whole corn flour prepared by the method of the present invention can better avoid the starch aging problem during storage, and can be sealed and stored in a cool and dry place for 12 months while still maintaining a high gelatinization degree and a low aging degree.

[0026] (3) Ordinary corn has the highest starch content, reaching more than 70% of the dry weight of corn. Among the starch, amylose accounts for 22% to 28% and amylopectin accounts for about 75%. Due to the higher content of amylopectin, it is more important to inhibit the aging of amylopectin during storage. Therefore, the present invention selects maltogenic amylase, which mainly hydrolyzes the α-1,4-glucosidic bonds on the amylopectin chain, as the enzyme for moderate degradation of starch molecules, and uses α-amylase in combination with it to further improve the efficiency of moderate enzymatic hydrolysis of corn starch. The present invention gives full play to the enzymatic hydrolysis characteristics of α-amylase and maltogenic amylase, and uses α-amylase to hydrolyze the α-1,4-glucosidic bonds inside the starch molecules to expose more starch molecule ends. On this basis, maltogenic amylase hydrolyzes the starch molecule ends, further hydrolyzing the starch molecules into maltose, oligosaccharides and small molecular dextrins, shortening the length of amylose chains and the length of amylopectin outer chains, effectively delaying the recrystallization of amylose and amylopectin molecules, thereby inhibiting the aging of corn starch.

[0027] (4) The pectin-chitosan composite electrolyte gel of the present invention utilizes the anionic polysaccharide properties of pectin and the cationic polysaccharide properties of chitosan, and selects chitosan with a high deacetylation degree of more than 85%. The higher the deacetylation degree, the more cationic charged groups are generated by the protonation of chitosan amino groups. The pectin anions and chitosan cations fully interact to form a composite electrolyte gel. During the spray drying process, the pectin-chitosan composite electrolyte gel is microencapsulated. At the same time, the polyelectrolyte interaction between pectin and chitosan can enhance the mechanical properties of the microcapsules, making the formed microcapsules stronger and denser, and fixing the moderately degraded corn starch molecules, preventing the starch molecules from forming crystals during storage, and inhibiting the aging of corn starch. At the same time, during the microencapsulation process of the pectin-chitosan composite electrolyte gel, the embedding of corn carotenoids is also achieved, the stability of corn carotenoids is improved, and thus the retention rate of carotenoids in whole corn flour is improved.

[0028] (5) The corn flour of the present invention is added with a natural emulsifier, sodium caseinate. During the spray drying process, sodium caseinate can form a helical complex with the moderately degraded corn amylose molecular fragments, further preventing the starch molecules from forming crystals and inhibiting the aging of corn starch.

[0029] (6) In the preparation process of anti-aging corn flour, superheated steam blanching and superheated steam gelatinization technology were used. Compared with the traditional hot water blanching and steaming gelatinization technology, the blanching and gelatinization time was shortened and the loss of nutrients was reduced.

[0030] (7) The raw materials used in the whole corn flour of the present invention are all of natural origin. Sodium caseinate comes from animal dairy products, pectin comes from fruit and vegetable plants, and chitosan comes from the shells of marine organisms. No chemically synthesized additives are used, thereby maintaining the all-natural food properties of the anti-aging whole corn flour with a high carotenoid retention rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The bar graphs of gelatinization degree of whole corn flour prepared by different methods before and after storage are shown;

[0032] Figure 2 The bar graphs of aging degree of whole corn flour prepared by different methods before and after storage are shown;

[0033] Figure 3 The bar graph shows the carotenoid retention rate of whole corn flour prepared by different methods;

[0034] Figure 4 The bar graph shows the zeaxanthin retention rate of whole corn flour prepared by different methods;

[0035] Figure 5 Bar graph showing lutein retention rate of whole corn flour prepared by different methods.

[0036] Note: Figure 1 to Figure 5 The whole corn flour prepared by the present invention is obtained in Example 1. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods. It should be noted that, under the premise of no conflict, the various embodiments or technical features described below can be arbitrarily combined to form a new embodiment.

[0038] Example 1

[0039] A method for preparing anti-aging whole corn flour with high carotenoid retention rate comprises the following steps:

[0040] 1) Preparation of corn enzymatic hydrolysis whole pulp: fresh and mature corn is taken, the husk is removed and then washed with running water, and the corn kernels are threshed by a thresher to obtain corn kernels, and the corn kernels are placed in a superheated steam baking microwave oven and blanched with superheated steam at 110°C for 90s to quickly inactivate the biological enzyme activity of the corn kernels, inhibit the browning of corn enzymes and the degradation of nutrients, so as to maintain the good color and nutritional quality of the product; after completion, pure water is added according to the mass ratio of corn kernels to water of 1:2, and the corn kernels are put into a pulping machine for pulping until a uniform pulp is obtained to obtain corn whole pulp; then the corn whole pulp is added to the mixture and the mixture is put into a pulping machine for pulping until a uniform pulp is obtained. The slurry was put into a sandwich pot, the stirrer was turned on, and superheated steam at 125°C was introduced while stirring for gelatinization treatment for 5 minutes, so that the gelatinization degree of corn starch reached more than 90% in a short time; then the temperature of the sandwich pot was adjusted to reduce the temperature of the corn paste material to 55°C. While maintaining this temperature, food α-amylase and maltogenic amylase were added in an amount of 10U / g corn whole slurry total solids and 20U / g corn whole slurry total solids, respectively, and the enzymatic hydrolysis was carried out for 20 minutes. After completion, the temperature was raised to 90°C for enzyme inactivation treatment for 1 minute to obtain corn enzymatic whole slurry.

[0041] 2) Preparation of pectin-chitosan composite electrolyte gel: pectin and highly deacetylated chitosan are prepared into solutions respectively: pectin is prepared into an aqueous solution with a mass concentration of 1%; chitosan is first dissolved in citric acid with a mass concentration of 1%, and then a chitosan solution with a mass concentration of 1% is prepared, the pectin solution and the chitosan solution are uniformly mixed at a mass ratio of 10:1, and allowed to stand for 24 hours to fully swell, and the anionic polysaccharide properties of pectin polysaccharide and the cationic polysaccharide properties of chitosan are utilized to allow the pectin anions and chitosan cations to fully react to form an electrolyte composite gel, that is, a pectin-chitosan composite electrolyte gel is obtained.

[0042] 3) Compounding and homogenizing of raw materials and auxiliary materials: Sodium caseinate and pectin-chitosan composite electrolyte gel are added to the corn enzymatic hydrolyzed whole pulp, and after grinding with a colloid mill, the mixture is further dispersed and emulsified by a homogenizer to obtain a uniform and fine mixture slurry. Among them, the addition amount of sodium caseinate is 1.0%, and the addition amount of pectin-chitosan composite gel is 1.5% (based on the total solids in the composite gel), and the chitosan used is a high deacetylation chitosan with a deacetylation degree of more than 85%; the addition amounts of the above ingredients are all calculated as a percentage of the total solids in the corn enzymatic hydrolyzed whole pulp.

[0043] 4) Spray drying: preheat the uniform and fine mixture slurry obtained in step 3) and spray dry it to obtain anti-aging corn flour with high carotenoid retention rate. The spray drying conditions are: inlet air temperature 180°C, feed rate 2.2L / h, hot air flow rate 26m 3 / h, the air outlet temperature is 85℃.

[0044] Example 2

[0045] A method for preparing anti-aging whole corn flour with high carotenoid retention rate comprises the following steps:

[0046] 1) Preparation of corn enzymatic hydrolysis whole pulp: fresh and mature corn is taken, the husk is removed and then washed with running water, and the corn kernels are threshed by a thresher to obtain corn kernels, and the corn kernels are placed in a superheated steam baking microwave oven and blanched with superheated steam at 120°C for 80 seconds to quickly passivate the biological enzyme activity of the corn kernels, inhibit the browning of corn enzymes and the degradation of nutrients, so as to maintain the good color and nutritional quality of the product; after completion, pure water is added according to the mass ratio of corn kernels to water of 1:2, and the corn kernels are put into a pulping machine for pulping until a uniform pulp is formed to obtain corn whole pulp; then Put the whole corn slurry into a sandwich pot, turn on the stirrer, and introduce 130°C superheated steam while stirring for 4 minutes to carry out gelatinization treatment, so that the gelatinization degree of corn starch reaches more than 90% in a short time; then adjust the temperature of the sandwich pot to reduce the temperature of the corn paste material to 55°C, and while maintaining this temperature, add food α-amylase and maltogenic amylase in an amount of 15U / g and 15U / g of total solids of the whole corn slurry, respectively, and carry out enzymatic hydrolysis for 30 minutes. After completion, raise the temperature to 80°C and inactivate the enzyme for 2 minutes to obtain corn enzymatic whole slurry.

[0047] 2) Preparation of pectin-chitosan composite electrolyte gel: pectin and highly deacetylated chitosan are prepared into solutions respectively: pectin is prepared into a 1% aqueous solution, and chitosan is dissolved in 1% citric acid to prepare a 1% chitosan solution; the pectin solution and the chitosan solution are uniformly mixed at a mass ratio of 10:1, and allowed to stand for 24 hours to fully swell, and the anionic polysaccharide properties of pectin polysaccharide and the cationic polysaccharide properties of chitosan are utilized to allow the pectin anions and chitosan cations to fully react to form an electrolyte composite gel, thus obtaining a pectin-chitosan composite electrolyte gel.

[0048] 3) Compounding and homogenizing of raw materials and auxiliary materials: Sodium caseinate and pectin-chitosan composite electrolyte gel are added to the whole corn enzymatic hydrolyzed pulp, and after grinding with a colloid mill, the mixture is further dispersed and emulsified by a homogenizer to obtain a uniform and fine mixture slurry. The amount of sodium caseinate added is 0.8%, and the amount of pectin-chitosan composite gel added is 1.2% (based on the total solids in the composite gel). The chitosan used is a high deacetylation chitosan with a deacetylation degree of more than 85%; the addition amounts of the above ingredients are all calculated as a percentage of the total solids in the whole corn enzymatic hydrolyzed pulp.

[0049] 4) Spray drying: preheat the uniform and fine mixture slurry obtained in step 3) and spray dry it to obtain anti-aging corn flour with high carotenoid retention rate. The spray drying conditions are: inlet air temperature 160°C, feed rate 2.5L / h, hot air flow rate 25m 3 / h, the air outlet temperature is 75℃.

[0050] Example 3

[0051] A method for preparing anti-aging whole corn flour with high carotenoid retention rate comprises the following steps:

[0052] 1) Preparation of corn enzymatic hydrolysis whole pulp: fresh and mature corn is taken, the husk is removed and then washed with running water, and the corn kernels are threshed by a thresher to obtain corn kernels, and the corn kernels are placed in a superheated steam baking microwave oven and blanched with superheated steam at 130°C for 60s to quickly passivate the biological enzyme activity of the corn kernels, inhibit the browning of corn enzymes and the degradation of nutrients, so as to maintain the good color and nutritional quality of the product; after completion, pure water is added according to the mass ratio of corn kernels to water of 1:2, and the corn kernels are put into a pulping machine for pulping until a uniform pulp is formed to obtain corn whole pulp; then Put the whole corn slurry into a sandwich pot, turn on the stirrer, and introduce 140°C superheated steam while stirring for gelatinization for 3 minutes, so that the gelatinization degree of corn starch reaches more than 90% in a short time; then adjust the temperature of the sandwich pot to reduce the temperature of the corn paste material to 55°C, and while maintaining this temperature, add food α-amylase and maltogenic amylase at an amount of 20U / g and 10U / g of total solids of the whole corn slurry, respectively, and carry out enzymatic hydrolysis for 40 minutes. After completion, raise the temperature to 85°C and inactivate the enzyme for 2 minutes to obtain corn enzymatic whole slurry.

[0053] 2) Preparation of pectin-chitosan composite electrolyte gel: pectin and highly deacetylated chitosan are prepared into solutions respectively: pectin is prepared into a 1% aqueous solution, and chitosan is dissolved in 1% citric acid to prepare a 1% chitosan solution; the pectin solution and the chitosan solution are uniformly mixed at a mass ratio of 10:1, and allowed to stand for 24 hours to fully swell, and the anionic polysaccharide properties of pectin polysaccharide and the cationic polysaccharide properties of chitosan are utilized to allow the pectin anions and chitosan cations to fully react to form an electrolyte composite gel, thus obtaining a pectin-chitosan composite electrolyte gel.

[0054] 3) Compounding and homogenizing of raw materials and auxiliary materials: Sodium caseinate and pectin-chitosan composite electrolyte gel are added to the corn enzymatic hydrolyzed whole pulp, and after grinding with a colloid mill, the mixture is further dispersed and emulsified by a homogenizer to obtain a uniform and fine mixture slurry. The amount of sodium caseinate added is 0.6%, and the amount of pectin-chitosan composite gel added is 1.8% (based on the total solids in the composite gel). The chitosan used is a high deacetylation chitosan with a deacetylation degree of more than 85%; the addition amount is calculated as a percentage of the total solids in the corn enzymatic hydrolyzed whole pulp.

[0055] 4) Spray drying: The uniform and fine mixture slurry obtained in step 3) is preheated and then spray dried to obtain anti-aging whole corn flour with high carotenoid retention rate. The spray drying conditions are: inlet air temperature 170°C, feed rate 2.3L / h, hot air flow rate 30m 3 / h, the air outlet temperature is 90℃.

[0056] In order to investigate the effectiveness of the method for inhibiting the aging of whole corn flour starch adopted by the present invention, the following control group was set up during the study to prepare whole corn flour, and other operations were consistent with Example 1:

[0057] ① Directly spray-drying the obtained corn whole syrup without enzymatic treatment, without adding sodium caseinate, and without adding pectin-chitosan electrolyte composite gel;

[0058] ② The obtained corn enzymatic hydrolyzed whole slurry is spray-dried without adding sodium caseinate or pectin-chitosan electrolyte composite gel;

[0059] ③ Sodium caseinate is added to the obtained corn enzymatic hydrolyzed whole pulp according to the ingredient ratio, but pectin-chitosan electrolyte composite gel is not added;

[0060] ④ Sodium caseinate and chitosan gel with a high degree of deacetylation are added to the obtained corn enzymatic hydrolyzed whole pulp according to the ingredient ratio, without pectin.

[0061] ⑤ Add sodium caseinate and pectin gel according to the proportion of ingredients to the obtained corn enzymatic hydrolyzed whole pulp, and chitosan without high deacetylation degree.

[0062] Conventional preparation method: The corn is steamed, cooked, hot-air dried and then ground to obtain conventionally prepared whole corn flour.

[0063] The whole corn flour prepared by the above control group, conventional method and the method of the present invention was sealed and stored in a cool and dry place for 12 months, and the gelatinization degree and aging degree were measured when they were prepared (i.e., the storage time was 0) and after 12 months of storage. The gelatinization degree measurement results are shown in Figure 1 , aging test results are shown in Figure 2 .

[0064] Figure 1 The degree of gelatinization is determined according to the method in Appendix B of GB / T 31323 "Instant Rice"; Figure 2 The degree of aging was determined by centrifugation. Three replicates were set for each sample and the results were calculated as the average. SPSS20 software was used to analyze the differences in the results of gelatinization and aging. Different lowercase letters in the figure indicate significant differences (P < 0.05).

[0065] Depend on Figure 1 and Figure 2 It can be seen that when prepared, the whole corn flour of each control group, the conventional method and Example 1 all had a very high gelatinization degree and a very low aging degree, and the results were similar, and there was no significant difference between the gelatinization degrees and the aging degrees; but after 12 months of storage, there were significant differences between the control groups and between the control groups and the present invention, and the whole corn flour of Example 1 maintained the highest gelatinization degree and the lowest aging degree.

[0066] After 12 months of storage, Figure 1 It can be seen that the gelatinization degree of corn flour prepared by the conventional method decreased from 94.19% to 63.31%, a decrease of more than 30%. Figure 2 It can be seen that its aging degree increased from 2.75% to 53.18%, and the aging degree increased by more than 50%; Figure 1 and Figure 2 The results show that the whole corn flour prepared by the present invention can reach a gelatinization degree of more than 90% and an aging degree of 11.63% after storage for 12 months. Compared with the whole corn flour obtained by conventional steaming, cooking, hot air drying and grinding, the present invention has a very significant effect in inhibiting the aging of the whole corn flour.

[0067] Figure 1 and Figure 2 The results showed that after 12 months of storage, among the five control groups ① to ⑤, control group ① had the lowest gelatinization degree and the highest aging degree. The control group ② treated with enzymatic hydrolysis had a significantly higher gelatinization degree than control group ① and a significantly lower aging degree than control group ①. The control group ③, to which sodium caseinate was added on the basis of control group ②, had a significantly higher gelatinization degree and a significantly lower aging degree than control group ②. The control groups ④ and ⑤, to which chitosan gel with a high degree of deacetylation and pectin gel were added on the basis of control group ③, had a significantly higher gelatinization degree than control group ③ and a significantly lower aging degree than control group ③. The effect of control group ⑤ was significantly better than that of control group ④. Due to the restriction on the amount of chitosan added in the national standard (GB2760-2014 "National Food Safety Standard for the Use of Food Additives"), according to the ingredient ratio of the present invention, the amount of chitosan gel with a high degree of deacetylation added in control group ④ was 1 / 10 of the amount of pectin gel added in control group ⑤. Therefore, this may be the reason why the anti-aging effect of control group ④ is weaker than that of control group ⑤. Compared with control groups ④ and ⑤, Example 1 uses pectin-chitosan electrolyte composite gel with high deacetylation degree, and its gelatinization degree is significantly improved and the aging degree is significantly reduced.

[0068] In addition, in order to investigate the effectiveness of the preparation method used in the present invention in improving the retention rate of corn carotenoids, the retention rates of total carotenoids, zeaxanthin and lutein in each group of samples were simultaneously measured during the study. The measurement results are shown in Figure 3 to Figure 5. The content determination and retention rate calculation methods are as follows: (1) The total carotenoid content was determined by UV-visible spectrophotometry using β-carotene as the working curve, and the total carotenoid content was calculated as the amount equivalent to β-carotene; (2) The zeaxanthin and lutein contents were determined by HPLC; (3) Total carotenoid retention rate = (total carotenoid content in the prepared sample / total carotenoid content in corn before preparation) × 100%, zeaxanthin retention rate = (zeaxanthin content in the prepared sample / zeaxanthin content in corn before preparation) × 100%, lutein retention rate = (lutein content in the prepared sample / lutein content in corn before preparation) × 100%. Three replicates were set for each sample determination, and the results were calculated as the average value. SPSS20 software was used to analyze the significance of the results of total carotenoid retention rate, zeaxanthin retention rate and lutein retention rate, and different lowercase letters indicate significant differences (P < 0.05).

[0069] Figure 2 to Figure 5 The measurement results show that the total carotenoid, zeaxanthin and lutein retention rates of the whole corn flour prepared in Example 1 are the highest when prepared and after 12 months of storage, which are significantly higher than the whole corn flour prepared by the conventional method and each control group. When prepared, the total carotenoid, zeaxanthin and lutein retention rates of the whole corn flour prepared in Example 1 can reach more than 85%, and after 12 months of storage, the retention rate is still more than 80%, indicating that the present invention can not only effectively protect corn carotenoids during processing, but also has a good protection effect during storage.

[0070] Among the five control groups, control group ① to control group ⑤, control group ①, which only used the spray drying method, had the lowest retention rates of total carotenoids, zeaxanthin, and lutein when prepared and after storage for 12 months, which were significantly lower than those of the other groups. The retention rates of control group ②, which was treated with enzymatic hydrolysis, were significantly higher than those of control group ①. This may be because the enzymatic hydrolysis promoted the release of corn carotenoids wrapped in starch macromolecules, and the carotenoid content in the product increased, and the retention rate increased accordingly. Control group ③, which added sodium caseinate to control group ②, showed that sodium caseinate could form a helical complex with the moderately degraded corn amylose molecular fragments during the spray drying process, which could prevent starch molecules from crystallizing and inhibit corn starch aging on the one hand, and also play a proper encapsulation role on corn carotenoids and improve their stability on the other hand. The retention rates of xanthophyll and lutein showed an increasing trend; the control groups ④ and ⑤, which respectively added high deacetylation chitosan gel and pectin gel to the control group ③, showed an upward trend in the retention rates of total carotenoids, zeaxanthin and lutein relative to the control group ③, because the gel formed microcapsules for corn carotenoids during the spray drying process, thereby improving their stability; and the effect of the control group ⑤ was significantly better than that of the control group ④, which may be due to the fact that the amount of pectin gel added to the control group ⑤ was 10 times the amount of chitosan gel with high deacetylation in the control group ④ (limited by the restriction on the amount of chitosan added in the national standard (GB2760-2014 "National Food Safety Standard for the Use of Food Additives"), according to the ratio of ingredients of the present invention, the amount of chitosan gel with high deacetylation in the control group ④ was 1 / 10 of the amount of pectin gel added to the control group ⑤). It can be seen that each preparation process adopted in Example 1 can effectively improve the retention rates of corn carotenoids and their zeaxanthin and lutein. The present invention adopts pectin-chitosan electrolyte composite gel with high deacetylation degree, which has the best microcapsule embedding effect on corn carotenoids and the highest retention rate during the spray drying process.

[0071] In summary, compared with the conventional whole corn flour obtained by steaming, cooking, hot air drying and grinding, the present invention has a very significant effect on inhibiting the aging of whole corn flour, and the retention rate of corn carotenoids is higher; the enzymatic hydrolysis preparation process adopted by the present invention and the addition and configuration of various auxiliary materials can effectively promote the reduction of the aging degree of whole corn flour and the improvement of the retention rate of corn carotenoids. The present invention combines the above methods to improve the retention rate of corn carotenoids and the effect of resisting corn starch aging.

[0072] The anti-aging whole corn flour with high carotenoid retention rate prepared by the method of the present invention maintains good sensory quality and digestibility and absorption, can be directly dissolved and eaten, and can also be used as an ingredient in baked foods such as bread and cakes, beverages or other foods.

[0073] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A method for preparing anti-aging whole corn flour with high carotenoid retention rate, characterized in that: The following steps are involved: 1) taking fresh and ripe corn, removing the husk and washing it, threshing it to obtain corn kernels, and blanching the corn kernels; 2) mixing the corn kernels blanched in step 1) with water and beating the mixture to obtain corn pulp; Then, the whole corn pulp is gelatinized to obtain corn pulp material; the temperature of the corn pulp material is lowered, and α-amylase and maltogenic amylase are added under heat preservation conditions to perform enzymatic hydrolysis treatment; after completion, the temperature is raised to perform enzyme inactivation treatment to obtain corn enzymatic hydrolysis whole pulp; 3) Preparation of pectin-chitosan composite electrolyte gel: pectin and chitosan with a high degree of deacetylation are prepared into solutions respectively; then the pectin solution and the chitosan solution are evenly mixed and allowed to stand to fully swell to form an electrolyte composite gel, that is, a pectin-chitosan composite electrolyte gel is obtained; 4) Compounding and homogenizing raw and auxiliary materials: adding sodium caseinate and the pectin-chitosan composite electrolyte gel obtained in step 3) to the corn enzymatic hydrolyzed whole slurry obtained in step 2), grinding with a colloid mill, and further dispersing and emulsifying to obtain a mixture; 5) Spray drying: preheating the mixture obtained in step 4) and then spray drying it to obtain the anti-aging whole corn flour with high carotenoid retention rate.

2. The method for preparing anti-aging whole corn flour with high carotenoid retention rate according to claim 1, characterized in that: In step 1), the corn kernels are placed in a superheated steam baking microwave oven and blanched with superheated steam at 110° C. to 130° C. for 60 to 90 seconds.

3. The method for preparing anti-aging whole corn flour with high carotenoid retention rate as claimed in claim 1, characterized in that: In step 2), the corn kernels blanched in step 1) are mixed with water in a mass ratio of 1:(2-3) to obtain corn whole pulp.

4. The method for preparing anti-aging whole corn flour with high carotenoid retention rate according to claim 1, characterized in that: In step 2), the whole corn slurry is put into a sandwich pot, the stirrer is turned on, and superheated steam at 120-140° C. is introduced while stirring to perform gelatinization treatment for 3-5 minutes, so that the gelatinization degree of the corn starch reaches more than 90%; then the temperature of the sandwich pot is adjusted to reduce the temperature of the corn paste material to 55-60° C., and α-amylase and maltogenic amylase are added under heat preservation conditions.

5. The method for preparing anti-aging whole corn flour with high carotenoid retention rate as claimed in claim 1, characterized in that: In step 2), 10 to 15 U / g of α-amylase is added according to the mass of the total solids of the whole corn syrup; and 15 to 20 U / g of maltogenic amylase is added according to the mass of the total solids of the whole corn syrup.

6. The method for preparing anti-aging whole corn flour with high carotenoid retention rate according to claim 1, characterized in that: In step 2), α-amylase and maltogenic amylase are added to carry out enzymatic hydrolysis for 20 to 40 minutes, and then the temperature is raised to 80 to 90° C. to inactivate the enzyme for 1 to 2 minutes to obtain corn enzymatic hydrolyzed whole slurry.

7. The method for preparing anti-aging whole corn flour with high carotenoid retention rate as claimed in claim 1, characterized in that: In step 3), the pectin solution is a pectin aqueous solution with a mass concentration of 1-2%; the chitosan solution is a chitosan aqueous solution with a mass concentration of 1-2%, the chitosan aqueous solution also contains citric acid with a mass concentration of 1-2%, and the chitosan used is a high-deacetylation chitosan with a deacetylation degree of more than 85%; the pectin solution and the chitosan solution are mixed uniformly in a mass ratio of (9-11):1, and allowed to stand for 12-24 hours to fully swell to form an electrolyte composite gel, thereby obtaining a pectin-chitosan composite electrolyte gel.

8. The method for preparing anti-aging whole corn flour with high carotenoid retention rate as claimed in claim 1, characterized in that: In step 4), the amount of sodium caseinate added is 0.5-1% of the total solids in the corn enzymatic hydrolyzed whole pulp; the amount of pectin-chitosan composite electrolyte gel added is 1-2% of the total solids in the corn enzymatic hydrolyzed whole pulp.

9. The method for preparing anti-aging whole corn flour with high carotenoid retention rate according to claim 1, characterized in that: In step 5), the spray drying conditions are: inlet air temperature 150-180°C, feed rate 2.0-2.5 L / h, hot air flow rate 25-30 m 3 / h, the air outlet temperature is 70~90℃.

10. An anti-aging whole corn flour with high carotenoid retention rate, characterized in that: The anti-aging whole corn flour with high carotenoid retention rate is prepared by the preparation method of any one of claims 1 to 9.

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