Method for peeling cyperus esculentus

Abstract

The invention belongs to the technical field of grain and oil crop processing, and relates to a cyperus esculentus peeling method, which comprises: (1) carrying out heat treatment on cyperus esculentus by using hot water or water vapor; and (2) carrying out alkali liquor soaking treatment on the cyperus esculentus subjected to heat treatment. According to the method disclosed by the invention, through the step of adding hot water or water vapor to treat the cyperus esculentus, wax on the epidermis of the cyperus esculentus can be softened, a wax barrier can be destroyed, alkali liquor can permeate into the epidermis more easily and can play a role more efficiently, and the loosening efficiency of the epidermis of the cyperus esculentus is improved; after the cyperus esculentus is subjected to subsequent treatment of alkali liquor soaking, the technical effect of almost 100% peeling can be achieved; the mandulapalka peeling machine is suitable for mandulapalka of different producing areas and varieties, is not influenced by the sizes and shapes of tubers, and can realize the effect of completely peeling the outer skins of the mandulapalka in batches; the peeled cyperus esculentus is treated by a food-grade citric acid solution, so that the color and flavor of the cyperus esculentus are stabilized.

Description

Technical Field

[0001] This invention belongs to the field of grain and oil crop processing technology, and relates to a method for peeling tiger nuts. Background Technology

[0002] Tiger nuts are a highly adaptable oilseed crop that integrates oil production, grain, livestock, and feed functions. Their oil content is generally 25%-32%, and their oil yield per acre is four times that of soybeans, making them a potentially important supplement to ensuring national food and oil security. Furthermore, tiger nuts are rich in starch, soluble sugars, and dietary fiber, making them a new type of grain and oil crop with high comprehensive utilization value, great development potential, and being non-GMO. They represent a highly promising emerging force in my country's grain and oil production system.

[0003] The development of the tiger nut industry still faces several pressing issues. Tiger nuts are the tubers of a plant, with their outermost layer being a rough and tough periderm. As a processing raw material, this tough periderm hinders the release and extraction of internal components such as oils, phospholipids, starches, sugars, fibers, and proteins, leading to higher energy consumption during oil extraction and flour production, and affecting oil and flour yields, thus reducing production efficiency. As a food ingredient, the presence of phytic acid in the periderm severely affects the absorption of nutrients from tiger nuts by the human body. Simultaneously, the presence of compounds such as cellulose, hemicellulose, lignin, and tannins in the periderm gives tiger nuts a noticeable fibrous texture and astringent taste, which are major obstacles to their direct consumption. The periderm of tiger nuts is typically dark brown or yellowish-brown, and these pigments affect the color of the final product. Retaining the periderm during the processing of tiger nut byproducts can easily lead to a dull color and decreased sensory quality in the final product, significantly weakening its visual appeal and commercial attributes in the market.

[0004] Tiger nuts have an irregular shape and many grooves on their surface, and their outer skin (periderm) is tightly attached to the cortex, making them difficult to remove. Currently used peeling techniques include wet peeling, dry peeling, and acid-alkali treatment-assisted peeling. Wet peeling involves soaking tiger nuts in an alkaline solution to loosen the outer skin; dry peeling uses a specialized peeling machine to remove the outer skin through mechanical friction or compression; acid-alkali treatment-assisted peeling combines acid-alkali chemical action with physical peeling methods, first softening the skin with an acid or alkali solution, then supplementing with mechanical peeling. However, these methods generally suffer from incomplete peeling and high tiger nut breakage rates, making them unsuitable for the requirements of industrial-scale tiger nut processing. Therefore, it is necessary to provide a new, efficient tiger nut peeling method to solve the above technical problems and achieve complete and efficient peeling of tiger nuts. Summary of the Invention

[0005] The main objective of this invention is to overcome the shortcomings of existing technologies in the complete peeling of tiger nuts, and to provide a method for peeling tiger nuts that can achieve almost 100% complete peeling of tiger nuts in batches, thus meeting the needs of industrial production.

[0006] To achieve the above objectives, the specific technical solution is as follows: This invention provides a method for peeling tiger nuts, comprising the following steps: (1) Heat-treat tiger nuts with hot water or steam to soften the waxy coating on the tiger nuts' skin; (2) Soak the heat-treated tiger nuts in a 10%-25% sodium hydroxide solution for 10-30 minutes to perform alkaline soaking treatment, so that the outer skin can be loosened and peeled off.

[0007] The method for peeling tiger nuts provided by this invention softens the waxy coating on the tiger nuts' surface by treating them with hot water or steam, breaking down the waxy barrier and allowing the alkali solution to penetrate more easily into the interior of the surface, thus improving the peeling efficiency. Furthermore, this invention uses a specific concentration of alkali solution and a specific time to soak the heat-treated tiger nuts, ensuring complete separation of the epidermal (periderm) cells from the cortical cells, achieving almost 100% peeling efficiency. Insufficient treatment time or too low an alkali concentration will result in incomplete peeling, while excessive treatment time or too high an alkali concentration will allow the alkali solution to penetrate into the interior of the tiger nuts, adversely affecting their subsequent processing quality. Specifically, NaOH, as a strong alkali, can break the hydrogen bonds within and between cellulose and hemicellulose molecules, causing the fibers to swell and partially dissolve, thereby achieving the purpose of peeling the tiger nuts.

[0008] Furthermore, the heat treatment involves soaking the tiger nuts in hot water at 80-100℃ for 15-25 minutes; or steaming the tiger nuts with water vapor for 10-20 minutes.

[0009] The heat treatment described above in this invention can fully soften the waxy coating on the surface of tiger nuts. If the treatment temperature is too low or the treatment time is too short, the waxy coating will not soften sufficiently, and its dense structure cannot be effectively broken down, resulting in the sodium hydroxide solution failing to fully react with the cellulose and hemicellulose in the coating. If the treatment time is too long, hot water will penetrate into the tiger nuts, producing an undesirable effect similar to steaming, damaging the internal components of the tiger nuts and affecting the quality of subsequent processing.

[0010] Furthermore, it also includes washing the tiger nuts that have been soaked in alkali solution with water to remove the alkali solution and outer skin, and cooling the tiger nuts.

[0011] The present invention involves soaking tiger nuts in alkaline solution and then washing them with water. This process can remove the outer skin that has already detached from the skin but is still physically attached to the tiger nuts (at this point, the tiger nut skin is completely loose and can be easily rubbed off by hand). At the same time, the water treatment can have a suitable cooling effect on the tiger nuts treated with alkaline solution.

[0012] Preferably, the water temperature is 18-25℃ and the water flow rate is 1-10 L / min.

[0013] Specifically, the water washing and peeling process involves using a drum washing and peeling machine or a spiral drum combination washing machine to stir and rinse the tiger nuts that have been soaked in alkaline solution to remove their outer skin.

[0014] Preferably, the water pressure of the drum washing and peeling machine or the spiral drum combination washing machine is 2-6 bar.

[0015] Furthermore, the method for peeling tiger nuts also includes soaking in a citric acid solution.

[0016] Specifically, the tiger nuts after water washing are soaked in a citric acid solution with a mass concentration of 0.5%-2% for 10-30 minutes; food-grade citric acid is preferred.

[0017] The citric acid solution soaking treatment of the present invention stabilizes the flavor of tiger nuts and protects their color.

[0018] Furthermore, after soaking in the citric acid solution, the tiger nuts are washed repeatedly with water until the pH of the tiger nuts reaches 7-8.

[0019] After being washed with water, the product meets national food safety standards. The pH value of the food (GB5009.237—2016) was measured to be 7-8.

[0020] Preferably, the alkaline solution immersion treatment uses a basket-type alkaline solution tank; the citric acid solution immersion treatment uses a basket-type acid solution tank.

[0021] Furthermore, the method for peeling tiger nuts also includes a pre-treatment to remove impurities such as grass leaves, roots, dust, stones, and metal from the tiger nuts.

[0022] Specifically, wind separation is used to remove lightweight impurities such as leaves and dust, screening is used to remove impurities such as stones and fine sand that are significantly different in size from tiger nuts, and magnetic separation is used to remove magnetic metal impurities such as iron nails.

[0023] Compared with the prior art, the present invention has the following significant advantages: The method for peeling tiger nuts provided by this invention softens the waxy coating on the tiger nuts by adding hot water or steam, thereby breaking down the waxy barrier and allowing the alkali solution to penetrate the interior of the skin more easily and work more efficiently, greatly improving the peeling efficiency of the tiger nuts. As a result, after the tiger nuts are soaked in alkali solution, almost 100% peeling can be achieved.

[0024] This invention is applicable to tiger nuts of different origins and varieties, and is unaffected by tuber size and shape, enabling the complete and batch-scale peeling of tiger nuts. It not only significantly improves the quality consistency of tiger nuts as a food ingredient or processed raw material, but also substantially enhances its processing efficiency and applicability in subsequent production stages. Simultaneously, it helps reduce processing losses, improve product appearance and taste, and provides feasible technological support for the high-value utilization of tiger nuts.

[0025] This invention uses food-grade citric acid solution to treat peeled tiger nuts, stabilizing their color and flavor, and adjusting the pH of the peeled tiger nuts to 7-8. This effectively improves the problems of dark color and poor taste caused by ordinary wet peeling, which is very important for the direct consumption of peeled tiger nuts as raw materials or products. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in this invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0027] Figure 1 This is a flowchart of the tiger nut peeling process in Embodiment 1 of the present invention; Figure 2 These are examples of Zhongyousha No. 1 tiger nuts before and after the peeling process in Example 1 of this invention. Left: Before peeling treatment; Right: After peeling treatment; Figure 3 The first embodiment of this invention is the Zhongyousha No. 1 tiger pea, which has undergone batch peeling treatment. Figure 4 These are Yunnan small long-grain tiger nuts before and after the peeling process in Example 2 of this invention; Left: Before peeling treatment; Right: After peeling treatment; Figure 5 The Yuyousha No. 2 tiger nuts that have undergone peeling treatment in Embodiment 3 of this invention; Figure 6 These are examples of tiger nuts (No. 1) before and after the peeling process in Comparative Example 1 of this invention. Left: Before peeling treatment; Right: After peeling treatment; Figure 7 The tiger nuts are the No. 1 tiger nuts after being treated as Comparative Example 2 of this invention. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with the embodiments of this invention. Obviously, the described embodiments are only some embodiments of this invention, not all embodiments. Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this invention.

[0029] Unless otherwise specified in the embodiments of the present invention, the techniques or conditions described in the literature in this field or the product instructions shall be followed; if the manufacturers of the reagents or instruments used are not specified, they are all conventional products that can be purchased through legitimate channels.

[0030] Example 1 like Figure 1 As shown in the figure, this embodiment provides a method for peeling tiger nuts, and the specific steps are as follows: S1 takes 50 kg of Zhongyousha No. 1 tiger nuts produced in Xinjiang Uygur Autonomous Region and performs impurity removal treatment, including wind separation to remove light impurities such as leaves and dust, screening to remove impurities such as stones and fine sand that are significantly different in size from tiger nuts, and magnetic separation to remove magnetic metal impurities such as iron nails. S2 completely immerses the cleaned tiger nuts in 95°C hot water for 15 minutes, stirring intermittently during the process to fully soften the tiger nut skin. S3 After filtering the tiger nuts from S2, soak them in a 20% NaOH solution for 15 minutes, stirring occasionally to separate the outer skin cells from the cortex cells and achieve complete peeling of the outer skin. S4 uses room temperature water at 20℃ to thoroughly wash the sample after step S3 to remove the alkali residue and peeling skin on the tiger nuts, and to cool the tiger nuts. S5 After filtering the tiger nuts sample from S4, soak them in a 2% citric acid solution for 20 minutes, stirring occasionally. S6 Wash the tiger nuts from step S5 five times with water until the pH of the tiger nuts reaches 7.4; the tiger nuts that have completed the peeling process are as follows: Figure 2 As shown; S7 will further process or dry and preserve the peeled tiger nuts obtained from the process.

[0031] This method allows for mass production, producing peeled tiger nuts such as... Figure 3 As shown.

[0032] Example 2 The method in this embodiment is basically the same as that in Embodiment 1, except that in step S1, the material used is small, long-grained tiger nut from Yunnan. Everything else is the same as in Embodiment 1 and will not be repeated here. This embodiment can also achieve complete peeling of Yunnan small, long-grained tiger nut; the peeled tiger nut is as follows: Figure 4 As shown. Figure 4 The Yunnan small long-grain peeled tiger nuts are whiter than those in other examples. This is because the tiger nuts in this treatment are freeze-dried after peeling, while the tiger nuts in other treatments are dried after peeling.

[0033] Example 3 The method in this embodiment is basically the same as that in Embodiment 1, except that in step S1, the material used is Yu You Sha No. 2 from Henan Province. Everything else is the same as in Embodiment 1 and will not be repeated here. This embodiment can also achieve complete peeling for Yu You Sha No. 2 tiger nuts from Henan Province; the peeled tiger nuts are as follows... Figure 5 As shown.

[0034] Comparative Example 1 The method for peeling tiger nuts in this comparative example is basically the same as that in Example 1, except that in step S3, the tiger nuts from S2 are filtered and then immersed in a 20% Na2SO3 solution. Everything else is the same as in Example 1 and will not be repeated here. The original tiger nuts and the treated tiger nuts are shown below. Figure 6 As shown.

[0035] Comparative Example 2 The method for peeling tiger nuts in this comparative example is basically the same as that in Example 1, except that in step S3, the tiger nuts from S2 are filtered and then immersed in a 30% Na2SO3 solution. Everything else is the same as in Example 1 and will not be repeated here. The treated tiger nuts are as follows: Figure 7 As shown.

[0036] Although Comparative Examples 1 and 2 also used alkaline solutions to soak the heat-treated tiger nuts, the Na2SO3 treatment could only partially remove the hairs on the tiger nut's surface, not the outer skin. Soaking it in sodium sulfite solution only served to protect the color and prevent browning. Tiger nuts are tubers, and their outer skin is mainly composed of cellulose, hemicellulose, lignin, and waxes. Under mild processing conditions, Na2SO3 is unlikely to effectively destroy their structure.

[0037] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for peeling tiger nuts, characterized in that, Includes the following steps: (1) Heat-treat tiger nuts with hot water or steam to soften the waxy coating on the tiger nuts' skin; (2) Soak the heat-treated tiger nuts in a 10%-25% sodium hydroxide solution for 10-30 minutes to perform alkaline soaking treatment, so that the outer skin can be loosened and peeled off.

2. The method for peeling tiger nuts according to claim 1, characterized in that, The heat treatment involves soaking tiger nuts in hot water at 80-100℃ for 15-25 minutes, or steaming tiger nuts with water vapor for 10-20 minutes.

3. The method for peeling tiger nuts according to claim 1 or 2, characterized in that, It also includes washing the tiger nuts that have been soaked in alkali solution to remove the alkali solution and outer skin, and cooling the tiger nuts.

4. The method for peeling tiger nuts according to claim 3, characterized in that, The water temperature is 18-25℃ and the water flow rate is 1-10 L / min.

5. The method for peeling tiger nuts according to claim 4, characterized in that, The water washing and peeling process involves using a drum washing and peeling machine or a spiral drum combination washing machine to stir and rinse the tiger nuts that have been soaked in alkaline solution to remove their outer skin.

6. The method for peeling tiger nuts according to claim 5, characterized in that, The water pressure of the drum washing and peeling machine or the spiral drum combination washing machine is 2-6 bar.

7. The method for peeling tiger nuts according to claim 1 or 2, characterized in that, It also includes soaking in citric acid solution.

8. The method for peeling tiger nuts according to claim 7, characterized in that, The tiger nuts after water washing were soaked in a citric acid solution with a mass concentration of 0.5%-2.0% for 10-30 minutes; food-grade citric acid is preferred.

9. The method for peeling tiger nuts according to claim 8, characterized in that, After soaking in the citric acid solution, the tiger nuts were washed repeatedly with water until the pH of the tiger nuts reached 7-8.

10. The method for peeling tiger nuts according to claim 1, 2, or 9, characterized in that, The alkaline solution immersion treatment uses a basket-type alkaline solution tank; the citric acid solution immersion treatment uses a basket-type acid solution tank.

Images