Peanut oil with low oil smoke, sweet and fragrant flavor and rich resveratrol and preparation method thereof

Abstract

The invention provides peanut oil with low oil smoke, sweet and fragrant flavor and rich resveratrol and a preparation method thereof. The preparation method of the peanut oil comprises the steps of steam explosion treatment, enzymolysis, heat treatment and oil cleaning. Wherein the steam pressure of the steam explosion treatment ranges from 0.7 MPa to 2.0 MPa, and the pressure maintaining time ranges from 30 seconds to 150 seconds; when the steam pressure is less than or equal to 0.8 MPa, the pressure holding time is 100-150 seconds; wherein the step of cleaning the oil comprises the following steps: adding peanut shell powder accounting for 5-10% of the weight of the oil into the oil obtained by heat treatment, and stirring at 40-100 DEG C for 0.5-2 hours. The peanut oil prepared by the method disclosed by the invention is rich in sweet flavor and high in smoke point, and contains high-content resveratrol.

Description

Technical Field

[0001] The invention relates to peanut oil with low oil smoke, sweet and fragrant flavor and rich in resveratrol and a preparation method thereof. Background Art

[0002] With the improvement of people's living standards, the application of edible oil in cooking is becoming more and more diversified. In order to cater to the preferences of consumers, relevant processing enterprises have developed edible oils with different flavors, such as cooking sesame oil, fragrant sunflower oil, fragrant corn oil, fragrant rapeseed oil, etc. And with the development of various dishes, catering snacks, edible oils with different flavors and different application functions and scenarios have become an inevitable trend in the development of the oil processing industry, such as barbecue oil, rice cooking oil, edible oil for pouring, stuffing and steaming fish, etc. As a traditional flavor oil in China, peanut oil will surely drive the development of the entire peanut industry if it can meet the flavor demand and have certain functional claims. Traditional peanut oil is dominated by roasted peanuts and is deeply loved by consumers. Cold-pressed oil with raw peanut oil flavor also satisfies some consumers because of its distinctive characteristics. Peanut oil characterized by sweet flavor is relatively rare in life, and there is a problem of relatively light sweet flavor and easy loss in the industrial production process. Therefore, retaining more sweet flavor in the production process of fragrant peanut oil has become the research focus of current scientific workers.

[0003] Due to the special cooking method of Chinese cuisine, a large amount of oil fume is generated during the cooking process. No matter what kind of dish is cooked, the process is basically heating the pan, adding oil, heating oil, adding ingredients, stir-frying, seasoning and serving. The three stages that produce the most oil fume are adding ingredients, stir-frying and serving. In addition, YIN et al. (Li, YIN et al. XRCC1 polymorphisms, cooking oil fume and lung cancer in Chinese women nonsmokers [J], Lung Cancer,, 2008, 62 (2): 145-151.) showed through cross-sectional and case-control studies that cooking oil fume has certain harm to the environment and human body, and has an impact on lung function. Among them, many domestic and foreign studies on oil fume have shown that oil fume VOCs contain a variety of toxic chemical components, which are harmful to the body's immunity, heredity, etc. Oil smoke can be judged by the smoke point. Generally speaking, the smoke point refers to the temperature of the sample's thermal decomposition products or continuous solid particles visible to the naked eye when the oil is heated. If the smoke point of cooking oil is low, it is easy to produce oil smoke. Therefore, the smoke point of cooking oil should be increased as much as possible to reduce the generation of oil smoke. Current research shows that the generation of oil smoke can be measured by measuring the smoke point or the concentration of solid particles in the oil smoke.

[0004] Generally speaking, there are many factors that affect the amount of oil smoke and smoke point, including the fatty acid composition of the oil, mainly the degree of unsaturation of fatty acids; the free fatty acids in the oil, mainly the content and degree of unsaturation of free fatty acids; the content of phospholipids, mainly the phospholipids remaining after refining and degumming; some secondary oxidation products in the oil, as well as water, impurities, antioxidants and mono- and di-glycerides in the oil will also affect the oil smoke situation. Wang Xingguo, Liu Yuanfa et al. (Wang Xingguo, Zhou Shengli. Effect of non-triglyceride components on the smoke point of oil products [J]. China Oils and Fats, 1999, 24(1): 38-39; Han Shanshan, Liu Yuanfa. Effect of phospholipids and free fatty acids on the smoke point and oxidative stability of oils and fats [J]. China Oils and Fats, 2013, 39(4): 23-26.) found that phospholipids and free fatty acids can significantly reduce the smoke point of vegetable oils, and the smoke point is negatively correlated with the content of free fatty acids.

[0005] Regarding the peanut oil for cooking, those skilled in the art have made the following attempts:

[0006] CN200510042451.2 discloses a method for anhydrous dephospholipidation of squeezed peanut oil with preserved aroma, which is mainly prepared by separating phospholipids in the squeezed oil and filtering at 14-22°C. The method mainly utilizes the characteristics of low-temperature flocculation and precipitation of phospholipids for separation, but other cooking application characteristics and aroma are not actually taken into consideration.

[0007] CN01129669.0 discloses a cooking flavor oil and a preparation method thereof, which adopts the form of a fat composition, mainly including edible oil, amino acid, sugar, organic acid, etc. of a certain mass range, and is prepared by thermal reaction heating, and then combined with a general heating method (hot water, steam or microwave) to prepare dishes with cooking flavor. Although the preparation method is simple, it does not take into account the stability of the fat, the traditional Chinese cooking habits, and the problem of easy splashing during actual use.

[0008] CN201710699251.7 discloses a method for preparing peanut oil rich in sweet aroma, including material selection, raw material pretreatment, crushing and embryo pressing, embryo steaming and frying, and oil pressing. The main feature is that weak alkaline water at a certain temperature is added during the embryo steaming process to promote the generation of sweet and fragrant substances. However, the proportion of weak alkaline water added is relatively high, the addition method and subsequent treatment are relatively cumbersome, and the evaporation energy consumption is also relatively large.

[0009] CN201611161761.0 discloses a method of low-temperature pressing, crude oil filtration, ceramic membrane degumming, clay decolorization and modified wheat husk adsorption. This method avoids the problems of protein denaturation and poor oil purity after hot pressing at room temperature, but the operation process is cumbersome, the industrialization cost of ceramic membrane degumming is high, and the resulting product has a lighter flavor, which has certain disadvantages in cooking applications.

[0010] In summary, the existing technology has not been able to take into account the sweet and fragrant flavor of peanuts while reducing the generation of oil smoke through moderate processing, and ultimately obtain the application function of taking into account the flavor of peanut oil and making the product have less oil smoke.

[0011] Therefore, there is an urgent need in the art to provide a product that can be prepared with a strong sweet flavor, less smoke and is environmentally friendly. Summary of the invention

[0012] The first aspect of the present invention provides a method for preparing peanut oil, which comprises the steps of steam explosion treatment, enzymatic hydrolysis, heat treatment and oil cleaning treatment.

[0013] In one or more embodiments, the steam pressure of the steam explosion treatment is 0.7 MPa to 2.0 MPa, and the holding time is 30 to 150 seconds; and when the steam pressure is ≤0.8 MPa, the holding time is 100 to 150 seconds, and when the steam pressure is ≥1.8 MPa, the holding time is ≤50s.

[0014] In one or more embodiments, the clear oil comprises: adding peanut shell powder accounting for 5-10% of the weight of the oil to the oil obtained by heat treatment, and stirring at 40-100° C. for 0.5-2 hours.

[0015] In one or more embodiments, the peanuts are crushed after steam explosion, and the resulting peanut flour is mixed with water and subjected to enzymatic treatment.

[0016] In one or more embodiments, the enzyme used for enzymolysis is selected from: one or more of neutral protease, alkaline protease, flavor protease, endoprotease, exoprotease, papain, trypsin, high temperature amylase, medium temperature amylase, fungal amylase, bacterial amylase, cellulase, hemicellulase, glucanase, complex saccharifying enzyme, pectinase, pullulanase, polygalacturonase and sucrose invertase; more preferably, the enzyme used for enzymolysis is selected from one or more of alkaline protease, flavor protease, medium temperature amylase, complex saccharifying enzyme and pectinase.

[0017] In one or more embodiments, the total amount of enzymes used for enzymatic hydrolysis is 1-6% by weight of the peanuts, such as 2-6%.

[0018] In one or more embodiments, the enzymes used for enzymatic hydrolysis include alkaline protease, flavor protease, mesophilic amylase, complex saccharifying enzyme and pectinase; based on the weight of peanuts, the amount of alkaline protease is 0.1-2%, such as 0.1-1.0%; the amount of flavor protease is 0.1-3%, such as 0.1-1.0%; the amount of mesophilic amylase is 0.1-3%, such as 0.1-1.0%; the amount of complex saccharifying enzyme is 0.1-3%, such as 0.5-2.0%; the amount of pectinase is 0.1-3%, such as 0.5-2.0%.

[0019] In one or more embodiments, the enzymatic hydrolysis is carried out at 30-70° C. and pH 5-9, and the reaction time is 3-15 hours.

[0020] In one or more embodiments, in the enzymatic hydrolysis reaction system, the mass ratio of peanut powder to water is 1:1 to 1:10, preferably 1:2 to 1:8.

[0021] In one or more embodiments, alkaline protease is first used for enzymolysis, and then flavor protease, medium-temperature amylase, complex saccharifying enzyme and pectinase are added for enzymolysis.

[0022] In one or more embodiments, when alkaline protease is used for enzymolysis, the amount used is 0.1-1.0% of the mass of peanuts, and the pH of the enzymolysis reaction system is 8.0-9.0.

[0023] In one or more embodiments, when flavor protease, medium-temperature amylase, complex saccharifying enzyme and pectinase are used for enzymatic hydrolysis, the pH of the reaction system is set to 5.5-6.5, wherein, based on the mass of peanuts, the amount of flavor protease is 0.1-1.0%, the amount of medium-temperature amylase is 0.1-1.0%, the amount of complex saccharifying enzyme is 0.5-2.0%, and the amount of pectinase is 0.5-2.0%.

[0024] In one or more embodiments, during the enzymatic hydrolysis process, the pH value of the reaction system is maintained at ±0.2 of the initial pH value of the reaction, and the pH value is within the range of 8.0 to 9.0 or 5.5 to 6.5.

[0025] In one or more embodiments, after the enzymatic hydrolysis is completed, the pH of the enzymatic hydrolyzate is adjusted to a range of 7.5 to 8.5, preferably 7.8±0.2, and then dried to obtain enzymatic hydrolyzate powder; preferably, the drying is selected from freeze drying, spray drying, rolling scraper drying and vacuum drying.

[0026] In one or more embodiments, the heat treatment comprises: mixing the enzymatic hydrolysis product with peanut oil, and then subjecting the resulting mixture to heat treatment.

[0027] In one or more embodiments, the mass ratio of the product to peanut oil is 1:2-10, such as 1:4-10 or 1:5-8.

[0028] In one or more embodiments, the heat treatment temperature is 160-180°C, and the heat treatment time is 0.5-1 hour; during the heat treatment, the pressure in the reaction vessel does not exceed 0.7 MPa, preferably 0.2-0.7 MPa, and more preferably 0.3-0.6 MPa.

[0029] In one or more embodiments, after the heat treatment is completed, the oil is separated and the oil is subjected to the oil clearing treatment.

[0030] In one or more embodiments, the peanut shell powder is prepared as follows: clean peanut shells are taken, dried to a moisture content of ≤3.0wt%, and then crushed to less than 20 mesh, preferably 40-80 mesh, to obtain the peanut shell powder; preferably, the drying temperature is 40-60°C, and the drying time is 10-24h.

[0031] The present invention also provides peanut oil prepared by the method described in any embodiment of the present invention.

[0032] In one or more embodiments, the smoke point of the peanut oil is ≥168°C, preferably ≥170°C, more preferably ≥173°C; and the resveratrol is ≥150 μg / kg, preferably ≥160 μg / kg, more preferably ≥170 μg / kg.

[0033] The present invention also provides a blended oil or a food containing the blended oil, wherein the blended oil contains the peanut oil described in the present invention; preferably, the food is selected from seasoning sauces, pre-prepared dishes, convenience foods, snack foods, meat and its products, cold foods, beverages and cakes.

[0034] The present invention also provides an application selected from the following:

[0035] (1) Application of steam explosion treatment in improving the sweet flavor of peanut oil, or in preparing peanut oil with enhanced sweet flavor; preferably, the pressure of the steam explosion treatment is 0.7-2.0 MPa, and the time is 30-150 s; more preferably, the pressure of the steam explosion treatment is 1.0-2.0 MPa, and the time is 50-150 s, such as 50-100 s;

[0036] (2) Application of steam explosion treatment and oil clearing treatment in improving the sweet flavor of peanut oil, improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil; preferably, the steam explosion treatment and oil clearing treatment are as described in any embodiment of the present invention;

[0037] (3) Application of steam explosion equipment and peanut shell powder in improving the sweet flavor of peanut oil, improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil; preferably, the steam explosion equipment comprises a gas explosion tank, and the peanut shell powder is prepared by the method described in any embodiment of the present invention;

[0038] (4) Application of peanut shell powder in improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil; preferably, the peanut shell powder is prepared by the method described in any embodiment of the present invention.

[0039] The present invention also provides a method for preparing peanut oil with a strong sweet flavor or improving the sweet flavor of peanut oil, characterized in that the method comprises the steps of steam explosion treatment of peanut raw materials and then enzymatic hydrolysis and heat treatment; wherein the steam pressure of the steam explosion treatment is 0.7MPa-2.0MPa, and the pressure holding time is 30-150 seconds; wherein, when the steam pressure is ≤0.8MPa, the pressure holding time is 100-150 seconds, and when the steam pressure is ≥1.8MPa, the pressure holding time is ≤50s; preferably, the enzymatic hydrolysis treatment is as described in any embodiment of the present invention; preferably, the heat treatment is as described in any embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0041] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0042] In this article, all features such as quantity, content and concentration defined in the form of numerical ranges or percentage ranges are only for brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions). In this article, unless otherwise specified, ratios are weight ratios and percentages are weight percentages.

[0043] In this document, in order to make the description concise, not all possible combinations of the technical features in each embodiment or example are described. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each embodiment or example can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0044] The inventors found that in the preparation process of peanut oil, the peanut raw materials are first subjected to steam explosion treatment before enzymatic hydrolysis, and the peanut oil obtained by heat treatment (such as Maillard reaction) is subjected to oil purification treatment. The obtained peanut oil has a strong sweet aroma, a high smoke point, and contains a high content of resveratrol.

[0045] Therefore, the present application provides a method for preparing peanut oil, which comprises the steps of steam explosion treatment, enzymatic hydrolysis, heat treatment and oil cleaning.

[0046] Herein, the peanuts used to prepare peanut oil may be various peanuts commonly used in the art for preparing peanut oil. The peanuts may be subjected to conventional treatment to remove impurities to obtain the peanut raw material for preparing peanut oil. For example, the raw peanuts may be treated with a vibrating screen to remove large impurities in the peanuts, the stones in the raw material may be removed by gravity de-stoning, and the metal substances in the raw material may be removed by a magnetic separator and a metal detector.

[0047] In this article, steam explosion, also known as steam explosion, is a technology that uses the steam ejection principle to realize the explosion process for pretreatment of biomass. Its technical essence is: the steam molecules that penetrate into the plant tissue are released instantly, so that the internal energy of the steam is converted into mechanical energy and acts on the cell layers of the biomass tissue, thereby using less energy to decompose the raw materials according to the purpose.

[0048] Herein, the steam pressure of the steam explosion treatment may be 0.7MPa to 2.0MPa, and the holding time may be 30 to 150 seconds. For example, the peanut raw material may be added to a suitable container, such as an explosion tank, and then saturated steam may be introduced to make the pressure in the container 0.7MPa to 2.0MPa, and the pressure may be maintained in the container for 30 to 150 seconds, thereby completing the steam explosion treatment. It should be understood that when the pressure is low, the holding time may be extended accordingly; and when the pressure is high, the holding time may be appropriately shortened. For example, when the steam pressure is ≤0.8MPa, the holding time may be more than 100s, such as 100 to 150s; when the steam pressure is between 1.8 and 2.0MPa, the holding time may be ≤100s, such as 30 to 100s or 30 to 50s. In some embodiments, the pressure of the steam explosion treatment is 0.7-1.5 MPa, and the holding time is 50-150 s; in some embodiments, the pressure of the steam explosion treatment is 1.8-2.0 MPa, and the holding time is 30-50 s. The present invention can be implemented using steam explosion equipment well known in the art, and these equipment can be commercially available products.

[0049] After the steam explosion process is completed, the peanuts are taken out, crushed, mixed with water, and then enzymes are added for enzymatic hydrolysis.

[0050] Herein, enzymolysis methods known in the art can be used to enzymolyze peanuts. Enzymes suitable for the present invention are enzymes commonly used in the preparation of strong-flavored oils and fats such as peanut oil in this area, including but not limited to one or more of neutral protease, alkaline protease, flavor protease, endoproteinase, exoproteinase, papain, trypsin, high-temperature amylase, medium-temperature amylase, fungal amylase, bacterial amylase, cellulase, hemicellulase, glucanase, composite saccharifying enzyme, pectinase, pullulanase, polygalacturonase and invertase etc. These enzymes are well known to those skilled in the art, can be prepared voluntarily by the disclosed method, or can be obtained from commercially available sources. For example, the required enzyme can be purchased from Novozymes.

[0051] The peanuts can be enzymatically hydrolyzed using a combination of one or more enzymes, for example, one or more enzymes selected from alkaline protease, flavor protease, moderate temperature amylase, complex saccharifying enzyme and pectinase can be used.

[0052] Generally, the total amount of enzymes used can be 1-6% of the weight of the oil-bearing crop seeds, such as 2-6%. When used, the amount of various enzymes used is the conventional amount used when enzymolyzing oil-bearing crop seeds such as peanuts. For example, based on the weight of oil-bearing crop seeds such as peanuts, the amount of alkaline protease used can be 0.1-2%, such as 0.1-1.0%; the amount of flavor protease used can be 0.1-3%, such as 0.1-1.0%; the amount of medium-temperature amylase used can be 0.1-3%, such as 0.1-1.0%; the amount of complex saccharifying enzyme used can be 0.1-3%, such as 0.5-2.0%; the amount of pectinase used can be 0.1-3%, such as 0.5-2.0%. It should be understood that the amount of enzymes used can be adjusted according to the actual reaction conditions.

[0053] The temperature, pH, reaction time and other parameters of the enzymolysis can be selected according to the most suitable reaction conditions of various enzymes. For example, enzymolysis is usually carried out under the conditions of 30-70°C and pH 5-9, and the reaction time is usually 3-15 hours. The specific reaction conditions may vary according to the enzyme. In the present invention, the pH value of the reaction system can be adjusted by conventional methods, such as using a buffer solution, or using an acid, a base, a salt, etc. It can be understood that the use of the buffer solution or the acid, the base, the salt should not affect the activity of the enzyme, or cause obvious physical or chemical changes in the components during the enzymolysis process. When multiple enzymes are used for enzymolysis, different enzymes can be added in sequence. After the enzymolysis reaction of the first one or more enzymes is completed, the reaction conditions such as the pH of the reaction system are adjusted to the optimal reaction conditions of the subsequent one or more enzymes, and then the subsequent one or more enzymes are added for enzymolysis reaction. When the optimal reaction conditions of several enzymes are similar and they do not interfere with each other when reacting together, several enzymes can be added at the same time for enzymolysis.

[0054] In some embodiments of the present invention, alkaline protease is first used for enzymolysis, and flavor protease, medium-temperature amylase, compound saccharifying enzyme and pectinase are added for enzymolysis after the enzymolysis is completed. In some embodiments, when alkaline protease is used for enzymolysis, its dosage can be 0.1-1.0% of the weight of peanuts, and the pH of the enzymolysis reaction system can be adjusted to 8.0-9.0; when flavor protease, medium-temperature amylase, compound saccharifying enzyme and pectinase are used for enzymolysis, the pH of the reaction system can be adjusted to 5.5-6.5, wherein, based on the weight of peanuts, the dosage of flavor protease can be 0.1-1.0%, the dosage of medium-temperature amylase can be 0.1-1.0%, the dosage of compound saccharifying enzyme can be 0.5-2.0%, and the dosage of pectinase can be 0.5-2.0%. Preferably, during the enzymolysis process, the pH value of the reaction system is maintained at a relatively fixed pH value.

[0055] During enzymolysis, the mass ratio of peanut powder to water in the enzymolysis reaction system can be 1:1 to 1:10, preferably 1:2 to 1:8. The water in the enzymolysis reaction system can come from pure water, or from a buffer solution, or a solution containing an acid, a base and / or a salt. When the pH value of the reaction system is not within the optimal working pH range of the enzyme used, conventional technical means in the art can be used, such as adding an appropriate amount of acid or base, to adjust the pH value of the reaction system to the optimal working pH range of the enzyme.

[0056] After the enzymolysis is completed, the pH of the enzymolysis solution can be adjusted to a range of 7.5 to 8.5, preferably 7.8±0.2, and then dried to obtain enzymolysis powder. The drying can be freeze drying, spray drying, rolling scraper drying and / or vacuum drying.

[0057] The enzymatic hydrolysis powder can be mixed with peanut oil, and the mixing mass ratio can be 1:2-10, for example, 1:4-10 or 1:5-8, and then the resulting mixture is subjected to heat treatment. Herein, the temperature of the heat treatment can be 160-180°C, and the heat treatment time can be 0.5-1 hour. During the heat treatment process, the pressure in the reaction vessel is preferably not more than 0.7MPa, for example, it can be 0.2-0.7MPa, preferably 0.3-0.6MPa. Since heat treatment increases the pressure in the reaction vessel (such as a reactor), the reaction vessel can be evacuated after the material is added to the reaction vessel before heat treatment. The vacuum degree after vacuuming can be controlled according to the actual reaction conditions, as long as the pressure in the reaction vessel during the heat treatment reaction does not exceed 0.7MPa, for example, within the range of 0.2-0.7MPa. In some embodiments, after vacuuming, the vacuum degree in the reaction vessel is -0.1MPa or less. Maillard reaction occurs under heat treatment conditions to obtain rich-flavored peanut oil.

[0058] The peanut oil suitable for the heat treatment of the present invention may be various refined peanut oils well known in the art.

[0059] After the heat treatment is completed, the reaction product can be cooled and separated to obtain the oil and fat part. The heat-treated product (crude oil and fat product) can be cooled and separated by conventional methods in the art. Generally, cooling and separation includes: after the reaction liquid is cooled to room temperature, separating and removing impurities in the crude oil and fat product. Impurities in the crude oil and fat product can be separated and removed by methods known in the art, such as but not limited to centrifugal separation, sedimentation separation, filtration separation and combinations thereof. Then, the obtained oil and fat part can be subjected to oil cleaning treatment.

[0060] Herein, peanut shell powder is used to perform oil clearing treatment on oil. Peanut shell powder can be prepared from newly harvested or sun-dried peanut shells. Specifically, clean peanut shells are taken, dried and crushed to less than 20 meshes, such as 40 to 80 meshes, to obtain the peanut shell powder used in the present invention. The drying temperature can be 40 to 60°C, and the drying time can be 10 to 24 hours. Oven drying or blast drying can be used. In some embodiments, the water content of the peanut shell powder is ≤3wt%. In some embodiments, the water content of the peanut shell powder is ≤2.8wt%. In some embodiments, the water content of the peanut shell powder is 0.5 to 2.8wt%.

[0061] In the oil clearing step, peanut shell powder accounting for 5% to 10% of the weight of the oil can be added to the oil, stirred at 40 to 100° C. for 0.5 to 2 hours, and then separated to obtain the peanut oil of the present invention. In some embodiments, the mixture of peanut shell powder and oil can be stirred in a closed environment for 0.5 to 2 hours. Peanut oil can be separated by methods well known in the art, including conventional filtration or centrifugation.

[0062] The peanut oil prepared by the method of the present invention has a strong sweet flavor, a high smoke point and a high content of resveratrol. Therefore, the present invention also includes a peanut oil with a strong sweet flavor, a smoke point of ≥168°C, preferably ≥170°C, more preferably ≥173°C, and a resveratrol content of ≥150 μg / kg, preferably ≥160 μg / kg, more preferably ≥170 μg / kg. Preferably, the peanut oil is prepared by the method described in any embodiment of the present invention.

[0063] In some embodiments, the present invention also provides a peanut oil, which contains the sweet and fragrant peanut oil of the present invention and one or more other various peanut oils well known in the art, including but not limited to one or more of refined peanut oil, strong fragrant peanut oil, cold pressed peanut oil and small pressed peanut oil. In the peanut oil, the content of the sweet and fragrant peanut oil of the present invention can be 0.5-50wt%.

[0064] In some embodiments, the present invention also provides a blended oil containing the sweet and fragrant peanut oil of the present invention. In addition to the sweet and fragrant peanut oil of the present invention, the blended oil may also contain one or more animal and vegetable oils and fats. The animal and vegetable oils and fats may be natural animal and vegetable oils and fats or processed animal and vegetable oils and fats, including but not limited to one or more of rice oil, butter, soybean oil, rapeseed oil, corn oil, sunflower seed oil, linseed oil, palm oil, rice bran oil and sesame oil. The content of various oils and fats in the blended oil can be determined according to actual needs. Usually, the peanut oil of the present invention can account for 0.5 to 90wt% of the total weight of the blended oil, preferably 1 to 30%.

[0065] In some embodiments, the present invention also provides the use of steam explosion treatment in improving the sweet flavor of peanut oil, or in preparing peanut oil with enhanced sweet flavor. In some embodiments, the pressure of the steam explosion treatment is 0.7-2.0 MPa, and the time is 30-150 s. In some embodiments, the pressure of the steam explosion treatment is 0.7-1.5 MPa, and the holding time is 50-150 s. In some embodiments, the pressure of the steam explosion is 1.8-2.0 MPa, and the holding time is 30-50 s.

[0066] In some embodiments, the present invention also provides the use of steam explosion treatment and oil clearing treatment in improving the sweet flavor of peanut oil, improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil. Preferably, the steam explosion treatment and oil clearing treatment are as described in any embodiment of the present invention.

[0067] In some embodiments, the present invention also provides the use of steam explosion equipment and peanut shell powder in improving the sweet flavor of peanut oil, improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil. Preferably, the steam explosion equipment and peanut shell powder are as described in any embodiment of the present invention.

[0068] In some embodiments, the present invention also provides the use of peanut shell powder in improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil. Preferably, the steam explosion device and peanut shell powder are as described in any embodiment of the present invention.

[0069] In some embodiments, the present invention also provides a method for preparing peanut oil with a strong sweet flavor or improving the sweet flavor of peanut oil, the method comprising the steps of steam explosion of peanut raw materials followed by enzymatic hydrolysis and heat treatment. Preferably, the steam explosion, enzymatic hydrolysis and heat treatment are as described in any embodiment herein.

[0070] The peanut oil or blended oil of the present invention can be used as fat in various foods, including but not limited to seasoning sauces, pre-prepared dishes, convenience foods, snack foods, meat and its products, cold foods, beverages, cakes, etc.

[0071] The present invention will be further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples that do not specify specific conditions are usually based on conventional conditions or the conditions recommended by the manufacturer. Unless otherwise stated, percentages and parts are calculated by weight.

[0072] The sources of the enzymes used in the following examples are as follows:

[0073] Alkaline protease (catalog number: AY50C), Amano Enzyme Co., Ltd.;

[0074] Flavor protease (Cat. No.: AXH), Novozymes Biotech Ltd.;

[0075] Medium-temperature amylase (catalog number: BAN480L), Novozymes Biotech Co., Ltd.;

[0076] Compound saccharifying enzyme (Cat. No.: Dextrozyme DX), Novozymes Biotech Ltd.;

[0077] Pectinase (Cat. No.: Rapidase Smart ClearPlus), DSM.

[0078] The peanut shell powder used in the following examples is prepared by the following method: the dried peanuts in shell are separated by a peanut sheller to obtain peanut shells, the peanut shells are rinsed in clean water, dried at 60°C, and then crushed to 40-80 mesh. Drying is carried out in a blast drying oven. The specific parameters are shown in the following table.

[0079]

[0080]

[0081] Example 1

[0082] Steam explosion treatment: add 1 kg of peanuts into a steam explosion tank, introduce saturated steam to make the pressure inside the tank 1.5 MPa, and maintain the pressure for 60 seconds.

[0083] Enzymatic hydrolysis conditions: 500g of peanut powder treated by steam explosion in a steam explosion tank was taken, and peanut powder and water were mixed in a mass ratio of 1:3, heated in a water bath to 50°C, 50% NaOH solution was added to adjust the pH to 8.5, and 1.5g alkaline protease AY50C (0.3%, based on the mass of peanut powder) was added for enzymatic hydrolysis for 2h, during which the pH of the reaction system was maintained at 8.5. Afterwards, 85% phosphoric acid was added to adjust the pH value of the reaction system to 6.0, 2.5g flavor protease AXH (0.5%, based on the mass of peanut powder), 2.5g medium temperature amylase (0.5%, based on the mass of peanut powder), 5g composite saccharifying enzyme (1%, based on the mass of peanut powder) and 5g pectinase (1%, based on the mass of peanut powder) were added, and enzymatic hydrolysis was carried out for 4h, during which the pH value of the reaction system was maintained at 6.0. After the enzymatic hydrolysis was completed, 50% NaOH solution was added to adjust the pH of the reaction system to 8.0. The enzymatic hydrolyzate was dried at 105°C for 6h and crushed to obtain enzymatic hydrolyzed powder.

[0084] Heat treatment: the enzymatic hydrolyzed powder is mixed with refined peanut oil in a mass ratio of 1:7, and after being stirred evenly, a diaphragm pump is used to evacuate the reactor to a vacuum degree of -0.09 MPa, and the airtight valve is closed. The reaction is carried out at 170°C for 30 minutes, and then the temperature is lowered to 30°C, the vacuum is broken, and the supernatant oil is obtained by centrifugation.

[0085] Clear oil treatment: add peanut shell powder accounting for 10% of the oil weight to the supernatant oil prepared above, stir in a closed environment at 65°C for 1 hour, and then filter to obtain peanut oil.

[0086] Example 2

[0087] The process was carried out in accordance with Example 1, except that the pressure of the steam explosion treatment was 1.2 MPa, and the peanut shell powder added in the oil cleaning step accounted for 5% of the oil weight.

[0088] Example 3

[0089] The process is carried out as in Example 1, except that the heat treatment temperature is 165°C and the time is 40 minutes.

[0090] Example 4

[0091] The process is carried out as in Example 1, except that the heat treatment temperature is 160°C and the time is 40 minutes.

[0092] Example 5

[0093] The process is carried out as in Example 1, except that the heat treatment temperature is 160°C and the time is 30 minutes.

[0094] Example 6

[0095] The process was carried out according to Example 1, except that the amount of flavor protease, medium-temperature amylase, complex saccharifying enzyme and pectinase was 5 g, the heat treatment temperature was 180°C, the time was 40 minutes, and the temperature of clear oil treatment was 90°C.

[0096] Example 7

[0097] The process was carried out in the same manner as in Example 1, except that the pressure of the steam explosion treatment was 0.7 MPa and the time was 150 seconds.

[0098] Example 8

[0099] The process was carried out in accordance with Example 1, except that the pressure of the steam explosion treatment was 2.0 MPa, the time was 30 seconds, and the alkaline protease hydrolysis time was 2.5 hours.

[0100] Example 9

[0101] The process was carried out as in Example 4, except that the heat treatment time was 60 minutes.

[0102] Example 10

[0103] The process was carried out according to Example 6, except that the heat treatment time was 60 minutes and the temperature of the clear oil treatment was 65°C.

[0104] Embodiment 11

[0105] The process was carried out as in Example 10, except that the heat treatment time was 30 minutes.

[0106] Example 12

[0107] The process was carried out according to Example 6, except that the heat treatment temperature was 170°C, the time was 30 minutes, and the peanut shell powder used for the clear oil treatment was peanut shell powder 2.

[0108] Comparative Example 1

[0109] The process was carried out in accordance with Example 1, except that the clear oil treatment was not performed and the supernatant oil obtained by the heat treatment was directly filtered.

[0110] Comparative Example 2

[0111] The process was carried out in accordance with Example 1, except that neither steam explosion nor clear oil treatment was performed, and the supernatant oil obtained by the heat treatment was directly filtered.

[0112] Comparative Example 3

[0113] The process was carried out as in Example 1, except that the steam explosion treatment was not performed.

[0114] Comparative Example 4

[0115] The process is carried out in accordance with Example 1, except that in the oil clearing step, the peanut shell powder 2 added accounts for 15% of the oil weight.

[0116] Comparative Example 5

[0117] The process was carried out as in Example 1, except that the steam explosion pressure was 0.7 MPa and the time was 90 seconds.

[0118] Comparative Example 6

[0119] The process was carried out as in Example 1, except that, in the heat treatment step, no vacuum was applied before the reaction.

[0120] Comparative Example 7

[0121] The process was carried out in accordance with Example 1, except that, in the heat treatment step, the reactor was filled with nitrogen to a pressure of 0.2 MPa after evacuation before the reaction.

[0122] Comparative Example 8

[0123] The process was carried out in accordance with Example 6, except that the pressure of the steam explosion treatment was 2.0 MPa, the time was 150 s, and in the heat treatment step, the reactor was filled with nitrogen to a pressure of 0.2 MPa after evacuation before the reaction.

[0124] Comparative Example 9

[0125] The process was carried out according to Example 6, except that the heat treatment temperature was 170°C, the time was 30 minutes, and the peanut shell powder used for the clear oil treatment was peanut shell powder 3.

[0126] Comparative Example 10

[0127] The process was carried out according to Example 6, except that the heat treatment temperature was 170°C, the time was 30 minutes, and the peanut shell powder used for the clear oil treatment was peanut shell powder 4.

[0128] The main control parameters of Examples 1-12 and Comparative Examples 1-10 are shown in Table 1 below.

[0129] Table 1

[0130]

[0131] 228992 1 CNCN

[0132]

[0133] 228992 1CNCN

[0134]

[0135] Test Case

[0136] (1) Determination of smoke point of oil fume

[0137] The HLY-III oil smoke point tester is used for measurement. The oil sample is placed in a measuring cup and heated. When a small amount of light blue smoke continues to come out of the sample, the temperature is read with the help of a spotlight. This is the smoke point of the sample.

[0138] (2) Sensory evaluation of sweetness and aroma intensity

[0139] First, the samples were randomly coded with three digits, and then 15-20 g of the samples were accurately weighed with an electronic balance into a 50 mL sensory evaluation bottle and stored in a frozen state. The samples were then returned to room temperature for sensory analysis.

[0140] Sensory descriptive method requirements:

[0141] Number of sensory evaluation personnel: 12;

[0142] Evaluation environment: quiet, clean, no odor;

[0143] Personnel background: Member of the peanut oil evaluation team;

[0144] Sampling: Random sampling (i.e. the evaluator smells the samples randomly, and the sample presenter does not specify the order of smelling).

[0145] Conduct descriptive experiments (flavor profile method): sensory evaluators first need to randomly sniff representative attribute samples, rest for 5 minutes after sniffing, and then sniff and evaluate R (standard sample) and compare it with the results after previous discussion to correct the scoring. Then rest for 1 minute and evaluate and score the attributes of the samples to be evaluated (raw taste, steamed taste, sweet aroma, stir-fried aroma, paste aroma, burnt bitter taste, sour taste, and peculiar smell) (0-15 points). After evaluating all the attributes of a sample, rest for 1 minute, and then sniff and evaluate the next sample. Then enter the results according to the median value of the scores of all members for the corresponding attributes.

[0146] (3) Determination of resveratrol content

[0147] Accurately weigh 1g of sample, add 5mL of methanol, vortex shaker for 2min, centrifuge at 6000rpm for 5min. Take all supernatant C18 SPE (500mg, 6mL) through the column, then elute with 3mL of eluent, collect all the solution, blow dry with N2, and re-dissolve with 200μL of dilution solution. Test on Agilent 12690 / AB Sciex QTRAP4500 liquid chromatography-mass spectrometry analyzer;

[0148] Liquid phase conditions: Chromatographic column: WATERS Nova- C18 3.9×150mm×4μm; mobile phase: A (acetonitrile): B (0.01% formic acid aqueous solution) = 35:65; flow rate: 0.3mL / min; detection time: 11min; injection volume: 5μL; ② Mass spectrometry conditions monitoring mode: negative mode; scanning mode: MRM.

[0149] The measurement results are shown in Table 2 below.

[0150] Table 2

[0151] Sweet aroma intensity Smoke point(℃) Total resveratrol (μg / kg) Example 1 9.4 178 187.61 Comparative Example 1 8.7 165 0.96 Comparative Example 2 3.5 165 1.81 Comparative Example 3 2.7 163 171.36 Comparative Example 4 5.1 160 222.01 Example 2 10.0 171 153.13 Example 3 11.2 175 175.72 Example 4 9.7 178 174.26 Example 5 8.9 174 173.44 Example 6 8.1 172 160.85 Example 7 8.7 169 150.76 Comparative Example 5 6.6 165 102.85 Example 8 8.3 174 183.59 Comparative Example 6 4.0 164 105.51 Comparative Example 7 1.0 163 116.30 Comparative Example 8 0.5 167 121.64 Comparative Example 9 8.9 165 179.75 Comparative Example 10 8.7 160 176.47 Example 9 8.3 175 163.06 Example 10 8.1 176 161.7 Embodiment 11 8.2 174 162.45 Example 12 9.2 176 181.24

[0152] As can be seen from Table 1, without the oil treatment (Comparative Examples 1 and 2), the total resveratrol is extremely low. By comparing Example 1, Comparative Example 1 and Comparative Example 3, it can be seen that steam explosion promotes the sweetness without adding shell powder oil. The results of Example 1 and Comparative Examples 1-3 prove that steam explosion and shell powder addition have a synergistic effect on reducing the smoke point of peanut oil.

[0153] From the comparison between Examples 1-3 and Comparative Example 4, it can be found that the appropriate amount of shell powder added is 5% to 10%. When the shell powder is excessive, although a higher content of resveratrol is obtained, the smoke point of peanut oil is seriously affected, and the sweet aroma is also damaged.

[0154] In Comparative Example 5, the processing time was shorter under the condition of lower steam explosion pressure, and as a result, its sweetness, smoke point and total resveratrol content were all lower than those of Examples 1-8.

[0155] The results of Comparative Example 6 show that, compared with Example 1, in the thermal reaction step, no vacuum was drawn before the reaction, resulting in the sweet aroma, smoke point and resveratrol content being affected. The results of Comparative Example 7 show that, compared with Example 1, in the thermal reaction step, nitrogen was filled in after vacuum drawing before the reaction, resulting in excessive pressure in the container during the reaction, which ultimately also affected the sweet aroma, smoke point and resveratrol content. The results of Comparative Example 8 show that the steam explosion treatment has high pressure and long time, and nitrogen was filled in after vacuum drawing before the reaction, resulting in excessive pressure in the container during the reaction, which seriously affected the sweet aroma, and the smoke point and resveratrol content were also significantly damaged.

[0156] Application Examples

[0157] Peanut oils 1 to 4 and blended oils 1 to 4 were prepared according to Table 3, and the percentages in the table are weight percentages. The peanut oil in the table is the peanut oil prepared in Example 1; the refined peanut oil in other oils was purchased from Kerry Grain and Oil (Qingdao) Co., Ltd., the fragrant peanut oil and sesame oil were purchased from Kerry Grain and Oil (Qingdao) Co., Ltd., and the first-grade soybean oil and first-grade sunflower seed oil were purchased from Shanghai Kerry Grain and Oil Industry Co., Ltd.

[0158] Table 3

[0159]

[0160]

[0161] The sweetness and smoke point of the peanut oils 1 to 4 and the blended oils 1 to 4 were tested using the method described above. The results are shown in Table 4 below.

[0162] Table 4

[0163] Sweet aroma intensity Smoke point(℃) Peanut Oil1 1.0 219 Peanut Oil2 2.8 207 Peanut Oil3 6.2 166 Peanut Oil4 7.7 169 Blending oil 1 1.5 218 Blending oil 2 1.5 217 Blending oil 3 2.0 216 Blending oil 4 2.0 214

Claims

1. A method for preparing peanut oil, characterized in that: The method comprises steam explosion treatment, enzymatic hydrolysis, heat treatment and oil cleaning steps; The steam pressure of the steam explosion treatment is 0.7MPa-2.0MPa, and the holding time is 30-150 seconds; when the steam pressure is ≤0.8MPa, the holding time is 100-150 seconds, and when the steam pressure is ≥1.8MPa, the holding time is ≤50s; The clear oil comprises: adding peanut shell powder accounting for 5-10% of the weight of the oil to the oil obtained by heat treatment, and stirring at 40-100° C. for 0.5-2 hours.

2. The method according to claim 1, characterized in that The peanuts are crushed after steam explosion, and the obtained peanut powder is mixed with water and subjected to enzymatic hydrolysis; Preferably, the enzyme used for enzymolysis is selected from: one or more of neutral protease, alkaline protease, flavor protease, endoprotease, exoprotease, papain, trypsin, high-temperature amylase, medium-temperature amylase, fungal amylase, bacterial amylase, cellulase, hemicellulase, glucanase, complex saccharifying enzyme, pectinase, pullulanase, polygalacturonase and sucrose invertase; More preferably, the enzyme used for enzymolysis is selected from one or more of alkaline protease, flavor protease, medium-temperature amylase, complex saccharifying enzyme and pectinase; Preferably, the total amount of enzymes used for enzymolysis is 1-6% by weight of the peanuts, such as 2-6%; Preferably, the enzymes used for enzymolysis include alkaline protease, flavor protease, mesophilic amylase, composite saccharifying enzyme and pectinase; based on the weight of peanuts, the amount of alkaline protease is 0.1-2%, such as 0.1-1.0%; the amount of flavor protease is 0.1-3%, such as 0.1-1.0%; the amount of mesophilic amylase is 0.1-3%, such as 0.1-1.0%; the amount of composite saccharifying enzyme is 0.1-3%, such as 0.5-2.0%; the amount of pectinase is 0.1-3%, such as 0.5-2.0%; Preferably, the enzymatic hydrolysis is carried out at 30-70°C and pH 5-9, and the reaction time is 3-15 hours; Preferably, in the enzymatic hydrolysis reaction system, the mass ratio of peanut powder to water is 1:1 to 1:10, preferably 1:2 to 1:

8.

3. The method according to claim 1 or 2, characterized in that Firstly, alkaline protease is used for enzymolysis, and then flavor protease, medium-temperature amylase, compound saccharifying enzyme and pectinase are added for enzymolysis after the enzymolysis is completed; Preferably, when alkaline protease is used for enzymolysis, its dosage is 0.1-1.0% of the mass of peanuts, and the pH of the enzymolysis reaction system is 8.0-9.0; Preferably, when flavor protease, medium-temperature amylase, composite saccharifying enzyme and pectinase are used for enzymolysis, the pH of the reaction system is 5.5-6.5, wherein, based on the weight of peanuts, the amount of flavor protease is 0.1-1.0%, the amount of medium-temperature amylase is 0.1-1.0%, the amount of composite saccharifying enzyme is 0.5-2.0%, and the amount of pectinase is 0.5-2.0%; Preferably, during the enzymatic hydrolysis process, the pH value of the reaction system is maintained at ±0.2 of the initial pH value of the reaction, and the pH value is within the range of 8.0 to 9.0 or 5.5 to 6.

5.

4. The method according to any one of claims 1 to 3, characterized in that After the enzymolysis is completed, the pH of the enzymolysis solution is adjusted to a range of 7.5 to 8.5, preferably 7.8±0.2, and then dried to obtain enzymolysis powder; preferably, the drying is selected from freeze drying, spray drying, rolling scraper drying and vacuum drying.

5. The method according to any one of claims 1 to 4, characterized in that: The heat treatment comprises: mixing the product obtained by enzymatic hydrolysis with peanut oil, and then subjecting the obtained mixture to heat treatment; Wherein, the mass ratio of the product to peanut oil is 1:2-10, such as 1:4-10 or 1:5-8; The heat treatment temperature is 160-180°C, and the heat treatment time is 0.5-1 hour. During the heat treatment, the pressure in the reaction vessel does not exceed 0.7 MPa, preferably 0.2-0.7 MPa, and more preferably 0.3-0.6 MPa. Preferably, after the heat treatment, the oil is separated and the oil is subjected to the oil clearing treatment.

6. The method according to any one of claims 1 to 5, characterized in that The peanut shell powder is prepared as follows: clean peanut shells are taken, dried to a moisture content of ≤3.0wt%, and then crushed to less than 20 meshes, preferably 40-80 meshes, to obtain the peanut shell powder; preferably, the drying temperature is 40-60°C, and the drying time is 10-24h.

7. Peanut oil prepared by the method according to any one of claims 1 to 6; Preferably, the smoke point of the peanut oil is ≥168°C, preferably ≥170°C, more preferably ≥173°C; the resveratrol is ≥150 μg / kg, preferably ≥160 μg / kg, more preferably ≥170 μg / kg.

8. A blended oil or a food containing the blended oil, characterized in that: The blended oil contains the peanut oil according to claim 7; preferably, the food is selected from seasoning sauces, pre-prepared dishes, convenience foods, snack foods, meat and its products, cold foods, beverages and cakes.

9. Select from the following applications: (1) Application of steam explosion treatment in improving the sweet flavor of peanut oil, or in preparing peanut oil with enhanced sweet flavor; preferably, the pressure of the steam explosion treatment is 0.7-2.0 MPa, and the time is 30-150 s; more preferably, the pressure of the steam explosion treatment is 1.0-2.0 MPa, and the time is 50-150 s, such as 50-100 s; (2) Application of steam explosion treatment and oil clearing treatment in improving the sweet flavor of peanut oil, improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil; preferably, the steam explosion treatment and oil clearing treatment are as described in claim 1; (3) Application of steam explosion equipment and peanut shell powder in improving the sweet flavor of peanut oil, improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil; preferably, the steam explosion equipment comprises a gas explosion tank, and the peanut shell powder is prepared by the method according to claim 6; (4) Application of peanut shell powder in improving the smoke point of peanut oil and increasing the resveratrol content of peanut oil; preferably, the peanut shell powder is prepared by the method according to claim 6.

10. A method for preparing peanut oil with a strong sweet aroma or improving the sweet aroma of peanut oil, characterized in that: The method comprises the steps of steam explosion treatment on peanut raw materials and then enzymatic hydrolysis and heat treatment; wherein the steam pressure of the steam explosion treatment is 0.7MPa-2.0MPa, and the pressure holding time is 30-150 seconds; wherein, when the steam pressure is ≤0.8MPa, the pressure holding time is 100-150 seconds, and when the steam pressure is ≥1.8MPa, the pressure holding time is ≤50s; Preferably, the enzymatic hydrolysis treatment is as described in any one of claims 2 to 4; Preferably, the heat treatment is as described in claim 5.

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