Method for obtaining high-oxidation-resistance sesame grease body through microwave pretreatment and application of high-oxidation-resistance sesame grease body

Abstract

The invention discloses a method for obtaining a high-oxidation-resistance sesame grease body through microwave pretreatment and application of the high-oxidation-resistance sesame grease body. The method comprises the following steps: carrying out microwave pretreatment on a sesame raw material at the power of 700W for 5-12min, pulping, centrifuging and washing. According to the method, through accurate regulation and control, moderate modification of interface protein is realized, so that the interface protein content (such as 7min: 90.08%) of the oil body is kept at a functional level after the oil body is treated for 5-12min, the emulsion stability (ESI) is optimized, and the elasticity (storage modulus G ') of an interface film is remarkably enhanced. Meanwhile, the method efficiently activates an endogenous anti-oxidation system, and after accelerated oxidation of a 5-min pretreatment group for 20 days, the peroxidation value (PV), the thiobarbituric acid value (TBARS) and the carbonyl value increase the slowest, the sulfydryl is retained to the maximum, and excellent oxidation stability is shown. The obtained sesame oil body is an excellent natural embedding medium and can be widely applied to food systems such as seasoning sauce and dairy products.

Description

Technical Field

[0001] This invention belongs to the field of food processing technology, and specifically relates to a method for obtaining highly antioxidant sesame oil by microwave pretreatment. Background Technology

[0002] Oil bodies (OBs) are natural, pre-emulsified oil-in-water (O / W) emulsions in which triglycerides are encapsulated by a monolayer of phospholipids and embedded membrane proteins. OB emulsions have attracted significant attention in the development of sustainable and healthy foods due to their green, natural, and readily available characteristics.

[0003] Sesame oil bodies, unlike sesame oil, consist of fat globule membranes encapsulating sesame oil. The outer layer of these oil bodies is an interfacial membrane, primarily composed of interfacial proteins. Sesame oil is encapsulated within this membrane. Sesame oil bodies not only possess the properties of oils but also the emulsifying properties of interfacial membranes. Based on their combined antioxidant and emulsifying characteristics, they can be widely used in food systems such as sauces, baking oils, dairy products, beverages, and functional snacks.

[0004] Existing technologies for sesame oil extraction have yielded numerous publications detailing methods to obtain sesame oil with enhanced antioxidant properties. However, few publications disclose extraction processes for sesame oil bodies, which consist of an outer interfacial membrane composed of interfacial proteins and an inner layer encapsulating sesame oil. Given that the structure of sesame oil bodies differs significantly from that of sesame oil, the factors influencing their antioxidant and emulsifying properties during the extraction process remain unknown and are currently undocumented in the literature.

[0005] Therefore, it is necessary to explore and analyze the factors affecting the antioxidant properties of sesame oil bodies, and to invent a method to obtain sesame oil bodies with excellent antioxidant properties. Summary of the Invention

[0006] To solve the above technical problems, this invention uses natural antioxidant components such as lignans and sesamol in sesame raw materials as evaluation indicators, and microwave pretreatment as the core processing scheme, and finally obtains sesame oil with excellent antioxidant properties.

[0007] The sesame oil body of the present invention is obtained through the following steps: (1) Microwave pretreatment: Take sesame raw materials and pretreat them with microwave power of 700W and microwave treatment time of 5~12 min; (2) Oil extraction: The sesame raw material that has been microwave pretreated in (1) is immediately mixed with cold water at 5~25℃, pulped, enzymatically hydrolyzed with compound enzyme, filtered, centrifuged, the upper layer of material is collected and washed to obtain sesame oil. The above-mentioned compound enzyme is cellulase and pectinase in a ratio of 1:1, and the amount of compound enzyme added is 1% to 3% of the weight of solids.

[0008] Preferably, (1) the microwave pretreatment time is 7 min or 5 min.

[0009] Preferably, in (2), centrifugation is performed at a speed of 8000 r / min for 15 min.

[0010] Preferably, in (2), the amount of the compound enzyme added is 2% of the weight of the solids.

[0011] Preferably, in (2), the conditions for enzymatic hydrolysis are: 50℃, 1h, without the need for high-temperature enzyme inactivation.

[0012] Preferably, the washing in (2) involves washing with deionized water 2 to 4 times.

[0013] Preferably, in (2), filtration is performed using a 100-200 mesh sieve.

[0014] Preferably, the method for obtaining highly antioxidant sesame oil bodies through microwave pretreatment includes the following steps: (1) Microwave pretreatment: Take sesame raw materials and pretreat them with microwave power of 700W and microwave treatment time of 0, 2, 5, 7, 10, 12 and 15 min. (2) Oil extraction: The sesame raw material that has been microwave pretreated in (1) is immediately mixed with cold water at 5~25℃, pulped, enzymatically hydrolyzed with compound enzyme, filtered, centrifuged at 8000r / min for 15min, the upper layer is collected and washed 3 times to obtain sesame oil. The compound enzyme is composed of cellulase and pectinase in a 1:1 ratio, and the amount of compound enzyme added is 2% of the weight of solids.

[0015] This application also includes the use of sesame oil bodies obtained by the above method as embedding agents.

[0016] And the application of sesame oil obtained by the above method in sauces, baking oils, dairy products, beverages and functional snacks.

[0017] The beneficial effects of this invention are as follows: (1) It simultaneously improves the oxidative stability and emulsifying ability of sesame oil. This application demonstrates that microwave pretreatment of sesame raw materials at 700W for 7 minutes resulted in a high ESI (emulsion stability) value. Furthermore, peroxide value detection at 5 minutes and 7 minutes also indicates that the formation of peroxides in the early stages of oil oxidation can be effectively delayed at these two treatment times. (2) Interfacial tension The results of interfacial tension measurement showed that microwave pretreatment at 700W for 7 min promoted cell rupture, which released phospholipids, free fatty acids and small polar molecules into the oil phase and enriched them at the oil / water interface, thereby increasing the concentration of surfactants, rapidly reducing interfacial tension and accelerating adsorption kinetics. (3) High content of lignans and sesamin When microwave pretreatment lasts for 5 or 7 minutes, sesamin, which was originally embedded or bound to the cell wall / macromolecule, is more easily released. Lignans exist in plants as glycosides or in combination with other components. Moderate heating can cause glycosylation or bond breakage, which leads to a significant increase in lignan levels in a short period of time.

[0018] (4) The sesame oil obtained by the present invention has excellent emulsification stability and oxidative stability. As a natural encapsulating agent or fat substitute, it can be widely used in the fields of seasoning sauce, baking oil, dairy products, beverages and functional snacks to improve product quality and health attributes. Attached Figure Description

[0019] Figure 1 The changes in emulsifying activity and emulsifying stability over treatment time; Figure 2 The SDS-PAGE spectra of sesame raw materials after pretreatment with microwave at 700 W for different durations are shown; from right to left, they are maker, 0, 2, 5, 7, 10, 12, and 15 min. Figure 3 The change in hydrophobicity (H0) of the oil surface over time; Figure 4 The effect of different microwave pretreatment times at 700 W on surface tension (SFT); Figure 5 The trends of energy storage modulus (G') and loss modulus (G'') with increasing angular frequency are shown. Figure 6 This describes the regular evolution of the lipid core-intact protein interface membrane under CLSM double staining technique with prolonged microwave time. Figure 7 The changes in the contents of sesamin, sesamin, and sesamol in the oil over time; Figure 8 The changes in the total amount of lignans in sesame oil from 0 to 7 minutes, and the conversion relationship between the contents of sesamin and sesamol; Figure 9 The trend of peroxide value (PV) changes with increasing oxidation time for each pretreatment time group; Figure 10The trend of thiobarbituric acid (TBARS) values ​​for each pretreatment time group as oxidation time increases; Figure 11 The trend of carbonyl value change with increasing oxidation time for each pretreatment time group; Figure 12 The trend of thiol value changes with increasing oxidation time for each pretreatment time group. Detailed Implementation

[0020] To enable those skilled in the art to better understand the present invention, the present invention will now be further described in conjunction with specific embodiments.

[0021] Example 1 A method for obtaining highly antioxidant sesame oil bodies through microwave pretreatment includes the following steps: (1) Microwave pretreatment: Take sesame raw materials and pretreat them with microwave power of 700W and microwave treatment time of 0, 2, 5, 7, 10, 12 and 15 min. (2) Oil extraction: The sesame raw material that has been microwave pretreated in (1) is immediately mixed with cold water at 5~25℃, pulped, and enzymatically hydrolyzed with a compound enzyme (the compound enzyme is cellulase and pectinase, the ratio of the two is 1:1, and the amount of compound enzyme added is 2% of the weight of solids). The mixture is filtered through a 100~200 mesh sieve, centrifuged at 8000r / min for 15min, the upper layer is collected and washed 3 times to obtain sesame oil.

[0022] Example 2 Determination of interfacial protein concentrations in lipid bodies under different microwave treatment times The method for determining the interfacial protein concentration of an emulsion is as follows: The emulsion is centrifuged at 12000 rpm and 4 °C for 1 h. Serum (substrate phase) is collected using a syringe and filtered through a 0.45 μm filter to determine the content of unadsorbed (substrate phase) proteins. W 血清 The obtained OB (oil-based) cream was defatted twice with acetone, and then centrifuged at 10,000 rpm and -20 °C for 15 min to remove organic solvents. The defatted sample was then lyophilized, and the residue was dissolved in deionized water. The protein content in serum and OBs, and the total protein content of the OB cream were then determined using a Bradford protein assay kit. W 总 g).

[0023] The formula for calculating the content of interfacial proteins is as follows: Interface protein content (%) = ( W 总 — W血清 ) / W 总 Under a fixed microwave power of 700 W, the interfacial protein content of sesame oil showed a continuous decreasing trend, indicating that microwave pretreatment significantly weakened the stability of the oil interface within this time range. Microwave heating mainly generates heat by exciting the high-frequency vibration of polar molecules such as water molecules. Protein molecules also have a certain polarity. Under microwave action, their molecular structure may vibrate and rotate. As the heating time increases, energy accumulates, causing the spatial structure of the protein to gradually unfold and denature. The distribution of hydrophobic and hydrophilic groups in the denatured protein changes, making it unable to stably bind to the oil interface, thus detaching from the interface and reducing the interfacial protein content. Microwave heating causes rapid evaporation of water in sesame seeds. Studies have shown that increasing microwave power reduces the water content of sesame seeds. Water is an important factor in maintaining protein structural stability. Water loss disrupts the hydration layer around the protein, altering the interactions between protein molecules, leading to protein structural instability and easy detachment from the oil interface, ultimately resulting in a decrease in interfacial protein content.

[0024] Table 1. Interface protein content under various microwave pretreatment durations. 700W microwave time (min) Interface protein content (%) 0 93.14±0.38 2 92.13±0.29 5 91.43±0.13 7 90.08±0.76 10 89.20±0.21 12 88.42±0.40 15 85.81±0.11

[0025] Example 3 Determining the emulsifying ability of sesame oil bodies Mix 1g of oil with 9g of deionized water until completely dissolved. Take 8mL of the sample dilution and mix it with 2mL of soybean oil. Then homogenize at 2000r / min for 1min to obtain an emulsion. Take 200μL of the bottom emulsion that has been pretreated for 0min and 30min respectively and add it to 10mL of 1% SDS solution, and mix thoroughly. Then, after vortexing, measure the absorbance at 500nm using a UV-Vis spectrophotometer. The absorbance measured at 0min is recorded as A0, and the absorbance measured again after 30min is recorded as A0. 30 The calculation formula is as follows: (1) (2)

[0026] After pretreatment of sesame raw materials with microwave at 700 W for 0, 2, 5, 7, 10, 12, and 15 min, see [the results]. Figure 1 ,and Figure 1 The corresponding data is shown in Table 2 below: Table 2. EAI and ESI values ​​of sesame oil liposomes under different microwave pretreatment times. Processing time (min) <![CDATA[EAI(m 2 / g)]]> ESI (min) 0 59.77±2.12 70.82±2.81 2 51.6±1.37 63.39±1.14 5 46.01±0.85 63.53±1.76 7 34.4±2.45 68.82±0.63 10 37.84±1.93 49.42±2.24 12 35.26±2.67 47.67±1.49 15 30.1±0.52 50.73±2.58

[0027] pass Figure 1 It can be observed that EAI continuously decreases over time, while ESI shows a pattern of first high, then low, and then slightly rebounding. This is consistent with the combined effects of microwave thermo-mechanical modification of interfacial proteins and the physical properties of oil droplets: the rapid local heating and electromagnetic vibration generated by microwaves cause interfacial proteins (such as oleosins) on the oil surface to partially unfold, expose hydrophobic groups, and further irreversibly aggregate or precipitate, resulting in a decrease in the amount of functional proteins that can participate in interface formation. Therefore, EAI decreases significantly with prolonged treatment time. EAI, or emulsifying activity, reflects the ability of proteins to adsorb and form interfaces in a short time. At the same time, mild treatment (short time 2-7 min) may enhance the coverage density and interaction of proteins at the interface by moderately unfolding them, thereby temporarily increasing or maintaining ESI, or emulsifying stability. However, with deeper treatment (10-12 min), proteins further denature, forming large molecular aggregates, increasing the rupture of the interfacial film or the coalescence of oil droplets, and decreasing the interfacial mechanical strength and charge stability, leading to a significant decrease in ESI. ESI appears under longer treatment (15 min). A slight increase in ESI could be due to the formation of polymer aggregates at the interface by a different mechanism that hinders coalescence, or to droplet size rearrangement (changing the surface area / protein demand ratio), but its stabilization mechanism is different from the original protein adsorption membrane. In summary, the decrease in EAI is mainly attributed to the loss or reduced accessibility of functional interface proteins, while the complex changes in ESI reflect the dynamic reconstruction of interface membrane properties under the combined influence of protein conformation, solubility, aggregation behavior, and droplet size or surface charge.

[0028] Example 4 Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) The method for separating proteins adsorbed at the oil / water interface is as follows: A protein sample (45 μL) was mixed with either a non-reducing (β-mercaptoethanol-free) buffer (15 μL) or a reducing (β-mercaptoethanol-containing) buffer (15 μL), and the mixture was heated in a water bath at 100 °C for 5 minutes. Electrophoresis was performed using a 12% stacking gel and a 5% separating gel at 80 V and 120 V, respectively. The molecular weight range of the labeled proteins was (15 ~ 130) kDa. After electrophoresis, the gel was stained with 0.25% Coomassie Brilliant Blue R-250 for 30 min, destained using a methanol:acetic acid:water mixture (1:1:8, v / v / v), and photographed using a gel imaging system to view the protein bands. Band intensity was analyzed using ImageLab v3.0 software.

[0029] SDS-PAGE spectra of sesame raw materials after pretreatment at 700 W microwave for 0, 2, 5, 7, 10, 12, and 15 min are shown below. Figure 2 The SDS-PAGE spectra of sesame raw materials after different pretreatment times under 700 W microwave treatment are shown. From right to left, they are maker, 0, 2, 5, 7, 10, 12, and 15 min. In the short-time treatment (2~7 min), the intensity of most typical oil body interface protein bands in the samples remained or slightly redistributed. However, in the medium and long-time treatment (10~15 min), the intensity of some medium and low molecular weight bands decreased, the relative increase of low molecular weight fragments and the appearance of blurred / tailed high molecular weight signals at the upper end of the lanes were observed. This is because the rapid localized heating caused by microwaves and the electromagnetic field effect induce conformational unfolding of interfacial proteins (such as oleosin-like proteins) and expose hydrophobic groups. Short-term partial unfolding facilitates protein re-adsorption at the oil / water interface and the formation of a dense coating (corresponding to the short-term maintenance or increase of ESI). However, as the treatment time increases, the increased exposed hydrophobic regions lead to enhanced hydrophobic interactions between protein molecules, resulting in irreversible nonvalent aggregation or the formation of high molecular weight aggregates through disulfide bond crosslinking. These aggregates may also not completely depolymerize under reducing SDS treatment, thus appearing as medium-molecular-weight bands with tailing at the top or disappearing on the gel. At the same time, the decrease in the amount of soluble functional proteins leads to the weakening of low / medium molecular weight bands (corresponding to the continuous decrease in ESI). In addition, prolonged heat treatment may also activate endogenous proteases or cause non-enzymatic thermal degradation, producing more low molecular weight fragmentation products, explaining the relative enhancement of low molecular weight bands in long-term samples.

[0030] Example 5 Surface hydrophobicity The method for determining surface hydrophobicity is as follows: 1 g of OBs is uniformly dispersed in 9 g of TrisHCl buffer (10 mmol / L). -1 In (pH=7.0). Using PBS solution (10 mmol / L). -1 (pH=7) OBs were diluted to 0.25%, 0.50%, 1.00%, 1.50%, and 2.00% (w / v), 20 mL each time, and 200 μL of ANS fluorescent probe (8 mmol / L) was added. The solutions were mixed thoroughly and allowed to stand in the dark for 15 min. Fluorescence intensity was measured using a fluorescence spectrophotometer. Experimental conditions were: excitation wavelength 390 nm, emission wavelength 470 nm, excitation unit slit 5 nm, emission unit slit 5 nm, and negative voltage of the photovoltaic cell 600 V. Fluorescence intensity was plotted on the ordinate, and sample protein concentration on the abscissa. The initial slope was recorded as the H0 value of the sample. Data and trends are shown in Table 3 and [Table data would be inserted here]. Figure 3 As shown.

[0031] Table 3. Changes in hydrophobicity (H0) of oil surface with treatment time Time (min) <![CDATA[H0 value]]> 0 2124.6±8.55 2 2023.6±12.77 5 1906.8±5.38 7 1793.2±10.28 10 1830.7±3.67 12 1672.4±14.70 15 1323.5±7.42

[0032] Depend on Figure 3 It can be seen that as the time increased from 0 min to 15 min, the hydrophobicity (H0) of the oil surface showed a continuous decreasing trend. This is because the microwave thermal effect denatures proteins. The initial short-time treatment leads to structural changes in some heat-sensitive proteins and a reduction in the exposure of hydrophobic groups. Although the later long-time treatment promotes the release of internal hydrophobic proteins, excessive protein denaturation and intermolecular aggregation "mask" the hydrophobic groups. At the same time, electrophoresis shows that the protein composition changes with the treatment time. Low molecular weight proteins participate in polymerization and other reactions, which further affects the degree of exposure of hydrophobic groups. Ultimately, the number of hydrophobic sites for binding between the oil and the ANS probe decreases, and H0 decreases. Meanwhile, the emulsifying activity (EAI) gradually weakens as H0 decreases, and the emulsifying stability (ESI) shows a dynamic change of first decreasing, then increasing, and then decreasing again. That is, microwaves affect the hydrophobicity and emulsifying properties of the oil surface by regulating protein conformation, composition, and interfacial behavior.

[0033] Example 6 Dynamic Interface Tension The defatted protein was dissolved in PBS (aqueous phase) and placed in a syringe, while soybean oil (oil phase) was placed in a cuvette. Then, 10 μL of the protein solution was transferred to the cuvette, and the contact angle was measured using an OCA25 optical contact angle meter, which was used to calculate the interfacial tension according to the Young-Laplace equation.

[0034] Microwave pretreatment of sesame raw materials at 700 W showed a clear time dependence, such as... Figure 4 The effect of different microwave pretreatment times at 700 W on surface tension (SFT).

[0035] Depend on Figure 4 It is evident that short to moderate time intervals (2–10 min) promote cell rupture, releasing phospholipids, free fatty acids, and small polar molecule adjuvants into the oil phase and enriching them at the oil / water interface, thereby increasing the surfactant concentration, rapidly reducing interfacial tension, and accelerating adsorption kinetics. However, excessively long time intervals (12–15 min) lead to thermal degradation, oxidation, or chemical modification (such as polymerization, cross-linking, or increased hydrophilicity) of these surfactant components due to localized high temperatures. This may also increase the amount of high molecular weight or polymerization byproducts in the oil phase, increase viscosity, and restrict diffusion, resulting in a reduction in the effective components available for interfacial adsorption. This manifests as increased interfacial tension and slower decay.

[0036] Example 7 rheology The prepared OBs were placed in the parallel plate of the dynamic rheometer. Excess sample was scraped off, and the surrounding area was sealed with liquid paraffin to prevent moisture loss. The sample was first equilibrated at 25 °C for 60 s to allow it to stabilize before measurement. A PP50 probe was used, with a 1 mm gap between the probe and the parallel plate and a parallel plate diameter of 80 mm. The angular frequency scan ranged from 100 rad / s to 0.1 rad / s, the strain value was set to 1%, and 16 data points were set within the linear viscoelastic region. The viscosity scan was performed at shear rates from 0.1 to 100 s⁻¹. -1 31 data points are set.

[0037] Depend on Figure 5 The rheological behavior of sesame OBs is significantly influenced by the composition of interfacial proteins and the structure of the OBs. The viscoelasticity of sesame OBs can be characterized by storage modulus (G') and loss modulus (G''). Within the angular frequency range of this study, the G' of the oil body from 0 to 12 min was consistently greater than G'', indicating that the OBs system is stable and predominantly elastic; both G' and G'' showed an increasing trend with increasing angular frequency. However, at the 15 min mark, the oil body exhibited instability with G' being less than G'' at the end. At the equivalent angular frequency, the G' and G'' values ​​of microwave-treated samples (except for the 15 min sample) were significantly higher than those of untreated samples. A possible explanation for this phenomenon is that microwave treatment leads to cross-linking and aggregation of interfacial proteins, transforming the viscous colloidal network structure into an elastic colloidal network structure, thereby enhancing the elasticity of the OBs.

[0038] Example 8 To investigate the aggregation changes of sesame oil bodies, CLSM observation was performed using laser confocal microscopy. Peanut OBs were stained with Nile red (0.1%, w / v) and FITC (1%, w / v) dissolved in propanol for 30 min. After staining, 10 μL of the emulsion was placed on a glass slide, and the microstructure of the OBs was observed using CLSM at an excitation wavelength of 488 nm.

[0039] This study used CLSM double staining technique to visually reveal the decisive influence of microwave treatment on the microstructure of sesame oil. Figure 6The results show that the untreated oil body exhibits a typical "lipid core-intact protein interface membrane" structure, corresponding to excellent initial emulsifying properties. With prolonged microwave treatment, this structure undergoes a regular evolution: short-term treatment (2-5 min) leads to partial dissociation of the interface proteins, but the structural framework remains intact, and stability is maintained; medium-term treatment (7-10 min) causes significant defects in the interface membrane and protein aggregation, leading to a deterioration in emulsifying function; long-term treatment (12-15 min) causes complete collapse of the oil body structure, forming lipid aggregates and severely losing emulsifying properties. The 5-min treatment is a critical point where beneficial structural reorganization occurs without severe damage, providing a microstructural explanation for maintaining both good emulsifying properties and optimal antioxidant stability.

[0040] Example 9 Lignin content The content of lignans in sesame oil and sesame oil was determined according to NY / T 1595-2008 "Determination of sesamin content in sesame by high performance liquid chromatography".

[0041] Microwave heating absorbs energy through polar water molecules, inducing rapid rupture of cell walls and intercellular structures, and enhancing the migration of intracellular secondary metabolites (such as lignans) to the solvent or oil phase. Therefore, within a short to moderate time (2-7 min), sesamins that were originally embedded or bound to the cell wall / macromolecules are more easily released. Moreover, lignans exist in plants in the form of glycosides or bound to other components. Moderate heating can cause glycosylation or bond breakage. These factors lead to a significant increase in lignan levels in a short period of time.

[0042] With further extension of processing time, lignans may undergo thermal degradation, oxidation, or reactions with other groups (polymerization, condensation), resulting in a decrease or stagnation of the measurable free lignan content. Existing studies have shown that sesamin can be converted to sesamol at high temperatures, which confirms this. Figure 7 Changes in sesamin and sesamol after 5 minutes.

[0043] From sesame oil Figure 8 The study revealed changes in the total amount of lignans in sesame. From 0-7 minutes, the conversion relationship between sesamin and sesamol was observed, with increases or decreases in sesamol accompanied by decreases or increases in sesamin. However, after 10 minutes, the prolonged heating time caused the decomposition of lignans.

[0044] Example 10 1. Emulsion oxidation 1.1 Peroxide value The emulsion (0.2 mL) was mixed with an organic solvent (isopropanol:isooctane = 1:3 v / v, 10 mL), vortexed for 10 s, and then centrifuged (6000 rpm, 15 min). The upper organic phase (i.e., the oil phase, 200 μL) was mixed with a mixture of methanol and n-butanol (2:1 v / v, 2.8 mL). Subsequently, ammonium thiocyanate solution (3.94 M, 15 μL) and Fe... 2+ A solution (15 μL, obtained by mixing equal volumes of 0.132 M BaCl2 and 0.144 M FeSO4) was added to the mixed sample and rotated uniformly. The sample was incubated in the dark for 20 min, and then the absorbance at 510 nm was measured. A standard curve was constructed using cumene hydroperoxide, and the fitting equation was as follows: y = 0.0115 x- 0.0352 ( y = Absorbance, x = Hydrogen peroxide concentration (M), R 2 = 0.994).

[0045] Peroxide value (PV) is an important indicator for measuring the peroxide content in oils and fats. Peroxides are the main products in the early stages of oil and fat oxidation, and changes in their content can reflect the initial stage of oil and fat oxidation. Figure 9 The peroxide value (PV) trends for each pretreatment time group with prolonged accelerated oxidation time show that the PV values ​​of all pretreatment time groups increase with the extension of accelerated oxidation time. This is because the oil oxidation reaction continues, and peroxides are continuously generated. Among them, the PV value of the 5-min microwave pretreatment group increased the slowest, and its PV value was significantly lower than other groups at the end of the 20-day accelerated oxidation. The PV value of the 10-min group increased the fastest and reached the highest value. This indicates that 5-min microwave pretreatment can effectively delay the generation of peroxides in the early stage of oil oxidation, while 10-min pretreatment may be due to overtreatment, destroying the natural antioxidant components in sesame raw materials or making the oil structure more susceptible to oxidative attack, leading to an accelerated peroxide generation rate. This fully demonstrates the antioxidant advantage of the 5-min pretreatment group in the early stage of oxidation.

[0046] 1.2 Thiobarbituric acid value (TBAR) The TBAR value experiment method is as follows: Mix the emulsion and thiobarbituric acid solution at a ratio of 1:2, transfer to a test tube, incubate in a 100°C water bath for 15 min, and centrifuge at 3000 rpm for 15 min. Measure the absorbance at 532 nm. Establish a standard equation using 1,1,3,3-tetraethoxypropane as the standard. y =0.0397 x + 0.0338 (R) 2= 0.9998), where y is the absorbance and x is the concentration of thiobarbituric acid (M).

[0047] The TBARS value is used to characterize the content of aldehydes such as malondialdehyde during the oxidation of fats and oils. Aldehydes are products of the later stages of fat and oil oxidation, and changes in their content reflect the depth of fat and oil oxidation. Figure 10 The trend graph of thiobarbituric acid (TBARS) values ​​for each pretreatment time group with increasing oxidation time shows that the TBARS values ​​of each experimental group generally show a trend of first increasing and then decreasing (or stabilizing) with increasing oxidation time. This is related to the initial formation of aldehydes during the oxidation process, followed by possible further decomposition or polymerization. The TBARS value of the 5-min microwave pretreatment group showed the smallest increase and the lowest peak value throughout the entire oxidation cycle; the 10-min group showed the largest increase and the highest peak value. This indicates that the 5-min pretreatment can effectively inhibit the formation of aldehydes in the later stages of oil oxidation and reduce the degree of deep oxidation, while the 10-min pretreatment makes the oil more prone to deep oxidation, further verifying the superiority of the 5-min pretreatment group in inhibiting deep oxidation of oils.

[0048] 1.3 Carbonyl content To determine the carbonyl content in the protein, specifically, DNPH (10 mM, 2 mL) was added to the sample (0.4 mL) and stirred for 1 h. Trichloroacetic acid (20% w / v, 2 mL) was then added and mixed thoroughly, and the precipitate was collected by centrifugation at 4 °C (12000 rpm, 15 min). The precipitate was washed three times with a mixture of ethanol and ethyl acetate (1:1 v / v, 4 mL each time). The precipitate was then dissolved in guanidine hydrochloride (6 M, 4 mL) and incubated at 37 °C for 15 min, followed by absorbance measurement at 370 nm. Carbonyl content (nmol) was determined. C=O / mg 可溶性蛋白 Using 22000 M -1 cm -1 The molar extinction coefficient was determined.

[0049] The carbonyl value is a measure of the carbonyl compounds formed after the oxidative breakdown of fatty acids during the oxidation of fats and oils. The formation of carbonyl compounds indicates the further development of fat and oil oxidation. From Figure 11The carbonyl value changes of each pretreatment time group with increasing oxidation time are shown in the graph. As the accelerated oxidation time increases, the carbonyl value of each experimental group gradually increases. The carbonyl value of the 5-min microwave pretreatment group increases significantly slower than the other groups, and after 20 days of oxidation, its carbonyl value is much lower than that of the other groups. The 7-min group shows the most rapid increase in carbonyl value, and also has the highest final value. This means that 5-min microwave pretreatment can effectively inhibit the process of fatty acid oxidation and the formation of carbonyl compounds, while 7-min pretreatment promotes this process, reflecting that 5-min pretreatment has a more significant inhibitory effect on the formation of carbonyl compounds during lipid oxidation.

[0050] 1.4 Thiol content The method for determining the thiol content is as follows. To prepare the Tris-Gly-urea solution, 2-nitrobenzoic acid (DTNB) solution (4 mg / mL, 0.02 mL) was added to a premixed solution of 10.4 g Tris, 6.9 g Gly, 1.2 g EDTA, and 480 g urea dissolved in deionized water. The solution was adjusted to a final volume of 1000 mL and a pH of 8.0. Then, the sample (1.0 mL) was mixed with 5.0 mL of Tris-Gly-urea solution and incubated at 25 °C for 30 min. The absorbance of the sample was then measured at 412 nm using a UV spectrophotometer. The thiol content (nmol) was then determined. 硫醇 / mg 蛋白 Using 13600M -1 cm -1 The molar extinction coefficient was determined.

[0051] The thiol group (-SH) has antioxidant properties in oil and fat systems, and its decrease is usually related to oil oxidation and the consumption of antioxidants. Figure 12 The graph showing changes in thiol values ​​reveals that the thiol values ​​in all experimental groups decreased over time with accelerated oxidation. This is because thiol groups either participated in the antioxidant reaction or were consumed by oxidation. The 5-min microwave pretreatment group exhibited the smallest decrease in thiol value, retaining a relatively large number of thiol groups even after 20 days of oxidation. The 10-min group showed the largest decrease in thiol value, with the least amount of remaining thiol groups. This indicates that the 5-min microwave pretreatment better preserves the antioxidant thiol groups in the sesame raw material, allowing them to continue exerting their antioxidant effects. In contrast, the 10-min pretreatment resulted in a significant consumption of thiol groups, weakening the antioxidant capacity. This further demonstrates the advantage of the 5-min pretreatment group in maintaining antioxidant substances.

[0052] At a fixed power of 700W, the effect of microwave pretreatment time on the oxidative stability of sesame oil is not linear, but rather exhibits a range of 5–12 min, particularly 5 min and 7 min. Pretreatment at these time points most effectively delays oil oxidation; the 5 min pretreatment group showed the smallest increase and lowest peak value in TBARS (a measure of aldehyde secondary oxidation products) and carbonyl value (a measure of fatty acid cleavage products) throughout the oxidation cycle. This demonstrates that the present invention not only inhibits the initiation of oxidation but also effectively prevents deep oxidation of the oil, preserving flavor and safety.

Claims

1. A method of obtaining high-oxidative-stability sesame oil bodies by microwave pretreatment, characterized by, It comprises the following steps: (1) Microwave pretreatment: take sesame raw materials, microwave pretreat them, microwave power is 700W, microwave treatment time is 5-12min; (2) Oil body extraction: immediately mix the sesame raw materials after microwave pretreatment in (1) with cold water of 5-25℃, beat pulp, add compound enzyme to hydrolyze, filter, centrifuge, collect the upper material and wash to obtain sesame oil body; The compound enzyme is cellulase and pectinase, the ratio of the two is 1:1, and the added amount of compound enzyme is 1%-3% of the weight of solid.

2. The method of claim 1, wherein the high-oxidative-stability sesame oil is obtained by the microwave pretreatment. (1) The microwave pretreatment time is 5min or 7min.

3. The method of claim 1, wherein the high-oxidative-stability sesame oil is obtained by the microwave pretreatment. (2) In (2), centrifuge at a speed of 8000r / min for 15min.

4. The method of claim 1, wherein the high-oxidative-stability sesame oil is obtained by the microwave pretreatment. (2) In (2), the added amount of compound enzyme is 2% of the weight of solid.

5. The method of claim 1, wherein the high-oxidative-stability sesame oil is obtained by the microwave pretreatment. (2) In (2), the enzyme hydrolysis condition is: 50℃, 1h, and no high-temperature enzyme inactivation is needed.

6. The method of claim 1, wherein the high-oxidative-stability sesame oil is obtained by the microwave pretreatment. The washing in (2) is washing 2-4 times with deionized water.

7. The method of claim 1, wherein the high-oxidative-stability sesame oil is obtained by the microwave pretreatment. The filtration in (2) is filtration with a 100-200 mesh screen.

8. A method of obtaining high-oxidative stability of sesame oil body by microwave pretreatment, characterized by, It comprises the following steps: (1) Microwave pretreatment: take sesame raw materials, microwave pretreat them, microwave power is 700W, microwave treatment time is 0, 2, 5, 7, 10, 12, 15min; (2) Oil body extraction: immediately mix the sesame raw materials after microwave pretreatment in (1) with cold water of 5-25℃, beat pulp, add compound enzyme to hydrolyze, filter, centrifuge at a speed of 8000r / min for 15min, collect the upper material and wash 3 times to obtain sesame oil body; The compound enzyme is cellulase and pectinase, the ratio of the two is 1:1, and the added amount of compound enzyme is 2% of the weight of solid.

9. Application of sesame oil body obtained by the method of claim 1 as an embedding agent.

10. Application of sesame oil body obtained by the method of claim 1 in seasoning sauce, baking oil, dairy products, beverages and functional snacks.

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