A process for simultaneously preparing walnut oil and walnut dough using a grinding and kneading method
By simultaneously preparing walnut oil and dough through grinding and kneading, the problems of low oil yield, high equipment cost, and complex processes in existing technologies have been solved. This method achieves efficient and simple separation of walnut oil and dough and continuous automated production, resulting in walnut oil and dough that are rich in nutrients and of excellent quality.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- YUNNAN UNIVERSITY OF CHINESE MEDICINE
- Filing Date
- 2023-12-29
- Publication Date
- 2026-06-30
AI Technical Summary
Existing walnut oil extraction processes suffer from problems such as low oil yield, high labor intensity, high equipment costs, risk of harmful residues, complex procedures, and heavy environmental impact, making it difficult to achieve continuous automated production and efficient separation of walnut oil and dough.
The grinding and kneading method is used to form walnut dough by kneading walnut kernels with water to achieve hydration, ionization and cross-linking, and hydrophobic liquid walnut oil is extracted. The walnut oil and dough are then separated into a simple solid-liquid mixture using existing food processing equipment.
It achieves efficient separation of walnut oil from dough, with an oil yield of 85-95%, rich in nutrients, low peroxide value and acid value, simple process, low equipment requirements, and is suitable for continuous automated production.
Smart Images
Figure CN117903868B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of grain and oil processing technology, specifically to a process for simultaneously preparing walnut oil and walnut dough using a grinding and kneading method. Background Technology
[0002] The statements in this section provide only background information relevant to the disclosure of this application and may not constitute prior art.
[0003] Currently, the main walnut oil extraction processes include pressing (such as traditional pressing and mechanical pressing), organic solvent extraction (commonly using solvent No. 4 and No. 6), aqueous extraction (also known as water displacement, water solubility, or boiling), and supercritical fluid extraction. Traditional pressing and hydraulic cold pressing have low oil yields, high labor intensity, and are not suitable for continuous automated production. Screw pressing has a higher oil yield, but it is mostly hot pressing, resulting in severe protein denaturation, high oil turbidity, and high refining load. Organic solvent extraction (commonly using solvent No. 4 or No. 6) carries the risk of solvent and harmful residues. Supercritical fluid extraction requires pressure vessels, resulting in high equipment investment and maintenance costs. Water displacement (including boiling, water solubility, or aqueous extraction) is a traditional Chinese method of edible oil preparation with a history of thousands of years. It usually does not require pressing equipment and is often used in family workshops for the preparation of shelled walnut kernel oil. The Naval Medical Research Institute explored an optimal material-to-liquid ratio of 1:0.7, a water dilution temperature of 70℃, and a water pH of 7 to achieve an oil yield of 88.51%. Centrifugation yielded an oil yield of 88.51%, but this method had drawbacks such as the need for raw material roasting and centrifugation [Wang Xuehui, et al. Study on aqueous oil extraction from Hetian walnuts. Food Industry, 2009, 1:39]. Enzymatic, ultrasonic, microwave, and freezing-assisted demulsification methods can achieve yields of over 90% (Liu Miao, et al. Study on water-based walnut oil extraction process and analysis of effective components. China Oils and Fats, 2004, 3:13), but these methods often face challenges such as complex processes and equipment, high energy consumption, heavy environmental impact, and difficulties in continuous production. Summary of the Invention
[0004] The purpose of this invention is to address the shortcomings of current walnut oil extraction processes by providing a process for simultaneously preparing walnut oil and walnut dough through grinding and kneading. This process allows for the direct extraction of liquid walnut oil from the walnut dough during the forming process through grinding and kneading, thus achieving a simple separation between liquid walnut oil and solid walnut dough. This solves many technical problems and difficulties existing in the aforementioned technologies.
[0005] The technical solution of the present invention is as follows:
[0006] A process for simultaneously preparing walnut oil and walnut dough by grinding and kneading utilizes kneading to allow walnut kernels to hydrate, become water-soluble, and fully cross-link and aggregate with water, forming a dough and releasing hydrophobic liquid walnut oil, thus separating the hydrophobic liquid walnut oil from the hydrophilic solid walnut dough.
[0007] Specifically, the steps include the following:
[0008] Includes the following steps:
[0009] Step (1): Grind the walnut kernels into a walnut paste with an average particle size range of 0.02mm to 0.25mm; preferably, grinding can be done using a colloid mill or a bone paste mill. This fineness facilitates kneading and allows the hydrophilic components or groups such as protein in the material to undergo hydration, watering, cross-linking, and aggregation with an appropriate amount of water to form a dough of suitable hardness and precipitate hydrophobic liquid oil.
[0010] Step (2): Use a dough kneading and gluten washing machine to knead the walnut paste. During this process, add 0.025-0.12 times the dry weight of the walnut kernels to 35-65℃ hot water and knead at 40-100r / min for 10-30 minutes. During this process, the walnut kernels, which are rich in gluten and prolysin, undergo hydrophilic hydration, watering, and full cross-linking and aggregation with a small amount of water to form a dough of suitable hardness and simultaneously release hydrophobic liquid oil.
[0011] Step (3): Separate the walnut dough and walnut oil into solid and liquid components.
[0012] Preferably, step (3) can specifically be: using a screw conveyor to lift the solid dough out, while the liquid walnut oil flows out from the liquid outlet of the gluten washing machine, thereby achieving simple solid-liquid separation between the hydrophobic liquid walnut oil and the hydrophilic solid walnut dough.
[0013] Within the hot water temperature range in step (1), it is beneficial for the hydration, hydration, cross-linking, aggregation and organization of hydrophilic components or groups such as walnut protein to form dough of suitable hardness and for the precipitation of liquid oil, as well as for the easy separation of solid dough and liquid oil.
[0014] According to a preferred embodiment, in step (2), the amount of water added is 0.11 times the dry weight of the walnut kernels.
[0015] According to a preferred embodiment, in step (2), the kneading time is 25 minutes.
[0016] According to a preferred embodiment, in step (2), the kneading temperature is 35-55°C.
[0017] According to a preferred embodiment, in step (2), the kneading temperature is 45°C.
[0018] According to a preferred embodiment, in step (2), walnut paste and water are kneaded in a dough mixing and washing machine. Other devices can also be used for kneading. The kneading parameters can vary depending on the machine used. When using a dough mixing and washing machine, the rotation speed range is 40-100 r / min. Too high a rotation speed will damage the structured gluten and dough. Kneading under these suitable conditions can efficiently promote the hydration, watering, cross-linking, aggregation and structure of hydrogen bonds rich in hydrophilic components such as walnut protein with an appropriate amount of water to form a walnut dough of suitable hardness and precipitate walnut oil. It also facilitates the liquid-solid separation of solid walnut dough and liquid walnut oil.
[0019] Based on its mechanism, this invention allows for the simultaneous preparation of walnut oil and walnut dough using a dough washing machine. The main difference from traditional dough washing is that when washing gluten, a continuous liquid phase of water is used to knead and wash out starch granules, fiber, and carbohydrates from the dough skeleton (i.e., gluten). Since these are mostly particulate matter, washing is difficult and requires multiple washes with water. However, when used for the simultaneous preparation of walnut oil and walnut dough, the continuous flowing liquid phase consists of hydrophobic liquid walnut oil that has been precipitated through kneading. By controlling the added water to be absorbed by walnut protein and other hydrophilic substances as much as possible, resulting in hydration, hydrolysis, and hydrogen bonding to form bound water, the water content in the liquid walnut oil can be reduced to a very low level, leaving very few hydrophilic impurities. Furthermore, the hydrophilic dough's repulsion of hydrophobic substances and the kneading action promote the precipitation of oil from the dough into the hydrophobic flowing liquid walnut oil, reducing the oil content and hydrophobic components in the hydrophilic walnut dough to a low level, typically below 6%. Furthermore, the appropriately firm and textured walnut dough obtained through kneading and separation makes it easier to further reduce residual oil to below 5% using pressing methods (such as hydraulic pressing or screw conveyor pressing).
[0020] This invention utilizes existing conventional food processing equipment, including but not limited to grinders, bone meal mills, colloid mills, dough mixers, kneading machines, dough washing machines, and screw conveyors, which, through appropriate combinations, can achieve online, continuous, automated, and synchronous production of walnut oil and walnut dough. Employing screw or spiral conveyors can further improve the oil yield while achieving continuous, automated production.
[0021] Walnut oil prepared using the method of the present invention.
[0022] The application of walnut oil prepared by the method of the present invention in edible and production of premium or first-grade edible walnut oil.
[0023] The walnut oil obtained by the grinding and kneading method of this invention can be consumed directly or, after appropriate refining, can meet the relevant standards for premium or first-grade edible walnut oil.
[0024] Application of walnut dough prepared using the method of the present invention in the preparation of food products.
[0025] The walnut dough of suitable hardness obtained by this invention can be directly shaped into products such as cakes, slices, strips (such as noodles, energy bars, etc.), balls, puffed foods, and textured foods, with or without the addition of auxiliary materials.
[0026] Compared with existing technologies, the advantages of this invention are:
[0027] 1. A process for simultaneously preparing walnut oil and walnut dough by grinding and kneading. Due to the repeated extraction effect of kneading, the walnut oil obtained is rich in hydrophobic and lipophilic components of walnuts, such as lipophilic vitamins, phytosterols, squalene, fat-soluble flavonoids, and phenolic compounds. Water is mainly stored in the textured and structured walnut dough in the form of bound water along with proteins, dietary fiber, carbohydrates, and other non-oil hydrophilic components such as free acids. The resulting walnut oil is rich in nutrients and usually does not require degumming.
[0028] 2. A process for simultaneously preparing walnut oil and walnut dough by grinding and kneading, wherein the sulfhydryl groups in walnut protein will form disulfide bonds during the dough formation process, which is beneficial to the stability of the protein network structure and the reduction of the redox potential in the system, thereby reducing the peroxide value of walnut oil.
[0029] 3. A process for simultaneously preparing walnut oil and walnut dough using a grinding and kneading method. Compared to traditional methods such as water extraction, pressing, solvent extraction, and supercritical fluid extraction, the method of this invention is simpler, requiring only simple grinding and kneading without complex centrifugation or pressure filtration. It also does not require operation under ultra-high or high pressure conditions, and the oil extraction rate is faster. The resulting walnut oil has low peroxide value and acid value, and high content of micronutrients. Specific advantages are analyzed and compared in the table below:
[0030]
[0031] Attached Figure Description
[0032] Figure 1 The curve showing the relationship between water addition and initial oil yield;
[0033] Figure 2 The curve showing the relationship between kneading time and oil yield;
[0034] Figure 3 The curve showing the relationship between kneading temperature and walnut oil yield;
[0035] Figure 4 A comparison of the main nutritional components (% of dry weight) and protein types (% of total protein content) of walnut kernels and wheat flour. Detailed Implementation
[0036] The features and performance of the present invention will be further described in detail below with reference to embodiments. It should be noted that, unless otherwise specified, the methods used in this application are all conventional methods; and unless otherwise specified, the experimental materials used in this application are all commercially available. The dough mixing and gluten washing machine of this application can be a commercially available dough mixing and gluten washing machine or a dough kneading and mixing machine.
[0037] Example 1
[0038] Step (1): Grind the walnut kernels into a paste using a colloid mill (average particle size 0.08mm).
[0039] Step (2): Weigh 500g of the ground walnut paste into a dough mixer and add 35℃ hot water (the water amounts are 0%, 3%, 6%, 9%, and 12% of the dry weight of the walnut kernels, respectively). Knead at 80 rpm for 25 minutes.
[0040] Step (3): Use a screw conveyor to lift the solid dough out, while the liquid walnut oil is discharged from the liquid outlet of the gluten washing machine. Observe the solid-liquid separation, observe the dough formation and oil-solid separation, take out the walnut dough, weigh it and calculate the walnut oil yield, and finally obtain the relationship curve between different water additions and walnut oil yield.
[0041] The obtained relationship curve is as follows Figure 1 As shown, from Figure 1 It can be seen that the yield of walnut oil is low when no water is added. As the amount of water added increases, the yield of walnut oil gradually increases. The yield of walnut oil is highest when the amount of water added reaches 11%. After that, the yield of walnut oil no longer increases when the amount of water added is further increased.
[0042] like Figure 1 As shown, the hardness of the prepared dough gradually increases with the increase of water content, and the hardness is the highest when the water content is 11%. Subsequently, the hardness of the dough begins to decrease when the water content is further increased.
[0043] Example 2
[0044] Step (1): Grind the walnut kernels into a paste using a grinder (average particle size 0.25mm).
[0045] Step (2): Weigh 500g of the ground walnut paste into a dough mixer and add 50ml of 65℃ hot water (10% of the dry weight of the walnut kernels). Knead at 100rpm and observe the dough formation and liquid oil extraction. Take out the walnut dough and liquid walnut oil at different times of 10min, 15min, 20min, 25min, and 30min, weigh them, and calculate the walnut oil yield. Obtain the effect of different kneading times on the walnut oil yield. The results are as follows: Figure 2 .
[0046] Depend on Figure 2 It can be seen that at a kneading temperature of 65℃, the yield of walnut oil varies with the length of kneading time. When the kneading time is from 10 min to 25 min, the yield of walnut oil gradually increases. However, when the time is greater than 25 min, the yield decreases instead of increasing, indicating that excessive kneading is not conducive to the extraction of oil from the dough.
[0047] The kneading time of this invention can be adjusted appropriately according to the structure and capacity of the kneading device. For example, if the kneading capacity is large, the kneading time can be appropriately extended. The more economical and efficient kneading time is 5-25 minutes. The walnut oil yield is related to the oil content of the walnut kernels. For walnut kernels with an oil content higher than 50-65%, the walnut oil yield can reach 85-95%. Since the walnut dough with suitable hardness and texture separated by kneading is easy to press (such as hydraulic pressing or screw conveyor pressing) to reduce residual oil, its oil yield can be further increased to more than 95%.
[0048] Example 3
[0049] Step (1): Grind the walnut kernels into a paste using a bone paste mill (average particle size 0.02mm).
[0050] Step (2): Weigh 500g of the ground walnut paste into a dough mixer and add 50ml of hot water (10% of the dry weight of the walnut kernels) at different temperatures (25℃, 35℃, 45℃, 55℃, 65℃). Knead at 40rpm for 25 minutes.
[0051] Step (3): Take out the walnut dough, weigh it, calculate the walnut oil yield, and finally obtain the relationship curve between different kneading temperatures and walnut oil yield. (See...) Figure 3 )
[0052] Depend on Figure 3 It can be seen that when the kneading time is 25 minutes, the walnut oil yield first increases and then decreases with the change in kneading temperature, indicating that a higher walnut oil yield can be obtained under appropriate temperature conditions.
[0053] like Figure 4As shown, walnut kernels generally contain 5.2% water, 14.9% protein, 58.8% fat, and 9.6% carbohydrates (Yang Yuexin, et al., Chinese Food Composition Tables, Peking University Medical Press, 2009). Walnut protein is mainly composed of gluten, globulin, albumin, and prolamins, accounting for 70.11%, 17.57%, 6.81%, and 5.33% of the total walnut protein, respectively (Liu Ling, et al., Food and Fermentation Industries, 2009, 35:116). Gluten can hydrate with water under suitable conditions, accompanied by molecular cross-linking, aggregation, and structuralization, exhibiting strong elasticity. Prolamins, also known as collagen, have strong viscosity, extensibility, and swelling properties after hydration; they are the main skeletal substances in dough kneading and gluten washing. However, prior to this invention, the economically viable application of these technologies in the simultaneous preparation of walnut oil and walnut dough was not discovered.
[0054] The embodiments described above merely illustrate specific implementation methods of this application, and while the descriptions are detailed and specific, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the technical solution of this application, and these modifications and improvements all fall within the scope of protection of this application.
Claims
1. A process for the simultaneous preparation of walnut oil and walnut dough by grinding rubbing method, characterized in that, By kneading, the hydrophilic components in the walnut kernels are hydrated, hydrolyzed, and fully cross-linked and aggregated with water, forming a dough and releasing hydrophobic liquid walnut oil, thus achieving a simple solid-liquid separation between the hydrophobic liquid walnut oil and the hydrophilic solid walnut dough. Specifically, the steps include the following: Step (1): Grind the walnut kernels into a walnut paste with an average particle size range of 0.02mm to 0.25mm; Step (2): Use a dough mixing and washing machine to knead the walnut paste. During this process, add hot water at 35-65℃ at 40-400rpm for 10-30 minutes, according to 0.025-0.12 times the dry weight of the walnut paste. The hydrophilic components in the walnut kernels will hydrate, hydrate, and fully cross-link and aggregate with the water, forming a solid dough and releasing hydrophobic liquid walnut oil. Step (3): Separate the walnut dough and walnut oil into solid and liquid components.
2. A process for the simultaneous preparation of walnut oil and walnut dough by grinding and rubbing according to claim 1, characterized in that, In step (1), the particle size of the walnut kernels is 0.08 mm.
3. The process for simultaneously preparing walnut oil and walnut dough by grinding and kneading according to claim 1, characterized in that, In step (1), the amount of water added is 0.11 times the dry weight of the walnut kernels.
4. The process for simultaneously preparing walnut oil and walnut dough by grinding and kneading according to claim 1, characterized in that, In step (2), the kneading time is 25 minutes.
5. The process for simultaneously preparing walnut oil and walnut dough by grinding and kneading according to claim 1, characterized in that, In step (2), the hot water temperature is 35-55℃.
6. The process for simultaneously preparing walnut oil and walnut dough by grinding and kneading according to claim 5, characterized in that, In step (2), the hot water temperature is 45℃.
7. Walnut oil prepared by the process described in any one of claims 1-6.
8. The use of walnut oil prepared by the process described in any one of claims 1-6 in edible and production of premium or first-grade edible walnut oil.
9. The use of walnut dough prepared by the process described in any one of claims 1-6 in the preparation of food products.