A method for artificially increasing glucosinolate substances in longan pulp after harvest

Abstract

The present invention belongs to the technical field of fruit and vegetable processing, and discloses a method for artificially increasing the content of glucosinolates in longan pulp after harvest. Specifically, a method for artificially increasing the content of glucosinolates in longan pulp after harvest is disclosed, which includes the following steps: fumigating longan with a SO2 generator; the SO2 generator includes a solid generator and a liquid reaction medium, the solid generator includes benzenesulfonic acid and sodium bisulfite, and the liquid reaction medium includes acetone. By fumigating longan with the SO2 generator, the fumigation can be completed within 20 to 90 minutes, with a fast speed and high efficiency. Moreover, it can significantly increase the content of glucosinolates in the pulp, enhance the nutritional and health care value of longan pulp, and promote benefit increment.

Description

Technical Field

[0001] The present invention belongs to the technical field of fruit and vegetable processing, and particularly relates to a method for artificially increasing the content of glucosinolates in longan pulp after harvesting. Background Art

[0002] Glucosinolate (GLs), also known as thioglucoside, is a sulfur-containing secondary metabolite of plants. It is most abundant in terms of variety and content in cruciferous vegetables. Its core structure is β-D-glucose + sulfonate aldehyde group + amino acid side chain R+. Foods rich in glucosinolates have special flavors (such as umami, bitterness, pungency, etc.) and health-care functions, which are related to the degradation products of glucosinolates. Research shows that when plants contain glucosinolates, they also contain enzymes that degrade glucosinolates, and this enzyme is myrosinase. When plant organs are chopped or chewed, glucosinolates will undergo an enzymatic reaction with myrosinase inside the plant, causing glucosinolates to hydrolyze, thereby generating active substances such as isothiocyanates and nitriles. These metabolites have various physiological functions such as antioxidant, anti-cancer, and regulation of intestinal flora.

[0003] Glucosinolates have received extensive attention due to their important biological functions. There are many types of glucosinolates. Currently, some bioactive substances produced by the hydrolysis of glucosinolates beneficial to the human body have functions such as antioxidant, anti-aging, cancer prevention and anti-cancer, and play an important role in human health. For example, sulforaphane is an isothiocyanate (SFN), phenethyl isothiocyanate (PEITC), etc. formed by the catalytic hydrolysis of 4-methylsulfinylbutyl glucosinolate (Glucoraphanin, GR, belonging to aliphatic glucosinolates) by myrosinase. It can regulate cell signaling pathways and epigenetic variations, up-regulate phase II detoxifying enzymes / antioxidant enzymes, reduce inflammatory mediators, and induce the expression of genes that inhibit tumors, promote apoptosis, antioxidant, and anti-inflammatory, thereby reversing and inhibiting cancer formation.

[0004] The content of glucosinolates in plants is not only regulated by plant genotypes but also affected by plant growth environmental factors. Biological factors such as insect feeding and pathogen infection, abiotic factors such as light, temperature, water, mineral elements, and gases, and exogenous plant growth regulators will all affect the content of glucosinolates in plants. The above research mainly focuses on the regulation of the growth period of cruciferous plants. There have been no relevant reports on fruits so far. Therefore, whether it is cruciferous plants or other plants or fruits, the content of glucosinolates mainly depends on varieties and planting management to regulate their production. After product harvesting, there have been no relevant reports on how to increase the content of glucosinolates in products and enhance the health-care functions of products through artificial means.

[0005] Longan is one of the precious fruit varieties in the tropical and subtropical regions of southern China. It can be used both as medicine and food, with good nutritional and health care functions, and is deeply loved by consumers at home and abroad. Summary of the Invention

[0006] The purpose of the first aspect of the present invention is to provide a method for artificially increasing the glucosinolate content in postharvest longan pulp.

[0007] The purpose of the second aspect of the present invention is to provide the application of the method of the first aspect of the present invention.

[0008] In order to achieve the above purposes, the technical solutions adopted by the present invention are as follows:

[0009] In the first aspect of the present invention, a method for artificially increasing the glucosinolate content in postharvest longan pulp is provided, including the following steps: fumigating longan with a SO 2 generator; the SO 2 generator includes a solid generator and a liquid reaction medium. The solid generator includes benzenesulfonic acid and sodium bisulfite, and the liquid reaction medium includes acetone.

[0010] Preferably, the mass ratio of the longan to the solid generator is 100-500:1; further preferably 150-500:1.

[0011] Preferably, the mass-volume ratio of the solid generator to the liquid reaction medium is 1:1-3 (g / mL).

[0012] More preferably, the mass-volume ratio of the solid generator to the liquid reaction medium is 1:1-2 (g / mL).

[0013] Even more preferably, the mass-volume ratio of the solid generator to the liquid reaction medium is 1:1-1.5 (g / mL).

[0014] Preferably, the mass ratio of benzenesulfonic acid to sodium bisulfite is 1:0.5-1.

[0015] More preferably, the mass ratio of benzenesulfonic acid to sodium bisulfite is 1:0.5-0.8.

[0016] Even more preferably, the mass ratio of benzenesulfonic acid to sodium bisulfite is 1:0.6-0.8.

[0017] Preferably, the acetone is an acetone aqueous solution with a volume fraction of 50v / v%-85v / v%.

[0018] More preferably, the acetone is an acetone aqueous solution with a volume fraction of 50v / v%-80v / v%.

[0019] Further preferably, the acetone is an aqueous acetone solution of 65 v / v% to 80 v / v%.

[0020] Preferably, when the reaction of the SO 2 generating agent is complete, continue fumigating for 20 to 90 min.

[0021] Further preferably, when the reaction of the SO 2 generating agent is complete, continue fumigating for 30 to 90 min.

[0022] Preferably, it is placed in a trapezoidal plastic turnover basket with holes on all six sides, large at the top and small at the bottom, and stacked in a pyramid shape in the fumigation chamber.

[0023] Preferably, the thickness of the fruit pile does not exceed 20 - 25 cm.

[0024] Preferably, after the fumigation, the excess SO 2 gas is removed.

[0025] Preferably, the longan after fumigation is stored at -1 to 1°C.

[0026] Preferably, the fumigation is carried out in a closed space, and no more than 4000 kg of longan fruits are placed in every 50 m 3 space.

[0027] The second aspect of the present invention lies in providing the application of the method of the first aspect of the present invention in any one of (1) to (4);

[0028] (1) increasing the content of glucosinolate substances in fruits;

[0029] (2) improving the nutritional value of fruits;

[0030] (3) color protection and fresh preservation of fruits;

[0031] (4) preservation of fruits.

[0032] Preferably, the fruits include common fruits on the current market, including but not limited to: longan, litchi, grape, ginger, water chestnut, etc.

[0033] The beneficial effects of the present invention are:

[0034] The present invention fumigates longan with an SO 2 generating agent, and the fumigation can be completed within 20 to 90 min, with a fast speed and high efficiency. Moreover, it can significantly increase the content of glucosinolate substances in the pulp, enhance the nutritional and health care value of longan pulp, and promote benefit increment.

[0035] Compared with SO 2Compared with the fresh-keeping paper (ZL201610227848.7) and the treatment of longan fruits by sulfur combustion fumigation, the present invention uses a solid generator different from the longan fresh-keeping paper, and instantaneously generates a large amount of SO 2 gas through a liquid reaction, which quickly acts on the fruits within 20 - 90 minutes. Not only is its safety and controllability higher than that of sulfur combustion treatment, but its fumigation effect is also faster than that of the SO 2 fresh-keeping paper treatment, and the acetone in the liquid medium can be recycled after recovery.

[0036] The low-temperature storage temperature of ordinary longan fruits is not lower than 4 - 5°C, otherwise chilling injury will occur, and the storage life is about 20 - 25 days. However, the fruits fumigated by the method provided by the present invention can be stored at a lower temperature (-1 - 1°C), greatly extending the storage life (60 - 90 days), providing technical guarantee for the substantial extension of the storage life of fresh longan fruits.

[0037] The present invention improves the content of glucosinolate substances in longan pulp through rapid post-harvest treatment. Compared with measures such as gene expression and cultivation management before harvest, first, the increase in glucosinolate substances in the pulp is large; second, the time is short and the efficiency is high; third, after the fruits are collected, they are centrally processed, with a large processing volume and low cost. Description of the Drawings

[0038] Figure 1 Relative contents of differential metabolites of glucosinolates in longan pulp treated with CK0d and CK35d.

[0039] Figure 2 Relative contents of differential metabolites of glucosinolates in longan pulp treated with CK0d, TS1_35d and TS2_35d.

[0040] Figure 3 Relative contents of differential metabolites of glucosinolates in longan pulp treated with CK35d, TS1_35d and TS2_35d. Detailed Embodiments

[0041] The present invention will be described in detail below in conjunction with specific embodiments, but the scope of the present invention is not limited.

[0042] The materials, reagents, etc. used in this embodiment are materials and reagents obtained from commercial channels unless otherwise specified.

[0043] Example 1

[0044] A method for artificially increasing the content of glucosinolate substances in post-harvest longan pulp, comprising the following steps:

[0045] (1) Fruit harvesting: Select mature fruits with few pests and diseases, no pollution, drug residues meeting the standard requirements, and appearance and internal quality reaching the inherent characteristics of Caopuzhong longan for harvesting. Harvest on September 17 and arrive in Guangzhou by express on September 18.

[0046] (2) Fruit selection and packaging: Cut the longan fruit spikes into small spikes or single fruits with soft branches, 15 - 20 cm long, and place them in trapezoidal plastic turnover baskets with holes on six sides, larger at the top and smaller at the bottom. The thickness of the fruit pile should not exceed 25 cm. After packing, cover the baskets. Each box contains 10 jin, a total of 5 baskets, 25 kg in total.

[0047] (3) Stacking in the fumigation chamber: Stack the packaged fruit baskets in a pyramid shape in a pre - prepared self - made plexiglass fumigation chamber with dimensions of 1.5×1.5×1.5 cm 3 . Stack them into stacks, with a distance of 20 - 30 cm between stacks, a gap of 30 - 50 cm between the stack and the ceiling and surrounding walls, and an air - separating board with a height of 15 - 20 cm placed between the stack and the ground. The ratio of the stack volume to the fumigation chamber volume should not be higher than 2 / 3.

[0048] (4) Reaction to generate SO 2 Fumigation: Place an open stainless - steel container on the tray of a magnetic stirrer, then pour in the fully - mixed solid - state generator (200 g of benzenesulfonic acid + 130 g of sodium bisulfite), and then add 495 mL of reaction medium (80 v / v% acetone aqueous solution) (low - dose treatment). Turn on the magnetic stirrer to assist dissolution for 0.5 - 1.0 min. Close the fumigation chamber. After the reaction is complete, continue fumigation for 30 min. During the fumigation process, use a gas flow or circulation device to promote the closed - loop circulation of SO 2 gas in the fumigation chamber to facilitate uniform absorption by the fruits.

[0049] (5) End of fumigation: Start the SO 2 gas purification facility to remove the excess SO 2 gas in the fumigation chamber. After cleaning, open the closed door of the fumigation chamber. Store the fumigated longan fruits under the condition of 1℃ for no more than 90 days.

[0050] (6) SO 2 residue: According to the regulations of the industry standard of the Ministry of Agriculture (《NY 1440 - 2007 Limit of Sulfur Dioxide Residue in Tropical Fruits》), the content of SO 2 in the longan pulp after fumigation should not exceed 30 mg / kg (the determination method refers to the pararosaniline hydrochloride method (pararosaniline method) in the national standard GB / T5009.34—2022), meeting the fresh - food standard specifications.

[0051] Example 2

[0052] A method for artificially increasing the glucosinolate content in post-harvest longan pulp, comprising the following steps:

[0053] (1) Fruit harvesting: Select mature fruits with few pests and diseases, no pollution, drug residues meeting the standard requirements, and appearance and internal quality reaching the inherent characteristics of Caopuzhong longan for harvesting. Harvest on September 17th and arrive in Guangzhou by express on September 18th.

[0054] (2) Fruit selection and packaging: Cut the longan fruit spikes into small spikes or single fruits with soft branches, 15 - 20 cm long, and place them in a trapezoidal plastic turnover basket with holes on all six sides, larger at the top and smaller at the bottom. The thickness of the fruit pile should not exceed 25 cm. After loading, cover it. Each box contains 10 catties, with a total of 5 baskets, totaling 25 kg.

[0055] (3) Stacking in the fumigation chamber: Stack the packaged fruit baskets in a pyramid shape in a pre-prepared self-made plexiglass fumigation chamber with dimensions of 1.5×1.5×1.5 cm 3 . Stack them into stacks, with a distance of 20 - 30 cm between stacks, a gap of 30 - 50 cm between the stack and the ceiling and surrounding walls, and a spacer board with a height of 15 - 20 cm placed between the stack and the ground. The ratio of the stack volume to the fumigation chamber volume should not be higher than 2 / 3.

[0056] (4) Reaction to generate SO 2 Fumigation: Place an open stainless-steel container on the tray of a magnetic stirrer, then pour in the fully mixed solid generator (300 g of benzenesulfonic acid + 195 g of sodium bisulfite), and then add 742 mL of reaction medium (80 v / v% acetone aqueous solution) (for high-dose treatment). Turn on the magnetic stirrer to assist dissolution for 0.5 - 1.0 min. Close the fumigation chamber. After the reaction is complete, continue fumigation for 30 min. During the fumigation process, use a gas flow or circulation device to promote the closed circulation of SO 2 gas in the fumigation chamber to facilitate uniform absorption by the fruits.

[0057] (5) End of fumigation: Start the SO 2 gas purification facility to remove the excess SO 2 gas in the fumigation chamber. After cleaning, open the closed door of the fumigation chamber. Store the fumigated longan fruits at 1°C for no more than 90 days.

[0058] (6) SO 2 residue: According to the regulations of the industry standard of the Ministry of Agriculture (《NY 1440—2007 Limit of Sulfur Dioxide Residue in Tropical Fruits》), the content of SO 2 in the longan pulp after fumigation should not exceed 30 mg / kg (the determination method refers to the pararosaniline hydrochloride method (pararosaniline method) in the national standard GB / T5009.34—2022), meeting the fresh food standard specifications.

[0059] Comparative Example 1

[0060] A method for artificially increasing the glucosinolate content in longan pulp after harvest, comprising the following steps:

[0061] (1) Fruit harvesting: Select mature fruits with few pests and diseases, no pollution, drug residues meeting the standard requirements, and appearance and internal quality reaching the inherent characteristics of Caopuzhong longan for harvesting. Harvest on September 17th and arrive in Guangzhou by express on September 18th.

[0062] (2) Fruit selection and packaging: Cut the longan ear into small spikes or single fruits with soft branches 15 - 20 cm long, place them in a trapezoidal plastic turnover basket with holes on six sides, large at the top and small at the bottom. The thickness of the fruit pile does not exceed 25 cm. After loading, cover it. Each box contains 10 catties, a total of 5 baskets, and a total of 25 kg.

[0063] (3) Stacking in the fumigation chamber: Stack the packaged fruit baskets in a pyramid shape in a pre-prepared self-made plexiglass fumigation chamber of 1.5×1.5×1.5 cm 3 . Stack them into stacks, with a distance of 20 - 30 cm between stacks, a gap of 30 - 50 cm between the stack and the ceiling and surrounding walls, and an air separation board with a height of 15 - 20 cm placed between the stack and the ground. The ratio of the stack volume to the fumigation chamber volume is not higher than 2 / 3.

[0064] (4) Store under the condition of 1℃ for no more than 90 days.

[0065] (4) SO 2 Residue amount: According to the regulations of the industry standard of the Ministry of Agriculture (Limit of Sulfur Dioxide Residue in Tropical Fruits, NY 1440 - 2007), the SO 2 content in longan pulp after fumigation does not exceed 30 mg / kg (the determination method refers to the pararosaniline hydrochloride method (parafuchsin method) in the national standard GB / T5009.34—2022), meeting the fresh food standard specifications.

[0066] Effect Example

[0067] 1. Determination of the SO 2 content in the pulp

[0068] Take out the longans stored for 35 days in Examples 1 - 2 and Comparative Example 1 (CK35d - longan stored for 35 days in Comparative Example 1, TS1_35d - longan stored for 35 days in Example 1, TS2_35d - longan stored for 35 days in Example 2), observe whether the peel color has turned brown, and use the pararosaniline hydrochloride method (parafuchsin method) in the national standard GB / T 5009.34—2022 to determine the SO 2 content in the pulp.

[0069] When the longan fruits were taken out after 35 days of storage, the good fruit rate of the longan fruits in Comparative Example 1 after 35 days of storage was 75.41%, and most of the fruit peels turned brown; while the good fruit rates of the longan fruits in Example 1 and Example 2 after 35 days of storage were 96.82 and 100% respectively, the fruit peels were yellow, and the good fruits had no browning; the SO 2 contents in the pulp of CK35d, TS1_35d and TS2_35d were 1.92 mg / kg, 12.58 mg / kg and 15.26 mg / kg respectively, all of which did not exceed 30 mg / kg.

[0070] 2. Comparison of relative contents of thioglycoside metabolites in longan

[0071] Take out the longan fruits stored for 35 days in Examples 1-2 and Comparative Example 1 (CK35d - longan fruits stored for 35 days in Comparative Example 1, TS1_35d - longan fruits stored for 35 days in Example 1, TS2_35d - longan fruits stored for 35 days in Example 2). Evenly select 60 good fruits in each fruit box, carefully peel the pulp, take every 20 fruits as 1 repeat, with a total of 3 repeats. After quickly freezing and crushing with liquid nitrogen, store them in a -80 °C ultra-low temperature refrigerator. Take another untreated (unstored) longan in Comparative Example 1 as the control before treatment (CK0d). The longan pulp samples preserved by liquid nitrogen treatment were submitted to Wuhan Metware Biotechnology Co., Ltd. to entrust the determination of the relative contents of thioglycoside metabolites in 4 samples, and perform differential analysis to screen out the changes of related metabolites before and after treatment and before and after storage.

[0072] The results showed that a total of 19 differential metabolites between CK0d and CK35d were obtained through analysis, 17 were up-regulated and 2 were down-regulated; among them, 2 were thioglycosides, 3 were indole alkaloids, and the others were sulfur-containing amino acids and their derivatives ( Figure 1 ). It shows that during storage, macromolecular sulfur-containing proteins are degraded into small-molecule amino acid substances, while the changes in thioglycoside substances are very small.

[0073] A total of 26 differential metabolites between CK0d, TS1_35d and TS2_35d were obtained through analysis, 24 were up-regulated and 2 were down-regulated. Among them, 10 were thioglycoside substances, 15 were sulfur-containing amino acids and their derivatives, and 1 was indole alkaloid ( Figure 2 ). Among the three treatments, the content of up-regulated metabolites in the longan fruits treated in Example 2 was higher than that in Example 1, and Example 1 was higher than CK0, indicating that after 35 days of storage, the contents of up-regulated thioglycoside substances and amino acids and their derivatives in the sulfur-treated pulp were significantly higher than those of the control pulp before storage after harvesting, and the increasing effect of the treatment with an appropriate high amount of generator was higher than that of the low amount treatment.

[0074] A total of 20 differential metabolites were obtained between CK35d, TS1_35d and TS2_35d, 17 of which were up-regulated and 3 were down-regulated. Among them, 9 were glucosinolates and 11 were amino acids and their derivatives ( Figure 3 Among the three treatments, the content of up-regulated metabolites in Example 2 was higher than that in Example 1, and that in Example 1 was higher than that in Comparative Example 1, indicating that after 35 days of storage, the types and contents of glucosinolates in the sulfur-treated pulp were significantly higher than those in the non-sulfur-treated pulp, and the increasing effect of the high-amount generator treatment was higher than that of the low-amount treatment.

[0075] 3. Effective effect of sulfur treatment on the content of glucosinolates in longan pulp

[0076] By further analyzing SO 2 The differential metabolites effectively upregulated in the longan pulp were treated. As shown in Table 1, there were 14 differential metabolites effectively upregulated, among which the first 10 metabolites were produced in the sulfur-treated pulp and were still significantly higher than the non-sulfur treatment (control CK0d) until 35 days of storage, indicating that the production of these substances was closely related to the sulfur treatment. The difference between the last 4 metabolites before and after storage in Comparative Example 1 (CK0d_vs_CK35d) was not obvious, but the difference between the last 4 metabolites before and after storage in the sulfur-treated fruit (CK0d_vs_TS2_35d) was obvious, indicating that these 4 metabolites were also closely related to the sulfur treatment. Among the 14 target differential metabolites obtained, 10 belonged to glucosinolates, and aliphatic glucosinolates were the main substances, 3 belonged to amino acids and their derivatives, and 1 belonged to indole alkaloids, all of which were upregulated metabolites. In addition, the relative contents of the first 10 glucosinolates in Table 1 were all more than 100% higher than CK0d and CK35d after 35 days of storage (TS2_35d), showing significant differences; the relative contents of the last 4 glucosinolates were not significantly different from CK35d (the increase rate was less than 100%) after 35 days of storage (TS2_35d), but were still higher than CK0d (the increase rate was higher than 100%). It can be seen that compared with the fruit without sulfur treatment, the sulfur-treated fruit not only greatly increased the content of glucosinolates in the longan pulp, but also increased the content of sulfur-containing amino acids and their derivatives. All glucosinolates are synthesized from amino acids, aliphatic glucosinolates are derived from methionine (methionine), aromatic glucosinolates are derived from phenylalanine, and indole glucosinolates are derived from tryptophan. Therefore, compared with the fruit without sulfur treatment, the sulfur-treated longan will emit a special fragrance and have a different flavor, which should be related to the formation of a variety of glucosinolates. At the same time, because it has certain health functions, the nutritional value of sulfur-treated longan may be higher than that of non-sulfur treatment.

[0077] Table 1 Screening of effective differential metabolites after sulfur treatment (all up-regulated) (relative content)

[0078]

[0079]

[0080] Note: TURE means that the fold change of metabolite content in the experimental group (longan treated in Example 1 and Example 2) and the control group (longan treated in Comparative Example 1) is ≥2, that is, the difference is more than 2 times (relative content increase rate ≥100%), then the difference is considered significant; otherwise, it is considered not significant, FALSE.

[0081] The embodiments of the present invention have been described in detail above in conjunction with the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various changes can be made without departing from the gist of the present invention. In addition, without conflict, the embodiments of the present invention and the features in the embodiments can be combined with each other.

Claims

1. A method for artificially increasing the glucosinolate content in longan pulp after harvest, comprising the following steps: Using SO 2 Generating agent to fumigate longan; the SO 2 Generating agent includes a solid generating agent and a liquid reaction medium. The solid generating agent includes benzenesulfonic acid and sodium bisulfite, and the liquid reaction medium includes acetone; When the SO 2 generator reaction is complete, continue fumigation for 30 - 90 minutes.

2. The method according to claim 1, characterized in that, the mass-volume ratio of the solid generating agent to the liquid reaction medium is 1:1 to 3.

3. The method according to any one of claims 1 to 2, characterized in that, the longan is stacked into a trapezoidal fruit pile before fumigation, and the trapezoid has an upper base larger than the lower base.

4. The method according to claim 3, characterized in that, the thickness of the fruit pile does not exceed 25 cm.

5. The method according to claim 4, characterized in that, the mass ratio of benzenesulfonic acid to sodium bisulfite is 1:0.5 to 1.

6. The method according to claim 4 or 5, characterized in that, the acetone is an acetone aqueous solution of 50 v / v% to 85 v / v%.

7. The method according to claim 6, wherein the fumigation is carried out in a closed space, and no more than 4000 kg of longan fruits are placed per 50 m 3 space.

8. The application of the method according to any one of claims 1 to 7 in any one of (1) to (3); (1) improving the nutritional value of longan; (2) color protection and fresh preservation of longan; (3) preservation of longan.

Images