Preparation method and application of resistant starch

Abstract

The invention belongs to the technical field of food processing, and particularly relates to a preparation method and application of resistant starch. By optimizing drying process parameters (temperature, humidity control and the like), the damage of spray drying (high-temperature hydrogen bond damage), vacuum freeze drying (water loss of a crystal channel caused by sublimation of ice crystals) and traditional hot air drying (untimely loss of bound water caused by unregulated moisture distribution) to the starch double-helix structure in the prior art is effectively avoided. By maintaining a moisture environment required by recrystallization of starch molecules, ordered arrangement of starch chains is promoted, the relative crystallinity of the resistant starch is remarkably improved, and the problems of incomplete crystal structure and limited digestion resistance caused by an existing drying process are solved; and a key technical support is provided for large-scale application in the fields of baked foods, meal replacement products, pharmaceutical preparations and the like.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of food processing, and particularly relates to a preparation method and application of resistant starch. BACKGROUND

[0002] Resistant starch (RS) refers to anti-digestive starch which cannot be digested and absorbed by the small intestine and can be fermented into short-chain fatty acids by microorganisms in the colon. It has the effects of inhibiting postprandial blood glucose increase, reducing blood lipids, and promoting the proliferation of intestinal probiotics. RS3 is a kind of anti-digestive starch. In the recrystallization process of resistant starch, water molecules are re-integrated into the double helix structure of starch to form a stable crystal structure. There are two corresponding relationships between the structural properties of resistant starch and its water distribution, one is the bound water of tightly combined starch chains, and the other is the water existing in the channel of starch crystal. The water content determines the proportion of microcrystals in resistant starch. Therefore, by treating the water molecules in resistant starch and then affecting the molecular structure, the purpose of regulating the anti-digestive property of starch can be achieved. Therefore, in the preparation process of resistant starch, the drying process is crucial to the retention of the crystal structure of resistant starch. If the crystal structure is destroyed or the water distribution is unbalanced during the drying process, the content of resistant starch will directly decrease.

[0003] In the prior art, the drying methods of resistant starch mainly include spray drying, vacuum freeze drying and hot air drying, but all have significant defects. Spray drying and vacuum freeze drying destroy the crystal structure of resistant starch and reduce the content of resistant starch. Hot air drying removes water through hot air convection, which can retain more crystal structure compared with spray drying and vacuum freeze drying, and the content of bound water is the highest, and the content of RS is 17.72%. However, the environmental humidity is not precisely controlled during the drying process, which easily leads to the premature loss of starch chain bound water, limits the recrystallization efficiency of starch molecules, and cannot further improve the crystallinity and the content of resistant starch, so it is difficult to meet the demand of functional food for high content of resistant starch.

[0004] Therefore, it is a technical problem to be solved in the field to develop a preparation method of resistant starch which can effectively protect the crystal structure of starch and improve the relative crystallinity. SUMMARY

[0005] In order to solve the problems existing in the prior art, the application provides a preparation method and application of resistant starch. On the basis of hot air drying, the high humidity drying method is added, which can protect the crystal structure of water molecules and starch molecules in resistant starch, thereby increasing the content of RS3 type resistant starch in resistant starch.

[0006] The object of the application can be achieved by the following technical scheme: In a first aspect, the present application provides a method for preparing resistant starch, comprising the following steps: S1, preparing a starch slurry with ordinary corn starch and water; S2, adjusting the pH of the starch slurry to 3-6, and stirring the starch slurry at 115-125℃ to gelatinize the starch, thereby obtaining a starch paste; S3, cooling the starch paste to 55-60℃, then adding pullulanase for reaction, and after the reaction is completed, heating to 85-90℃ to inactivate the enzyme, and cooling to retrograde; S4, centrifuging the retrograded sample, and then moisturizing and drying or segmenting, drying, sieving, and obtaining the resistant starch.

[0007] Further, in step S1, the mass percentage of the starch slurry can be 1-30wt%.

[0008] Further, in step S1, the mass percentage of the starch slurry can be 1wt%, 3wt%, 4wt%, 5wt%, 10wt%, 15wt%, 20wt% or 30wt%, etc., but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0009] Further, in step S2, the pH of the starch slurry can be adjusted to 3, 3.5, 4, 4.5, 5 or 6.5, etc., but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0010] Further, in step S2, the stirring temperature of the starch slurry can be 115℃, 116℃, 117℃, 118℃, 119℃, 120℃, 121℃, 122℃, 123℃, 124℃ or 125℃, etc., but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0011] Further, in step S2, the stirring time can be 10min, 15min, 20min, 25min or 30min, etc., but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0012] Further, in step S3, the starch paste can be cooled to 55℃, 56℃, 57℃, 58℃, 59℃, 60℃, 61℃, 62℃, 63℃, 64℃ or 65℃, etc., but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0013] Further, in step S3, the working concentration of the pullulanase can be 20U / g, 30U / g or 40U / g, etc., but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0014] Further, in step S3, the reaction time can be 2.5 h, 3 h or 3.5 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0015] Further, in step S3, the temperature after the end of the reaction can be 85°C, 86°C, 87°C, 88°C, 89°C or 90°C, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0016] Further, in step S3, the regeneration after cooling is specifically: cooling to room temperature, taking out the reaction liquid, and placing in a 4°C refrigerator for 24 h.

[0017] Further, in step S4, the centrifugation condition is 5000 r / min for 15 min to remove water and soluble sugar, which can reduce the hardness of the product after drying.

[0018] Further, in step S4, after centrifugation, the sample is also spread on a 600-mesh screen with a film thickness of 1-2 mm, and the screen with the sample is evenly laid in a constant temperature and humidity box.

[0019] Further, in step S4, in the constant temperature and humidity box, the moisture drying is: setting the temperature to 45-60°C and the humidity to 20%-95% for drying for 2.5-20 h; or, setting the temperature to 45-60°C and setting the linear humidity range to a humidity of 99%-60% for drying for 2.5-20 h.

[0020] Further, in step S4, the moisture drying is: the temperature can be set to 45°C, 50°C or 60°C, the humidity can be set to 20%, 55%, 75% or 95%, and the drying time can be 2.5 h, 3 h, 6.5 h, 11 h, 15 h or 20 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable; or, the temperature can be set to 45°C, 50°C or 60°C, the linear humidity range is set to a humidity of 99%-60%, and the drying time can be 2.5 h, 3 h, 6.5 h, 11 h, 15 h or 20 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0021] Further, in step S4, the moisture drying is: the temperature can be set to 45°C, 50°C or 60°C, the humidity can be set to 20%, 55%, 75% or 95%, and the drying time can be 2.5 h, 3 h, 6.5 h, 11 h, 15 h or 20 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable; or, the temperature can be set to 45°C, 50°C or 60°C, the linear humidity range is set to a humidity of 99%-60%, and the drying time can be 2.5 h, 3 h, 6.5 h, 11 h, 15 h or 20 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0021] Further, in step S4, the moisture drying is: the temperature can be set to 45°C, 50°C or 60°C, the humidity can be set to 20%, 55%, 75% or 95%, and the drying time can be 2.5 h, 3 h, 6.5 h, 11 h, 15 h or 20 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable; or, the temperature can be set to 45°C, 50°C or 60°C, the linear humidity range is set to a humidity of 99%-60%, and the drying time can be 2.5 h, 3 h, 6.5 h, 11 h, 15 h or 20 h, but is not limited to the above-mentioned values, and other values not mentioned in the above-mentioned value range are also applicable.

[0022] The first section temperature setting can be 40 DEG C, 45 DEG C or 50 DEG C, and the drying time can be 1.5h, 2h or 2.5h; the second section temperature setting can be 55 DEG C, 60 DEG C or 65 DEG C, and the drying time can be 1.5h, 2h or 2.5h, but is not limited to the above listed values, and other values not listed in the above value range are also applicable.

[0023] Further, in step S4, the segmental moisturizing drying is as follows: the first section temperature setting is 40-50 DEG C, the linear humidity is set to 99-80%, and the drying time is 1.5-2.5h; the second section temperature setting is 55-65 DEG C, the linear humidity is set to 80-70%, and the drying time is 1.5-2.5h.

[0024] The first section temperature setting can be 40 DEG C, 45 DEG C or 50 DEG C, and the drying time can be 1.5h, 2h or 2.5h; the second section temperature setting can be 55 DEG C, 60 DEG C or 65 DEG C, and the drying time can be 1.5h, 2h or 2.5h, but is not limited to the above listed values, and other values not listed in the above value range are also applicable.

[0025] Further, in step S4, the drying is specifically overnight in a dryer.

[0026] Further, in step S4, the mesh number of the sieve is 50 mesh.

[0027] In a second aspect of the present application, the resistant starch prepared by the preparation method is applied to the preparation of functional food.

[0028] The above technical solution has the following beneficial effects compared with the prior art: (1) The present application effectively avoids the damage to the double helix structure of starch in the prior art, such as spray drying (high temperature destroys hydrogen bonds), vacuum freeze drying (ice crystal sublimation leads to water loss in crystal channels) and traditional hot air drying (uncontrolled water distribution leads to premature loss of bound water), by optimizing the water control mechanism in the drying process. By maintaining the water environment required for starch molecular recrystallization, the ordered arrangement of starch chains is promoted, and the relative crystallinity of resistant starch is significantly improved, solving the problem of incomplete crystalline structure and limited anti-digestion caused by the existing drying process.

[0029] (2) Compared with the existing hot air drying process, the present application further improves the content of resistant starch (up to 41.69%) by protecting the crystalline structure. The high crystallinity of the starch molecular structure gives the product stronger anti-digestion, which can more effectively play the physiological functions of regulating postprandial blood glucose, reducing blood lipids, promoting the proliferation of intestinal probiotics, etc., and provides a higher quality raw material basis for functional food and health products.

[0030] (3) The application optimizes the process on the basis of traditional hot air drying, without introducing complex high-energy-consumption equipment such as vacuum freeze drying, has low energy consumption in the production process, and significantly reduces the equipment investment and maintenance cost. Meanwhile, the process parameters are easy to control, the drying efficiency is high, the existing food processing production line can be directly adapted, the problems of large industrialization difficulty and high cost of the existing resistant starch drying technology are solved, and the scale production and market promotion are facilitated. BRIEF DESCRIPTION OF DRAWINGS

[0031] Figure 1 XRD patterns of resistant starches with different drying humidity in the embodiments of the application; Figure 2 Moisture distribution diagrams of resistant starches with different drying humidity in the embodiments of the application. DETAILED DESCRIPTION

[0032] The application will be further described in detail below with reference to the specific embodiments, and the embodiments provided below are only for illustrating the application, rather than limiting the scope of the application. The embodiments provided below can serve as a guide for further improvement by those skilled in the art, and do not constitute any limitation on the application in any way.

[0033] In the following examples, the experimental methods are all conventional methods, and are performed according to the techniques or conditions described in the literature in the art or according to the product instructions, unless otherwise specified. The materials, reagents and the like used in the following examples can be obtained from commercial channels, unless otherwise specified.

[0034] 1. Determination of resistant starch content and amylose content The resistant starch content was determined according to the AOAC method 2002.02, and the amylose content was determined using an amylose kit (K-AMYL, Megazyme).

[0035] 2. Calculation of relative crystallinity (RC) The relative crystallinity was calculated using jade 6.0 software.

[0036] 3. Common corn starch The common corn starch was brand bowling, purchased from bowling biological Co., Ltd.

[0037] 4. Pullulanase The pullulanase (LP482001, 2000 U / mL) was purchased from Cool Chemical Technology Co., Ltd.

[0038] Example 1 Step 1: Prepare a starch slurry of normal corn starch (RS content of 1.05%) with water at a ratio of 1:20, adjust the ph to 4.5, and place it in a high-temperature fermentation tank. Stir while heating to 121℃ for 20 min, then cool to 60℃. Add 30 U / g of pullulanase at 60℃ and 150 r / min for 3 h of enzymatic hydrolysis. Then heat the fermentation tank to 85℃ for 10 min to inactivate the enzyme, cool to room temperature, remove the liquid, and place it in a refrigerator at 4℃ for 24 h of retrogradation.

[0039] Step 2: Centrifuge the retrograded sample at 5000 r / min for 15 min to remove water and soluble sugars, which can reduce the hardness of the dried product. Grind the sample and pass it through a 50-mesh sieve to increase the permeability by 20%.

[0040] Step 3: Apply the retrograded sample to a 600-mesh screen with a coating thickness of 1-2 mm. Uniformly lay the sample-coated screen in a constant temperature and humidity chamber.

[0041] Step 4: Set the temperature of the constant temperature and humidity chamber to 45℃ and the humidity to 20%. Dry for 2.5 h.

[0042] Step 5: Place the dried sample in a desiccator overnight to equilibrate the moisture. Grind the sample with a grinder and pass it through a 50-mesh sieve with a permeability of more than 98% to obtain corn resistant starch.

[0043] Example 2 Steps 1-3 are the same as in Example 1.

[0044] Step 4: Set the temperature of the constant temperature and humidity chamber to 45℃ and the humidity to 55%. Dry for 6.5 h.

[0045] Step 5: Same as Example 1.

[0046] Example 3 Steps 1-3 are the same as in Example 1.

[0047] Step 4: Set the temperature of the constant temperature and humidity chamber to 45℃ and the humidity to 75%. Dry for 11 h.

[0048] Step 5: Same as Example 1.

[0049] Example 4 Steps 1-3 are the same as in Example 1.

[0050] Step 4: Set the temperature of the constant temperature and humidity chamber to 45℃ and the humidity to 95%. Dry for 20 h.

[0051] Step 5: Same as Example 1.

[0052] Example 5 Steps 1-3 are the same as in Example 1.

[0053] Step 4: The sample was heated in a water bath at 45 °C for 17.5 h before drying, the temperature of the constant temperature and humidity box was set to 45 °C, the humidity was set to 20%, and the sample was dried for 2.5 h.

[0054] Step 5: Same as Example 1.

[0055] Example 6 Steps 1-3: Same as Example 1.

[0056] Step 4: The sample was heated in a water bath at 45 °C for 13.5 h before drying, the temperature of the constant temperature and humidity box was set to 45 °C, the humidity was set to 55%, and the sample was dried for 6.5 h.

[0057] Step 5: Same as Example 1.

[0058] Example 7 Steps 1-3: Same as Example 1.

[0059] Step 4: The sample was heated in a water bath at 45 °C for 9 h before drying, the temperature of the constant temperature and humidity box was set to 45 °C, the humidity was set to 75%, and the sample was dried for 11 h.

[0060] Step 5: Same as Example 1.

[0061] Example 8 Steps 1-3: Same as Example 1.

[0062] Step 4: The temperature of the constant temperature and humidity box was set to 45 °C, the humidity was set to 95%, and the sample was dried for 20 h.

[0063] Step 5: Same as Example 1.

[0064] Example 9 Steps 1-3: Same as Example 1.

[0065] Step 4: The temperature of the constant temperature and humidity box was set to 45 °C, the humidity was set to 95%, and the sample was dried for 20 h.

[0066] Step 5: Same as Example 1.

[0067] Example 10 Steps 1-3: Same as Example 1.

[0068] Step 4: The temperature of the constant temperature and humidity box was set to 60 °C, the humidity was set to 95%, and the sample was dried for 10 h.

[0069] Step 5: Same as Example 1.

[0070] Example 11 Steps 1-3: Same as Example 1.

[0071] Step 4: The temperature of the constant temperature and humidity chamber was set to 80°C, and the humidity was set to 95%, and dried for 5 h.

[0072] Step 5: The same as Example 1.

[0073] Example 12 Steps 1-3: The same as Example 1.

[0074] Step 4: The temperature of the constant temperature and humidity chamber was set to 45°C, and the linear humidity was set to 99-60%, and dried for 6 h.

[0075] Step 5: The same as Example 1.

[0076] Example 13 Steps 1-3: The same as Example 1.

[0077] Step 4: The temperature of the constant temperature and humidity chamber was set to 60°C, and the linear humidity was set to 99-70%, and dried for 3 h.

[0078] Step 5: The same as Example 1.

[0079] Example 14 Steps 1-3: The same as Example 1.

[0080] Step 4: The drying temperature was segmented, the first segment was set to 45°C, and the linear humidity was set to 99-80%, and dried for 2 h; the second segment was set to 60°C, and the linear humidity was set to 80-70%, and dried for 2 h.

[0081] Step 5: The same as Example 1.

[0082] Example 15 Steps 1-3: The same as Example 1.

[0083] Step 4: The drying temperature was segmented, the first segment was set to 60°C, and the linear humidity was set to 99-80%, and dried for 2 h; the second segment was set to 45°C, and the linear humidity was set to 80-70%, and dried for 2 h.

[0084] Step 5: The same as Example 1.

[0085] The content of resistant starch, the content of amylose in the resistant starch prepared in Examples 1-4 were detected, and the xrd and moisture distribution of resistant starch under different drying humidity were detected. The results are shown in Table 1, Figure 1 , Figure 2

[0086] Table 1 Influence of different humidity on the content of resistant starch

[0087] ​As shown in Table 1, the RS content of resistant starch is the highest when dried at 95% humidity, which is 88.03% higher than that of common hot air drying (20% humidity). Different drying humidity has little effect on the final moisture content and the amylose content.

[0088] As shown in Table 1, the RS content of resistant starch is the highest when dried at 95% humidity, which is 88.03% higher than that of common hot air drying (20% humidity). Different drying humidity has little effect on the final moisture content and the amylose content. Figure 1 As shown in Table 1, the RS content of resistant starch is the highest when dried at 95% humidity, which is 88.03% higher than that of common hot air drying (20% humidity). Different drying humidity has little effect on the final moisture content and the amylose content.

[0089] As shown in Table 1, the RS content of resistant starch is the highest when dried at 95% humidity, which is 88.03% higher than that of common hot air drying (20% humidity). Different drying humidity has little effect on the final moisture content and the amylose content. Figure 2 As shown in Table 1, the RS content of resistant starch is the highest when dried at 95% humidity, which is 88.03% higher than that of common hot air drying (20% humidity). Different drying humidity has little effect on the final moisture content and the amylose content.

[0090] As shown in Table 1, the RS content of resistant starch is the highest when dried at 95% humidity, which is 88.03% higher than that of common hot air drying (20% humidity). Different drying humidity has little effect on the final moisture content and the amylose content.

[0091] The RS content of resistant starch prepared in Examples 5-8 was detected. The results are shown in Table 2.

[0092] Table 2

[0093] To exclude the effect of heating time on the sample, the sample was placed in a water bath before drying for a certain period of time to keep the total heating time of all samples consistent. The results of Examples 5-8 show that the heating time has little effect on the RS content of resistant starch.

[0094] The RS content of resistant starch prepared in Examples 9-11 was detected. The results are shown in Table 3.

[0095] Table 3

[0096] The results show that high temperature of 80°C destroys the crystal structure of resistant starch, causing it to melt during high humidity drying, and the drying effect is best at 45°C.

[0097] The RS content of resistant starch prepared in Examples 12-16 was detected. The results are shown in Table 4.

[0098] Table 4 Drying temperature segmentation and linear humidity drying

[0099] From the results of Table 4, if only 60℃ drying, shorter drying time, higher temperature at high humidity will reduce the RS content. Only 45℃ drying, longer drying time, lower subsequent humidity, reduce the RS content.

[0100] The resistant starch obtained by combining the segment temperature change and linear humidity change drying method greatly shortens the drying time, the RS content of the resistant starch treated at 45℃ first and then at 60℃ is 41.69%, higher than that at 45℃ and 95% humidity, and the drying time is reduced by 80% compared with that at 45℃ and 95% humidity.

[0101] Finally, it should be noted that the above only for the preferred embodiments of the present application, and is not intended to limit the present application, although the foregoing detailed description of the present application is made with reference to the foregoing examples, for those skilled in the art, it still can be modified, or part of the equivalent replacement of the technical solutions recorded in the foregoing examples. Any modification, equivalent replacement, improvement, etc. within the spirit and principles of the present application shall be included within the scope of protection of the present application. Although the above describes the specific embodiments of the present application, it is not a limitation on the scope of protection of the present application, those skilled in the art should understand that on the basis of the technical solutions of the present application, various modifications or changes made by those skilled in the art without the need for creative labor are still within the scope of protection of the present application.

Claims

1. A method for preparing resistant starch, characterized in that, Includes the following steps: S1. A starch slurry is prepared using ordinary corn starch and water; S2. Adjust the pH of the starch slurry to 3-6, and stir the starch slurry at 115-125℃ to gelatinize the starch and obtain starch paste. S3. Cool the starch paste to 55~60℃, then add pullulanase to react. After the reaction is complete, raise the temperature to 85~90℃ to inactivate the enzyme, and then cool and regenerate. S4. After centrifugation, the regenerated sample is moistened and dried or dried in segments, dried, and sieved to obtain the final product.

2. The preparation method according to claim 1, characterized in that, In step S1, the mass concentration of the starch slurry is 1wt%~30wt%.

3. The preparation method according to claim 1, characterized in that, In step S2, the stirring time is 10~30 minutes.

4. The preparation method according to claim 1, characterized in that, In step S3, the working concentration of pullulanase is 20~40 U / g.

5. The preparation method according to claim 1, characterized in that, In step S3, the reaction time is 2.5~3.5h.

6. The preparation method according to claim 1, characterized in that, In step S4, the moisturizing and drying process involves setting the temperature to 45~60℃, the humidity to 20%~95%, and drying for 2.5~20 hours. Alternatively, the temperature in the constant temperature and humidity chamber can be set to 45~60℃, and the linear humidity range can be set to 99%~60%, with a drying time of 2.5~20 hours.

7. The preparation method according to claim 1, characterized in that, In step S4, the moisturizing and drying process involves setting the temperature to 45~60℃, the humidity to 55%~95%, and drying for 2.5~20 hours. Alternatively, the temperature in the constant temperature and humidity chamber can be set to 45~60℃, and the linear humidity range can be set to 99%~60%, with a drying time of 2.5~20 hours.

8. The preparation method according to claim 1, characterized in that, In step S4, the segmented moisturizing and drying process is as follows: the first segment temperature is set at 55~65℃, the linear humidity is set at 99-80%, and the drying time is 1.5~2.5h; the second segment temperature is set at 40~50℃, the linear humidity is set at 80-70%, and the drying time is 1.5~2.5h.

9. The preparation method according to claim 1, characterized in that, The segmented moisturizing and drying process is as follows: the first segment has a temperature of 40~50℃ and a linear humidity of 99-80%, and is dried for 1.5~2.5 hours; the second segment has a temperature of 55~65℃ and a linear humidity of 80-70%, and is dried for 1.5~2.5 hours.

10. The application of the resistant starch prepared by the preparation method according to any one of claims 1-9 in the preparation of functional foods.

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