CN113875825B

CN113875825B - Crystallization accelerator for inducing crystallization of rice oil and method for improving freezing resistance of rice oil

Info

Publication number: CN113875825B
Application number: CN202110814151.0A
Authority: CN
Inventors: 周帅; 孙悦; 王勇; 姜元荣; 朱振南; 刘吕睿
Original assignee: Wilmar Shanghai Biotechnology Research and Development Center Co Ltd
Current assignee: Wilmar Shanghai Biotechnology Research and Development Center Co Ltd
Priority date: 2021-07-19
Filing date: 2021-07-19
Publication date: 2023-12-19
Anticipated expiration: 2041-07-19
Also published as: CN113875825A

Abstract

The present invention provides a crystallization accelerator for inducing crystallization of rice oil and a method for improving freezing resistance of rice oil. The crystallization accelerator comprises plant sterol, plant sterol fatty acid ester and optional liquid oil, wherein the mass ratio of the plant sterol to the plant sterol fatty acid ester is 4:6-7:3. The method for improving the freezing resistance of the rice oil comprises the steps of adding the crystallization promoter into the rice oil, cooling and crystallizing the rice oil, and then carrying out solid-liquid separation. The invention also includes the use of plant sterols and plant sterol fatty acid esters and crystallization promoters described herein. According to the invention, the phytosterol and the phytosterol fatty acid ester are exogenously added to serve as the crystallization promoter, so that the crystal morphology induced by the crystallization promoter is effectively controlled, the efficiency of the crystallization promoter for inducing the crystallization of the rice oil is improved, the crystallization time for degreasing and separating the rice oil is shortened, the excellent crystal morphology is easy to separate solid from liquid, and the freezing performance of the rice oil is greatly improved.

Description

Crystallization accelerator for inducing crystallization of rice oil and method for improving freezing resistance of rice oil

Technical Field

The invention belongs to the field of foods, and particularly relates to a crystallization promoter for inducing crystallization of rice oil and a method for improving freezing resistance of the rice oil.

Background

The rice bran has rich nutrition and contains various physiological active ingredients, has the health care function, and is known as a natural nutrition treasury. The rice oil belongs to a rice bran deep processing product, has reasonable fatty acid composition, is closest to human dietary recommended standard, contains rich VE, squalene, sitosterol, ferulic acid and other components, and is internationally recognized natural green healthy oil. The data show that the long-term edible rice oil has obvious effects on preventing cardiovascular diseases, improving human immunity, regulating blood sugar and the like. Therefore, rice oil is highly favored by consumers.

The crude rice oil has deep color, high acid value, more impurities and complex components, so the refining process is complex. At present, in order to improve the freezing resistance time of rice oil, the method adopted by enterprises mainly comprises the steps of adding refining technology, such as degreasing treatment for 2-3 times, or adding a high Wen Tuose treatment method based on conventional decoloring, so that equipment and labor investment are increased, and meanwhile, the production efficiency is obviously reduced, and the productivity is reduced.

Thus, there is a need in the art for a highly efficient method of improving the freezing resistance of rice oil.

Disclosure of Invention

The invention aims to develop a degreasing method for improving the freezing resistance of rice oil, and solves the problems that the degreasing process of the rice oil has long crystal growing time (usually higher than 48 h), the degreasing oil has short freezing time at 0 ℃ and is usually about 30min, the fat crystal appearance is poor, the filtering is difficult, and the detection by a freezing experiment is difficult.

Specifically, one aspect of the present invention provides a crystallization promoter for inducing crystallization of rice oil, which comprises a plant sterol and a plant sterol fatty acid ester and optionally a liquid oil, wherein the mass ratio of the plant sterol and the plant sterol fatty acid ester is 4:6 to 7:3, preferably 5:5 to 6:4.

In one or more embodiments, the phytosterol is 4-methyl-free sterol comprising one or more of β -sitosterol, stigmasterol, campesterol, and brassicasterol.

In one or more embodiments, the plant sterol portion of the plant sterol fatty acid ester is 4-methyl free sterol comprising one or more of β -sitosterol, stigmasterol, campesterol, and brassicasterol; the fatty acid moiety of the plant sterol fatty acid ester is selected from one or more of saturated fatty acids and unsaturated fatty acids having a carbon number of 12 to 24, preferably 16 to 24, preferably from one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, behenic acid, erucic acid and tetracosenic acid.

In one or more embodiments, the liquid oil is a liquid vegetable oil, preferably one or any mixture of oils of rice oil, sunflower seed oil, palm kernel oil, peanut oil, rapeseed oil, cottonseed oil, safflower oil, perilla seed oil, tea seed oil, palm fruit oil, coconut oil, olive oil, cocoa butter, tallow seed oil, almond oil, tung seed oil, rubber seed oil, rice bran oil, corn germ oil, wheat germ oil, sesame seed oil, castor seed oil, linseed oil, evening primrose seed oil, hazelnut oil, walnut oil, grape seed oil, linseed oil, borage seed oil, sea buckthorn seed oil, tomato seed oil, pumpkin seed oil, macadamia nut oil, cocoa butter, and algae oil.

In one or more embodiments, the plant sterols comprise β -sitosterol, optionally further comprising one or more of stigmasterol, campesterol, and brassicasterol; preferably, the plant sterols comprise beta-sitosterol, stigmasterol, campesterol and brassicasterol; preferably, the mass fraction of beta-sitosterol is greater than or equal to 35%, preferably greater than or equal to 40%, more preferably greater than or equal to 42% based on the total weight of the phytosterols.

In one or more embodiments, the plant sterol portion of the plant sterol fatty acid ester comprises β -sitosterol, optionally further comprising one or more of stigmasterol, campesterol, and brassicasterol; preferably, the plant sterol fraction comprises β -sitosterol, stigmasterol, campesterol and brassicasterol; preferably, the mass fraction of beta-sitosterol is greater than or equal to 35%, preferably greater than or equal to 40%, more preferably greater than or equal to 42%, based on the total weight of the phytosterol portion of the phytosterol fatty acid ester; preferably, the mass fraction of the phytosterol fraction is greater than or equal to 50%, preferably greater than or equal to 58%, more preferably greater than or equal to 60%, based on the total weight of the phytosterol fatty acid ester.

In one or more embodiments, the plant sterols contain beta-sitosterol, stigmasterol, campesterol and brassicasterol in a total mass fraction of 80% or more, preferably 85% or more, more preferably 90% or more, more preferably 95% or more, and the beta-sitosterol is 35% or more, preferably 40% or more, more preferably 42% or more, based on the total weight of the plant sterols; the plant sterol part of the plant sterol fatty acid ester comprises beta-sitosterol, stigmasterol, campesterol and brassicasterol, and the total mass fraction of beta-sitosterol, stigmasterol, campesterol and brassicasterol in the plant sterol part of the plant sterol fatty acid ester is equal to or more than 80%, preferably equal to or more than 85%, more preferably equal to or more than 90%, more preferably equal to or more than 95%, and the mass fraction of beta-sitosterol is equal to or more than 35%, preferably equal to or more than 40%, more preferably equal to or more than 60%, more preferably equal to or more than 70%; the fatty acid moiety of the fatty acid esters of phytosterols is palmitic acid, stearic acid, oleic acid, linoleic acid and tetracosenoic acid.

In one or more embodiments, the plant sterol is β -sitosterol and the plant sterol fatty acid ester is β -sitosterol oleate.

In another aspect, the invention provides a method for improving the freezing resistance or degreasing of rice oil, which is characterized in that the method comprises the steps of adding the crystallization promoter according to any embodiment of the invention into the rice oil, cooling and crystallizing the rice oil, and then carrying out solid-liquid separation.

In one or more embodiments, the ratio of the total mass of plant sterols and plant sterol fatty acid esters to the mass of rice oil in the crystallization promoter is not less than 2:98, preferably 2:98 to 10:90, more preferably 3:97 to 6:94, such as about 4:96.

In one or more embodiments, the rice oil is selected from the group consisting of degummed rice oil, dewaxed rice oil, deacidified rice oil, decolorized rice oil, and deodorized rice oil.

In one or more embodiments, the crystallization promoter is added to the rice oil at 45 to 90 ℃, preferably 45 to 60 ℃.

In one or more embodiments, the total time of the cooling down procedure does not exceed 48 hours, preferably does not exceed 36 hours, such as 25 to 36 hours.

In one or more embodiments, the end temperature of the cool down procedure is between 0 and 3 ℃.

In one or more embodiments, the rice oil crystals form crystals having a sea urchin-like morphology and an average crystal size of 80 μm or more.

In one or more embodiments, the mass ratio of the plant sterol and the plant sterol fatty acid ester is from 5:5 to 6:4, and the mass ratio of the total mass of the plant sterol and the plant sterol fatty acid ester in the crystallization promoter to the rice oil is from 3:97 to 6:94.

In one or more embodiments, the cooling crystallization sequentially comprises: the rice oil added with the crystallization promoter is cooled from 45 ℃ to 90 ℃, preferably 45 ℃ to 60 ℃ to 23 ℃ to 28 ℃ at a cooling rate of 3 ℃ to 4 ℃/h, then cooled to 18 ℃ to 22 ℃ at a cooling rate of 2 ℃ to 3 ℃/h, then cooled to 5 ℃ to 10 ℃ at a cooling rate of 0.5 ℃ to 1.5 ℃/h and kept at a constant temperature for 2 to 4 hours, and then cooled to 0 ℃ to 3 ℃ at a cooling rate of 0.5 ℃ to 1.5 ℃/h.

In one or more embodiments, the solid-liquid separation is performed by centrifugation, filtration; preferably, the centrifugal temperature is 0-5 ℃, the centrifugal time is 20-40 min, and the centrifugal rotating speed is 6000-10000 r/min.

The invention also provides rice oil prepared by adopting any one of the methods; preferably, the rice oil has a freezing time of 72 minutes or more as measured according to GB/T17756 standard.

The invention also provides for a use selected from the group consisting of:

(1) The crystallization promoter disclosed by any embodiment of the invention is applied to degreasing of rice oil to improve the freezing resistance of the rice oil;

(2) The use of the crystallization promoter according to any one of the embodiments of the present invention in the preparation of a reagent for degreasing rice oil to improve the freezing resistance of the rice oil;

(3) The application of the plant sterol and the plant sterol fatty acid ester in degreasing rice oil to improve the freezing resistance of the rice oil or in preparing a crystallization promoter for degreasing the rice oil to improve the freezing resistance of the rice oil; preferably, the mass ratio of the plant sterol to the plant sterol fatty acid ester is 4:6-7:3, preferably 5:5-6:4; preferably, the plant sterols and plant sterol fatty acid esters are as described in any embodiment of the invention.

Drawings

FIG. 1 is a polarized light micrograph of the crystal morphology of the examples and comparative examples.

Detailed Description

So that those skilled in the art can appreciate the features and effects of the present invention, a general description and definition of the terms and expressions set forth in the specification and claims follows. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, and in the event of a conflict, the present specification shall control.

The theory or mechanism described and disclosed herein, whether right or wrong, is not meant to limit the scope of the invention in any way, i.e., the present disclosure may be practiced without limitation to any particular theory or mechanism.

Herein, "comprising," "including," "having," "containing," and similar terms are intended to cover the meaning of "consisting essentially of … …" and "consisting of … …," e.g., where "a comprises B and C" is disclosed herein, it is to be considered that "a consists of B and C" has been disclosed herein.

In this document, all features such as values, amounts, and concentrations that are defined as ranges of values or percentages are for brevity and convenience only. Accordingly, the description of a numerical range or percentage range should be considered to cover and specifically disclose all possible sub-ranges and individual values (including integers and fractions) within the range.

Herein, when embodiments or examples are described, it should be understood that they are not intended to limit the invention to these embodiments or examples. On the contrary, all alternatives, modifications, and equivalents of the methods and materials described herein are intended to be included within the scope of the invention as defined by the appended claims.

The sum of the percentages of the components is equal to 100%.

In this context, not all possible combinations of the individual technical features in the individual embodiments or examples are described in order to simplify the description. Accordingly, as long as there is no contradiction between the combinations of these technical features, any combination of the technical features in the respective embodiments or examples is possible, and all possible combinations should be considered as being within the scope of the present specification.

The invention aims to improve the freezing resistance of rice oil. The invention discovers that the combination of plant sterol and plant sterol fatty acid ester which is beneficial to human body is used as the crystallization promoter, so that the crystal morphology induced by the crystallization promoter can be effectively controlled, the efficiency of the crystallization promoter for inducing the crystallization of rice oil is further improved, the degreasing cooling time is shortened, the solid-liquid separation is easy, and the freezing performance of the rice oil can be greatly improved.

Herein, the crystallization promoter, after being added to rice oil, induces formation and growth of crystals in the rice oil as seed crystals. The seed crystal refers to an additive that can form a crystal nucleus in a crystallization method to accelerate or promote the growth of crystals.

The crystallization promoter of the present invention comprises a plant sterol and a plant sterol fatty acid ester, and optionally a liquid oil, wherein the mass ratio of plant sterol to plant sterol fatty acid ester is from 4:6 to 7:3, such as 5:5, 6:4. In some embodiments, the crystallization promoter of the present invention has a mass ratio of plant sterols to plant sterol fatty acid esters of from 5:5 to 6:4. In some embodiments, the crystallization promoters of the present invention consist of plant sterols and plant sterol fatty acid esters. In some embodiments, the crystallization promoter of the present invention is a mixture of a phytosterol and a fatty acid ester of a phytosterol.

Phytosterol is a compound which is widely existing in plants, takes cyclopentane perhydro phenanthrene as a framework and contains alcohol groups. Phytosterols can be classified into 4-methyl-free sterols, 4-methyl sterols and 4,4' -dimethyl sterols. The 4-methyl-free sterols mainly comprise beta-sitosterol, stigmasterol, campesterol and brassicasterol. In some embodiments, the phytosterols suitable for use in the crystallization promoters of the present invention are 4-methyl-free sterols including, but not limited to, one or more selected from the group consisting of beta-sitosterol, stigmasterol, campesterol, and brassicasterol.

The fatty acid esters of phytosterols suitable for use in the crystallization promoter of the present invention are the esterification products of phytosterols and fatty acids. Suitable phytosterol moieties are as described hereinbefore and include 4-methyl-free sterols, 4-methyl sterols and 4,4' -dimethyl sterols, preferably 4-methyl-free sterols, more preferably including but not limited to one or more selected from the group consisting of beta-sitosterol, stigmasterol, campesterol and brassicasterol. Suitable fatty acids are selected from one or more of saturated and unsaturated fatty acids having carbon numbers of 12 to 24, preferably 16 to 24, and include, for example, but are not limited to, one or more selected from lauric acid (C12:0), myristic acid (C14:0), palmitic acid (C16:0), stearic acid (C18:0), oleic acid (C18:1), linoleic acid (C18:2), behenic acid (C22:0), erucic acid (C22:1), and tetracosenoic acid (C24:1). In some embodiments, the fatty acid is preferably one or more of palmitic acid, stearic acid, oleic acid, linoleic acid, and tetracosenoic acid.

The crystallization promoter of the present invention may optionally contain a liquid oil. Various edible liquid oils known in the art may be used in the present invention including, but not limited to, any of a variety of vegetable oils such as rice oil, sunflower oil, palm kernel oil, peanut oil, canola oil, cottonseed oil, safflower oil, perilla seed oil, tea seed oil, palm fruit oil, coconut oil, olive oil, cocoa butter oil, tallow seed oil, almond oil, tung seed oil, rubber seed oil, rice bran oil, corn germ oil, wheat germ oil, sesame seed oil, castor seed oil, linseed oil, evening primrose seed oil, hazelnut oil, walnut oil, grape seed oil, linseed oil, glass chicory seed oil, sea buckthorn seed oil, tomato seed oil, pumpkin seed oil, macadamia nut oil, cocoa butter, and an oil mixture of any two or more of the oils. The liquid oil is used herein to previously dissolve the plant sterol and plant sterol fatty acid ester, and thus, when it is contained in the crystallization accelerator, the specific amount of the liquid oil is not particularly limited as long as it can sufficiently dissolve the plant sterol and plant sterol fatty acid ester. The preferred liquid oil is rice oil.

In some embodiments, the phytosterols in the crystallization promoters of the present invention comprise β -sitosterol. In some embodiments, the mass fraction of beta-sitosterol in the phytosterols in the crystallization promoter of the present invention is greater than or equal to 35%, such as greater than or equal to 40%, greater than or equal to 42%. In some embodiments, the phytosterols in the crystallization promoter of the present invention comprise β -sitosterol, optionally further comprising one or more of stigmasterol, campesterol, and brassicasterol. In some embodiments, the total mass fraction of β -sitosterol and one or more of stigmasterol, campesterol, and brassicasterol optionally included in the phytosterols in the crystallization promoter of the present invention is greater than or equal to 80%, such as greater than or equal to 85%, greaterthan or equal to 90%, greaterthan or equal to 95%. In some embodiments, the phytosterols in the crystallization accelerator of the present invention comprise β -sitosterol, stigmasterol, campesterol, and brassicasterol. In some embodiments, the phytosterol in the crystallization promoter of the present invention is beta-sitosterol. Phytosterols suitable for use in the present invention are commercially available.

In some embodiments, the plant sterol portion of the plant sterol fatty acid ester in the crystallization promoter of the present invention comprises β -sitosterol. In some embodiments, the mass fraction of beta-sitosterol in the plant sterol fraction of the plant sterol fatty acid ester in the crystallization promoter of the present invention is no less than 35%, such as no less than 40%, noless than 42%, noless than 60%, no less than 70%. In some embodiments, the plant sterol portion of the plant sterol fatty acid ester in the crystallization promoter of the present invention comprises β -sitosterol, optionally further comprising one or more of stigmasterol, campesterol, and brassicasterol. Preferably, the total mass fraction of β -sitosterol and optionally one or more of stigmasterol, campesterol and brassicasterol in the plant sterol portion of the plant sterol fatty acid ester in the crystallization promoter of the present invention is ≡80%, for example ≡85%,. Gtoreq.90%,. Gtoreq.95%. In some embodiments, the plant sterol portion of the plant sterol fatty acid esters in the crystallization accelerator of the present invention contains β -sitosterol, stigmasterol, campesterol, and brassicasterol. In some embodiments, the plant sterol portion of the plant sterol fatty acid ester in the crystallization promoter of the present invention is β -sitosterol.

In some embodiments, the phytosterols in the phytosterol fatty acid esters of the present invention are β -sitosterol, stigmasterol, campesterol, and brassicasterol, and the fatty acids are palmitic acid, stearic acid, oleic acid, linoleic acid, and tetracosenoic acid.

Preferably, in the plant sterol fatty acid ester of the present invention, the mass fraction of plant sterols is not less than 50%, preferably not less than 58%, more preferably not less than 60% based on the total weight of the plant sterol fatty acid ester.

The plant sterol fatty acid esters suitable for use in the present invention are commercially available and can also be prepared by methods known in the art, for example, by methods reported in the literature as "enzymatic synthesis of plant sterol esters" ("chemical Engineers", 2016, 30 (9): 4-9).

In some embodiments, the phytosterol fatty acid esters are prepared using the following method: the esterification of phytosterols with fatty acids is carried out using a lipase, such as candida cylindracea lipase, as a catalyst and a liquid alkane, such as n-hexane, as a reaction medium. The molar ratio of the phytosterol to the fatty acid may be from 1:1 to 5:1. The lipase may be added in an amount of 5 to 10wt%. The reaction temperature may be 25 to 60 ℃, for example 40 to 50 ℃. The reaction time may be 12 to 36 hours, for example 20 to 30 hours.

In some embodiments, the fatty acid portion of the plant sterol fatty acid esters in the crystallization promoter of the present invention comprises one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, behenic acid, erucic acid, tetracosenoic acid. In some embodiments, the fatty acid moiety of the plant sterol fatty acid ester in the crystallization promoter of the present invention is oleic acid.

In some embodiments, the crystallization promoters of the present invention comprise plant sterols and plant sterol fatty acid esters in a mass ratio of 4:6 to 7:3 (e.g., 5:5, 6:4), wherein the plant sterols contain β -sitosterol, stigmasterol, campesterol, and brassicasterol, and the total mass fraction of β -sitosterol, stigmasterol, campesterol, and brassicasterol in the plant sterols is greater than or equal to 80%, e.g., greater than or equal to 85%, greaterthan or equal to 90%, greaterthan or equal to 95%, the mass fraction of β -sitosterol is greater than or equal to 35%, e.g., greater than or equal to 40%, greaterthan or equal to 42%; the plant sterol part of the plant sterol fatty acid ester comprises beta-sitosterol, stigmasterol, campesterol and brassicasterol, and the total mass fraction of beta-sitosterol, stigmasterol, campesterol and brassicasterol in the plant sterol part of the plant sterol fatty acid ester is equal to or more than 80%, such as equal to or more than 85%, equal to or more than 90%, equal to or more than 95%, and the mass fraction of beta-sitosterol is equal to or more than 35%, such as equal to or more than 40%, equal to or more than 60%, and equal to or more than 70%; the fatty acid moiety of the plant sterol fatty acid ester is a saturated fatty acid and an unsaturated fatty acid having 12 to 24 carbon atoms, preferably 16 to 24 carbon atoms, more preferably, the fatty acid is palmitic acid, stearic acid, oleic acid, linoleic acid, and tetracosenoic acid.

In some embodiments, the crystallization promoters of the present invention comprise a plant sterol and a plant sterol fatty acid ester in a mass ratio of from 4:6 to 7:3 (e.g., 5:5, 6:4), wherein the plant sterol is β -sitosterol and the plant sterol fatty acid ester is β -sitosterol oleate.

The rice oil degreasing method or the method for improving the freezing resistance of the rice oil comprises the steps of adding the crystallization promoter into the rice oil, and cooling and crystallizing the rice oil.

The rice oil suitable for the present invention may be rice oil obtained at any processing section in the processing of rice oil, including degummed rice oil, dewaxed rice oil, deacidified rice oil, decolorized rice oil and deodorized rice oil. In some embodiments, the present invention uses deodorized rice oil obtained by degumming, dewaxing, deacidifying, decolorizing and deodorizing.

In the method of the present invention, the mass ratio of the crystallization promoter to the rice oil is not less than 2:98, for example, 2:98 to 4:96, 3:97. In some embodiments, the mass ratio of crystallization promoter to rice oil is from 2:98 to 10:90. The total time of crystal growth (cooling procedure) of the method of the invention is not more than 48 hours, for example, 25-48 hours, 30-48 hours, preferably not more than 36 hours, for example, 25-36 hours, 25-34 hours, 30-34 hours, and the time is obviously shortened compared with the conventional method. The end temperature of the crystal growth can be 0-3 ℃. The shape of the crystal formed by the crystallization of the rice oil is sea urchin-shaped, the average crystal size is more than or equal to 80 mu m, and the solid-liquid separation is easy.

In some embodiments, the crystallization promoter of the present invention is added to rice oil at 45 to 90 ℃, preferably 45 to 60 ℃, more preferably 50 to 55 ℃. The crystallization promoter may be added under stirring, and the stirring rate may be 10 to 50rpm. After the addition of the crystallization promoter, the temperature may be maintained for a period of time, for example, 10 to 30 minutes, for example, 20.+ -. 5 minutes, to eliminate residual crystals and thermal history. The rice oil added with the crystallization promoter may be cooled from 45 to 90℃, for example, 50 to 55℃, to 23 to 28℃, for example, 25 to 28℃ at a cooling rate of 3 to 4℃/h, then to 18 to 22℃, for example, 20 to 22℃ at a cooling rate of 2 to 3℃/h, then to 5 to 10℃, for example, 7 to 10℃ at a cooling rate of 0.5 to 1.5C/h and kept at a constant temperature for 2 to 4 hours, for example, 3.+ -. 0.5 hours, and then to 0 to 3℃ at a cooling rate of 0.5 to 1.5C/h. The total time of the cooling procedure is controlled to be not more than 48 hours, for example, 25-48 hours.

In some embodiments, the rice oil added with the crystallization promoter is cooled from 45 to 90 ℃, preferably 45 to 60 ℃, more preferably 50 to 55 ℃ to 23 to 28 ℃, such as 25 to 28 ℃, at a cooling rate of 3 to 4 ℃/h, such as 3.125 ℃/h, then to 18 to 22 ℃, such as 20 to 22 ℃, at a cooling rate of 2 to 3 ℃/h, such as 2.5 ℃/h, then to 5 to 10 ℃, such as 7 to 10 ℃ and kept at a constant temperature for 2 to 4 hours, such as 3±0.5 hours, then to 0 to 3 ℃ at a cooling rate of 0.5 to 1.5 ℃/h, such as 1 ℃/h, and the total time of seeding is controlled to be not more than 36 hours, such as 25 to 36 hours, 30 to 34 hours.

In general, in the cooling procedure of the present invention, the cooling rate of the first cooling is higher than the cooling rate of the second cooling, and the cooling rates of the third cooling and the fourth cooling may be the same or different, but are both lower than the cooling rate of the second cooling.

The crystallization promoter may be dissolved with a small amount of rice oil to obtain a rice oil mother liquor, and then the mother liquor may be added to the remaining rice oil.

And after the cooling procedure is finished, carrying out solid-liquid separation, and obtaining clear liquid which is the defatted rice oil product with excellent freezing resistance. The solid-liquid separation can be carried out by centrifugation and filtration, the centrifugation temperature is not higher than 5 ℃, for example, 0-5 ℃, the centrifugation time can be 20-40 min, and the centrifugation rotating speed can be 6000-10000 revolutions per minute. In some embodiments, after the end of seeding, the cells are centrifuged at 8000.+ -. 500 rpm at 4.+ -. 0.5 ℃ for 30.+ -. 5 min.

The rice oil defatted by the method has excellent freezing resistance, the freezing time measured according to GB/T17756 standard can reach more than 72 minutes, for example, 72-1200 minutes, and compared with the freezing time of the defatted rice oil obtained by the conventional method, the freezing time of the defatted rice oil is obviously improved.

The invention has the following beneficial effects: according to the invention, the phytosterol and the phytosterol fatty acid ester contained in the rice oil are exogenously added to serve as the crystallization promoter, so that the crystallization induced by the crystallization promoter is effectively controlled to be sea urchin-shaped crystals with the average size of more than or equal to 80 mu m, and the efficiency of the crystallization promoter in inducing the crystallization of the rice oil is improved. Compared with the conventional method, the invention selects plant sterol and plant sterol fatty acid ester which are beneficial to human bodies as crystallization promoter, shortens degreasing and crystal growing time (for example, can be shortened to 30-48 h), ensures that sea urchin-shaped crystals with average size of more than or equal to 80 mu m are easy to separate solid from liquid, ensures long freezing time of degreased rice oil, and greatly improves freezing performance of the rice oil.

The invention will be illustrated by way of specific examples. It should be understood that these examples are illustrative only and are not intended to limit the scope of the invention. The methods, reagents and materials used in the examples and comparative examples are those conventional in the art unless otherwise specified. The materials in both examples and comparative examples are commercially available.

The following raw materials were used in the examples and comparative examples:

raw material rice oil: the rice oil subjected to degumming, dewaxing, deacidification, decolorization and deodorization is purchased from Qin Royal gold sea food industry Co., ltd;

phytosterol 1: the model PS-95, which is purchased from Valley Biotechnology (Jiangsu) Inc. of Feng Yichun, contains beta-sitosterol, stigmasterol, campesterol and brassicasterol, wherein the total mass fraction of beta-sitosterol, stigmasterol, campesterol and brassicasterol is 95% and the mass fraction of beta-sitosterol is 42%.

Phytosterol ester 1: the plant sterol part of the plant sterol ester contains beta-sitosterol, stigmasterol, campesterol and brassicasterol, wherein the total mass fraction of the beta-sitosterol, stigmasterol, campesterol and brassicasterol is more than or equal to 90%, and the mass fraction of the beta-sitosterol is 70-80%; the fatty acid part of the plant sterol ester is saturated fatty acid and unsaturated fatty acid with 12-24 carbon atoms.

Phytosterol 2: beta-sitosterol was purchased from Shanghai Taitan technologies Co.

Phytosterol ester 2: beta-sitosterol oleate synthesized by literature' enzymatic method of phytosterol ester]The chemical engineer, 2016,30 (9): methods reported by 4-9 "laboratory syntheses, the specific synthetic methods are: the molar ratio of beta-sitosterol (purchased from Shanghai Taitan technology Co., ltd.) to oleic acid (purchased from Shanghai Taitan technology Co., ltd.) is 3:1, the adding amount of candida cylindracea lipase is 7.2%, and the reaction medium is 150 r.min ^-1 The reaction is carried out in an air bath oscillator (shaking table) at the temperature of 45.3 ℃ for 25.3 hours to obtain the beta-sitosterol oleate.

Liquid vegetable oil 1: sunflower seed oil is purchased from Goldfish grain and oil food Co., ltd.

Liquid vegetable oil 2: soybean oil purchased from goldfish grain and oil food stock, inc.

The following experimental methods were used in the examples and comparative examples:

(1) Freezing experiment: the GB/T17756 standard is adopted. The specific operation method comprises the following steps: the heating was stopped immediately when the oil sample (200-300 mL) was heated to 130℃and filtered while hot. The filtered oil was poured into an oil sample bottle, stoppered with a cork, cooled to 25 ℃, and capped with paraffin. Then immersing the oil sample bottle into an ice water bath at 0 ℃, starting timing, keeping the ice water bath at 0 ℃, and recording the turbidity time of the oil sample.

(2) Crystal morphology: and observing the crystal morphology at the end of crystal growth by adopting a polarizing microscope.

Comparative example 1

Heating raw material rice oil to 40 ℃, cooling the oil to 20 ℃ at a cooling rate of 2.5 ℃/h, growing crystals at 20 ℃ for 20 hours, then continuously cooling the oil to 3 ℃ at 1.7 ℃/h, growing crystals at 3 ℃ for 22 hours, wherein the total time of growing crystals is 60 hours, and the end temperature of growing crystals is 3 ℃. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Comparative example 2

In comparative example 2, the crystallization promoter was phytosterol 1.

The addition amount of the crystallization accelerator: the mass ratio of the phytosterol 1 to the rice oil is 4:96.

The raw rice oil was warmed to 50℃at a stirring rate of 10rpm, and a rice oil mother liquor containing a crystallization promoter was added to the raw rice oil and kept at the temperature for 20 minutes to eliminate residual crystals and heat history. And (3) cooling the raw material rice oil added with the crystallization accelerator from 50 ℃ to 25 ℃ at a cooling rate of 3.125 ℃/h, cooling to 20 ℃ at a cooling rate of 2.5 ℃/h, cooling to 7 ℃ at a cooling rate of 1 ℃/h, keeping the temperature for 3h, and cooling to 3 ℃ at a cooling rate of 1 ℃/h, wherein the total crystal growing time is 30h. When the temperature is reduced to be lower than 5 ℃, the rice oil is gel-like, and solid-liquid separation and subsequent freezing experiments cannot be performed. The crystal morphology at the end of crystal growth is shown in figure 1.

Comparative example 3

In comparative example 3, the crystallization promoter was phytosterol 1.

The addition amount of the crystallization accelerator: the mass ratio of the phytosterol 1 to the rice oil is 2:98.

The raw rice oil was warmed to 50℃at a stirring rate of 10rpm, and a rice oil mother liquor containing a crystallization promoter was added to the raw rice oil and kept at the temperature for 20 minutes to eliminate residual crystals and heat history. And (3) cooling the raw material rice oil added with the crystallization accelerator from 50 ℃ to 25 ℃ at a cooling rate of 3.125 ℃/h, cooling to 20 ℃ at a cooling rate of 2.5 ℃/h, cooling to 7 ℃ at a cooling rate of 1 ℃/h, keeping the temperature for 3h, and cooling to 3 ℃ at a cooling rate of 1 ℃/h, wherein the total crystal growing time is 30h. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Comparative example 4

In comparative example 4, the crystallization promoter was phytosterol ester 1.

The addition amount of the crystallization accelerator: the mass ratio of the plant sterol ester 1 to the rice oil is 4:96.

Comparative example 5

The raw rice oil was warmed to 50℃under a stirring rate of 10rpm and kept at a constant temperature for 20 minutes to eliminate residual crystals and heat history. The raw material rice oil is cooled to 25 ℃ from 50 ℃ at a cooling rate of 3.125 ℃/h, then cooled to 20 ℃ at a cooling rate of 2.5 ℃/h, then cooled to 7 ℃ at a cooling rate of 1 ℃/h and kept at a constant temperature for 3h, and then cooled to 3 ℃ at a cooling rate of 1 ℃/h, and the total crystal growing time is 30h. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Example 1

In example 1, the crystallization promoter was a mixture of phytosterol 1 and phytosterol ester 1, the mass ratio of phytosterol 1 to phytosterol ester 1 was 5:5.

The addition amount of the crystallization accelerator: the mass ratio of the crystallization promoter to the rice oil is 4:96.

Example 2

In example 2, the crystallization promoter was a mixture of phytosterol 1 and phytosterol ester 1, the mass ratio of phytosterol 1 to phytosterol ester 1 was 5:5.

The raw rice oil was warmed to 50℃at a stirring rate of 10rpm, and a rice oil mother liquor containing a crystallization promoter was added to the raw rice oil and kept at the temperature for 20 minutes to eliminate residual crystals and heat history. The raw material rice oil added with the crystallization accelerator is cooled to 25 ℃ from 50 ℃ at a cooling rate of 3.125 ℃/h, then cooled to 20 ℃ at a cooling rate of 2.5 ℃/h, then cooled to 7 ℃ at a cooling rate of 1 ℃/h and kept at a constant temperature for 3 hours, and then cooled to 0 ℃ at a cooling rate of 1 ℃/h, wherein the total crystal growing time is 33 hours. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Example 3

In example 3, the crystallization promoter was a mixture of phytosterol 1 and phytosterol ester 1, the mass ratio of phytosterol 1 to phytosterol ester 1 was 5:5.

The addition amount of the crystallization accelerator: the mass ratio of the crystallization promoter to the rice oil is 2:98.

Example 4

In example 4, the crystallization promoter was a mixture of plant sterol 1, plant sterol ester 1 and liquid plant oil 1, the mass ratio of plant sterol 1 to plant sterol ester 1 was 7:3, and the mass ratio of liquid plant oil 1 to total sterols (sum of plant sterol 1 and plant sterol ester 1) was 5:1.

The addition amount of the crystallization accelerator: the mass ratio of total sterols (sum of phytosterol 1 and phytosterol ester 1) fraction to rice oil in the crystallization accelerator was 3:97.

The raw rice oil was warmed to 50℃at a stirring rate of 10rpm, and a crystallization promoter containing liquid vegetable oil 1 was added to the raw rice oil and kept at a constant temperature for 20 minutes to eliminate residual crystals and heat history. And (3) cooling the raw material rice oil added with the crystallization accelerator from 50 ℃ to 25 ℃ at a cooling rate of 3.125 ℃/h, cooling to 20 ℃ at a cooling rate of 2.5 ℃/h, cooling to 7 ℃ at a cooling rate of 1 ℃/h, keeping the temperature for 3h, and cooling to 3 ℃ at a cooling rate of 1 ℃/h, wherein the total crystal growing time is 30h. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Example 5

In example 5, the crystallization promoter was a mixture of phytosterol 2 and phytosterol ester 2, the mass ratio of phytosterol 2 to phytosterol ester 2 was 6:4.

The raw rice oil was warmed to 50℃at a stirring rate of 10rpm, and a rice oil mother liquor containing a crystallization promoter was added to the raw rice oil and kept at the temperature for 20 minutes to eliminate residual crystals and heat history. The raw material rice oil added with the crystallization accelerator is cooled to 25 ℃ from 50 ℃ at a cooling rate of 3 ℃/h, then cooled to 20 ℃ at a cooling rate of 2 ℃/h, then cooled to 7 ℃ at a cooling rate of 0.5 ℃/h and kept at a constant temperature for 3h, and then cooled to 3 ℃ at a cooling rate of 0.5 ℃/h, and the total crystal growing time is 47.8h. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Example 6

In example 6, the crystallization promoter was a mixture of plant sterol 2, plant sterol ester 2 and liquid plant oil 2, the mass ratio of plant sterol 2 to plant sterol ester 2 was 4:6, and the mass ratio of liquid plant oil 2 to total sterols (sum of plant sterol 2 and plant sterol ester 2) was 4:1.

The addition amount of the crystallization accelerator: the mass ratio of total sterols (sum of phytosterol 2 and phytosterol ester 2) fraction to rice oil in the crystallization accelerator was 4:96.

The raw rice oil was warmed to 55℃at a stirring rate of 10rpm, and a crystallization promoter containing liquid vegetable oil 2 was added to the raw rice oil and kept at a constant temperature for 20 minutes to eliminate residual crystals and heat history. The raw material rice oil added with the crystallization accelerator is cooled to 28 ℃ from 55 ℃ at a cooling rate of 4 ℃/h, then cooled to 22 ℃ at a cooling rate of 3 ℃/h, then cooled to 10 ℃ at a cooling rate of 1.5 ℃/h and kept at a constant temperature for 3h, and then cooled to 3 ℃ at a cooling rate of 0.5 ℃/h, wherein the total crystal growing time is 33.7h. After the crystal growth is finished, centrifuging for 30min at 4 ℃, wherein the centrifugal speed is 8000 rpm, filtering after the centrifugation is finished, and taking supernatant rice oil for a freezing experiment. The freezing experiment results are shown in table 1, and the crystal morphology at the end of crystal growth is shown in fig. 1.

Table 1: results of the freezing experiments

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Note that: in comparative example 2, when the temperature is lowered below 5 ℃, the rice oil is in a gel state, and solid-liquid separation and subsequent freezing experiments cannot be performed.

As can be seen from Table 1, the rice oil is subjected to cooling crystallization by using the plant sterol and the plant sterol fatty acid ester as crystallization promoters by adopting the method disclosed by the invention, sea urchin-shaped crystals with average crystal size more than or equal to 80 mu m can be induced to be formed, solid-liquid separation is easy, the rice oil obtained after the solid-liquid separation has excellent freezing resistance, the freezing time at 0 ℃ can reach more than 70 hours, the crystal growing time is short, and the degreasing efficiency is obviously improved.

The defatted rice oil obtained in comparative example 1 was frozen at 0℃for a time similar to that of example 2, but since the crystallization accelerator of the present invention was not used, the crystallization time was far longer than that of example 2, and the crystals formed were small-particle crystals having an average crystal size of < 5. Mu.m, and solid-liquid separation was not easy. Comparative examples 3 to 4 use only phytosterol or phytosterol fatty acid ester as crystallization promoter, and the obtained defatted rice oil was poor in freezing resistance. The crystallization time of comparative example 5 was the same as that of examples 1, 3 and 4, but since the crystallization accelerator of the present invention was not used, the freezing resistance of the defatted rice oil obtained was significantly inferior to that of examples 1, 3 and 4.

Claims

1. A crystallization promoter for inducing crystallization of rice oil, characterized in that the crystallization promoter comprises plant sterols, plant sterol fatty acid esters and optionally liquid oil, wherein the mass ratio of the plant sterols to the plant sterol fatty acid esters is 4:6-7:3; the plant sterol comprises beta-sitosterol, and the mass fraction of the beta-sitosterol is more than or equal to 35% based on the total weight of the plant sterol; the plant sterol part of the plant sterol fatty acid ester comprises beta-sitosterol, and the mass fraction of the beta-sitosterol is more than or equal to 35 percent based on the total weight of the plant sterol part of the plant sterol fatty acid ester.

2. The crystallization accelerator according to claim 1, wherein the mass ratio of the plant sterol to the plant sterol fatty acid ester is 5:5 to 6:4.

3. The crystallization accelerator according to claim 1, wherein,

the plant sterol is 4-methyl-free sterol, and further comprises one or more of stigmasterol, campesterol and brassicasterol; and/or

The plant sterol part of the plant sterol fatty acid ester is 4-methyl-free sterol, and further comprises one or more of stigmasterol, campesterol and brassicasterol; the fatty acid part of the plant sterol fatty acid ester is selected from one or more of saturated fatty acid and unsaturated fatty acid with 12-24 carbon atoms; and/or

The liquid oil is liquid vegetable oil.

4. The crystallization accelerator according to claim 3, wherein the fatty acid moiety of the plant sterol fatty acid ester is one or more selected from the group consisting of saturated fatty acids and unsaturated fatty acids having 16 to 24 carbon atoms.

5. The crystallization accelerator according to claim 4, wherein the fatty acid moiety of the plant sterol fatty acid ester is selected from one or more of lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, behenic acid, erucic acid, and tetracosenic acid.

6. The crystallization accelerator according to claim 1, wherein the liquid oil is one or a mixture of any two or more of rice oil, sunflower oil, palm kernel oil, peanut oil, rapeseed oil, cottonseed oil, safflower oil, perilla oil, tea seed oil, coconut oil, olive oil, cocoa butter, almond oil, rubber seed oil, rice bran oil, corn germ oil, wheat germ oil, sesame seed oil, linseed oil, evening primrose seed oil, hazelnut oil, walnut oil, grape seed oil, glass chicory seed oil, sea buckthorn seed oil, tomato seed oil, pumpkin seed oil, macadamia nut oil, and algae oil.

7. The crystallization accelerator according to claim 1, wherein,

the plant sterol also comprises one or more of stigmasterol, campesterol and brassicasterol; and/or

The plant sterol portion of the plant sterol fatty acid ester further comprises one or more of stigmasterol, campesterol, and brassicasterol.

8. The crystallization accelerator according to claim 7, wherein the plant sterols comprise β -sitosterol, stigmasterol, campesterol, and brassicasterol.

9. The crystallization accelerator according to claim 8, wherein the mass fraction of beta-sitosterol is not less than 40% based on the total weight of the phytosterols.

10. The crystallization accelerator according to claim 9, wherein the mass fraction of beta-sitosterol is not less than 42% based on the total weight of the phytosterols.

11. The crystallization accelerator according to claim 7, wherein the plant sterol portion of the plant sterol fatty acid ester comprises β -sitosterol, stigmasterol, campesterol, and brassicasterol.

12. The crystallization accelerator according to claim 11, wherein the mass fraction of beta-sitosterol is not less than 40% based on the total weight of the plant sterol portion of the plant sterol fatty acid ester.

13. The crystallization accelerator according to claim 12, wherein the mass fraction of beta-sitosterol is not less than 42% based on the total weight of the plant sterol portion of the plant sterol fatty acid ester.

14. The crystallization accelerator according to claim 11, wherein the mass fraction of the phytosterol fraction is not less than 50% based on the total weight of the phytosterol fatty acid ester.

15. The crystallization accelerator according to claim 14, wherein the mass fraction of the phytosterol fraction is greater than or equal to 58% based on the total weight of the phytosterol fatty acid ester.

16. The crystallization accelerator according to claim 15, wherein the mass fraction of the phytosterol fraction is not less than 60% based on the total weight of the phytosterol fatty acid ester.

17. The crystallization accelerator according to claim 1, wherein,

the plant sterol contains beta-sitosterol, stigmasterol, campesterol and brassicasterol, and the total mass fraction of the beta-sitosterol, stigmasterol, campesterol and brassicasterol is more than or equal to 80% based on the total weight of the plant sterol; the plant sterol part of the plant sterol fatty acid ester comprises beta-sitosterol, stigmasterol, campesterol and brassicasterol, and the total mass fraction of the beta-sitosterol, stigmasterol, campesterol and brassicasterol in the plant sterol part of the plant sterol fatty acid ester is more than or equal to 80%; the fatty acid part of the plant sterol fatty acid ester is palmitic acid, stearic acid, oleic acid, linoleic acid and tetracosenoic acid; or (b)

The plant sterol is beta-sitosterol, and the plant sterol fatty acid ester is beta-sitosterol oleate.

18. The crystallization accelerator according to claim 17, wherein the total mass fraction of beta-sitosterol, stigmasterol, campesterol and brassicasterol is not less than 85% based on the total weight of the phytosterols.

19. The crystallization accelerator according to claim 18, wherein the total mass fraction of β -sitosterol, stigmasterol, campesterol and brassicasterol is not less than 90% based on the total weight of the phytosterols.

20. The crystallization accelerator according to claim 19, wherein the total mass fraction of β -sitosterol, stigmasterol, campesterol and brassicasterol is not less than 95% based on the total weight of the phytosterols.

21. The crystallization accelerator according to claim 17, wherein the mass fraction of beta-sitosterol is not less than 40% based on the total weight of the phytosterols.

22. The crystallization accelerator according to claim 21, wherein the mass fraction of beta-sitosterol is not less than 42% based on the total weight of the phytosterols.

23. The crystallization accelerator according to claim 17, wherein the total mass fraction of β -sitosterol, stigmasterol, campesterol and brassicasterol in the plant sterol fraction of the plant sterol fatty acid ester is not less than 85%.

24. The crystallization accelerator according to claim 23, wherein the total mass fraction of β -sitosterol, stigmasterol, campesterol and brassicasterol in the plant sterol fraction of the plant sterol fatty acid ester is not less than 90%.

25. The crystallization accelerator according to claim 24, wherein the total mass fraction of β -sitosterol, stigmasterol, campesterol and brassicasterol in the plant sterol fraction of the plant sterol fatty acid ester is not less than 95%.

26. The crystallization accelerator according to claim 17, wherein the mass fraction of beta-sitosterol in the plant sterol fraction of the plant sterol fatty acid ester is not less than 40%.

27. The crystallization accelerator according to claim 26, wherein the mass fraction of beta-sitosterol in the plant sterol fraction of the plant sterol fatty acid ester is not less than 60%.

28. The crystallization accelerator according to claim 27, wherein the mass fraction of beta-sitosterol in the plant sterol fraction of the plant sterol fatty acid ester is not less than 70%.

29. A method for improving the freezing resistance or degreasing of rice oil, which is characterized by comprising the steps of adding the crystallization promoter according to any one of claims 1-28 to rice oil, cooling and crystallizing the rice oil, and then performing solid-liquid separation; wherein the ratio of the total mass of the plant sterol and the plant sterol fatty acid ester in the crystallization promoter to the mass of the rice oil is 2:98 to 10:90.

30. The method of claim 29, wherein the method has one or more of the following features:

the rice oil is selected from degummed rice oil, dewaxed rice oil, deacidified rice oil, decolorized rice oil and deodorized rice oil;

adding a crystallization promoter into rice oil at 45-90 ℃;

the total time of the cooling procedure is not more than 48 hours;

the temperature of the cooling program is 0-3 ℃;

the shape of the crystal formed by the crystallization of the rice oil is sea urchin-shaped, and the average crystal size is more than or equal to 80 mu m.

31. The method according to claim 29, wherein the mass ratio of the total mass of the plant sterols and plant sterol fatty acid esters to the rice oil in the crystallization promoter is 3:97 to 6:94.

32. The method according to claim 30, wherein the crystallization promoter is added to rice oil at 45 to 60 ℃.

33. The method of claim 30, wherein the total time of the cooling process is no more than 36 hours.

34. The method of claim 33, wherein the total cooling time is 25-36 hours.

35. The method of claim 29, wherein the cooling crystallization comprises, in order: and cooling the rice oil added with the crystallization promoter from 45-90 ℃ to 23-28 ℃ at a cooling rate of 3-4 ℃/h, cooling to 18-22 ℃ at a cooling rate of 2-3 ℃/h, cooling to 5-10 ℃ at a cooling rate of 0.5-1.5 ℃/h, keeping the temperature for 2-4 h, and cooling to 0-3 ℃ at a cooling rate of 0.5-1.5 ℃/h.

36. The method of claim 35, wherein the rice oil added with the crystallization promoter is cooled from 45 to 60 ℃ to 23 to 28 ℃ at a cooling rate of 3 to 4 ℃/h.

37. The method of claim 29, wherein the solid-liquid separation is performed by centrifugation or filtration.

38. The method of claim 37, wherein the centrifugation temperature is 0-5 ℃, the centrifugation time is 20-40 min, and the centrifugation speed is 6000-10000 rpm.

39. A rice oil prepared by the method of any one of claims 29-38.

40. The rice oil of claim 39, wherein the rice oil has a freezing time of 72 minutes or more as measured according to GB/T17756 standard.

41. An application selected from the group consisting of:

(1) Use of the crystallization promoter according to any one of claims 1-28 for degreasing rice oil to improve the freezing resistance of the rice oil;

(2) Use of the crystallization promoter according to any one of claims 1-28 for the preparation of a reagent for degreasing rice oil to improve the freezing resistance of the rice oil;

(3) The application of the plant sterol and the plant sterol fatty acid ester in degreasing rice oil to improve the freezing resistance of the rice oil or in preparing a crystallization promoter for degreasing the rice oil to improve the freezing resistance of the rice oil; wherein the mass ratio of the plant sterol to the plant sterol fatty acid ester is 4:6-7:3; the plant sterol comprises beta-sitosterol, and the mass fraction of the beta-sitosterol is more than or equal to 35% based on the total weight of the plant sterol; the plant sterol part of the plant sterol fatty acid ester comprises beta-sitosterol, and the mass fraction of the beta-sitosterol is more than or equal to 35 percent based on the total weight of the plant sterol part of the plant sterol fatty acid ester.

42. The use according to claim 41, wherein the mass ratio of plant sterol to plant sterol fatty acid ester is from 5:5 to 6:4.

43. The use according to claim 41, wherein the plant sterols and plant sterol fatty acid esters are according to any one of claims 3 to 28.