Flavored oil processing technology for improving phenolic nutrient substances

Abstract

The invention relates to the field of food processing, and discloses a flavor oil processing technology for improving phenolic nutrient substances, which comprises the following steps: (1) mixing oil seeds with water, and carrying out low-temperature treatment at 20 DEG C or below to obtain wetted oil seeds; (2) stir-frying and squeezing the wetted oil seeds to obtain first crude oil and an oil cake; (3) mixing the oil cake with water, performing heat treatment, and performing oil extraction to obtain second crude oil; and (4) mixing the first crude oil and the second crude oil to obtain the vegetable oil. By adopting the method disclosed by the invention, the content of polyphenol, sterol and flavor substances in the vegetable oil can be further improved.

Description

Technical Field

[0001] The invention relates to the field of food processing, and in particular to a flavor oil processing technology for increasing phenolic nutrients. Background Art

[0002] Plant polyphenols is a general term for polyhydroxyphenol compounds existing in plants, mainly including flavonoids, tannins, anthocyanins, phenolic acids, etc. Phenolic substances exist in plants mainly in free and bound states. Free phenols refer to phenolic compounds that do not interact physically or chemically with other macromolecules; bound phenols are polyphenols that are bound to food matrices (such as cell wall substances) via covalent bonds, and need to be separated from the cell wall by chemical or enzymatic treatment methods.

[0003] Rapeseed is rich in polyphenols, 10-30 times that of other oil seeds. The polyphenols in rapeseed mainly include free phenolic acids such as sinapic acid, caffeic acid, ferulic acid, canolol, and bound polyphenols such as sinapine. These polyphenols can be called "rapeseed polyphenols" or "rapeseed phenols". In recent years, phenolic compounds widely present in oil-containing plants have been shown to contribute to their therapeutic properties, including anti-cancer, antiviral, antioxidant, hypoglycemic, lipid-lowering and anti-inflammatory activities, and have very important application value. Therefore, how to increase the content of polyphenols in rapeseed oil is of great significance.

[0004] "Effect of dry frying on rapeseed polyphenols and rapeseed oil quality; Wang Weijun, Journal of the Chinese Cereals and Oils Association, 36(3))" studied the effect of rapeseed frying temperature on polyphenol content. The results showed that as the frying temperature increased, the total phenol content in rapeseed oil increased, increasing by 27.4 times at 160°C.

[0005] "Polyphenol yield and antioxidant activity of rapeseed pretreated with steam explosion; Feng Chengfeng, Journal of Hunan Agricultural University, 2023, 49(5): 609-615)" studied the effects of different steam explosion conditions on the polyphenol content of rapeseed oil. The results showed that steam explosion can be used as a heating pretreatment technology for rapeseed in the preparation of rapeseed oil, which can effectively improve the polyphenol yield and antioxidant activity of rapeseed. When the steam pressure was 0.7MPa and the pressure was maintained for 3min, the polyphenol content in rapeseed cake and oil reached the maximum.

[0006] CN102533426A discloses a processing method for improving the flavor and nutritional quality of rapeseed oil, which comprises: (1) conditioning to make the rapeseed moisture content in the range of 9%-20%; (2) preheating to preheat the conditioned rapeseed to make the material temperature reach 100°C-150°C; (3) cold pressing or peeling and cold pressing to obtain cold pressed rapeseed crude oil; (4) degumming to obtain degummed oil; (5) deacidification to obtain cold pressed rapeseed oil. The rapeseed oil obtained by the method has a good and rich flavor and is rich in nutrients.

[0007] In summary, although increasing the frying temperature (above 160°C) can increase the polyphenol content, it has a great impact on the quality of the oil. For example, high temperature causes the flavor oil to have a strong burnt smell, or a high peroxide value, or an increase in the content of harmful substances such as benzopyrene, which reduces the quality of the oil. For this reason, the frying temperature for preparing flavor oil should not exceed 170°C; steam explosion has a good effect on improving polyphenols, but since the water content of the oil is greatly increased after steam explosion, it cannot be directly used for oil pressing. It needs to be dried first, which increases energy consumption costs. In addition, during the steam explosion process, the oil is hydrolyzed into free fatty acids, resulting in the acid value of the obtained oil being too high and the quality being poor; low-temperature cold pressing is used to improve the quality of the oil and cake, but the rapeseed oil obtained by cold pressing has obvious undesirable flavors such as vegetable green.

[0008] In order to solve the above problems, it is therefore urgent to provide a method for increasing the content of polyphenols, sterols and flavor substances in vegetable oils, thereby improving the quality of vegetable oils. Summary of the invention

[0009] The purpose of the present invention is to overcome the problems of low content of polyphenols and flavor substances in vegetable oils and poor quality of vegetable oils in the prior art, and to provide a flavor oil processing technology for improving phenolic nutrients. The vegetable oil prepared by the process method has high content of polyphenols, sterols and flavor substances.

[0010] In order to achieve the above object, the present invention provides a method for preparing a vegetable oil rich in polyphenols and flavor substances, the method comprising the following steps:

[0011] (1) mixing oil seeds with water and performing low temperature treatment at a temperature below 20° C. to obtain wet oil seeds;

[0012] (2) frying and pressing the moistened oil seeds to obtain first crude oil and oil cake;

[0013] (3) mixing the oil cake with water, performing heat treatment, and extracting oil to obtain a second crude oil;

[0014] (4) Mixing the first crude oil and the second crude oil to obtain vegetable oil.

[0015] Through the above technical scheme, the present invention can at least achieve the following beneficial technical effects: the method of the present invention increases the content of polyphenols in the pressed oil, promotes the migration of polyphenols in the pressed cake, and at the same time ensures the content of flavor substances in the oil product. In a preferred embodiment, the polyphenol content in rapeseed oil (mixed oil after blending) is as high as 601 mg / kg, the sterol content is as high as 6598 mg / kg, and the flavor substance content is as high as 489 mg / kg. DETAILED DESCRIPTION

[0016] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0017] The present invention provides a method for preparing a vegetable oil rich in polyphenols and flavor substances, the method comprising the following steps:

[0018] (1) mixing oil seeds with water and performing low temperature treatment at a temperature below 20° C. to obtain wet oil seeds;

[0019] (2) frying and pressing the moistened oil seeds to obtain first crude oil and oil cake;

[0020] (3) mixing the oil cake with water, heat treating, and extracting oil to obtain a second crude oil;

[0021] (4) Mixing the first crude oil and the second crude oil to obtain vegetable oil.

[0022] According to the present invention, there is no particular limitation on oil seeds, and any seed that can be squeezed to extract oil is suitable for the present method, such as rapeseed, linseed, etc. In a specific embodiment provided by the present invention, rapeseed is used as the oil seed to prepare rapeseed oil.

[0023] According to the present invention, rapeseed and rapeseed both refer to the seeds of rapeseed flowers, and the oil prepared is rapeseed oil.

[0024] According to some embodiments of the present invention, in step (1), the amount of water is 15 wt%-100 wt%, preferably 20 wt%-50 wt%, based on the dry weight of the oil seeds.

[0025] According to some embodiments of the present invention, the conditions for the low temperature treatment include: a temperature of 10-20°C, preferably 15-19°C.

[0026] According to the present invention, there is no particular limitation on the time of low temperature treatment, as long as the moisture can fully wet the rapeseed. However, in order to prevent the oil seeds from growing mold and stinking during the low temperature treatment, preferably, the low temperature treatment time is 4-12 hours, more preferably 6-8 hours.

[0027] According to a preferred embodiment of the present invention, oil seeds are mixed with water and left to stand at low temperature, so that the oil seeds can fully absorb water, and the water enters the interior of the cells, further changing the binding sites of polyphenols in the oil seed cells, making the binding of polyphenols to intracellular proteins or cell walls looser, thereby allowing the polyphenols in the cells to migrate to the outside of the cells, promoting the dissolution of polyphenols, and thus significantly increasing the content of polyphenols in vegetable oils.

[0028] According to some embodiments of the present invention, in step (3), the oil cake is mixed with water so that the water content of the oil cake is 35 wt %-65 wt %.

[0029] Preferably, in step (3), the oil cake is mixed with water so that the water content of the oil cake is 40wt%-60wt%.

[0030] According to the present invention, the oil cake is mixed with water so that the water content of the oil cake meets the above-mentioned limiting conditions, which can promote further dissolution of polyphenols in the oil cake.

[0031] According to some embodiments of the present invention, in step (2), the frying and pressing treatment comprises sequentially subjecting the moistened oil seeds to a first stage frying treatment, a second stage frying treatment and a pressing treatment.

[0032] According to some embodiments of the present invention, the temperature of the first stage frying treatment is 80-100°C, and the temperature of the second stage frying treatment is 155°C-165°C.

[0033] According to the present invention, the inventors of the present invention have found that dividing the frying process into two heating stages can weaken the binding force between protein and polyphenols in oil seeds, thereby further promoting the dissolution of polyphenols in oil seeds, while producing the most suitable flavor substances, and the prepared vegetable oil has the best flavor.

[0034] In the present invention, there is no particular limitation on the method of squeezing, and any method that can achieve physical squeezing is acceptable. For example, a screw press can be used for squeezing, and the screw press is purchased from Shibayoufang Co., Ltd., and the instrument model is FL-S2017.

[0035] According to some embodiments of the present invention, in step (3), the heat treatment method is selected from at least one of a wok treatment, an extrusion puffing treatment and a steam explosion treatment.

[0036] Preferably, the conditions of the wok treatment include: temperature of 60-120° C. and time of 15-40 min.

[0037] Preferably, the conditions of the extrusion puffing treatment include: a screw speed of 60-80 rpm, a steam pressure of 0.4-0.4 MPa, and a puffing time of 2-4 s.

[0038] Preferably, the conditions for the steam explosion treatment include: steam pressure of 0.4 MPa-1 MPa, and time of 20-60 s.

[0039] According to some embodiments of the present invention, in step (3), the oil extraction treatment comprises mixing the heat-treated oil cake with oil and performing solid-liquid separation. The solid-liquid separation may be performed by centrifugal separation.

[0040] According to the present invention, there is no particular limitation on the oil used in the oil extraction process, and the oil can be selected according to the type of the prepared vegetable oil. For example, if the prepared vegetable oil is rapeseed oil, rapeseed oil is added to the rapeseed cake; if the prepared vegetable oil is linseed oil, linseed oil is added to the linseed cake. In a specific embodiment provided by the present invention, the oil is rapeseed oil.

[0041] Preferably, the weight ratio of the oil to the heat-treated oil cake is (3-6):1.

[0042] Preferably, the conditions for mixing the heat-treated oil cake with oil (or extracting oil) include: temperature of 60-90° C. and time of 1-3 h.

[0043] According to some embodiments of the present invention, in step (4), the mass ratio of the first crude oil to the second crude oil is 1:(10-20).

[0044] According to some embodiments of the present invention, the method further comprises dehydrating and degumming the vegetable oil so that the water content of the vegetable oil is lower than 0.05 wt % and the phosphorus content is lower than 40 mg / kg.

[0045] According to some embodiments of the present invention, the conditions of the dehydration treatment include: temperature of 60-80°C, preferably 65-75°C; pressure of 0.03-0.08MPa, preferably 0.04-0.06MPa; time of 5-20min, preferably 10-15min;

[0046] Preferably, the degumming treatment comprises heating the vegetable oil to 70-75°C, adding an acid solution to adjust the pH to 6-6.5, and then cooling the oil to 30-40°C.

[0047] More preferably, the acid solution is selected from phosphoric acid solution and / or citric acid solution.

[0048] More preferably, the mass concentration of the acid in the acid solution is 0.1 wt%-0.2 wt%.

[0049] According to a particularly preferred embodiment of the present invention, a method for preparing a vegetable oil rich in polyphenols and flavor substances is provided, the method comprising the following steps:

[0050] (1) spraying tap water (the amount of tap water is 20-50 wt% of the rapeseed weight) on the surface of the oil seeds, and leaving it at 15-19° C. for 6-8 hours to obtain wet rapeseed;

[0051] (2) heating the wet rapeseed to 85-90° C., and then heating to 155-160° C.; pouring the roasted rapeseed into a screw press for pressing to obtain first rapeseed crude oil and pressed cake;

[0052] (3) adding water to the pressed cake so that the water content of the pressed cake is 40-50 wt %, and then heating the pressed cake by frying (raising the temperature of the pressed cake to 70-90° C. for 20-30 min); adding rapeseed oil to the heat-treated pressed cake, and removing solids by centrifugation to obtain a second crude rapeseed oil;

[0053] The mass ratio of rapeseed oil to the heated pressed cake is (4-5):1;

[0054] (4) in a sealed container, mixing the first crude rapeseed oil and the second crude rapeseed oil in a mass ratio of 1:(10-15), heating the mixed crude rapeseed oil to 65-75° C., and heating at 0.04-0.06 MPa for 10-15 min to obtain a dehydrated mixed oil;

[0055] (5) The dehydrated mixed oil is heated to 70-75° C., a phosphoric acid solution with a mass concentration of 0.1-0.2 wt % is added, and the pH value of the mixed oil is adjusted to 6-6.5, and then the mixed oil is cooled to 30-40° C. to crystallize phospholipids, and then filtered to obtain rapeseed oil.

[0056] The present invention will be described in detail below through examples.

[0057] In the following examples and comparative examples, rapeseed refers to rapeseed.

[0058] Unless otherwise specified, materials are commercially available.

[0059] Example 1

[0060] (1) Spraying tap water (the amount of tap water is 20 wt% of the weight of the rapeseed) on the surface of 1000 g of rapeseed, and leaving it to stand at 20° C. for 12 h to obtain wet rapeseed;

[0061] (2) heating the wet rapeseed to 100° C. to reduce the water content of the rapeseed to 10 wt %, and then heating the rapeseed to 165° C.; pouring the roasted rapeseed into a screw press for pressing to obtain a first crude rapeseed oil and a pressed cake;

[0062] (3) adding water to the pressed cake so that the water content of the pressed cake is 65 wt %, and then heating the pressed cake by frying (raising the temperature of the pressed cake to 120° C. for 40 min); adding rapeseed oil to the pressed cake after heat treatment, stirring at 80° C. for 3 h, and removing solids by centrifugation to obtain a second rapeseed crude oil;

[0063] Among them, the mass ratio of rapeseed oil to heat-treated pressed cake is 6:1;

[0064] (4) in a sealed container, mixing the first crude rapeseed oil and the second crude rapeseed oil in a mass ratio of 1:20, heating the mixed crude rapeseed oil to 80° C., and heating at 0.08 MPa for 20 min to obtain a dehydrated mixed oil;

[0065] Wherein, the water content of the mixed rapeseed oil is 0.2wt%;

[0066] (5) The dehydrated mixed oil is heated to 75° C., a phosphoric acid solution with a mass concentration of 0.2 wt % is added, and the pH value of the mixed oil is adjusted to 6.5, and then the mixed oil is cooled to 40° C. to crystallize phospholipids, and then filtered to obtain rapeseed oil.

[0067] Example 2

[0068] (1) Spraying tap water (the amount of tap water is 15 wt% of the weight of the rapeseed) on the surface of 1000 g of rapeseed, and leaving it to stand at 10° C. for 4 h to obtain wet rapeseed;

[0069] (2) heating the wet rapeseed to 80° C. to reduce the water content of the rapeseed to 5 wt %, and then heating it to 155° C.; pouring the roasted rapeseed into a screw press for pressing to obtain a first crude rapeseed oil and a pressed cake;

[0070] (3) adding water to the pressed cake so that the water content of the pressed cake is 35 wt %, and then heating the pressed cake by frying (raising the temperature of the pressed cake to 60° C. for 15 min); adding rapeseed oil to the pressed cake after heat treatment, stirring at 60° C. for 1 h, and removing solids by centrifugation to obtain a second crude rapeseed oil;

[0071] Among them, the mass ratio of rapeseed oil to heat-treated pressed cake is 3:1;

[0072] (4) in a sealed container, mixing the first crude rapeseed oil and the second crude rapeseed oil in a mass ratio of 1:10, heating the mixed crude rapeseed oil to 60° C., and heating at 0.03 MPa for 5 min to obtain a dehydrated mixed oil;

[0073] Wherein, the water content of the mixed rapeseed oil is 0.8wt%;

[0074] (5) The dehydrated mixed oil is heated to 70° C., a phosphoric acid solution with a mass concentration of 0.1 wt % is added, and the pH value of the mixed oil is adjusted to 6. Then, the mixed oil is cooled to 30° C., phospholipids are crystallized and filtered to obtain rapeseed oil.

[0075] Example 3

[0076] (1) Spraying tap water (the amount of tap water is 40 wt% of the weight of the rapeseed) on the surface of 1000 g of rapeseed, and leaving it to stand at 15° C. for 8 h to obtain wet rapeseed;

[0077] (2) heating the wet rapeseed to 90° C. to reduce the water content of the rapeseed to 8 wt %, and then heating it to 160° C.; pouring the roasted rapeseed into a screw press for pressing to obtain a first crude rapeseed oil and a pressed cake;

[0078] (3) adding water to the pressed cake so that the water content of the pressed cake is 50 wt %, and then heating the pressed cake by frying (raising the temperature of the pressed cake to 90° C. for 30 min); adding rapeseed oil to the heat-treated pressed cake, stirring at 60° C. for 2 h, and removing solids by centrifugation to obtain a second rapeseed crude oil;

[0079] Among them, the mass ratio of rapeseed oil to heat-treated pressed cake is 5:1;

[0080] (4) in a sealed container, mixing the first crude rapeseed oil and the second crude rapeseed oil in a mass ratio of 1:15, heating the mixed crude rapeseed oil to 70° C., and heating at 0.05 MPa for 12 min to obtain a dehydrated mixed oil;

[0081] Wherein, the water content of the mixed rapeseed oil is 0.5wt%;

[0082] (5) The dehydrated mixed oil is heated to 75° C., a phosphoric acid solution with a mass concentration of 0.2 wt % is added, and the pH value of the mixed oil is adjusted to 6.3, and then the mixed oil is cooled to 35° C. to crystallize phospholipids, and then filtered to obtain rapeseed oil.

[0083] Example 4

[0084] The method of Example 3 is followed, except that in step (1), the low temperature treatment time is 0.5 h to obtain rapeseed oil.

[0085] Example 5

[0086] The method of Example 3 is different in that, in step (2), the wet rapeseed is not subjected to the first stage frying treatment, but is directly heated to 160° C. and then pressed to obtain rapeseed oil.

[0087] Example 6

[0088] The method of Example 3 is followed, except that in step (3), 70 g of water is added to the pressed cake so that the water content of the pressed cake is 10 wt %, to obtain rapeseed oil.

[0089] Example 7

[0090] The method of Example 3 is different in that, in step (4), centrifugal dehydration (rotation speed of 4000 rpm, time of 10 min) is used to obtain rapeseed oil.

[0091] Example 8

[0092] The method of Example 3 is used, except that in step (5), the degumming treatment adopts water degumming (the method of water degumming is to add salt water with a concentration of 10wt% of the oil weight to the dehydrated mixed oil) to obtain rapeseed oil.

[0093] Comparative Example 1

[0094] The method of Example 3 is different in that, in step (1), tap water of the same mass is sprayed on the surface of rapeseed, the wetted rapeseed is allowed to stand at room temperature (25° C.), and then fried and pressed to obtain rapeseed oil;

[0095] According to the method of comparative example 1, the wet rapeseed produces miscellaneous bacteria during the standing process at room temperature (25° C.), causing the rapeseed to deteriorate (become sour and smelly), and the obtained rapeseed oil also deteriorates (becomes sour and smelly), losing its commercial value.

[0096] Comparative Example 2

[0097] The method of Example 3 is different in that, in step (1), the temperature of low temperature treatment is 40° C. to obtain rapeseed oil;

[0098] According to the method of comparative example 2, the wet rapeseed produces miscellaneous bacteria during the high temperature (40° C.) standing process, causing the rapeseed to deteriorate (become sour and smelly), and the obtained rapeseed oil also deteriorates (becomes sour and smelly), losing its commercial value.

[0099] Comparative Example 3

[0100] The method of Example 3 is followed, except that in step (1), tap water is not sprayed on the surface of the rapeseed, and the rapeseed is directly left to stand at 15° C. for 8 h to obtain rapeseed oil.

[0101] Comparative Example 4

[0102] The rapeseed oil is prepared by a traditional small-scale pressing process, the method comprising the following steps:

[0103] 1000g of rapeseed is put into a drum seed roasting pot preheated to 170℃. When the temperature of the rapeseed surface at the discharge port is measured by an infrared temperature measuring gun and rises to 160±5℃, reverse rotation is performed for unloading. The discharged rapeseed is directly put into a single-screw press for pressing. The pressing conditions of the single-screw press are a screw speed of 150r / min and a feeding rate of 300g / min.

[0104] Test Example 1

[0105] The water content, phosphorus content, flavor substance content, polyphenol content and flavor sensory intensity of the rapeseed oil prepared by the above embodiment and comparative example methods were measured respectively. The results are shown in Table 2.

[0106] The moisture content of rapeseed oil was determined using the method of “GB 5009.236-2016 National Food Safety Standard - Determination of Moisture and Volatile Matter in Animal and Plant Fats and Oils - Method 2”.

[0107] The phosphorus content of rapeseed oil was determined using the method of "GB / T 5537-2008 Inspection of Cereals and Oils - Determination of Phospholipid Content".

[0108] The flavor substances in rapeseed oil refer to the sum of 2,5-dimethylpyrazine, 2,5-dimethyl-3-ethylpyrazine, 2-methyl-3-heptanone, benzaldehyde and 2-pentylfuran. The content of flavor substances was determined by gas chromatography-mass spectrometry. The specific determination method includes: adding 5.00g sample (mixed rapeseed oil) and 3μL of 2-methyl-3-heptanone solution (internal standard, 816mg / L octyl decanoate glyceride) into a 20mL headspace bottle. The headspace bottle was placed in a 60℃ heating tank for equilibration for 20min, and the activated extraction head was inserted into the headspace bottle to adsorb volatile substances for 30min, and then inserted into the GC injection port for thermal analysis for 5min. The injection port temperature was 250℃.

[0109] GC conditions: DB-Wax polar column (30m×0.25mm, 0.25μm); carrier gas is high-purity helium (purity>99.99%); flow rate is 1.2mL / min; non-divided mode is adopted; heating program: column temperature starts at 45℃, increases to 180℃ at a rate of 4℃ / min, maintains for 2min, then increases to 230℃ at 10℃ / min, maintains for 6min.

[0110] MS conditions: transfer line temperature 230 °C, electron energy 70 eV, electron ionization source temperature 250 °C, quadrupole temperature 150 °C, mass scan range 40-500 m / z, full scan mode.

[0111] All indexes were measured three times. By searching the NIST14 spectral library, compounds with positive and negative matching greater than 800 (maximum value 1000) were selected, and qualitative analysis was performed in combination with the retention index (RI). The relative content of flavor substances was calculated according to formula (I).

[0112] C j =C i *A j / A i (I)

[0113] In formula (I): C j is the mass concentration of flavor substances, mg / kg.

[0114] C i is the mass concentration of the internal standard, mg / mL.

[0115] A j is the peak area of ​​flavor substances.

[0116] A i is the peak area of ​​the internal standard.

[0117] The polyphenol content of rapeseed oil was determined using the LS / T 6119-2017 Grain and Oil Inspection-Determination of Polyphenols in Vegetable Oils-Spectrophotometric Method.

[0118] The method for determining the flavor sensory intensity score is as follows: using rapeseed oil prepared by traditional small-scale pressing technology (Comparative Example 4) as a blank control, providing the rapeseed oils in other embodiments and comparative examples to 10 tasters (5 males and 5 females, aged 20-30 years old, healthy, no smoking or spicy food two hours before tasting, no disease), and scoring the mixed rapeseed oil according to the proposed scoring criteria after training. The flavor sensory intensity is represented by the average value of the scores of the 10 tasters, and the scoring criteria are shown in Table 1 below.

[0119] Table 1 Rating criteria for flavor sensory intensity of rapeseed oil

[0120] standard Score (points) Blank control group intensity 5 Slightly thick 5＜X≤6 Thick 6＜X≤8 Espresso 8＜X≤10 Slightly light 3≤X＜5 Lighter 1≤X＜3 Extra light 0≤X＜1

[0121] Table 2

[0122]

[0123] The method of the present invention increases the content of polyphenols in the pressed oil and promotes the migration of polyphenols in the pressed cake, while ensuring the content of sterols and flavor substances in the oil product. In a preferred embodiment, the polyphenol content in rapeseed oil (mixed oil after blending) is as high as 601 mg / kg, the sterol content is as high as 6598 mg / kg, and the flavor substance content is as high as 489 mg / kg.

[0124] By comparing Example 3 with Examples 4-8, it can be seen that the use of the preferred preparation method can further increase the content of polyphenols, sterols and flavor substances in rapeseed oil (mixed oil after blending).

[0125] In Comparative Examples 1-2, rapeseed and water were mixed and then allowed to stand at 25°C (normal temperature) and 40°C (high temperature), respectively, and the rapeseed and rapeseed oil (the blended mixed oil) deteriorated, became smelly and sour, and had no commercial value; in Comparative Example 3, tap water was not sprayed on the surface of the rapeseed, and the rapeseed was directly allowed to stand at low temperature, resulting in a decrease in the content of polyphenols, sterols and flavor substances in the rapeseed oil (the blended mixed oil); in Comparative Example 4, rapeseed oil was prepared by pressing using traditional technology, and the content of polyphenols, sterols and flavor substances in the rapeseed oil was reduced.

[0126] In summary, the method of the embodiment of the present invention can increase the content of polyphenols, sterols and flavor substances in vegetable oil and improve the quality of vegetable oil.

[0127] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for preparing a vegetable oil rich in polyphenols and flavor substances, characterized in that: The method comprises the following steps: (1) mixing oil seeds with water and performing low temperature treatment at a temperature below 20° C. to obtain wet oil seeds; (2) frying and pressing the moistened oil seeds to obtain first crude oil and oil cake; (3) mixing the oil cake with water, performing heat treatment, and extracting oil to obtain a second crude oil; (4) Mixing the first crude oil and the second crude oil to obtain vegetable oil.

2. The method according to claim 1, wherein: In step (1), the amount of water is 15wt%-100wt% of the weight of the oil seeds, preferably 20wt%-50wt% based on the dry weight of the oil seeds; And / or, the conditions of the low temperature treatment include: temperature of 10-20°C, preferably 15-19°C, time of 4-12h, preferably 6-8h; And / or, in step (3), the oil cake is mixed with water so that the water content of the oil cake is 35wt%-65wt%.

3. The method according to claim 1 or 2, wherein: In step (2), the frying and pressing treatment comprises sequentially subjecting the moistened oil seeds to a first stage frying treatment, a second stage frying treatment and a pressing treatment.

4. The method according to claim 3, wherein: The temperature of the first stage frying treatment is 80-100°C, and the temperature of the second stage frying treatment is 155°C-165°C.

5. The method according to any one of claims 1 to 4, wherein: In step (3), the oil cake is mixed with water so that the water content of the oil cake is 40wt%-60wt%.

6. The method according to any one of claims 1 to 5, wherein: In step (3), the heat treatment method is selected from at least one of a wok treatment, an extrusion puffing treatment and a steam explosion treatment; Preferably, the conditions of the wok treatment include: temperature of 60-120°C, time of 15-40min; Preferably, the conditions of the extrusion puffing treatment include: screw speed of 60-80 rpm, steam pressure of 0.2-0.4 MPa, and puffing time of 2-4 s; Preferably, the conditions for the steam explosion treatment include: steam pressure of 0.4 MPa-1 MPa, and time of 20-60 s.

7. The method according to any one of claims 1 to 6, wherein: In step (3), the oil extraction treatment method includes mixing the heat-treated oil cake with the oil and separating the solid and liquid; Preferably, the weight ratio of the oil to the heat-treated oil cake is (3-6):1; Preferably, the conditions for mixing the heat-treated oil cake with the oil include: a temperature of 60-90° C. and a time of 1-3 h.

8. The method according to any one of claims 1 to 7, wherein: In step (4), the mass ratio of the first crude oil to the second crude oil is 1:(10-20).

9. The method according to any one of claims 1 to 8, wherein: The method further comprises sequentially dehydrating and degumming the vegetable oil, so that the water content of the vegetable oil is lower than 0.05wt% and the phosphorus content is lower than 40mg / kg.

10. The method according to claim 9, wherein: The dehydration treatment conditions include: temperature of 60-80°C, preferably 65-75°C; pressure of 0.03-0.08MPa, preferably 0.04-0.06MPa; time of 5-20min, preferably 10-15min; Preferably, the degumming treatment comprises heating the vegetable oil to 70-75°C, adding an acid solution to adjust the pH to 6-6.5, and then cooling to 30-40°C; More preferably, the acid solution is selected from phosphoric acid solution and / or citric acid solution; More preferably, the mass concentration of the acid in the acid solution is 0.1 wt%-0.2 wt%.

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