Method for inhibiting browning of fresh-cut Chinese yam through combined treatment of cold plasma and hydrogen sulfide and application

Abstract

The invention discloses a method for inhibiting browning of fresh-cut Chinese yam through combined treatment of cold plasma and hydrogen sulfide and application, and belongs to the technical field of postharvest preservation of agricultural products. Exposing the fresh-cut Chinese yam to cold plasma for treatment; soaking the treated fresh-cut Chinese yam in a NaHS solution serving as a hydrogen sulfide donor, and taking out and draining after soaking is finished; and putting into a glass dish, and refrigerating and storing. The browning inhibition method provided by the invention effectively solves the problem that the fresh-cut Chinese yam is easy to brown, prolongs the shelf life of the fresh-cut Chinese yam, retains the special nutritional value of the Chinese yam, and is green, safe, simple and easy to implement.

Description

Technical Field

[0001] The invention belongs to the technical field of post-harvest preservation of agricultural products, and particularly relates to a method for inhibiting browning of fresh-cut yams through combined treatment with cold plasma and hydrogen sulfide, and application thereof. Background Art

[0002] Chinese yam (Dioscorea opposita) is an annual or perennial twining herbaceous vine in the Dioscoreaceae family that produces tubers and is widely consumed as a food. Cultivated in China, Japan, and South Korea, it is an important dual-purpose crop for both food and medicine. In Asia, Chinese yam is often used as a dietary supplement and as a herbal remedy. Chinese yam is also used in traditional medicine to treat diabetes and tumors, protect liver and kidney function, and boost the immune system. It contains a variety of nutrients, including sapogenins, saponins, starch, mucopolysaccharides, protein, and amino acids, and market demand continues to grow.

[0003] With the accelerating pace of modern life and rising consumer demand for healthy eating, fresh-cut fruits and vegetables are becoming a popular segment of the food industry due to their convenience, nutritional value, and freshness. Fresh-cut yams, a prime example of this, retain their natural nutrients while utilizing pre-processing techniques to meet consumer demand for immediate consumption, aligning with the contemporary dietary philosophy of "efficiency and health coexist." Compared to whole yams, the cutting process involved in processing fresh-cut yams disrupts their tissue structure and rapidly activates metabolic reactions within the tissue, leading to a rapid decline in quality, significantly shortening their shelf life, and reducing their edible and commercial value.

[0004] Currently, methods for inhibiting browning mainly include physical (low temperature, modified atmosphere packaging), chemical (soaking in ascorbic acid, citric acid) and biological (coating with plant extracts), but there are still problems such as nutrient loss, residual agents, high cost or complex operation. For example, chemical treatment may reduce the polyphenol content of yam, while physical methods have high equipment requirements and are difficult to popularize. Literature (such as CN119111620A) discloses antibacterial technology for treating fruits and vegetables with cold plasma alone, but its inhibition rate on browning enzymes is insufficient (<50%) and it cannot solve the texture deterioration caused by dehydration.

[0005] Therefore, developing an efficient and safe collaborative fresh-cut yam preservation technology has extremely high practical and economic value. Summary of the Invention

[0006] [Technical Issues]

[0007] Existing methods for inhibiting browning of fresh-cut yam have problems such as nutrient loss, drug residue, high cost or complex operation, and cannot meet the needs of effectively inhibiting browning of fresh-cut yam while being green, safe and low-cost.

[0008] [Technical solution]

[0009] In order to solve the above problems, the present invention provides a method for inhibiting browning of fresh-cut yam by combining cold plasma and hydrogen sulfide treatment. The method of the present invention is simple to operate, does not have excessively high technical requirements, and can achieve effective detection while ensuring accuracy.

[0010] A first object of the present invention is to provide a method for inhibiting browning of fresh-cut yam, comprising the steps of:

[0011] (1) Spread a single layer of yam slices and treat them with cold plasma at a voltage of 300-500 V for 10-120 s;

[0012] (2) The yam slices treated with cold plasma were soaked in a NaHS solution with a concentration of 0.5 to 8 mmol / L for 1 to 30 min and then drained to obtain yam slices with inhibited browning.

[0013] In one embodiment, in step (1), the yam slices are treated with cold plasma at a voltage of 400 to 500 V for 30 to 120 s; the plasma frequency used in the cold plasma treatment is 3000 Hz.

[0014] In one embodiment, in step (2), the yam slices are soaked in a NaHS solution with a concentration of 2 to 4 mmol / L for 5 to 30 minutes.

[0015] In one embodiment, the thickness of the yam slices in step (1) is 3 to 7 mm.

[0016] In one embodiment, the ratio of the yam tablets to the NaHS solution in step (2) is 150-200 g: 25-30 mL.

[0017] In one embodiment, the dried product in step (2) is stored at 0-4°C.

[0018] In one embodiment, the yam slices are obtained by slicing iron stick yam.

[0019] In one embodiment, the browning-inhibited yam slices have a refrigerated shelf life of 10 to 12 days.

[0020] The second object of the present invention is to provide a method for inhibiting the growth of fresh-cut yam while improving the texture of yam and increasing the content of polyphenols and polysaccharides, comprising the steps of:

[0021] (1) Spread a single layer of yam slices and treat them with cold plasma at a voltage of 300-500 V for 10-120 s;

[0022] (2) The yam slices treated with cold plasma were soaked in a NaHS solution with a concentration of 0.5 to 8 mmol / L for 1 to 30 min and then drained to obtain yam slices with inhibited browning.

[0023] In one embodiment, in step (1), the yam slices are treated with cold plasma at a voltage of 400 to 500 V for 30 to 120 s; the plasma frequency used in the cold plasma treatment is 3000 Hz.

[0024] In step (2), the yam slices are soaked in a NaHS solution with a concentration of 2 to 4 mmol / L for 5 to 30 minutes.

[0025] In one embodiment, the thickness of the yam slices in step (1) is 3-7 mm; and in step (2), the ratio of the yam slices to the NaHS solution is 150-200 g: 25-30 mL.

[0026] In one embodiment, the dried product in step (2) is stored at 0-4°C.

[0027] In one embodiment, the yam slices are obtained by slicing iron stick yam.

[0028] In one embodiment, the browning-inhibited yam slices have a refrigerated shelf life of 10 to 12 days.

[0029] The third object of the present invention is to provide the application of any of the above methods in preserving fresh-cut yams.

[0030] Beneficial effects of the present invention:

[0031] (1) The method provided herein for inhibiting browning of fresh-cut yams by combining cold plasma and hydrogen sulfide treatment effectively addresses the problem of browning in fresh-cut yams and extends their shelf life. Compared to plasma treatment or immersion in a hydrogen sulfide donor NaHS solution alone, the combined cold plasma and hydrogen sulfide treatment of fresh-cut yams achieves unexpected technical benefits. The combined treatment allows for refrigerated preservation of fresh-cut yams for up to 10 to 12 days.

[0032] (2) Soak fresh-cut fruits and vegetables in a solution of hydrogen sulfide donor NaHS. The solution can effectively slow down the diffusion rate of oxygen during soaking. At the same time, after being taken out and drained, H2S inhibits the enzyme active center through sulfhydryl modification (-SSH) and activates the endogenous antioxidant system (SOD and CAT activity increases by ≥30%), reducing oxidative plasma, degrading the generated quinone browning products such as melanin, and oxidizing phenolic substrates, reducing the subsequent browning reaction substrates, and achieving a better color protection effect. In addition, H2S can be completely volatilized at low concentrations, without the allergenic risk of sulfite preservatives. At the same time, it inhibits the activity of pectinase and cellulase, slows down the decomposition of cell walls, and maintains the hardness of yam. It reduces lipid peroxidation, avoids the generation of odor substances such as aldehydes, and maintains a sweet flavor. The reactive oxygen species (·OH, O3) generated by cold plasma disrupt the hydrogen bond network of PPO / POD, inducing a transition from the α-helix to the β-sheet conformation of the enzyme protein, thereby destroying the secondary and tertiary structures of polyphenol oxidase and altering the surrounding microenvironment, thereby reducing its activity and maintaining the color of fruit and vegetable slices. Furthermore, the active ingredients in cold plasma can kill microorganisms on the surface of apple slices, achieving a disinfecting and sterilizing effect, thereby extending the shelf life of fresh-cut fruits and vegetables and facilitating long-distance transportation.

[0033] (3) The preservation method provided by the present invention is green, safe, simple and easy to use, and meets the high safety standards of modern food processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 Graphs showing the browning of yam (A) and the changes in PAL enzyme activity (B) in Example 1 of the present invention and Comparative Examples 1 to 4;

[0035] Figure 2 Graphs showing the browning of yam (A) and the changes in PAL enzyme activity (B) in Examples 1 and 2 of the present invention;

[0036] Figure 3 Graphs showing the browning of yam (A) and the changes in PAL enzyme activity (B) in Examples 1 and 3 of the present invention;

[0037] Figure 4 Graphs showing the browning of yam (A) and the changes in PAL enzyme activity (B) in Examples 1 and 4 of the present invention;

[0038] Figure 5 Graphs showing the browning of yam (A) and the changes in PAL enzyme activity (B) in Examples 1 and 5 of the present invention;

[0039] Figure 6 Graphs showing the browning of yam in Example 1 of the present invention and Comparative Example 5 (A) and the change in PAL enzyme activity (B). DETAILED DESCRIPTION

[0040] The following describes preferred embodiments of the present invention. It should be understood that the embodiments are for better explanation of the present invention and are not intended to limit the present invention.

[0041] Test method:

[0042] (1) Determination of L value, a value, b value, and browning degree of fresh-cut yam

[0043] The surface color difference of the samples was measured using a colorimeter, and the L*, a*, and b* values were recorded. The browning degree of the samples was measured before and after three days of storage. Each sample group was measured in parallel three times. The L* value represents the lightness and darkness, the a* value represents the redness and greenness, the b* value represents the yellowness and blueness, and the BI value represents the browning degree. The BI calculation formula is as follows.

[0044] x=(a*+1.75×L*) / (5.645×L*+a*-3.012×b*)

[0045] BI=100×(x-0.31) / 0.172

[0046] (2) Extraction and measurement of PAL activity

[0047] Phenylalanine ammonia lyase (PAL) activity was measured using a spectrophotometric assay kit. Approximately 0.2 g of tissue was added to 1 mL of the extract, homogenized on ice, and centrifuged at 12,000 rpm for 10 minutes at 4°C. The supernatant was collected and placed on ice for analysis. PAL enzyme activity in the supernatant was measured using the PAL assay kit. All procedures were performed according to the kit instructions, and each test was repeated three times.

[0048] (3) Extraction and measurement of total phenols

[0049] A polyphenol detection kit (spectrophotometric method) was used for determination. Approximately 0.1 g of fresh sample was weighed, ground, and then added to 1.5 mL of 60% ethanol. Extracted with shaking at 60°C for 2 h (if evaporation occurs, the volume was adjusted to 1.5 mL with 60% ethanol). Centrifuged at 12,000 rpm for 10 min at 25°C, and the supernatant was collected for analysis. The polyphenol content in the supernatant was determined using a polyphenol detection kit. All procedures were performed according to the kit instructions, and each test was repeated three times.

[0050] (4) Determination of polysaccharide content

[0051] Fresh-cut yam slices were freeze-dried at -20°C and ground into a powder. A certain amount of yam powder was weighed and added to distilled water at a 1:10 mass ratio. Extraction was performed at 85°C, pH 8-9 for 1 hour. 20 g of yam slurry was placed in a centrifuge tube and centrifuged (12,000 rpm, 22°C) for 15 minutes. The supernatant was added to 20 mL of 70% ethanol, shaken, and centrifuged (12,000 rpm, 22°C) for 15 minutes. The supernatant was aspirated and the precipitate was freeze-dried to obtain crude polysaccharides. 20 mL of deionized water was added to dissolve the crude polysaccharide to obtain the polysaccharide extract to be tested. A standard curve was constructed using glucose as the standard substance, plotting glucose concentration on the horizontal axis and absorbance on the vertical axis. Use a pipette to transfer 0.6 mL of the polysaccharide extract to a 10 mL test tube. Add 1.2 mL of a 50 g / L phenol solution and mix thoroughly. Add 5 mL of concentrated hydrochloric acid, bring the volume to the mark, and vortex to mix thoroughly. Let the solution stand for 5 minutes, then heat in an 85°C water bath for 15 minutes. After cooling to room temperature, allow the solution to stand for 30 minutes. Use distilled water as a blank control and measure the absorbance at 490 nm. Calculate the polysaccharide concentration based on the standard curve, and thus the polysaccharide content in fresh-cut yam.

[0052] (5) Texture determination

[0053] The puncture test was used to determine the texture of yam. The selected probe P2 (diameter 2 mm) was placed symmetrically along the cross section of the slice at 0 and 7 d, respectively. The speeds before, during, and after the test were set to 3, 1, and 3 mm / s, respectively. The minimum sensing force was 5 g, the puncture depth was 3 mm, and the hardness (g) and brittleness (g) of the sample were calculated based on the average value of the two times.

[0054] The instruments involved in the present invention are:

[0055] High-voltage pulsed cold plasma generator (Jiangsu Xianjing Plasma Technology Research Institute Co., Ltd.), precision colorimeter, refrigerated high-speed centrifuge (Thermo Fisher Scientific (China) Co., Ltd.), UV spectrophotometer, electronic analytical balance (Shanghai Mettler-Toledo Instrument Co., Ltd.), water bath constant temperature oscillator (Changzhou Guowang Instrument Manufacturing Co., Ltd.).

[0056] raw material

[0057] Iron root yam was purchased from Weifang, Shandong;

[0058] NaHS and anhydrous ethanol were purchased from Sinopharm Group;

[0059] PAL kit, polyphenol kit, and antioxidant kit were purchased from Jianglai Biological.

[0060] Example 1

[0061] A method for treating fresh-cut yam by combining cold plasma and hydrogen sulfide, comprising the following steps:

[0062] (1) Wash and peel the iron root yam without rot or mechanical damage, weigh about 800 g of the whole tuber, and cut it into 5 mm yam slices;

[0063] (2) Spread a single layer of yam slices on a glass dish and place them in a cold plasma chamber and treat them at 450 V for 30 seconds;

[0064] (3) 200 g of cold plasma-treated yam slices were placed in 30 mL of 4 mmol / L NaHS solution and soaked for 10 minutes. The mixture was drained, placed in a glass dish, sealed, and stored at 0-4°C.

[0065] Example 2

[0066] The cold plasma voltage in step (2) in Example 1 was adjusted to 300 V, 350 V, 400 V, and 500 V, respectively. Other conditions were the same as in Example 1.

[0067] Example 3

[0068] The cold plasma treatment time in step (2) in Example 1 was adjusted to 10s, 20s, 60s, and 120s, respectively. Other conditions were the same as in Example 1.

[0069] Example 4

[0070] The concentrations of the hydrogen sulfide donor NaHS solution in step (3) of Example 1 were adjusted to 0.5 mmol / L, 1 mmol / L, 2 mmol / L, 4 mmol / L, and 8 mmol / L, respectively. Other conditions were the same as in Example 1.

[0071] Example 5

[0072] The treatment time of the hydrogen sulfide donor NaHS solution in step (3) in Example 1 was adjusted to 1 min, 5 min, 20 min, and 30 min, respectively. Other conditions were the same as in Example 1.

[0073] Comparative Example 1

[0074] (1) Preparation of fresh-cut Chinese yam: same as in Example 1.

[0075] (2) Hydrogen sulfide treatment: Spread the yam slices in a single layer on a glass dish, add 4 mmol / L NaHS solution, soak for 10 minutes, and then drain.

[0076] (3) Storage: Place fresh-cut yam slices in a glass dish and seal it tightly. Store in a refrigerator at 0-4°C.

[0077] Comparative Example 2

[0078] (1) Preparation of fresh-cut Chinese yam: same as in Example 1.

[0079] (2) Cold plasma treatment: Spread a single layer of yam slices on a glass dish, place it in a cold plasma chamber, and treat it at 450V for 30 seconds.

[0080] (3) Storage: Place fresh-cut yam slices in a glass dish and seal it tightly. Store in a refrigerator at 0-4°C.

[0081] Comparative Example 3

[0082] In Example 1, hydrogen sulfide was replaced with ascorbic acid of corresponding concentration, and other aspects remained the same as in Example 1.

[0083] Comparative Example 4

[0084] In Example 1, hydrogen sulfide was replaced with tea polyphenols of corresponding concentration, and the rest remained the same as in Example 1.

[0085] Comparative Example 5

[0086] The order of cold plasma and hydrogen sulfide treatment in Example 1 was adjusted, and other conditions were the same as in Example 1.

[0087] Example 6

[0088] The yams obtained by processing in Examples 1 to 5 and Comparative Examples 1 to 5 were placed for 72 hours to detect browning, changes in enzyme activity, changes in polyphenol and polysaccharide content, and changes in yam texture.

[0089] 1. Browning

[0090] The browning conditions of Example 1 and Comparative Examples 1 to 4 are as follows: Figure 1 As shown in (browning situation (A), PAL enzyme activity change (B)), the results show that compared with only cold plasma treatment (Comparative Example 2) and only NaHS solution soaking (Comparative Example 1), the combined use (Example 1) can achieve better results, with a BI value of 30.6 and an enzyme activity of 90.0; at the same time, by comparing Comparative Examples 3 and 4, it can be seen that the use of other antioxidants (ascorbic acid, tea polyphenols) solution soaking effect is much lower than NaHS.

[0091] The effects of different treatment conditions (Examples 2 to 5) on the browning of yam slices are shown in Figure 2. Figures 2 to 5 The results show that browning (A) and changes in PAL enzyme activity (B) were poorly effective under excessive voltage, NaHS concentration, and treatment time, with optimal results achieved only under appropriate conditions. Specifically, the optimal treatment conditions were: cold plasma at 450V for 30 seconds and immersion in a 4mmol / L NaHS solution for 10 minutes.

[0092] The browning condition (A) and the change of PAL enzyme activity (B) of Example 1 and Comparative Example 5 are shown in FIG. Figure 6 As shown, the results show that when the treatment order is changed, the effect of first soaking in NaHS solution and then using cold plasma treatment is significantly lower than that of first using plasma treatment and then soaking in NaHS solution.

[0093] 2. Nutrients

[0094] The total phenol and polysaccharide contents in the yam slices were measured after treatment in Example 1 and Comparative Examples 1 to 5. As shown in Tables 1 and 2, the total phenol and polysaccharide contents in Example 1 after three days were significantly higher than those in Comparative Examples 1 to 5.

[0095] Table 1 Changes in total phenol and polysaccharide contents in yam slices after treatment in Example 1 and Ratios 1 to 5

[0096]

[0097]

[0098] Note: Different superscript letters in the same column represent statistically significant differences (P<0.05).

[0099] 3. Texture (hardness, brittleness)

[0100] The hardness and brittleness of the yam slices after treatment of Example 1 and Comparative Examples 1 to 5 were tested. The results are shown in Table 2. After three days, the hardness and brittleness of Example 1 were significantly higher than those of Comparative Examples 1 to 5.

[0101] Table 2 Changes in hardness and brittleness of yam slices after treatment in Example 1 and Ratios 1 to 5

[0102] Hardness (g) Brittleness (g) Fresh yam (0h) <![CDATA[458.12 a ]]> <![CDATA[474.32 a ]]> Chinese Yam (72h) <![CDATA[400.35 d ]]> <![CDATA[402.37 d ]]> Example 1 <![CDATA[455.16 a ]]> <![CDATA[476.73 a ]]> Comparative Example 1 <![CDATA[403.49 d ]]> <![CDATA[405.74 d ]]> Comparative Example 2 <![CDATA[410.67 c ]]> <![CDATA[413.25 c ]]> Comparative Example 3 <![CDATA[411.43 c ]]> <![CDATA[412.87 c ]]> Comparative Example 4 <![CDATA[419.56 b ]]> <![CDATA[420.39 b ]]> Comparative Example 5 <![CDATA[422.55 b ]]> <![CDATA[421.52 b ]]>

[0103] Note: Different superscript letters in the same column represent statistically significant differences (P<0.05).

[0104] Although the present invention has been disclosed above in terms of preferred embodiments, it is not intended to limit the present invention. Anyone familiar with this technology can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the definition of the claims.

Claims

1. A method for inhibiting browning of fresh-cut yam, characterized in that: Including steps: (1) Spread a single layer of yam slices and treat them with cold plasma at a voltage of 300-500 V for 10-120 s; (2) The yam slices treated with cold plasma were soaked in a NaHS solution with a concentration of 0.5 to 8 mmol / L for 1 to 30 min and then drained to obtain yam slices with inhibited browning.

2. The method according to claim 1, characterized in that In step (1), the yam slices are treated with cold plasma at a voltage of 400 to 500 V for 30 to 120 seconds.

3. The method according to claim 1, characterized in that In step (2), the yam slices are soaked in a NaHS solution with a concentration of 2 to 4 mmol / L for 5 to 30 minutes.

4. The method according to claim 1, wherein The thickness of the yam slices in step (1) is 3 to 7 mm.

5. The method according to claim 1, wherein In step (2), the ratio of the yam tablets to the NaHS solution is 150-200 g: 25-30 mL.

6. The method according to claim 1, wherein The dried product in step (2) is stored at 0-4°C.

7. A method for inhibiting browning of fresh-cut yam while improving its texture and increasing its polyphenol and polysaccharide contents, characterized in that: Including steps: (1) Spread a single layer of yam slices and treat them with cold plasma at a voltage of 300-500 V for 10-120 s; (2) The yam slices treated with cold plasma were soaked in a NaHS solution with a concentration of 0.5 to 8 mmol / L for 1 to 30 min and then drained to obtain yam slices with inhibited browning.

8. The method according to claim 7, characterized in that In step (1), the yam slices are treated with cold plasma at a voltage of 400 to 500 V for 30 to 120 seconds; In step (2), the yam slices are soaked in a NaHS solution with a concentration of 2 to 4 mmol / L for 5 to 30 minutes.

9. The method according to claim 7, characterized in that The thickness of the yam slices in step (1) is 3-7 mm; and the dosage ratio of the yam slices to the NaHS solution in step (2) is 150-200 g: 25-30 mL.

10. Use of the method according to any one of claims 1 to 9 in preserving fresh-cut yam.

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