Method for preparing fishy smell-removed soybean oil through cooperation of infrared rays and high-frequency pulses

Abstract

The invention discloses a method for preparing deodorized soybean oil through infrared and high-frequency pulse cooperation, and belongs to the technical field of food. In order to solve the problems of nutrition loss, peculiar smell rebound and low efficiency of a traditional deodorization process or a single technology in the prior art, the invention provides a method for preparing deodorized soybean oil by infrared and high-frequency pulse, and the deodorized soybean oil is prepared by infrared pretreatment for 30-120 minutes at 90-150 DEG C and high-frequency pulse treatment for 15-35 kV, 100-1000 Hz, 2-10 us and 60-210 s. The enzyme activity inhibition-precursor release-peculiar smell degradation triple mechanism is constructed, the fishy smell removal and aroma enhancement effects are achieved, a green and efficient solution is provided for high-quality soybean oil processing, and the method has wide application prospects.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of food technology, and particularly relates to a method for preparing deodorized soybean oil by infrared synergistic high-frequency pulse. BACKGROUND

[0002] Soybean oil, as one of the largest edible vegetable oils in the world, its flavor quality directly determines the consumer acceptance and market premium ability. However, the inherent "beany flavor" of soybean has become the core bottleneck restricting its high-value utilization. The beany flavor mainly comes from the oxidation of unsaturated fatty acids (linoleic acid, linolenic acid) catalyzed by lipoxygenase (LOX) in the pre-processing and middle period, generating volatile aldehydes, ketones, alcohols such as hexanal, pentanal and 2-pentyl furan; these substances are easily released and enriched in the processing process, forming strong beany flavor and grassy flavor, not only covering the natural aroma of soybean oil itself, but also possibly causing consumer sensory rejection.

[0003] The traditional deodorization process in the prior art has the following difficult-to-overcome side effects: (1) chemical method: relying on alkaline reagents or adsorbents, although it can neutralize or adsorb part of the odor substances, it is easy to introduce exogenous chemical residues, and at the same time, it irreversibly destroys the natural antioxidant accompanying substances (vitamin E, sterol) of oil, reducing the nutritional value; (2) high temperature method: by >200 ℃ high temperature steaming and frying to inactivate LOX activity, however, excessive heating will cause deep denaturation of protein, and intensify Maillard reaction, which in turn generates secondary off-flavors such as burnt smell and bitter taste, and a large amount of heat-sensitive nutrients are lost, the product has a single aroma, which cannot meet the market demand of "strong aroma" healthy oil products; (3) physical method: vacuum degassing, activated carbon adsorption and other low-temperature physical methods have no chemical residues, but the removal efficiency of low-boiling-point aldehyde ketone odor substances is low, the treatment time is long, and it is difficult to realize industrialized deep deodorization.

[0004] In recent years, non-thermal processing technology has been tried for soybean deodorization due to its "low temperature, high efficiency and less loss"; however, single technology has obvious process blind area: (1) infrared pretreatment, if the temperature field distribution is uneven, the surface material will be quickly carbonized, and the internal LOX inactivation will not be complete; (2) high-frequency pulse electric field can break cells in milliseconds and promote the release of odor substances, but the electric field energy distribution is affected by the dielectric difference of the material, resulting in large spatial difference in cell wall breaking rate and insufficient release of odor substances.

[0005] Therefore, the skilled in the art is eager to study a compound deodorization strategy without chemical addition, low temperature, short time and industrialization. SUMMARY

[0006] The present application provides a method for preparing deodorized soybean oil by infrared synergistic high-frequency pulse to solve the problems of nutrient loss, off-flavor rebound and low efficiency in the traditional deodorization process or single technology in the prior art.

[0007] One objective of this invention is to provide a method for preparing deodorized soybean oil using infrared-assisted high-frequency pulses, the method comprising the following steps: S1: Select mold-free soybean seeds as oilseeds, clean and remove impurities, adjust the moisture content of the oilseeds to 10.0±0.5%, spread the treated oilseeds evenly in a petri dish, and control the material thickness to 2 cm. S2: Place the petri dish from S1 into an intelligent infrared drying oven for infrared pretreatment, soak the treated oilseeds in distilled water, and adjust the moisture content of the oilseeds to 30%. S3: Spread the oilseeds processed in S2 evenly in the pulse electric field processing chamber and perform high-frequency pulse processing; S4: The oilseeds processed in S3 are dried in a 40℃ oven until the moisture content is 6%-8%. They are then pressed using a screw press to collect crude oil. The crude oil is then refined to obtain deodorized soybean oil.

[0008] In a preferred embodiment of the present invention, the intelligent infrared drying chamber in S2 has a voltage of 220V and a power of 5kW.

[0009] In a preferred embodiment of the present invention, the infrared pretreatment time in S2 is 30 min-120 min and the temperature is 90℃-150℃.

[0010] In a preferred embodiment of the present invention, the pulse voltage of the high-frequency pulse processing in S3 is 15kV-35kV, the pulse frequency is 100 Hz-1000 Hz, the pulse width is 2 μs-10 μs, and the material residence time is 60 s-210 s.

[0011] In a preferred embodiment of the present invention, the pressing step in S4 is as follows: first, the screw oil press is preheated to 180°C-200°C, and the dried oilseeds are fed into the feed inlet of the screw oil press so that the oilseeds are evenly pushed in the pressing chamber and crude oil is collected.

[0012] In a preferred embodiment of the present invention, the power of the screw oil press is 820 W.

[0013] In a preferred embodiment of the present invention, the crude oil refining step in S4 is as follows: the crude oil is first subjected to sedimentation or filtration to remove impurities, and then the crude oil is subjected to deacidification, decolorization and dewaxing treatment, without deodorization treatment.

[0014] The second objective of this invention is to provide a deodorized soybean oil, which is prepared by the above-described method.

[0015] Compared with existing technologies, the beneficial effects of this invention are as follows: This invention prepares deodorized soybean oil through infrared synergy with a high-frequency pulsed electric field. Specifically, firstly, the surface of soybean seeds is selectively heated by infrared pretreatment (treatment temperature 90℃-150℃, time 30 min-120 min) to precisely thermally inactivate lipoxygenase. Under the control of 90℃~150℃, the spatial structure of the enzyme protein undergoes irreversible denaturation, cutting off the enzymatic generation pathway of odorous aldehydes, represented by hexanal, from the source, thereby achieving precise control of lipoxygenase (LOX) activity and reducing the generation of odorous precursors. Then, the instantaneous high-voltage electric field (15kV-35kV) generated by the high-frequency pulsed electric field exerts its electroporation effect to physically modify the cell membrane structure, causing reversible or irreversible perforation of the cell membrane, increasing cell membrane permeability, and promoting the accelerated release of residual enzymes and generated precursors of odor from the cell to the outside. This process not only eliminates potential odor hazards but also greatly optimizes the channels and efficiency of subsequent oil extraction.

[0016] This invention utilizes the synergistic effect of infrared radiation and high-frequency pulsed electric fields to jointly promote "flavor transformation and sublimation." The high-frequency pulsed treatment, while promoting the release of cell contents, also "pushes" a large amount of flavor precursors such as free amino acids and reducing sugars together, creating a more complete reaction interface. At this time, the heat accumulated during infrared pretreatment and the potentially warm environment during oil extraction provide ideal thermodynamic conditions for the Maillard reaction and the formation of pyrazines. This invention, through this combined treatment, powerfully promotes the Maillard reaction and the formation of pyrazines. This reaction pathway directly competes with the lipid oxidation pathway that produces fishy aldehydes, guiding the reaction substrate towards the formation of heterocyclic compounds such as pyrazines with "roasted" and "nutty" aromas. Sensoryly, this results in a sharp reduction of unpleasant "grassy" flavors, while pleasant "oily" and "roasted" aromas and a rich "fatty" flavor are significantly enhanced. Ultimately, this achieves a qualitative leap from "removing fishy odors" to "enhancing aroma," thus winning high consumer recognition.

[0017] This invention provides a method for preparing deodorized soybean oil using infrared-assisted high-frequency pulsed electric fields, which has the following advantages: (1) Synergistic and efficient deodorization: Through the synergistic effect of infrared pretreatment and high-frequency pulse, a triple mechanism of "enzyme activation inhibition - precursor release - odor degradation" is constructed, which reduces the content of odor substances (such as hexanal) by more than 80%, and the deodorization efficiency is significantly better than that of single technology.

[0018] (2) High retention of flavor substances: Low temperature (40℃) drying + refining process avoids flavor loss caused by high temperature or chemical treatment, and retains flavor substances such as characteristic aroma pyranone and lactone at a rate of over 90%.

[0019] (3) Strong industrial adaptability: The key parameters of the system optimization (infrared time 30-180 min, high frequency pulse electric field dwell time 60 s-210 s) are controllable, and the equipment is compatible with conventional industrial equipment (such as 820 W screw oil press), which is suitable for large-scale production.

[0020] (4) Green and environmentally friendly: The entire process is physical and coordinated, without the need for chemical reagents, and the carbon emissions are reduced by more than 40% compared with traditional processes, which is in line with the concept of green processing. Attached Figure Description

[0021] Figure 1 To quantitatively describe and analyze radar charts. Detailed Implementation

[0022] Those skilled in the art can refer to the content of this document and appropriately improve the process parameters to achieve the desired results. It should be particularly noted that all similar substitutions and modifications are obvious to those skilled in the art and are considered to be included in this invention. The methods and applications of this invention have been described through preferred embodiments, and those skilled in the art can obviously make modifications or appropriate alterations and combinations to the methods and applications described herein without departing from the content and scope of this invention to implement and apply the technology of this invention.

[0023] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to specific embodiments. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the materials, reagents, methods, and instruments used are all conventional materials, reagents, methods, and instruments in the art, and can be obtained commercially by those skilled in the art.

[0024] Example 1: S1: Select mold-free soybean seeds as oilseeds, clean and remove impurities, adjust the moisture content of the oilseeds to 10.0±0.5%, spread the treated oilseeds evenly in a petri dish with a diameter of 18 cm, and control the thickness of the material to 2 cm. S2: Place the petri dish from S1 in an intelligent infrared drying oven (voltage is 220V, power is 5kW) for infrared pretreatment (treatment time is 60 min, treatment temperature is 90℃), soak the treated oilseeds in distilled water, and adjust the moisture content of the oilseeds to 30%. S3: The oilseeds processed in S2 are evenly spread in the pulse electric field treatment chamber and subjected to high-frequency pulse treatment (pulse voltage is 15 kV, material residence time is 184 s, pulse frequency range is 810 Hz, and pulse width is 8 μs). S4: The oilseeds processed in S3 are placed in a 40℃ oven and dried until the moisture content is 6%-8%. They are then pressed using a screw press preheated to 180℃ to collect crude oil. The crude oil is then refined (the refining process involves filtering to remove impurities, followed by deacidification, decolorization, and dewaxing of the crude oil. No deodorization is performed, taking advantage of the excellent flavor quality of the crude oil itself and avoiding the catastrophic loss of aroma caused by deodorization) to obtain deodorized soybean oil 1.

[0025] Example 2: The difference between this embodiment and embodiment 1 is that the infrared pretreatment time in S2 is 60 min and the temperature is 120℃; the pulse voltage of the high-frequency pulse treatment in S3 is 25 kV, the material residence time is 184 s, the pulse frequency range is 810 Hz, and the pulse width is 8 μs; the other steps are the same as in embodiment 1, and deodorized soybean oil 2 is obtained.

[0026] Example 3: The difference between this embodiment and embodiment 1 is that the infrared pretreatment time in S2 is 60 min and the temperature is 150℃; the pulse voltage of the high-frequency pulse treatment in S3 is 35 kV, the material residence time is 184 s, the pulse frequency range is 810 Hz, and the pulse width is 8 μs; the other steps are the same as in embodiment 1, and deodorized soybean oil 3 is obtained.

[0027] Comparative Example 1: The difference between this comparative example and Example 1 is that infrared pretreatment and high-frequency pulse treatment are not performed; the other steps are the same as in Example 1, and deodorized soybean oil 4 is obtained.

[0028] Comparative Example 2: The difference between this comparative example and Example 2 is that high-frequency pulse processing is not performed; the other steps are the same as in Example 2, and deodorized soybean oil 5 is obtained.

[0029] Comparative Example 3: The difference between this comparative example and Example 2 is that no infrared pretreatment is performed; the other steps are the same as in Example 2, and deodorized soybean oil 6 is obtained.

[0030] Comparative Example 4: The difference between this comparative example and Example 2 is that the crude oil refining step involved a conventional deodorization process; the other steps were the same as in Example 2, resulting in deodorized soybean oil 7.

[0031] Comparative Example 5: The difference between this comparative example and Example 1 is that the infrared pretreatment time in S2 is 150 min and the temperature is 60℃; the pulse voltage of the high-frequency pulse treatment in S3 is 45 kV, the material residence time is 184 s, the pulse frequency range is 810 Hz, and the pulse width is 8 μs; the other steps are the same as in Example 1, and deodorized soybean oil 8 is obtained.

[0032] Comparative Example 6: The difference between this comparative example and Example 1 is that the infrared pretreatment time in S2 is 60 min and the temperature is 200℃; the pulse voltage of the high-frequency pulse treatment in S3 is 10 kV, the material residence time is 184 s, the pulse frequency range is 810 Hz, and the pulse width is 8 μs; the other steps are the same as in Example 1, and deodorized soybean oil 9 is obtained.

[0033] Comparative Example 7: The difference between this comparative example and Example 1 is that the pulse voltage of the high-frequency pulse treatment in S3 is 15kV, the material residence time is 250s, the pulse frequency range is 80 Hz, and the pulse width is 1 us; the other steps are the same as in Example 1, and 10g of deodorized soybean oil is obtained.

[0034] Comparative Example 8: The difference between this comparative example and Example 1 is that the infrared pretreatment time in S2 is 60 min and the temperature is 120℃; the pulse voltage of the high-frequency pulse treatment in S3 is 25 kV, the material residence time is 50 s, the pulse frequency range is 1200 Hz, and the pulse width is 11 μs; the other steps are the same as in Example 1, and deodorized soybean oil 11 is obtained.

[0035] Comparative Example 9: The difference between this comparative example and Example 1 is that the infrared pretreatment time in S2 is 150 min and the temperature is 60℃; the pulse voltage of the high-frequency pulse treatment in S3 is 45 kV, the material residence time is 250 s, the pulse frequency range is 80 Hz, and the pulse width is 11 μs; the other steps are the same as in Example 1, and deodorized soybean oil 12 is obtained.

[0036] Effect Experiment: 1. Sensory evaluation According to the scoring criteria described in Table 1, 12 members of the sensory panel evaluated the deodorized soybean oil obtained above from 1 to 12 based on consumer flavor preferences, ranging from 1 (very disliked flavor) to 9 (very liked flavor). The freshly pressed soybean oil was placed in paper cups and given to each evaluator for scoring.

[0037] The scoring results are shown in Table 2. The deodorized soybean oils 1-3 prepared using the method provided by this invention (Examples 1-3) obtained high sensory evaluation scores.

[0038] Table 1

[0039] Table 2

[0040] 2. Quantitative analysis Twelve participants were recruited and underwent a week of sensory training to ensure they could identify the aroma of the oil. The deodorized soybean oils 1-12 obtained above were analyzed for aroma (including grassy, ​​roasted, oily, burnt, spicy, and bitter almond aromas). Each aroma attribute was scored from 0 to 3, with a 1-minute interval between samples. Each sample was evaluated 3 times, and the results are expressed as the average.

[0041] The beany smell is a mixture of the beany, grassy, ​​and pungent odors found in beans. Figure 1 As can be seen from the quantitative descriptive analysis radar chart, compared with the deodorized soybean oil 4-12 prepared in Comparative Examples 1-9, the grassy smell of the deodorized soybean oil 1-3 prepared in Examples 1-3 gradually decreased, while the oily aroma, fatty aroma, and roasted aroma gradually increased.

[0042] 3. GC-MS analysis of flavor components The volatile flavor components of the deodorized soybean oils 1-12 obtained above were collected using SPME technology, and the volatile aroma components were separated and identified using GC-MS technology. A 7890B-5977MSD GC-MS system (Agilent Technologies) was used, with an HP-5 column.

[0043] The specific steps are as follows: SPME conditions: A manual solid-phase microextraction device (extraction head: 50 / 30cm CAR / PDMS / DVB) was used to collect and inject volatile components from flavor oil samples. 5 g of flavor oil sample was weighed and poured into a sample bottle. The extraction temperature was 60℃, the extraction time was 30 min, the equilibration time was 40 min, and the resolution time was 3 min.

[0044] GC conditions: 40 °C for 3 min, increase to 80 °C at 5 °C / min and hold for 5 min; increase to 160 °C at 10 °C / min and hold for 2 min; increase to 230 °C at 10 °C / min and hold for 8 min; carrier gas (He) flow rate is 1 mL / min.

[0045] MS conditions: electron energy 70 eV; transfer line temperature 280 °C; ion source temperature 230 °C; mass scan range m / z 30-450; characteristic volatile compounds were identified by comparing the experimental mass spectral library with the NIST 17 mass spectral library, retention index (RI), and odor description (O).

[0046] Hexanal is the main representative of the beany odor, while total pyrazine is the main representative of the aroma. As shown in Table 3, the deodorized soybean oil 3 obtained after infrared synergistic high-frequency pulse treatment had the lowest hexanal content (0.0623 mg / kg), while the total pyrazine content remained at a relatively high level of 8.47%. This is because after high-degree heat treatment, the hexanal content decreased or became undetectable, but a certain amount of phenylacetaldehyde, 2-methylbutyraldehyde, and 2-methylpentanaldehyde were newly generated. In the initial stage of high temperature, the rate of oil oxidation to hexanal is very fast. As time goes by, the most easily oxidized unsaturated fatty acids in the oil are largely consumed, reducing the "raw materials" for hexanal generation, and its generation rate will gradually decrease. Hexanal is highly volatile and will volatilize in large quantities. At the same time, the "raw materials" (phenylalanine) for the generation of phenylacetaldehyde (which plays a role in enhancing aroma, hyacinth, floral, and sweet flavors) are continuously dissolved or exposed from the oil, with a relatively stable and sufficient supply.

[0047] The hexanal content of the deodorized soybean oil 4-12 prepared by Comparative Examples 1-9 was maintained at 0.48-0.51 mg / kg, and the pyrazine content was only 4.15-7.34%. This indicates that the method for preparing deodorized soybean oil by infrared synergistic high-frequency pulse provided by the present invention, under the preferred parameter combination, can simultaneously achieve "removal of fishy smell" and "preservation of aroma".

[0048] Table 3

[0049] 4. Detection of residual lipoxygenase (LOX) activity Referring to GB / T 5523-2008 "Grain and Oil Inspection: Determination of Lipoxygenase Activity in Grains and Oilseeds", the deodorized soybean oils 1-12 obtained above were tested for residual lipoxygenase (LOX) activity.

[0050] 5. Detection of soybean oil acid value (AV) The acid value (AV) of the deodorized soybean oils 1-12 obtained above was tested in accordance with the national standard GB 5009.299-2016 "National Food Safety Standard - Determination of Acid Value in Food".

[0051] 6. Soybean oil peroxide value (PV) test Referring to the national standard GB 5009.227-2023 "National Food Safety Standard - Determination of Peroxide Value in Food", the peroxide value (PV) of the deodorized soybean oils 1-12 obtained above was tested.

[0052] 7. Detection of anisidine value (p-AnV) in soybean oil The anisidine value (p-AnV) of the deodorized soybean oils 1-12 obtained above was tested according to GB / T 24304-2009 "Determination of anisidine value of animal and vegetable oils".

[0053] 8. Vitamin E test Referring to GB 5009.82-2016 "National Food Safety Standard - Determination of Vitamins A, D and E in Food", the vitamin E content of the deodorized soybean oils 1-12 obtained above was tested.

[0054] As shown in Table 4, the acid value (≤3mg / g) and peroxide value (≤0.25g / 100g) of the deodorized soybean oils 1-3 (Examples 1-3) obtained after infrared synergistic high-frequency pulse treatment all meet the national standards. The residual LOX activity was precisely suppressed to 3-7%, the odor precursor was released and degraded, the hexanal was reduced by more than 80%, and the total pyrazine was increased by more than 20%. Among them, the deodorized soybean oil 3 had the lowest residual LOX activity (3.06%), the lowest peroxide value (0.028 g / 100 g), and the vitamin E was well preserved (184 mg / 100 g).

[0055] In contrast, the deodorized soybean oil prepared in Comparative Example 1 had a residual LOX activity as high as 95.0%, indicating that infrared-assisted high-frequency pulses are significantly superior to conventional treatment in reducing enzyme activity and inhibiting primary oxidation.

[0056] Table 4

[0057] Therefore, this invention proposes a two-step physical synergy approach: selective infrared heating (90-150℃, 30-120 min) + high-frequency pulsed electric field (15-35 kV, 60-210 s, 100 Hz-1000 Hz, 2 us-10 us). This approach first precisely deactivates lipoxygenase on the surface of oilseed grains, reducing the formation of odor precursors. Then, instantaneous high-pressure perforation promotes the release and degradation of the precursors, achieving the goal of removing beany odor, enhancing oil aroma, and maximizing the retention of active substances (vitamin E). No chemical reagents are required throughout the process. By limiting the infrared time to 30-180 min, the pulse dwell time to 60-210 s, and the low-temperature drying at 40℃, a triple mechanism of "enzyme activity inhibition - precursor release - odor degradation" is achieved. This reduces hexanal by more than 80%, pyrazine retention rate ≥90%, and LOX residual activity <5%, with a significant decrease in peroxide value. The process parameters are directly compatible with the equipment (820 W screw oil press), demonstrating the innovative characteristics of being green, efficient, and industrially scalable.

[0058] The specific embodiments of the present invention disclosed above are merely illustrative of the invention. These embodiments do not exhaustively describe all details, nor do they limit the invention to the specific embodiments described. Many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention.

Claims

1. A method for preparing deodorized soybean oil using infrared-assisted high-frequency pulse, characterized in that, The method includes the following steps: S1: Select mold-free soybean seeds as oilseeds, clean and remove impurities, adjust the moisture content of the oilseeds to 10.0±0.5%, spread the treated oilseeds evenly in a petri dish, and control the material thickness to 2 cm. S2: Place the petri dish from S1 into an intelligent infrared drying oven for infrared pretreatment, soak the treated oilseeds in distilled water, and adjust the moisture content of the oilseeds to 30%. S3: Spread the oilseeds processed in S2 evenly in the pulse electric field processing chamber and perform high-frequency pulse processing; S4: The oilseeds processed in S3 are dried in a 40℃ oven until the moisture content is 6%-8%. They are then pressed using a screw press to collect crude oil. The crude oil is then refined to obtain deodorized soybean oil.

2. The method according to claim 1, characterized in that, The intelligent infrared drying oven described in S2 has a voltage of 220V and a power of 5kW.

3. The method according to claim 1, characterized in that, The infrared pretreatment time in S2 is 30 min-120 min, and the temperature is 90℃-150℃.

4. The method according to claim 1, characterized in that, The high-frequency pulse processing described in S3 has a pulse voltage of 15kV-35kV, a pulse frequency of 100 Hz-1000 Hz, a pulse width of 2 μs-10 μs, and a material residence time of 60 s-210 s.

5. The method according to claim 1, characterized in that, The pressing steps described in S4 are as follows: First, preheat the screw oil press to 180℃-200℃, then feed the dried oilseeds into the feed inlet of the screw oil press, so that the oilseeds are evenly pushed into the pressing chamber and crude oil is collected.

6. The method according to claim 5, characterized in that, The power of the screw oil press is 820 W.

7. The method according to claim 1, characterized in that, The crude oil refining steps described in S4 are as follows: first, the crude oil is subjected to sedimentation or filtration to remove impurities, and then the crude oil is subjected to deacidification, decolorization, and dewaxing treatments, without deodorization treatment.

8. A deodorized soybean oil, characterized in that, The deodorized soybean oil is prepared by the method described in any one of claims 1 to 7.

Images