A method for increasing rutin content in tartary buckwheat seeds using superheated steam technology

Abstract

The present invention discloses a method for increasing the rutin content in tartary buckwheat seeds using superheated steam technology. The method comprises the steps of tempering and superheating the whole tartary buckwheat seeds in their shells. This method breaks with the conventional wisdom that high-temperature treatment of tartary buckwheat inevitably leads to flavonoid loss. By utilizing the pressure difference between the inside and outside of the tartary buckwheat hulls caused by high-temperature airflow within a short period of time, the method promotes the migration of rutin from the hulls into the tartary buckwheat seeds. This migration is further accelerated by using water from the tempering process as a transfer medium. This method fully utilizes the nutritional value of the hulls, increases the rutin content in the tartary buckwheat seeds, and thus enhances the nutritional and functional value of the edible portion of the tartary buckwheat.

Description

Technical Field

[0001] The invention belongs to the technical field of miscellaneous grain processing, and particularly relates to a method for increasing the rutin content in tartary buckwheat seeds by utilizing superheated steam technology. Background Art

[0002] Buckwheat is a healthy food ingredient used for both medicinal and edible purposes. It is rich in functional ingredients such as bioflavonoids, D-chiro-inositol, sugar alcohols, and resistant starch. Among these functional ingredients, rutin is the defining characteristic of buckwheat and the largest component of its flavonoids, comprising approximately 80%. Rutin has physiological functions such as regulating postprandial blood sugar, lowering blood lipids, and reducing blood pressure. To increase the flavonoid content of buckwheat, researchers have worked extensively on breeding and cultivation, significantly increasing its flavonoid content. Currently, the total amount of rutin and other flavonoids in buckwheat has increased from an average of approximately 1% to nearly 3%. Research has found that, in addition to a certain amount of flavonoids in buckwheat seeds, buckwheat hulls, buckwheat flowers, and straw are also very rich in rutin and other flavonoids. Studies have shown that the flavonoid content of buckwheat hulls is lower than that of buckwheat seeds (by 1 / 3 to 1 / 2). However, because buckwheat hulls account for a significant portion of the total weight (over one-third of the total weight of buckwheat hulls), their flavonoid content accounts for over one-third of the total flavonoid content in buckwheat seeds and about half of the flavonoid content in buckwheat seeds. After processing, the hulls are essentially discarded, and the flavonoids in them are not effectively utilized.

[0003] Buckwheat (whole buckwheat kernels) consists of husks and seeds, which are typically processed and dehulled before consumption. The husks are typically used as feed or pillow fillings. Buckwheat kernels are then made into tartary buckwheat rice or flour, which is divided into whole flour (including the bran) and core flour (excluding the bran and containing only the endosperm). Core flour, due to its superior taste, is highly favored by consumers and enjoys a high market share. Currently, most research focuses on limiting rutinase activity to increase rutin content in buckwheat kernels, such as in [Effect of thermal processing for rutin preservation on the properties of phenolics and starch in Tartary buckwheat achenes, International Journal of Biological Macromolecules, 2020], patents with publication numbers CN115474639A, CN109757566A, and 112493398A.

[0004] Therefore, how to transfer the flavonoids in buckwheat husks into buckwheat grains before food processing such as rice or flour making, and significantly increase the flavonoid content of buckwheat grains to improve the nutritional value of buckwheat grains, is of great significance for buckwheat processing.

[0005] However, the dense structure of buckwheat husks, primarily composed of dietary fiber, significantly restricts the migration of flavonoids such as rutin. Moistening the wheat grains with water is an effective approach to address this problem, but if the moisture content of the grains is significantly increased, the starch-based grains become loose, and some may adhere to the husks. This increases the difficulty of separating the grains from the husks during shelling and flour production, significantly reducing flour yield. Therefore, researchers face the challenge of facilitating the transfer of rutin from the husks into the buckwheat grains while maintaining flour yield. Summary of the Invention

[0006] In order to solve the above technical problems, fully tap the economic value of buckwheat hulls, and improve the nutrition of buckwheat grains, the present invention provides the following technical solutions.

[0007] In a first aspect, the present invention provides a method for processing whole buckwheat grains for enriching rutin using superheated steam technology, the method comprising the steps of sequentially treating the whole buckwheat grains with shells with superheated steam after tempering.

[0008] Preferably, during the tempering process, the mass ratio of whole tartary buckwheat grains with shells to water is 10:1-3, for example: 10:1, 10:1.5, 10:2, 10:2.5, 10:3.

[0009] Preferably, the tempering time in the tempering process is 10-20 min, for example: 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min.

[0010] Preferably, the moisture content of the shelled buckwheat after tempering is 10-25%, for example: 10%, 13%, 14%, 14.90%, 14.93%, 14.95%, 16.35%, 18.16%, 19.17%, 20%, 23.74%, 25%.

[0011] Preferably, the moisture content of buckwheat hulls is 15-30%, for example: 15%, 17.25%, 17.79%, 17.88%, 18.35%, 20%, 25.34%, 27%, 29.30%, 30%.

[0012] Preferably, the moisture content of tartary buckwheat seeds is 12-20%, for example: 12%, 13.13%, 13.33%, 14.31%, 15.42%, 17%, 19.71%, 20%.

[0013] Preferably, the temperature of the superheated steam treatment is 120-180°C, for example: 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C.

[0014] Preferably, the superheated steam treatment time is 1-9 min, for example: 1 min, 1.5 min, 2 min, 3 min, 4 min, 4.5 min, 5 min, 6 min, 7 min, 8 min, 9 min.

[0015] Further preferably, the superheated steam treatment temperature is 120-140° C. and the time is 6-9 minutes.

[0016] Further preferably, the superheated steam treatment temperature is 140-160° C. and the time is 4-6 minutes.

[0017] Further preferably, the superheated steam treatment temperature is 160-180° C. and the time is 3-4 minutes.

[0018] In one embodiment of the present invention, the method for increasing the rutin content in tartary buckwheat seeds comprises the following steps:

[0019] (1) Moistening: Mix the shelled buckwheat with water at a material-liquid ratio of 10-30% of its own weight. After soaking, the moisture content of the shelled buckwheat is 10-25%, and the soaking time is 10-20 minutes.

[0020] (2) Superheated steam treatment: The whole buckwheat kernels with shells were placed in superheated steam at a temperature of 120-180°C for 1-9 min.

[0021] In a second aspect, the present invention provides a method for preparing tartary buckwheat grains with high rutin content, which is characterized by comprising the steps of sequentially tempering, superheated steam treatment and shelling the whole tartary buckwheat grains with shells to obtain the tartary buckwheat grains with high rutin content.

[0022] In a third aspect, the present invention provides a method for preparing tartary buckwheat flour with high rutin content, the preparation method comprising the steps of sequentially tempering whole tartary buckwheat grains with shells, treating them with superheated steam, grinding them into powder, and sieving and shelling them.

[0023] Preferably, during the tempering process, the mass ratio of whole tartary buckwheat grains with shells to water is 10:1-3, for example: 10:1, 10:1.5, 10:2, 10:2.5, 10:3.

[0024] Preferably, the tempering time in the tempering process is 10-20 min, for example: 10 min, 11 min, 12 min, 13 min, 14 min, 15 min, 16 min, 17 min, 18 min, 19 min, 20 min.

[0025] Preferably, the moisture content of the shelled buckwheat after tempering is 10-25%, for example: 10%, 13%, 14%, 14.90%, 14.93%, 14.95%, 16.35%, 18.16%, 19.17%, 20%, 23.74%, 25%.

[0026] Preferably, the moisture content of buckwheat hulls is 15-30%, for example: 15%, 17.25%, 17.79%, 17.88%, 18.35%, 20%, 25.34%, 27%, 29.30%, 30%.

[0027] Preferably, the moisture content of tartary buckwheat seeds is 12-20%, for example: 12%, 13.13%, 13.33%, 14.31%, 15.42%, 17%, 19.71%, 20%.

[0028] Preferably, the temperature of the superheated steam treatment is 120-180°C, for example: 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, 180°C.

[0029] Preferably, the superheated steam treatment time is 1-9 min, for example: 1 min, 1.5 min, 2 min, 3 min, 4 min, 4.5 min, 5 min, 6 min, 7 min, 8 min, 9 min.

[0030] Preferably, a rubber roller husking or a roller belt husking method is used.

[0031] Preferably, in the flour making process, the shelled tartary buckwheat grains are pulverized by a cyclone at a speed of 10,000-35,000 r / min for 10-20 s to prepare whole tartary buckwheat flour, including bran and endosperm.

[0032] In a fourth aspect, the present invention provides a tartary buckwheat product, wherein the processing process of the tartary buckwheat product comprises the steps of sequentially tempering and treating the whole tartary buckwheat grains with shells with superheated steam.

[0033] Preferably, the tartary buckwheat product comprises whole tartary buckwheat grains processed by the method described in the first aspect, or tartary buckwheat grains prepared by the preparation method described in the second aspect, or tartary buckwheat flour prepared by the preparation method described in the third aspect.

[0034] Preferably, the tartary buckwheat product includes tartary buckwheat flour, tartary buckwheat tea or tartary buckwheat beverage.

[0035] Beneficial effects of the present invention:

[0036] The present invention breaks through the conventional understanding that high-temperature treatment of buckwheat will inevitably lead to the loss of flavonoids. It uses superheated steam technology, that is, the pressure difference between the inside and outside of the buckwheat hull caused by high-temperature airflow in a short period of time promotes the migration of rutin in the buckwheat hull to the buckwheat grains, and assists with the use of water constructed by wheat moistening treatment as a transfer medium to accelerate this migration, fully utilize the nutritional value of the buckwheat hull, increase the rutin content in the buckwheat grains, and thus improve the nutritional and functional value of the edible part of the buckwheat. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 Shown are the effects of different superheated steam treatment temperatures on the rutin content in buckwheat seeds and hulls;

[0038] Figure 2 Shown are the effects of different superheated steam treatment times on the rutin content in buckwheat seeds and hulls;

[0039] Figure 3 Shown are the effects of different time and temperature combinations of superheated steam treatment on the rutin content in tartary buckwheat seeds;

[0040] Figure 4 Shown are the effects of different treatments on the rutin content in buckwheat seeds and hulls;

[0041] Figure 5 The figure shows the moisture distribution of tartary buckwheat kernels with shells at different moistening times;

[0042] Figure 6 The figure shows the effect of different watering rates on the rutin content in buckwheat seeds and hulls;

[0043] Figure 7 The figure shows the effect of different water soaking time on the rutin content in buckwheat seeds and hulls;

[0044] In the figure, a, b, and c represent the differences between the different treatment conditions. P There were differences at the statistical level of <0.05. DETAILED DESCRIPTION

[0045] The technical solution of the present invention will be further described below in conjunction with the embodiments and drawings, and the advantages and features of the present invention will become clearer as the description proceeds. However, it should be understood that the embodiments are merely illustrative and do not limit the scope of the present invention.

[0046] Example 1: Effect of superheated steam on rutin content in buckwheat hulls and buckwheat seeds

[0047] 1.1 The whole buckwheat kernels with shells were treated in superheated steam at different temperatures of 120, 150 and 180°C for 3 min, and then cyclone-pulverized to separate the buckwheat kernels (including bran and endosperm) and buckwheat shells.

[0048] 1.2 Buckwheat seeds and husks treated with 120°C, 150°C, and 180°C, and not treated with superheated steam, were collected and the rutin content in the seeds and husks was determined by high performance liquid chromatography. The specific conditions were as follows: chromatographic column: C18 column (250×4.6 mm, 5 μm), mobile phase A: methanol, mobile phase B: 0.5% acetic acid, wavelength: 350 nm, column temperature: 35°C, flow rate: 0.8 mL / min, injection volume: 20 μL, and gradient elution conditions are shown in Table 1.

[0049] Table 1 Gradient elution conditions

[0050]

[0051] like Figure 1 As shown in Figure 2, compared with the control without superheating treatment, the rutin content in buckwheat hulls decreased with the increase of superheated steam treatment temperature, and the differences among the treatments were significant ( P <0.05). Compared with the control without superheating treatment, the rutin content in buckwheat seeds increased with the increase of superheated steam treatment temperature, and the differences among the treatments were significant ( P <0.05). Compared to the rutin content of 15.4 mg / g in the control buckwheat seeds, the rutin content in the seeds at 180°C increased by 23.63% to 19.04 mg / g (15.4 mg / g vs 19.04 mg / g). The rutin content in the husk decreased by 35.91% from 3.37 mg / g in the control to 2.16 mg / g. This suggests that superheated steam treatment promotes the migration of rutin from the husk into the seeds.

[0052] 1.3 The whole buckwheat kernels with shells were placed in superheated steam and treated at 180°C for 1 min, 1.5 min, 3 min, 6 min, and 9 min, respectively. The kernels (including bran and endosperm) and hulls were then separated by cyclone crushing.

[0053] 1.4 Take buckwheat seeds and husks treated with superheated steam for 1 min, 1.5 min, 3 min, 6 min, and 9 min, and samples without superheated steam treatment, respectively, and determine the rutin content in the seeds and husks according to the method in 1.2.

[0054] like Figure 2As shown in Figure 2, the rutin content in buckwheat hulls treated with superheated steam was significantly reduced compared to that in untreated buckwheat seeds ( P <0.05), with the lowest value occurring during 1.5-6 minutes of superheated steam treatment. This suggests that a sufficiently long treatment time is required to achieve maximum rutin migration, but excessive treatment time may denature starch and protein in the buckwheat grains, hindering the migration of rutin from the husk to the grains.

[0055] Compared with the unheated buckwheat seeds, the rutin content in the superheated steam treated buckwheat seeds was significantly increased ( P <0.05, and the rutin content in buckwheat seeds treated with superheated steam for more than 1.5 min was significantly higher than that in the shorter treatment ( P <0.05), but the treatment time of 1.5-9 min had no significant effect on rutin content.

[0056] 1.5 The whole buckwheat kernels with shells were placed in superheated steam treatment under different conditions: 120℃, 9 min, 140℃, 6 min, 160℃, 4 min, 180℃, 3 min, and then cyclone crushed to separate the buckwheat kernels (including bran and endosperm) and buckwheat shells.

[0057] 1.6 Take buckwheat seed and husk samples treated with superheated steam at 120℃ for 9 min, 140℃ for 6 min, 160℃ for 4 min, and 180℃ for 3 min, and determine the rutin content in the buckwheat seed and husk according to the method in 1.2.

[0058] like Figure 3 As shown in the results, the rutin content in buckwheat seeds under the conditions of 120℃, 9 min, 140℃, 6 min, 160℃, 4 min, and 180℃, 3 min had no significant difference ( P >0.05). This shows that both the short-time high temperature and long-time low temperature treatment combinations can achieve the same rutin retention effect. The shorter the superheated steam treatment time, the longer the treatment time. Treatment of whole buckwheat seeds at 120-140℃ for 6-9 min, 140-160℃ for 4-6 min, and 160-180℃ for 3-4 min can effectively increase the rutin content in buckwheat seeds.

[0059] Example 2: Effect of Superheated Steam Treatment on Rutin Content Compared with Conventional Heat Treatment

[0060] 2.1 Three portions of whole buckwheat kernels (with shells) were collected. One portion was subjected to superheated steam at 180°C for 3 minutes; one portion was steamed at 100°C for 15 minutes; and one portion was stir-fried at 180°C for 2 minutes. The three samples were then cyclone-pulverized to separate the buckwheat kernels (including the bran and endosperm) from the hulls.

[0061] 2.2 The rutin content in untreated, superheated steam treated, steamed and fried tartary buckwheat seeds and hulls was determined according to the method in 1.2.

[0062] like Figure 4 As shown in Figure 2, compared with the untreated control, all three heat treatments resulted in a significant decrease in rutin content in buckwheat hulls ( P <0.05), the rutin content in the buckwheat husks treated with superheated steam was significantly lower than that in the steamed and fried buckwheat husks ( P <0.05). Compared with untreated buckwheat seeds, frying reduced the rutin content in buckwheat seeds, while steaming and superheated steaming significantly increased the rutin content in buckwheat seeds ( P <0.05). The rutin content in superheated steam-treated buckwheat seeds (19.04 mg / g) increased by 5.19% compared to the rutin content in steam-treated buckwheat seeds (18.10 mg / g) and by 92.32% compared to the rutin content in roasted buckwheat seeds (9.90 mg / g). This suggests that superheated steam, as a rapid, closed treatment method, achieves optimal rutin enrichment in buckwheat seeds due to the pressure differential that induces rutin migration from the buckwheat husk to the buckwheat seeds.

[0063] Example 3: Effect of tempering on moisture distribution in buckwheat hulls and seeds

[0064] 3.1 Mix the shelled buckwheat with water at a material-to-liquid ratio of 10% by weight and soak for 10, 15, and 20 minutes. Determine the moisture content of each component using a rapid halogen moisture analyzer (see Table 2).

[0065] Table 2 Moisture content

[0066]

[0067] Note: a, b, c, d represent letters in the same column P Statistical difference <0.05

[0068] As shown in Table 2, after 10 minutes of tempering, the moisture content of the shelled buckwheat increased from approximately 8% to nearly 15%. As the tempering time increased, the moisture content of the shelled buckwheat remained constant within 20 minutes. The moisture content of the husk increased from approximately 8% to approximately 18%, with a decreasing trend as the tempering time increased. The moisture content of the buckwheat kernels increased from approximately 8% to approximately 13%, and gradually increased to 14% with increasing tempering time. This suggests that tempering with a fixed amount of water promotes the gradual migration of moisture from the husk to the kernels.

[0069] 3.2 Buckwheat seeds were placed in a 10 mm nuclear magnetic resonance (NMR) tube and then placed in a low-field NMR instrument for proton density imaging. The following parameters were used: an HSE imaging sequence with an offset frequency of 588696.49 Hz, a spectral width of 40 kHz, 64 resamples, 500 echoes, 300 signal acquisition points, a repetition time of 1500 ms, an echo time of 0.376 ms, 1 slice number, a slice width of 0.013 m, and a slice thickness of 0.013 m. MRI images were obtained in grayscale and pseudo-colorized using Osiris software.

[0070] like Figure 5 As shown in the results, within 10 minutes of soaking, water primarily remained on the surface of the shelled buckwheat seeds, i.e., the hull. After 15 minutes of soaking, water had penetrated the hull and reached the outer layer of the seeds. When soaking was extended to 20 minutes, a significant amount of water entered the interior of the seeds. This suggests that water can act as a migration medium, promoting the migration of nutrients such as rutin into the seeds.

[0071] Example 4: Effect of watering amount on rutin enrichment in superheated steam tartary buckwheat grains

[0072] 4.1 Buckwheat shells were mixed with water at a material-liquid ratio of (10%, 20%, 30%) of their own weight. After 15 minutes of soaking, the moisture contents of buckwheat shells were 14.95%, 19.17%, and 23.74%, respectively; the moisture contents of buckwheat shells were 17.88%, 29.30%, and 33.60%, respectively; and the moisture contents of buckwheat grains were 13.33%, 19.71%, and 24.38%, respectively.

[0073] 4.2 Treat the whole buckwheat kernels in shells in superheated steam at 180°C for 3 minutes. Then, separate the buckwheat kernels (including bran and endosperm) and the shells by cyclone crushing.

[0074] 4.3 Determine the rutin content in buckwheat seeds and hulls with different water content and without water according to the method in 1.2.

[0075] like Figure 6 As shown in the results, when the water content was 20% and 30%, the rutin content in the tartary buckwheat seeds was not significantly different from that in the unwatered tartary buckwheat seeds. However, when the water content was 10%, the rutin content in the tartary buckwheat seeds (19.86 mg / g) was 4.31% higher than that in the unwatered tartary buckwheat seeds (19.04 mg / g), and the difference was significant ( P <0.05); compared with the untreated ones, the rutin content in the tartary buckwheat hulls treated with 10% and 20% water was significantly reduced ( P<0.05), but the difference between the water content of 10% and 20% was not significant. The rutin content in the 10% water content buckwheat hull (2.01 mg / g) was significantly lower than that in the unwatered buckwheat hull (2.16 mg / g) by 6.94% ( P <0.05). This indicates that 10% moisture content in the tartary buckwheat hulls is more effective in migrating rutin from the hulls into the grains.

[0076] Example 5: Effect of water soaking time on rutin enrichment in superheated steam tartary buckwheat grains

[0077] 5.1 Mix shelled buckwheat kernels with water at a ratio of 10% by weight to water and soak for 10, 15, and 20 minutes. Next, subject the kernels to superheated steam at 180°C for 3 minutes. Cyclone milling is then performed to separate the kernels (including the bran and endosperm) from the hulls.

[0078] 5.2 Determine the rutin content in buckwheat seeds and hulls soaked for different times according to the method in 1.2.

[0079] like Figure 7 As shown in Figure 2, the rutin content in buckwheat husks soaked for 15 min (2.01 mg / g) was significantly lower than that in buckwheat husks soaked for 20 min (2.41 mg / g) ( P <0.05). The rutin content of buckwheat seeds soaked for 15 min (19.86 mg / g) was significantly higher than that of buckwheat seeds soaked for 10 min (18.66 mg / g) ( P <0.05). This indicates that soaking the shelled buckwheat for 15 min has a better effect on promoting the migration of rutin from the shell to the buckwheat grains, and the rutin content in the buckwheat grains is higher.

[0080] The preferred embodiments of the present invention are described in detail above. However, the present invention is not limited to the specific details in the above embodiments. Within the technical concept of the present invention, various simple modifications can be made to the technical solution of the present invention, and these simple modifications all fall within the scope of protection of the present invention.

Claims

1. A method for increasing the rutin content in tartary buckwheat seeds using superheated steam technology, characterized in that: The method comprises the steps of tempering and superheating steam treatment on whole tartary buckwheat kernels with shells; The tempering time is 10-20 minutes, and the moisture content of the whole tartary buckwheat grains with shells after tempering is 10-25%; The temperature of the superheated steam treatment is 120-180° C., and the time is 1.5-9 minutes.

2. The method according to claim 1, characterized in that During the tempering process, the mass ratio of whole tartary buckwheat grains with shells to water is 10:1-3.

3. The method according to claim 1, characterized in that The wheat tempering time is 15-20 minutes.

4. The method according to claim 1, wherein The moisture content of the whole shelled buckwheat kernels after tempering is 10%.

5. The method according to claim 1, characterized in that The temperature of the superheated steam treatment is 150-180° C., and the time is 1.5-6 minutes.

6. The method according to claim 1, wherein The temperature of the superheated steam treatment is 180° C., and the time is 3 minutes.

7. A method for preparing tartary buckwheat seeds with high rutin content, characterized in that: The method comprises the steps of tempering, superheated steam treatment and shelling of whole tartary buckwheat kernels with shells; The tempering time is 10-20 minutes, and the moisture content of the whole tartary buckwheat kernels with shells after tempering is 10-25%; The temperature of the superheated steam treatment is 120-180° C., and the time is 1.5-9 minutes.

8. A method for preparing tartary buckwheat flour with high rutin content, characterized in that: The preparation method comprises the steps of tempering whole tartary buckwheat grains with shells, treating them with superheated steam, grinding them into powder, and sieving and shelling them: The tempering time is 10-20 minutes, and the moisture content of the whole tartary buckwheat kernels with shells after tempering is 10-25%; The temperature of the superheated steam treatment is 120-180° C., and the time is 1.5-9 minutes.

9. A tartary buckwheat product, characterized in that: The processing of the tartary buckwheat product comprises the steps of tempering the whole tartary buckwheat grains with shells and treating them with superheated steam; The tempering time is 10-20 minutes, and the moisture content of the whole tartary buckwheat kernels with shells after tempering is 10-25%; The temperature of the superheated steam treatment is 120-180° C., and the time is 1.5-9 minutes.

10. A tartary buckwheat product, characterized in that: The tartary buckwheat product comprises whole tartary buckwheat grains processed by the method according to any one of claims 1 to 6, or tartary buckwheat grains prepared by the preparation method according to claim 7, or tartary buckwheat flour prepared by the preparation method according to claim 8.

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