Heat-stable starch microcrystals and their application and preparation of sweet potato vermicelli

Abstract

The invention discloses heat-stable starch microcrystals, which are characterized in that they are mainly prepared by the following steps: step one, extracting amylose from sweet potato starch; step two, mixing the amylose with water to form a suspension, and subjecting it to a pressure heat and cold storage cycle treatment, and then homogenizing and drying. Also, the application of heat-stable starch microcrystals and sweet potato vermicelli prepared by adding the heat-stable starch microcrystals. The heat-stable starch microcrystals of the invention have good thermal stability and have the effect of promoting starch aging, and can be added to starch gel-based foods to promote the formation of slowly digestible starch and resistant starch in starch gel-based foods.

Description

Technical Field

[0001] The invention relates to the field of starch processing, and more specifically to a thermally stable starch microcrystal and application thereof and sweet potato vermicelli prepared therefrom. Background Art

[0002] The existing methods for preparing starch microcrystals include acid hydrolysis, enzymatic hydrolysis, and mechanical methods. The acid hydrolysis method is currently commonly used. For example, in Zhu Biye's "The Mechanism of the Influence of Amylose Seeds on Starch Retrogradation", the amylose was gelatinized with high-pressure steam and refrigerated retrogradation combined with concentrated sulfuric acid hydrolysis to obtain starch seeds with small particle size and high crystallinity, but it has the disadvantages of poor thermal stability, long preparation time, and hidden dangers to food caused by acid addition. The enzymatic method for preparing starch microcrystals is mainly to directly use starch gelatinization and retrogradation followed by enzymatic hydrolysis. The starch microcrystals generated by this method are not of high purity and have large particles. Generally, acid hydrolysis or mechanical methods are used to reduce the particle size. For example, Gao Xin et al.'s "Preparation of Waxy Corn Starch Nanocrystals by Enzyme Pretreatment and Acid Hydrolysis and Its Characterization" uses glucose amylase combined with sulfuric acid to treat starch. The mechanical method reduces the particle size of the starch solution through high-pressure homogenization or ultrasound. Although the particle size is reduced, the crystallinity is reduced. As recorded in "Preparation of Sweet Potato Nanostarch by High-Pressure Homogenization and Its Characterization" by Hou Shuyao et al., the particle size of sweet potato starch was reduced from microns to nanometers after multiple high-pressure homogenization, but its crystalline structure was destroyed. Summary of the invention

[0003] One object of the present invention is to provide a thermally stable starch microcrystal, which first extracts amylose and then performs multiple cycles of autoclave and refrigeration to improve the thermal stability of the starch microcrystals, and then performs multiple homogenization to reduce the particle size. The starch microcrystals obtained by the present invention have a stable structure, high crystallinity, and a small particle size, and mechanical homogenization is more environmentally friendly and safe.

[0004] Another object of the present invention is to provide an application of heat-stable starch microcrystals in promoting the formation of slowly digestible starch and resistant starch in starch gel-based foods.

[0005] Another object of the present invention is to provide sweet potato vermicelli prepared by adding the heat-stable starch microcrystals.

[0006] In order to achieve the purpose and other advantages of the present invention, a heat-stable starch microcrystal is provided, which is mainly prepared by the following steps:

[0007] Step 1, extracting amylose from sweet potato starch;

[0008] Step 2: Mix the amylose and water to form a suspension, and perform a heat-pressing and cold-storage cycle treatment, and then homogenize and dry to obtain the product.

[0009] Preferably, the heat-stable starch microcrystals, in step 1, include: 1) mixing 100g of sweet potato starch with water to form a suspension with a mass fraction of 10-20%, stirring at 90-100°C until it becomes a transparent paste, taking it out, cooling it to room temperature, and then aging it at 4°C for 1-4d; 2) adding 6-8mL of α-high temperature amylase to the aged sweet potato starch, and performing enzymolysis at 90-100°C for 6-8h; 3) centrifuging the enzymolysis solution, taking the precipitate, washing it with distilled water, repeating the centrifugation and washing process 3-6 times, taking the precipitate, and obtaining retrograded sweet potato starch; 4) adding 4mol / L KOH solution to the retrograded sweet potato starch to fully dissolve the precipitate, then adding 6mol / L HCl solution to adjust the starch solution to neutrality, and then adding 2-5 times the volume of n-butanol of the KOH solution, mixing it thoroughly, centrifuging it, taking the precipitate, and repeating the n-butanol centrifugation and washing process 8-12 times to obtain the straight-chain starch.

[0010] Preferably, in the heat-stable starch microcrystals, in step 2, the amylose is mixed with water to form a suspension with a mass fraction of 15-20%, and after pre-gelatinization, the suspension is subjected to a cycle of autoclaving and refrigeration at 4°C for 3-8 times, and then the suspension is passed through a colloid mill for 8-20 times and freeze-dried to obtain the heat-stable starch microcrystals.

[0011] Preferably, for the heat-stable starch microcrystals, in step 2, the temperature of the autoclave treatment is 121° C., the pressure is 100 kPa, and the time is 10-30 min; and the refrigeration time at 4° C. is 12 to 24 h.

[0012] The present invention also provides an application of heat-stable starch microcrystals for promoting the formation of slowly digestible starch and resistant starch in starch gel-based foods.

[0013] The invention also provides a sweet potato vermicelli, to which the heat-stable starch microcrystals are added.

[0014] Preferably, the sweet potato vermicelli is mainly made of the following raw materials: 40-60 parts by weight of sweet potato starch, 3-12 parts by weight of whole sweet potato flour, 0.5-3 parts by weight of heat-stable starch microcrystals and 0.05-0.5 parts by weight of edible gum; wherein the edible gum is composed of konjac gum, carrageenan and xanthan gum in a weight ratio of 1:1:1.

[0015] Preferably, the sweet potato vermicelli is mainly prepared by the following steps:

[0016] Step A, taking 5 to 10 parts by weight of sweet potato starch, adding water to make a paste, and then stirring at 98 to 100° C. for 3 to 5 minutes to obtain a starch paste;

[0017] Step B, mixing sweet potato whole flour, heat-stable starch microcrystals, edible gum and remaining sweet potato starch according to the formula amount, adding the mixture into the starch paste, and kneading the mixture into a smooth dough;

[0018] Step C, placing the dough in an extruder for extrusion molding, and then subjecting the dough to ripening, cooling, aging and drying to obtain the product.

[0019] Preferably, in the sweet potato vermicelli, in step B, when the mixed raw materials are added to the starch paste, the temperature of the starch paste is 45-60°C.

[0020] Preferably, in the step C of the sweet potato vermicelli, the aging temperature is 0-6° C. and the aging time is 8-48 h.

[0021] The present invention has at least the following beneficial effects:

[0022] First, the present invention prepares heat-stable starch microcrystals by first extracting amylose from sweet potato starch, mixing the amylose with water into a suspension, and then subjecting the suspension to pressure heat and cold storage cycle treatment, homogenization and drying. Compared with the original sweet potato starch, the heat-stable starch microcrystals have a smaller particle size, a greatly improved crystallinity and thermal stability, and have the effect of promoting starch aging.

[0023] Second, the gelatinization temperature of the heat-stable starch microcrystals of the present invention is above 120° C., and can be added to starch gel-based foods to promote the formation of slowly digestible starch and resistant starch in the starch gel-based foods.

[0024] Third, the sweet potato vermicelli of the present invention has a high content of slowly digestible starch and resistant starch, has slow digestion characteristics, and has high nutritional value, good sensory quality, and is extremely edible. Other advantages, objectives, and features of the present invention will be partially reflected in the following description, and partly will be understood by those skilled in the art through research and practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is the SEM test result of sweet potato starch, sweet potato amylose and heat-stable starch crystallites;

[0026] Figure 2 This is the X-ray diffractometer test result diagram of sweet potato starch, sweet potato amylose and heat-stable starch microcrystals;

[0027] Figure 3 It is a differential scanning calorimeter test result diagram of sweet potato starch, sweet potato amylose and heat-stable starch microcrystals;

[0028] Figure 4 This is the FTIR infrared spectrum analysis test result diagram of sweet potato starch, sweet potato amylose and heat-stable starch microcrystals. DETAILED DESCRIPTION

[0029] The present invention is further described in detail below in conjunction with embodiments and drawings so that those skilled in the art can implement the invention with reference to the description.

[0030] It should be understood that the terms such as “having”, “including” and “comprising” used herein do not exclude the existence or addition of one or more other elements or combinations thereof.

[0031] It should be noted that the experimental methods described in the following embodiments are conventional methods unless otherwise specified, and the reagents and materials can be obtained from commercial channels unless otherwise specified.

[0032] Embodiment 1:

[0033] Preparation of sweet potato amylose (M): 100g sweet potato starch (purity>95%, the same below) was mixed with water to form a 10% (w / v) suspension, placed in a 90-100℃ water bath and stirred continuously for gelatinization, and the heating was stopped when the suspension became a transparent paste. After being taken out and gradually cooled to room temperature, it was placed in the refrigerator (4℃) for aging for 48h. The aged sweet potato starch was taken out, 7mL of α-high temperature amylase was added, and the heating was stopped after enzymolysis in a 95℃ water bath for 8h. After cooling to room temperature, centrifuged (8000rmp, 20min), the supernatant was poured out, and the precipitate was washed with distilled water. The centrifugal washing was repeated 4 times to obtain a precipitate. 4mol / LKOH solution was added to the precipitate to fully dissolve the precipitate, and then 6mol / L HCl solution was added until the starch solution was neutral. Then 2 times the volume of n-butanol (the amount of KOH added) was added and stirred and mixed thoroughly, and then a centrifuge was used for high-speed centrifugal washing 8 times to obtain sweet potato amylose.

[0034] Sweet potato amylose microcrystals (MJ): Prepare a 20% (w / v) suspension of sweet potato amylose with deionized water, stir evenly and place in a boiling water bath for pre-gelatinization for 30 minutes. Transfer to a 121°C autoclave and heat-treat for 10 minutes. After taking out, regenerate in a 4°C environment for 12 hours, and repeat the heat-treat / 4°C cycle for 3 times. Then, dilute the autoclaved sample by 1 time with distilled water, pass 8 times in a colloid mill at 200 MPa, and freeze-dry to obtain sweet potato amylose microcrystals, i.e., heat-stable starch microcrystals.

[0035] Embodiment 2:

[0036] Preparation of sweet potato amylose (M): 100g sweet potato starch (purity>95%, the same below) was mixed with water to form a 20% (w / v) suspension, placed in a 90-100℃ water bath and stirred continuously for gelatinization, and the heating was stopped when the suspension became a transparent paste. After being taken out and gradually cooled to room temperature, it was placed in the refrigerator (4℃) for aging for 96h. The aged sweet potato starch was taken out, 8mL of α-high temperature amylase was added, and the heating was stopped after enzymolysis in a 100℃ water bath for 6h. Cooled to room temperature, centrifuged (8000rmp, 20min), the supernatant was poured out, and the precipitate was washed with distilled water. The centrifugal washing was repeated 6 times to obtain a precipitate. 4mol / LKOH solution was added to the precipitate to fully dissolve the precipitate, and then 6mol / L HCl solution was added until the starch solution was neutral. Then 5 times the volume of n-butanol (the amount of KOH added) was added and stirred and mixed thoroughly, and then a centrifuge was used for high-speed centrifugal washing 12 times to obtain sweet potato amylose.

[0037] Sweet potato amylose microcrystals (MJ): Prepare a 15% (w / v) suspension of sweet potato amylose with deionized water, stir evenly and place in a boiling water bath for pre-gelatinization for 30 minutes. Transfer to a 121°C autoclave and heat-treat for 30 minutes. After taking out, regenerate in a 4°C environment for 18 hours, and repeat the heat-treat / 4°C cycle for 8 times. Then, dilute the autoclaved sample by 1 time with distilled water, pass through a colloid mill at 200 MPa for 20 times, and freeze-dry to obtain sweet potato amylose microcrystals, i.e., heat-stable starch microcrystals.

[0038] Embodiment 3:

[0039] Preparation of sweet potato amylose (M): Mix sweet potato starch with water to form a 15% (w / v) suspension, place it in a 90-100°C water bath and stir it continuously for gelatinization. Stop heating when the suspension becomes a transparent paste. Take it out and gradually cool it to room temperature, then place it in the refrigerator (4°C) for aging for 24 hours. Take out the aged sweet potato starch, add 6mL of α-high temperature amylase, and stop heating after enzymolysis in a 90°C water bath for 6 hours. Cool to room temperature, centrifuge (8000rmp, 20min), pour out the supernatant, wash the precipitate with distilled water, repeat the centrifugation washing 4 times to obtain a precipitate. Add 4mol / L KOH solution to the precipitate to fully dissolve the precipitate, and then add 6mol / L HCl solution until the starch solution is neutral. Add 4 times the volume of n-butanol (the amount of KOH added) and stir and mix thoroughly, then use a centrifuge to perform high-speed centrifugation washing 8 times to obtain sweet potato amylose.

[0040] Sweet potato amylose microcrystals (MJ): Prepare a 20% (w / v) suspension of sweet potato amylose with deionized water, stir evenly and place in a boiling water bath for pre-gelatinization for 30 minutes. Transfer to a 121°C autoclave and autoclave for 20 minutes. After taking out, regenerate in a 4°C environment for 24 hours, and repeat the autoclave / 4°C cycle for 6 times. Then, dilute the autoclaved sample by 1 time with distilled water, pass through a colloid mill at 200 MPa for 10 times, and freeze-dry to obtain sweet potato amylose microcrystals, i.e., heat-stable starch microcrystals.

[0041] Experimental Example 1:

[0042] The sweet potato starch and the sweet potato amylose and thermostable starch microcrystals prepared in Example 3 were characterized and analyzed by scanning electron microscopy (SEM), X-ray diffractometer (XRD) and differential scanning calorimeter (DSC). Figure 1 , Figure 2 and Figure 3 As shown. Among them, Figure 1 (a) is the SEM image of sweet potato starch. Figure 1 (b) is the SEM image of sweet potato amylose. Figure 1 (c) is the SEM image of sweet potato amylose microcrystals.

[0043] Depend on Figure 1 It can be seen that sweet potato starch is spherical and complete particles. The particles of amylose are destroyed by enzymatic extraction, and due to aging, the molecules aggregate and the particle size becomes larger. After multiple pressure heating / cooling cycles and colloid milling treatment, the prepared amylose microcrystals have reduced aggregation between amylose molecules, reduced average particle size, and more uniform particle size distribution, which is more conducive to the aging of amylose microcrystals in the later stage to promote gelatinized starch gel.

[0044] Depend on Figure 2 It can be seen that sweet potato starch has characteristic peaks at 15°, 17°, 18°, and 23°, which is a typical A-type crystal with a crystallinity of about 23%. The amylose extracted and the amylose microcrystals treated by hot / cold cycles and colloid milling all have peaks at 15°, 17°, and 24°, indicating that there is a certain difference between the crystallinity of amylose and amylose crystals after extraction and native starch, and the crystallinity of the extracted amylose is higher than that of native starch. Multiple hot / cold cycles and colloid milling treatments did not change the amylose crystal form, but further increased its crystallinity to 32.9%.

[0045] Depend on Figure 3It can be seen that within the measurement range of 20-120℃, the DSC measurement results show that the gelatinization temperature of sweet potato starch is 67.39℃ and ΔH is 11.61J / g. However, within the measurement range, the gelatinization temperature and ΔH of the prepared sweet potato amylose and microcrystals were not measured. This shows that the sample crystal structure is extremely stable within the measurement temperature range and is not easily destroyed by high temperature.

[0046] Experimental Example 2:

[0047] The sweet potato amylose and heat-stable starch microcrystals prepared in Example 3 were subjected to an experiment to promote sweet potato starch aging.

[0048] Mix sweet potato starch and water into a 20% (w / v) suspension, add the above sweet potato amylose or heat-stable starch microcrystals in a ratio of 0%, 1%, 3%, and 5%, vortex evenly, stir in a 95°C water bath for 30 minutes to gelatinize the sample, and cool to room temperature to obtain a sweet potato starch gel. The sweet potato starch gelatinized gel sample was placed in a 4°C refrigerator, and samples were taken at 0h, 10h, and 7d, respectively, to determine the moisture migration, and to perform FTIR infrared spectroscopy analysis and resistant starch and slowly digestible starch content determination (in vitro simulated digestion method). The results are as follows: Figure 4 , as shown in Table 1 and Table 2.

[0049] Depend on Figure 4 It can be seen that, at the same addition amount, the sample with added heat-stable starch microcrystals has a stronger ability to promote the migration of starch gel moisture to the surface during storage, indicating that amylose microcrystals have a stronger ability to promote short-term and long-term aging of starch gel.

[0050] Table 1 Results of promoting short-term and long-term aging of starch gel

[0051]

[0052] In Table 1, 1047 cm -1 / 1022cm -1 and 995cm -1 / 1022cm -1 They represent the short-range ordered structure and long-range ordered structure in the sample, respectively. As shown in Table 1, adding different proportions of amylose microcrystals will promote the formation of short-range ordered structure and long-range ordered structure in starch gel. The aging behavior of starch is the orderly rearrangement of disordered starch molecular chains. Therefore, the above results also show that heat-stable starch microcrystals have an effective effect in promoting the aging of starch gel.

[0053] Table 2 Resistant starch and slowly digestible starch content

[0054]

[0055] As shown in Table 2, after adding amylose microcrystals and storing, the content of resistant starch in the short term (10h) and the content of slowly digestible starch in the long term (7d) increased significantly. This shows that amylose microcrystals contribute to the short-term and long-term aging of starch gel.

[0056] Embodiment 4:

[0057] Sweet potato starch microcrystals prepared in Example 3 were used to prepare sweet potato vermicelli.

[0058] The raw materials of the sweet potato vermicelli are as follows: 40 parts by weight of sweet potato starch; 12 parts by weight of sweet potato whole flour; 0.5 parts by weight of sweet potato amylose microcrystals; and 0.05 parts by weight of edible gum; the edible gum comprises konjac gum: carrageenan: xanthan gum in a ratio of 1:1:1.

[0059] Processing method: Take 5 parts by weight of sweet potato starch, add water and stir evenly, and boil in water for 5 minutes to make a thick paste. Mix sweet potato whole powder, sweet potato amylose microcrystals, edible gum and the remaining sweet potato starch according to the raw material composition and add them to the thick paste, knead into a smooth dough, and then extrude it into shape. Put the extruded vermicelli in boiling water to fully mature it. After maturation, rinse with cold water, take it out, place it at 4°C for aging for 24 hours, and dry it.

[0060] Embodiment 5:

[0061] Sweet potato starch microcrystals prepared in Example 3 were used to prepare sweet potato vermicelli.

[0062] The raw materials of the sweet potato vermicelli are as follows: 45 parts by weight of sweet potato starch; 9 parts by weight of whole sweet potato; 1 part by weight of sweet potato amylose microcrystals; and 0.1 part by weight of edible gum; the edible gum comprises konjac gum: carrageenan: xanthan gum in a ratio of 1:1:1.

[0063] Processing method: Take 10 parts by weight of sweet potato starch, add water and stir evenly, and boil in water for 5 minutes to make a thick paste. Mix sweet potato whole powder, sweet potato amylose microcrystals, edible gum and the remaining sweet potato starch according to the raw material composition and add them to the thick paste, knead into a smooth dough, and then extrude it into shape. Put the extruded vermicelli in boiling water to fully mature it. After maturation, rinse with cold water, take it out, place it at 4°C for aging for 12 hours, and dry it.

[0064] Implementation 6:

[0065] Sweet potato starch microcrystals prepared in Example 3 were used to prepare sweet potato vermicelli.

[0066] The raw materials of the sweet potato vermicelli are as follows: 50 parts by weight of sweet potato starch; 3 parts by weight of sweet potato whole flour; 1.5 parts by weight of sweet potato amylose microcrystals; and 0.2 parts by weight of edible gum; the edible gum comprises konjac gum: carrageenan: xanthan gum in a ratio of 1:1:1.

[0067] Processing method: Take 5 parts by weight of sweet potato starch, add water and stir evenly, and boil in water for 5 minutes to make a thick paste. Mix sweet potato whole powder, sweet potato amylose microcrystals, edible gum and the remaining sweet potato starch according to the raw material composition and add them to the thick paste, knead into a smooth dough, and then extrude it into shape. Put the extruded vermicelli in boiling water to fully mature it. After maturation, rinse with cold water, take it out, place it at 4°C for aging for 48 hours, and dry it.

[0068] Implementation 7:

[0069] Sweet potato starch microcrystals prepared in Example 3 were used to prepare sweet potato vermicelli.

[0070] The raw materials of the sweet potato vermicelli are as follows: 50 parts by weight of sweet potato starch; 3 parts by weight of sweet potato whole flour; 2 parts by weight of sweet potato amylose microcrystals; and 0.3 parts by weight of edible gum; the edible gum comprises konjac gum: carrageenan: xanthan gum in a ratio of 1:1:1.

[0071] Processing method: Take 10 parts by weight of sweet potato starch, add water and stir evenly, and boil in water for 5 minutes to make a thick paste. Mix sweet potato whole powder, sweet potato amylose microcrystals, edible gum and the remaining sweet potato starch according to the raw material composition and add them to the thick paste, knead into a smooth dough, and then extrude it into shape. Put the extruded vermicelli in boiling water to fully mature it. After maturation, rinse with cold water, take it out, place it at 4°C for aging for 36 hours, and dry it.

[0072] Experimental Example 3:

[0073] Take the sweet potato vermicelli prepared in Examples 4 to 6, grind it and pass it through a 100-mesh sieve for later use. Weigh 10 mg of the sample, add 8 mL of distilled water and boil it in a water bath for 20 min to fully gelatinize the sample. Adjust the pH to 2-3, bring it to room temperature, add pepsin (2500 U), shake it in a water bath at 37°C for 20 min, adjust the pH to about 7.4, add α-amylase (170 U) and amyloglucosidase (21 U), and continue shaking it in a water bath for 150 min. Take samples at 20 and 120 min, and determine the glucose content by DNS method.

[0074] Calculate SDS and RS. The formula is as follows:

[0075] RDS(%)=(G 20 -FG)×0.9×100

[0076] SDS(%)=(G 120 -G 20 )×0.9×100

[0077] RS(%)=TS-RDS-SDS

[0078] Where G 20 Refers to the glucose content of the 20min sample, G120 refers to the glucose content of the sample at 120 min, TS refers to the total starch content, and FG refers to the glucose content of the sample before enzymatic hydrolysis. The results are shown in Table 3.

[0079] Table 3 Resistant starch and slowly digestible starch content in sweet potato vermicelli

[0080] Example No. 4 5 6 7 Resistant starch content% 10.75 11.09 13.45 14.65 Slowly digestible starch content% 22.15 25.57 25.96 25.28

[0081] As shown in Table 3, the content of resistant starch in sweet potato vermicelli increases with the increase of the added amount of sweet potato amylose microcrystals, and the effect of sweet potato amylose microcrystals on promoting starch aging increases with the increase of the added amount.

[0082] Experimental Example 4:

[0083] The sweet potato vermicelli prepared in Examples 4 to 6 and 10% resistant starch vermicelli were taken for sensory evaluation. Among them, the raw material composition of 10% resistant starch vermicelli: 35 parts by weight of sweet potato starch; 10 parts by weight of sweet potato whole powder; 5 parts by weight of corn resistant starch; 0.05 parts by weight of edible gum; the edible gum is composed of konjac gum: carrageenan: xanthan gum = 1:1:1. Processing method: Take 5 parts by weight of sweet potato starch, add water and stir evenly, boil in water bath for 5 minutes, and make a glutinous paste. According to the raw material composition, the sweet potato whole powder, corn resistant starch, edible gum and the remaining sweet potato starch are mixed and added to the glutinous paste, kneaded into a smooth dough, and then extruded and formed, and the extruded vermicelli is placed in boiling water to fully mature. After maturation, take it out after cooling water, place it at 4°C for aging for 24 hours, and dry it. The sensory evaluation standards are shown in Table 4 and the evaluation results are shown in Table 5.

[0084] Table 4 Sensory evaluation standards

[0085]

[0086]

[0087] Table 5 Sensory evaluation results

[0088] Color Organizational form Taste texture Smell and taste Total score Example 4 12 13 21 17 22 86 Example 5 13 13 22 17 23 89 Example 6 13 13 20 15 23 85 Example 7 12 13 20 16 22 87 10% Resistant Starch Noodles 12 13 15 11 23 74

[0089] As can be seen from Table 5, the taste, texture and total score of the sweet potato vermicelli prepared by the method of the present invention are significantly higher than those of the vermicelli with 10% resistant starch, which shows that the sweet potato vermicelli of the present invention can maintain the excellent sensory quality of the sweet potato vermicelli while increasing the content of resistant starch in the vermicelli.

[0090] The number of equipment and processing scale described here are used to simplify the description of the present invention. The application, modification and variation of the heat-stable starch microcrystals and the application and preparation of sweet potato vermicelli of the present invention are obvious to those skilled in the art.

[0091] Although the embodiments of the present invention have been disclosed as above, they are not limited to the applications listed in the specification and the implementation modes, and they can be fully applied to various fields suitable for the present invention. For those familiar with the art, additional modifications can be easily implemented. Therefore, without departing from the general concept defined by the claims and the scope of equivalents, the present invention is not limited to the specific details and the illustrations shown and described herein.

Claims

1. Heat-stable starch microcrystals, characterized in that: It is mainly prepared by the following steps: Step 1, extracting amylose from sweet potato starch; Step 2: Mix the amylose and water to form a suspension, and perform a heat-pressing and cold-storage cycle treatment, and then homogenize and dry to obtain; Step 1 comprises: 1) mixing 100g of sweet potato starch with water to form a suspension with a mass fraction of 10-20%, stirring at 90-100°C until it becomes a transparent paste, taking it out, cooling it to room temperature, and then transferring it to aging at 4°C for 1-4 days; 2) adding 6-8 mL of α-high temperature amylase to the aged sweet potato starch, and performing enzymolysis at 90-100°C for 6-8 hours; 3) centrifuging the enzymolysis solution, taking the precipitate, washing it with distilled water, repeating the centrifugation and washing process 3-6 times, taking the precipitate, and obtaining retrograded sweet potato starch; 4) adding 4 mol / L KOH solution to the retrograded sweet potato starch to fully dissolve the precipitate, then adding 6 mol / L HCl solution to adjust the starch solution to neutrality, and then adding 2-5 times the volume of n-butanol of the KOH solution, mixing it thoroughly, centrifuging it, taking the precipitate, and repeating the n-butanol centrifugation and washing process 8-12 times to obtain the straight-chain starch; In step 2, the amylose is mixed with water to form a suspension with a mass fraction of 15-20%, and the suspension is subjected to a cycle of autoclaving and refrigeration at 4° C. for 3-8 times, and then passed through a colloid mill for 8-20 times, and freeze-dried to obtain the heat-stable starch microcrystals.

2. The use of the heat-stable starch microcrystals as claimed in claim 1, characterized in that: Used to promote the formation of slowly digestible starch and resistant starch in starch gel-based foods.

3. Sweet potato vermicelli, characterized in that: The heat-stable starch microcrystals as claimed in claim 1 are added.

4. The sweet potato vermicelli as claimed in claim 3, characterized in that The invention is mainly prepared from the following raw materials: 40-60 parts by weight of sweet potato starch, 3-12 parts by weight of whole sweet potato flour, 0.5-3 parts by weight of heat-stable starch microcrystals and 0.05-0.5 parts by weight of edible gum; wherein the edible gum is composed of konjac gum, carrageenan and xanthan gum in a weight ratio of 1:1:

1.

5. The sweet potato vermicelli as claimed in claim 4, characterized in that It is mainly prepared by the following steps: Step A, taking 5-10 parts by weight of sweet potato starch, adding water to make a paste, and then stirring at 98-100° C. for 3-5 min to obtain a starch paste; Step B, mixing sweet potato whole flour, heat-stable starch microcrystals, edible gum and remaining sweet potato starch according to the formula amount, adding the mixture into the starch paste, and kneading the mixture into a smooth dough; Step C, placing the dough in an extruder for extrusion molding, and then subjecting the dough to ripening, cooling, aging and drying to obtain the product.

6. The sweet potato vermicelli as claimed in claim 5, characterized in that In step B, when the mixed raw materials are added to the starch paste, the temperature of the starch paste is 45-60°C.

7. The sweet potato vermicelli as claimed in claim 5, characterized in that In step C, the aging temperature is 0-6 °C and the aging time is 8-48 h.

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