A process for the expression of plant edible oil with retention of nutrients

Abstract

The application discloses a kind of plant edible oil pressing nutrition retention process, belong to plant oil processing technical field.The process includes: placing oil material in inert gas and carrying out oxygen barrier conditioning;Adopting infrared and microwave synergic treatment makes lipase and lipoxygenase inactivation and wall breaking;In inert gas protection, suitable temperature presses and extremely fast cooling;Enzymatic degumming;Low-temperature bleaching;Add tea polyphenol palmitate, tocopherol and phospholipid ternary complex in bleaching oil, form micro-micelle slow-release shield by high-speed shearing;Double-temperature short-time deodorization;Nitrogen filling is filled after winterization dewaxing.The application is through oxygen barrier multi-physical field enzyme inactivation, slow-release shield front protection and the system cooperation of double-temperature short-time deodorization, while ensuring the depth of refining, significantly improves the retention rate of tocopherol and sterol, inhibits the generation of trans fatty acid and 3-chloropropanol ester, realizes the unity of nutrition retention and safety control.

Description

Technical Field

[0001] This invention relates to the field of vegetable oil processing technology, and in particular to a process for preserving nutrients during the pressing of edible vegetable oils. Background Technology

[0002] Vegetable oils are an important source of dietary lipids for humans. Oilseeds are naturally rich in functional active ingredients such as phytosterols, tocopherols, polyphenols, and carotenoids, which play a positive role in maintaining human physiological functions. However, the fat-soluble active substances in vegetable oils are highly sensitive to heat and oxygen, and processing parameters directly affect their retention in the finished oil.

[0003] Currently, the mainstream industrial production of vegetable oils relies on high-temperature pressing combined with chemical refining. While high-temperature treatment can increase oil yield and produce finished oils with pure flavor, it also results in significant nutrient loss. During the pressing process, high-temperature pretreatment easily leads to the degradation of heat-sensitive nutrients such as vitamin E and sterols; nearly half of the active ingredients in traditional processing are destroyed during the pretreatment stage. In hot pressing, the activity of lipoxygenase in the oilseeds briefly surges within the medium-temperature range. If oxygen-barrier measures are not taken, the instantaneously generated free radicals will cause a sharp increase in the initial oxidation value of the crude oil. In the refining process, although the extremely high temperature and long dwell time of the traditional deodorization process can remove odors, it greatly damages nutrients such as tocopherols and generates a large amount of harmful byproducts such as trans fatty acids and 3-chloropropanol esters, making it difficult to balance product nutrition and safety.

[0004] To mitigate heat damage, low-temperature cold pressing technology emerged. However, cold-pressed oils, because they do not undergo high-temperature enzyme inactivation, have high residual activity of lipases and lipoxygenases, making them highly susceptible to hydrolysis and oxidative rancidity during storage, thus limiting their shelf life. Furthermore, the oil yield from pressing is relatively low, and the residual oil content in the cake is high, resulting in insufficient resource utilization.

[0005] Microwave and infrared physical field pretreatment technologies have shown potential in improving oil extraction efficiency and reducing enzyme activity. Existing technologies indicate that microwave treatment can significantly improve extraction efficiency and substantially reduce lipase activity. However, most current physical field pretreatments are conducted in an aerobic open environment. The presence of oxygen in the intermediate temperature range makes it impossible to inhibit the transient oxidation induced by lipoxygenase, which instead accelerates the initial oxidation of crude oil. In addition, existing deodorization technologies mostly rely on equipment structure improvements and have not yet moved the antioxidant protection mechanism forward to achieve in-situ protection before the deodorization process. Although enzymatic degumming has been applied, its synergistic design with front-end oxygen barrier enzyme inactivation and back-end deodorization and refining remains a gap.

[0006] In summary, how to systematically resolve the conflict between nutrient preservation and oxidative stability, as well as the contradiction between deep deodorization and the generation of heat-damaging substances, has become a critical technical bottleneck that needs to be overcome in the field of high-quality vegetable oil processing. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of existing technologies by proposing a process for preserving the nutrients in vegetable edible oil during pressing.

[0008] To achieve the above objectives, the present invention adopts the following technical solution:

[0009] A process for preserving nutrients during the pressing of vegetable edible oil includes the following steps:

[0010] S1. Raw material conditioning and oxygen barrier replacement: The oil is placed in a closed environment to adjust the moisture content, and inert gas is introduced to replace the air until the residual oxygen content is <2%.

[0011] S2, Synergistic Enzyme Inactivation and Cell Wall Disruption by Multi-Physical Fields with Oxygen Barrier: Under the protection of an inert gas, the oil obtained in S1 is subjected to synergistic treatment by two physical fields to efficiently inactivate lipase and lipoxygenase and disrupt cell walls, resulting in the treated material; the two physical fields are a combination of infrared radiation and microwave treatment, with microwave treatment causing the material to reach an instantaneous temperature of 85-95℃ to achieve efficient enzyme inactivation.

[0012] S3. Oxygen-barrier temperature pressing and rapid cooling: The processed material is pressed under a slight positive pressure protection of 0.01-0.1MPa inert gas gauge pressure. The extracted crude oil is immediately deoxygenated and rapidly cooled to obtain cooled crude oil. The pressing temperature is 60-80℃, and inert gas is filled into the pressing chamber to form a local slight positive pressure oxygen-barrier environment.

[0013] S4. Enzymatic degumming: The cooled crude oil is subjected to enzymatic degumming treatment so that the residual phosphorus in the degummed oil meets the requirements of physical refining, thus obtaining degummed oil.

[0014] S5. Low-temperature decolorization: Under vacuum conditions, an adsorbent is added to decolorize the degummed oil to obtain decolorized oil.

[0015] S6. Constructing a micro-interface sustained-release antioxidant system: A ternary sustained-release antioxidant complex is added to the decolorized oil and dispersed by high-speed shearing to form a sustained-release shield with a micromicelle structure in the oil phase, thus obtaining the deodorized oil; the amount of the ternary sustained-release antioxidant complex added is 0.02-0.05% of the mass of the decolorized oil; the ternary sustained-release antioxidant complex is composed of tea polyphenol palmitate, tocopherol and phospholipid in a mass ratio of 1:1-2:1-1.5.

[0016] S7. Dual-temperature short-time deodorization: The oil to be deodorized is deodorized in a two-stage process, including a low-temperature stage and a high-temperature stage. In the high-temperature stage, the residence time of the oil to be deodorized in the heater is less than 30 seconds, resulting in deodorized oil. The deodorization temperature of the low-temperature stage is 180-210℃, and the residence time is 30-70 minutes. The deodorization temperature of the high-temperature stage is 220-250℃, the absolute pressure is 0.1-3 mbar, and the direct steam injection rate is 0.5-3% of the mass of the oil to be deodorized.

[0017] S8. Winterization, dewaxing, and nitrogen filling: The deodorized oil is cooled to allow crystal growth and dewaxing, then filtered and filled with nitrogen.

[0018] Preferably, in step S1, the moisture content of the oil is adjusted to 8-12%; the inert gas is any one of nitrogen or a nitrogen mixture containing 5-15% carbon dioxide.

[0019] Preferably, in step S3, the rapid cooling to a temperature ≤25℃ takes less than 3 minutes.

[0020] Preferably, in step S5, the decolorization temperature is 85-95℃ and the decolorization time is 20-25 min; the adsorbent is activated clay, and the amount of activated clay added is 1-2.5% of the mass of the degummed oil.

[0021] Preferably, in step S6, the high-speed shear dispersion is carried out at a temperature of 60-70℃, an absolute pressure of 0.01-0.04MPa, a rotation speed of 2000-3000rpm, and a time of 20-30min.

[0022] Preferably, in step S8, the temperature for crystal growth and dewaxing is 4-10℃, and the crystal growth time is 12-36h; the nitrogen filling uses nitrogen with a purity of ≥99.9%, and the residual oxygen content in the packaging headspace is <2%.

[0023] Preferably, the oilseed is selected from any one of soybeans, peanuts, camellia seeds, and sunflower seeds.

[0024] The core of this invention lies in treating "oxygen barrier - multi-physical field cascade enzyme inactivation - slow-release shield pre-positioning - dual-temperature short-time deodorization" as an organic whole, and realizing nutrient retention throughout the entire oil processing process based on rigorous internal logic.

[0025] First, this invention blocks enzymatic oxidation at its source, interrupting the chain reaction that leads to oil deterioration. At the moment oilseed cells rupture, endogenous lipoxygenase (LOX) and lipase rapidly catalyze the oxidation of unsaturated fatty acids to hydroperoxides under suitable temperature and oxygen conditions. In traditional hot pressing processes, if oxygen is present during heating, activated LOX will acquire a catalytic substrate, leading to an increase in the initial peroxide value of the crude oil. This invention controls residual oxygen in the environment to below 2% through nitrogen purging throughout the process, directly depriving LOX of the oxygen substrate required for the catalytic reaction and greatly inhibiting its ability to initiate chain oxidation in the active temperature range. Based on this, an infrared-microwave stepped synergistic treatment is employed: infrared radiation provides initial uniform preheating, gently crossing the enzyme activity window; subsequently, microwaves, with their penetrating heating and selective absorption effects, bring the material's instantaneous temperature to 85-95°C. Compared to conventional hot air treatment, microwave heating causes violent polar oscillations within the enzyme protein molecules, resulting in irreversible denaturation and inactivation of their spatial conformation within a short time. Since lipoxygenases generally have higher thermal stability than lipases, raising the microwave temperature to 85-95℃ aims to ensure efficient inactivation of the more heat-resistant lipoxygenase, thus achieving simultaneous inactivation of both target enzymes. Under the dual effects of oxygen barrier and microwave heating, supplemented by low-frequency mechanical vibration or ultrasonic cavitation, the expanded and loosened cell walls can be further torn apart, promoting oil release. This "oxygen barrier + multi-physics field" combination achieves efficient enzyme inactivation and cell wall disruption while blocking the instantaneous oxidation pathway in the heating stage, reducing the initial oxidation level of crude oil to an extremely low level, providing high-quality raw materials for subsequent refining.

[0026] Secondly, this invention constructs a micro-interface slow-release shield in the high-temperature refining zone, achieving a pre-positioned synergistic antioxidant barrier. Traditional processes add antioxidants only after refining, a passive defense that cannot recover the loss of natural byproducts such as tocopherols during the high-temperature deodorization period. This invention shifts the antioxidant strategy from "post-event compensation" to "pre-event protection" by introducing a ternary complex composed of tea polyphenol palmitate, tocopherol, and phospholipids into the decolorized oil after decolorization and before deodorization. By constructing the shield after decolorization, non-specific adsorption and removal of phospholipids and antioxidant components by the decolorizing adsorbent are effectively avoided, ensuring the integrity of the slow-release system. The tea polyphenol palmitate, after esterification modification, possesses both strong free radical scavenging ability and excellent oil-phase dispersibility; even a small amount can significantly improve the oxidative stability of the oil. Phospholipids, as amphiphilic substances, construct micro-interface regions in the oil phase and exert metal ion chelation effects, while providing structural support for the formation of the slow-release system. The ternary combination of tea polyphenols, tocopherols, and phospholipids exhibits a strong synergistic antioxidant effect in oils, far superior to single or binary systems. In the subsequent high-temperature deodorization zone, conventional antioxidants tend to rapidly volatilize or thermally decompose, while this ternary system exhibits slow-release characteristics through micro-interface binding: tea polyphenol derivatives are preferentially "protectively consumed," effectively reducing the attack of thermally induced free radicals on tocopherols and sterols in the oil matrix, allowing the antioxidant capacity to persist in extreme thermal fields. Furthermore, this micromicelle structure possesses excellent thermodynamic stability in the oil phase, maintaining dispersion without demulsification or precipitation during the subsequent low-temperature crystal growth stage of winterization dewaxing, ensuring the transparency and cold stability of the finished oil.

[0027] More importantly, this invention decouples nutrient retention from hazardous substance generation through system linkage, overcoming the refining dilemma. The deodorization process has long faced the conflict between nutrient retention and hazardous substance control: while high-temperature, long-duration deodorization removes odors and peroxides, it leads to significant loss of tocopherols and induces the formation of trans fatty acids (TFA) and 3-MCPD esters. When the deodorization temperature exceeds 220°C, the formation rate of TFA and 3-MCPD esters accelerates significantly; conversely, lowering the deodorization temperature and shortening the residence time can drastically reduce the formation of these hazardous substances. This invention effectively resolves this dilemma through front-end and back-end linkage: front-end oxygen inhibition and enzyme inactivation significantly reduce the initial oxidation level of crude oil, effectively mitigating the oxidative load in subsequent deodorization stages; the mid-stage slow-release shield provides high-temperature antioxidant protection for the oil phase. Based on this support, the deodorization process employs a dual-temperature, short-time strategy: first, the oil is held at 180-210℃ for 30-70 minutes to remove most free fatty acids and volatile oxides; then, in a high-temperature zone of 220-250℃, the oil to be deodorized is held in the heater for less than 30 seconds, and the total residence time in the high-temperature zone of the tower is less than 3 minutes, instantly removing residual small-molecule impurities. This dual-temperature deodorization and reasonable equipment combination, while ensuring deodorization efficiency, significantly reduces the formation of trans fatty acids and the loss of vitamin E and phytosterols. By creating a more tolerant operating window for the back end through the front-end process, it achieves a balance between nutrient preservation and safety control.

[0028] In summary, this invention, based on the principle of "oxygen barrier—multi-physical field cascade enzyme inactivation—pre-placed slow-release shield—dual-temperature short-time deodorization," systematically constructs a technical system for preserving the nutrients in vegetable oils from three levels: enzyme source cutoff, processing protection, and optimization of refining conditions. The synergistic effect of the entire process is reflected in: front-end oxygen barrier and enzyme inactivation reduce the initial oxidation value of crude oil, reducing pressure during refining; the mid-stage slow-release shield establishes antioxidant protection before deodorization, preventing significant loss of active ingredients during refining; and the rear-end dual-temperature short-time deodorization, supported by the quality advantages of the front end and the shield protection, completes refining under mild conditions, achieving a win-win situation for both nutrition and safety. This design concept transforms "passive remediation" into "active protection," providing a feasible industrial path for producing vegetable oils that combine high quality and high safety.

[0029] Compared with the prior art, the beneficial effects of the present invention are:

[0030] 1. This invention employs full inert gas replacement before pressing to control residual oxygen in the environment to below 2%. During pressing, inert gas is continuously injected into the feed end of the pressing chamber and the external space of the pressing cage to create a localized oxygen-barrier microenvironment. Simultaneously, this is combined with multi-physics field synergistic treatment of uniform preheating via infrared radiation and instantaneous heating via microwave, enabling the material to rapidly cross the activity temperature window of lipoxygenase under oxygen-barrier conditions and achieve irreversible denaturation and inactivation of the enzyme protein. This method cuts off the enzymatic oxidation chain reaction at its source, effectively avoiding the problem of increased initial peroxide value of crude oil caused by the enzyme activity window period during traditional aerobic pretreatment, thus providing a raw material foundation with excellent oxidative stability for subsequent refining.

[0031] 2. This invention introduces a ternary slow-release antioxidant complex composed of tea polyphenol palmitate, tocopherol, and phospholipids into the decolorized oil after the decolorization process and before the deodorization process. The amphiphilic nature of phospholipids allows for the formation of micromicelle structures in the oil phase. This pre-process design avoids damage to the micromicelle components by the decolorization adsorbent. This "pre-protection" strategy overcomes the passive defense defect of traditional processes that only add antioxidants to the finished oil. Through the binding and slow-release effect of the micro-interface, tea polyphenol palmitate is preferentially consumed in the high-temperature deodorization zone, thereby protecting the tocopherols and sterols in the main oil mass from thermal oxidation and significantly improving the retention rate of endogenous nutrients during refining.

[0032] 3. This invention employs a two-stage deodorization process, including a low-temperature stage and a high-temperature stage. The low-temperature stage involves a longer residence time to remove most free fatty acids and volatile oxides, while the high-temperature stage controls the residence time of the oil to be deodorized in the heater to within 30 seconds. Combined with the low-oxidation crude oil obtained through front-end oxygen-barrier and enzyme-inactivating processes, and the in-situ antioxidant protection provided by the mid-stage slow-release shield, this dual-temperature, short-time deodorization method significantly reduces the formation of heat-induced harmful substances such as trans fatty acids, 3-chloropropanol esters, and glycidyl esters while maintaining the depth of refining. This overcomes the technical bottleneck of traditional single-temperature, long-time deodorization processes, which struggle to simultaneously achieve nutrient retention and harmful substance control.

[0033] 4. This invention integrates three stages—"oxygen-barrier multi-physical field enzyme inactivation—slow-release shield pre-installation—dual-temperature short-time deodorization"—into a complete nutrient retention process. Each stage forms a clear synergistic relationship: the front end provides high-quality raw materials for the back end, the middle stage establishes an antioxidant safety net for the back end, and the back end completes refining under mild conditions. This systemic linkage allows the finished oil to simultaneously achieve high nutrient retention, high oxidative stability, and low levels of harmful substances without excessive refining. The overall effect is significantly better than simply adding up optimizations of each stage individually. Detailed Implementation

[0034] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with existing known technologies. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0035] All raw materials used in this invention are commercially available.

[0036] Example 1: A process for preserving nutrients during the pressing of vegetable edible oil, comprising the following steps:

[0037] S1. Raw material conditioning and oxygen replacement: Place 30kg of rapeseed in a sealed environment and adjust the moisture content to 8%. Pour nitrogen into the soil from the bottom to replace the air until the residual oxygen content is <2%. The conditioning temperature is 20℃. Let the soil stand for 2 hours to reach equilibrium.

[0038] S2, Oxygen Barrier Multi-Physical Field Synergistic Enzyme Inactivation and Cell Wall Disruption: Under nitrogen protection, the oil obtained in S1 is subjected to infrared radiation and microwave treatment: infrared radiation controls the material layer temperature to rise to 50℃ and stays for 3 minutes; microwave treatment controls the microwave frequency to 915MHz, so that the instantaneous temperature of the material reaches 85℃ and stays for 1.5 minutes; then 20Hz low-frequency mechanical vibration is applied to obtain the treated material.

[0039] S3. Oxygen-barrier temperature pressing and rapid cooling: The processed material is pressed at a suitable temperature under the protection of a nitrogen gauge pressure of 0.01-0.1MPa. The pressing temperature is 60℃. Nitrogen is filled into the pressing chamber to form a slight positive pressure. The pressed crude oil is immediately separated from oxygen by a nitrogen curtain and rapidly cooled to 25℃ to obtain cooled crude oil.

[0040] S4. Enzymatic degumming: The cooled crude oil is subjected to enzymatic degumming treatment: 5g of citric acid (food grade, 50% aqueous solution) is added, and the mixture is reacted at 50℃ for 15min; then 0.3g of phospholipase A1 (Lecitase® Ultra, minimum activity 10KLU / g liquid) is added, the pH is adjusted to 5.0, and the mixture is reacted at 50℃ for 1h. 100g of water is added, the stirring speed is 80rpm, and the oil residue is separated by centrifugation to make the residual phosphorus in the degummed oil <10mg / kg, thus obtaining the degummed oil.

[0041] S5. Low-temperature decolorization: Under vacuum conditions, activated clay (food-grade powder, decolorization rate ≥95%) is added to decolorize the degummed oil. The amount of activated clay added is 1% of the mass of the degummed oil. The decolorization temperature is 85℃, the decolorization time is 20min, and the vacuum degree is ≤-0.095MPa to obtain decolorized oil.

[0042] S6. Constructing a micro-interface sustained-release antioxidant system: Add a ternary sustained-release antioxidant complex composed of tea polyphenol palmitate (food grade, GB1886.360, content ≥99%), tocopherol (mixed tocopherol concentrate, total tocopherol content ≥70%) and phospholipids (food grade soybean phospholipids, acetone insoluble matter ≥60%) in a mass ratio of 1:1:1 to the decolorized oil. The amount of the ternary sustained-release antioxidant complex added is 0.02% of the mass of the decolorized oil. Under an oil temperature of 60℃ and an absolute pressure of 0.04MPa, the mixture is sheared and dispersed at 2000rpm for 20min to form a sustained-release shield with a micromicelle structure in the oil phase, thus obtaining the deodorized oil.

[0043] S7. Dual-temperature short-time deodorization: The oil to be deodorized is deodorized in two stages, including a low-temperature stage and a high-temperature stage. The deodorization temperature in the low-temperature stage is 180℃, and the residence time is 30min. The deodorization temperature in the high-temperature stage is 220℃. The residence time of the oil to be deodorized in the heater is 20s, the absolute pressure is 0.1mbar, the direct steam injection rate is 0.5% of the mass of the oil to be deodorized, and the total residence time in the high-temperature zone is 2min, thus obtaining deodorized oil.

[0044] S8. Winterization, dewaxing, and nitrogen filling: Cool the deodorized oil to 4°C and allow it to crystallize for 12 hours. Stir slowly at 10 rpm during crystal growth. After filtration, fill the package with nitrogen gas of ≥99.9% purity. The residual oxygen content in the headspace of the package is <2%.

[0045] Example 2: A process for preserving nutrients during the pressing of vegetable edible oil, comprising the following steps:

[0046] S1. Raw material conditioning and oxygen barrier replacement: Place 30kg of rapeseed in a sealed environment and adjust the moisture content to 10%. Then, introduce a nitrogen mixture containing 10% carbon dioxide from the bottom to replace the air until the residual oxygen content is <2%. The conditioning temperature is 25℃, and the mixture is allowed to stand for 3 hours to reach equilibrium.

[0047] S2, Oxygen Barrier Multi-Physical Field Synergistic Enzyme Inactivation and Cell Wall Disruption: Under inert gas protection, the oil obtained in S1 is subjected to infrared radiation and microwave treatment: infrared radiation controls the material layer temperature to rise to 57℃ and stays for 4.5 min; microwave treatment controls the microwave frequency to 915MHz, so that the instantaneous temperature of the material reaches 90℃ and stays for 2.2 min; then supplemented with 25Hz low-frequency mechanical vibration to obtain the treated material.

[0048] S3. Oxygen-barrier temperature pressing and rapid cooling: The processed material is pressed at a suitable temperature under the protection of a nitrogen gauge pressure of 0.01-0.1MPa. The pressing temperature is 70℃. The pressing chamber is filled with a nitrogen mixture containing 10% carbon dioxide to form a slight positive pressure. The pressed crude oil is immediately passed through an inert gas curtain to isolate oxygen and is rapidly cooled to 20℃ to obtain cooled crude oil.

[0049] S4. Enzymatic degumming: The cooled crude oil is subjected to enzymatic degumming treatment: 7.5g of citric acid (food grade, 50% aqueous solution) is added, and the reaction is carried out at 55℃ for 22min; then 0.55g of phospholipase A1 (Lecitase® Ultra, minimum activity 10KLU / g liquid) is added, the pH is adjusted to 5.25, the reaction is carried out at 55℃ for 1.5h, 200g of water is added, the stirring speed is 115rpm, and the oil residue is separated by centrifugation to make the residual phosphorus in the degummed oil <10mg / kg, thus obtaining degummed oil.

[0050] S5. Low-temperature decolorization: Under vacuum conditions, activated clay (food-grade powder, decolorization rate ≥95%) is added to decolorize the degummed oil. The amount of activated clay added is 1.75% of the mass of the degummed oil. The decolorization temperature is 90℃, the decolorization time is 22min, and the vacuum degree is ≤-0.095MPa to obtain decolorized oil.

[0051] S6. Constructing a micro-interface sustained-release antioxidant system: A ternary sustained-release antioxidant complex composed of tea polyphenol palmitate (food grade, GB1886.360, content ≥99%), tocopherol (mixed tocopherol concentrate, total tocopherol content ≥70%), and phospholipids (food grade soybean phospholipids, acetone insoluble matter ≥60%) in a mass ratio of 1:1.5:1.25 was added to the decolorized oil. The amount of the ternary sustained-release antioxidant complex added was 0.035% of the mass of the decolorized oil. At an oil temperature of 65℃ and an absolute pressure of 0.025MPa, the mixture was sheared at 2500rpm for 25min to form a sustained-release shield with a micromicelle structure in the oil phase, thus obtaining the deodorized oil.

[0052] S7. Dual-temperature short-time deodorization: The oil to be deodorized is deodorized in two stages, including a low-temperature stage and a high-temperature stage. The deodorization temperature in the low-temperature stage is 195℃, and the residence time is 50min. The deodorization temperature in the high-temperature stage is 235℃. The residence time of the oil to be deodorized in the heater is 25s, the absolute pressure is 1.55mbar, the direct steam injection rate is 1.75% of the mass of the oil to be deodorized, and the total residence time in the high-temperature zone is 2.5min, thus obtaining deodorized oil.

[0053] S8. Winterization, dewaxing, and nitrogen filling: Cool the deodorized oil to 7°C and allow it to crystallize for 24 hours. Stir slowly at 11 rpm during crystal growth. After filtration, fill the package with nitrogen gas of ≥99.9% purity. The residual oxygen content in the headspace of the package is <2%.

[0054] Example 3: A process for preserving nutrients during the pressing of vegetable edible oil, comprising the following steps:

[0055] S1. Raw material conditioning and oxygen replacement: Place 30kg of rapeseed in a sealed environment and adjust the moisture content to 12%. Then, introduce a nitrogen mixture containing 15% carbon dioxide from the bottom to replace the air until the residual oxygen content is <2%. The conditioning temperature is 30℃, and the mixture is allowed to stand for 4 hours to reach equilibrium.

[0056] S2, Oxygen Barrier Multi-Physical Field Synergistic Enzyme Inactivation and Cell Wall Disruption: Under inert gas protection, the oil obtained in S1 is subjected to infrared radiation and microwave treatment: infrared radiation controls the material layer temperature to rise to 65℃ and stays for 6 minutes; microwave treatment controls the microwave frequency to 915MHz, so that the instantaneous temperature of the material reaches 95℃ and stays for 3 minutes; then, 30Hz low-frequency mechanical vibration is applied to obtain the treated material.

[0057] S3. Oxygen-barrier temperature pressing and rapid cooling: The processed material is pressed at a suitable temperature under the protection of a nitrogen gauge pressure of 0.01-0.1MPa. The pressing temperature is 80℃. The pressing chamber is filled with a nitrogen mixture containing 15% carbon dioxide to form a slight positive pressure. The pressed crude oil is immediately passed through an inert gas curtain to isolate oxygen and is rapidly cooled to 15℃ to obtain cooled crude oil.

[0058] S4. Enzymatic degumming: The cooled crude oil is subjected to enzymatic degumming treatment: 10g of citric acid (food grade, 50% aqueous solution) is added, and the mixture is reacted at 60℃ for 30min; then 0.8g of phospholipase A1 (Lecitase® Ultra, minimum activity 10KLU / g liquid) is added, the pH is adjusted to 5.5, and the mixture is reacted at 60℃ for 2h. 300g of water is added, the stirring speed is 150rpm, and the oil residue is separated by centrifugation to make the residual phosphorus in the degummed oil <10mg / kg, thus obtaining the degummed oil.

[0059] S5. Low-temperature decolorization: Under vacuum conditions, activated clay (food-grade powder, decolorization rate ≥95%) is added to decolorize the degummed oil. The amount of activated clay added is 2.5% of the mass of the degummed oil. The decolorization temperature is 95℃, the decolorization time is 25min, and the vacuum degree is ≤-0.095MPa to obtain decolorized oil.

[0060] S6. Constructing a micro-interface sustained-release antioxidant system: Add a ternary sustained-release antioxidant complex composed of tea polyphenol palmitate (food grade, GB1886.360, content ≥99%), tocopherol (mixed tocopherol concentrate, total tocopherol content ≥70%) and phospholipids (food grade soybean phospholipids, acetone insoluble matter ≥60%) in a mass ratio of 1:2:1.5 to the decolorized oil. The amount of the ternary sustained-release antioxidant complex added is 0.05% of the mass of the decolorized oil. Under an oil temperature of 70℃ and an absolute pressure of 0.01MPa, the mixture is sheared and dispersed at 3000rpm for 30min to form a sustained-release shield with a micromicelle structure in the oil phase, thus obtaining the deodorized oil.

[0061] S7. Dual-temperature short-time deodorization: The deodorized oil is deodorized in two stages, including a low-temperature stage and a high-temperature stage. The deodorization temperature in the low-temperature stage is 210℃, and the residence time is 70min. The deodorization temperature in the high-temperature stage is 250℃, the residence time of the oil to be deodorized in the heater is 25s, the absolute pressure is 3mbar, the direct steam injection rate is 3% of the mass of the oil to be deodorized, and the total residence time in the high-temperature zone is 3min, thus obtaining deodorized oil.

[0062] S8. Winterization, dewaxing, and nitrogen filling: Cool the deodorized oil to 10°C and allow it to crystallize for 36 hours. Stir slowly at 13 rpm during crystal growth. After filtration, fill the package with nitrogen gas of ≥99.9% purity. The residual oxygen content in the headspace of the package is <2%.

[0063] Comparative Example 1: Based on Example 2, the difference is that inert gas is not introduced in steps S1 and S2 (open oxygen environment), but infrared-microwave synergistic treatment is still used to raise the material temperature to 90°C, and the remaining steps are the same as in Example 2.

[0064] Comparative Example 2: Based on Example 2, the difference is that nitrogen gas is introduced for protection in step S2, but instead of infrared-microwave synergistic processing, conventional hot air heating is used to raise the material temperature to 90°C and hold it for 5 minutes. The remaining steps are the same as in Example 2.

[0065] Comparative Example 3: Based on Example 2, the difference is that the ternary slow-release antioxidant complex is not added in step S6. Instead, after winterization dewaxing and nitrogen filling in S8, the same proportion and amount (total addition amount 0.035%, mass ratio 1:1.5:1.25) of the tea polyphenol palmitate, tocopherol and phospholipid ternary complex is added to the finished oil. The remaining steps are the same as in Example 2.

[0066] Comparative Example 4: Based on Example 2, the difference is that only tea polyphenol palmitate and tocopherol (the mass ratio of the two is maintained at 1:1.5) are added in step S6, and no phospholipids are added. The total amount added is still 0.035% of the mass of the decolorized oil. The remaining steps are the same as in Example 2.

[0067] Comparative Example 5: Based on Example 2, the difference is that only tocopherol and phospholipids are added in step S6 (the mass ratio of the two is maintained at 1.5:1.25), and tea polyphenol palmitate is not added. The total amount added is still 0.035% of the mass of the decolorized oil. The remaining steps are the same as in Example 2.

[0068] Comparative Example 6: Based on Example 2, the difference is that in step S7, instead of using dual-temperature short-time deodorization, conventional single-temperature deodorization is used—the oil is heated to 240°C, the residence time is 60 minutes, the direct steam injection rate is 3% of the mass of the oil to be deodorized, the absolute pressure of the deodorization tower is 3 mbar, and the remaining steps are the same as in Example 2.

[0069] Test Example: The edible oils prepared in Examples 1-3 and Comparative Examples 1-6 above were subjected to the following tests, and the test methods are as follows:

[0070] 1. Initial peroxide value of crude oil: determined according to Method I (indicator titration method) of GB 5009.227-2023 "National Food Safety Standard - Determination of Peroxide Value in Food". The result is expressed as meq / kg.

[0071] 2. Residual activity of oilseed lipoxygenase (LOX): determined by ultraviolet spectrophotometry. Oilseed samples treated with S2 were used, and the absorbance change was measured at 234 nm using linoleic acid as a substrate. One unit of enzyme activity was defined as a change in absorbance of 0.001 per minute. Residual activity was expressed as a relative percentage between the treated sample and the untreated control sample.

[0072] 3. Tocopherol content and retention rate: Determined according to GB / T 26635-2025 "Determination of Tocopherol and Tocotrienol Content in Animal and Vegetable Oils by High Performance Liquid Chromatography". Tocopherol retention rate (%) = (Total tocopherol content of deodorized oil sample / Tocopherol content of degummed oil) × 100%.

[0073] 4. Residual rate of tea polyphenol palmitate: Following the method for determining the content of tea polyphenol palmitate in GB 1886.360-2022, high performance liquid chromatography (C18 column, detection wavelength 280nm) was used, with external standard method for quantification. Residual rate (%) = (content of tea polyphenol palmitate in deodorized oil sample / content after addition in decolorized oil) × 100%.

[0074] 5. Trans fatty acid content: Determined by gas chromatography according to GB 5009.257-2016 "National Food Safety Standard - Determination of Trans Fatty Acids in Food". The results are expressed as the percentage (%) of the peak area of ​​each trans isomer methyl ester to the peak area of ​​the total fatty acid methyl ester.

[0075] 6. Content of 3-chloropropanol esters (3-MCPD esters) and glycidyl esters (GEs): determined according to AOCS Official Method Cd 29a-13 or GB 5009.191-2024 "National Food Safety Standard - Determination of Chloropropanol and its Fatty Acid Ester Content in Food", and the results are expressed in mg / kg (based on oil).

[0076] 7. Oxidation induction time of finished oil: The oxidation stability of oils was determined using an oil oxidation stability analyzer, referring to the general method for determining the oxidation stability of oils (Rancimat method). The conditions were: sample amount 3g, temperature 110℃, air flow rate 20L / h. The results are expressed as oxidation induction time (h).

[0077] 8. Phytosterol content and retention rate: Determined according to GB / T 25223-2010 "Determination of Sterol Composition and Total Sterol Content in Animal and Vegetable Oils by Gas Chromatography". Sterol retention rate (%) = (Total sterol content of deodorized oil sample / Total sterol content of degummed oil) × 100%.

[0078] 9. Determination of Routine Physicochemical and Safety Indicators of Refined Oil Products: The routine quality and safety indicators of refined oil products shall be determined according to the following national standard methods:

[0079] (1) Acid value: determined according to GB 5009.229-2025 (cold solvent indicator titration or automatic potentiometric titration), and the result is expressed as mgKOH / g.

[0080] (2) Moisture and volatile matter: determined according to the first method of GB 5009.236-2016, and the results are expressed as mass fraction (%).

[0081] (3) Insoluble impurities: determined according to GB / T 15688-2024, and the results are expressed as mass fraction (%).

[0082] (4) Solvent residue: determined by headspace gas chromatography according to GB 5009.262-2016, and the result is expressed as mg / kg.

[0083] (5) Color: Determined according to the Lovibond colorimetric method in GB / T 22460-2008. The results are expressed as colorimetric values.

[0084] (6) Transparency, odor and taste: determined according to the sensory evaluation method of GB / T 5525-2025.

[0085] (7) Heating test (280℃): Determine according to GB / T 5531-2018, and observe the change in oil color and the precipitation.

[0086] (8) Smoke point: Determined according to GB / T 20795-2025 (automatic smoke point tester method or visual method), and the result is expressed in °C.

[0087] (9) Erucic acid content: determined by gas chromatography according to GB 5009.168-2016, and the result is expressed as mass fraction (%).

[0088] (10) Benzo[a]pyrene: Determined by high performance liquid chromatography according to GB 5009.27-2016. Results are expressed in μg / kg.

[0089] (11) Aflatoxin B1: Determined by isotope dilution liquid chromatography-tandem mass spectrometry according to GB 5009.22-2016. The results are expressed in μg / kg.

[0090] (12) Total arsenic: determined by ICP-MS method according to GB 5009.11-2024, and the result is expressed as mg / kg.

[0091] (13) Lead: Determined by graphite furnace atomic absorption spectrometry according to GB 5009.12-2023. The result is expressed in mg / kg.

[0092] The test results are shown in Tables 1 and 2.

[0093] Table 1: Test Results of Quality Indicators in Examples 1-3

[0094]

[0095] Data Analysis: Analysis of Table 1 shows that the finished oils prepared in Examples 1-3 all meet the requirements of GB / T 1536-2021 Grade 1 pressed rapeseed oil in terms of conventional physicochemical and safety indicators (heating test results are better than Grade 2 standards and meet Grade 1 standards). Furthermore, key indicators such as acid value and peroxide value are far superior to the standard minimums. The acid value is as low as 0.06-0.09 mgKOH / g, and the smoke point reaches 215-220℃, indicating that the dual-temperature short-time deodorization process still achieves sufficient deacidification and deodorization refining effects under mild conditions. Benzo[a]pyrene, aflatoxin, and heavy metals were not detected or were far below the safety limits, proving that no external contamination was introduced throughout the process, and the products possess extremely high basic quality and safety.

[0096] Table 2: Test Results of Examples 1-3 and Comparative Examples 1-6

[0097]

[0098] Data analysis: Analysis of the values ​​in Table 2 shows that the present invention systematically solves the contradiction between nutrient retention and hazardous substance control through the synergistic linkage of three core mechanisms.

[0099] First, oxygen barrier and multi-physics field synergy blocked enzymatic oxidation at its source. Examples 1-3, through oxygen barrier and instantaneous microwave heating, controlled the initial peroxide value of crude oil at 1.1-1.3 meq / kg, reducing the residual LOX activity to 7.2-8.5%. Comparative Example 1, treated with microwaves in an aerobic environment, achieved a similar enzyme inactivation effect to Example 2, with a residual activity of 8.2%. However, LOX gained oxygen substrate during the heating phase, causing the initial peroxide value of crude oil to rise sharply to 8.6 meq / kg. Although Comparative Example 2 had nitrogen purging protection, the continuous introduction of hot air during conventional heating directly introduced a large amount of oxygen, disrupting the local oxygen barrier environment. Simultaneously, the poor penetration of the hot air resulted in incomplete enzyme inactivation, with LOX residue reaching as high as 32.4%. The residual LOX under these aerobic and heated conditions underwent vigorous catalytic oxidation, causing the peroxide value to surge to 10.2 meq / kg.

[0100] Secondly, the micro-interface slow-release shield provides in-situ protection in the high-temperature deodorization zone. In Comparative Example 3, the "tocopherol retention rate" refers to the measured value after deodorization but before the addition of antioxidants (at this point, there is no exogenous addition, i.e., it is the endogenous retention rate). For the examples and other comparative examples, since the added exogenous tocopherols are preferentially consumed as slow-release sacrificial agents in the high-temperature deodorization zone, the remaining tocopherols after deodorization are mainly endogenous components. Therefore, this calculation method can effectively reflect the true retention of endogenous nutrients. In Example 2, the endogenous tocopherol retention rate reached 92.8%, and the sterol retention rate reached 97.5%. In Comparative Example 3, antioxidants were added after deodorization, and there was no shield protection during the deodorization process. The endogenous tocopherol retention rate was only 68.5%, and the sterol retention rate was 92.2%, proving that post-treatment compensation cannot recover the losses from thermal degradation during deodorization. In Comparative Example 4, lacking phospholipids, tea polyphenol palmitate was directly exposed and volatilized in the high-temperature zone due to the loss of micromicelle protection, with a residual rate of only 12.3%, and the tocopherol retention rate dropped to 74.2%, confirming that the micro-interface constructed by phospholipids is the structural basis for maintaining the shield's slow-release properties. In Comparative Example 5, lacking tea polyphenol palmitate, tocopherol lost the sacrificial protection of the main antioxidant, and the retention rate dropped to 65.8%. In addition, Comparative Examples 1 and 2, due to their high initial peroxide values, experienced a large amount of shield consumption due to the intense free radical reaction during deodorization, and the residual rates of tea polyphenol palmitate dropped sharply to 42.5% and 35.8%, respectively, further confirming that front-end oxygen control provides a fundamental support for the effectiveness of the back-end shield.

[0101] Finally, dual-temperature short-time deodorization decoupled nutrient retention from the generation of harmful substances. The generation of trans fatty acids, 3-MCPD esters, and GEs is mainly driven by the deodorization heat load. Examples 1-3 and Comparative Examples 1-5 all employed dual-temperature short-time deodorization, with trans fatty acids controlled at 0.21% or below, 3-MCPD esters at or below 0.61 mg / kg, and GEs at or below 1.05 mg / kg. Comparative Example 6 employed single-temperature long-time deodorization, significantly increasing the heat load, raising trans fatty acids to 0.67%, 3-MCPD esters to 2.34 mg / kg, and GEs to 2.89 mg / kg, confirming that prolonged high temperature is the main driving force for harmful substance generation. This invention relies on high-quality crude oil at the front end and a slow-release shield in the middle stage to reduce the dependence of deodorization on high heat load, enabling dual-temperature short-time deodorization to be implemented, thus inhibiting the generation of harmful substances while ensuring the depth of refining.

[0102] The oxidation induction time comprehensively reflects the synergistic effect of the above mechanisms. Examples 1-3 had induction times as long as 15.2-16.5 hours, while Comparative Examples 1 and 2, due to severe initial oxidation and significant nutrient loss, had induction times of only 4.1-4.8 hours. Comparative Examples 3-6, due to the lack of a protective shield or poor deodorization conditions, had induction times between 6.5 and 9.6 hours. This indicates that improvements to a single step alone cannot achieve long-term stability; the system integration of oxygen-barrier enzyme inactivation, slow-release protective shield, and dual-temperature deodorization is the fundamental guarantee for obtaining extremely high oxidation stability.

[0103] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A process for preserving nutrients during the pressing of vegetable edible oil, characterized in that, Includes the following steps: S1. Raw material conditioning and oxygen barrier replacement: The oil is placed in a closed environment to adjust the moisture content, and inert gas is introduced to replace the air until the residual oxygen content is <2%; S2, Synergistic Enzyme Inactivation and Cell Wall Disruption by Multi-Physical Fields with Oxygen Barrier: Under the protection of an inert gas, the oil obtained in S1 is subjected to synergistic treatment by two physical fields to efficiently inactivate lipase and lipoxygenase and disrupt cell walls, resulting in the treated material; the two physical fields are a combination of infrared radiation and microwave treatment, with microwave treatment causing the material to reach an instantaneous temperature of 85-95℃ to achieve efficient enzyme inactivation. S3. Oxygen-barrier temperature pressing and rapid cooling: The processed material is pressed under a slight positive pressure protection of 0.01-0.1MPa inert gas gauge pressure. The extracted crude oil is immediately deoxygenated and rapidly cooled to obtain cooled crude oil. The pressing temperature is 60-80℃, and the pressing chamber is filled with inert gas to form a local slight positive pressure oxygen-barrier environment. S4. Enzymatic degumming: The cooled crude oil is subjected to enzymatic degumming treatment so that the residual phosphorus in the degummed oil meets the requirements of physical refining, and degummed oil is obtained. S5. Low-temperature decolorization: Under vacuum conditions, an adsorbent is added to decolorize the degummed oil to obtain decolorized oil; S6. Constructing a micro-interface sustained-release antioxidant system: A ternary sustained-release antioxidant complex is added to the decolorized oil and dispersed by high-speed shearing to form a sustained-release shield with a micromicelle structure in the oil phase, thus obtaining the deodorized oil; the amount of the ternary sustained-release antioxidant complex added is 0.02-0.05% of the mass of the decolorized oil; the ternary sustained-release antioxidant complex is composed of tea polyphenol palmitate, tocopherol and phospholipid in a mass ratio of 1:1-2:1-1.5; S7. Dual-Temperature Short-Time Deodorization: The oil to be deodorized is deodorized in a two-stage process, including a low-temperature stage and a high-temperature stage. In the high-temperature stage, the residence time of the oil in the heater is less than 30 seconds, resulting in deodorized oil. The deodorization temperature in the low-temperature stage is 180-210℃, and the residence time is 30-70 minutes. The deodorization temperature in the high-temperature stage is 220-250℃, the absolute pressure is 0.1-3 mbar, and the direct steam injection rate is 0.5-3% of the mass of the oil to be deodorized. S8. Winterization, dewaxing, and nitrogen filling: The deodorized oil is cooled to allow crystal growth and dewaxing, then filtered and filled with nitrogen.

2. The vegetable edible oil pressing nutrient retention process according to claim 1, characterized in that, In step S1, the moisture content of the oil is adjusted to 8-12%; the inert gas is either nitrogen or a nitrogen mixture containing 5-15% carbon dioxide.

3. The vegetable edible oil pressing and nutrient retention process according to claim 1, characterized in that, In step S3, the rapid cooling to a temperature ≤25℃ takes less than 3 minutes.

4. The vegetable edible oil pressing nutrient retention process according to claim 1, characterized in that, In step S5, the decolorization temperature is 85-95℃ and the decolorization time is 20-25 min; the adsorbent is activated clay, and the amount of activated clay added is 1-2.5% of the mass of the degummed oil.

5. The vegetable edible oil pressing and nutrient retention process according to claim 1, characterized in that, In step S6, the high-speed shear dispersion is carried out at a temperature of 60-70℃, an absolute pressure of 0.01-0.04MPa, a rotation speed of 2000-3000rpm, and a time of 20-30min.

6. The vegetable edible oil pressing nutrient retention process according to claim 1, characterized in that, In step S8, the temperature for crystal growth and dewaxing is 4-10℃, and the crystal growth time is 12-36h; the nitrogen filling uses nitrogen with a purity of ≥99.9%, and the residual oxygen content in the packaging headspace is <2%.

7. The vegetable edible oil pressing nutrient retention process according to claim 1, characterized in that, The oilseeds are selected from any one of soybeans, peanuts, camellia seeds, and sunflower seeds.

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