Low-temperature fresh-keeping peanut oil processing technology for enhancing freshness of peanut oil

Abstract

This invention relates to the field of edible oil production technology, specifically a low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil. The core steps include low-temperature pretreatment of raw materials, gradient low-temperature freshness-locking pressing, low-temperature static sedimentation, low-temperature composite microfiltration, and low-temperature freshness-locking bottling. The pressing parameters are quantitatively controlled using a critical matching formula for freshness-locking pressing, keeping the peak temperature of the peanut material below 45℃. The entire process employs a closed, low-oxygen environment and inert gas protection, complemented by a multi-dimensional quantitative control system. This invention inhibits oil oxidation and deterioration from the source, maximizing the preservation of the original flavor and active nutrients of peanut oil, achieving long-term freshness maintenance, improving batch-to-batch quality uniformity, and is compatible with existing industrial production lines, possessing significant industrial application value.

Description

Technical Field

[0001] This invention relates to the field of edible oil production technology, specifically to a low-temperature freshness-locking peanut oil processing technology that enhances the freshness of peanut oil. Background Technology

[0002] Peanut oil, as one of the most consumed edible vegetable oils in my country, occupies an important position in people's diets due to its unique flavor characteristics and rich nutritional composition. The ability of peanut oil to maintain freshness is a core indicator determining product quality, shelf life, and market competitiveness. Its key influencing factors include the precision of temperature control during processing, the level of oxygen contact control, the matching of process parameters, and the effectiveness of impurity and gum removal, among other dimensions. Currently, peanut oil processing technology in the industry is mainly divided into two categories: hot pressing and cold pressing. Traditional hot pressing achieves high oil yield through high-temperature roasting and pressing. However, the high-temperature environment easily triggers thermal oxidation and thermal decomposition reactions of the oil, leading to the loss of the original flavor substances of peanuts and the destruction of active nutrients such as vitamin E and phytosterols. At the same time, it easily causes an increase in the initial acid value and peroxide value of the product, resulting in a short freshness retention period. Although traditional cold pressing avoids the core drawbacks of high-temperature processing, it generally suffers from problems such as the lack of standardized control over raw material pretreatment, the lack of quantitative matching relationship between pressing process parameters, unsystematic oxygen isolation measures throughout the process, and the lack of clear quantitative judgment standards for the processing endpoint. Not only is the oil yield unstable, but it also easily leads to enzymatic oxidation and auto-oxidation of the oil during processing. The freshness of the product deteriorates rapidly during the shelf life, and the product quality fluctuates greatly between different batches, making it difficult to achieve long-term stable maintenance of peanut oil freshness.

[0003] Addressing the industry demand for preserving the aroma and freshness of peanut oil, patent document CN117683581A, entitled "A Production Process and Device for Maintaining the Fresh Aroma of Richly Fragrant Peanut Oil," discloses a peanut oil production scheme. This scheme sequentially sets six core steps: raw material processing, ozone sterilization, low-temperature oil pressing, quick-freezing, filtration, and constant-temperature nitrogen-filled storage. It also includes a corresponding stirring and pressing production device. The core technical concept is to avoid aroma volatilization and oxidation during high-temperature processing through low-temperature oil pressing, and to reduce the loss of aroma and nutrients through rapid freezing. Finally, the constant-temperature oil tank is filled with nitrogen and sealed to isolate oxygen, thereby preserving the aroma and freshness of the peanut oil. This scheme, to a certain extent, solves the problems of aroma loss and accelerated oil oxidation in traditional high-temperature processing, providing a basic technological direction for maintaining the freshness of peanut oil. However, in actual industrial applications, several technical shortcomings still exist. First, the prior art only outlines the macroscopic process direction of low-temperature oil pressing, failing to quantify and implement closed-loop control of core process parameters such as pressure gradient, holding time, peak peanut temperature, and heating rate during pressing. It also fails to establish a correlation between pressing process parameters and oil freshness retention, making precise control of the freshness-locking effect during pressing impossible. In actual production, this can easily lead to problems such as uncontrolled material temperature and an inability to simultaneously achieve both oil yield and freshness retention. Second, the raw material pretreatment stage in the prior art only involves routine washing and drying, without precise control over the water activity and moisture distribution uniformity of the peanut kernels. The moisture state of the raw material directly affects the stability of oil extraction and the initial quality of the oil during pressing, easily leading to significant differences in pressing effects between different batches of raw material and insufficient product quality uniformity. Third, the prior art fails to establish a systematic low-oxygen environment control system for the entire processing flow, only implementing nitrogen purging in the final storage stage, and neglecting pressing and sedimentation. The first point is that the core processing steps, such as filtration and filling, do not quantitatively control key indicators such as ambient oxygen content, oil oxygen contact time, and residual oxygen rate in the packaging headspace. The oil remains at continuous oxidation risk throughout the processing, making it impossible to lock in freshness across the entire chain from raw materials to finished products. The second point is that the comparison document only removes impurities and gums from oils through conventional filtration and quick-freezing, without optimizing the gum removal process for low-temperature environments. This fails to effectively remove phospholipids and other colloidal substances from the oils, and the presence of phospholipids easily accelerates oxidation and deterioration during storage, leading to rapid decline in freshness during the product's shelf life and insufficient long-term storage stability. The third point is that the process scheme in the comparison document does not establish quantitative judgment formulas and control standards for the process endpoints and quality control thresholds of each step. The production process relies heavily on manual experience, making it difficult to adapt to the standardized management and control requirements of industrial-scale production, and the problem of batch-to-batch product freshness and quality fluctuations cannot be fundamentally solved.

[0004] Based on this, and addressing the numerous shortcomings of existing technologies and the aforementioned comparative documents, we are developing a peanut oil processing technology that enables low-temperature preservation throughout the entire processing flow, precise quantitative control of process parameters, full-chain oxidation prevention and control, and consistent batch quality. This technology has significant practical implications and industrial application value for improving the freshness retention of peanut oil products, extending product shelf life, and promoting the standardization and high-quality development of the peanut oil processing industry. Summary of the Invention

[0005] The purpose of this invention is to provide a low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil, thereby solving the problems mentioned in the background art, such as weak freshness retention capacity, lack of quantitative matching of process parameters, insufficient whole-chain oxidation control, and large batch quality fluctuations in existing peanut oil processing technologies.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil includes peanut kernel pretreatment, pressing, sedimentation, filtration, and bottling steps, as detailed below: S1 Raw Material Low Temperature Pretreatment: Select peanut kernels with a maturity of ≥95%, remove impurities, and then condition them in a low temperature and sealed environment to control the water activity of the peanut kernels to a preset range. S2 Gradient Low-Temperature Fresh-Locking Pressing: Conditioned peanut kernels are fed into a closed hydraulic cold-pressing equipment for three-stage gradient low-temperature pressing. The ambient temperature is controlled between 15℃ and 25℃ throughout the pressing process, and the peanut material temperature never exceeds 45℃. The process parameters meet the critical matching formula for fresh-locking pressing. ; In the formula, K is the critical index for freshness-locking pressing, P is the final pressing pressure in MPa; t is the holding time of the final pressure in s; and T is the peak temperature of the peanut material during the pressing process in °C. S3 Low-Temperature Static Settling: The crude oil obtained by pressing is sent into a sealed settling tank and allowed to settle naturally in a dark and low-temperature environment. Inert gas is introduced throughout the settling process to maintain a slight positive pressure. S4 Low-Temperature Composite Microfiltration: The supernatant oil after sedimentation is sent into a two-stage composite microfiltration system for graded filtration in a constant temperature and low-temperature environment to remove solid impurities and colloidal substances, and obtain filtered clean oil. S5 Low-Temperature Freshness-Locking Filling: Filtered oil is filled in a light-proof, low-temperature, inert gas atmosphere. Before filling, the packaging container is purged with inert gas. After filling, the headspace residual oxygen rate meets the critical control formula for freshness-locking storage. ; In the formula, The headspace residual oxygen content of the oil after filling is expressed as % (%). Set the temperature for oil storage, in °C; After bottling, the finished product is a low-temperature fresh-locking peanut oil.

[0007] Preferably, in step S1, the temperature of the low-temperature sealed environment is controlled at 18℃-22℃, the relative humidity is controlled at 45%-55%, the conditioning time is 12h-24h, and the water activity Aw of the peanut kernels after conditioning is controlled at 0.45-0.55. The moisture content deviation at different locations of the peanut kernels satisfies the uniformity control formula: ; In the formula, This is due to the relative deviation in moisture content. The maximum moisture content of the peanut kernel sample. This represents the minimum moisture content of the peanut kernel sample. The average moisture content of the peanut kernel sample is given.

[0008] Preferably, in step S2, the specific parameters of the three-stage gradient pressurization low-temperature pressing are as follows: the first stage pressurization is increased to 8MPa-12MPa, and the pressure holding time is 180s-300s; the second stage pressurization is increased to 20MPa-25MPa, and the pressure holding time is 240s-360s; the third stage pressurization is increased to 35MPa-45MPa, and the pressure holding time is 600s-900s. The oxygen volume fraction in the closed environment throughout the pressing process is ≤0.5%, and the heating rate of the peanut material is ≤0.03℃ / min.

[0009] Preferably, in step S3, the temperature inside the settling tank is constantly controlled at 10℃-15℃, the settling time is 48h-72h, the inert gas pressure maintained inside the tank is 0.02MPa-0.05MPa, and the rate of decrease in oil turbidity during the settling process satisfies the settling efficiency control formula: ; In the formula, The average rate of decrease in turbidity. The initial turbidity of the oil after settling is expressed in NTU. The value represents the oil turbidity after settling for t hours, in NTU; t represents the settling time, in hours.

[0010] Preferably, in step S4, the constant temperature and low temperature environment of the two-stage composite microfiltration system are controlled at 12℃-18℃. The first-stage microfiltration uses polypropylene meltblown filter material with a pore size of 5μm-10μm and a filtration pressure of 0.1MPa-0.3MPa. The second-stage microfiltration uses polyethersulfone pleated filter material with a pore size of 0.22μm-0.45μm and a filtration pressure of 0.2MPa-0.4MPa. The total oxygen contact time between the oil and the environment throughout the filtration process is ≤30min.

[0011] Preferably, in step S5, the inert gas replacement of the packaging container adopts a vacuum-filling alternating replacement process, with ≥3 replacement cycles, an absolute pressure of ≤1kPa for each vacuuming cycle, and an inert gas purity ≥99.99%. The residual oxygen rate inside the container after replacement satisfies the replacement efficiency control formula: ; In the formula, The residual oxygen rate in the container after replacement. This represents the initial air oxygen volume fraction. denoted as the gas replacement rate for a single replacement, and n as the number of replacements.

[0012] Preferably, after step S2 and before step S3, a low-temperature hydration degumming step is included: the pressed crude oil is fed into a sealed degumming tank, and at an oil temperature of 35℃-40℃, a citric acid aqueous solution of 1%-2% by weight of the crude oil is added, stirred and mixed, and allowed to stand for 20-40 minutes. Then, deionized water of 2%-4% by weight of the crude oil is added, stirred and mixed, and allowed to stand for 30-60 minutes. The gums are removed by centrifugation, and the phospholipid content of the degummed oil meets the degumming control formula. ; In the formula, This refers to the mass concentration of phospholipids in the oil.

[0013] As a preferred option, steps S1 to S5 are conducted in a light-proof manner. All equipment, pipes and containers that come into direct contact with the oil are made of food-grade 304 / 316L stainless steel. The inert gas used throughout the process is food-grade nitrogen or food-grade argon. The total time from the production of crude oil to the completion of finished product bottling is ≤12h.

[0014] Preferably, in the critical matching formula for freshness-locking pressing in step S2, the preferred range of K value is [0.95, 1.15], the value range of the final pressing pressure P is 38MPa-42MPa, the value range of the final pressure holding time t is 700s-800s, and the peak temperature of peanut material during the pressing process is T≤42℃.

[0015] Preferably, in the critical control formula for freshness-locking storage in step S5, the oil storage set temperature is... The values ​​range from 4℃ to 25℃. After bottling, the initial acid value of the finished peanut oil is ≤0.15mgKOH / g, the initial peroxide value is ≤0.05g / 100g, and it meets the freshness stability control formula: ; In the formula, For storage The peroxide value of Tianhou oil is expressed in g / 100g. This refers to the number of days the finished product has been stored at room temperature in a sealed container, expressed in days (d).

[0016] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention addresses the industry pain points of traditional peanut oil processing, such as high-temperature pressing and refining leading to oil oxidation, flavor decomposition, and nutrient loss, and the poor parameter matching and insufficient oxygen contact control in ordinary cold pressing processes, which result in short product freshness retention periods and large batch quality fluctuations. Through a systematic process design of low-temperature, closed, and low-oxygen throughout the entire process, the original freshness of peanut oil is locked in the entire chain. In the raw material pretreatment stage, the water activity and moisture distribution uniformity of peanut kernels are precisely controlled through low-temperature closed conditioning, ensuring the stability of the pressed oil while avoiding flavor deterioration caused by the enzymatic reaction of the raw materials themselves. In the pressing stage, a three-stage gradient pressurization low-temperature pressing process combined with a freshness-locking pressing critical matching formula quantifies and controls the matching relationship between pressure, holding time, and material temperature, strictly controlling the peak temperature of peanut material during the pressing process below 45℃. This inhibits the occurrence of thermal oxidation and thermal decomposition reactions of the oil from the source, maximizing the preservation of the original flavor substances, vitamin E, phytosterols, and other active nutrients in peanut oil. Combined with a fully closed conveying process and inert gas atmosphere protection, the probability and duration of contact between the oil and oxygen are significantly reduced, significantly lowering the initial acid value and peroxide value of the oil, achieving long-term preservation of the original freshness of peanut oil and extending the product's shelf life.

[0017] 2. This invention constructs a closed-loop control system for the entire process parameters of peanut oil processing through multi-dimensional quantitative control formulas, solving the problems of traditional peanut oil processing relying on manual experience, lack of quantitative matching standards for process parameters, and large batch-to-batch product quality fluctuations. In the raw material conditioning stage, the moisture uniformity control formula ensures batch consistency of raw material pretreatment; in the sedimentation stage, the sedimentation efficiency control formula achieves standardized judgment of the sedimentation process endpoint; in the filling stage, the replacement efficiency control formula and the freshness-locking storage critical control formula achieve precise control of residual oxygen rate inside the packaging, so that the process parameters of each process have clear quantitative control boundaries. Meanwhile, this invention achieves efficient removal of gums and solid impurities from oil products under low-temperature conditions through a combination of low-temperature hydration degumming and two-stage composite microfiltration. The phospholipid content of the degummed oil is controlled to within 5 mg / kg, which avoids the damage to the flavor and nutrition of the oil products caused by traditional high-temperature degumming, decolorization, and deodorization refining processes, and also ensures the clarity and long-term storage stability of the oil products. The total time from crude oil production to finished product bottling is controlled to within 12 hours, which significantly shortens the exposure time of the oil products during processing, further reduces the risk of quality deterioration in the processing stage, and ensures the uniformity and stability of freshness and quality of different batches of products.

[0018] 3. This invention employs a purely physical processing method, eliminating high-temperature refining and organic solvent extraction steps, and introducing no chemical food additives. All equipment, pipes, and containers in direct contact with the oil are made of food-grade stainless steel, and all inert gases used are food-grade. This ensures the food safety of the product throughout the entire processing flow, while simultaneously preventing the formation of harmful substances such as trans fatty acids and polycyclic aromatic hydrocarbons during high-temperature processing. The low-temperature processing technology of this invention significantly reduces energy consumption during production. Compared to traditional hot-pressing refining processes, energy consumption is significantly lower. Low-temperature control during pressing also reduces the thermal denaturation of proteins in peanut cake, allowing the peanut meal to be further used for deep processing such as plant protein extraction, thus improving the comprehensive utilization efficiency of peanut raw materials. Furthermore, the process steps of this invention are adaptable to existing peanut oil industrial production lines, requiring no large-scale modification of core production equipment. The process parameters are highly controllable, operation is convenient, and it combines product quality improvement with adaptability for large-scale industrial production, possessing significant industrial application value. Attached Figure Description

[0019] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are explained in detail together with the embodiments of the invention, but do not constitute a limitation thereof.

[0020] Figure 1 This is to illustrate the complete process flow diagram of the low-temperature freshness-preserving technology of the present invention; Figure 2 This is a flowchart of the low-temperature pretreatment process for raw materials in this invention; Figure 3 This is a diagram of the gradient low-temperature freshness-locking pressing process of the present invention; Figure 4 This is a diagram of the low-temperature static settling process of the present invention; Figure 5 This is a process diagram of the low-temperature composite microfiltration of the present invention. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] like Figures 1-5As shown, the low-temperature freshness-locking peanut oil processing technology of the present invention for enhancing the freshness of peanut oil includes five core steps: low-temperature pretreatment of raw materials, gradient low-temperature freshness-locking pressing, low-temperature static sedimentation, low-temperature composite microfiltration, and low-temperature freshness-locking bottling. A low-temperature hydration degumming step can be added as an auxiliary step. The entire process adopts a light-proof, sealed, and low-oxygen environment control. All equipment, pipelines, and containers that come into direct contact with the oil are made of food-grade 304 / 316L stainless steel. The inert gas used throughout the process is food-grade nitrogen or food-grade argon. The total time from the production of crude oil to the completion of finished product bottling is ≤12 hours.

[0023] Step S1: Low-temperature pretreatment of raw materials Peanut kernels from the current year with a maturity of ≥95% were selected. Moldy kernels, broken kernels, sand, and other impurities were removed through winnowing and screening to obtain clean peanut kernels. The cleaned peanut kernels were then placed in a low-temperature, sealed conditioning chamber. The temperature was controlled at 18℃-22℃ and the relative humidity at 45%-55% for static conditioning treatment for 12-24 hours. After conditioning, the water activity (Aw) of the peanut kernels was controlled at 0.45-0.55. Simultaneously, moisture content was measured at multiple points on the conditioned peanut kernels. The deviation in moisture content at different locations met the uniformity control formula: ; In the formula, This is due to the relative deviation in moisture content. The maximum moisture content of the peanut kernel sample. This represents the minimum moisture content of the peanut kernel sample. The average moisture content of the peanut kernel sample is given.

[0024] After conditioning, the peanut kernels are directly sent to the subsequent pressing process to avoid prolonged contact with air.

[0025] Step S2: Gradient Low-Temperature Pressing for Freshness Preservation The conditioned peanut kernels are fed into a closed hydraulic cold-pressing equipment. The entire pressing process is carried out in a closed environment with an oxygen volume fraction ≤0.5% and an ambient temperature controlled between 15℃ and 25℃. A three-stage gradient pressurization low-temperature pressing process is adopted: the first stage pressurizes to 8MPa-12MPa and holds the pressure for 180s-300s; the second stage pressurizes to 20MPa-25MPa and holds the pressure for 240s-360s; the third stage pressurizes to 35MPa-45MPa and holds the pressure for 600s-900s. The peanut material temperature is monitored in real time during the pressing process, and is controlled to never exceed 45℃, with a temperature rise rate ≤0.03℃ / min. The process parameters of the pressing process meet the critical matching formula for freshness-locking pressing. ; In the formula, K is the critical index for freshness-locking pressing, P is the final pressing pressure in MPa, t is the holding time of the final pressure in s, and T is the peak temperature of the peanut material during the pressing process in °C.

[0026] After pressing, crude peanut oil and peanut cake are obtained. The crude peanut oil is directly and sealed and transported to the subsequent processes to avoid contact with oxygen.

[0027] Optional step: Low-temperature hydration degumming After pressing, the crude peanut oil can undergo low-temperature hydration degumming. The pressed crude oil is sealed and fed into a closed degumming tank equipped with temperature control and stirring devices. The oil temperature is maintained at a constant 35℃-40℃. First, a citric acid aqueous solution (1%-2% by weight of the crude oil, 50% by mass) is added. The stirring device is turned on and mixed at a speed of 60-80 rpm for 10-15 minutes. After stirring, the mixture is allowed to stand for 20-40 minutes. Then, deionized water (2%-4% by weight of the crude oil, at the same temperature as the crude oil) is added and mixed at a speed of 80-100 rpm for 15-20 minutes. After stirring, the mixture is allowed to stand for 30-60 minutes. After standing, a disc centrifuge is used for centrifugation at a speed of 4000-6000 rpm for 10-15 minutes to separate and remove the bottom gum and aqueous phase, yielding degummed clear oil. The phospholipid content of the degummed oil meets the degumming control formula: ; In the formula, This refers to the mass concentration of phospholipids in the oil.

[0028] The degummed and oil-removed material is then transported in a sealed manner to the subsequent settling process.

[0029] Step S3 Low-temperature static settling The crude oil or degummed oil obtained from pressing is sent to a sealed settling tank. The settling tank is kept completely dark, and the internal temperature is maintained at a constant 10℃-15℃. Throughout the settling process, food-grade inert gas is introduced into the tank to maintain a slight positive pressure of 0.02MPa-0.05MPa, preventing the entry of outside air. The oil undergoes natural settling in the tank for 48-72 hours. The turbidity of the oil is monitored periodically during settling, and the rate of decrease in turbidity during settling satisfies the settling efficiency control formula: ; In the formula, The average rate of decrease in turbidity. The initial turbidity of the oil after settling is expressed in NTU. The value represents the oil turbidity after settling for t hours, in NTU; t represents the settling time, in hours.

[0030] After settling is complete, the upper layer of clear oil in the tank is extracted and transported in a sealed manner to the subsequent filtration process, while the bottom sediment is discharged and treated.

[0031] Step S4 Low-temperature composite microfiltration The supernatant oil after sedimentation is fed into a two-stage composite microfiltration system. The entire filtration process is conducted in a constant temperature and low-temperature environment, with the ambient temperature controlled between 12℃ and 18℃. The entire process is carried out in a dark, sealed environment, with the total oxygen contact time between the oil and the environment ≤30 minutes. The two-stage composite microfiltration system consists of a first-stage microfiltration unit and a second-stage microfiltration unit. The first-stage microfiltration uses polypropylene melt-blown filter media with a pore size of 5μm-10μm, and the filtration pressure is controlled at 0.1MPa-0.3MPa, removing larger solid impurities from the oil. The second-stage microfiltration uses polyethersulfone pleated filter media with a pore size of 0.22μm-0.45μm, and the filtration pressure is controlled at 0.2MPa-0.4MPa, removing fine colloidal substances and residual solid impurities from the oil. After two-stage filtration, the filtered clear oil is obtained and transported in a sealed environment to the subsequent filling process.

[0032] Step S5: Low-temperature freshness-locking filling The filtered oil is filled in a light-proof, low-temperature, inert gas atmosphere filling room. The ambient temperature of the filling room is controlled at 15℃-20℃, and the oxygen volume fraction is ≤1%. Before filling, the packaging containers are purged with inert gas using a vacuum-filling alternating purging process, with ≥3 purgings. The absolute pressure of a single vacuum evacuation is ≤1kPa, and the purity of the inert gas used is ≥99.99%. After purging, the residual oxygen rate in the container meets the purging efficiency control formula: ; In the formula, The residual oxygen rate in the container after replacement. This represents the initial air oxygen volume fraction. denoted as the gas replacement rate for a single replacement, and n as the number of replacements.

[0033] During the filling process, inert gas is simultaneously introduced into the container to form a liquid seal, preventing the oil from contacting air. The container is sealed immediately after filling, and the headspace residual oxygen rate after filling meets the critical control formula for freshness preservation. ; In the formula, The headspace residual oxygen content of the oil after filling is expressed as % (%). Set the temperature for oil storage, in °C.

[0034] After bottling, the finished product is a low-temperature fresh-locking peanut oil.

[0035] The finished peanut oil has an initial acid value ≤ 0.15 mg KOH / g, an initial peroxide value ≤ 0.05 g / 100g, and meets the freshness stability control formula: ; In the formula, For storage The peroxide value of Tianhou oil is expressed in g / 100g. This refers to the number of days the finished product has been stored at room temperature in a sealed container, expressed in days (d).

[0036] Example 1 This embodiment provides a low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil. The specific implementation steps are as follows: S1 raw material low-temperature pretreatment Peanut kernels from Shandong harvested that year with a maturity of 98% were selected and impurities were removed through winnowing and screening to obtain cleaned peanut kernels. The cleaned peanut kernels were then placed in a low-temperature, sealed conditioning chamber, with the temperature controlled at 20℃ and the relative humidity at 50%, and allowed to stand for 18 hours for conditioning. After conditioning, the water activity (Aw) of the peanut kernels was 0.50. Moisture content was measured at five points, and the average moisture content of the peanut kernel sample was determined. The maximum moisture content was 6.2%. The minimum moisture content is 6.35%. The relative deviation of moisture content is 6.08%. ; It meets the requirements for uniformity control.

[0037] S2 gradient low-temperature preservation pressing The conditioned peanut kernels were fed into a closed hydraulic cold-pressing equipment. The oxygen volume fraction was 0.3% and the ambient temperature was controlled at 20℃ throughout the pressing process in a closed environment. A three-stage gradient pressurization low-temperature pressing method was used: the first stage increased the pressure to 10MPa and held it for 240s; the second stage increased the pressure to 22MPa and held it for 300s; and the third stage increased the pressure to 40MPa and held it for 900s. The peanut material temperature was monitored in real time during the pressing process. The peak temperature T was 38℃, the temperature rise rate was 0.02℃ / min, and it did not exceed 45℃. The critical index for freshness-locking pressing was calculated. ; It meets the critical matching requirements for freshness-locking pressing.

[0038] S3 Low-Temperature Static Settling The crude oil obtained from pressing was transferred to a sealed, light-proof settling tank. The tank temperature was controlled at 12°C, and food-grade nitrogen was purged throughout the process to maintain a slight positive pressure of 0.03 MPa. Natural settling time was 60 hours. The initial turbidity of the oil after settling was... The turbidity of the oil was 85 NTU after settling for 60 hours. For a given NTU, calculate the average rate of turbidity decrease: ; It meets the requirements for sedimentation efficiency control. After sedimentation is completed, the upper layer of clear oil is extracted and transported to the filtration process in a sealed manner.

[0039] S4 Low Temperature Composite Microfiltration The supernatant oil after sedimentation is sent to a two-stage composite microfiltration system. The ambient temperature is controlled at 15℃ throughout the filtration process, and the entire process is carried out in a sealed, light-protected environment. The cumulative contact time between the oil and ambient oxygen is 22 minutes. The first-stage microfiltration uses polypropylene melt-blown filter media with a pore size of 8μm and a filtration pressure of 0.2MPa; the second-stage microfiltration uses polyethersulfone pleated filter media with a pore size of 0.3μm and a filtration pressure of 0.3MPa. After filtration, the filtered clear oil is transported to the filling process in a sealed environment.

[0040] S5 Low-Temperature Freshness Locking Filling The filtered oil was filled in a light-proof filling room at 18℃ with an oxygen volume fraction of 0.8%. Before filling, the food-grade PET packaging containers underwent vacuum-nitrogen alternating purging four times, with a single vacuum pressure of 0.8 kPa. The nitrogen purity was 99.995%, and the gas replacement rate η for each purging was 98%. The initial air oxygen volume fraction was... The oxygen content is 21%. Calculate the residual oxygen rate in the container after replacement: ; It meets the requirements for replacement efficiency control.

[0041] Nitrogen gas is introduced simultaneously during the filling process to form a liquid seal. The seal is immediately established after filling, and the oil storage temperature is set. Calculate the upper limit for headspace residual oxygen rate control at 25℃: ; In this embodiment, the measured headspace residual oxygen rate after filling was 0.035%, which meets the critical control requirements for freshness-locking storage.

[0042] In this embodiment, the total time from crude oil extraction to finished product bottling is 10 hours, with the entire process conducted in the dark. All equipment, pipes, and containers in contact with the oil are made of food-grade 304 stainless steel. The initial acid value of the finished peanut oil is 0.12 mg KOH / g, and the initial peroxide value is 0.04 g / 100g. After 180 days of sealed storage at room temperature, the measured peroxide value is 0.38 g / 100g, meeting the freshness stability control formula. ; It meets the requirements for freshness stability.

[0043] Example 2 This embodiment provides a low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil. The specific implementation steps are as follows: S1 raw material low-temperature pretreatment Peanut kernels from the current year with a maturity of 96% were selected and impurities were removed through winnowing and screening to obtain clean peanut kernels. The cleaned peanut kernels were then placed in a low-temperature, sealed conditioning chamber, with the temperature controlled at 18℃ and the relative humidity at 45%, and allowed to stand for 24 hours for conditioning. After conditioning, the water activity (Aw) of the peanut kernels was 0.45. Moisture content was measured at five points, and the average moisture content of the peanut kernel sample was determined. The maximum moisture content was 5.8%. The minimum moisture content was 5.94%. The relative deviation of moisture content is 5.66%. ; It meets the requirements for uniformity control.

[0044] S2 gradient low-temperature preservation pressing The conditioned peanut kernels were fed into a closed hydraulic cold-pressing equipment. The oxygen volume fraction was 0.4% and the ambient temperature was controlled at 15℃ throughout the entire pressing process in a closed environment. A three-stage gradient pressurization low-temperature pressing method was used: the first stage increased the pressure to 8MPa and held it for 300s; the second stage increased the pressure to 20MPa and held it for 360s; and the third stage increased the pressure to 35MPa and held it for 900s. The peanut material temperature was monitored in real time during the pressing process. The peak temperature T was 36℃, the temperature rise rate was 0.025℃ / min, and it did not exceed 45℃. The critical index for freshness-locking pressing was calculated. ; It meets the critical matching requirements for freshness-locking pressing.

[0045] Low-temperature hydration degumming After S2, the crude peanut oil undergoes low-temperature hydration degumming treatment: the pressed crude oil is sealed and fed into a sealed degumming tank, with the oil temperature controlled at 35℃. A citric acid aqueous solution (1% by weight, 50% by mass) is added and stirred at 60 rpm for 15 minutes, then allowed to stand for 40 minutes. Next, deionized water (2% by weight, 35℃) is added and stirred at 80 rpm for 20 minutes, then allowed to stand for 60 minutes. After standing, a disc centrifuge is used at 4000 rpm for 15 minutes to remove gums and the aqueous phase, yielding degummed clear oil. The measured phospholipid content of the degummed oil is 4.2 mg / kg, meeting the degumming control formula. ; It meets the requirements for degumming control.

[0046] S3 Low-Temperature Static Settling The degummed oil was transferred to a sealed, light-proof settling tank. The tank temperature was controlled at 10°C, and food-grade argon gas was purged throughout the process to maintain a slight positive pressure of 0.02 MPa. Natural settling time was 72 hours. Initial oil turbidity after settling was... The turbidity of the oil was 95 NTU after settling for 72 hours. Given 6 NTU, calculate the average rate of turbidity decrease: It meets the requirements for sedimentation efficiency control. After sedimentation is completed, the upper layer of clear oil is extracted and transported to the filtration process in a sealed manner.

[0047] S4 Low Temperature Composite Microfiltration The supernatant oil after sedimentation is sent to a two-stage composite microfiltration system. The ambient temperature is controlled at 12℃ throughout the filtration process, and the entire process is carried out in a sealed, light-protected environment. The cumulative contact time between the oil and ambient oxygen is 28 minutes. The first-stage microfiltration uses polypropylene melt-blown filter media with a pore size of 5μm and a filtration pressure of 0.1MPa; the second-stage microfiltration uses polyethersulfone pleated filter media with a pore size of 0.22μm and a filtration pressure of 0.2MPa. After filtration, the filtered clear oil is transported to the filling process in a sealed environment.

[0048] S5 Low-Temperature Freshness Locking Filling The filtered oil was filled in a light-proof filling room at 15℃ with an oxygen volume fraction of 0.9%. Before filling, the food-grade glass packaging containers underwent vacuum-argon alternating purging three times, with a single vacuum pressure of 1 kPa. The argon gas purity was 99.992%, and the gas replacement rate η for each purging was 97%. The initial air oxygen volume fraction was... The oxygen content is 21%. Calculate the residual oxygen rate in the container after replacement: ; It meets the requirements for replacement efficiency control.

[0049] Argon gas is introduced simultaneously during the filling process to form a liquid seal. The seal is immediately established after filling, and the oil storage temperature is set. Calculate the upper limit for headspace residual oxygen rate control at 20℃: ; In this embodiment, the measured headspace residual oxygen rate after filling was 0.042%, which meets the critical control requirements for freshness-locking storage.

[0050] In this embodiment, the total time from crude oil extraction to finished product bottling is 11.5 hours. The entire process is conducted in the dark, and all equipment, pipes, and containers in contact with the oil are made of food-grade 316L stainless steel. The initial acid value of the finished peanut oil is 0.13 mg KOH / g, and the initial peroxide value is 0.042 g / 100g. After 180 days of sealed storage at room temperature, the measured peroxide value is 0.40 g / 100g, meeting the freshness stability control formula. ; It meets the requirements for freshness stability.

[0051] Example 3 This embodiment provides a low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil. The specific implementation steps are as follows: S1 raw material low-temperature pretreatment Peanut kernels from the current year with a maturity of 95% were selected and impurities were removed through winnowing and screening to obtain clean peanut kernels. The cleaned peanut kernels were then placed in a low-temperature, sealed conditioning chamber, with the temperature controlled at 22℃ and the relative humidity at 55%, and allowed to stand for 12 hours for conditioning. After conditioning, the water activity (Aw) of the peanut kernels was 0.55. Moisture content was measured at five points to obtain the average moisture content of the peanut kernel sample. The maximum moisture content is 6.5%. The minimum moisture content was 6.78%. The relative deviation of moisture content is 6.46%. ; It meets the requirements for uniformity control.

[0052] S2 gradient low-temperature preservation pressing The conditioned peanut kernels were fed into a closed hydraulic cold-pressing equipment. The entire pressing process was conducted in a closed environment with an oxygen volume fraction of 0.5% and an ambient temperature controlled at 25℃. A three-stage gradient pressurization low-temperature pressing method was used: the first stage increased the pressure to 12MPa and held it for 180s; the second stage increased the pressure to 25MPa and held it for 240s; and the third stage increased the pressure to 45MPa and held it for 850s. The peanut material temperature was monitored in real time during the pressing process. The peak temperature T was 44℃, and the temperature rise rate was 0.03℃ / min, not exceeding 45℃. The critical index for freshness-locking pressing was calculated. ; It meets the critical matching requirements for freshness-locking pressing.

[0053] S3 Low-Temperature Static Settling The crude oil obtained from pressing was transferred to a sealed, light-proof settling tank. The tank temperature was controlled at 15°C, and food-grade nitrogen was purged throughout the process to maintain a slight positive pressure of 0.05 MPa. Natural settling time was 48 hours. Initial oil turbidity after settling was... The turbidity of the oil was 80 NTU after settling for 48 hours. Given 18 NTU, calculate the average rate of turbidity decrease: ; It meets the requirements for sedimentation efficiency control. After sedimentation is completed, the upper layer of clear oil is extracted and transported to the filtration process in a sealed manner.

[0054] S4 Low Temperature Composite Microfiltration The supernatant oil after sedimentation is sent to a two-stage composite microfiltration system. The ambient temperature is controlled at 18℃ throughout the filtration process, and the entire process is carried out in a sealed, light-protected environment. The cumulative contact time between the oil and ambient oxygen is 30 minutes. The first-stage microfiltration uses polypropylene melt-blown filter media with a pore size of 10μm and a filtration pressure of 0.3MPa; the second-stage microfiltration uses polyethersulfone pleated filter media with a pore size of 0.45μm and a filtration pressure of 0.4MPa. After filtration, the filtered clear oil is transported to the filling process in a sealed environment.

[0055] S5 Low-Temperature Freshness Locking Filling The filtered oil was filled in a light-proof filling room at 20℃ and with an oxygen volume fraction of 1%. Before filling, the food-grade tinplate packaging containers underwent vacuum-nitrogen alternating purging five times. Each vacuum was applied at an absolute pressure of 0.5 kPa, and the nitrogen purity was 99.99%. The gas replacement rate η for each purging was 99%, and the initial air oxygen volume fraction was... The oxygen content is 21%. Calculate the residual oxygen rate in the container after replacement: ; It meets the requirements for replacement efficiency control.

[0056] Nitrogen gas is introduced simultaneously during the filling process to form a liquid seal. The seal is immediately established after filling, and the oil storage temperature is set. Calculate the upper limit for headspace residual oxygen rate control at 4℃: ; In this embodiment, the measured headspace residual oxygen rate after filling was 0.065%, which meets the critical control requirements for freshness-locking storage.

[0057] In this embodiment, the total time from crude oil extraction to finished product bottling is 9 hours, with the entire process conducted in the dark. All equipment, pipes, and containers in contact with the oil are made of food-grade 304 stainless steel. The initial acid value of the finished peanut oil is 0.14 mg KOH / g, and the initial peroxide value is 0.048 g / 100g. After 180 days of sealed storage at room temperature, the measured peroxide value is 0.405 g / 100g, meeting the freshness stability control formula. ; It meets the requirements for freshness stability.

[0058] This invention addresses the industry pain points of traditional peanut oil processing, such as high-temperature pressing and refining leading to oil oxidation, flavor decomposition, and nutrient loss, as well as poor parameter matching and insufficient oxygen contact control in ordinary cold pressing processes, resulting in short product freshness retention periods and large batch quality fluctuations. Through a systematic process design with low temperature, airtight, and low oxygen throughout the entire process, this invention achieves full-chain preservation of the original freshness of peanut oil. In the raw material pretreatment stage, the water activity and moisture distribution uniformity of peanut kernels are precisely controlled through low-temperature closed conditioning, ensuring the stability of the pressed oil while avoiding flavor deterioration caused by the enzymatic reaction of the raw materials themselves. In the pressing stage, a three-stage gradient pressurization low-temperature pressing process combined with a freshness-locking pressing critical matching formula quantifies and controls the matching relationship between pressure, holding time, and material temperature, strictly controlling the peak temperature of peanut material during the pressing process below 45℃. This inhibits the occurrence of thermal oxidation and thermal decomposition reactions of the oil from the source, maximizing the preservation of the original flavor substances, vitamin E, phytosterols, and other active nutrients in peanut oil. Combined with a fully closed conveying process and inert gas atmosphere protection, the probability and duration of contact between the oil and oxygen are significantly reduced, significantly lowering the initial acid value and peroxide value of the oil, achieving long-term preservation of the original freshness of peanut oil and extending the product's shelf life.

[0059] This invention constructs a closed-loop control system for the entire process parameters of peanut oil processing through multi-dimensional quantitative control formulas, solving the problems of traditional peanut oil processing relying on manual experience, lack of quantitative matching standards for process parameters, and large batch-to-batch product quality fluctuations. In the raw material conditioning stage, the moisture uniformity control formula ensures batch consistency of raw material pretreatment; in the sedimentation stage, the sedimentation efficiency control formula achieves standardized judgment of the sedimentation process endpoint; in the filling stage, the replacement efficiency control formula and the freshness-locking storage critical control formula achieve precise control of residual oxygen rate inside the packaging, ensuring that the process parameters of each step have clear quantitative control boundaries. Meanwhile, this invention achieves efficient removal of gums and solid impurities from oil products under low-temperature conditions through a combination of low-temperature hydration degumming and two-stage composite microfiltration. The phospholipid content of the degummed oil is controlled to within 5 mg / kg, which avoids the damage to the flavor and nutrition of the oil products caused by traditional high-temperature degumming, decolorization, and deodorization refining processes, and also ensures the clarity and long-term storage stability of the oil products. The total time from crude oil production to finished product bottling is controlled to within 12 hours, which significantly shortens the exposure time of the oil products during processing, further reduces the risk of quality deterioration in the processing stage, and ensures the uniformity and stability of freshness and quality of different batches of products.

[0060] This invention employs a purely physical processing method, eliminating high-temperature refining and organic solvent extraction steps, and introducing no chemical food additives. All equipment, pipes, and containers in direct contact with the oil are made of food-grade stainless steel, and all inert gases used are food-grade. This ensures the food safety of the product throughout the entire processing flow, while simultaneously preventing the formation of harmful substances such as trans fatty acids and polycyclic aromatic hydrocarbons during high-temperature processing. The low-temperature processing technology of this invention significantly reduces energy consumption during production, resulting in a substantial reduction in energy consumption compared to traditional hot-pressing refining processes. Low-temperature control during pressing also reduces the thermal denaturation of proteins in the peanut cake, allowing the peanut meal to be further used in deeper processing stages such as plant protein extraction, thus improving the comprehensive utilization efficiency of peanut raw materials. Furthermore, the process steps of this invention are adaptable to existing peanut oil industrial production lines, requiring no large-scale modification of core production equipment. The process parameters are highly controllable, operation is convenient, and it combines product quality improvement with adaptability for large-scale industrial production, demonstrating significant industrial application value.

[0061] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely preferred examples and are not intended to limit the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of the present invention is defined by the appended claims and their equivalents.

Claims

1. A low-temperature freshness-locking peanut oil processing technology to enhance the freshness of peanut oil, comprising peanut kernel pretreatment, pressing, sedimentation, filtration, and bottling steps, characterized in that, The specific steps are as follows: S1 Raw Material Low Temperature Pretreatment: Select peanut kernels with a maturity of ≥95%, remove impurities, and then condition them in a low temperature and sealed environment to control the water activity of the peanut kernels to a preset range. S2 Gradient Low-Temperature Fresh-Locking Pressing: Conditioned peanut kernels are fed into a closed hydraulic cold-pressing equipment for three-stage gradient low-temperature pressing. The ambient temperature is controlled between 15℃ and 25℃ throughout the pressing process, and the peanut material temperature never exceeds 45℃. The process parameters meet the critical matching formula for fresh-locking pressing. ； In the formula, K is the critical index for freshness-locking pressing, and P is the final pressing pressure, in MPa. t represents the final pressure holding time, in seconds; T represents the peak temperature of the peanut material during the pressing process, in °C. S3 Low-Temperature Static Settling: The crude oil obtained by pressing is sent into a sealed settling tank and allowed to settle naturally in a dark and low-temperature environment. Inert gas is introduced throughout the settling process to maintain a slight positive pressure. S4 Low-Temperature Composite Microfiltration: The supernatant oil after sedimentation is sent into a two-stage composite microfiltration system for graded filtration in a constant temperature and low-temperature environment to remove solid impurities and colloidal substances, and obtain filtered clean oil. S5 Low-Temperature Freshness-Locking Filling: Filtered oil is filled in a light-proof, low-temperature, inert gas atmosphere. Before filling, the packaging container is purged with inert gas. After filling, the headspace residual oxygen rate meets the critical control formula for freshness-locking storage. ； In the formula, The headspace residual oxygen content of the oil after filling is expressed as % (%). Set the temperature for oil storage, in °C; After bottling, the finished product is a low-temperature fresh-locking peanut oil.

2. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In step S1, the temperature of the low-temperature sealed environment is controlled at 18℃-22℃, the relative humidity is controlled at 45%-55%, the conditioning time is 12h-24h, and the water activity Aw of the peanut kernels after conditioning is controlled at 0.45-0.

55. The moisture content deviation at different locations of the peanut kernels meets the uniformity control formula: ； In the formula, This is due to the relative deviation in moisture content. The maximum moisture content of the peanut kernel sample. This represents the minimum moisture content of the peanut kernel sample. The average moisture content of the peanut kernel sample is given.

3. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In step S2, the specific parameters of the three-stage gradient pressurization low-temperature pressing are as follows: the first stage pressurization is increased to 8MPa-12MPa, and the pressure holding time is 180s-300s; the second stage pressurization is increased to 20MPa-25MPa, and the pressure holding time is 240s-360s; the third stage pressurization is increased to 35MPa-45MPa, and the pressure holding time is 600s-900s. The oxygen volume fraction in the closed environment throughout the pressing process is ≤0.5%, and the heating rate of peanut material is ≤0.03℃ / min.

4. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In step S3, the temperature inside the settling tank is constantly controlled at 10℃-15℃, the settling time is 48h-72h, the inert gas pressure maintained inside the tank is 0.02MPa-0.05MPa, and the rate of decrease in oil turbidity during the settling process satisfies the settling efficiency control formula: ; In the formula, The average rate of decrease in turbidity. The initial turbidity of the oil after settling is expressed in NTU. The value represents the oil turbidity after settling for t hours, in NTU; t represents the settling time, in hours.

5. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In step S4, the constant temperature and low temperature environment of the two-stage composite microfiltration system are controlled at 12℃-18℃. The first-stage microfiltration uses polypropylene meltblown filter material with a pore size of 5μm-10μm and a filtration pressure of 0.1MPa-0.3MPa. The second-stage microfiltration uses polyethersulfone pleated filter material with a pore size of 0.22μm-0.45μm and a filtration pressure of 0.2MPa-0.4MPa. The total oxygen contact time between the oil and the environment during the entire filtration process is ≤30min.

6. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In step S5, the inert gas replacement of the packaging container adopts a vacuum-filling alternating replacement process, with ≥3 replacements, an absolute pressure of ≤1kPa for each vacuuming, and an inert gas purity ≥99.99%. After replacement, the residual oxygen rate in the container meets the replacement efficiency control formula: ; In the formula, The residual oxygen rate in the container after replacement. This represents the initial air oxygen volume fraction. denoted as the gas replacement rate for a single replacement, and n as the number of replacements.

7. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 3, characterized in that, After step S2 is completed and before step S3 begins, a low-temperature hydration degumming step is also included: the pressed crude oil is sent into a sealed degumming tank, and under the condition of oil temperature of 35℃-40℃, 1%-2% of citric acid aqueous solution by weight of crude oil is added, stirred and mixed, and allowed to stand for 20min-40min. Then, 2%-4% of deionized water by weight of crude oil is added, stirred and mixed, and allowed to stand for 30min-60min. The gums are removed by centrifugation. After degumming, the phospholipid content of the oil meets the degumming control formula. ； In the formula, This represents the mass concentration of phospholipids in the oil.

8. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, Steps S1 to S5 are conducted in a light-proof manner. All equipment, pipes and containers that come into direct contact with the oil are made of food-grade 304 / 316L stainless steel. The inert gas used throughout the process is food-grade nitrogen or food-grade argon. The total time from the production of crude oil to the completion of finished product bottling is ≤12 hours.

9. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In the critical matching formula for freshness-locking pressing in step S2, the preferred range of K value is [0.95, 1.15], the value range of the final pressing pressure P is 38MPa-42MPa, the value range of the final pressure holding time t is 700s-800s, and the peak temperature of peanut material during the pressing process is T≤42℃.

10. The low-temperature freshness-locking peanut oil processing technology for enhancing peanut oil freshness according to claim 1, characterized in that, In the critical control formula for freshness-locking storage in step S5, the set temperature for oil storage is... The values ​​range from 4℃ to 25℃. After bottling, the initial acid value of the finished peanut oil is ≤0.15mgKOH / g, the initial peroxide value is ≤0.05g / 100g, and it meets the freshness stability control formula: ； In the formula, For storage The peroxide value of Tianhou oil is expressed in g / 100g. This refers to the number of days the finished product has been stored at room temperature in a sealed container, expressed in days (d).

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