Preparation method of natural strong-flavor soybean oil

Abstract

The invention provides a preparation method of natural strong-flavor soybean oil. The preparation method comprises the following steps: (1) pretreating a soybean raw material; (2) carrying out heat treatment on the pretreated soybean raw materials, namely roasting or baking treatment; (3) cooling the soybean raw material subjected to heat treatment, and then performing mechanical squeezing to obtain crude oil; (4) sequentially carrying out degumming treatment, physical deacidification and deodorization treatment on the crude oil to obtain finished oil; wherein the degumming treatment temperature is not higher than 70 DEG C; the physical deacidification adopts a steam distillation method; the deodorization treatment is carried out under the conditions that the vacuum degree is lower than 3mbar and the temperature is 200-220 DEG C. According to the method, phospholipid, free fatty acid and peculiar smell substances can be efficiently removed to ensure the safety and stability of grease, and meanwhile, the damage and removal of heat-sensitive natural flavor substances are reduced, so that the flavor of the finished product soybean oil is increased.

Description

Technical Field

[0001] This invention relates to the field of soybean oil preparation technology, and in particular to a method for preparing natural, aromatic soybean oil. Background Technology

[0002] Soybean oil is one of the world's most produced vegetable oils, and its conventional industrial production mainly relies on solvent extraction. While this method offers high oil yield and low cost, the resulting crude oil must undergo extensive refining, including alkali refining and high-temperature deodorization, to obtain a finished oil with a clear color, high smoke point, and good stability. However, while this series of drastic refining processes removes impurities and off-odors, it also almost completely eliminates natural flavor compounds (such as pyrazines and furans) that may have formed during the pretreatment stage. This results in commercially available soybean oil generally having a mild flavor and lacking the roasted or nutty aroma characteristic of traditional oils. Summary of the Invention

[0003] In view of this, the present invention proposes a method for preparing natural, aromatic soybean oil, with the aim of improving the flavor of soybean oil.

[0004] The technical solution of this invention is implemented as follows:

[0005] A method for preparing naturally aromatic soybean oil includes the following steps:

[0006] (1) Pre-treatment of soybean raw materials;

[0007] (2) Heat treatment is performed on the pretreated soybean raw materials, wherein the heat treatment is roasting or baking.

[0008] (3) Cool the heat-treated soybean raw material and then mechanically press it to obtain crude oil;

[0009] (4) The crude oil is subjected to degumming, physical deacidification and deodorization treatment in sequence to obtain finished oil; wherein the degumming treatment temperature is not higher than 70°C; the physical deacidification is carried out by steam distillation; the deodorization treatment is carried out under the conditions of vacuum degree below 3mbar and temperature of 200°C to 220°C.

[0010] Preferably, in step (2), the heat treatment is carried out in a rotary roaster or a fluidized bed dryer. The purpose of this preferred solution is to ensure that the whole soybean grains are heated evenly and react consistently. Both of these devices can provide good heat conduction and material agitation, effectively preventing local overheating and scorching or underheating, and can achieve batch-to-batch flavor stability and reproducibility, providing a uniform intermediate raw material for subsequent processes.

[0011] Preferably, in step (2), the heat treatment temperature is 180°C to 220°C, and the time is 15 minutes to 40 minutes. Within this parameter range, the Maillard reaction and lipid degradation reaction can be fully carried out, and abundant characteristic aroma compounds such as pyrazines and furans can be generated efficiently and controllably.

[0012] Preferably, in step (3), before mechanical pressing, the heat-treated soybean raw material is cooled to 60°C to 80°C. Within this temperature range, the high temperature can effectively prevent the loss of a large amount of volatile aroma components that have been generated before pressing, and can also maintain the appropriate plasticity of the soybean meal, ensuring that the subsequent pressing process proceeds smoothly, thereby maximizing the transfer of flavor substances formed in the previous heat treatment to the crude oil.

[0013] Preferably, in step (3), the mechanical pressing is a screw press, and the temperature of the material during the pressing process does not exceed 120°C. Screw pressing is highly efficient and has good continuity; controlling the upper limit of the pressing temperature can significantly suppress the additional thermal oxidation reaction caused by mechanical friction heat, avoid the interference of by-products such as burnt flavor on the main aroma, and ensure the flavor purity from raw material to crude oil.

[0014] Preferably, in step (4), the degumming treatment is a hydration degumming treatment or an acid degumming treatment.

[0015] Preferably, in step (4), the physical deacidification is carried out under conditions of vacuum degree below 5 mbar and temperature of 180°C to 200°C. The purpose is to enable free fatty acids to be efficiently evaporated and removed. At the same time, this condition constitutes an important "boiling point cutoff point", so that a large number of key flavor substances with higher boiling points that are expected to be retained can still exist stably in the oil phase, thereby achieving the goal of "removing harmful acids and retaining beneficial aromas" in a refined manner.

[0016] Preferably, in step (4), the deodorization time is 40 to 90 minutes. The purpose is to ensure the effective removal of low-boiling-point odor components and peroxides to meet product quality standards, while avoiding excessive loss of flavor substances and nutrients due to excessively long heat treatment time.

[0017] Preferably, in step (4), a decolorization process is further included between the degumming treatment and the physical deacidification treatment; in the decolorization treatment, activated clay at 0.5% to 1.5% of the weight of the crude oil is used as an adsorbent, and the process is carried out at 95°C to 105°C under vacuum conditions. The purpose is to gently adsorb and remove pigments, trace metals, and residual gums from the crude oil, improve the color and oxidative stability of the oil, and reduce the burden on subsequent processes. Using a low proportion of activated clay (0.5%-1.5%) and a moderate temperature (95-105°C) can achieve the necessary purification effect while minimizing the adsorption loss of flavor substances and natural tocopherols.

[0018] Compared with the prior art, the present invention has at least the following beneficial effects:

[0019] This invention can efficiently remove phospholipids, free fatty acids, and off-flavor substances to ensure the safety and stability of the oil, while reducing the damage and removal of heat-sensitive natural flavor substances, thereby increasing the flavor of the finished soybean oil. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to specific examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Example 1

[0022] A method for preparing naturally aromatic soybean oil is provided, comprising the following steps:

[0023] (1) Pre-treatment of soybean raw materials: Select fresh, whole, non-GMO soybeans and remove impurities by cleaning sieve.

[0024] (2) Heat treatment of pretreated soybean raw materials: Put soybeans into a rotary roaster and roast them whole. Control the roasting temperature at 200℃ and the time at 30 minutes. Until the soybeans are uniformly brownish-yellow and have a strong roasted aroma.

[0025] (3) Cooling and pressing the heat-treated soybean raw material: The roasted soybeans are quickly air-cooled to 70°C, and then pressed with a double screw oil press at a pressing temperature of ≤110°C to obtain crude oil.

[0026] (4) Refining:

[0027] a. Degumming treatment (acid degumming treatment): The crude oil is heated to 65°C, and food-grade phosphoric acid (85% concentration) of 0.1% by weight of the crude oil is added under stirring to react. Then, an appropriate amount of hot water is added for hydration, and the gum is removed by centrifugation to obtain degummed oil.

[0028] b. Decolorization treatment: Transfer the degummed oil to a decolorization tank. Under conditions of 50 mbar absolute pressure and 100℃ temperature, add 1.0% activated clay by weight of the oil. Stir and decolorize for 25 minutes, then filter through a filter to obtain clear decolorized oil.

[0029] c. Physical deacidification: The decolorized oil is pumped into a physical refining tower. Steam distillation is carried out under conditions of 3 mbar absolute pressure and 190°C to remove free fatty acids.

[0030] d. Deodorization treatment: After physical deacidification, the oil temperature is raised to 210℃ in the same tower, and deodorization treatment is carried out continuously for 60 minutes under an absolute pressure of 2mbar to obtain the finished oil.

[0031] Example 2

[0032] (1) Pretreatment of soybean raw materials: Same as in Example 1.

[0033] (2) Heat treatment of pretreated soybean raw materials: In a fluidized bed dryer, whole soybeans are baked with hot air at 185°C for 40 minutes to produce a mild roasted aroma.

[0034] (3) Cooling and pressing the heat-treated soybean raw material: Cooling to 60℃ and pressing temperature ≤105℃ to obtain crude oil.

[0035] (4) Refining:

[0036] a. Degumming treatment (hydration degumming treatment): Heat the crude oil to 68°C, add hot water (90°C) of about 3% of the oil weight while stirring rapidly, continue stirring for 30 minutes, and then centrifuge to remove the hydrated gums to obtain degummed oil.

[0037] b. Physical deacidification: The degummed oil is pumped into a physical refining tower. Steam distillation is carried out under conditions of 4 mbar absolute pressure and 180°C to remove free fatty acids.

[0038] c. Deodorization treatment: After physical deacidification, the system temperature is raised to 200℃ and deodorized for 90 minutes under an absolute pressure of 2.5mbar to obtain the finished oil.

[0039] Example 3

[0040] (1) Pretreatment of soybean raw materials: Same as in Example 1.

[0041] (2) Heat treatment of the pretreated soybean raw material: rotary roasting at 180℃ for 15 minutes. The soybeans are light yellow and have a fresh soybean aroma.

[0042] (3) Cooling and pressing the heat-treated soybean raw material: Cool down to 65℃ and press at ≤100℃.

[0043] (4) Refining:

[0044] a. Degumming treatment (acid degumming treatment): The crude oil is heated to 70°C, and an appropriate amount of food-grade phosphoric acid is added to react and hydrate. After centrifugation, degummed oil is obtained.

[0045] b. Decolorization treatment: Add 0.5% of the oil weight of activated clay to the degumming oil at an absolute pressure of 60 mbar and 95°C, stir for 20 minutes, and then filter.

[0046] c. Physical deacidification: The filtered oil is deacidified by steam distillation at an absolute pressure of 5 mbar and a temperature of 180°C.

[0047] d. Deodorization treatment: After deacidification, deodorization is carried out at 200℃ and 3mbar absolute pressure for 40 minutes to obtain the finished oil.

[0048] Example 4

[0049] (1) Pretreatment of soybean raw materials: Same as in Example 1.

[0050] (2) Heat treatment of the pretreated soybean raw material: rotary roasting at 220℃ for 40 minutes. The soybeans are dark brown and have a strong caramel and nutty aroma.

[0051] (3) Cooling and pressing the heat-treated soybean raw material: rapidly cool to 80°C and press at ≤115°C.

[0052] (4) Refining:

[0053] a. Degumming treatment (hydration degumming treatment): Heat the crude oil to 60°C, add hot water for hydration, and centrifuge to obtain degummed oil.

[0054] b. Decolorization treatment: Add 1.5% of the oil weight of activated clay to the degumming oil under an absolute pressure of 40 mbar and a temperature of 105°C, stir for 30 minutes, and then filter.

[0055] c. Physical deacidification: The filtered oil is deacidified by steam distillation at an absolute pressure of 2 mbar and a temperature of 200°C.

[0056] d. Deodorization treatment: After deacidification, deodorization is carried out at 220℃ and 1.5mbar absolute pressure for 50 minutes to obtain the finished oil.

[0057] Comparative Example 1 (Traditional solvent leaching combined with deep chemical refining)

[0058] (1) Raw material processing: Take soybeans from the same source as in Example 1, clean them, and without roasting / baking, directly press them into thin sheets using a rolling mill.

[0059] (2) Oil extraction: The soybean curd is fed into the solvent extractor and solvent is extracted with n-hexane to obtain mixed oil; the mixed oil is evaporated and stripped to recover the solvent to obtain crude oil.

[0060] (3) Refining:

[0061] a. Degumming: Heat the extracted crude oil to 80°C, add hot water for hydration and degumming, and centrifuge to separate the gum.

[0062] b. Alkali refining and deacidification (non-physical deacidification): The degummed oil is heated to 70°C, and a certain concentration of sodium hydroxide solution is added to neutralize the free fatty acids in the oil and generate soap residue; then the temperature is raised to 75°C to promote the flocculation of the soap residue, and the soap residue is removed by centrifugation and washed with hot water until the oil is neutral.

[0063] c. Decolorization: Add 3% by weight of activated clay to the alkali-refined oil at 105℃ under vacuum conditions, stir to decolorize, and then filter.

[0064] d. Deodorization: The decolorized oil is subjected to deodorization treatment at an absolute pressure of 2 mbar and a temperature of 240℃ for 120 minutes to obtain the finished oil.

[0065] Comparative Example 2 (High-Temperature Pressing Clay Process)

[0066] (1) Raw materials and heat treatment: Take soybeans from the same source as in Example 1, clean them, and stir-fry them in an open flame wok at about 200°C for 30 minutes.

[0067] (2) Pressing: The roasted soybeans are fed directly into the hydraulic oil press while they are still hot (about 150°C) for high-temperature pressing.

[0068] (3) Processing: The crude oil extracted by pressing is only subjected to natural settling and coarse filtration through gauze, without any degumming, deacidification or deodorization treatment, and is then used as finished oil.

[0069] The key indicators of the finished oil products obtained in Examples 1-4 and Comparative Examples 1-2 were tested, and the results are shown in the table below:

[0070]

[0071] As can be seen from Examples 1-4 and Comparative Examples 1-2, the present invention can efficiently remove phospholipids, free fatty acids and off-flavor substances to ensure the safety and stability of the oil, while reducing the damage and removal of heat-sensitive natural flavor substances, thereby increasing the flavor of the finished soybean oil.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing naturally aromatic soybean oil, characterized in that, Includes the following steps: (1) Pre-treatment of soybean raw materials; (2) Heat treatment is performed on the pretreated soybean raw materials, wherein the heat treatment is roasting or baking. (3) Cool the heat-treated soybean raw material and then mechanically press it to obtain crude oil; (4) The crude oil is subjected to degumming, physical deacidification and deodorization treatment in sequence to obtain finished oil; wherein the degumming treatment temperature is not higher than 70°C; the physical deacidification is carried out by steam distillation; the deodorization treatment is carried out under the conditions of vacuum degree below 3mbar and temperature of 200°C to 220°C.

2. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (2), the heat treatment is carried out in a rotary roasting machine or a fluidized bed dryer.

3. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (2), the heat treatment temperature is 180°C to 220°C and the time is 15 minutes to 40 minutes.

4. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (3), before mechanical pressing, the heat-treated soybean raw material is cooled to 60°C to 80°C.

5. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (3), the mechanical pressing is a screw press, and the temperature of the material during the pressing process is not higher than 120°C.

6. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (4), the degumming process is either hydration degumming or acid degumming.

7. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (4), the physical deacidification is carried out under conditions of vacuum degree below 5 mbar and temperature of 180°C to 200°C.

8. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (4), the deodorization time of the deodorization treatment is 40 to 90 minutes.

9. The method for preparing natural aromatic soybean oil according to claim 1, characterized in that, In step (4), between the degumming treatment and the physical deacidification, a decolorization treatment is also included; in the decolorization treatment, 0.5% to 1.5% of the weight of the crude oil is used as an adsorbent, and the treatment is carried out at 95°C to 105°C under vacuum conditions.

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