Rice oil and preparation method thereof

Abstract

The invention belongs to the field of edible oil processing. Specifically, the invention provides a grease deodorization method, the method comprises the step of deodorizing decolored oil to be deodorized, and the oil to be deodorized contains circulating decolored oil which is decolored at least twice. By controlling the content of DG in the raw materials and the addition amount and deodorization temperature of circulating decolorized oil in the deodorization step, the content of 3-chloropropanol ester in the prepared grease can be reduced, the color of the grease is reduced, and meanwhile the frying frequency of the grease is prolonged.

Description

Technical Field

[0001] The present invention belongs to the field of edible oil processing, and particularly relates to a rice bran oil and a preparation method thereof. Background Art

[0002] The pollution of fatty acid chloropropanol esters is one of the food safety problems, especially the pollution problem of 3-chloro-1,2-propylene glycol ester (3-MCPD ester). Research shows that 3-MCPD esters in edible vegetable oils are mainly formed during the refining process, while unrefined edible vegetable oils contain almost no 3-MCPD esters.

[0003] In the actual production process of rice bran oil, there are the following two main problems: 1. Since rice bran contains a large amount of lipase, the content of free fatty acids and diglycerides (DG) in rice bran oil is generally high; 2. Rice bran oil contains more impurities and has a darker color, and these colors are not easy to remove. Therefore, in the refining process, in order to overcome the above problems, multiple decolorization steps are usually carried out, the temperature of steam distillation for deacidification and deodorization is increased, and the time for deacidification and deodorization is increased, etc. However, the deodorization process will cause a significant increase in the content of 3-chloropropanol esters. The higher the deodorization temperature and the longer the deodorization time, the greater the increase in 3-chloropropanol esters, and the deodorization temperature has a greater impact than the deodorization time. On the other hand, reducing the deodorization temperature and shortening the deodorization time will both cause the color of the oil to deepen, resulting in faster waste of the oil during frying of food materials and reducing the yield of the food. Therefore, it is largely impossible to simultaneously control the content of 3-chloropropanol esters in the oil and reduce the color of the oil.

[0004] CN111349513B discloses a processing technology for controlling the formation of 3-MCPD esters and glycidyl esters in edible oils, including the following steps: (1) filtering crude oil and adding a mixed auxiliary agent, stirring and mixing at room temperature and ultrasonicating, and centrifuging to separate to obtain an oil phase; (2) adding a mixed auxiliary agent to the oil phase obtained in step (1), stirring and mixing at room temperature and ultrasonicating, and centrifuging to separate to obtain an oil phase; repeating the operation 6 times; (3) adding silica gel for degumming to the edible oil of the oil phase obtained after centrifuging in step (2), centrifuging and separating to obtain an oil phase, repeating twice, filtering the obtained oil phase, decolorizing, filtering again, and then performing low-temperature deodorization on the edible oil and entering a deacidification device for low-temperature rapid deacidification to obtain the finished oil. This technology can remove plasticizers in the early stage and does not require a high-temperature distillation step in the later stage, thus avoiding the formation of glycidyl esters and 3-MCPD esters caused by high temperature.

[0005] CN112940853B provides an edible vegetable oil with low contents of 3-monochloropropanediol esters and glycidyl esters, a preparation method thereof, and applications thereof. The preparation method includes: taking crude vegetable oil for hydration degumming treatment to obtain degummed oil; taking the degummed oil for caustic refining and alcohol washing treatment to remove free fatty acids in the oil and reduce the contents of monoglycerides and diglycerides in the oil, so as to obtain an oil with a low acid value and low contents of monoglycerides and diglycerides; wherein, the reaction conditions of the caustic refining and alcohol washing treatment include: the over-alkali addition coefficient is 0.05% - 0.3%, the elution solvent for the caustic refined oil is ethanol or an aqueous ethanol solution with an ethanol content of not less than 70%, the ratio of the alcohol washing feed liquid is 1:3 - 1:5, and the number of alcohol washing times is 1 - 3 times; taking the oil with low contents of monoglycerides and diglycerides for steam distillation deodorization treatment to obtain an edible vegetable oil with low contents of 3-monochloropropanediol esters and glycidyl esters.

[0006] CN115605566A provides a method for preventing or reducing the formation of monochloropropanediol (MCPD) or monochloropropanediol esters (MCPDE) in triacylglycerol oil. The method includes the following steps: (a) mixing the triacylglycerol oil with a liquid to form a blend, wherein the liquid is selected from one or more of water, an acid solution, an alkali solution, a phospholipid solution, and a surfactant solution; (b) optionally homogenizing the blend; (c) performing one or more of the following steps: 1. heating the blend during homogenization; and 2. heating the blend; (d) cooling the blend to below 100°C; (e) optionally concentrating the insoluble crystalline components from the blend by: 1. applying centrifugal force to the blend; and / or 2. allowing the insoluble crystalline components in the blend to settle by gravity; (f) separating the aqueous insoluble phase and the crystalline components from the blend and / or applying one or more processes selected from the following to the blend: degumming, physical refining, chemical refining, neutralization, transesterification, bleaching, dewaxing, and fractionation; (g) applying a heat treatment to the blend.

[0007] CN115106075A provides an activated carbon, a preparation method thereof, and applications thereof in oils and fats. The mass percentage content of silicon dioxide in the activated carbon is 5.5% - 30%. The inventors unexpectedly found that by controlling the conductivity, pH, silicon dioxide content, and metal ion content of rice husk ash, the reaction of oils and fats occurs under non-vacuum conditions. On the premise of meeting the physical properties of transesterified oils and fats, the phosphorus content and soap content in the oils and fats can be reduced, the color and luster of the oils and fats can be improved, and the contents of 3-MCPD esters and GE in the oils and fats can be synchronously reduced, obtaining high-quality transesterified oils and fats with low pollutants, and the degree of transesterification can be controlled by process parameters. While completing the transesterification modification, the contents of various pollutants in the final oil and fat products can be effectively controlled, which is applicable to industrial production of oils and fats.

[0008] CN106916630B discloses a method for controlling the generation of harmful substances in oils and fats. Specifically, the present invention provides a method for reducing harmful substances during the deodorization of oils and fats, or a method for deodorizing or preparing oils and fats, which includes deodorizing an oil and fat raw material, wherein the oil and fat raw material contains (1) inositol fatty acid esters, and (2) food acids and / or oils and fats that omit some refining processes. By adding inositol fatty acid esters, food acids or oils and fats that omit some refining processes during the deodorization process, the present invention achieves the effect of controlling the content of chloropropanol esters in oils and fats through the synergistic effect between inositol fatty acid esters and food acids and optionally oils and fats that omit some refining processes.

[0009] From the above prior art, it can be seen that the currently commonly used methods for controlling 3-chloropropanol esters in oils and fats mainly include pretreatment of oils and fats, adding specific additives during the processing, or performing special modification on the additives, and secondary processing of the finished oils and fats, etc. However, these methods are complex in operation, increase the oil and fat refining process, reduce production efficiency, and also increase the oil and fat refining cost, which has an adverse impact on production enterprises. Moreover, reducing the deodorization temperature and shortening the deodorization time will also cause the color of the oils and fats to deepen, resulting in rapid scrapping of the oils and fats during use (such as frying foods), and reducing the yield of the food. Therefore, it is largely impossible to both control the content of 3-chloropropanol esters in oils and fats and reduce the color of the oils and fats. Therefore, on the premise of ensuring product quality, new control processes also need to be developed to produce products with low color and low 3-chloropropanol esters to meet the needs of production enterprises and consumers. Summary of the Invention

[0010] The first aspect of the present invention provides a method for deodorizing oils and fats, which includes deodorizing the decolorized oil to be deodorized, and the decolorized oil to be deodorized contains at least recycled decolorized oil that has been decolorized at least twice.

[0011] In one or more embodiments, the recycled decolorized oil is the decolorized oil obtained by mixing decolorized oil and oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3 and then performing decolorization.

[0012] In one or more embodiments, the oil and fat is rice oil.

[0013] In one or more embodiments, the pressure of the deodorization system is 0.1 - 0.5 kPa.

[0014] In one or more embodiments, the temperature of the deodorization system is 210 - 250 °C, such as 220 - 250 °C or 235 - 250 °C.

[0015] In one or more embodiments, the deodorization time is 1 - 3 h.

[0016] The second aspect of the present invention provides an oil refining method, which includes an oil deodorization method as described in any of the embodiments herein, and one or more steps selected from degumming, dewaxing, deacidification, neutralization, and decolorization.

[0017] In one or more embodiments, the oil is rice oil.

[0018] In one or more embodiments, the oil is crude rice bran oil with a DG content < 10%, preferably a DG content ≤ 8%.

[0019] In one or more embodiments, the decolorization includes: mixing the decolorized oil and the oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3, and then performing decolorization to obtain a recycled decolorized oil. A part of the recycled decolorized oil is deodorized, and the remaining part is mixed with the oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3, and then decolorized again to obtain a recycled decolorized oil. Then, a part of the recycled decolorized oil is mixed with the oil to be decolorized for re-decolorization, and a part is deodorized until all the oil to be decolorized is decolorized and deodorized.

[0020] In one or more embodiments, the degumming includes adding a degumming medium not less than 0.05 wt% of the weight of the crude oil to the crude oil and performing degumming at a temperature of 45 - 80°C.

[0021] In one or more embodiments, the dewaxing includes pumping the degummed oil into a crystallization tank, controlling the temperature to 50 - 70°C, standing for 20 - 40 min, then cooling to 20°C within 35 - 45 hours, and crystallizing at 20°C for 5 - 15 hours. After crystallization, filtration is performed.

[0022] In one or more embodiments, the deacidification includes treating the dewaxed oil at a temperature of 40 - 80°C or deacidifying by the caustic refining method; optionally, after caustic refining, soap removal and drying steps are included.

[0023] In one or more embodiments, the decolorization includes adding a decolorizing agent to the oil to be decolorized, stirring for 10 min - 2 h under the conditions of 100 - 120°C and 2 - 5 kPa, and then filtering to remove the decolorizing agent.

[0024] The third aspect of the present invention provides an oil processed by the method as described herein, or an oil composition containing the oil;

[0025] In one or more embodiments, the 3-MCPD ester content of the oil is less than or equal to 4.0 mg / kg, preferably less than or equal to 2.5 mg / kg, more preferably less than or equal to 1.5 mg / kg; and / or the red color value of the oil is less than or equal to 5, preferably less than or equal to 3, more preferably less than or equal to 2.

[0026] In the fourth aspect of the present invention, a decolorized oil is provided. The decolorized oil is obtained by decolorizing a mixture of the decolorized oil and the oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3; preferably, the decolorized oil is derived from decolorized rice bran oil, and the oil to be decolorized is degummed rice bran oil; preferably, the decolorized rice bran oil is derived from crude rice bran oil with a DG content < 10%, preferably a DG content ≤ 8%.

[0027] The fifth aspect of the present invention provides the application of the recycled decolorized oil as described in any embodiment herein in reducing the content of 3-MCPD esters in oils and fats, reducing the red value of the color of oils and fats, and / or extending the number of frying times of oils and fats; or the application of the method as described in any one of claims 1 to 7 in reducing the content of 3-MCPD esters in oils and fats, reducing the red value of the color of oils and fats, and / or extending the number of frying times of oils and fats. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a schematic diagram of the oil processing method of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0029] To enable those skilled in the art to understand the features and effects of the present invention, the following provides a general description and definition of the terms and phrases mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used herein shall have the ordinary meaning understood by those skilled in the art for the present invention. In case of conflict, the definition in this specification shall prevail.

[0030] The theories or mechanisms described and disclosed herein, whether correct or incorrect, shall not in any way limit the scope of the present invention, that is, the content of the present invention can be implemented without being limited by any specific theory or mechanism.

[0031] As used herein, terms such as "comprising", "including", "containing" and similar terms encompass the meanings of "consisting essentially of" and "consisting of". For example, when it is disclosed herein that "A comprises B and C", it should be considered that "A consists essentially of B and C" and "A consists of B and C" have been disclosed herein.

[0032] In this article, all features defined in the form of numerical ranges or percentage ranges, such as numerical values, quantities, contents and concentrations, are only for the sake of brevity and convenience. Accordingly, the description of numerical ranges or percentage ranges should be regarded as having covered and specifically disclosed all possible sub-ranges and individual numerical values within the ranges (including integers and fractions).

[0033] In this article, unless otherwise specified, the percentage refers to the mass percentage and the ratio refers to the mass ratio.

[0034] In this text, the sum of the percentage contents of the components of the composition is 100%.

[0035] In this text, when describing the embodiments or examples, it should be understood that they are not used to limit the present invention to these embodiments or examples. On the contrary, all alternatives, improvements and equivalents of the methods and materials described in the present invention can be covered within the scope defined by the claims.

[0036] In this text, for the sake of brevity of description, 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 as the scope described in this specification.

[0037] The present invention discovers that by controlling the DG content in the rice bran raw material, adding recycled decolorized oil in the deodorization step and controlling the deodorization temperature and the proportion of decolorized oil in each cycle of the recycled decolorized oil, the content of 3-chloropropanol esters in the prepared oil can be reduced, the color of the oil can be reduced, and at the same time, the number of times the oil can be fried can be extended. Thus, the present invention is completed.

[0038] The present invention provides a method for deodorizing oil, and the oil is crude rice bran oil with a DG content < 10%, preferably a DG content ≤ 8%.

[0039] In the present invention, the specific process of deodorization is well known to those skilled in the art. For example, but not limited to, the method in "Bailey's Industrial Oil and Fat Products" (Volume VI) can be used. Generally, deodorization may include: introducing nitrogen or steam into the oil as a deodorizing medium, and allowing the oil to contact with nitrogen or steam for a period of time under certain temperature and vacuum conditions. In addition, a conventional deodorizing device can also be used for deodorization, such as a deodorizing tower. In this text, the pressure of the exemplary deodorization reaction system can be 0.1 - 0.5 kPa, the exemplary deodorization temperature can be 210 - 250 °C, preferably 220 - 250 °C, such as 235 - 250 °C, and the exemplary deodorization time can be 1 - 3 h, preferably 1.5 - 2.5 h.

[0040] In the present invention, the decolorized oil for deodorization contains recycled decolorized oil that has been decolorized two or more times. Herein, "recycled decolorized oil" refers to decolorized oil that has undergone two or more decolorization treatments. Specifically, during the decolorization process of the present invention, after each decolorization is completed, 10-90 wt% of the decolorized oil based on the weight of the decolorized oil is mixed with the next batch of oil to be decolorized (such as degummed oil) for recycled decolorization. Exemplary recycled decolorization includes mixing 10-90 wt% of the first batch of decolorized oil with the oil to be decolorized such as degummed oil for the second batch of decolorization; after the second batch of decolorization is completed, similarly, 10-90 wt% of the decolorized oil of this batch is mixed with the oil to be decolorized such as degummed oil for the third batch of decolorization, and so on. In some embodiments, in the recycled decolorization, the recycling ratio of the decolorized oil can be 10-70 wt% or 10-50 wt% or 50-70 wt%. In each batch of decolorization, the ratio of the recycled decolorized oil to the oil to be decolorized can be in the range of 1:9 to 9:1, for example, in the range of 1:9 to 7:3, or in the range of 1:9 to 1:1, or in the range of 1:1 to 7:3.

[0041] The present invention has no particular limitations on the decolorizing agent or reaction conditions used in decolorization. Exemplary decolorization includes adding a decolorizing agent to the oil. Exemplary decolorizing agents include, but are not limited to, activated clay, attapulgite, zeolite, acidified rice husk ash, magnesium silicate, diatomaceous earth, perlite, and activated carbon. One decolorizing agent or any mixture of two or more decolorizing agents can be used. When using two or more decolorizing agents, there are no special restrictions on the dosage ratio between the decolorizing agents in the decolorizing agent mixture. Exemplary decolorizing agents can be activated clay. Generally, the addition amount of the decolorizing agent used in the present invention is 1-5% by weight of the oil, preferably 2-4%, and there are no special restrictions on the decolorization time and temperature, which can be determined according to the specific type of crude oil, the type of decolorizing agent used, and the amount of the decolorizing agent by conventional means. The pressure of the reaction system is 2-5 kPa or 3-5 kPa, the decolorization temperature is 100-120 °C or 100-115 °C, and the decolorization time is 10 min-2 h or 10-60 min.

[0042] In some embodiments, the oil refining method of the present invention includes the oil deodorization step described herein and one or more selected from the steps of degumming, dewaxing, deacidification, neutralization, and decolorization. It should be understood that depending on the actual production situation and production purpose, one or more of the degumming, degreasing / dewaxing, deacidification, neutralization, and decolorization can be omitted. The process conditions of the degumming, degreasing / dewaxing, deacidification, neutralization, and decolorization can be conventional process conditions in the art and can be adjusted according to the actual production situation.

[0043] Exemplary degumming includes filtering the crude oil to remove solid impurities and then adding a degumming medium to degum the crude oil. The degumming agent can be a conventional degumming agent in the art, such as citric acid, phosphoric acid solution, and degumming enzyme. When using a degumming enzyme (such as PLA1 phospholipase), the reaction system is generally at 45-80°C for 2-8 hours. The degumming medium is not less than 0.05 wt% of the weight of the crude oil and usually not more than 2 wt% of the weight of the crude oil. When using an acid, based on the total weight of the solution, the concentration of the acid is not less than 5 wt% and usually not more than 80 wt%, for example, it can be in the range of 5-65 wt%, 10-60 wt%, 20-50 wt%. Water can be added simultaneously, and usually the amount of water is not less than 0.5 wt% of the weight of the crude oil; usually the amount of water used in a single degumming step is not more than 30 wt% of the oil weight, for example, in the range of 0.5-20 wt%, 0.5-10 wt%, 5-25 wt%. The amount of water does not include the water in the degumming medium. After the reaction, the gum is separated to obtain degummed oil.

[0044] In some embodiments, the crude oil is degummed using PLA1 phospholipase. The added mass of the phospholipase is 10-1000 mg / kg of the mass of the crude oil, the reaction temperature is 45-50°C, the reaction time is 4-6 hours, the reaction pH value is 5-5.3, and after the reaction, the gum is separated to obtain degummed oil.

[0045] In some embodiments, dewaxing is carried out after degumming. Exemplary dewaxing includes pumping the degummed oil into a crystallization tank, controlling the temperature to 50-70°C, stabilizing for a period of time such as 20-40 minutes, and then starting to cool and crystallize. It is reduced to about 20°C within 35-45 hours, and then the crystals are grown at this temperature for 5-15 hours. After the crystal growth is completed, filtration is carried out.

[0046] Exemplary degreasing / dewaxing process includes pumping the oil to be degreased into a crystallization tank, controlling the temperature to 50-60°C, standing for 10-60 minutes, and then starting to cool and crystallize. It can be reduced to 0-6°C within 10-60 hours, and then the crystals are grown at this temperature for 6-10 hours. After the crystal growth is completed, filtration is carried out.

[0047] The main purpose of deacidification is to remove free fatty acids in the crude oil, and at the same time remove some impurities such as pigments, phospholipids, hydrocarbons, and mucilage. Physical deacidification methods can be used for deacidification. For example, the degummed oil can be treated at a pressure of 0.02-0.6 kPa and a temperature of 180-250°C to obtain deacidified oil. Or, the alkali refining method can be used for deacidification. For example, at 40-80°C, an appropriate amount of alkali solution is added to the degummed oil and reacted for 10-60 minutes. Usually, the amount of alkali added = 7.13×10 -4 ×M 油 ×AV×(1 + over-alkali amount), the over-alkali amount can be 0-20%, and the amount of alkali solution = the amount of alkali added / the concentration of the alkali solution, where M 油The oil weight is referred to as such, and AV refers to the acid value. After the reaction is completed, centrifugation can be carried out to obtain neutralized oil. The rotational speed of centrifugation can be 5000 - 10000 rpm.

[0048] If the acid removal is carried out by the caustic refining method, the caustic refined oil (neutralized oil) can be washed with water and dried first for soap removal to obtain soap - removed oil. For example, the neutralized oil can be heated to 80 - 90 °C, washed with hot water at 5 wt% or less (such as 1 - 3 wt%) of the oil weight, and then subjected to vacuum drying treatment at 90 - 120 °C after centrifugation to obtain soap - removed oil. It should be understood that when necessary, physical acid removal can be carried out first and then caustic refining.

[0049] Using the method of the present invention can reduce the content of 3 - MCPD esters in the oil, reduce the red value of the oil color, and / or extend the number of frying times of the oil. Therefore, in some embodiments, the present invention also provides a method for reducing the content of 3 - MCPD esters in the oil, reducing the red value of the oil color, and / or extending the number of frying times of the oil, and this method includes the step of preparing the oil by using the method described in any embodiment herein.

[0050] The present invention also includes the oil treated by using the method described in any embodiment of the present invention. Preferably, herein, the oil is rice oil. The deacidified oil is deacidified rice oil, and the decolorized oil is decolorized rice oil.

[0051] In some embodiments, the content of 3 - MCPD esters in the oil treated by using the method of the present invention is less than or equal to 4.0 mg / kg, preferably less than or equal to 2.5 mg / kg, and more preferably less than or equal to 1.5 mg / kg.

[0052] In some embodiments, the red value of the color of the oil treated by using the method of the present invention is less than or equal to 5, preferably less than or equal to 3, and more preferably less than or equal to 2.

[0053] In some embodiments, the number of frying batches of the oil treated by using the method of the present invention is greater than or equal to 50 times, preferably greater than or equal to 55 times, and more preferably greater than or equal to 60 times.

[0054] In some embodiments, the present invention also provides a decolorized oil, which is a decolorized oil obtained by mixing the decolorized oil and the oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3, and then carrying out decolorization; preferably, the recycled decolorized oil is derived from decolorized rice oil, the oil to be decolorized is deacidified rice oil; preferably, the decolorized rice oil is derived from rice bran crude oil with DG content < 10%, preferably DG content ≤ 8%.

[0055] In some embodiments, the present invention also provides the application of the method described in any one of the embodiments herein in reducing the content of 3-MCPD esters in oils and fats, reducing the red value of the color of oils and fats, and / or extending the number of frying times of oils and fats, as well as the application of the decolorized oil described in any one of the embodiments of the present invention in reducing the content of 3-MCPD esters in oils and fats, reducing the red value of the color of oils and fats, and / or extending the number of frying times of oils and fats.

[0056] The present invention has the following beneficial effects:

[0057] By optimizing the raw materials and adopting the processes of cyclic decolorization and moderate refining, the present invention can reduce the content of 3-chloropropanol esters in the prepared oils and fats, reduce the color of the oils and fats, and at the same time extend the number of frying times of the oils and fats.

[0058] The present invention will be further described below by way of specific examples. It should be understood that these examples are merely illustrative and not intended to limit the scope of the present invention. The methods and reagents used in the examples are conventional methods and reagents in the art unless otherwise specified.

[0059] Detection methods

[0060] (a) The detection method for 3-chloropropanol esters refers to AOCS Cd 29c-13.

[0061] (b) The color detection refers to the Lovibond colorimetry method.

[0062] (c) Frying test of tempura shrimp:

[0063] 1) Cleaning: Use penaeus vannamei, remove the shrimp head, shell, shrimp vein and the sharp corner at the tail of the shrimp, wash it repeatedly with clean water, and make a cut on the abdomen of the shrimp;

[0064] 2) Coating with flour: Coat the processed shrimp with a thin layer of wheat flour;

[0065] 3) Coating with batter: Coat the shrimp after coating with flour with batter (egg juice: flour = 2:1, prepared with cold water), and drain the batter slightly;

[0066] 4) Frying: Fry at 195 °C for 150 s and then take out of the pan. Immediately conduct sensory evaluation after taking out of the pan.

[0067] Sensory evaluation of tempura shrimp:

[0068] The sensory evaluation is based on the color and flavor of the tempura shrimp. When the food has an obvious oxidized flavor or the color of the food exceeds 5.0 (a value in the Lab value), stop producing the product and record the total number of batches produced.

[0069] Comparative Example 1

[0070] (1) Method for preparing oil and fat:

[0071] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 10% of the mass of the crude oil.

[0072] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, PLA1 phospholipase is used to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction, the gum is separated to obtain degummed oil.

[0073] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and carry out crystallization at 20 °C for 10 hours. After crystallization, filter.

[0074] 4. Deacidification: Add an aqueous sodium hydroxide solution with the theoretical base amount of acid value to the dewaxed oil, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil.

[0075] 5. Washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying.

[0076] 6. Decolorization: Add 3% of the oil weight of clay to the deacidified oil obtained in the previous step in the decolorization tower. React at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the first batch of decolorized oil after decolorization. 50 wt% of the obtained first batch of decolorized oil (once decolorized oil) is directly pumped into the deodorization tower; 50 wt% of the obtained first batch of decolorized oil is sent back to the decolorization tower and undergoes secondary decolorization under the same conditions together with the second batch of undecolorized oil to be decolorized. Then, 50 wt% of the secondary decolorized oil obtained from the secondary decolorization is sent back to the decolorization tower and undergoes tertiary decolorization under the same conditions together with the third batch of undecolorized oil to be decolorized. Then, 50 wt% of the tertiary decolorized oil obtained from the tertiary decolorization is sent back to the decolorization tower and undergoes quaternary decolorization under the same conditions together with the fourth batch of undecolorized oil to be decolorized. Decolorize in this way in a cycle until all the oil to be decolorized is decolorized. Then, pump all the decolorized oil (cycle decolorized oil) obtained from the cycle decolorization into the deodorization tower;

[0077] 7. Deodorization: Deodorize the once decolorized oil and the cycle decolorized oil pumped into the deodorization tower respectively. The system pressure is 0.2 kPa, the temperature is 235 °C, and process for 2 h to obtain deodorized oil.

[0078] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0079] Comparative Example 2

[0080] (1) Method for preparing oil:

[0081] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0082] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, PLA1 phospholipase is used to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction, the gum is separated to obtain degummed oil;

[0083] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and carry out crystallization at 20 °C for 10 hours. After the crystallization is completed, filter;

[0084] 4. Deacidification: Add an aqueous sodium hydroxide solution with the theoretical base amount of acid value to the dewaxed oil, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0085] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0086] 6. Decolorization: Add 3% of clay based on the weight of the oil to the deacidified oil obtained in the previous step in the decolorization tower. React at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the first batch of decolorized oil after decolorization. 95 wt% (primary decolorized oil) of the obtained first batch of decolorized oil is directly pumped into the deodorization tower; 5 wt% of the obtained first batch of decolorized oil is sent back to the decolorization tower, and together with the second batch of undecolorized oil to be decolorized, it is subjected to secondary decolorization under the same conditions. Then, 5 wt% of the secondary decolorized oil obtained from the secondary decolorization is sent back to the decolorization tower and subjected to tertiary decolorization with the third batch of undecolorized oil to be decolorized under the same conditions. Then, 5 wt% of the tertiary decolorized oil obtained from the tertiary decolorization is sent back to the decolorization tower and subjected to quaternary decolorization with the fourth batch of undecolorized oil to be decolorized under the same conditions. Decolorize in such a cycle until all the oil to be decolorized is decolorized, and then pump all the decolorized oil (cycle decolorized oil) obtained from the cycle decolorization into the deodorization tower;

[0087] 7. Deodorization: The primary decolorized oil and the cycle decolorized oil pumped into the deodorization tower are respectively deodorized. The system pressure is 0.2 kPa, the temperature is 235 °C, and after treatment for 2 h, deodorized oil is obtained.

[0088] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0089] Comparative Example 3

[0090] (1) Method for preparing oil:

[0091] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0092] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, degumming is carried out on the crude oil using PLA1 phospholipase. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction, the gum is separated to obtain degummed oil;

[0093] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, keep it stable for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and carry out crystallization at 20 °C for 10 hours. After crystallization, filter;

[0094] 4. Deacidification: Add an aqueous sodium hydroxide solution with the theoretical alkali amount of acid value to the dewaxed oil, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0095] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0096] 6. Decolorization: Add 3% of the oil weight of clay to the deacidified oil obtained in the previous step in the decolorization tower. React at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the first batch of decolorized oil after decolorization. 5 wt% (primary decolorized oil) of the obtained first batch of decolorized oil is directly pumped into the deodorization tower; 95 wt% of the obtained first batch of decolorized oil is sent back to the decolorization tower and undergoes secondary decolorization under the same conditions together with the second batch of undecolorized oil to be decolorized. Then, 95 wt% of the secondary decolorized oil obtained from the secondary decolorization is sent back to the decolorization tower and undergoes tertiary decolorization under the same conditions together with the third batch of undecolorized oil to be decolorized. Then, 95 wt% of the tertiary decolorized oil obtained from the tertiary decolorization is sent back to the decolorization tower and undergoes quaternary decolorization under the same conditions together with the fourth batch of undecolorized oil to be decolorized. Decolorize in this way in a cycle until all the oil to be decolorized is decolorized. Then, pump all the decolorized oil (cyclic decolorized oil) obtained from the cyclic decolorization into the deodorization tower;

[0097] 7. Deodorization: Carry out deodorization on the primary decolorized oil and the cyclic decolorized oil pumped into the deodorization tower respectively. The system pressure is 0.2 kPa, the temperature is 235 °C, and process for 2 h to obtain deodorized oil.

[0098] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0099] Comparative Example 4

[0100] (1) Method for preparing oil:

[0101] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0102] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, PLA1 phospholipase is used to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction, the gums are separated to obtain degummed oil;

[0103] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and carry out crystallization at 20 °C for 10 hours. After the crystallization is completed, filter;

[0104] 4. Deacidification: Add an aqueous sodium hydroxide solution with the theoretical alkali amount of acid value to the dewaxed oil, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap to obtain soap-free oil;

[0105] 5. Washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0106] 6. Decolorization: Add 3% of the oil weight of clay to the deacidified oil obtained in the previous step in the decolorization tower. React at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the first batch of decolorized oil after decolorization. 50 wt% (primary decolorized oil) of the obtained first batch of decolorized oil is directly pumped into the deodorization tower; 50 wt% of the obtained first batch of decolorized oil is sent back to the decolorization tower, and together with the second batch of undecolorized oil to be decolorized, it is subjected to secondary decolorization under the same conditions. Then, 50 wt% of the secondary decolorized oil obtained from the secondary decolorization is sent back to the decolorization tower and the third batch of undecolorized oil to be decolorized is subjected to tertiary decolorization under the same conditions. Then, 50 wt% of the tertiary decolorized oil obtained from the tertiary decolorization is sent back to the decolorization tower and the fourth batch of undecolorized oil to be decolorized is subjected to quaternary decolorization under the same conditions. Such cyclic decolorization is carried out until all the oil to be decolorized is decolorized. Then, all the decolorized oil (cyclic decolorized oil) obtained from the cyclic decolorization is pumped into the deodorization tower;

[0107] 7. Deodorization: The primary decolorized oil and the cyclic decolorized oil pumped into the deodorization tower are respectively deodorized. The system pressure is 0.2 kPa, the temperature is 200 °C, and after treatment for 2 h, deodorized oil is obtained.

[0108] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0109] Comparative Example 5

[0110] (1) Method for preparing oil and fat:

[0111] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0112] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, PLA1 phospholipase is used to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction, the gum is separated to obtain degummed oil;

[0113] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and crystallize at 20 °C for 10 hours. After crystallization, filter;

[0114] 4. Deacidification: Add an aqueous sodium hydroxide solution with the theoretical base amount of acid value to the dewaxed oil, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0115] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0116] 6. Decolorization: Add 3% of the oil weight of clay to the deacidified oil obtained in the previous step in the decolorization tower. React at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the first batch of decolorized oil after decolorization. 50 wt% (primary decolorized oil) of the obtained first batch of decolorized oil is directly pumped into the deodorization tower; 50 wt% of the obtained first batch of decolorized oil is sent back to the decolorization tower and subjected to secondary decolorization under the same conditions together with the second batch of undecolorized oil to be decolorized. Then, 50 wt% of the secondary decolorized oil obtained from the secondary decolorization is sent back to the decolorization tower and subjected to tertiary decolorization under the same conditions together with the third batch of undecolorized oil to be decolorized. Then, 50 wt% of the tertiary decolorized oil obtained from the tertiary decolorization is sent back to the decolorization tower and subjected to quaternary decolorization under the same conditions together with the fourth batch of undecolorized oil to be decolorized. Decolorize in this way until all the oil to be decolorized is decolorized, and then pump all the decolorized oil (circular decolorized oil) obtained from the circular decolorization into the deodorization tower;

[0117] 7. Deodorization: The primary decolorized oil and the circular decolorized oil pumped into the deodorization tower are respectively deodorized. The system pressure is 0.2 kPa, the temperature is 260 °C, and after treatment for 2 h, deodorized oil is obtained.

[0118] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0119] Comparative Example 6

[0120] (1) Method for preparing oil:

[0121] 1. Crude oil production and selection: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 4% of the mass of the crude oil.

[0122] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, PLA1 phospholipase is used to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction is completed, the gum is separated to obtain degummed oil;

[0123] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and start cooling and crystallizing. Cool down to 20 °C within 40 hours, and crystallize for 10 hours at 20 °C. After the crystallization is completed, filter.

[0124] 4. Deacidification: Add an aqueous sodium hydroxide solution with the theoretical alkali amount of acid value to the dewaxed oil, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap to obtain soap-removed oil.

[0125] 5. Water washing and drying: Add 2% soft water to the soap-removed oil, wash at 85 °C for 15 min and then centrifuge, and dry to obtain deacidified oil.

[0126] 6. Decolorization: Add 3% of clay based on the weight of the oil to the deacidified oil obtained in the previous step in the decolorization tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min, and then obtain the decolorized oil after decolorization is completed. Pump the decolorized oil into the deodorization tower;

[0127] 7. Deodorization: Deodorize the decolorized oil pumped into the deodorization tower. The system pressure is 0.2 kPa, the temperature is 260 °C, and after treatment for 2 h, deodorized oil is obtained.

[0128] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0129] Example 1

[0130] (1) Oil preparation method:

[0131] 1. Crude oil production and selection: After pressing and leaching rice bran, crude rice bran oil is obtained. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0132] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, PLA1 phospholipase is used to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction is completed, the gum is separated to obtain degummed oil;

[0133] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and start cooling and crystallizing. Cool down to 20 °C within 40 hours, and crystallize for 10 hours at 20 °C. After the crystallization is completed, filter;

[0134] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical base amount of acid value, react at 60 °C for 1 h, then centrifuge at 8000 rpm for 10 min to remove soap, and obtain the soap-removed oil;

[0135] 5. Water washing and drying: Add 2% soft water to the soap-removed oil, wash at 85 °C for 15 min and then centrifuge, and obtain the deacidified oil after drying;

[0136] 6. Decoloration: Add 3% (by weight of the oil) of clay to the deacidified oil obtained in the previous step in the decolorization tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min, and obtain the first batch of decolorized oil after decolorization. Pump 10 wt% (primary decolorized oil) of the obtained first batch of decolorized oil directly into the deodorization tower; send 90 wt% of the obtained first batch of decolorized oil back to the decolorization tower, and perform secondary decolorization on it together with the second batch of undecolorized oil to be decolorized under the same conditions. Then send 90 wt% of the secondary decolorized oil obtained from the secondary decolorization back to the decolorization tower and perform tertiary decolorization on it together with the third batch of undecolorized oil to be decolorized under the same conditions. Then send 90 wt% of the tertiary decolorized oil obtained from the tertiary decolorization back to the decolorization tower and perform quaternary decolorization on it together with the fourth batch of undecolorized oil to be decolorized under the same conditions. Decolorize in such a cycle until all the oil to be decolorized is completely decolorized, and then pump all the decolorized oil (cycle decolorized oil) obtained from the cycle decolorization into the deodorization tower.

[0137] 7. Deodorization: Perform deodorization on the primary decolorized oil and the cycle decolorized oil pumped into the deodorization tower respectively. The system pressure is 0.2 kPa, the temperature is 235 °C, and process for 2 h to obtain the deodorized oil.

[0138] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of production batches.

[0139] Example 2

[0140] (1) Oil preparation method:

[0141] 1. Crude oil extraction and selection: After pressing and leaching rice bran, obtain crude rice bran oil. The content of DG in the crude oil accounts for 4% of the mass of the crude oil.

[0142] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, use PLA1 phospholipase to degum the crude oil. The addition amount of the phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction ends, separate the gum to obtain the degummed oil;

[0143] 3. Dewaxing: Pump the degummed oil into the crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and start cooling and crystallizing. Cool down to 20 °C within 40 hours, crystallize at 20 °C for 10 hours, and filter after the crystallization ends;

[0144] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical base amount for acid value, react at 60 °C for 1 h, then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0145] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0146] 6. Bleaching: Add 3% (by weight of the oil) of clay to the deacidified oil obtained in the previous step in a bleaching tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the bleached oil after the first batch of bleaching is completed. Pump 90 wt% of the obtained first batch of bleached oil (primary bleached oil) directly into the deodorizing tower; send 10 wt% of the obtained first batch of bleached oil back to the bleaching tower, and perform secondary bleaching on it together with the second batch of unbleached oil to be bleached under the same conditions. Then send 10 wt% of the secondary bleached oil obtained from the secondary bleaching back to the bleaching tower and perform tertiary bleaching on it together with the third batch of unbleached oil to be bleached under the same conditions. Then send 10 wt% of the tertiary bleached oil obtained from the tertiary bleaching back to the bleaching tower and perform quaternary bleaching on it together with the fourth batch of unbleached oil to be bleached under the same conditions. Cycle the bleaching in this way until all the oil to be bleached is completely bleached, and then pump all the bleached oil (cyclic bleached oil) obtained from the cyclic bleaching into the deodorizing tower.

[0147] 7. Deodorization: Deodorize the primary bleached oil and the cyclic bleached oil pumped into the deodorizing tower respectively. The system pressure is 0.2 kPa, the temperature is 235 °C, and process for 2 h to obtain deodorized oil.

[0148] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of production batches.

[0149] Example 3

[0150] (1) Oil preparation method:

[0151] 1. Crude oil extraction and selection: After pressing and leaching rice bran, obtain crude rice bran oil. The content of DG in the crude oil accounts for 4% of the mass of the crude oil.

[0152] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, use PLA1 phospholipase to degum the crude oil. The addition amount of the phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction ends, separate the gum to obtain degummed oil;

[0153] 3. Dewaxing: Pump the degummed oil into a crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and conduct crystallization at 20 °C for 10 hours. After the crystallization ends, filter;

[0154] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical base amount corresponding to the acid value, react at 60 °C for 1 h, then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0155] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0156] 6. Bleaching: Add 3% (by weight of the oil) of clay to the deacidified oil obtained in the previous step in a bleaching tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min, obtaining the bleached oil after the first batch of bleaching is completed. Pump 50 wt% of the obtained first batch of bleached oil (primary bleached oil) directly into the deodorization tower; send 50 wt% of the obtained first batch of bleached oil back to the bleaching tower, and perform secondary bleaching on it together with the second batch of unbleached oil to be bleached under the same conditions. Then send 50 wt% of the secondary bleached oil obtained from the secondary bleaching back to the bleaching tower and perform tertiary bleaching on it together with the third batch of unbleached oil to be bleached under the same conditions. Then send 50 wt% of the tertiary bleached oil obtained from the tertiary bleaching back to the bleaching tower and perform quaternary bleaching on it together with the fourth batch of unbleached oil to be bleached under the same conditions. Repeat the bleaching in this way until all the oil to be bleached is completely bleached, and then pump all the bleached oil (circularly bleached oil) obtained from the circular bleaching into the deodorization tower;

[0157] 7. Deodorization: Deodorize the primary bleached oil and the circularly bleached oil pumped into the deodorization tower respectively. The system pressure is 0.2 kPa, the temperature is 235 °C, and process for 2 h to obtain deodorized oil.

[0158] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of production batches.

[0159] Example 4

[0160] (1) Method for preparing oil:

[0161] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, obtain crude rice bran oil. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0162] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, use PLA1 phospholipase to degum the crude oil. The addition amount of the phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction ends, separate the gum to obtain degummed oil;

[0163] 3. Dewaxing: Pump the degummed oil into a crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and start cooling and crystallization. Cool down to 20 °C within 40 hours, and conduct crystallization at 20 °C for 10 hours. After the crystallization ends, filter;

[0164] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical alkali amount based on the acid value, react at 60 °C for 1 h, then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-removed oil;

[0165] 5. Water washing and drying: Add 2% soft water to the soap-removed oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0166] 6. Decolorization: Add 3% of the oil weight of clay to the deacidified oil obtained in the previous step in a decolorization tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min, obtaining the decolorized oil after the first batch of decolorization is completed. Pump 50 wt% of the obtained first batch of decolorized oil (primary decolorized oil) directly into the deodorization tower; send 50 wt% of the obtained first batch of decolorized oil back to the decolorization tower, and perform secondary decolorization on it together with the second batch of undecolorized oil to be decolorized under the same conditions. Then send 50 wt% of the secondary decolorized oil obtained from the secondary decolorization back to the decolorization tower and perform tertiary decolorization on it together with the third batch of undecolorized oil to be decolorized under the same conditions. Then send 50 wt% of the tertiary decolorized oil obtained from the tertiary decolorization back to the decolorization tower and perform quaternary decolorization on it together with the fourth batch of undecolorized oil to be decolorized under the same conditions. Decolorize in this way in a cycle until all the oil to be decolorized is completely decolorized, and then pump all the decolorized oil (cyclic decolorized oil) obtained from the cyclic decolorization into the deodorization tower;

[0167] 7. Deodorization: Perform deodorization on the primary decolorized oil and the cyclic decolorized oil pumped into the deodorization tower respectively. The system pressure is 0.2 kPa, the temperature is 220 °C, and process for 2 h to obtain deodorized oil.

[0168] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0169] Example 5

[0170] (1) Method for preparing oil:

[0171] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, obtain crude rice bran oil. The content of DG in the crude oil accounts for 4% of the mass of the crude oil;

[0172] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, use PLA1 phospholipase to degum the crude oil. The addition amount of the phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction ends, separate the gum to obtain degummed oil;

[0173] 3. Dewaxing: Pump the degummed oil into a crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and start cooling and crystallization. Cool down to 20 °C within 40 hours, conduct crystallization at 20 °C for 10 hours, and filter after the crystallization ends;

[0174] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical base amount of acid value, react at 60 °C for 1 h, then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0175] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0176] 6. Decoloration: Add 3% (by weight of the oil) of clay to the deacidified oil obtained in the previous step in a decolorization tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min, obtaining the first batch of decolorized oil after decolorization is completed. Pump 50 wt% of the obtained first batch of decolorized oil (primary decolorized oil) directly into the deodorization tower; send 50 wt% of the obtained first batch of decolorized oil back to the decolorization tower, and perform secondary decolorization on it together with the second batch of undecolorized oil to be decolorized under the same conditions. Then send 50 wt% of the secondary decolorized oil obtained from the secondary decolorization back to the decolorization tower and perform tertiary decolorization on it together with the third batch of undecolorized oil to be decolorized under the same conditions. Then send 50 wt% of the tertiary decolorized oil obtained from the tertiary decolorization back to the decolorization tower and perform quaternary decolorization on it together with the fourth batch of undecolorized oil to be decolorized under the same conditions. Decolorize in this way in a cycle until all the oil to be decolorized is decolorized, and then pump all the decolorized oil (cycle decolorized oil) obtained from the cycle decolorization into the deodorization tower;

[0177] 7. Deodorization: Perform deodorization on the primary decolorized oil and the cycle decolorized oil pumped into the deodorization tower respectively, with the system pressure of 0.2 kPa and the temperature of 250 °C, and process for 2 h to obtain deodorized oil.

[0178] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0179] Example 6

[0180] (1) Method for preparing oil and fat:

[0181] 1. Preparation and selection of crude oil: After pressing and leaching rice bran, obtain crude rice bran oil. The content of DG in the crude oil accounts for 8% of the mass of the crude oil;

[0182] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, use PLA1 phospholipase to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction is completed, separate the gum to obtain degummed oil;

[0183] 3. Dewaxing: Pump the degummed oil into a crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and crystallize at 20 °C for 10 hours. After crystallization is completed, filter;

[0184] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical base amount of acid value, react at 60 °C for 1 h, then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-removed oil;

[0185] 5. Water washing and drying: Add 2% soft water to the soap-removed oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0186] 6. Decoloration: Add 3% (by weight of the oil) of clay to the deacidified oil obtained in the previous step in a decolorization tower, react at a reaction pressure of 4 kPa and 115 °C for 30 min to obtain the first batch of decolorized oil after decolorization is completed. Pump 50 wt% (primary decolorized oil) of the obtained first batch of decolorized oil directly into the deodorization tower; send 50 wt% of the obtained first batch of decolorized oil back to the decolorization tower, and perform secondary decolorization on it together with the second batch of undecolorized oil to be decolorized under the same conditions. Then send 50 wt% of the secondary decolorized oil obtained from the secondary decolorization back to the decolorization tower and perform tertiary decolorization on it together with the third batch of undecolorized oil to be decolorized under the same conditions. Then send 50 wt% of the tertiary decolorized oil obtained from the tertiary decolorization back to the decolorization tower and perform quaternary decolorization on it together with the fourth batch of undecolorized oil to be decolorized under the same conditions. Decolorize in this way in a cycle until all the oil to be decolorized is decolorized, and then pump all the decolorized oil (cycle decolorized oil) obtained from the cycle decolorization into the deodorization tower;

[0187] 7. Deodorization: Perform deodorization on the primary decolorized oil and the cycle decolorized oil pumped into the deodorization tower respectively, with the system pressure of 0.2 kPa and the temperature of 235 °C, and process for 2 h to obtain deodorized oil.

[0188] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0189] Example 7

[0190] (1) Oil preparation method:

[0191] 1. Crude oil production and selection: After pressing and leaching rice bran, obtain crude rice bran oil. The content of DG in the crude oil accounts for 5% of the mass of the crude oil;

[0192] 2. Degumming: After filtering the above-mentioned crude rice bran oil to remove solid impurities, use PLA1 phospholipase to degum the crude oil. The addition amount of phospholipase is 50 mg / kg of the mass of the crude oil, the reaction temperature is 50 °C, the reaction time is 6 h, and after the reaction ends, separate the gum to obtain degummed oil;

[0193] 3. Dewaxing: Pump the degummed oil into a crystallization tank, control the temperature to 60 °C, stabilize for 30 min, and then start cooling and crystallization. Cool down to 20 °C within 40 hours, and conduct crystallization at 20 °C for 10 hours. After crystallization ends, filter.

[0194] 4. Deacidification: Add the dewaxed oil to an aqueous sodium hydroxide solution with the theoretical base amount of acid value, react at 60 °C for 1 h, and then centrifuge at 8000 rpm for 10 min to remove soap, obtaining soap-free oil;

[0195] 5. Water washing and drying: Add 2% soft water to the soap-free oil, wash at 85 °C for 15 min and then centrifuge, and obtain deacidified oil after drying;

[0196] 6. Decolorization: Add 3% (by weight of the oil) of clay to the deacidified oil obtained in the previous step in a decolorization tower, react at a reaction pressure of 2 kPa and 120 °C for 2 h to obtain the first batch of decolorized oil after decolorization is completed. Pump 70 wt% (primary decolorized oil) of the obtained first batch of decolorized oil directly into the deodorization tower; send 30 wt% of the obtained first batch of decolorized oil back to the decolorization tower, and perform secondary decolorization on it together with the second batch of undecolorized oil to be decolorized under the same conditions. Then send 30 wt% of the secondary decolorized oil obtained from the secondary decolorization back to the decolorization tower and perform tertiary decolorization on it together with the third batch of undecolorized oil to be decolorized under the same conditions. Then send 30 wt% of the tertiary decolorized oil obtained from the tertiary decolorization back to the decolorization tower and perform quaternary decolorization on it together with the fourth batch of undecolorized oil to be decolorized under the same conditions. Decolorize in this way in a cycle until all the oil to be decolorized is decolorized, and then pump all the decolorized oil (cyclic decolorized oil) obtained from the cyclic decolorization into the deodorization tower;

[0197] 7. Deodorization: Perform deodorization on the primary decolorized oil and the cyclic decolorized oil pumped into the deodorization tower respectively. The system pressure is 0.2 kPa, the temperature is 235 °C, and process for 2 h to obtain deodorized oil.

[0198] (2) Frying experiment: Conduct the frying experiment according to the aforementioned method and record the total number of batches produced.

[0199] In each example and comparative example, the mass of the deacidified oil initially subjected to decolorization is the same, and the proportion of the cyclic decolorized oil in each cyclic decolorization is different. Detect the 3-MCPD ester content and color of the deodorized oil obtained in each example and comparative example, and conduct the frying test according to the method described above, and record the total number of batches of fried food produced. The results are shown in Table 1 below.

[0200] Table 1: Oil preparation conditions and test results

[0201]

[0202]

Claims

1. A method for deodorizing oil and fat, the method comprising deodorizing the bleached oil to be deodorized, characterized in that, The decolorized oil to be deodorized contains at least recycled decolorized oil that has been decolorized at least twice.

2. The method for deodorizing grease according to claim 1, wherein, The method has the following characteristics: The recycled decolorized oil is decolorized oil obtained by mixing decolorized oil and oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3; and / or The oil is rice oil.

3. The method according to claim 1 or 2, wherein the deodorization has one or more of the following characteristics: The pressure of the deodorization system is 0.1 - 0.5 kPa; The temperature of the deodorization system is 210 - 250 °C, such as 220 - 250 °C or 235 - 250 °C; and The time of the deodorization is 1 - 3 h.

4. A method for refining oil and fat, characterized in that, The method includes the oil deodorization method according to any one of claims 1 - 3, and one or more selected from the steps of degumming, dewaxing, deacidification, neutralization, and decolorization; preferably, the oil is rice oil.

5. The method according to claim 4, wherein The oil is crude rice bran oil with a DG content < 10%, preferably a DG content ≤ 8%.

6. The method according to claim 4, wherein The decolorization includes: mixing decolorized oil and oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3, then decolorizing to obtain recycled decolorized oil, subjecting a part of the recycled decolorized oil to deodorization, mixing the remaining part with oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3, and then decolorizing again to obtain recycled decolorized oil, and then mixing a part of the recycled decolorized oil with oil to be decolorized for re - decolorization and a part for deodorization until all the oil to be decolorized is decolorized and deodorized.

7. The method according to any one of claims 4 - 6, characterized in that The degumming includes adding a degumming medium not less than 0.05 wt% of the weight of the crude oil to the crude oil and carrying out degumming at a temperature of 45 - 80 °C; The dewaxing includes pumping the degummed oil into a crystallization tank, controlling the temperature to 50 - 70 °C, standing for 20 - 40 min, then cooling to 20 °C within 35 - 45 hours, and crystallizing at 20 °C for 5 - 15 hours, and filtering after the crystallization ends; The deacidification includes treating the dewaxed oil at a temperature of 40 - 80 °C or deacidifying by the caustic refining method; optionally, after caustic refining, it includes soap removal and drying steps; The decolorization includes adding a decolorizing agent to the oil to be decolorized, stirring for 10 min - 2 h under the conditions of 100 - 120 °C and 2 - 5 kPa, and then filtering to remove the decolorizing agent.

8. Oil processed by the method according to any one of claims 1 - 7, or an oil composition containing such oil; Preferably, the 3 - MCPD ester content of the oil is less than or equal to 4.0 mg / kg, preferably less than or equal to 2.5 mg / kg, more preferably less than or equal to 1.5 mg / kg; and / or the red color value of the oil is less than or equal to 5, preferably less than or equal to 3, more preferably less than or equal to 2.

9. A decolorized oil, characterized in that, The decolorized oil is obtained by decolorizing a mixture of decolorized oil and oil to be decolorized in a ratio of 1:9 to 9:1, such as a ratio of 1:9 to 7:3 or a ratio of 1:1 to 7:3; preferably, the decolorized oil is derived from decolorized rice oil, and the oil to be decolorized is degummed rice oil; preferably, the decolorized rice oil is derived from crude rice bran oil with a DG content < 10%, preferably a DG content ≤ 8%.

10. Use of the recycled decolorized oil according to claim 9 in reducing the content of 3-MCPD esters in oil, reducing the red value of the oil color and / or extending the number of frying times of the oil; or use of the method according to any one of claims 1 to 7 in reducing the content of 3-MCPD esters in oil, reducing the red value of the oil color and / or extending the number of frying times of the oil.

Images