A method for preparing sesame paste

Abstract

This invention provides a method for preparing sesame paste, relating to the field of sesame paste processing technology. The method involves selecting sesame seeds, washing and drying them to remove impurities, obtaining raw materials, heating the raw materials to obtain roasted sesame seeds, cooling the roasted sesame seeds and removing debris to obtain roasted sesame seeds to be ground, and grinding the roasted sesame seeds to a predetermined median diameter to obtain sesame paste. This sesame paste contains no additives, uses simple raw materials, and only controls the median diameter of the roasted sesame seeds. Without damaging the structure and properties of the proteins, the sesame paste has a delicate texture, rich aroma, is not prone to oil separation, has an unstable oil-paste interface, is not prone to rancidity, and has a long shelf life.

Description

Technical Field

[0001] This invention belongs to the field of sesame paste processing technology, and specifically relates to a method for preparing sesame paste. Background Technology

[0002] Sesame paste is a product made from sesame seeds through processes such as washing, removing impurities, roasting, and grinding. Consuming sesame paste not only satisfies people's taste buds, but the grinding process also makes the nutrients and active ingredients in sesame seeds more easily absorbed by the body, maximizing their nutritional and health benefits.

[0003] Sesame paste is a multiphase dispersion system. After being left to stand for a period of time, the oil-paste interface becomes unstable, easily leading to oil-paste separation. The oil that rises to the top is prone to oxidation and rancidity, while the particles at the bottom settle and cause the lower layer to harden, severely affecting the product's flavor, spreadability, and shelf life. Current technologies improve product stability by adding natural antioxidants and emulsifiers, but this compromises the purity and flavor of the sesame paste. Summary of the Invention

[0004] In view of this, the present invention provides a method for preparing sesame paste that does not affect the purity and flavor of the sesame paste and has a stable oil-paste interface.

[0005] The technical solution adopted by this invention to solve its technical problem is:

[0006] A method for preparing sesame paste includes the following steps:

[0007] S1 Pretreatment: Select sesame seeds, wash and dry them to remove impurities, and obtain the raw materials;

[0008] S2 heating: Heating the raw materials to obtain roasted sesame seeds;

[0009] S3 Smoke Removal: Cool the cooked sesame seeds and remove the debris to obtain the cooked sesame seeds to be ground;

[0010] S4 Grinding: Grind the cooked sesame seeds to be ground to a predetermined median diameter to obtain sesame paste;

[0011] S5 Bottling: Bottle the resulting sesame paste.

[0012] Preferably, in the S4 grinding process, the predetermined median diameter is 65μm-87μm.

[0013] Preferably, in the S4 grinding process, the predetermined median diameter is 70μm-76μm.

[0014] Preferably, in the S4 grinding process, the predetermined median diameter is 80μm-87μm.

[0015] Preferably, in the S4 grinding process, the predetermined median diameter is 65μm-69μm.

[0016] Preferably, in the S2 heating process, the raw material can be heated by an oven, with sesame seeds spread evenly on a baking tray at a temperature of 150℃-170℃, and the thickness of the spread sesame seeds is less than 4mm.

[0017] Preferably, in the S3 smoke emission, the cooked sesame seeds are cooled to below 60°C.

[0018] Preferably, in the S5 bottling process, the bottling containers used must be cleaned and sterilized at high temperature before use.

[0019] Preferably, in the S1 pretreatment, the sesame seeds are plump, free of mold, and have an intact appearance.

[0020] Sesame paste prepared by the method described above.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] This invention provides a method for preparing sesame paste. The method involves selecting sesame seeds, washing and drying them to remove impurities, obtaining raw materials, heating the raw materials to obtain roasted sesame seeds, cooling the roasted sesame seeds and removing debris to obtain roasted sesame seeds to be ground, and grinding the roasted sesame seeds to a predetermined median diameter to obtain sesame paste. This sesame paste contains no additives, uses simple raw materials, and only controls the median diameter of the roasted sesame seeds. Without damaging the structure and properties of the proteins, the sesame paste has a delicate texture, rich aroma, is not prone to oil separation, has an unstable oil-paste interface, is not easily rancid, and has a long shelf life. Attached Figure Description

[0023] Figure 1 The images show the morphology of sesame paste with different particle sizes.

[0024] Figure 2 The rheological properties of sesame paste with different particle sizes are shown in the figure.

[0025] Figure 3 Microstructure diagrams of sesame paste with different particle sizes.

[0026] Figure 4 Zeta potential diagrams of sesame paste with different particle sizes.

[0027] Figure 5 This is a graph showing the oil separation rate of sesame paste under different particle sizes.

[0028] Figure 6 This is a graph showing the sedimentation oil separation rate of sesame paste with different particle sizes.

[0029] Figure 7The graph shows the oxidative stability of sesame paste with different particle sizes.

[0030] Figure 8 Scanning electron microscopy images of protein structures in sesame paste at different particle sizes.

[0031] Figure 9 This is a graph showing the secondary measurement of protein in sesame paste at different particle sizes.

[0032] Figure 10 This is a graph showing the protein properties in sesame paste at different particle sizes.

[0033] Figure 11 This is a graph showing the content of polycyclic aromatic hydrocarbons in sesame paste.

[0034] Figure 12 This is a graph showing the content of heterocyclic amines in sesame paste.

[0035] Figure 13 This is a graph showing the content of volatile compounds in sesame paste.

[0036] Figure 14 A heat map of volatile compounds in sesame paste.

[0037] Figure 15 This is a principal component analysis diagram of volatile compounds in sesame paste.

[0038] Figure 16 This is a schematic diagram of the grinding equipment.

[0039] Figure 17 This is a cross-sectional structural diagram of the grinding equipment.

[0040] Figure 18 This is a front view schematic diagram of the flow diversion component.

[0041] Figure 19 This is a schematic diagram of the drainage component.

[0042] In the figure: lower grinding disc 1, lower annular slope 11, cylindrical platform 12, upper grinding disc 2, upper annular slope 21, embedded hole 22, flow diversion assembly 3, fixing ring 31, flow diversion plate 32;

[0043] Figure 3 Notes: (a) Nile red staining of sesame paste oil; (b) FITC staining of sesame paste protein; (c) Co-distribution of sesame paste oil and protein. Detailed Implementation

[0044] The technical solutions and effects of the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings.

[0045] A method for preparing sesame paste includes the following steps:

[0046] S1 Pre-treatment: Select sesame seeds, wash and dry them to remove impurities, and obtain raw materials; all equipment in the production process needs to be cleaned regularly, every two days, to keep it clean;

[0047] S2 heating: Heating the raw materials to obtain roasted sesame seeds;

[0048] S3 Smoke Removal: Cool the cooked sesame seeds and remove the debris to obtain the cooked sesame seeds to be ground;

[0049] S4 Grinding: Grind the cooked sesame seeds to be ground to a predetermined median diameter to obtain sesame paste;

[0050] S5 Bottling: Bottle the resulting sesame paste.

[0051] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0052] This invention provides a method for preparing sesame paste. The method involves selecting sesame seeds, washing and drying them to remove impurities, obtaining raw materials, heating the raw materials to obtain roasted sesame seeds, cooling the roasted sesame seeds and removing debris to obtain roasted sesame seeds to be ground, and grinding the roasted sesame seeds to a predetermined median diameter to obtain sesame paste. This sesame paste contains no additives, uses simple raw materials, and only controls the median diameter of the roasted sesame seeds. Without damaging the structure and properties of the proteins, the sesame paste has a delicate texture, rich aroma, is not prone to oil separation, has an unstable oil-paste interface, is not easily rancid, and has a long shelf life.

[0053] Furthermore, in the S4 grinding process, the predetermined median diameter is 65μm-87μm.

[0054] Furthermore, in the S4 grinding process, the predetermined median diameter is 70μm-76μm.

[0055] Furthermore, in the S4 grinding process, the predetermined median diameter is 80μm-87μm.

[0056] Furthermore, in the S4 grinding process, the predetermined median diameter is 65μm-69μm.

[0057] Please refer to Figures 16 to 19Furthermore, the grinding equipment used in the S4 grinding includes: a lower grinding disc 1 and an upper grinding disc 2 disposed directly above the lower grinding disc 1; the middle of the top of the lower grinding disc 1 is recessed downward to form a circular bottom, and slopes from the top edge of the lower grinding disc 1 to the edge of the circular bottom to form a lower annular slope 11, which serves as the grinding surface of the lower grinding disc 1. A cylindrical platform 12 is provided on the circular bottom, which can block sesame particles and allow the sesame seeds to be placed on the grinding surface as much as possible; the middle of the bottom of the upper grinding disc 2 protrudes outward to form a circular boss, and slopes from the bottom edge of the upper grinding disc 2 to the edge of the circular boss to form an upper annular slope 21, which serves as the grinding surface of the upper grinding disc 2. An embedded hole 22 adapted to the cylindrical platform 12 is provided in the middle of the bottom of the upper grinding disc 2, which can limit the upper grinding disc 2 and guide the upper grinding disc 2. The upper grinding disc 2 can move up and down along the longitudinal direction to control the gap between the grinding surfaces of the upper grinding disc 2 and the lower grinding disc 1. The longitudinal movement of the upper grinding disc 2 can be achieved by hydraulic or electric drive. During grinding, the gap between the grinding surfaces of the upper grinding disc 2 and the lower grinding disc 1 can be gradually reduced in a step-like manner, thereby gradually increasing the compressive force of the grinding media on the upper and lower grinding discs 2 and 1. This results in a step-like increase in the grinding intensity, ensuring a more uniform particle size distribution during grinding. The upper grinding disc 2 and the lower grinding disc 1 can rotate relative to each other, and both are driven by variable frequency motors. There are three rotation modes for the upper grinding disc 2 and the lower grinding disc 1. The first mode is that the lower grinding disc 1 and the upper grinding disc 2 can rotate in the same direction. The second mode is that the upper grinding disc 2 and the lower grinding disc 1 can rotate in opposite directions, that is, when the upper grinding disc 2 rotates clockwise, the lower grinding disc 1 rotates counterclockwise, or the upper grinding disc 2 rotates counterclockwise and the lower grinding disc 1 rotates clockwise. The third mode is that the lower grinding disc 1 does not rotate, and only the upper grinding disc 2 rotates. When grinding sesame seeds, due to the relative rotation of the upper grinding disc 2 and the lower grinding disc 1, the ground sesame seeds will move towards the periphery of the upper grinding disc 2 and the lower grinding disc 1 under the action of centrifugal force. The lower annular slope 11 can hinder the outward dispersion of sesame seeds, and due to the influence of their own gravity, the sesame seeds will fall downward. At this time, the upper grinding disc 2 can also compress the sesame seeds to achieve a uniform grinding effect.

[0058] Furthermore, the diameter of the upper grinding disc 2 is smaller than that of the lower grinding disc 1, leaving a gap between them; this also facilitates the addition of the grinding media. An annular baffle is provided at the top edge of the lower grinding disc 1 to prevent media from overflowing.

[0059] Furthermore, a flow-guiding assembly 3 is provided on the upper grinding disc 2. The outer edge of the flow-guiding assembly 3 does not contact the annular baffle, and the flow-guiding assembly 3 rotates synchronously with the upper grinding disc 2. The flow-guiding assembly 3 includes a fixing ring 31 and a flow-guiding plate 32. The fixing ring 31 is fitted onto the upper grinding disc 2 and can be fastened to the upper grinding disc 2 with screws for easy disassembly, replacement, and installation. The flow-guiding plates 32 are evenly distributed circumferentially along the outer wall of the fixing ring 31, and the ends of the flow-guiding plates 32 do not contact the annular baffle. The flow-guiding plates 32 are inclined in the longitudinal direction, that is, the axis of the flow-guiding plates 32 forms an angle with the axis of the fixing ring 31. This angle can be adjusted appropriately within the range of 5-10° according to requirements.

[0060] When grinding sesame seeds, the upper grinding disc 2 will drive the guide plate 32 to rotate synchronously. If the upper grinding disc 2 rotates clockwise, the guide plate 32 will generate an upward airflow when rotating, causing the particles between the upper grinding disc 2 and the lower grinding disc 1 to move towards the annular baffle. This is mainly used when the sesame seeds are large. At this time, the sesame seeds need to spread outward to disperse them as much as possible. After dispersion, the sesame seeds will fall back due to their own gravity. The counter-rotation of the upper grinding disc 2 and the lower grinding disc 1 is used to achieve balanced grinding of the sesame seeds. When the upper grinding disc 2 rotates counterclockwise, the guide plate 32 will generate a downward airflow, causing the particles between the upper grinding disc 2 and the lower grinding disc 1 to move towards the center. This is mainly used when the sesame particles become smaller. Since the sesame particles are relatively small, they need to be gathered and ground. At this time, the airflow helps to gather the finer sesame particles as much as possible, preventing dry grinding after the gap between the upper grinding disc 2 and the lower grinding disc 1 becomes smaller. The counterclockwise rotation of the upper grinding disc 2 and the lower grinding disc 1 is used to achieve even grinding of the sesame particles.

[0061] Furthermore, in the S2 heating process, the raw materials can be heated in an oven. The sesame seeds are spread evenly on a baking tray at a temperature of 150℃-170℃, with a thickness of less than 4mm. The resulting white sesame seeds are crispy and have a rich aroma after baking.

[0062] Furthermore, in the S2 heating process, the raw materials can be first heated by infrared heating, and then immediately heated by microwave heating to obtain roasted sesame seeds. Through infrared-assisted microwave heating, the resulting sesame paste exhibits significantly lower levels of benzo[a]pyrene (13.73%), PAH4 (20.5%), Harman (24.27%), Norharman (23.14%), acid value, and peroxide value compared to traditionally roasted sesame paste. On the other hand, infrared-assisted microwave heating produces 2-ethyl-3,5,6-trimethylpyrazine, α-ethylidene-phenylacetaldehyde, methyl dihydrojasmonic acid, and other compounds. Flavor compounds such as 2-buten-1-ol propionate and n-heptanol increased the content of volatile compounds (aldehydes, alcohols, esters, and acids) in the sesame paste by 31.54%, 3.72%, 42.39%, and 16.95%, respectively. Among them, the content of aroma compounds with roasting, bread, nut, and cocoa flavors, such as 3,5-dimethyl-2-pyrazine and 2-ethyl-3,5,6-trimethylpyrazine, increased significantly. The content of isovaleraldehyde, 2-methylbutanal, and phenylacetaldehyde, which are related to umami and lipid aromas, increased significantly. The content of trimethylpentanol, n-hexanol, and 1-octen-3-ol, which are related to sweetness, floral aroma, waxiness, greenness, citrus, and fruit flavors, increased significantly.

[0063] Furthermore, in the S2 heating process, the infrared power is 600W-800W, and the heating time is 2-3.5min.

[0064] Furthermore, in the S2 heating process, the microwave power is 650-750W, and the heating time is 3-5 minutes.

[0065] Furthermore, in the S3 smoke emission, the cooked sesame seeds are cooled to below 60°C.

[0066] Furthermore, in the S5 bottling process, the bottling containers used must be cleaned and sterilized at high temperature before use; the high temperature sterilization specifically involves cleaning the containers and sterilizing them with steam at 121°C for 20 minutes.

[0067] Furthermore, in the S1 pretreatment, the sesame seeds are plump, free of mold, and have an intact appearance.

[0068] Sesame paste prepared by the method described above.

[0069] The following are specific examples of preparation:

[0070] The sesame seeds come from Zhumadian, Henan Province, and are stored in a dry environment at room temperature. The sesame seeds are oval-shaped, approximately 3*1.5*0.5mm, and are selected for their plumpness, good maturity, and absence of mold or spoilage.

[0071] Example 1:

[0072] S1 Pretreatment: Select white sesame seeds that are plump, free of mold, intact in appearance, and bright in color. Soak the selected white sesame seeds in water to wash them. After washing, drain the water and dry them to remove impurities and obtain clean white sesame seeds for subsequent processing.

[0073] S2 Heating: Spread the raw white sesame seeds evenly on a baking tray, with the thickness of the sesame seeds within 4mm, and bake at 170℃ for 20 minutes to obtain roasted sesame seeds;

[0074] S3 Smoke Removal: Cool the roasted sesame seeds to below 60℃ and remove the debris to obtain the roasted sesame seeds to be ground;

[0075] S4 Grinding: Grind the cooked sesame seeds to be ground into a median diameter of 83μm-87μm to obtain sesame paste;

[0076] S5 Bottling: After cleaning the glass jars, sterilize them with high-temperature steam at 121℃ for 20 minutes, and then bottle the resulting sesame paste.

[0077] Example 2:

[0078] The other steps are the same as in Example 1, except that in S4 grinding, the median diameter after grinding is 74μm-76μm.

[0079] Example 3:

[0080] The other steps are the same as in Example 1, except that in S4 grinding, the median diameter after grinding is 67μm-69μm.

[0081] The three sesame paste samples obtained in Examples 1-3 were named G1, G3 and G5, respectively. The stability and quality of the sesame paste were evaluated using the following experimental methods.

[0082] I. The form of sesame paste

[0083] 1. Experimental Method: Place three samples of sesame paste separately on covered glass slides. Observe their natural, compressed, and diffused morphologies, such as... Figure 1 As shown.

[0084] 2. Experimental Results: By spreading the sauce, the state of the sauce under different grinding times can be directly observed. Figure 1It was found that there were significant differences in the natural, extruded, and diffused forms of the three samples. G1 had a very noticeable grainy texture, possibly because the sesame seeds were not fully ground and debris was mixed in with the sesame paste, resulting in an abnormally coarse paste. Compared to G1, G3 and G5 had a silky smooth paste, with the sesame seeds being fully ground and significantly fewer visible impurities. G3 and G5 had high fluidity and were easier to spread, which may be related to the variation in the particle size of the sesame paste. G1 had a larger particle size, which reduced its fluidity. However, with increasing grinding times, the internal structure of the sesame seeds was disrupted, the particles became smaller, more oil was released, and the fluidity of the sesame paste improved.

[0085] II. Rheological properties of sesame paste

[0086] 1. Experimental Method: After thoroughly stirring the sesame paste sample to be tested, a certain amount of sample was placed on a 35mm diameter plate, and excess sample was scraped off. The mixture was then incubated at 25℃ for 0.1 to 100 seconds. -1 Apparent viscosity and shear stress were measured within the shear rate range. The Ostwald de Waele model is...

[0087] τ=Kγ n

[0088] Where K is the consistency coefficient (Pa s) n ); γ represents the shear rate (s). -1 ) ; τ represents shear stress (Pa); n represents flow performance parameters. For dynamic viscoelasticity, the changes in storage modulus G' and loss modulus G” were recorded at frequencies from 0.1 Hz to 10 Hz.

[0089] 2. Experimental Results: The static rheological properties of sesame paste were measured, and the results are as follows: Figure 2 As shown in Figure a, the apparent viscosity of all sesame paste samples decreased with increasing shear rate, indicating that shear thinning occurred in all samples. G1 had the highest initial viscosity, but its viscosity decreased rapidly with increasing shear rate. Both G3 and G5 showed a slow decrease with increasing shear rate, with G3 having the lowest initial viscosity. These phenomena may be attributed to the reduction in the effective molecular volume, the breaking of molecular entanglement, i.e., the unwinding of molecules, ultimately leading to a decrease in apparent viscosity. To understand the flow behavior of the sesame paste samples, the coefficients (K) and flow behavior exponent (n) were obtained by fitting the data using a power-law model. Figure 2 c, We found that all samples showed a good fit, with a correlation coefficient (R²) of [missing value]. 2All three coefficients (K) are above 0.99. G5 has the highest flow behavior index (n) at 0.66, while G1 has the lowest at 0.51, indicating that the flowability of sesame paste increases with decreasing particle size. Furthermore, the consistency coefficient is closely related to flow characteristics; in food, a low K value signifies a thinner, more "flowing" texture. G3 has the lowest consistency coefficient (K) at 37.92, while G1 has the highest at 83.84, indicating that G3 has the lowest viscosity and better flowability. Figure 2 As shown in b, the shear stress of all sesame paste samples increases non-linearly with increasing shear rate. At the same shear rate, G1 has higher shear stress than G3 and G5. This may be because reducing the particle size of sesame paste disrupts the internal structure of the sesame seeds, weakening particle-particle interactions and leading to lower shear stress. This corresponds to the change in apparent viscosity. In summary, sesame paste with different particle sizes exhibits significantly different flow characteristics; by adjusting the particle size, specific food products with desired consistency ("flowability") can be produced.

[0090] The dynamic rheological properties of sesame paste were studied using a permeation test with an oscillation frequency of 0.1–10 Hz. Figure 2 Figures 2d, 2e, and 2f show the elastic modulus (G') and loss modulus (G”) of different sesame pastes. Both G' and G” increase linearly with frequency. For G3 and G5, all G” values ​​are higher than G', indicating that the samples are more viscous than elastic. Furthermore, there is no crossover point between G” and G', a characteristic similar to liquids. However, G1 has a crossover point, indicating a state transition in the sesame paste where viscoelasticity dominates. Overall, smaller particle size sesame pastes exhibit higher G” values ​​than larger particle size sesame pastes. Additionally, the larger storage modulus values ​​indicate strong particle-particle interactions and / or a stable network structure.

[0091] The above results indicate that as the particle size of sesame paste decreases, the fluidity of the paste increases. G3 and G5 exhibit liquid characteristics, and the larger "G" suggests that their pastes have a more stable network structure.

[0092] III. Microstructure of Sesame Paste

[0093] 1. Experimental Methods: The microstructure of sesame paste samples was observed using a laser scanning confocal microscope (CLSM). First, the sesame paste was stirred thoroughly. 0.5g of the sesame paste sample was taken and 20μL of fluorescein isothiocyanate and 20μL of Nile red staining solution were added. The mixture was stirred until fully homogeneous and allowed to stand overnight. A small amount of sample was placed on a glass slide, covered with a coverslip, and a uniform, bubble-free thin slide was prepared for observation using CLSM. The concentration of Nile red staining solution was 0.1% (w / v), the excitation wavelength was 488nm, and the detection wavelength was 580-620nm; the concentration of fluorescein isothiocyanate staining solution was 0.1% (w / w), the excitation wavelength was 633nm, and the detection wavelength was 651-710nm.

[0094] 2. Experimental Results: Protein is an important substance for adsorbing oil, accounting for up to 25% of the content in sesame paste. Smaller particle size increases the fluidity of the sesame paste, potentially significantly altering the distribution of oil and protein. By staining the paste and then observing it under a microscope, the distribution of protein and oil can be observed, thus characterizing the effect of particle size changes on the distribution of oil and protein. Staining the oil and protein before observation is necessary; the results are as follows. Figure 3 As shown in the diagram, red areas represent the presence of oils, green areas represent the presence of proteins, and black areas represent unstained substances. In G1, the red and green areas are evenly distributed, indicating that oils and proteins are dispersed with no significant interaction. In contrast, the red area in G3 is larger, and a large amount of green area is also observed in this area, suggesting that proteins and oil droplets aggregate together. In G5, there is also a clear co-distribution of red and green areas, but it is not as pronounced as in G3. This may be because the high-temperature reaction during crop friction can denature proteins and destroy the polysaccharide backbone, leading to a decrease in oil adsorption capacity. The above research suggests that smaller particle sizes may result in a more uniform distribution of substances, which is beneficial for protein to contact with and bind oils. This sesame paste may have a more stable system to resist oil separation. The protein particle size is also significantly smaller, which may cause changes in protein structure and properties, thus resulting in significant differences in the oil adsorption effect.

[0095] IV. Zeta potential of sesame paste with different particle sizes

[0096] 1. Experimental Method: Sesame paste and deionized water were mixed at a ratio of 1:100 to form a dispersion. The electrophoresis potential of the sesame paste was measured using a Zeta potentiometer. 650 ml of the diluted sample was placed in the electrophoresis tank and its potential value was measured. The average value was taken from three measurements.

[0097] 2. Experimental Results: The Zeta potential is a measure of the strength of the repulsive or attractive forces between particles, and its value is related to the stability of colloidal dispersion. The smaller the molecules or dispersed particles, the higher the absolute value (positive or negative) of the Zeta potential, and the more stable the system, meaning that dissolution or dispersion can resist aggregation. Conversely, the lower the Zeta potential (positive or negative), the more inclined it is to coagulate or aggregate, meaning that the attractive force exceeds the repulsive force, the dispersion is destroyed, and coagulation or aggregation occurs.

[0098] Zeta potential analysis was performed on the prepared sesame paste, and the results are as follows: Figure 4 As shown, the absolute value of the Zeta potential in G3 is significantly higher than that in G1 and G5, with the absolute value of the Zeta potential in G5 being higher than that in G1. This indicates that the substances in G3 tend to disperse, while the substances in G1 tend to aggregate. The surface charge of the substances is neutralized, resulting in a decrease in the absolute value of the Zeta potential. This suggests that a moderate reduction in particle size can promote the improvement of the stability of the sesame paste system.

[0099] V. Centrifugal oil separation rate of sesame paste with different particle sizes

[0100] 1. Experimental Method: Weigh 40g of sesame paste into a 50ml centrifuge tube, cap it, and immediately heat it in an 80℃ water bath for 30 minutes, then cool it under running tap water for 15 minutes. Next, centrifuge the sample continuously at 4000×g for 10 minutes, remove the separated oil using a Pasteur pipette, and calculate the percentage of oil released from the sample. The formula is the formula for calculating the oil separation rate of sesame paste.

[0101] C1=m1 / m2×100 (1)

[0102] In the formula, C is the oil separation rate (%); m1 is the mass of the upper floating oil (g); and m2 is the mass of the sesame paste (g).

[0103] 2. Experimental Results: Centrifugation can quickly separate the oil from the sesame paste. The oil separated by this high centrifugal force is considered to be the maximum amount of oil that can be separated during storage, and this amount is far lower than the total oil in the sesame paste system. The separated free oil was measured by determining the centrifugal oil separation rate. The results are as follows: Figure 5 As shown, the oil separation rates of G3 and G5 are significantly lower than those of G1, indicating that smaller particle size slows down the oil-water separation trend. However, the oil separation rate of G5 is higher than that of G3, suggesting that excessively small particle size does not continuously enhance the stability of the paste. This may be because the internal structure of sesame seeds is disrupted when the particle size is smaller, and repeated friction and overheating may damage some heat-sensitive components in sesame seeds, thus reducing the ability of the paste's internal substances to adsorb oil.

[0104] VI. Sedimentation and oil separation rate of sesame paste with different particle sizes

[0105] 1. Experimental Method: Take about 30g of sesame paste into a fine-marked bottle and leave it at room temperature. Measure the height of the oil separation layer every 30 days (after 60, 90, and 120 days of storage). The formula is for calculating the sedimentation oil separation rate of sesame paste.

[0106] C2=H1 / H×100 (2)

[0107] In the formula, C is the sedimentation oil separation rate (%); H1 is the height of the oil separation layer (mm); and H is the total height of the sesame paste (mm).

[0108] 2. Experimental Results: By measuring the rate of oil-soybean separation during storage—specifically, the rising of oil and the sedimentation of solids—the sedimentation oil rate was obtained, which characterizes the stability of the oil-soybean system under natural conditions. Figure 6 It can be seen that the sesame paste produced by this method exhibits only a very small amount of oil separation after 120 days, and the trend of oil-soybean separation is significantly slowed down. This sesame paste can maintain an oil-soybean state for a long time. Table 1 shows that after 60, 90, and 120 days of sesame paste production, the sedimentation oil separation rates of G3 and G5 are lower than that of G1, with G3 reaching the lowest level. This is consistent with the experimental results of centrifugal oil separation, indicating that smaller particle size can slow down the oil-water separation trend of the paste; excessively smaller particle size is detrimental to the stability of the paste.

[0109] Table 1 Sedimentation and oil separation rate of sesame paste

[0110]

[0111] VII. Oxidative stability of sesame paste with different particle sizes

[0112] 1. Experimental Methods: Sesame paste samples were collected on days 0 and 45, and the changes in acid value and peroxide value were measured. Acid value was determined according to GB / T 5009.229—2016 "National Food Safety Standard - Determination of Acid Value in Food"; peroxide value was determined according to GB / T 5009.227—2016 "National Food Safety Standard - Determination of Peroxide Value in Food".

[0113] 2. Experimental Results: The acid value and peroxide value of sesame paste with different particle sizes were determined to evaluate the oxidative stability of the paste. The results are shown in […]. Figure 7 Acid value reflects the degree of fat hydrolysis during storage and is therefore considered an indicator of rancidity. From Figure 7As can be seen from the data, the acid value (KOH) of all three sesame paste samples met the requirement of less than or equal to 3 mg / g as specified in LS / T 3220—2017 "Sesame Paste". It is evident that the acid value of all samples increased to varying degrees with increasing storage time, indicating that the oxidative rancidity of fats is an irreversible process. Furthermore, with increasing grinding times, the acid value rose from 0.43 mg / g to 0.49 mg / g, indicating that excessive grinding does indeed increase the degree of oil oxidation, which is detrimental to the oxidative stability of sesame paste. The increasing trend of acid value also differed among the samples. A comprehensive analysis of the data from several groups of sesame pastes revealed that the increase in acid value for G1 and G3 was relatively slow, but for G5, after 45 days of storage at room temperature, the acid value increased from 0.49 mg / g to 0.63 mg / g. This rate of increase may be detrimental to the shelf life of sesame paste. Peroxide value directly reflects the oxidative rancidity of oils in sesame paste; therefore, the peroxide values ​​of fresh sesame paste and sesame paste stored for 45 days were measured and compared. The results are shown in [Figure 1]. Figure 7 b. G5 had the highest initial peroxide value at 0.036 g / 100 g, and also the highest at 45 days at 0.118 g / 100 g, meeting the requirement of LS / T3220—2017 "Sesame Paste" for a peroxide value less than or equal to 0.25 g / 100 g. Corresponding to the acid value results, the peroxide value of sesame paste increased as the particle size decreased. This may be because the friction, collision, and shear forces caused by stone milling disrupted the structure of the sesame seeds, releasing more oil. Excessive grinding time or heat generated by friction exacerbated the oxidative rancidity of the oils in the sesame paste. The peroxide value increases of G1 and G3 were not significant, indicating that these sesame pastes had relatively good oxidative stability.

[0114] VIII. Protein Structure and Functional Characteristics in Sesame Paste with Different Particle Sizes

[0115] 1. Experimental Method: A certain amount of sesame paste was placed in a centrifuge tube and centrifuged at 4000×g for 10 minutes at 25℃. The paste was defatted using n-hexane (1:10, w / v, sesame paste to solvent ratio) and stirred continuously at room temperature for 2 hours. The paste was defatted twice (using the same sesame paste to n-hexane ratio), then filtered and dried. The sesame paste powder was suspended in distilled water at pH 11 at a ratio of 1:10 (w / v) and stirred with a magnetic stirrer at 25℃ for 2 hours. The mixture was centrifuged at 8000rpm at 25℃ for 30 minutes. The supernatant obtained after centrifugation was adjusted to pH 4.5 with HCl, placed overnight at 4℃ for 18 hours, and then centrifuged at 8000rpm at 5℃ for 30 minutes. The resulting precipitate was washed twice with distilled water, neutralized to pH 7.0 with 2M NaOH, and then the protein solution was freeze-dried under vacuum. The freeze-dried powder was stored in a vacuum desiccator. The proteins extracted from G1, G3, and G5 were named SP1, SP3, and SP5, and used in the following studies.

[0116] (1) Microstructure: The influence of scanning electron microscopy on the surface microstructure of SPI particles was studied. Protein samples were coated with a 10 nm thick gold-palladium layer and displayed at 500x and 2000x magnifications under accelerating voltages of 8 kV and 9 kV.

[0117] (2) Protein secondary structure: The protein extracted from sesame paste was freeze-dried and thoroughly ground with potassium bromide (KBr) at a ratio of 1:100 in an agate mortar for FTIR spectroscopy measurements. Approximately 1 mg of sample was used for measurement; the sample was placed on the surface of an ATR crystal and pressed down with a flat-head plunger. Measurements were taken from 4000 to 400 cm⁻¹. -1 , at 4cm -1 A total of 64 scans were performed at the specified resolution. OPUS 7.2 software was used to eliminate background interference. The scan ranged from 1600 to 1700 cm⁻¹. -1 The amide I band was processed using Peak Fit software for Fourier transform deconvolution and second-order derivative peak fitting. The correspondence between the α-helix absorption peak and the secondary structure is as follows: the α-helix absorption peak is located at 1648–1660 cm⁻¹. -1 1610-1636cm -1 and 1682-1690cm -1 It is β-folded; 1661-1681 cm -1 For β-turn angle; and 1637-1647cm -1 The coils are irregular. All experiments were conducted at room temperature.

[0118] (3) Protein surface hydrophobicity: The protein suspension was diluted to 5 mg / mL with 50 mM PBS (0.6 M KCl, pH = 7.0). Then, 200 μL of BPB solution (1 mg / mL dissolved in deionized water) was mixed with 1 mL of the diluted protein sample and deionized water as the treatment sample and control sample, respectively, and vortexed at 20 °C for 10 min. After centrifugation at 2000 × g for 15 min, the absorbance of the collected supernatant was measured at 595 nm using a microplate reader. The BPB-binding protein content was calculated according to the following formula:

[0119]

[0120] Where Ac is the absorbance of the control sample and As is the absorbance of the treated sample.

[0121] (4) Protein active thiol groups: The sample was dispersed at a concentration of 1% (w / v) in Tris-gly buffer (0.086 M Tris, 0.09 M glycine, 4 mM Na2EDTA, pH 8.0). After stirring and centrifugation, the supernatant was mixed with 0.03 mL Ellman's reagent and incubated for 15 min. The absorbance was measured at 412 nm. The control group was phosphate buffer. The free thiol content of the sample was calculated using the formula:

[0122]

[0123] Where 73.53 = 10 6 / (1.36×10 4 ), 1.36×10 4 A is the molar extinction coefficient of the DNTB reagent. 412 The absorbance at 412 nm is represented by D, which indicates the dilution factor, and C indicates the final concentration of the sample.

[0124] (5) Protein emulsifying properties: Accurately weigh a certain mass of sesame paste protein and dissolve it in deionized water to prepare a 1.0% (w / v) protein solution. Stir at a constant speed for 2 hours using a magnetic stirrer and store at 4℃. Add sesame oil to the protein dispersion and shear at 19000 rpm for 1 minute at room temperature to prepare an emulsion. Immediately and completely vortex disperse 50 μL aliquots of the prepared sample into 5 mL of SDS solution (0.1%), and then measure the absorbance at 500 nm. Keep the remaining portion of the diluted solution at room temperature for 30 minutes and repeat the above absorbance measurement. Using SDS solution as a blank, measure the absorbance at a wavelength of 500 nm. EAI and ESI are calculated using equations.

[0125]

[0126] Where A0 and A 10The absorbance values ​​were measured at 0 minutes and 10 minutes, Δt; at 10 minutes, ΔA; and the difference between the initial value and the absorbance value after 10 minutes.

[0127] 2. Experimental results: (1) The surface structure of SPI can be directly observed using a scanning electron microscope, and the results are as follows: Figure 8 As shown, the appearance of proteins in sesame paste changes significantly with decreasing particle size. SP1 particles are uneven in size, containing many large particles, and the protein surface is rough. Compared to SP1, SP3 particles are smaller, more uniform in size, with a smooth surface and a denser internal structure. SP5 has an even smaller particle size, but the protein surface becomes rougher. The protein surface structure can be seen more clearly under a 2000x microscope, consistent with observations under a 500x microscope: SP1 has a rough surface, SP3 has a denser structure, and SP5 has a rough surface with larger cavities. These results indicate that the microstructure of proteins in sesame paste also changes significantly.

[0128] (2) The secondary structure of the protein was measured, and the results were obtained from... Figure 9 As shown in Table 2, compared with SP1, SP3 showed a significant decrease in helical and random coil content and a significant increase in folded content. This change indicates a shift in protein spatial conformation from folded to extended, with smaller particle size promoting protein unfolding. SP5, on the other hand, exhibited the highest helical and random coil content and the lowest folded content, indicating a return to a folded state. These findings confirm that particle size significantly affects protein structure, which may lead to changes in protein functional properties.

[0129] Table 2 Secondary structure of proteins in sesame paste

[0130]

[0131] (3) Electrophoretic markers such as protein biomarkers (BPB) quantify the hydrophobicity of protein surfaces through their strong hydrophobic interactions with proteins. The interaction between BPB and proteins is assessed by centrifugation to separate free and bound BPB. The titration of bound BPB is performed using absorption spectroscopy, and the amount of bound BPB is considered an indicator of protein hydrophobicity. For example... Figure 10 As shown, compared to G1, SP3 exhibits a significantly increased BPB bond content, indicating increased surface hydrophobicity. This may be due to the smaller particle size, which causes the protein structure to unfold, exposing buried hydrophobic residues on the polar surface. Studies have shown that the stronger the protein's hydrophobicity, the easier it is to effectively adsorb at the oil-water interface. Simultaneously, a dense cross-sectional film can form on the oil droplet surface, preventing droplet aggregation through steric hindrance and stabilizing the emulsion. However, SP5 shows the lowest surface hydrophobicity, which may be related to previous research results; excessively small particle size causes protein structure shrinkage, resulting in a decrease in hydrophobicity.

[0132] (4) The content of active thiol groups in different samples, such as Figure 10 As shown, the results are similar to those observed for surface hydrophobicity. Figure 9 The content of active thiol groups in SP3 was significantly higher than that in SP1, indicating that the exposure of thiol groups was due to protein unfolding. Similarly, the content of active thiol groups in SP5 was the lowest, which may also be due to protein contraction.

[0133] (5) EAI (emulsifying activity) and ESI (emulsifying stability) are important indicators used to characterize the emulsifying properties of proteins, reflecting their ability to stabilize the entire emulsion system. EAI represents the protein's adsorption capacity at the oil-soybean interface; ESI represents the protein's ability to maintain the stability of the oil-soybean dispersion system within a certain time period. The effects of different particle sizes on EAI and ESI in sesame paste proteins are as follows: Figure 10 As shown, the emulsifying activity of proteins with different particle sizes shows an increasing trend, indicating that the emulsifying activity of proteins is largely affected by particle size. This may be because a smaller protein particle size promotes faster diffusion and remodeling of proteins at the oil-water interface. The significantly increased emulsifying stability of SP3 may be due to changes in the SP3 structure, namely increased surface hydrophobicity and exposure of hydrophobic groups. These results suggest that appropriately reducing the protein particle size helps protein structure unfold, enhances protein emulsifying function, and promotes a more stable oil-water interface, resisting oil-water separation.

[0134] Examples 4-6

[0135] S2 Heating: Place 100g of the selected sesame seeds into an electric drum and heat them between two parallel infrared heating plates. Set the infrared power to 600W, 700W, and 800W respectively, and heat for 3 minutes. Set the drum speed to 400rpm. Immediately after heating, remove the sesame seeds and place them on a microwave-safe ceramic plate. Heat them at 700W microwave power for 4 minutes, stirring once every 2 minutes. Except for step S2, the other steps are the same as in Example 2.

[0136] Comparative Example 1

[0137] S2 Heating: Weigh 600g of the selected sesame seeds, and place 100g of each batch into an electric roller to heat between two infrared heating plates placed parallel to each other. Set the infrared power to 700W and heat for 7 minutes. Other steps are the same as in Example 2.

[0138] Comparative Example 2

[0139] S2 Heating: Weigh 600g of the selected sesame seeds and place them in a microwave-safe ceramic dish. Heat at 700W for 7 minutes, stirring once every 2 minutes. Other steps are the same as in Example 2.

[0140] Using Example 2, Comparative Examples 1 and 2 as controls, the quality of sesame paste was evaluated using the following method.

[0141] I. Determination of Polycyclic Aromatic Hydrocarbons in Sesame Paste

[0142] Weigh 1 g ± 0.01 g of sesame paste and mix with 5 mL of acetonitrile (HPLC grade). Vortex vigorously for 1 min, then extract with ultrasonic assistance for 8 min, followed by centrifugation at 4000 r / min for 5 min. Transfer the supernatant to a glass tube. Repeat the extraction process twice. Thoroughly mix the three extracts in a sealed glass bottle and freeze overnight at -18°C. Then, rotary evaporate the sample at 60°C, concentrating the separated supernatant until essentially solvent-free. Redissolve the residue in 2 mL of n-hexane and pass it through a pre-activated PCX solid-phase extraction column twice at a loading rate of 1 mL / min. Elute the solid-phase extraction column with 4 mL of n-hexane-dichloromethane (1:1, v / v). Dry the collected eluent under nitrogen at 45°C, redissolve it with 1 mL of acetonitrile, filter through a 0.22 μm organic filter, and then inject. Approximately 1 mL of the solution was added to an e2695 high-performance liquid chromatograph using an autosampler. The C18 column (250.0 m × 4.6 mm × 5 μm) was from Waters, and fluorescence detection was from Agilent. In pulse-on-dip split-free mode, the injection volume was 10 μL. The mobile phase was A: acetonitrile and B: ultrapure water, with a flow rate of 1.0 mL / min. The HPLC gradient elution program was as follows: 0–8 min, 60% acetonitrile; 8–28 min, acetonitrile increased from 60% to 100%; 29–35 min, acetonitrile decreased from 100% to 60%, with the column temperature maintained at 35 °C.

[0143] The contents of benzo[a]pyrene, benzo[a]anthracene, benzo[b]fluoranthracene, and chrysene in heat-treated sesame paste were determined, and the results are as follows: Figure 11 As shown in Example 2, after heating in an oven at 170°C for 20 minutes, the contents of benzo[a]pyrene and PAH4 in the sesame paste reached their maximum, at 1.45 μg / kg and 4.99 μg / kg, respectively. When the infrared power increased from 600W to 800W, the benzo[a]pyrene content increased from 1.25 μg / kg to 1.26 μg / kg, and the PAH4 content increased from 3.97 μg / kg to 4.22 μg / kg. Therefore, compared with traditional roasting, the polycyclic aromatic hydrocarbon content of the sesame paste obtained by the novel IR-MW heating method was significantly reduced, and the safety of the sesame paste was improved.

[0144] II. Determination of heterocyclic amines in sesame paste

[0145] Weigh 1g ± 0.01g of sesame paste and mix with 5mL of acetonitrile (HPLC grade). Vortex vigorously for 1 min, then extract with ultrasonic assistance for 8 min. Centrifuge at 4000 r / min for 5 min. Transfer the supernatant to a glass tube. Repeat the entire extraction process twice. Purification: Load the collected supernatant onto a PCX solid-phase extraction column pre-activated with 3mL methanol and 3mL ultrapure water at a flow rate of 1mL / min. Elute the column sequentially with 3mL of 0.1mol / L hydrochloric acid and 3mL of methanol. After rinsing, remove the remaining solution from the column using a vacuum pump. Elute with 3mL of methanol-ammonia solution (95:5v / v). Collect all eluent and dry under nitrogen at 45℃. Redissolve the dried product with 1mL of methanol, filter through a 0.22μm organic filter membrane, and then inject the sample. HPLC conditions: Waters C18 column (250.0 m × 4.6 mm × 5 μm), column temperature 30 °C, injection volume 10 μL. Mobile phase A was 10 mmol / L ammonium formate solution at pH 6.8, and mobile phase B was acetonitrile, with a volume ratio of 85:15. Chromatography time: 15 min, flow rate: 1 mL / min. Fluorescence detector conditions: excitation wavelength / emission wavelength 300 nm / 440 nm.

[0146] The contents of Harman and Norharman in heat-treated sesame paste were determined, and the results are as follows: Figure 12 As shown, compared to baking in an oven at 170℃ for 20 minutes, the Harman content of sesame paste significantly decreased by 24.27% (from 144.36 μg / kg to 109.33 μg / kg) and the Norharman content significantly decreased by 23.14% (from 235.04 μg / kg to 180.65 μg / kg) after IR-MW baking. When the infrared power increased from 600W to 800W, the Harman content increased from 109.33 μg / kg to 122.26 μg / kg and the Norharman content increased from 180.65 μg / kg to 185.56 μg / kg. Therefore, compared to traditional roasting, the heterocyclic amine content of sesame paste obtained by the novel IR-MW heating method is significantly reduced.

[0147] III. Determination of Volatile Compounds in Sesame Paste

[0148] The volatile components of sesame paste were determined using HS-SPME. First, 4 g ± 0.01 g of the treated sesame paste sample was weighed into a 25 mL headspace vial and immediately sealed with a silicone diaphragm. The vial was equilibrated in a 65℃ water bath for 25 min, and stirred with a magnetic stirrer at 80 rpm. Then, an activated divinylbenzene / carboxylic acid / polydimethylsiloxane (DVB / CAR / PDMS) fiber extraction needle (length: 2 cm; thickness: 50 / 30 μm) was inserted for extraction for 40 min. For the first use, the fiber needle was aged at 250℃ for 90 min; subsequent uses only required 30 min aging. The extracted SPME fiber was then inserted into the GC inlet (250℃), with a resolution time of 5 min, and the acquisition program was started. Gas chromatography conditions: HP-5MS capillary column (30m × 0.25mm × 0.25μm); initial temperature 35℃, then increased to 220℃ at a rate of 5℃ / min, held for 10 min, and finally increased to 250℃ at a rate of 15℃ / min, held for 8 min. Mass spectrometry conditions: ion source temperature 230℃; interface temperature 250℃; electron energy 70eV. The elution times of each compound in the sample were used to match the sample with a spectral library, and components with a matching degree greater than 80% were selected.

[0149] The volatile compound content of sesame paste is from Figure 13 , Figure 14 , Figure 15As shown in Table 3, a total of 81 volatile compounds were detected in sesame paste, including pyrazines (11), pyrroles (1), pyridines (2), furans (4), aldehydes (10), ketones (4), alcohols (11), esters (9), acids (2), hydrocarbons (19), and other compounds (8). Compared with Example 2, Comparative Example 1, and Comparative Example 2, the aldehyde, alcohol, ester, and acid contents of sesame paste prepared by IR-MW heating increased by 31.54%, 3.72%, 42.39%, and 16.95%, respectively. After heat treatment, pyrazine compounds are the most abundant volatile compounds in sesame paste. They typically exhibit roasted, bread, nutty, and cocoa aromas. Compared to oven-treated sesame paste, IR-MW800 showed an increase in the content of 3,5-dimethyl-2-pyrazine (from 1923.95 μg / kg to 1973.65 μg / kg), and also produced 2-ethyl-3,5,6-trimethylpyrazine. The contents of isovaleraldehyde, 2-methylbutyraldehyde, and phenylacetaldehyde, which are associated with umami and lipid aromas, significantly increased. The contents of trimethylpentanol, n-hexanol, and 1-octen-3-ol, which are associated with sweetness, floral, waxy, green, citrus, and fruity flavors, also significantly increased. IR-MW heat treatment produced volatile substances such as 2-ethyl-3,5,6-trimethylpyrazine, α-ethylidene-phenylacetaldehyde, methyl dihydrojasmonate, 2-buten-1-ol propionate, and n-heptanol. In Comparative Example 1, infrared (IR) radiation is a non-ionizing electromagnetic spectrum with a wavelength range of 0.75-1000 μm, located between the ultraviolet and microwave regions. During oilseed heating, the energy emitted by the infrared heater is absorbed by the internal components of the oilseed (water molecules and ions) and converted into heat energy, which is then conducted throughout the oilseed in the form of electromagnetic waves. However, long-term exposure to IR radiation can cause changes in the material's own structure. In Comparative Example 2, microwave (MW) energy enters the oilseed in the form of electromagnetic radiation, generating a large amount of water vapor from the inside out, forming an effective vapor pressure gradient that drives moisture to migrate to the surface. The polar structure of the internal water molecules vibrates at high frequency under microwave action, resulting in a huge frictional effect and thermal motion, causing rapid moisture loss. However, microwave heating can easily cause uneven heating and lead to the formation of oxygen-containing compounds and fatty acid conjugates, reducing oil stability and accelerating oil rancidity.

[0150] Table 3. Effect of heat treatment on the volatile compound content of sesame paste.

[0151]

[0152]

[0153] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the invention. Those skilled in the art will understand that implementing all or part of the above-described embodiments and making equivalent changes in accordance with the claims of the present invention are still within the scope of the invention.

Claims

1. A method for preparing sesame paste, characterized in that, Includes the following steps: S1 Pretreatment: Select white sesame seeds, wash and dry them to remove impurities, and obtain raw white sesame seeds; S2 Heating: Spread the raw white sesame seeds evenly on a baking tray, with a thickness of no more than 4mm, and bake at 170℃ for 20 minutes to obtain roasted sesame seeds; S3 Smoke Removal: Cool the roasted sesame seeds to below 60℃ and remove the debris to obtain the roasted sesame seeds to be ground; S4 Grinding: Grind the cooked sesame seeds to be ground into a median diameter of 74μm-76μm using a grinding device to obtain sesame paste; S5 Bottling: Bottle the resulting sesame paste.

2. The method for preparing sesame paste as described in claim 1, characterized in that, In the S5 bottling process, the bottling containers used must be cleaned and sterilized at high temperature before use.

3. The method for preparing sesame paste as described in claim 1, characterized in that, In the S1 pretreatment, the white sesame seeds are plump, free of mold, and have an intact appearance.

4. Sesame paste prepared by the method for preparing sesame paste according to claim 1.

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