Preparation method and device of pea resistant starch

Abstract

The invention belongs to the technical field of functional food processing, and provides a preparation method and device of pea resistant starch. According to the preparation method, the pea resistant starch is prepared by adopting a technical scheme of synergistic modification of pullulanase debranching and autoclaving treatment. The specific process comprises the following steps: weighing pea starch, dispersing the pea starch in a buffer solution to prepare starch milk, gelatinizing the starch milk, adding enzyme to carry out gradient enzymolysis, washing, aging, drying and sieving to obtain a finished product. The process not only solves the core problems of low RS content, high GI value and poor thermal stability in the prior art, but also provides a scientific basis and a process normal form for high-valued utilization of pea starch through analysis of a structure-function association mechanism, and has significant application value in the fields of diabetes-friendly food, low-GI staple food development and the like.

Description

A method and apparatus for preparing pea resistant starch Technical Field

[0001] This invention belongs to the field of functional food processing technology, and specifically relates to a method and apparatus for preparing resistant starch from peas. Background Technology

[0002] In the field of pea starch modification research, existing technologies have long faced three core challenges: First, the increase in resistant starch (RS) content is limited. Traditional enzymatic hydrolysis or pressure heat treatment processes are difficult to break through the bottleneck of 40-53% RS content in natural pea starch, and are often accompanied by an excessively high proportion of rapidly digestible starch (RDS), resulting in a high glycemic index (GI) of the product, making it difficult to meet the needs of special populations such as diabetics and obese individuals for low-GI foods. Second, the crystal structure is not precisely controlled. Natural pea starch is mainly C-type crystal, with poor thermal stability (gelatinization temperature of about 60-70℃), and is prone to retrogradation during processing, affecting the texture and shelf life of food. Third, the structure-function correlation is weak. Traditional modification methods focus on optimizing a single index, making it difficult to achieve synergistic improvement of multiple dimensions such as RS content, thermal stability, and rheological properties, resulting in poor performance in processing properties such as solubility and swelling power, which limits its widespread application in low-GI staple foods, functional foods, and other fields.

[0003] Specifically, in existing technologies, simple enzymatic debranching easily leads to excessive degradation of starch chains, resulting in unstable RS content and high RDS. While simple pressure heating can promote recrystallization, it often results in excessive crystallinity, leading to high product hardness and poor taste. Traditional synergistic processes suffer from problems such as coarse parameter control (e.g., no gradient design for enzymatic hydrolysis time) and ambiguous structural characterization (e.g., unclear crystal type transformation mechanism), making it difficult to achieve targeted conversion from "high-GI natural starch" to "low-GI resistant starch." Furthermore, existing technologies lack sufficient research on the correlation mechanism between amylose enrichment and resistant structure formation, leading to a mismatch between the increase in amylose content (approximately 32% in natural starch) and RS increase, often accompanied by derivative problems such as uneven molecular weight distribution and poor thermal stability. In addition, the processing often requires the use of various instruments and equipment, such as stirring tanks, water baths, reaction vessels, and washing tanks. Personnel need to constantly transfer materials between different devices, severely impacting production efficiency and increasing labor intensity and processing time. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention proposes a method for preparing resistant pea starch. Employing a "pullulanase enzymatic debranching-pressure heat treatment synergistic modification" technique, it not only solves the core problems of low RS content, high GI value, and poor thermal stability in existing technologies, but also provides a scientific basis and technological paradigm for the high-value utilization of pea starch through structure-function correlation mechanism analysis. This method has significant application value in areas such as diabetes-friendly foods and the development of low-GI staple foods.

[0005] The technical solution of the present invention is as follows: The present invention proposes a method for preparing pea resistant starch, including the following steps: (1) weigh pea starch, disperse it in a buffer solution with a pH of 5.2, and prepare a starch milk with a concentration of 10%; (2) gelatinization: place the starch milk in a 90°C environment (such as a water bath) and stir to gelatinize for 25-30 min, then take it out and cool it to 55°C, wherein the gelatinization process is carried out by stirring with a heatable stirring component; (3) enzymatic hydrolysis: add pullulanase and continuously stir to debranch the starch in a 55°C environment (such as a water bath), and take it out after enzymatic hydrolysis for 18-20 h, and continuously stir and press-heat at 121°C for 20 min; (4) centrifugation: wash three times and centrifuge to promote the precipitation of amylose, remove buffer salts, small molecule glucose and free short amylose in starch, and make the starch molecular chain distribution more uniform; and age and revert at 4°C for 24 hours. After h, it was dried at 45℃ to constant weight, ground and passed through a 120-mesh sieve to obtain pea resistant starch prepared by pressure heating-assisted enzymatic hydrolysis.

[0006] Preferably, in (1), the buffer solution is a 0.1 mol sodium acetate buffer solution with a pH of 5.2.

[0007] Preferably, in (3), the pullulanase activity is 4000 NPUN / g, and the mass ratio of pea starch to pullulanase is 100:(1.0-2.0).

[0008] Preferably, in (3), the mass-to-volume ratio of pea starch to pullulanase is 100:1.5.

[0009] Preferably, in (3), the enzymatic hydrolysis time is 18 h.

[0010] Preferably, the present invention also provides an apparatus for preparing pea resistant starch, for implementing the above-mentioned preparation method, comprising a reaction vessel consisting of an upper vessel and a lower vessel, and a stirring assembly fixedly connected to the reaction vessel; the inner side wall of the upper vessel is provided with an axially spaced liquid inlet heat exchange ring and a liquid outlet heat exchange ring, the upper vessel is provided with a liquid inlet port communicating with the inner cavity of the liquid inlet heat exchange ring and a liquid outlet port communicating with the inner cavity of the liquid outlet heat exchange ring, the stirring assembly includes a drive motor and a stirring rod extending into the inner cavity of the reaction vessel, the stirring rod is provided with a stirring branch tube fixedly connected thereto, the top end of the stirring branch tube is provided with a liquid inlet port and a liquid outlet port arranged on both sides of the stirring rod, the liquid inlet port communicating with the inner cavity of the liquid inlet heat exchange ring, and the liquid outlet port communicating with the inner cavity of the liquid outlet heat exchange ring.

[0011] Preferably, the liquid inlet heat exchange ring includes a liquid inlet ring rail fixedly disposed on the inner side wall of the upper vessel body and a liquid inlet ring plate movably and sealingly connected to the liquid inlet ring rail. The liquid inlet port is fixedly connected to the liquid inlet ring plate and passes through the liquid inlet ring plate to communicate with the inner cavity of the liquid inlet heat exchange ring. The liquid outlet heat exchange ring includes a liquid outlet ring rail fixedly disposed on the inner side wall of the upper vessel body and a liquid outlet ring plate movably and sealingly connected to the liquid outlet ring rail. The liquid outlet port is fixedly connected to the liquid outlet ring plate and passes through the liquid outlet ring plate to communicate with the inner cavity of the liquid outlet heat exchange ring.

[0012] Preferably, both the inlet ring rail and the outlet ring rail are provided with guide ring grooves on their sidewalls that are adapted to the stirring branch tube.

[0013] Preferably, at least one set of sealing rings is provided between the liquid inlet ring rail and the liquid inlet ring plate, and at least one set of sealing rings is also provided between the liquid outlet ring rail and the liquid outlet ring plate.

[0014] Preferably, the stirring tube has a pear-shaped profile that is narrower at the top and wider at the bottom, and the stirring tube is arranged in several groups and is evenly spaced along the circumferential direction with the stirring rod axis as the center.

[0015] Preferably, the top of the upper vessel is provided with a raw material inlet, a buffer solution inlet, an enzyme solution inlet, and a washing liquid inlet communicating with its inner cavity. The top of the upper vessel is also provided with a pressure gauge and a pressure relief valve communicating with its inner cavity. The bottom of the lower vessel is provided with a discharge port communicating with its inner cavity and a discharge valve fixedly connected thereto.

[0016] Preferably, the outer wall of the lower vessel is provided with a heat exchange jacket fixedly connected thereto, the heat exchange jacket is provided with a heat exchange inlet and a heat exchange outlet communicating with its inner cavity, and the lower vessel is also provided with a temperature monitoring unit that penetrates the heat exchange jacket and the side wall of the lower vessel and extends into the inner cavity of the lower vessel.

[0017] The present invention has the following advantages and effects compared with the prior art: (1) The method uses sodium acetate buffer solution to replace the traditional HCl / NaOH adjustment system, which effectively maintains the stable acidic environment required for starch hydrolysis and enzymatic hydrolysis, reduces pH fluctuations and shortens the acid-base adjustment time; through precise enzymatic hydrolysis time control, the content of resistant starch (RS) reaches a breakthrough of 72.41%, the content of rapidly digestible starch (RDS) is reduced to 2.30%, and the predicted glycemic index (pGI) is as low as 46.19, which fully meets the low GI food standard; the innovative "pressing and heating before aging" process sequence significantly improves the anti-digestion characteristics of starch and reduces the RDS content compared with the traditional "aging before pressing and heating" process. In the HEW18 and HEW24 tests, after 18 hours of reaction, the RDS content was less than 6%, and the total amount of RS and SDS reached more than 96%. Among them, SDS has both continuous energy supply and low glycemic index characteristics, so that the prepared RSⅢ type pea starch can effectively build a glycemic buffer barrier while providing the energy required by the body, avoiding a sudden rise in blood sugar, and is suitable for diabetes-friendly and sports nutrition, etc. Quasi-nutritional scenario; (2) This invention uses a special equipment integrating gelatinization-enzymatic hydrolysis-pressure heating functions, and achieves efficient synergy of processes through the synergistic effect of stirring and heating: In the gelatinization stage, the starch granules are fully heated and absorb water to expand through the heatable stirring component, resulting in more complete gelatinization and exposing more enzyme cleavage sites in the molecular chain, thereby improving the efficiency of enzymatic hydrolysis; In the enzymatic hydrolysis stage, the cooling time is shortened by simultaneously cooling to 55℃ inside and outside; In the pressure heating stage, by combining stirring and pressure heating synergistic treatment, not only is the uniformity of solution heating improved, but also the linear starch molecular structure is directionally regulated (from C type to B type) through continuous stirring and pressure heating process, which significantly enhances the thermal stability of starch (gelatinization temperature is increased to 98.3-98.7℃), and at the same time achieves high accumulation of SDS and RS content; (3) This invention optimizes the structure in multiple dimensions (such as reducing the molecular weight from 23237kDa to 5.84kDa, promoting the rearrangement of the double helix structure of starch molecules, improving the double helix degree and average chain length), and simultaneously improves the solubility (37.06%) and reduces the swelling force (3.59%). (g / g), achieving a balance between high RS content and good processing performance. Attached Figure Description

[0018] Figure 1 shows scanning electron microscopy (SEM) and polarized light microscopy (PLM) images of natural pea starch and resistant pea starch; Figure 2 shows the XRD patterns of natural pea starch and resistant pea starch; Figure 3 shows the Fourier transform infrared (FTIR) patterns of natural pea starch and resistant pea starch; Figure 4 shows the SAXS patterns of natural pea starch and resistant pea starch; Figure 5 shows the DSC patterns of natural pea starch and resistant pea starch; Figure 6 shows the thermogravimetric analysis (TGA) and differential thermogravimetric analysis (DTG) patterns of natural pea starch and resistant pea starch; Figure 7 shows the chain length distribution of natural pea starch and resistant pea starch; Figure 8 shows the natural pea starch and resistant pea starch. Figure 9 shows the rheological properties of natural pea starch and resistant pea starch; Figure 10 shows the solubility and swelling force of natural pea starch and resistant pea starch; Figure 11 is a schematic diagram of the preparation device in Example 3 of the present invention; Figure 12 is another schematic diagram of the preparation device in Example 3 of the present invention; Figure 13 is a partially cutaway schematic diagram of the preparation device in Example 3 of the present invention; Figure 14 is an enlarged schematic diagram of position A in Figure 13; Figure 15 is a partial schematic diagram of the preparation device in Example 3 of the present invention; Figure 16 is an enlarged schematic diagram of position B in Figure 15. Detailed Implementation

[0019] To enable those skilled in the art to better understand the present invention, specific embodiments will now be described in further detail. It should be understood that the specific embodiments described herein are for illustrative and explanatory purposes only and are not intended to limit the scope of the invention.

[0020] Example 1: Preparation process (1) Weigh 100 g of pea starch and disperse it in 0.1 mol of sodium acetate buffer solution with a pH of 5.2 to prepare a starch milk with a concentration of 10%; (2) Gelatinization: Place the starch milk in a water bath and stir and gelatinize it at 90℃ for 25-30 min, then cool it to 55℃; (3) Enzymatic hydrolysis: Add 1.5 g pullulanase (4000 NPUN / g) and stir continuously in a 55℃ water bath to debranch it. After enzymatic hydrolysis for 0 h, 6 h, 12 h, 18 h, 24 h, 30 h, and 36 h, cool it to room temperature and then press-heat it at 121℃ for 20 min; (4) Centrifugation: Wash three times and centrifuge to promote the precipitation of amylose, remove buffer salts, small molecule glucose and free short amylose in starch, and make the starch molecular chain distribution more uniform; aging and retrogradation at 4℃ for 24 minutes After h, it was dried at 45℃ to constant weight, ground, and passed through a 120-mesh sieve to obtain pea resistant starch prepared by pressure-heat assisted enzymatic hydrolysis. The starches with enzymatic hydrolysis times of 0 h, 6 h, 12 h, 18 h, 24 h, 30 h, and 36 h were designated as HEW0, HEW6, HEW12, HEW18, HEW24, HEW30, and HEW36, respectively.

[0021] In the preparation of the above samples (including HEW18), steps (1)-(3) were all performed using the special equipment described in Example 3. In contrast, although the preparation of the HEW18-W sample in Example 2 followed the same steps, the special equipment was not used, and the stirring operation was omitted in the key pressure heat treatment process. This is the core difference between the two process paths.

[0022] Example 2: Detection Indicators and Data Analysis 2.1 Analysis of Starch Granule Characterization Results The changes in pea starch granules before and after pullulanase and pressure-heat modification were observed using polarized light microscopy (PLM) and scanning electron microscopy (SEM) as shown in Figure 1. In current studies, the intensity of the "Maltese cross" at the center of starch granules under PLM is commonly used to evaluate the degree of starch gelatinization. Observing Figure 1 (an), it can be found that the "Maltese cross" appeared in the HEW0 group after polarization (Figure 1h), while the "Maltese cross" disappeared in the modified HEW6-HEW36 groups after polarization, and the starch outline was more blurred (Figure 1in), indicating that the crystalline and semi-crystalline structures of the gelatinized starch were destroyed, resulting in disordered starch chains inside the granules and thus loss of birefringence. The changes in the shape, size, pores and other microstructures of starch granules were observed through SEM images. Untreated natural pea starch granules (Figure 1o) are mostly smooth-surfaced, elliptical or spherical granules of varying sizes, with clear boundaries and no obvious damage. After enzymatic debranching, pressure heating, and recrystallization, the surface and shape of the starch granules in the HEW6-HEW36 group (pu in Figure 1) changed significantly. After 6-12 hours of enzymatic hydrolysis (pq in Figure 1), the surface of the pea starch began to be damaged, losing its luster and showing small pits and depressions. After 18 hours of enzymatic hydrolysis (ru in Figure 1), the surface of the starch granules became rough with more irregular pores, and large granules broke down into granules of varying sizes. The longer the hydrolysis time, the more small granules appeared. This demonstrates that pullulanase and pressure heating treatment have a modifying effect on pea starch, and the degree of damage to the surface structure of pea starch is related to the debranching time.

[0023] 2.2 X-ray diffraction (XRD) results analysis Table 1 Effect of enzymatic hydrolysis-pressure heat treatment on the crystal structure of pea starch

[0024] Note: Different lowercase letters in each column indicate significant differences (p<0.05) between different sample groups. The data in the tables of this invention are all subject to this note.

[0025] X-ray diffraction (XRD) was used to determine the crystal structure of starch samples. Figure 2 shows the XRD patterns of resistant pea starch before and after modification. HEW0 exhibits distinct diffraction peaks near 15°, 17°, and 23° at the 2θ angle, indicating that untreated pea starch has a C-type crystal structure. This result is consistent with previous reports of a C-type crystal structure in pea starch. After pullulanase and pressure heating modification, the diffraction peak at 23° at the 2θ angle disappeared for starch crystals with different enzymatic debranching times, while new diffraction peaks appeared at 5° and 24°, with a weakened peak intensity at 15°, indicating that the modified starch crystal form changed from C-type to B-type. This may be because enzymatic hydrolysis and shearing of the branched chains increased the main chain length, thereby increasing the amylose content and making the starch more easily converted to B-type crystals. The change in starch crystal form indicates that the original crystal structure of starch granules was disrupted, and the starch obtained after enzymatic hydrolysis and pressure heating tends to exhibit a B-type crystal structure.

[0026] As shown in Table 1, the relative crystallinity of starch in each group showed a trend of first decreasing and then slightly increasing with the extension of enzymatic hydrolysis time. Within 0-18 h of enzymatic hydrolysis, the relative crystallinity of each group continuously decreased from 0 h (21.00%), reaching its lowest value (18.03%) at 18 h, and then slightly increased to 20.03% at 36 h. This trend indicates that in the early stage of enzymatic hydrolysis, amylase preferentially acts on the crystalline regions of the sample, destroying the ordered crystal structure through hydrolysis, resulting in a significant decrease in crystallinity. This is consistent with the result that crystallinity decreases with increasing amylose content. The relative crystallinity did not return to its initial level after the initial increase. This may be because in the later stage of enzymatic hydrolysis, a large amount of amorphous regions in the sample were hydrolyzed, and the remaining crystalline regions rearranged to form a more orderly crystal structure. However, since the crystalline regions were irreversibly damaged in the early stage of enzymatic hydrolysis, the crystallinity could not be restored to the un-enzymatically hydrolyzed state.

[0027] 2.3 Fourier Transform Infrared Spectroscopy (FTIR) Results Table 2 Effects of Enzymatic Hydrolysis-Pressure Heating Treatment on the Molecular Order and Double Helix Degree of Pea Starch

[0028] FTIR spectra can be used to evaluate the double helix structure, functional group changes, hydrogen bonds, and short-range ordered structure of starch molecules. The FTIR spectra of pea starch and its modified forms are shown in Figure 3. (3300 cm⁻¹) -1 The peak value at 3300 cm⁻¹ is related to the tensile vibration of OH; both the pre- and post-modification sample groups are at 3300 cm⁻¹. -1 There is an absorption peak nearby; after modification, the peak value is reduced from 3308 cm⁻¹. -1 Moved to 3280 cm -1The synergistic effect of pullulanase hydrolysis and pressure heating disrupts the original hydrogen bond network structure of starch, releasing strongly associated hydroxyl groups and forming a relatively loose hydrogen bond system. The shortened molecular chains are more likely to form weak hydrogen bonds with water molecules or adjacent molecules, leading to a decrease in the stretching vibration frequency of OH bonds and a shift of the absorption peak to lower wavenumbers (redshift). FTIR at 1047 cm⁻¹ -1 and 1022 cm -1 The peak values ​​at R are related to the crystalline and amorphous structures of starch, respectively. 1047 / 1022 and R 995 / 1022 The changes in the values ​​are related to alterations in the short-range ordered structure and double helix structure of starch molecules. As shown in Table 2, the HEW group showed values ​​at 1047 / 1022 cm⁻¹. -1 and 1022 / 995 cm -1 The ratios at the locations were 0.71 and 0.77, respectively. After modification, the HEW6-36 group showed a ratio of 1047 / 1022 cm⁻¹. -1 The ratio at this location showed a trend of first decreasing and then increasing, and was lower than that of the HEW group; 1022 / 995 cm -1 The ratio at the [specific location] showed a trend of first increasing and then decreasing, and was consistently higher than that of the HEW group; at 18 h of enzymatic hydrolysis, the ratio was 1047 / 1022 cm⁻¹. -1 and 1022 / 995 cm -1 The values ​​reached a minimum (0.65) and a maximum (0.82) at the respective locations. The results indicate that, compared to the HEW group, the modified starch exhibited a reduction in short-range ordered structures and an increase in amorphous regions. Pullulanase hydrolysis and pressure heating treatment disrupted some of the ordered structures in natural starch, thus reducing its degree of order.

[0029] 2.4 Small-angle X-ray scattering (SAXS) analysis Table 3 Effect of enzymatic hydrolysis-pressure heat treatment on the fractal dimension of pea starch

[0030] The electron density difference between the ordered crystalline regions and the disordered amorphous regions of starch molecules generates a significant scattering signal, forming a characteristic "scattering peak." The fractal dimension value is positively correlated with the density of the sample. The mass fractal dimension value (0 < α < 3) reflects the density of the sample; the closer the value is to 0, the looser the sample. The surface fractal dimension value (3 < α < 4) reflects the smoothness and roughness of the sample; the closer the value is to 3, the smoother the sample. Table 3 shows that the α value of the HEW group starch is 2.83, and the α values ​​of all sample groups are between 2 and 3, indicating a significant mass fractal dimension. After pullulanase and pressure-heat modification treatment, the α values ​​of the HEW6-36 groups all decreased, indicating that the modified starch samples were looser and less dense than the original starch. The decrease in α value may be due to the reduction of the ordered structure caused by enzymatic hydrolysis and thermal expansion of the starch granules. The scattering peak of starch is related to the thickness (d) of the half-lamellae layer, as shown in Figure 4. The HEW group has a peak at 0.07 nm. -1 Typical scattering peaks appeared at the scattering peaks, while the scattering peaks of HEW6-HEW36 starch tended to flatten and almost disappeared, indicating that it did not have a distinct semi-lamellae layer structure. This may be because after pullulanase and pressure heat treatment, amylose rearranged to form a new layered structure during retrogradation, reducing the molecular order structure and thus causing the starch scattering peaks to disappear.

[0031] 2.5 Analysis of Thermodynamic Properties (DSC) Table 4 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on Thermodynamic Properties of Pea Starch

[0032] The thermodynamic properties of starch can be determined using differential scanning calorimetry (DSC). The thermodynamic properties of natural pea starch and starch treated with enzymatic hydrolysis and pressure heat were compared using DSC. The initial gelatinization temperature (T0) and peak temperature (T2) of the starch before and after modification were also measured. P ), termination temperature (T) C Gelatinization temperature range (∆T=T) C The peak temperature (ΔT) and gelatinization enthalpy (ΔH) of the HEW6-36 group are shown in Figure 4 and Table 5. With increasing enzymatic hydrolysis time, the peak temperature, ΔT, and gelatinization enthalpy of the HEW6-36 group all showed a trend of first increasing and then decreasing. Furthermore, at 18 hours of enzymatic hydrolysis, T... PThe highest values ​​for ∆T and ∆H were 98.69℃, 3.55℃, and 0.018 J / g, respectively. The change in starch ∆T is related to the crystalline regions within the granules; the more microcrystals in the crystalline regions, the larger the ∆T. The ∆T of the HEW6-36 group (1.95-3.55℃) was significantly lower than that of the HEW0 group (24.15℃), which is consistent with the trend of crystallinity changes in pea starch before and after modification. Gelatinization temperature reflects the stability of the starch crystal structure. The peak temperature of the HEW0 group (69.86℃) was significantly lower than that of the HEW6-36 group (98.30-98.69℃). This indicates that the modified pea starch requires higher temperatures and heat for gelatinization. This may be because the starch undergoes debranching and pressure heating after enzymatic hydrolysis and debranching, producing a large amount of amylose, forming a new double helix structure, which enhances the thermal stability of the starch. The starch requires more energy to break the intermolecular bonds, hydrogen bonds, and other intermolecular forces within the crystalline regions.

[0033] 2.6 Thermogravimetric Analysis As shown in Figure 6-a, the thermogravimetric process of starch can be roughly divided into three stages, with the second stage exhibiting the fastest mass loss rate. The first mass loss occurs within the 70-140℃ range (Figure 6-a, b), due to the loss of free water from starch granules caused by heat, resulting in the first weight loss peak. Observing Figure b, it can be seen that the water loss rate of the modified HEW6-36 group is relatively gradual compared to the HEW0 group. The second mass loss occurs within the 200-400℃ range (Figure 6-a, c), due to the breakage of the starch molecule's main chain bonds, resulting in the second weight loss peak. The third mass loss occurs within the 500-800℃ range (Figure 6-a), where the starch mass loss rate tends to level off, and the starch and its intermediate products completely decompose, producing ash and low molecular weight substances.

[0034] 2.7 Analysis of Chain Length Distribution Results Table 5 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on Chain Length Distribution of Pea Starch

[0035] Based on the degree of polymerization (DP), amylopectin chains can be classified into A chains (DP 6–12), B1 chains (DP 13–24), B2 chains (DP 25–36), and B3 chains (DP>37). The chain length distribution of pea starch before and after modification is shown in Figure 7 and Table 5. As shown in Figure 7, the proportions of A, B1, B2, and B3 chains in the HEW0 group were 24.22%, 45.33%, 15.40%, and 15.05%, respectively, which is typical of pea starch. Short chains (A) and medium chains (B1) are the dominant chains in the HEW0-36 group. Compared with the HEW0 group, the proportions of A and B1 chains in the HEW6-36 group were significantly reduced (p<0.05), while the proportions of medium and long chains (B2+B3) were significantly increased (p<0.05). The changes in the crystalline region of amylopectin are related to the content of A-chain and B1-chain, as shown in Figure 7. Compared with the HEW0 group, the content of A-chain and B1-chain in the modified sample group decreased, which is consistent with the trend of decreasing crystallinity with increasing enzymatic hydrolysis time. B2 and B3 chains can form longer double helices. With increasing enzymatic hydrolysis time, the proportion of medium- and long chains (B2+B3) increases, thereby increasing the content of double helix structures in the modified sample group, requiring a higher temperature for thermal dissociation. As shown in Table 5, the average chain length (CL) of the modified sample group increased from 22.34 to 24.99 compared with the HEW0 group, while the branching degree (DB) decreased from 4.48 to 4.00. This indicates that the average chain length of amylopectin chains is positively correlated with enzymatic hydrolysis time and amylose content, while the branching degree is negatively correlated with enzymatic hydrolysis time and amylose content.

[0036] 2.8 Molecular Weight Results Analysis Table 6 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on the Molecular Weight of Pea Starch

[0037] The molecular weight and spatial conformation changes of pea starch after enzymatic hydrolysis combined with pressure heating modification are shown in Table 6. The changes in number-average molecular weight (Mw), weight-average molecular weight (Mn), molecular weight dispersion coefficient (PD=Mw / Mn), and Z-average radius of gyration (Rz) of starch are related to the morphological changes of starch granules, amylose content, and starch chain structure. Natural pea starch (HEW0) is mainly composed of highly branched chains, and its Mw value (23237.01 kDa), Mn value (91912.98 kDa), and Rz value (188.66 nm) are significantly higher than those of the modified pea starch sample group. Moreover, its PD value is lower at 3.96 kDa, indicating that the molecular chain length uniformity of natural pea starch is better. Compared with natural pea starch (HEW0), the modified pea starch (HEW6-36) showed significant changes in Mw, Mn, PD, and Rz values ​​(p<0.05). Specifically, the Mn value decreased from 23237.01 kDa to 5.84 kDa, the Mw value decreased from 9191.298 kDa to 216.45 kDa, the Rz value decreased from 188.66 nm to 20.46 nm, and the PD value increased from 3.96 kDa to 37.48 kDa. (The text abruptly ends here, likely due to an incomplete translation or missing information.) 6 -10 7 g·mol -1 Compared to amylose, amylose has a lower molecular weight (10). 5 g·mol -1 Therefore, after pullulanase enzymatic debranching, the short side chains of amylopectin are cleaved, causing the large amylopectin molecules to degrade into smaller fragments, disrupting the intermolecular glycosidic bonds, and increasing the amylose content, thus reducing the molecular weight of starch. With prolonged enzymatic hydrolysis, the values ​​of Mn, Mw, and Rz gradually decrease, indicating that prolonged enzymatic hydrolysis can achieve more thorough hydrolysis and debranching of starch chains, increasing the proportion of small fragments. The trend in molecular weight change is consistent with the morphological changes of pea starch granules; after enzymatic hydrolysis, the starch surface becomes rougher as the molecular weight decreases. Mw slightly rebounds at 36 h (216.45 kDa), possibly related to the aggregation or uneven degradation of residual long chains (amylose and long-chain amylopectin) after excessive debranching, but the overall content is still much lower than that of natural pea starch.

[0038] 2.9 Analysis of Rheological Properties Table 7 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on Rheological Properties of Pea Starch

[0039] The rheological properties of starch samples were analyzed using a rheometer. Static rheological analysis is shown below; Figure 8-a and Table 7 present the static rheological curves and changes in various parameters of pea starch before and after modification, respectively. As shown in Figure 8-a, all pea starch gels before and after modification exhibited nonlinear curves. At shear rates of (0-200 s⁻¹),... -1 Within the range of [value missing], the shear stress in the HEW0 group increased rapidly and then tended to stabilize with the extension of enzymatic hydrolysis time. However, after enzymatic hydrolysis and pressure heating treatment, the change in starch shear stress with the fluctuation of shear rate was not significant. The shear stress of natural pea starch was greater than that of the modified pea starch group. Among the modified groups, with the extension of enzymatic hydrolysis time, the shear stress of the HEW6 group was greater than that of other sample groups with enzymatic hydrolysis time, and all gels (HEW6-HEW36) showed low shear stress at high shear rates after enzymatic hydrolysis. As shown in Table 7, compared with the HEW0 group, the τ0, K, and n values ​​of the modified HEW6-36 group were significantly reduced (p<0.05). The changes in τ0 and K values ​​are related to the amylose content and branching degree of starch. With increasing enzymatic hydrolysis time, the branching degree of starch decreases, side chains on the molecular chain are removed, leading to an increase in amylose content. The molecular chain transforms from a "multi-branched, disordered structure" to a "sparsely branched, long-chain structure," significantly reducing the number of entanglement points, resulting in a looser structure and weaker interactions between starch molecules, thus causing a decrease in τ0 and K values. When n < 1, the measured sample is a pseudoplastic fluid. The n value decreases with increasing enzymatic hydrolysis time, indicating enhanced starch fluidity and pseudoplasticity, suggesting lower starch viscosity at high shear rates, consistent with previous findings. In conclusion, pullulanase hydrolysis combined with pressure heating has a significant regulatory effect on the steady-state rheological properties of starch.

[0040] The dynamic rheological analysis is as follows, and the dynamic rheological curves of pea starch before and after modification are shown in Figure 8(bd). Storage modulus (G′) and loss modulus (G′′) characterize the elastic and viscous states of starch gel, respectively. From Figures 8-b and 8-c, it can be seen that G′ of each group of starch gels is greater than G′′. Compared with the HEW0 group, after enzymatic hydrolysis and pressure-heat modification, the G′ and G′′ of the starch gels in the HEW6 and HEW12 groups decreased slightly. However, after long-term enzymatic hydrolysis, the G′ and G′′ of the starch gels in the HEW18-36 groups showed a significant decreasing trend, which is consistent with the trend of RVA detection results. The results indicate that pullulanase treatment can effectively reduce the viscoelasticity of starch gels, and the effect of enzymatic hydrolysis on the viscoelasticity of starch gels is more significant with increasing hydrolysis time. This may be because long-term enzymatic hydrolysis alters the complete starch granule structure, breaking the smooth pea granules into small, rough, porous pieces, reducing their branching and order. tan δ, the ratio of G′′ to G′, reflects the overall viscoelasticity of starch and is related to the rheological changes caused by the interaction of starch molecules. As shown in Figure 8-d, the tan δ of all groups is less than 1, indicating that the elasticity of their starch gel is greater than its viscosity. Compared with the HEW0 group, enzymatic hydrolysis and pressure heating treatment are beneficial to increasing the tan δ of the starch gel, indicating that the modification treatment is beneficial to reducing the viscosity of the starch gel. This may be because pullulanase hydrolyzes the α-1,6 glycosidic bonds in starch, causing the starch chain to debranch and form more linear chains, increasing the number of short straight-chain molecules and decreasing the molecular weight, thereby reducing the cross-linking ability between starch molecules, and thus gradually reducing the gel strength of starch. Similar results were also found in rice starch and glutinous rice starch.

[0041] 2.10 Analysis of Starch Gelatinization Characteristics (RVA) Table 8 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on Gelatinization Characteristics of Pea Starch

[0042] As shown in Figure 9 and Table 8, the gelatinization characteristics of pea starch changed significantly before and after modification. The gelatinization curve of natural pea starch (HEW0) began to gelatinize at 94.83℃ and showed a distinct gelatinization peak with a peak viscosity of 3602 cp and a final viscosity of 4325 cp. The maximum viscosity observed during heating is called the peak viscosity of the starch. Compared with the HEW0 group, the gelatinization viscosity of the HEW6 and HEW12 groups was significantly reduced after enzymatic hydrolysis and pressure heating treatment, while the HEW18-HEW36 groups did not show a distinct peak viscosity. The change in viscosity in the gelatinization curve is related to factors such as the starch granule crystal structure, water absorption and swelling, and amylose content. On the one hand, enzymatic hydrolysis and pressure heating treatment disrupted the original structure of the starch granules, reducing their molecular order and thus lowering the gelatinization viscosity. On the other hand, the change in peak viscosity is positively correlated with the swelling capacity of starch. The modified pea starch has increased amylose content, and because its water-binding capacity is lower than that of amylopectin, it does not easily absorb water and swell, resulting in a decrease in the water absorption capacity and a significant reduction in swelling power. This makes the peak viscosity, trough viscosity, and disintegration value of the HEW6-36 group undetectable, which is consistent with the rheological test results. The shear stress of the modified pea starch is significantly reduced and tends to level off. Final viscosity is positively correlated with the gelling ability of starch; lower viscosity indicates that the pea starch has developed a more stable and heat-resistant crystalline structure during modification. Similar to peak viscosity, the final viscosity of the modified starch is extremely low (10.00-153.33 cp). The final viscosity of the HEW6 and HEW12 groups is significantly reduced, and the HEW18-HEW36 groups have no obvious final viscosity (<50 cp). These results indicate that pullulanase and pressure heat treatment can significantly alter the gelatinization ability of pea starch.

[0043] 2.11 Analysis of Solubility and Swelling Force Results Table 9 Effect of Enzymatic Hydrolysis-Pressure Heating Treatment on Solubility and Swelling Force of Pea Starch

[0044] The solubility and swelling power are related to the water absorption capacity of starch granules and the content of amylose, respectively. Figure 10 and Table 9 show the changes in solubility and swelling power of pea starch before and after modification. After modification, the solubility of pea starch increased with increasing enzymatic hydrolysis time (6-36 h) (12.09%-37.06%). Natural starch has low solubility and strong swelling power. Compared with the HEW0 group, due to enzymatic debranching and pressure-heat treatment, the starch granules partially degrade at high temperatures, producing low molecular weight starch chains, which enhances the solubility of starch granules in water. Heating and enzymatic modification treatment can significantly increase the solubility of starch granules (p < 0.05).

[0045] Contrary to the trend in solubility, the swelling power of pea starch decreased from 7.80 g / g to 3.59 g / g with increasing enzymatic hydrolysis time (6-36 h). Starch swelling mainly occurs in amorphous regions, which have a looser structure and are easily hydrolyzed by amylopectin enzymes such as pullulanase. Debranching disrupts the amylopectin network structure, forming short amylose chains that inhibit starch swelling, thus reducing the swelling capacity of starch granules. Amylose can also undergo complexation reactions with lipids, further limiting starch granule swelling and reducing amylose leaching, resulting in lower swelling power. The results show that with increasing amylose content, the solubility of modified pea starch increases while its swelling power decreases. Compared with natural pea starch, its solubility is significantly improved, and its swelling power is half that of natural pea starch.

[0046] 2.12 Analysis of Amylose Content Results Table 10 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on Amylose Content of Pea Starch

[0047] Pea starch has a high amylose content (35-65%). The apparent amylose (AC) content of pea starch before and after modification was detected, and the results are shown in Table 10. After pullulanase hydrolysis and pressure heating treatment, the AC content of pea starch increased significantly (p<0.05). Furthermore, with increasing hydrolysis time, the AC content showed a trend of first increasing and then decreasing. At 18 h of hydrolysis, the pea starch in the HEW18 group had the highest AC content at 46.69%, while the AC content in the HEW18-W group was slightly lower at 43.30%, representing increases of 14.72% and 11.36% respectively compared to native pea starch (HEW0: 31.97%). The results indicate that after pea starch was treated with enzymatic hydrolysis, pullulanase acted on the α-1,6 glycosidic bonds of amylopectin, thereby producing more free amylose and increasing the RS and amylose content. The combination of pressurization and stirring promotes the degradation of long starch chains and the directional arrangement of molecules, resulting in a higher AC content (46.69%) in the HEW18 group compared to the HEW18-W group (43.30%). Prolonged debranching may lead to the loss of amylose during enzymatic hydrolysis. Excessive debranching weakens the resistance of amylose molecules, which may explain why the amylose content in pea starch did not continuously increase after 18 hours of enzymatic hydrolysis, consistent with the trend in RS content.

[0048] 2.13 Analysis of Starch Digestibility Results Table 11 Effect of Enzymatic Hydrolysis-Pressure Heat Treatment on the In Vitro Digestibility of Pea Starch

[0049] The SDS and RS contents of legume starch ranged from 16.9% to 40% and 50.3% to 78.9%, respectively. Pea starch is a good source of resistant starch, with reported resistant starch contents ranging from 21% to 53.4%. The changes in RDS, SDS, RS, and pGI values ​​of pea starch before and after modification are shown in Table 11. With increasing enzymatic hydrolysis time, compared with the HEW0 group, the RDS content of the HEW6-HEW36 groups gradually decreased, the SDS content showed a trend of first decreasing and then increasing, and the RS content showed a trend of first increasing and then decreasing. At 30 h of enzymatic hydrolysis (HEW30), the starch SDS content was the highest at 34.49%, and the RDS content was the lowest at 2.3%. At 18 h of enzymatic debranching, the RS yield of HEW18 was the highest at 72.41%, and then began to decrease. At this time, the RS content of the HEW18-W group was 69.70%, significantly lower than that of the HEW18 group. This may be due to pullulanase's specific hydrolysis of the α-1,6-glycosidic bonds in amylopectin, leading to a rapid increase in resistant starch (RS) content within a short period (0-18 h). However, prolonged hydrolysis (24-36 h) reduces the number of short linear molecules produced from amylopectin, hindering intermolecular rearrangement and making it difficult to form regenerable crystal structures. The highest RS content (72.41%) was observed in starch hydrolyzed for 18 h, a 27.95% increase compared to the HEW0 group. This result indicates that pullulanase combined with pressure heating can debranch starch, thereby increasing the content of resistant starch. The estimated glycemic index (pGI) measures the postprandial blood glucose response caused by carbohydrates in food. A glucose GI value of 100 is typically used as a reference standard, classifying foods into high-GI (≥70), medium-GI (56-69), and low-GI (≤55) foods. As shown in Table 11, after modification, the GI value of pea starch in the HEW0 group decreased significantly from 97.66 to 46.19-59.45, while the pGI value of the HEW18 group was the lowest at 46.19. This is consistent with its high RS content trend, which may be due to the decrease in RDS content and the increase in SDS and RS content in the starch. Therefore, pea starch prepared by enzymatic hydrolysis-pressure heating has the characteristic of low GI value and has good potential for replacing other starches in the development of low-GI foods.

[0050] Example 3: As shown in Figures 11-16, the present invention also provides an apparatus for preparing resistant pea starch, used to implement the preparation method mentioned in Example 1 above. Specifically, it includes a reaction vessel and a stirring assembly fixedly connected to the reaction vessel. The reaction vessel includes an upper vessel body 1 and a lower vessel body 2 that are detachably and sealed together. The stirring assembly includes a drive motor 5 fixedly mounted on the top of the upper vessel body 1 and a stirring rod 6 extending into the inner cavity of the reaction vessel. Specifically, the stirring rod 6 is connected to the output shaft of the drive motor 5 via a coupling, and the drive motor 5 is fixedly mounted on the top of the upper vessel body 1 via a mounting base. It should be noted that, given that the drive motor 5, coupling, and mounting base are all mature existing technologies in the field, their specific structures and principles will not be described in detail here.

[0051] Referring to Figure 11, the top of the upper vessel 1 is equipped with a raw material inlet 13, a buffer solution inlet 14, an enzyme solution inlet 15, and a washing solution inlet 16, all connected to its internal cavity. Connecting pipes and flanges are provided at each of these locations to facilitate direct connection to external material storage tanks for adding the corresponding raw materials and solutions into the reactor cavity. The top of the upper vessel 1 is also equipped with a pressure gauge 17 and a pressure relief valve 18, both connected to its internal cavity, to monitor the pressure within the reactor cavity in real time, ensuring the safety and compliance of the reaction process. The bottom of the lower vessel 2 is equipped with a discharge port connected to its internal cavity, and a discharge valve 21 is located at the discharge port.

[0052] Referring to Figures 13 and 14, the inner wall of the upper vessel 1 is provided with an inlet heat exchange ring 3 and a outlet heat exchange ring 4 arranged axially at intervals. Both the inlet heat exchange ring 3 and the outlet heat exchange ring 4 are provided with annular inner cavities for storing heat-conducting liquid. Referring to Figure 12, the outer wall of the upper vessel 1 is provided with an inlet connection port 11 that penetrates its side wall and communicates with the annular inner cavity of the inlet heat exchange ring 3, and an outlet connection port 12 that communicates with the annular inner cavity of the outlet heat exchange ring 4. This allows for the connection of an external heat-conducting liquid (such as heat-conducting oil) to be pumped into the vessel through the inlet connection port 11 and the outlet connection port 12, thereby realizing the pumping in and pumping out circulation flow heat exchange of the heat-conducting liquid.

[0053] Referring to Figure 15, the stirring rod 6 is provided with a stirring branch tube 7 fixedly connected to it. The stirring branch tube 7 has a pear-shaped profile, narrower at the top and wider at the bottom, to facilitate uniform stirring of the material located at the bottom of the reactor. Furthermore, several sets of stirring branch tubes 7 are provided, and they are evenly spaced along the circumference with the axis of the stirring rod 6 as the center. Specifically, in this embodiment, three sets of stirring branch tubes 7 are provided, and they are evenly spaced along the circumference to improve the uniformity and efficiency of stirring and heat exchange.

[0054] As shown in Figures 15 and 16, the top end of the stirring tube 7 is provided with an inlet 71 and a outlet 72 on both sides of the stirring rod 6. The inlet 71 is connected to the annular inner cavity of the inlet heat exchange ring 3, and the outlet 72 is connected to the annular inner cavity of the outlet heat exchange ring 4. This allows the heat-conducting liquid to flow into the annular inner cavity of the inlet heat exchange ring 3 through the inlet 11, and then flow into the stirring tube 7 through the inlet 71. It then flows into the annular inner cavity of the outlet heat exchange ring 4 through the outlet 72, and finally flows out through the outlet 12. This achieves the circulation and heat exchange of the heat-conducting liquid in the inner cavity of the stirring tube 7, thereby achieving uniform and efficient heating or cooling of the material in contact with the stirring tube 7 during the stirring process. It should be noted that the external heat transfer liquid circulation device connected to the liquid inlet 11 and the liquid outlet 12 adopts a circulation device with a pressurized pump body to ensure the normal circulation flow of the heat transfer liquid in the stirring branch tube 7. Since the heat transfer liquid circulation device and the pressurized pump body are both mature existing technologies in this field, their specific structures are not shown in the figure, and their principles will not be described in detail here.

[0055] Furthermore, as shown in Figures 14 and 16, the liquid inlet heat exchange ring 3 includes a liquid inlet ring rail 31 fixedly disposed on the inner wall of the upper vessel body 1 and a liquid inlet ring plate 32 movably and sealingly connected to the liquid inlet ring rail 31. The liquid inlet ring plate 32 is rotatably and sealingly embedded inside the liquid inlet ring rail 31, so that the inner wall of the upper vessel body 1, the upper and lower inner walls of the liquid inlet ring rail 31, and the outer wall of the liquid inlet ring plate 32 form a sealed annular inner cavity of the liquid inlet heat exchange ring 3. The liquid inlet port 71 of the stirring branch pipe 7 is fixedly connected to the liquid inlet ring plate 32 and it penetrates the liquid inlet ring plate 32 and communicates with the annular inner cavity of the liquid inlet heat exchange ring 3. Similarly, the drain heat exchange ring 4 includes a drain ring rail 41 fixedly installed on the inner wall of the upper vessel 1 and a drain ring plate 42 movably and sealingly connected to the drain ring rail 41. The drain ring plate 42 is rotatably and sealingly embedded inside the drain ring rail 41, so that the inner wall of the upper vessel 1, the upper and lower inner walls of the drain ring rail 41, and the outer wall of the drain ring plate 42 form a sealed annular cavity of the drain heat exchange ring 4. The drain port 72 of the stirring branch tube 7 is fixedly connected to the drain ring plate 42 and it passes through the drain ring plate 42 and communicates with the annular cavity of the drain heat exchange ring 4.

[0056] Referring to Figures 15 and 16, both the sidewalls of the inlet ring rail 31 and the outlet ring rail 41 are equipped with guide ring grooves 8 that are compatible with the stirring branch tube 7. This allows the stirring branch tube 7 to rotate synchronously under the action of the stirring rod 6. The inlet ring plate 32 and the outlet ring plate 42, which are fixedly connected to the stirring branch tube 7, also rotate synchronously. At the same time, the heat-conducting liquid circulates through the inner cavity of the stirring branch tube 7 between the inlet heat exchange ring 3 and the outlet heat exchange ring 4 for heat exchange, thus achieving simultaneous stirring and heating or cooling of the material through the stirring branch tube 7. Since the stirring branch tube 7 can fully and comprehensively contact the material under high-speed rotation, this method of heat exchange using the stirring branch tube 7 can achieve more comprehensive, uniform, and efficient heating or cooling of the material compared to the existing method of heat exchange through the reactor body, with lower heat loss and lower energy consumption.

[0057] Furthermore, referring to Figure 14, at least one set of sealing rings 9 is provided between the liquid inlet ring rail 31 and the liquid inlet ring plate 32, and at least one set of sealing rings 9 is also provided between the liquid outlet ring rail 41 and the liquid outlet ring plate 42, to ensure the sealing of the annular inner cavity of the liquid inlet heat exchange ring sleeve 3 and the liquid outlet heat exchange ring sleeve 4. The sealing rings 9 can be commonly used sealing rubber rings or sealing rings made of other materials. Specifically, in this embodiment, four sets of sealing rings 9 are provided between the liquid inlet ring rail 31 and the liquid inlet ring plate 32, respectively located between the upper and lower inner walls and the side walls where the liquid inlet ring rail 31 and the liquid inlet ring plate 32 contact. Four sets of sealing rings 9 are also provided between the liquid outlet ring rail 41 and the liquid outlet ring plate 42, respectively located between the upper and lower inner walls and the side walls where the liquid outlet ring rail 41 and the liquid outlet ring plate 42 contact.

[0058] Furthermore, as shown in Figures 12 and 13, a heat exchange jacket 22 is fixedly connected to the outer wall of the lower vessel 2. The heat exchange jacket 22 has a accommodating cavity for storing heat-conducting liquid. The heat exchange jacket 22 is provided with a heat exchange inlet 23 and a heat exchange outlet 24 communicating with its accommodating cavity, so as to connect to an external heat-conducting liquid circulation pumping device through the heat exchange inlet 23 and the heat exchange outlet 24. It should be noted that the heat-conducting liquid circulation pumping device connected to the heat exchange jacket 22 and the heat-conducting liquid circulation pumping device connected to the aforementioned inlet heat exchange ring 3 and outlet heat exchange ring 4 can be a set of heat-conducting liquid circulation pumping devices. Of course, two independent sets of heat-conducting liquid circulation pumping devices can also be used to achieve more precise and stable temperature adjustment and control. The preferred scheme is that the heat exchange jacket 22 is used to handle temperature control with large temperature fluctuations and low adjustment accuracy in the early stage, while the inlet heat exchange ring 3 and outlet heat exchange ring 4 are used for temperature control with smaller temperature fluctuations and higher adjustment accuracy. Furthermore, it is understandable that, due to the use of a smaller diameter stirring tube 7 for heat exchange, the temperature control lag is smaller, meaning that it can quickly complete temperature changes, especially in preparation reaction environments where enzymatic hydrolysis requires repeated heating and cooling and where high temperature accuracy is required.

[0059] As shown in Figures 11 and 13, the lower vessel 2 is also equipped with a temperature monitoring unit 25 that penetrates the heat exchange jacket 22 and the side wall of the lower vessel 2. The temperature monitoring unit 25 is located near the bottom of the lower vessel 2 and is connected to the inner cavity of the lower vessel 2 to monitor the temperature of the material located at the bottom of the lower vessel 2 in real time. Specifically, the temperature monitoring unit 25 includes a temperature sensor that extends into the inner cavity of the lower vessel 2 and a thermometer located outside the lower vessel 2. Of course, an electronic receiver or other data receiving device electrically connected to the temperature sensor can also be used to acquire the monitored temperature data in real time.

[0060] Specifically, due to the use of the stirring tube 7 for heating and cooling, the temperature control efficiency was significantly improved. In the actual preparation of pea resistant starch, the gelatinization time was reduced from 30 min to 18 min, a 40% reduction. The cooling time after gelatinization was reduced from 180 min to 36 min, an 80% reduction. Furthermore, since there was no need to transfer intermediate products and materials, the time required for transfer operations was eliminated by 30-40 min. It should be noted that since the enzymatic hydrolysis process requires 18-20 h and the subsequent aging and retrogradation process requires 24 h, which constitutes the majority of the production preparation time, the overall time reduction rate cannot effectively reflect the beneficial effects of using the above-mentioned preparation device. Therefore, the overall time reduction rate will not be calculated or shown in detail here.

[0061] It is understood that, in conjunction with the pea resistant starch preparation method provided in Embodiment 1 of the present invention, in the actual preparation process of pea resistant starch, the following steps, including the preparation of starch milk, starch milk stirring and gelatinization, enzymatic hydrolysis, and stirring and pressing, are all continuously completed in the preparation device provided in this embodiment. There is no need to transfer intermediate products and materials, which greatly improves the production efficiency and the quality of the prepared product, shortens the production time required, and reduces the labor intensity of relevant personnel. Specifically, firstly, pea starch is weighed and placed into the reactor through the raw material inlet 13. Simultaneously, a buffer solution is injected into the reactor through the buffer solution inlet 14 to obtain starch slurry. Then, the reactor is heated through the inlet heat exchange ring 3 and outlet heat exchange ring 4 of the upper reactor body 1 and the heat exchange jacket 22 of the lower reactor body 2 to ensure the starch slurry is at a temperature of 90°C. The stirring rod 6 and stirring branch 7 of the stirring assembly rotate to stir and gelatinize the starch slurry. After stirring and gelatinization are completed, the stirring assembly stops rotating, and the reactor is cooled through the inlet heat exchange ring 3 and outlet heat exchange ring 3 of the upper reactor body 1 and the heat exchange jacket 22 of the lower reactor body 2 to ensure a temperature of 55°C. Subsequently, pullulanase is added through the enzyme solution inlet 15. The stirring assembly operates, driving the stirring rod 6 and stirring branch 7 to rotate and stir for debranching, maintaining the temperature at 55°C for 18-20 minutes of enzymatic hydrolysis. h; After enzymatic hydrolysis is completed, the inside of the reactor is heated through the inlet heat exchange ring 3 and outlet heat exchange ring of the upper reactor body 1 and the heat exchange jacket 22 of the lower reactor body 2. At the same time, the internal pressure of the reactor is detected by the pressure gauge 17 to ensure continuous stirring and pressurization at 121℃. After the stirring and pressurization treatment is completed, the pressure is released from the reactor through the pressure relief valve 18. At the same time, washing liquid (deionized water, sewage ethanol) is added through the washing liquid inlet 16. The stirring component works to stir and mix evenly. Finally, the material is collected through the discharge valve 21 at the bottom of the lower reactor body 2 for subsequent washing, centrifugation, drying, grinding, sieving and other operations.

[0062] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. All equivalent changes and modifications made within the scope of the present invention should still fall within the scope of the present invention.

Claims

1. A method for preparing resistant pea starch, characterized in that, The process includes the following steps: (1) Weigh pea starch and disperse it in a buffer solution with a pH of 5.2 to prepare a starch milk with a concentration of 10%; (2) Gelatinization: Place the starch milk in a 90°C environment and stir to gelatinize for 25-30 min, then cool it to 55°C. The gelatinization process is carried out using a heatable stirring assembly; (3) Enzymatic hydrolysis: Add pullulanase and stir continuously at 55°C to debranch the starch. After hydrolysis for 18-20 h, stir continuously at 121°C and pressurize for 20 min; (4) Centrifugation: Wash and centrifuge three times, age and regenerate at 4°C for 24 h, dry at 45°C to constant weight, grind and pass through a 120-mesh sieve to obtain pea resistant starch.

2. The preparation method as described in claim 1, characterized in that: (1) The buffer solution is a 0.1 mol sodium acetate buffer solution with a pH of 5.

2.

3. The preparation method as described in claim 1, characterized in that: (3) The pullulanase activity is 4000 NPUN / g, and the mass ratio of pea starch to pullulanase is 100:(1.0-2.0).

4. The preparation method as described in claim 1, characterized in that: In (3), the mass ratio of pea starch to pullulanase is 100:1.

5.

5. The preparation method as described in claim 1, characterized in that: In (3), the enzymatic hydrolysis time is 18 h.

6. An apparatus for preparing pea resistant starch, used to implement the preparation method as described in any one of claims 1-5, characterized in that: The reactor comprises an upper vessel body (1) and a lower vessel body (2), and a stirring assembly fixedly connected to the reactor body. The inner wall of the upper vessel body (1) is provided with axially spaced inlet heat exchange rings (3) and outlet heat exchange rings (4). The upper vessel body (1) is provided with an inlet connection port (11) communicating with the inner cavity of the inlet heat exchange ring (3) and an outlet connection port (12) communicating with the inner cavity of the outlet heat exchange ring (4). The stirring assembly includes… The driving motor (5) and the stirring rod (6) extending into the inner cavity of the reactor are provided. The stirring rod (6) is provided with a stirring branch tube (7) fixedly connected to it. The top end of the stirring branch tube (7) is provided with an inlet pipe (71) and a outlet pipe (72) arranged on both sides of the stirring rod (6). The inlet pipe (71) is connected to the inner cavity of the inlet heat exchange ring (3), and the outlet pipe (72) is connected to the inner cavity of the outlet heat exchange ring (4).

7. The preparation apparatus according to claim 6, characterized in that: The liquid inlet heat exchange ring (3) includes a liquid inlet ring rail (31) fixedly installed on the inner wall of the upper vessel body (1) and a liquid inlet ring plate (32) movably and sealedly connected to the liquid inlet ring rail (31). The liquid inlet port (71) is fixedly connected to the liquid inlet ring plate (32) and it passes through the liquid inlet ring plate (32) and communicates with the inner cavity of the liquid inlet heat exchange ring (3). The liquid outlet heat exchange ring (4) includes a liquid outlet ring rail (41) fixedly installed on the inner wall of the upper vessel body (1) and a liquid outlet ring plate (42) movably and sealedly connected to the liquid outlet ring rail (41). The liquid outlet port (72) is fixedly connected to the liquid outlet ring plate (42) and it passes through the liquid outlet ring plate (42) and communicates with the inner cavity of the liquid outlet heat exchange ring (4).

8. The preparation apparatus as described in claim 6, characterized in that: The stirring tube (7) has a pear-shaped outline that is narrow at the top and wide at the bottom. Several sets of the stirring tube (7) are arranged evenly in the circumferential direction with the axis of the stirring rod (6) as the center.

9. The preparation apparatus as described in claim 6, characterized in that: The upper vessel (1) is provided with a raw material inlet (13), a buffer solution inlet (14), an enzyme solution inlet (15), and a washing liquid inlet (16) connected to its inner cavity at the top. The upper vessel (1) is also provided with a pressure gauge (17) and a pressure relief valve (18) connected to its inner cavity at the top. The lower vessel (2) is provided with a discharge port connected to its inner cavity and a discharge valve (21) fixedly connected to it at the bottom.

10. The preparation apparatus according to claim 6, characterized in that: The lower vessel (2) is provided with a heat exchange jacket (22) fixedly connected to the outer wall of the lower vessel (2). The heat exchange jacket (22) is provided with a heat exchange inlet (23) and a heat exchange outlet (24) communicating with its inner cavity. The lower vessel (2) is also provided with a temperature monitoring unit (25) that penetrates the heat exchange jacket (22) and the side wall of the lower vessel (2) and extends into the inner cavity of the lower vessel (2).

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