Method for preparing low-GI Chinese chestnut powder by utilizing fermentation coupled enzyme technology

Abstract

The invention relates to a method for preparing low-GI Chinese chestnut powder by utilizing a fermentation coupled enzyme technology, which comprises the following steps of: removing shells and inner skins of fresh raw Chinese chestnuts, and screening out insect-free, complete, light yellow and full Chinese chestnut kernels; chinese chestnut kernels are sliced, dried, ground, sieved and sterilized, and treated Chinese chestnut powder is obtained; mixing the sterilized Chinese chestnut powder with sterile water to obtain a Chinese chestnut powder solution, adding a lactobacillus plantarum leavening agent for fermentation to obtain a fermented Chinese chestnut powder solution, centrifuging the fermented Chinese chestnut powder solution to obtain a precipitate, mixing the precipitate with a sodium acetate buffer solution to form a suspension, heating the mixture in a boiling water bath, gelatinizing, and cooling to room temperature; and cooling, adding pullulanase into the mixture, debranching, heating in a boiling water bath after debranching to inactivate the pullulanase, centrifuging to remove the supernatant, and freeze-drying. The method greatly improves the extraction efficiency of the Chinese chestnut starch, reduces the GI value of the Chinese chestnut powder, is non-toxic and harmless, and opens up a new way for deep processing of Chinese chestnuts.

Description

Technical Field

[0001] The invention relates to the technical field of food processing, and in particular to a method for preparing low GI chestnut powder by utilizing fermentation coupled enzyme technology. Background Art

[0002] Chestnut, the fruit of the Fagaceae family, Castanea Mill, is rich in nutrients, but due to the relatively backward processing technology, there are few high value-added products, so there is still a lot of room for development and utilization of its health functions. In recent years, with the annual increase in chestnut production and the development of chestnut deep processing technology, processed chestnut products are easily digested and absorbed by the human body, causing a sharp rise in blood sugar, and the glycemic index (GI value) is relatively high, reaching 60-70.

[0003] Foods are classified according to their GI values ​​into low GI foods, medium GI foods, and high GI foods. Among them, low GI foods: GI value ≤ 55. This type of food stays in the gastrointestinal tract for a long time, has a low absorption rate, releases glucose slowly, has a low peak after entering the blood, a slow decline rate, and small blood sugar fluctuations. Medium GI foods: GI values ​​between 55 and 70 (or 75). The blood sugar response of this type of food is between high GI foods and low GI foods. High GI foods: GI value > 70 (or 75). This type of food is digested quickly after entering the gastrointestinal tract, has a high absorption rate, releases glucose quickly, has a high peak after entering the blood, and has large blood sugar fluctuations.

[0004] The starch content in chestnuts can reach up to about 70%. Changing the structure of chestnut starch is an important way to prepare low-GI chestnut powder. At present, the common methods of extracting chestnut starch mainly include alkaline extraction, fermentation and enzyme extraction. Different extraction processes have their own advantages and disadvantages, and the starch yields vary greatly. Although the alkaline extraction method has a higher yield, it will affect the starch structure and pollute the environment; the fermentation method has significant advantages such as fast growth rate, reduced energy consumption, and improved product quality, and can change its physical, chemical and sensory properties, so it has a relative advantage; the enzyme extraction method has mild conditions, which can improve the solubility and digestibility of the product, and has a high extraction yield. It has significant advantages in protecting the starch structure, improving product quality and purity. However, these extraction methods are mainly focused on the preparation of chestnut starch as a whole, the extraction efficiency needs to be improved, and the GI value is high. There are relatively few studies on the preparation methods of low-GI chestnut powder.

[0005] In view of this, the present invention is proposed. Summary of the invention

[0006] Technical problem to be solved: In view of the problem that the extraction efficiency of the chestnut powder preparation method in the prior art needs to be improved and the GI value is relatively high, the present invention proposes a method for preparing low GI chestnut powder by using fermentation coupled enzyme technology, which greatly improves the extraction efficiency of chestnut starch and reduces the GI value of chestnut powder.

[0007] Technical solution: A method for preparing low GI chestnut powder using fermentation coupled enzyme technology, the steps are as follows:

[0008] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the chestnut kernels that are free of insect pests, complete, light yellow in color and full;

[0009] Step 2: Slice the chestnut kernels, dry them, grind them, sieve them, and sterilize them to obtain the processed chestnut powder;

[0010] Step 3, mixing the sterilized chestnut powder with sterile water to obtain a chestnut powder solution, adding a plant lactobacillus fermentation agent to ferment to obtain a fermented chestnut powder solution, centrifuging the fermented chestnut powder solution to obtain a precipitate, mixing it with a sodium acetate buffer to form a suspension, heating the mixture in a boiling water bath to gelatinize it, and then cooling it to room temperature;

[0011] Step 4: Add pullulanase to the cooled mixture to perform debranching, heat in a boiling water bath to inactivate the pullulanase, remove the supernatant by centrifugation, and then freeze-dry.

[0012] Preferably, the liquid ratio of the sterilized chestnut powder to sterile water in step three is 1 g: 3-7 mL.

[0013] Preferably, the viable count of the plant lactobacillus fermentation agent in step 3 is not less than 1×10 8 CFU / mL, the inoculation amount of Lactobacillus plantarum fermentation agent in the chestnut powder solution was 6-14% (v / v).

[0014] Preferably, the pH value of the sodium acetate buffer in step three is 4.4, and the ratio of the precipitate in the sodium acetate buffer is 14% (w / v).

[0015] Preferably, the ratio of the pullulanase to the sterilized chestnut powder is 40-80U:1g.

[0016] Preferably, in step 2, the chestnut kernel slices have a thickness of 3-5 mm; the drying temperature is 35-45° C., the drying time is 32 h-48 h; and the slices are ground and sieved to 100-200 mesh.

[0017] Preferably, the sterilization in step 2 is low-temperature plasma sterilization treatment, the high-voltage discharge voltage is 45-85kv, the operating frequency is 60-80Hz, and the operating time is 120-180s.

[0018] Preferably, the fermentation time in step three is 18-28 hours.

[0019] Preferably, the reaction time of the pullulanase debranching treatment in step 4 is 3-8h and the reaction temperature is 40-60°C.

[0020] Preferably, in step 4, the product is freeze-dried to a water content of ≤5wt%.

[0021] Beneficial effects:

[0022] (1) The present invention adopts Lactobacillus plantarum fermentation coupled with pullulanase to prepare low GI chestnut powder, and no toxic or harmful solvents are used in the preparation process, which is safe and reliable.

[0023] (2) The present invention can significantly reduce the content of rapidly digestible starch in a relatively short period of time, and the GI value of the chestnut powder finally obtained is relatively low, which is suitable for human digestion and absorption and will not cause large fluctuations in blood sugar.

[0024] (3) The preparation method of the present invention is simple and easy to promote.

[0025] (4) The present invention has a positive significance for promoting the development of the chestnut industry and accelerating the pace of chestnut farmers to get rich, and also opens up a new way for the deep processing of chestnuts. DETAILED DESCRIPTION

[0026] The present invention will be further described below in conjunction with specific embodiments.

[0027] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0028] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0029] Among them, Lactobacillus plantarum SHBCC D16021 and SHBCC D14977 were purchased from Shanghai Collection Biotechnology Center;

[0030] Pullulanase 2000u / g, liquid, model P875969, purchased from Shanghai MacLean Biochemical Technology Co., Ltd.;

[0031] MRS medium, i.e., MRS broth liquid medium, batch number 20240205, was purchased from Shanghai Ruichu Biotechnology Co., Ltd.;

[0032] Sodium acetate buffer, with a concentration of 0.1 mol / L and a pH of 4.4, was prepared from anhydrous sodium acetate and ultrapure water. Anhydrous sodium acetate was of analytical grade and purchased from Sinopharm Chemical Reagent Co., Ltd.

[0033] Example 1

[0034] This embodiment provides a method for preparing low GI chestnut powder using fermentation coupled enzyme technology, the steps are as follows:

[0035] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the pest-free, complete, light yellow and plump chestnut kernels for processing.

[0036] Step 2: Slice the chestnut kernels to a thickness of 3 mm, dry at 35°C for 32 hours, grind through a 100-mesh sieve, and sterilize using low-temperature plasma sterilization (high-voltage discharge voltage of 45 kV, operating frequency of 60 Hz, and operating time of 180 seconds) to obtain the required chestnut powder.

[0037] Step 3: The solid-liquid ratio (g / mL) of chestnut powder to sterile water is 1:5, and the mixture is shaken to obtain a chestnut powder solution; Lactobacillus plantarum SHBCC D16021 is cultured in an MRS medium (the content of Lactobacillus plantarum is 10% (v / v)) in a 37°C constant temperature incubator until the late exponential phase (18 h), the cells are collected and centrifuged (3000 r, 3 min), washed 3 times with sterile saline, and resuspended to 10 8 CFU / mL, as a fermentation agent. 6% (v / v) fermentation agent was inoculated into the chestnut powder solution, shaken on a shaker for 5 minutes, and fermented in a constant temperature incubator at 37°C for 20 hours. The fermented solution was centrifuged (4000r, 10min) and the precipitate was mixed with a sodium acetate buffer of pH 4.4 to form a 14% (w / v) suspension. The mixture was then heated in a boiling water bath for 20 minutes to ensure complete gelatinization, and gelatinized chestnut powder was obtained after cooling to room temperature. 40U pullulanase was added to each gram of gelatinized chestnut powder, and stirred in a 55°C water bath for 4h to carry out the debranching process. After debranching, the sample was placed in a boiling water bath for 30min to inactivate the pullulanase, centrifuged (4000r, 10min), the precipitate was taken, and freeze-dried to a moisture content of 5wt% to obtain low GI chestnut powder.

[0038] Example 2

[0039] This embodiment provides a method for preparing low GI chestnut powder using fermentation coupled enzyme technology, the steps are as follows:

[0040] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the pest-free, complete, light yellow and plump chestnut kernels for processing.

[0041] Step 2: Slice the chestnut kernels to a thickness of 4 mm, dry at 40°C for 40 h, grind through a 100-mesh sieve, and sterilize using low-temperature plasma sterilization (high-voltage discharge voltage of 85 kV, operating frequency of 80 Hz, and operating time of 120 s) to obtain the required chestnut powder.

[0042] Step 3: The solid-liquid ratio (g / mL) of chestnut powder to sterile water is 1:6, and the mixture is shaken to obtain a chestnut powder solution; Lactobacillus plantarum SHBCC D16021 is cultured in an MRS medium (the content of Lactobacillus plantarum is 10% (v / v)) in a 37°C constant temperature incubator until the late exponential phase (18 h), the cells are collected and centrifuged (3000 r, 3 min), washed 3 times with sterile saline, and resuspended to 10 8 CFU / mL, as a fermentation agent. Inoculate 8% (v / v) of the fermentation agent into the chestnut powder solution, shake on a shaker for 5 minutes, and ferment in a constant temperature incubator at 37°C for 24 hours. The fermented solution was centrifuged (4000r, 10min) and the precipitate was mixed with a sodium acetate buffer of pH 4.4 to form a 14% (w / v) suspension. The mixture was then heated in a boiling water bath for 20 minutes to ensure complete gelatinization, and gelatinized chestnut powder was obtained after cooling to room temperature. 60U of pullulanase was added to each gram of gelatinized chestnut powder, and stirred in a 50°C water bath for 6 hours to carry out the debranching process. After debranching, the sample was placed in a boiling water bath for 30 minutes to inactivate the pullulanase and centrifuged (4000r, 10min). Freeze-dried to a moisture content of 4wt%, a low GI chestnut powder was obtained.

[0043] Example 3

[0044] This embodiment provides a method for preparing low GI chestnut powder using fermentation coupled enzyme technology, the steps are as follows:

[0045] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the pest-free, complete, light yellow and plump chestnut kernels for processing.

[0046] Step 2: Slice the chestnut kernels into slices with a thickness of 5 mm, dry at 45°C for 48 hours, grind through a 200-mesh sieve, and sterilize with low-temperature plasma (high-voltage discharge voltage is 85 kV, operating frequency is 80 Hz, and operating time is 120 seconds) to obtain the required chestnut powder.

[0047] Step 3: The solid-liquid ratio (g / mL) of chestnut powder to sterile water is 1:4, and the mixture is shaken to obtain a chestnut powder solution; Lactobacillus plantarum SHBCC D16021 is cultured in an MRS medium (the content of Lactobacillus plantarum is 10% (v / v)) in a 37°C constant temperature incubator until the late exponential phase (18 h), the cells are collected and centrifuged (3000 r, 3 min), washed 3 times with sterile saline, and resuspended to 10 8CFU / mL, as a fermentation agent. 12% (v / v) fermentation agent was inoculated into the chestnut powder solution, shaken on a shaker for 5 minutes, and fermented in a constant temperature incubator at 37°C for 18 hours. The fermented solution was centrifuged (4000r, 10min) and the precipitate was mixed with a sodium acetate buffer of pH 4.4 to form a 14% (w / v) suspension. The mixture was then heated in a boiling water bath for 20 minutes to ensure complete gelatinization, and gelatinized chestnut powder was obtained after cooling to room temperature. 50U pullulanase was added to each gram of gelatinized chestnut powder, and stirred in a 45°C water bath for 8 hours to carry out the debranching process. After debranching, the sample was placed in a boiling water bath for 30 minutes to inactivate the pullulanase and centrifuged (4000r, 10min). Freeze-dried to a moisture content of 3wt%, a low GI chestnut powder was obtained.

[0048] Comparative Example 1: Original chestnut powder

[0049] The same as Example 3, except that this comparative example only provides raw chestnut powder.

[0050] The specific steps are as follows:

[0051] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the pest-free, complete, light yellow and plump chestnut kernels for processing.

[0052] Step 2: Slice the chestnut kernels into slices with a thickness of 5 mm, dry at 45°C for 48 hours, grind through a 200-mesh sieve, and sterilize with low-temperature plasma (high-voltage discharge voltage is 85 kV, operating frequency is 80 Hz, and operating time is 120 seconds) to obtain the required chestnut powder.

[0053] Comparative Example 2 Lactobacillus plantarum fermentation

[0054] The same as Example 3, except that this comparative example does not use the enzymatic debranching process.

[0055] The specific steps are as follows:

[0056] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the pest-free, complete, light yellow and plump chestnut kernels for processing.

[0057] Step 2: Slice the chestnut kernels into slices with a thickness of 5 mm, dry at 45°C for 48 hours, grind through a 200-mesh sieve, and sterilize with low-temperature plasma (high-voltage discharge voltage is 85 kV, operating frequency is 80 Hz, and operating time is 120 seconds) to obtain the required chestnut powder.

[0058] Step 3: The solid-liquid ratio (g / mL) of chestnut powder to sterile water is 1:4, and the mixture is shaken to obtain a chestnut powder solution; Lactobacillus plantarum SHBCC D16021 is cultured in an MRS medium (the content of Lactobacillus plantarum is 10% (v / v)) in a 37°C constant temperature incubator until the late exponential phase (18 h), the cells are collected and centrifuged (3000 r, 3 min), washed 3 times with sterile saline, and resuspended to 10 8 CFU / mL, as a fermentation agent. Inoculate 12% (v / v) of the fermentation agent into the chestnut powder solution, shake on a shaker for 5 minutes, and ferment in a 37°C constant temperature incubator for 18 hours. Centrifuge the fermented solution (4000r, 10min) to obtain the precipitate, and freeze-dry it to a moisture content of 3wt% to obtain bacterial fermented chestnut powder.

[0059] Comparative Example 3 Pullulanase debranching

[0060] The same as Example 3, except that this comparative example does not adopt the bacterial fermentation process.

[0061] The specific steps are as follows:

[0062] Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the pest-free, complete, light yellow and plump chestnut kernels for processing.

[0063] Step 2: Slice the chestnut kernels into slices with a thickness of 5 mm, dry at 45°C for 48 hours, grind through a 200-mesh sieve, and sterilize with low-temperature plasma (high-voltage discharge voltage is 85 kV, operating frequency is 80 Hz, and operating time is 120 seconds) to obtain the required chestnut powder.

[0064] Step 3, chestnut powder is mixed with sodium acetate buffer at pH 4.4 to form a 14% (w / v) suspension. The mixture is then heated in a boiling water bath for 20 minutes to ensure complete gelatinization, and gelatinized chestnut powder is obtained after cooling to room temperature. 50U pullulanase is added to each gram of gelatinized chestnut powder, and stirred in a 45°C water bath for 8h to carry out the debranching process. After debranching, the sample is placed in a boiling water bath for 30min to inactivate the pullulanase and centrifuged (4000r, 10min). Freeze-dried to a moisture content of 3wt%, a low GI chestnut powder is obtained.

[0065] About the selection of plant lactobacillus, before the present application was carried out, the applicant studied the influence of plant lactobacillus SHBCC D16021 fermentation on the nutritional quality and digestibility of chestnut powder, and compared with the fermentation of control group plant lactobacillus SHBCC D14977 (method is the same as comparative example 2, difference is, bacteria are different) and spontaneous fermentation (method is the same as comparative example 2, difference is, bacteria are not added). SHBCC D16021 fermentation improves the resistance of chestnut powder to hydrolytic enzyme. Compared with SHBCC D14977 fermentation and spontaneous fermentation, the resistant starch content of SHBCC D16021 fermented chestnut powder is the highest (6.13g / 100g), and the predicted glycemic index is the lowest (54.03). Therefore, plant lactobacillus SHBCC D16021 starch fermentation is a promising method to improve the nutritional value of chestnut powder and reduce the digestibility of chestnut powder.

[0066] The digestibility and eGI values ​​of chestnut flour products obtained by different fermentation treatments were determined, as shown in Table 1:

[0067] Table 1 Comparison of various indexes of chestnut flour after different fermentation treatments

[0068]

[0069] Previous studies have shown that the activity of pullulanase has a dual effect on the synthesis and degradation of starch. The debranching of starch by pullulanase increases its amylose content. The resistant starch content increases with the increase of pullulanase dosage. The higher the resistant starch content, the lower the predicted glycemic index. In summary, this study used the method of high-density fermentation of Lactobacillus plantarum SHBCC D16021 coupled with pullulanase to prepare low GI chestnut powder.

[0070] In addition, the digestion rates and eGI values ​​of the products obtained in Examples 1-3 and Comparative Examples 1 and 3 were measured, as shown in Table 2:

[0071] Table 2 Comparison of various indexes of chestnut flour and its modified

[0072] index Original chestnut powder Pullulanase debranching Example 1 Example 2 Example 3 RS(%) <![CDATA[73.65±2.38 a ]]> <![CDATA[46.15±0.46 b ]]> <![CDATA[32.98±0.43 c ]]> <![CDATA[30.12±2.31 d ]]> <![CDATA[33.65±0.52 c ]]> SDS(%) <![CDATA[10.12±2.03 b ]]> <![CDATA[31.73±1.16 a ]]> <![CDATA[40.32±0.37 c ]]> <![CDATA[42.34±2.08 b ]]> <![CDATA[45.16±0.46 c ]]> RDS(%) <![CDATA[16.23±0.35 c ]]> <![CDATA[22.12±0.85 c ]]> <![CDATA[26.70±0.07 b ]]> <![CDATA[27.54±0.32 a ]]> <![CDATA[21.19±0.08 b ]]> eGI <![CDATA[62.30±2.12 a ]]> <![CDATA[58.60±1.96 c ]]> <![CDATA[52.80±0.36 b ]]> <![CDATA[53.10±0.63 a ]]> <![CDATA[49.20±0.71 c ]]>

[0073] Note: Starch can be divided into three categories according to digestion rate, namely rapidly digestible starch (RDS), slowly digestible starch (SDS) and resistant starch (RS). The glucose content can be calculated by measuring the absorbance of the starch solution at 0, 20 and 120 minutes, and then the digestibility can be calculated by the formula, which is the percentage in the table.

[0074] It can be seen from Tables 1 and 2 that the SDS content (SDS average in Examples 1-3) of chestnut flour after fermentation coupled with pullulanase treatment is 3.21 times, 0.63 times and 0.34 times higher than that of original chestnut flour, bacterial fermentation and enzymatic debranching.

[0075] Lactobacillus plantarum fermentation reduced the total starch content in chestnut flour, and the resistant starch content of fermented chestnut flour reached 52.23%, with a predicted glycemic index of 57.2. Therefore, Lactobacillus plantarum fermentation effectively improved the nutritional value of chestnut flour and reduced the digestibility of chestnut flour.

[0076] In the process of debranching and degradation, the contents of RDS, SDS and RS of pullulanase debranched chestnut powder changed. Compared with the original chestnut powder, the RS level of debranched starch was higher. The resistant starch in the original chestnut powder generally has a dense structure, and its resistance disappears with the completion of gelatinization, forming an amorphous structure that is conducive to digestion and absorption, and the digestion performance is improved; the starch is modified by fermentation coupled enzyme technology, which not only has the formation process of amorphous areas, but also undergoes retrogradation treatment after debranching, which promotes the recrystallization of SDS formation. Therefore, the SDS content of the modified chestnut starch is correspondingly increased compared with the original starch, while the RS content is reduced compared with the original starch.

[0077] In embodiment 1-3, after chestnut powder is treated by plant lactobacillus fermentation coupled enzyme technology, the RDS content of chestnut powder after gelatinization is significantly reduced, and the SDS and RS contents are significantly increased. The digestibility of chestnut powder after bacterial fermentation coupled enzyme debranching treatment is weakened. Plant lactobacillus fermentation coupled enzyme combined treatment can degrade starch molecules, partially destroying the spiral, crystalline and layered structures originally present in natural starch. The chestnut powder after treatment has higher resistance to enzymatic hydrolysis (RS increases). Preferably, embodiment 3, bacterial fermentation coupled enzyme debranching treatment can change the structure on multiple scales to effectively regulate the digestibility of chestnut powder and eventually convert part of RDS / SDS into RS, RDS and SDS mass fractions are significantly reduced, and at the same time the mass fraction of RS is improved, and the eGI value reaches the minimum (49.2). According to the above results, it can be concluded that the alleviation of starch aging / enzyme action during bacterial fermentation coupled enzyme treatment will cause the starch hierarchy to be destroyed, thereby changing the digestion and gelatinization characteristics of chestnut powder, and then showing higher resistance to enzymatic hydrolysis in the digestion process and showing higher resistance to water and heat effect in the gelatinization process.

[0078] Finally, it should be noted that the above implementation modes are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned implementation modes, a person of ordinary skill in the art should understand that the technical solutions described in the aforementioned implementation modes can still be modified, or some or all of the technical features therein can be replaced by equivalents. However, these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the implementation modes of the present invention.

Claims

1. A method for preparing low GI chestnut powder using fermentation coupled enzyme technology, characterized in that: Here are the steps: Step 1: Remove the outer shell and inner skin of fresh raw chestnuts, and select the chestnut kernels that are free of insect pests, complete, light yellow in color and full; Step 2: Slice the chestnut kernels, dry them, grind them, sieve them, and sterilize them to obtain the processed chestnut powder; Step 3, mixing the sterilized chestnut powder with sterile water to obtain a chestnut powder solution, adding a plant lactobacillus fermentation agent to ferment to obtain a fermented chestnut powder solution, centrifuging the fermented chestnut powder solution to obtain a precipitate, mixing it with a sodium acetate buffer to form a suspension, heating the mixture in a boiling water bath to gelatinize it, and then cooling it to room temperature; Step 4: Add pullulanase to the cooled mixture to perform debranching, heat in a boiling water bath to inactivate the pullulanase, remove the supernatant by centrifugation, and then freeze-dry.

2. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: The liquid ratio of the sterilized chestnut powder to sterile water in step three is 1 g: 3-7 mL.

3. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: The viable count of the plant lactobacillus fermentation agent in step 3 is not less than 1×10 8 CFU / mL, the inoculation amount of Lactobacillus plantarum fermentation agent in the chestnut powder solution was 6-14% (v / v).

4. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: The pH value of the sodium acetate buffer in the step 3 is 4.4, and the ratio of the precipitate in the sodium acetate buffer is 14% (w / v).

5. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: In the step 4, the ratio of pullulanase to the sterilized chestnut powder is 40-80 U: 1 g.

6. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: In the step 2, the chestnut kernel slices have a thickness of 3-5 mm; the drying temperature is 35-45° C., and the drying time is 32 h-48 h; and the slices are ground and sieved to 100-200 mesh.

7. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: The sterilization in step 2 is low-temperature plasma sterilization treatment, the high-voltage discharge voltage is 45-85kv, the working frequency is 60-80Hz, and the working time is 120-180s.

8. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: The fermentation time in step 3 is 18-28 hours.

9. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: In the step 4, the reaction time of the pullulanase debranching treatment is 3-8 hours, and the reaction temperature is 40-60°C.

10. The method for preparing low GI chestnut powder using fermentation coupled enzyme technology according to claim 1, characterized in that: In the step 4, the product is freeze-dried to a moisture content of ≤5wt%.

Images