Method for targeted activation of endogenous enzymes in flax seed for maintaining particle morphology and debittering and flavoring

Abstract

This invention discloses a method for targeted activation of endogenous enzymes and debittering / fragrance enhancement in flaxseed while maintaining its granular shape. The method includes the following steps: microcrack treatment of flaxseed; spraying an ethanol-water solution onto the surface of the flaxseed to create a slightly moist state; heating and conditioning in a heat-preserving conditioning device to activate the endogenous cyanogenic glycoside hydrolytic enzyme system; short-term heat treatment under closed or semi-closed negative pressure conditions and introducing cyanide-containing exhaust gas into an exhaust gas treatment system; and cooling and tempering to obtain debittered and fragrance-enhanced flaxseed. This invention, through the synergistic effect of microcrack treatment and ethanol-water wetting, effectively activates endogenous enzymes to promote cyanogenic glycoside hydrolysis and removal of volatile cyanide-containing components under extremely low wetting solution addition conditions, while simultaneously inhibiting the hydration and swelling of seed coat mucilage. This results in treated flaxseed maintaining a dispersed granular state and good flowability, suitable for subsequent continuous pressing processing.

Description

Technical Field

[0001] This invention relates to the field of oilseed crop processing technology, specifically to a method for targeted activation of endogenous enzymes in flaxseed to maintain particle morphology and for debittering and enhancing aroma. Background Technology

[0002] Flaxseed is a common oilseed crop, containing oils, proteins, dietary fiber, lignans, and alpha-linolenic acid. Flaxseed can be used to produce flaxseed oil, flaxseed meal, and related food or feed ingredients. Flaxseed also contains a certain amount of cyanogenic glycosides, which can hydrolyze in the presence of moisture and upon contact with endogenous enzymes, producing volatile cyanide-containing components such as hydrogen cyanide. These cyanogenic glycosides and their hydrolysis products affect the flavor and safety of processed flaxseed products; therefore, appropriate debittering, decyanation, or conditioning treatments are usually required during flaxseed processing.

[0003] In current flaxseed pressing processing, common pretreatment methods include simple cleaning before cold pressing, roasting or steaming before hot pressing, soaking, fermentation, microwave treatment, and puffing. Cold pressing helps reduce the loss of heat-sensitive components, but its effect on the degradation of cyanogenic glycosides in flaxseed is limited. Heat treatment methods such as roasting, steaming, puffing, or microwave treatment can promote the degradation of some cyanogenic glycosides and the removal of volatile cyanide-containing components, but high treatment intensity can easily cause oil oxidation or excessive changes in flavor. Wet treatments such as soaking and fermentation can promote the action of endogenous enzymes or microbial enzymes, but flaxseed coats contain mucilage, which easily absorbs water and swells upon contact with water, causing the particles to stick together, resulting in reduced material flowability, which is not conducive to subsequent continuous pressing.

[0004] Furthermore, the penetration rate of water into the seed coat and internal tissues of intact flaxseed kernels is relatively slow, which limits the contact between cyanogenic glycoside substrates and endogenous enzymes. Simply relying on short-term wetting and conditioning is insufficient to fully utilize the function of endogenous enzymes; while increasing the amount of water or extending the wet processing time can easily exacerbate mucilage leakage and kernel agglomeration. These factors make it difficult to simultaneously achieve the goals of debittering and decyanating flaxseeds, maintaining kernel shape, reducing the risk of sticking, and adapting to continuous pressing.

[0005] Therefore, it is necessary to provide a pretreatment method for flaxseed before pressing, which improves water transfer efficiency and endogenous enzyme activity efficiency without processing the flaxseed into a paste, promotes the directional hydrolysis of cyanogenic glycosides and the removal of volatile cyanide-containing components, and inhibits excessive hydration of flaxseed mucilage and particle adhesion, so that the treated flaxseed maintains good particle shape and flowability, and further improves the flavor quality of the pressed product. Summary of the Invention

[0006] Based on the problems existing in the background technology, the present invention provides a method for targeted activation of endogenous enzymes and debittering and aroma enhancement of flaxseed while maintaining particle morphology. This method is used to improve the efficiency of endogenous enzyme action before flaxseed pressing, promote the hydrolysis of cyanogenic glycosides and the removal of volatile cyanide-containing components, reduce particle adhesion and material flowability caused by wet conditioning, and make the treated flaxseed suitable for subsequent continuous pressing processing.

[0007] This invention is implemented through the following technical solutions: A method for targeted activation, debittering, and aroma enhancement of endogenous enzymes in flaxseed while maintaining its granular shape, comprising the following steps: S1. Perform micro-crack treatment on flax seeds to create micro-cracks in the seed coat or near the seed coat area; S2. Spray an ethanol aqueous solution onto the surface of the flaxseeds obtained in step S1 to make the surface of the flaxseeds slightly moist and keep the particles dispersed and flowing. S3. The flaxseed obtained in step S2 is heated and conditioned in a heat preservation and conditioning device to activate the endogenous cyanogenic glycoside hydrolytic enzyme system in the flaxseed, and the cyanogenic glycosides are hydrolyzed. S4. The flaxseeds obtained in step S3 are subjected to short-time heat treatment under closed or semi-closed negative pressure conditions, and the gas generated during the treatment is introduced into the exhaust gas treatment system. S5. Cool and temper the flax seeds obtained in step S4 to obtain flax seeds that have undergone debittering and aroma enhancement treatment.

[0008] Further, in step S1, the microcrack treatment is carried out using one of the following methods: twin-roller fracturing, differential roller fracturing, elastic roller fracturing, vibration fracturing, or low-intensity impact fracturing.

[0009] Further, in step S1, the contact pressure for the microcrack treatment is 3~10MPa. The roller gap or impact intensity of the fracturing equipment is adjusted through sampling and testing to ensure that the treated flaxseed meets the following output indicators: crack depth does not exceed 10%~20% of the seed thickness; the breakage rate of the treated flaxseed is not higher than 5%, and the proportion of cracked seeds is 60%~90%. When the raw material particle size fluctuates significantly, differential speed rollers or elastic rollers should be preferred for fracturing to improve pressure adaptability. The channels formed by microcracks on the seed coat can significantly shorten the path of moisture diffusion into the inner layer of the seed coat during subsequent conditioning, while simultaneously increasing the contact area between the cyanogenic glycoside substrate and the endogenous enzyme system.

[0010] Furthermore, before step S1, there is also a raw material moisture adjustment step: adjusting the moisture content of flaxseed to 6%~10%; when the moisture content is below 6%, water is added by short-term rehydration, and when the moisture content is above 10%, the moisture content is reduced by low-temperature ventilation or low-temperature drying.

[0011] Further, in step S2, the ethanol aqueous solution has an ethanol volume fraction of 10% to 25%, and the spraying amount is 2.5% to 5.0% of the flaxseed mass; the spraying method is continuous atomization spraying or pulse atomization spraying, and the spraying and mixing time is 1 to 5 minutes.

[0012] Furthermore, in step S2, the ethanol-water solution also contains reducing sugar, which is one or more of glucose, xylose, fructose or maltose, and the amount of reducing sugar added is 0.05% to 0.30% of the flaxseed mass.

[0013] The presence of ethanol in the wetting solution effectively reduces the hydration rate of mucilage, preventing excessive dissolution of seed coat mucilage and thus preventing particle adhesion. Simultaneously, water penetrates through microcracks, providing the necessary water activity for the activation of endogenous enzyme systems. After wetting, flaxseed particles are slightly moist and dispersed, not forming a continuous paste, and exhibit good flowability.

[0014] Furthermore, in step S3, the conditioning temperature is 45~50℃, the conditioning time is 25~40 minutes, the relative humidity of the conditioning environment is 65%~85%, and the flaxseeds are intermittently turned or continuously turned at low speed; the conditioning device is equipped with an exhaust port connected to the exhaust gas treatment system.

[0015] Furthermore, in step S4, the short-time heat treatment adopts one of the following methods: superheated steam, hot air, infrared, microwave, microwave-hot air combination, or infrared-hot air combination; the surface treatment temperature of flaxseed is 105~130℃, and the treatment time is 45~180 seconds; under the closed or semi-closed negative pressure conditions, the vacuum degree inside the treatment chamber is -5~-50 kPa.

[0016] Further, in step S4, the exhaust gas treatment system includes one or more of the following: an alkaline absorption device, an oxidation absorption device, a condensation device, an activated carbon adsorption device, or a catalytic oxidation device.

[0017] Further, in step S5, the cooling and tempering time is 5 to 20 minutes, and the pressing temperature after tempering is 40 to 65°C; the cooling method is one of natural tempering, ventilation cooling, low-temperature airflow cooling or stirring cooling; after step S5, the flax seeds that have undergone debittering and aroma enhancement treatment are sent into the oil pressing equipment for pressing, and the oil pressing equipment is a single screw oil press or a twin screw oil press.

[0018] The beneficial effects of this invention are: 1. This invention fundamentally solves the problem of excessive hydration and seepage of mucilage in the seed coat and particle agglomeration during flaxseed conditioning by combining microcrack treatment with low-moisture ethanol wetting. Microcracks increase the water diffusion channels, allowing water to effectively penetrate the inner layer of the seed coat and activate endogenous cyanogenic glycoside hydrolytic enzymes even with extremely low total wetting solution addition (not exceeding 5.0% of flaxseed mass). Simultaneously, the introduction of ethanol significantly inhibits the swelling rate of the mucilage, ensuring the wetted material remains in a dispersed state with good flowability, allowing it to be directly pressed in a screw oil press without additional drying, crushing, or granulation processes, thus simplifying the process and reducing energy consumption.

[0019] 2. This invention employs a two-stage decyanation strategy combining endogenous enzymatic hydrolysis and closed-loop short-time thermal decyanation, significantly improving the efficiency of cyanogenic glycoside removal. In the conditioning stage, the endogenous cyanogenic glycoside hydrolytic enzyme system fully hydrolyzes the cyanogenic glycosides into volatile cyanide-containing components under suitable temperature and humidity conditions. In the thermal decyanation stage, the closed negative pressure condition promotes the rapid escape of volatile cyanide-containing components from microcrack channels, which are then effectively collected by the exhaust gas treatment system, thus balancing decyanation efficiency and safe emission requirements.

[0020] 3. Compared with traditional high-temperature cooking or long-term strong heat treatment, the present invention adopts a short-time heat treatment method (105~130℃ for the surface layer, 45~180 seconds), which can effectively reduce the degree of thermal oxidation of α-linolenic acid in flaxseed oil while ensuring the decyanation effect, and reduce the loss of heat-sensitive functional components such as vitamin E and lignans, thus helping to obtain pressed oil with lower peroxide value and better oxidative stability.

[0021] 4. In the embodiment where a small amount of food-grade reducing sugar is added to the wetting solution and combined with dry heat short-time heat treatment (such as infrared, hot air or a combination thereof), a mild Maillard reaction can occur on the surface of flaxseed. This reaction works synergistically with the dry heat processing method used to impart roasted and nut-like aromas to pressed oil and cake without causing charring or significant oil oxidation, thereby improving product flavor and meeting the needs of differentiated product development. Detailed Implementation

[0022] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the scope of protection of the present invention is not limited to the following embodiments.

[0023] The flaxseed raw materials used in the examples and comparative examples were from the same batch. Each example and comparative example used 1000g of flaxseed raw material with an initial moisture content of 7.8% (no further moisture adjustment is needed in actual operation). The total cyanogenic glycoside content, calculated as hydrogen cyanide equivalent, was 276 mg / kg. The total oil content (dry basis) was 41.2%, the proportion of α-linolenic acid in the total fatty acids was 54.6%, and the lignan content (calculated as open-ring isolarcilide diglucoside SDG) was 25.4 mg / g (dry basis). Ethanol was food grade with a purity ≥95% (v / v); glucose, xylose, fructose, and maltose were all food grade.

[0024] Example 1: A method for targeted activation, debittering, and aroma enhancement of endogenous enzymes in flaxseed while maintaining its granular shape, comprising the following steps: S1. Micro-crack treatment: Flaxseeds are fed into a two-roller cracker, and the roller gap is adjusted to make the contact pressure 5 MPa. After treatment, the crack depth is about 15% of the seed thickness, the proportion of cracked seeds is about 75%, and the material breakage rate is 2.8%.

[0025] S2, Ethanol-water solution spraying: Pulse atomize and spray an ethanol-water solution (ethanol volume fraction 15%) onto the pretreated flaxseed while it is continuously turned over. The amount sprayed is 3.5% of the flaxseed mass (i.e. 35 g), and the spraying and mixing time is 2 min. After spraying, the surface of the material is slightly moist, the particles are dispersed and flow, and there is no obvious adhesion.

[0026] S3. Heat preservation and conditioning: Transfer the material into the conditioning tower, control the temperature at 47℃ and the relative humidity at 75%, and keep it at this temperature for 30 minutes, turning it over every 5 minutes during the process; connect the exhaust port of the conditioning device to a 5% NaOH alkaline solution absorption tower to absorb the small amount of HCN that escapes during the enzymatic hydrolysis process.

[0027] S4. Short-time heat treatment: The conditioned flaxseed is sent into a superheated steam treatment machine. The treatment chamber is evacuated to -20 kPa. The superheated steam outlet temperature is 140°C, the surface treatment temperature of the flaxseed is 115°C, and the treatment time is 90 seconds. The HCN-containing tail gas generated during the treatment process is introduced into the NaOH alkaline solution absorption tower through a pipeline for further absorption.

[0028] S5. Cooling and pressing: After processing, the material is cooled and tempered by ventilation for 10 minutes until the material temperature drops to 50°C. Then, it is sent to a single screw oil press for pressing to obtain pressed oil and cake.

[0029] Example 2: A method for targeted activation, debittering, and aroma enhancement of endogenous enzymes in flaxseed while maintaining its granular shape, comprising the following steps: S1. Micro-crack treatment: Flaxseeds are fed into a differential roller crusher. The roller spacing and the speed difference between the upper and lower rollers are adjusted to make the contact pressure 8 MPa. After treatment, the crack depth is about 18% of the seed thickness, the proportion of cracked seeds is about 85%, and the material breakage rate is 4.2%.

[0030] S2, Ethanol-water spraying: Dissolve glucose in 20% ethanol-water solution at a dosage of 0.20% of flaxseed mass to prepare an ethanol-water wetting solution containing reducing sugar; continuously atomize and spray the above wetting solution onto the pretreated flaxseed while it is continuously turning over, the amount of spraying is 4.5% of the flaxseed mass (i.e. 45 g), and the spraying and mixing time is 3 min; after spraying, the surface of the material is slightly moist, the particles are dispersed and flowing, and there is no obvious adhesion.

[0031] S3. Heat preservation and conditioning: Transfer the material into the conditioning tower, control the temperature at 48℃ and the relative humidity at 80%, and keep it at this temperature for 35 minutes, during which time it is continuously turned over at a low speed; connect the exhaust port of the conditioning device to a 5% NaOH alkaline solution absorption tower to absorb the small amount of HCN that escapes during the enzymatic hydrolysis process.

[0032] S4. Short-time heat treatment: The conditioned flaxseed is sent into an infrared-hot air composite treatment machine. The treatment chamber is evacuated to -30 kPa. The infrared radiation intensity and hot air temperature are adjusted to make the surface temperature of the flaxseed reach 125℃. The treatment time is 120 seconds. The HCN-containing tail gas generated during the treatment process is introduced into the NaOH alkaline absorption tower through a pipeline for further absorption.

[0033] S5. Cooling and pressing: After processing, the material is cooled and tempered by low-temperature airflow for 15 minutes until the material temperature drops to 55℃. Then, it is sent to a single screw oil press for pressing to obtain pressed oil and cake.

[0034] Example 3: A method for targeted activation, debittering, and aroma enhancement of endogenous enzymes in flaxseed while maintaining its granular shape, comprising the following steps: S1. Micro-crack treatment: Flaxseeds are fed into an elastic roller cracker, and the roller spacing is adjusted to make the contact pressure 4 MPa. After treatment, the crack depth is about 12% of the seed thickness, the proportion of cracked seeds is about 65%, and the material breakage rate is 2.0%.

[0035] S2. Ethanol-water solution spraying: Glucose and xylose are mixed at a mass ratio of 1:1. The total amount of the mixed reducing sugar is 0.10% of the flaxseed mass, which is pre-dissolved in an ethanol-water solution with a volume fraction of 12% to prepare an ethanol-water wetting solution containing reducing sugar. The above wetting solution is pulse-atomized and sprayed onto the pretreated flaxseed under continuous turning conditions. The amount of spraying is 3.0% of the flaxseed mass (i.e., 30 g), and the spraying and mixing time is 2 min. After spraying, the surface of the material is slightly moist, the particles are dispersed and flowing, and there is no obvious adhesion.

[0036] S3. Heat preservation and conditioning: Transfer the material into the conditioning tower, control the temperature at 45℃ and the relative humidity at 70%, and keep it at this temperature for 40 minutes. During this period, turn the material intermittently (once every 8 minutes). Connect the exhaust port of the conditioning device to a 5% NaOH alkaline solution absorption tower to absorb the small amount of HCN that escapes during the enzymatic hydrolysis process.

[0037] S4. Short-time heat treatment: The conditioned flaxseeds are sent into a microwave-hot air composite treatment machine. The treatment chamber is evacuated to -15 kPa. The microwave power and hot air temperature are adjusted to make the surface temperature of the flaxseeds reach 110℃. The treatment time is 150 seconds. The HCN-containing tail gas generated during the treatment process is introduced into the NaOH alkaline absorption tower through a pipeline for further absorption.

[0038] S5. Cooling and pressing: After processing, the material is naturally cooled for 12 minutes until the temperature drops to 48°C. Then, it is sent to a single screw oil press for pressing to obtain pressed oil and cake.

[0039] Comparative Example 1: A method for pre-processing flaxseed during pressing includes the following steps: S1. No micro-crack treatment: No pressure cracking is applied to the flaxseed seed coat in this step. The flaxseeds remain in their original, intact state and proceed directly to the next step.

[0040] S2, Ethanol-water solution spraying: Pulse atomize and spray an ethanol-water solution (ethanol volume fraction 15%) onto the original flaxseeds while continuously turning them over. The amount sprayed is 3.5% of the flaxseed mass (i.e., 35 g), and the spraying and mixing time is 2 min.

[0041] S3. Heat preservation and conditioning: Transfer the material into the conditioning tower, control the temperature at 47℃ and the relative humidity at 75%, and keep it at this temperature for 30 minutes, turning it over every 5 minutes during the process; connect the exhaust port of the conditioning device to a 5% NaOH alkaline solution absorption tower to absorb the small amount of HCN that escapes during the enzymatic hydrolysis process.

[0042] S4. Short-time heat treatment: The conditioned flaxseed is sent into a superheated steam treatment machine. The treatment chamber is evacuated to -20 kPa. The superheated steam outlet temperature is 140°C, the surface treatment temperature of the flaxseed is 115°C, and the treatment time is 90 seconds. The HCN-containing tail gas generated during the treatment process is introduced into the NaOH alkaline solution absorption tower through a pipeline for further absorption.

[0043] S5. Cooling and pressing: After processing, the material is cooled and tempered by ventilation for 10 minutes until the material temperature drops to 50°C. Then, it is sent to a single screw oil press for pressing to obtain pressed oil and cake.

[0044] Comparative Example 2: A method for pre-processing flaxseed during pressing includes the following steps: S1. Micro-crack treatment: Flaxseeds are fed into a two-roller cracker, and the roller gap is adjusted to make the contact pressure 5 MPa. After treatment, the crack depth is about 15% of the seed thickness, the proportion of cracked seeds is about 75%, and the material breakage rate is 2.8%.

[0045] S2. Pure water spraying: Deionized water is pulse-atomized and sprayed onto the pretreated flaxseed under continuous agitation. The amount of water sprayed is 3.5% of the flaxseed mass (i.e., 35 g), and the spraying and mixing time is 2 min. After spraying, the surface of the material is wet, and obvious adhesion tends to be observed between the particles.

[0046] S3. Heat preservation and conditioning: Transfer the material into the conditioning tower, control the temperature at 47℃ and the relative humidity at 75%, and keep it at this temperature for 30 minutes, turning it over every 5 minutes during the process. During the conditioning process, a large amount of mucilage in the seed coat of the material will hydrate and seep out, and the aggregation between particles will intensify. The exhaust port of the conditioning device is connected to a 5% NaOH alkaline solution absorption tower to absorb the small amount of HCN that escapes during the enzymatic hydrolysis.

[0047] S4. Short-time heat treatment: Because the material has been severely agglomerated after conditioning, it is first crushed by a crusher and dispersed through a 4 mm sieve, and then sent to a superheated steam treatment machine. The treatment chamber is evacuated to -20 kPa, the superheated steam outlet temperature is 140℃, the flaxseed surface treatment temperature is 115℃, and the treatment time is 90 seconds. The HCN-containing tail gas generated during the treatment process is introduced into the NaOH alkaline solution absorption tower through a pipeline for further absorption.

[0048] S5. Cooling and pressing: After processing, the material is cooled and tempered by ventilation for 10 minutes until the material temperature drops to 50°C. Then, it is sent to a single screw oil press for pressing to obtain pressed oil and cake.

[0049] Comparative Example 3: A traditional high-temperature steaming, roasting, and pressing pretreatment method for flaxseed includes the following steps: S1. Steaming and roasting treatment: Place flax seeds in a horizontal steaming and roasting pot, and introduce saturated steam (steam temperature about 121℃). After the material temperature rises to 120℃, maintain it for 30 minutes. During the steaming and roasting process, the moisture content of the material gradually rises to about 18%, and the material becomes semi-paste.

[0050] S2. Hot air drying: Transfer the steamed and roasted material into a hot air dryer. The hot air temperature is 60~70℃. Dry continuously until the material moisture content is about 6%. During the drying process, some material forms a slight adhesion on the surface due to the dissolution of mucus. The material color changes from yellowish brown to dark brown.

[0051] S3. Crushing and sieving: The dried material is crushed into agglomerates by a roller crusher and then sieved through a 4 mm standard sieve to obtain dispersible and flowable flaxseed particles.

[0052] S4. Pressing: The crushed and sieved flaxseeds are fed into the same single-screw oil press as in Example 1 for pressing to obtain pressed oil and cake.

[0053] Comparative Example 4 A method for direct low-temperature cold pressing of flaxseed includes the following steps: S0. Raw materials: Take 1000 g of flaxseed raw materials (initial moisture content 7.8%).

[0054] S1. Cleaning: The flaxseeds are screened to remove impurities such as stems, soil clods, and stones, resulting in clean flaxseeds.

[0055] S2. Low-temperature cold pressing: The cleaned flaxseeds are directly fed into the same single-screw oil press as in Example 1 for low-temperature cold pressing. During the pressing process, the temperature of the machine chamber does not exceed 60°C, and no heat treatment, wetting or conditioning pretreatment is performed. After pressing, the pressed oil and cake are collected.

[0056] Experimental example: The pressed oil and cake obtained by the above method in each embodiment and comparative example were subjected to performance tests, and the test methods are as follows: 1) Agglomeration rate: After processing, flaxseed is passed through a 4 mm standard sieve. The percentage of agglomerates on the sieve relative to the total mass is the agglomeration rate.

[0057] 2) Hydrolysis rate of cyanogenic glycosides during conditioning stage: After conditioning and before heat treatment, samples are taken to determine the residual cyanogenic glycosides (in HCN equivalent). The hydrolysis rate (%) is calculated as follows: (amount of raw material cyanogenic glycosides − amount of residual cyanogenic glycosides after conditioning) / amount of raw material cyanogenic glycosides × 100%.

[0058] 3) Hydrogen cyanide equivalent in pressed oil and cake: determined by headspace gas chromatography, according to GB 5009.36-2023. The measured hydrogen cyanide content is converted to mg / kg based on the sample mass.

[0059] 4) Oil yield: Calculated on a dry basis of flaxseed, oil yield (%) = mass of oil obtained by pressing / dry basis of flaxseed × 100%.

[0060] 5) Acid value and peroxide value of pressed oil: determined according to GB 5009.229-2025 and GB 5009.227-2023 respectively, and expressed as mg KOH / g and mmol / kg respectively.

[0061] 6) α-Linolenic acid content in pressed oil: determined according to GB 5009.168-2016 method, α-linolenic acid retention rate (%) = α-linolenic acid content in treated flaxseed oil / α-linolenic acid content corresponding to raw material × 100% (the α-linolenic acid content measured by low temperature solvent extraction of the same batch of raw materials is used as 100% benchmark).

[0062] 7) Lignin retention rate: Calculated as SDG, the lignan retention rate (%) was determined by high performance liquid chromatography. The lignan retention rate (%) = total SDG in the treated cake and oil / total SDG in the raw material × 100%.

[0063] 8) Sensory evaluation: Ten professionally trained evaluators will conduct blind evaluations of the pressed oil, and give a comprehensive score based on three aspects: flavor purity, nutty aroma intensity, and bitterness (reverse). The maximum score is 10 points, with 1 point being the worst and 10 points being the best. The average score will be taken.

[0064] The test results are shown in Tables 1 and 2.

[0065] Table 1. Process evaluation indicators for each embodiment and comparative example

[0066] As shown in Table 1, the agglomeration rate of materials in Examples 1-3 was no more than 5%, and the materials maintained good particle dispersion and flowability, allowing them to be directly fed into a screw oil press for continuous pressing. In contrast, the agglomeration rate of Comparative Example 2 (using pure water instead of ethanol solution) was as high as 35.6%, with the materials clearly clumping together. It required crushing and sieving before entering the pressing process, demonstrating that the inhibitory effect of ethanol on the hydration and swelling of seed coat mucilage in step S2 was crucial for maintaining particle integrity in this invention. In Comparative Example 1 (omitting microcrack treatment), the cyanogenic glycoside hydrolysis rate during the conditioning stage was only 52.8%, corresponding to an HCN residue of 6.5 mg / kg in the pressed oil, significantly higher than the 1.2 mg / kg in Example 1. This indicates that the microcrack channels formed in step S1 significantly improved the mass transfer efficiency of water and endogenous enzymes to the inner layer of the seed coat, which is the basis for the targeted activation of the endogenous cyanogenic glycoside hydrolytic enzyme system and the improvement of cyanogenic glycoside hydrolysis efficiency. The HCN residue in the pressed oil of Examples 1-3 did not exceed 2 mg / kg, and the HCN residue in the cake did not exceed 5 mg / kg, which is far below the limit of 10 mg / kg for cyanide in edible oils specified in GB 2762-2025. However, the HCN residue in the oil of Comparative Example 4 (direct low-temperature cold pressing, without decyanation pretreatment) reached 18.5 mg / kg, which exceeded the national standard limit, verifying the significant advantages of the process of this invention in terms of decyanation safety.

[0067] Regarding the flavor (sensory evaluation) of the pressed oil, Example 1 (without added reducing sugar) scored 7.5, exhibiting a typical flaxseed aroma without bitterness; Example 2 (with 0.20% glucose added) scored 8.7, with a rich nutty aroma and a pronounced roasted aroma; Example 3 (with 0.10% mixed reducing sugar added) scored 8.3, with a mellow aroma. Comparative Example 3 (traditional steaming and roasting) scored 6.8, exhibiting a certain degree of burnt aroma and oxidized oil flavor; Comparative Example 4 (direct cold pressing) scored 4.2, with a pronounced bitterness, which is related to the high HCN residue and unhydrolyzed cyanogenic glycosides in the oil. The results indicate that the combination of sugar addition and dry heat short-time heat treatment (infrared-hot air, microwave-hot air) can synergistically generate mild Maillard reaction products and pyrolysis aroma products on the surface, significantly improving the product flavor without causing oil oxidation and charring.

[0068] Table 2. Quality and nutritional components of pressed oils from each example and comparative example.

[0069] As shown in Table 2, the acid value of the pressed oils in Examples 1-3 did not exceed 1.7 mg KOH / g and the peroxide value did not exceed 3 mmol / kg, which were significantly better than the acid value of 2.35 mg KOH / g and the peroxide value of 5.10 mmol / kg in Comparative Example 3 (traditional steaming and roasting process). Although Examples 1-3 experienced relatively mild conditions of 45-50℃ during the conditioning stage, the total amount of wetting liquid accounted for only 2.5%-5.0% of the flaxseed mass and contained 10%-25% ethanol, resulting in low water activity and a limited window for effective lipase action. The subsequent short-term heat treatment (45-180 seconds) rapidly inactivated the lipase, limiting the accumulation of enzymatic hydrolysis. In contrast, Comparative Example 3 was subjected to high temperature and high humidity (moisture content rose to approximately 18%) for 30 minutes, accompanied by significant thermal hydrolysis of triglycerides and the generation of secondary products of oil oxidation. This, combined with the cumulative oxidation during the long-term drying process at 60-70℃, is the main reason why its acid value was significantly higher than that of the Examples.

[0070] The α-linolenic acid retention rate in Examples 1-3 was no less than 95%, and the lignan retention rate was no less than 89%, representing a significant improvement compared to 88.5% and 75.6% in Comparative Example 3, respectively. This indicates that the "low-moisture wetting and conditioning + short-time heat treatment" strategy employed in this invention significantly reduces the thermal oxidation loss of α-linolenic acid and the damage to heat-sensitive functional components compared to traditional long-term high-temperature steaming and frying. It should be noted that although Comparative Example 4 (direct cold pressing) had the highest α-linolenic acid and lignan retention rates (99.0% and 96.8%, respectively), the lack of decyanation treatment resulted in severely excessive HCN levels in the oil, rendering it impractical for use. In summary, the process of this invention achieves a good balance between decyanation safety and nutritional quality preservation.

[0071] Finally, it should be noted that the above embodiments are merely illustrative of several implementations of the present invention and are not intended to limit the scope of the invention. For those skilled in the art, any modifications, equivalent substitutions, or improvements made without departing from the concept of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A method for targeted activation and debittering / fragranting of endogenous enzymes in flaxseed while maintaining its granular shape, characterized in that, Includes the following steps: S1. Perform micro-crack treatment on flax seeds to create micro-cracks in the seed coat or near the seed coat area; S2. Spray an ethanol aqueous solution onto the surface of the flaxseeds obtained in step S1 to make the surface of the flaxseeds slightly moist and keep the particles dispersed and flowing. S3. The flaxseed obtained in step S2 is heated and conditioned in a heat preservation and conditioning device to activate the endogenous cyanogenic glycoside hydrolytic enzyme system in the flaxseed, and the cyanogenic glycosides are hydrolyzed. S4. The flaxseed obtained in step S3 is subjected to short-time heat treatment under closed or semi-closed negative pressure conditions, and the gas generated during the treatment is introduced into the exhaust gas treatment system. S5. Cool and temper the flax seeds obtained in step S4 to obtain flax seeds that have undergone debittering and aroma enhancement treatment.

2. The method according to claim 1, characterized in that, In step S1, the microcrack treatment is carried out using one of the following methods: twin-roller fracturing, differential roller fracturing, elastic roller fracturing, vibration fracturing, or low-intensity impact fracturing.

3. The method according to claim 1, characterized in that, In step S1, the contact pressure for the microcrack treatment is 3~10MPa.

4. The method according to claim 1, characterized in that, Before step S1, there is also a raw material moisture adjustment step: adjust the moisture content of flaxseed to 6%~10%; when the moisture content is lower than 6%, replenish the water by short-term rehydration, and when the moisture content is higher than 10%, reduce the moisture content by low-temperature ventilation or low-temperature drying.

5. The method according to claim 1, characterized in that, In step S2, the volume fraction of ethanol in the ethanol-water solution is 10% to 25%, and the amount sprayed is 2.5% to 5.0% of the flaxseed mass; the spraying method is continuous atomization spraying or pulse atomization spraying, and the spraying and mixing time is 1 to 5 minutes.

6. The method according to claim 1, characterized in that, In step S2, the ethanol-water solution also contains reducing sugar, which is one or more of glucose, xylose, fructose or maltose, and the amount of reducing sugar added is 0.05% to 0.30% of the flaxseed mass.

7. The method according to claim 1, characterized in that, In step S3, the conditioning temperature is 45~50℃, the conditioning time is 25~40 minutes, the relative humidity of the conditioning environment is 65%~85%, and the flax seeds are intermittently turned or continuously turned at low speed; the conditioning device is equipped with an exhaust port connected to the exhaust gas treatment system.

8. The method according to claim 1, characterized in that, In step S4, the short-time heat treatment adopts one of the following methods: superheated steam, hot air, infrared, microwave, microwave-hot air combination, or infrared-hot air combination; the surface treatment temperature of flaxseed is 105~130℃, and the treatment time is 45~180 seconds; under the closed or semi-closed negative pressure conditions, the vacuum degree inside the treatment chamber is -5~-50 kPa.

9. The method according to claim 1, characterized in that, In step S4, the exhaust gas treatment system includes one or more of the following: an alkaline absorption device, an oxidation absorption device, a condensation device, an activated carbon adsorption device, or a catalytic oxidation device.

10. The method according to claim 1, characterized in that, In step S5, the cooling and tempering time is 5 to 20 minutes, and the pressing temperature after tempering is 40 to 65°C. The cooling method is one of natural tempering, ventilation cooling, low-temperature airflow cooling, or stirring cooling. After step S5, the flax seeds that have undergone debittering and aroma enhancement treatment are sent to the oil pressing equipment for pressing. The oil pressing equipment is a single-screw oil press or a twin-screw oil press.

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