Method for promoting mung bean sprout polyphenol accumulation through blue light combined with methyl salicylate treatment

Abstract

The invention discloses a method for promoting polyphenol accumulation of mung bean sprouts through blue light combined with methyl salicylate treatment. Comprising the following steps: disinfecting screened mung bean seeds with 70% ethanol, then soaking the mung bean seeds in tap water for 6 hours to stimulate the mung bean seeds to germinate, and finally putting the mung bean seeds into an artificial climate box for continuous culture: keeping the temperature of the incubator at 25 DEG C and the humidity at 90%, keeping the temperature constant, changing water once every 12 hours, and culturing for 6 days in total. And starting to apply a methyl salicylate aqueous solution on the fifth day of germination. According to the method, the mung beans are treated by combining blue light with methyl salicylate, so that accumulation of phenols in the germination process of the mung beans is promoted. The oxidation resistance of the mung bean sprouts is further enhanced, so that the nutritional characteristics of the mung bean sprouts as high-quality green vegetables are improved, and a reliable basic technology is provided for the growth of the mung bean sprouts with high nutritional value.

Description

Technical Field

[0001] The present invention relates to the accumulation of polyphenols in mung bean sprouts, and particularly to a method for promoting the accumulation of polyphenols in mung bean sprouts by treating them with blue light in combination with methyl salicylate. Background Art

[0002] Mung bean sprouts are a popular green vegetable, rich in polyphenols, which are a good source of natural antioxidants.

[0003] As a "living vegetable", mung bean sprouts will generate a large amount of reactive oxygen species during the sales process, resulting in a decrease in their nutritional quality. Polyphenols, as strong antioxidants that can scavenge reactive oxygen species, their content is an important quality index of mung bean sprouts. Mung bean sprouts are affected by external environmental factors such as temperature, light, and exogenous additives during the growth process (Wei Y, Wang X, Shao X, et al. Sucrose treatment of mung bean seeds results in increased vitamin C, total phenolics, and antioxidant activity in mung bean sprouts [J]. Food Science & Nutrition, 2019, 7(12): 4037 - 4044.).

[0004] Studies have shown that blue light promotes the accumulation of phenolic substances during the germination and growth of mung beans (Yaoyao C, Honglin C, Yihan Z, et al. Effect of light quality on polyphenol biosynthesis in three varieties of mung bean sprouts with different color seed coats. [J]. Plant cell reports, 2022, 42(2): 253 - 268.).

[0005] In addition, methyl salicylate is a phenolic phytohormone related to stress, and exogenous methyl salicylate can also affect the polyphenol content and antioxidant activity of mung bean sprouts to a certain extent (Chandan T, Sanjay G, Kanika S, et al. Effect of salicylic acid and methyl salicylate treatment on polyphenol metabolites and bioactive properties of mung bean (Vigna radiata) sprouts[J]. Indian Journal of Agricultural Biochemistry, 2022, 35(1): 66-70.). Summary of the Invention

[0006] The purpose of the present invention is to overcome the above-mentioned shortcomings and deficiencies of the prior art, and provide a method for promoting the accumulation of polyphenols in mung bean sprouts by treating with blue light combined with methyl salicylate. The method of the present invention improves the polyphenol content of mung bean sprouts and greatly enhances the nutritional quality of mung bean sprouts at the same time.

[0007] The present invention is realized through the following technical solutions:

[0008] A method for promoting the accumulation of polyphenols in mung bean sprouts by treating with blue light combined with methyl salicylate, comprising the following steps:

[0009] S1, screening of mung bean seeds;

[0010] S2, first disinfect the epidermis of the mung bean seeds selected in step S1 with ethanol, and then wash them clean with water; subject the disinfected and washed mung bean seeds to heat shock; put the mung bean seeds after heat shock into a culture box, add water and perform cold shock at room temperature to soften the mung bean epidermis and promote the germination rate, and finally pour out all the water to complete the cold shock; add water to the mung bean seeds that have completed the cold shock again, and put the culture box into an artificial climate chamber (RQH-01Y, Hubei, China);

[0011] S3, the culture conditions in the artificial climate chamber are: humidity is 90%, temperature is 25°C, and the total culture time is 6 days;

[0012] The light conditions are: darkness and blue light with λ = 460 - 465 nm, the light duration is 24 h / d, and the aqueous solution of methyl salicylate is rinsed by water rinsing and spraying methods successively before and after the germination of mung bean seeds.

[0013] In the above step S1, the screening of mung bean seeds specifically refers to selecting mung bean seeds that are plump, complete, free of pests and diseases, mildew, and of the same size.

[0014] In the above-mentioned step S2, the disinfection of the mung bean seed epidermis with ethanol specifically means weighing 30 g of mung bean seeds and disinfecting the mung bean seed epidermis with 70% ethanol for 0.5 - 1 min.

[0015] In the above-mentioned step S2, the heat shock means rinsing with boiling water in a mung bean seed strainer for 25 - 30 s for heat shock, and the cold shock means adding 300 - 400 mL of tap water to the mung bean seeds and cold shocking them at room temperature for 6 h; the cold shock for 5 - 6 h at room temperature is carried out under dark conditions.

[0016] In the above-mentioned step S3, the specific method of applying the methyl salicylate aqueous solution by rinsing and spraying in sequence during the periods before and after the germination of mung bean seeds is as follows: rinse the mung bean seeds with 60 mL of tap water in the first four days before germination, and start applying the methyl salicylate aqueous solution by spraying 60 mL from the fifth day;

[0017] The rinsing frequency is 12 h / d, and the concentrations of the methyl salicylate solution are 0, 250, 500, and 1000 μM / L;

[0018] Spray 60 mL of methyl salicylate solutions with different concentrations in the last two days during the process of rinsing with the methyl salicylate aqueous solution.

[0019] Compared with the prior art, the present invention has the following advantages and effects:

[0020] In the method of the present invention, by treating mung beans with blue light in combination with methyl salicylate, the accumulation of phenols during the germination process is promoted. Further, the antioxidant capacity of mung bean sprouts is enhanced to improve their nutritional characteristics as high-quality green vegetables, providing a reliable basic technology for the growth of mung bean sprouts with high nutritional value.

[0021] In the method of the present invention, blue light increases the total phenol content and total antioxidant capacity in mung bean sprouts, and three phenolic monomers, namely caffeic acid, rutin, and 7-hydroxycoumarin, respond actively under blue light and are the phenolic substances mainly accumulated under blue light. Moreover, the treatment of mung bean sprouts with 500 μM / L of methyl salicylate in combination with blue light can further increase their total phenol content and total antioxidant capacity. Among them, the total phenol content and ORAC value of group B500 are 1.72 times and 1.80 times that of group D0, respectively. Description of the Drawings

[0022] Figure 1 It is a growth situation diagram of mung bean sprouts under the treatment of blue light and methyl salicylate.

[0023] Figure 2 Among them, A is the influence diagram of blue light and methyl salicylate on the total phenol content of mung bean sprouts; B is the influence diagram (mmol TE / 100 g FW) of blue light and methyl salicylate on the oxygen radical absorbance capacity (ORAC value) of mung bean sprouts. Specific embodiments

[0024] The present invention discloses a method for promoting the accumulation of polyphenols in mung bean sprouts by treating with blue light combined with methyl salicylate. The following further describes the present invention in detail with specific embodiments.

[0025] The mung bean seeds of the Zhonglü 5 variety, which are from the Institute of Crop Science, Chinese Academy of Agricultural Sciences, are selected in the present invention. The seeds after screening and disinfection are treated with boiling water and cold water to stimulate germination, and soaked in tap water for 6 h in a dark environment at room temperature. Then the pre-treated seeds are evenly spread in a germination box, 60 mL of tap water is added, and they are placed in an RQH-01Y type artificial climate chamber for germination culture, with 3 boxes in each group.

[0026] The humidity in the climate chamber is controlled at 90%, and the temperature is 25°C. The light quality conditions are darkness and blue light (λ = 460 - 465 nm), and full-day illumination is adopted. The mung bean sprouts are rinsed with tap water in the first four days of germination, and replaced with 0 - 1000 μM / L methyl salicylate in the last two days.

[0027] After 6 days of germination, the dehulled mung bean sprouts are collected as experimental materials, immediately frozen in liquid nitrogen and stored at -80°C for subsequent experimental determination. According to the light conditions and the concentration of the methyl salicylate solution, the mung bean sprouts are labeled as D0, D250, D500, D1000, B0, B250, B500 and B1000 (D: dark treatment; B: blue light treatment; 0: distilled water treatment; 250: treatment with 250 μM / L methyl salicylate solution; 500: treatment with 500 μM / L methyl salicylate solution; 1000: treatment with 1000 μM / L methyl salicylate solution), as Figure 1 .

[0028] Extraction and determination of polyphenols in mung bean sprouts:

[0029] The mung bean sprouts are ground into powder using a liquid nitrogen grinder. 10.0 g of the powder is weighed, 100 mL of pre-cooled acetone (80%, v / v) is added, and homogenized with a homogenizer (12000 rpm, 1 min, repeated three times). The homogenate is filtered and concentrated using a rotary evaporator (45 rpm, 45°C), and then made up to 25 mL with distilled water. Each sample is extracted three times, and the extract is stored at -20°C for subsequent determination.

[0030] The total phenolic content in mung bean sprouts is determined by the Folin-Ciocalteu colorimetric method, and each sample is determined three times. The results are expressed as mg gallic acid equivalents per 100 g of fresh mung bean sprouts (mg GAE / 100 g FW). The polyphenol components in mung bean sprouts are qualitatively and quantitatively analyzed by high performance liquid chromatography, and the results are expressed as the content of μg polyphenol compounds per gram of fresh mung bean sprouts (μg / g FW), (n = 3).

[0031] Determination of oxygen radical absorbance capacity (ORAC):

[0032] The total antioxidant capacity of mung bean sprouts was evaluated by measuring the oxygen radical absorbance capacity of polyphenol extracts. The results were expressed as mmol Troloxl (TE) equivalents per 100 g of fresh mung bean sprouts (mmol TE / 100 g FW), (n = 3).

[0033] Data analysis:

[0034] The data were analyzed using IBM SPSS 25.0 software. Each sample was replicated three times, and the data were reported as mean ± standard deviation (mean ± SD).

[0035] Results and analysis:

[0036] 1) Effects of blue light and methyl salicylate on the total phenolic content of mung bean sprouts

[0037] The changes in the total phenolic content of mung bean sprouts under the combined treatment of blue light and methyl salicylate are shown in Appendix Figure 2 A. In the dark group, the total phenolic content in D0 was 73.84 ± 1.83 mg GAE / 100 g FW, and there was no significant change in the total phenolics with the change of the concentration of methyl salicylate applied, indicating that the application of methyl salicylate solution alone could not increase the total phenolic content. In addition, by comparing different light quality treatment groups, it was found that the total phenolic content in the blue light group was higher than that in the dark group (1.38 - 1.70 times). By comparing the groups of methyl salicylate solutions with different concentrations under blue light treatment, it was found that the total phenolic content in B500 was the highest (127.14 ± 4.22 mg GAE / 100 g FW). This indicates that 500 μM / L methyl salicylate solution can further increase the total phenolic content of mung bean sprouts treated with blue light.

[0038] 2) Effects of blue light and methyl salicylate on the polyphenol content of mung bean sprouts

[0039] The changes in the content of polyphenol components in mung bean sprouts under the combined treatment of blue light and methyl salicylate are shown in Table 1. Five polyphenol monomers were detected in mung bean sprouts by HPLC, and the contents from high to low were caffeic acid, rutin, 7-hydroxycoumarin, vanillic acid, and genistin. Among them, caffeic acid, 7-hydroxycoumarin, and rutin responded positively to blue light. In the dark group, high concentrations of methyl salicylate could inhibit the accumulation of caffeic acid and vanillic acid in mung bean sprouts. In the blue light group, it was found that high concentrations of methyl salicylate could promote the accumulation of polyphenols in mung bean sprouts, and the polyphenol accumulation was most obvious in the 500 μM / L methyl salicylate treatment group, indicating that methyl salicylate and blue light had a good synergistic effect on polyphenol accumulation.

[0040] Table 1 Effects of Blue Light and Methyl Salicylate on the Polyphenol Composition and Content of Mung Bean Sprouts (μg / g FW)

[0041]

[0042] Note: Different letters in the same column indicate significant differences at p < 0.05

[0043] 3) Effects of Blue Light and Methyl Salicylate on the Oxygen Radical Absorbance Capacity of Mung Bean Sprouts

[0044] The changes in the oxygen radical absorbance capacity (ORAC value) of mung bean sprouts under the combined treatment of blue light and methyl salicylate are shown in Appendix Figure 2 B. In the dark group, the ORAC value of mung bean sprouts was consistent with the corresponding total phenol results, and there were no significant changes. Among them, the ORAC value of the D0 group was 1.25 ± 0.02 mmol TE / 100 g FW, which indicated that applying methyl salicylate solution under full-dark growth conditions could not improve the total antioxidant capacity of mung bean sprouts. By comparing the total phenol content of mung bean sprouts under different light conditions, it was found that the ORAC value of the blue light group was 1.4 - 1.7 times that of the dark group, and the ORAC value of B500 in the blue light group was the highest (2.22 ± 0.03 mmol TE / 100 g FW), significantly higher than that of B0 and B250. These results indicated that single blue light treatment improved the total antioxidant capacity of mung bean sprouts, and high-concentration methyl salicylate solution synergistically with blue light could further improve the total antioxidant capacity of mung bean sprouts.

[0045] Therefore, the combined treatment of blue light and methyl salicylate improved the total antioxidant capacity of mung bean sprouts, which might be closely related to the increase in polyphenol content.

[0046] It can be seen that in the method of the present invention, blue light increased the total phenol content and total antioxidant capacity in mung bean sprouts, and the three phenolic monomers, caffeic acid, rutin, and 7-hydroxycoumarin, responded actively under blue light and were the phenolic substances mainly accumulated under blue light. Moreover, 500 μM / L methyl salicylate synergistically with blue light treatment of mung bean sprouts could further improve their total phenol content and total antioxidant capacity. The total phenol content and ORAC value of the B500 group were 1.72 times and 1.80 times that of the D0 group, respectively.

[0047] The implementation manners of the present invention are not limited by the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications made without departing from the spirit and principle of the present invention shall be equivalent replacement manners and are all included in the protection scope of the present invention.

Claims

1. A method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate, characterized in that It includes the following steps: S1, screening mung bean seeds; S2, first disinfect the surface of the mung bean seeds selected in step S1 with ethanol, and then wash them clean with water; subject the disinfected and washed mung bean seeds to heat shock; put the mung bean seeds after heat shock into a culture box, add water, and perform cold shock at room temperature to soften the mung bean epidermis and promote the germination rate. Finally, pour out all the water to complete the cold shock; add water to the mung bean seeds that have completed the cold shock again, and put the culture box into an artificial climate chamber; S3, the culture conditions in the artificial climate chamber are: humidity is 90%, temperature is 25°C, and the total culture time is 6 days; the light conditions are: darkness and blue light with λ = 460 - 465 nm, the light duration is 24 h / d, and the mung bean seeds are rinsed with a methyl salicylate aqueous solution by water rinsing and spraying methods successively before and after germination.

2. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 1, characterized in that, In step S1, the screening of mung bean seeds specifically refers to selecting mung bean seeds that are plump, complete, free of pests and diseases, mold, and of the same size.

3. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 1, wherein In step S2, disinfecting the surface of the mung bean seeds with ethanol specifically refers to weighing 30 g of mung bean seeds and disinfecting the surface of the mung bean seeds with 70% ethanol for 0.5 - 1 min.

4. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 1, wherein, In step S2, the heat shock refers to performing heat shock for 25 - 30 s by rinsing with boiling water in a mung bean seed strainer, and the cold shock refers to adding 300 - 400 mL of tap water to the mung bean seeds and performing cold shock for 5 - 6 h at room temperature.

5. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 4, wherein The 6 - hour cold shock at room temperature is carried out under dark conditions.

6. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 1, characterized in that, In step S3, the mung bean seeds are rinsed with a methyl salicylate aqueous solution by water rinsing and spraying methods successively before and after germination specifically refers to: rinsing with tap water for the first four days before the mung bean seeds germinate, and starting from the fifth day, rinsing with a methyl salicylate aqueous solution by spraying method.

7. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 6, wherein, The mung bean seeds are rinsed with 60 mL of tap water for the first four days before germination, and starting from the fifth day, 60 mL of a methyl salicylate aqueous solution is rinsed by spraying method.

8. The method for promoting polyphenol accumulation in mung bean sprouts by treating with blue light combined with methyl salicylate according to claim 7, wherein, The rinsing frequency is 12 h / d, and the concentrations of the methyl salicylate solution are 0, 250, 500, and 1000 μM / L.

9. The method for promoting polyphenol accumulation in mung bean sprouts by using blue light combined with methyl salicylate according to claim 7, wherein In the last two days during the rinsing process with the methyl salicylate aqueous solution, 60 mL of methyl salicylate solutions with different concentrations are sprayed.

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