A freshness preservation method for cut fruits and vegetables using plasma activated water and tartaric acid in combination

Abstract

The present invention discloses a freshness preservation method for treating cut fruit and vegetables using plasma activated water and tartaric acid in combination, which belongs to the technical field of freshness preservation of fruit and vegetables. In the method for inhibiting Staphylococcus aureus using plasma activated water and tartaric acid in combination, the growth of Staphylococcus aureus can be effectively inhibited by using tartaric acid and plasma activated water in combination to act on Staphylococcus aureus, and the problem of cut fruit being easily spoiled when acting on cut fruit and vegetables can be effectively solved and the shelf life of cut fruit and vegetables can be extended. Compared with the single use of tartaric acid soaking and plasma activated water soaking treatment, the combined treatment of tartaric acid and plasma activated water can kill microorganisms on the surface of cut fruit and vegetables efficiently and with low energy consumption, effectively inhibit the activity of enzymes related to respiratory decay, maintain the sensory quality of the fresh food of cut fruit and vegetables, greatly extend its fresh shelf life, and do not generate chemical residues due to sterilization, significantly improving the safety of fresh fruit and vegetables.

Description

[Technical field]

[0001] The present invention relates to a method for preserving the freshness of cut fruit vegetables by treating them with plasma activated water and tartaric acid in combination, and belongs to the technical field of preserving the freshness of fruit vegetables. [Background technology]

[0002] Pineapple, also known as Houli (feng pear), is a perennial herbaceous fruit plant of the Bromeliaceae family, Bromeliaceae, rich in fructose, glucose, vitamins and minerals, and highly nutritious, which makes it popular with many consumers. However, pineapples are large in volume and difficult to peel and eat, which has limited their sales. Therefore, the application of cutting technology to supply ready-to-eat fruit vegetables to consumers while maintaining their freshness after sorting, washing, and cutting shows promising future market potential.

[0003] However, when pineapple goes through a series of cutting processes, various undesirable physiological and biochemical reactions occur, which damage the tissue structure of the fruit, and the enzymes and substrates in the tissues come into direct contact with each other, causing the juices in the fruit tissue to leak out. In addition, processes such as peeling and cutting the fruit lose the protective effect of the dermis, making it prone to microbial contamination and proliferation, especially the proliferation of Staphylococcus aureus. In addition, some nutrients are lost, affecting the quality of the product. These causes have led to problems such as deterioration of pineapple quality and short storage time, which have seriously restricted the development of the cut pineapple industry.

[0004] At present, many technical methods have been developed in China and abroad to extend the shelf life of cut fruits, including low-temperature cold chain, radiation preservation, ultra-high pressure preservation, modified atmosphere packaging, active packaging, edible coating, and antiseptic and antibacterial treatment. The first three traditional freshness preservation methods have problems such as complicated operation, high equipment costs, and insufficient freshness preservation effect. Freshness preservation methods such as new packaging and freshness preservation coding have a wide range of applications, but have disadvantages such as unstable antibacterial effect and unclear bacteriostatic effect.

[0005] Therefore, the development of highly efficient and non-toxic preservatives is one of the challenges that the cut fruit industry needs to overcome. Summary of the Invention [Problem to be solved by the invention]

[0006] The conventional methods for preserving the freshness of cut fruits have problems such as complicated operations, high costs, poor bacteriostatic effects, and insufficient freshness preservation effects.

[0007] In response to the above technical problems and deficiencies, the present invention provides a freshness preservation method for treating cut fruit and vegetable products by combining plasma activated water and tartaric acid, which can not only significantly reduce the number of bacteria growing and effectively maintain the sensory quality and nutritional value of the product, but also effectively inhibit the discoloration reaction of cut fruit and vegetable products and extend the shelf life of fresh produce. [Means for solving the problem]

[0008] The object of the present invention can be achieved by the following technical solutions.

[0009] The first object of the present invention is to (1) dissolving tartaric acid in plasma activated water to obtain a tartaric acid activated solution; (2) inoculating Staphylococcus aureus into a tryptic soy broth medium, culturing overnight to obtain a bacterial liquid, and then centrifuging and collecting the bacterial liquid, and suspending it in a sterile aqueous sodium chloride solution to obtain a suspension; The present invention provides a method for inhibiting Staphylococcus aureus by using plasma activated water and tartaric acid in combination, the method comprising: mixing the tartaric acid activation solution prepared in step (1) and the Staphylococcus aureus suspension prepared in step (2) in sterile water, homogenizing the mixture, and allowing it to stand to sterilize; and then, in step (3), placing the mixture in a petri dish, adding 15 to 20 mL of plate count medium, mixing homogenously, culturing, and counting.

[0010] In one embodiment, the plasma activated water in step (1) is plasma activated water obtained by preparation at a power of 400 W for 30 to 60 minutes, preferably 50 minutes.

[0011] In one embodiment, the concentration of the tartaric acid activation solution in step (1) is 0.25 to 1.0% by mass, preferably 0.75%.

[0012] In one embodiment, the tryptic soy broth medium in step (2) is prepared by dissolving 17.0 g tryptone, 5.0 g sodium chloride, 3.0 g soy papain hydrolysate, 2.5 g dipotassium phosphate, and 2.5 g glucose in 1 L of distilled water.

[0013] In one embodiment, the overnight culture conditions in step (2) are overnight culture at 37° C. and a rotation speed of 150 rpm.

[0014] In one embodiment, the suspension in step (2) is obtained by centrifuging 1 mL of the bacterial liquid at 8000 r for 5 minutes, collecting the collected liquid, and suspending it in 9 mL of a sterile aqueous sodium chloride solution to obtain a suspension, and the concentration of the bacterial liquid in the suspension is 10 6 ~10 7 CFU / mL.

[0015] In one embodiment, the volume ratio of the tartaric acid activation solution to the S. aureus suspension in step (3) is 1:1.

[0016] In one embodiment, the sterilization time in step (3) is 2 to 10 minutes, preferably 10 minutes.

[0017] In one embodiment, the plate count medium in step (3) is prepared by dissolving 5.0 g tryptone, 2.5 g yeast extract powder, 1.0 g glucose, and 15.0 g agar in 1 L of distilled water.

[0018] In one embodiment, the culturing in step (3) is carried out at 37° C. for 24 to 36 hours.

[0019] A second object of the present invention is to (1) Pre-treating fresh fruit by washing and slicing the fresh fruit and vegetables; (2) preparing a tartaric acid activation solution using tartaric acid as a solute and plasma activated water as a solution; Step (3) of soaking the thin slices of cut fruit and vegetables pretreated in step (1) in the tartaric acid activation solution prepared in step (2), draining the water after soaking, and soaking the fruit and vegetables; The method for preserving freshness of cut fruit vegetables using a combination of plasma activated water and tartaric acid includes a step (4) of thoroughly drying the fruit vegetables treated in the step (3), sealing and preserving the fruit vegetables.

[0020] In one embodiment, the fresh fruit vegetables in step (1) are one or more of pineapple, apple, pear, and cucumber.

[0021] In one embodiment, the plasma activated water in step (2) is plasma activated water obtained by preparation at a power of 400 W for 50 minutes.

[0022] In one embodiment, the concentration of the tartaric acid activation solution in step (2) is 0.75 to 1.0% by mass.

[0023] In one embodiment, the soaking time of the cut fruit or vegetable in the tartaric acid activating liquid in step (3) is 10 minutes.

[0024] In one embodiment, the thin slices in step (1) are thin slices of fresh fruit cut lengthwise to a thickness of 0.3 to 0.5 cm.

[0025] In one embodiment, the cut fruit or vegetable has a freshness retention time of 4 to 8 days when treated with a tartaric acid activating solution.

[0026] Another object of the present invention is to provide a freshness preservation method for treating cut fruit vegetables using the plasma activated water in combination with tartaric acid in a freshness preservation treatment of fruit vegetables.

[0027] The beneficial effects of the present invention are as follows:

[0028] (1) The freshness preservation method of treating cut fruit and vegetables with tartaric acid and plasma activated water according to the present invention effectively solves the problem of cut fruit being easily spoiled and extends the shelf life of cut fruit. Compared with the soaking in tartaric acid and the soaking in plasma activated water treatment alone, the combined treatment with tartaric acid and plasma activated water adopts a technical method of first immersion sterilization and then processing and packaging, which does not generate heat during the sterilization process and can efficiently kill microorganisms on the surface of cut fruit and vegetables with low energy consumption, effectively inhibit the activity of enzymes related to respiratory decay, maintain the sensory quality of the fresh food of cut fruit and vegetables, greatly extend their fresh expiration date, and do not generate chemical residues due to sterilization, significantly improving the safety of fresh fruit and vegetables. Cut fruit and vegetables treated with the combined treatment have a long freshness preservation time of 4 to 8 days when refrigerated.

[0029] (2) When cut fruit and vegetables are immersed in a tartaric acid solution, the low pH value of the tartaric acid solution can not only effectively inhibit polyphenol oxidase activity, but also inhibit the growth of microorganisms on the surface of the fruit and vegetables. Tartaric acid is a non-toxic, odorless, natural antioxidant that is harmless to the human body and the environment. When combined with plasma-activated water, it can effectively kill spoilage microorganisms and act uniformly regardless of the shape of the material. In addition, as a new non-heat sterilization technology, plasma-activated water treatment can effectively improve food quality with less loss and destruction of food color, texture, and nutrition, avoiding the adverse effects of heat on bioactive compounds in food, and prolonging the shelf life of food while maintaining the quality and nutritional content of cut fruit and vegetables.

[0030] (3) The freshness-preserving means of the present invention is environmentally friendly, safe, easy to implement, and readily accepted by consumers, and can be applied to various fruit and beverage stores, etc. [Brief description of the drawings]

[0031] [Figure 1] FIG. 2 is a data chart showing the logarithm of reduction in Staphylococcus aureus in bacterial liquids in Example 1 of the present invention and Comparative Examples 1 to 5. [Diagram 2] FIG. 2 is a data chart showing the logarithm of reduction in Staphylococcus aureus in a heterogeneous bacterial solution in Example 2 of the present invention. [Diagram 3] FIG. 1 is a data chart showing the log reduction of Staphylococcus aureus in a heterogeneous bacterial solution in Example 3 of the present invention. [Figure 4] FIG. 1 is a data diagram showing the logarithm of reduction in Staphylococcus aureus in a heterogeneous bacterial solution in Example 4 of the present invention. [Diagram 5] FIG. 1 is a graph showing changes in the surface color of cut pineapples within the storage period in Example 5 of the present invention and Comparative Examples 6 to 8. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0032] In order to make the present invention clearer, the present invention will be further described below with reference to the examples and drawings of cut pineapple. The examples are used for illustration only and are not intended to limit the present invention in any way. In the examples, each reagent material is commercially available, and the experimental methods without specific conditions are in accordance with the conventional methods and conventional conditions well known in the art or the conditions proposed by the equipment manufacturers.

[0033] Tryptic soy broth (TSB) medium: Dissolve 17.0 g trypsin, 5.0 g sodium chloride, 3.0 g soybean papain hydrolysate, 2.5 g dipotassium hydrogen phosphate, and 2.5 g glucose in 1 L of distilled water.

[0034] Plate Count Medium: Add 5.0 g tryptone, 2.5 g yeast extract powder, 1.0 g glucose, and 15.0 g agar to 1 L of distilled water.

[0035] Staphylococcus aureus ATCC 6538 was purchased from Beihan Biotechnology Research Institute.

[0036] Example 1 A method for inhibiting Staphylococcus aureus using plasma activated water in combination with tartaric acid, comprising the steps of:

[0037] (1) Preparation of plasma activated water: Deionized water was poured into a handheld plasma generator (a plasma activated water preparation device manufactured by BSH), the power was adjusted to 400 W, and the treatment was carried out for 50 min to generate plasma activated water (PAW).

[0038] (2) Preparation of tryptic soy broth (TSB) medium: Weigh out 3 g of tryptic soy broth medium and add it to 100 mL of deionized water. After dissolving, sterilize at 121°C for 15 minutes, cool the temperature, and then place in a bioclean bench.

[0039] (3) Preparation of plate count medium: Weigh out 4.7 g of plate count medium and add it to 100 mL of deionized water. After dissolving, sterilize at 121°C for 15 minutes, cool the temperature, and then place on a bioclean bench.

[0040] (4) Activation of Staphylococcus aureus: Take the Staphylococcus aureus ATCC 6538 stored in a -80°C refrigerator, inoculate the thawed culture into 15 mL of TSB medium prepared in step (2) at 37°C, and culture for 10 hours.

[0041] (5) Preparation of Staphylococcus aureus suspension: Inoculate 1 mL of the activated Staphylococcus aureus in step (4) into 10 mL of the tryptic soy broth (TSB) prepared in step (2) and leave it overnight at 37°C with the rotation speed set to 150 rpm. Then, collect 1 mL of the bacterial liquid by centrifugation at 8000 r for 5 minutes and suspend it in 9 mL of sterile aqueous sodium chloride solution to obtain a suspension.

[0042] (6) Preparation of tartaric acid activation solution: Add 0.75 g of tartaric acid to 100 ml of plasma activated water and dissolve completely.

[0043] (7) Sterilization treatment: 100 μL of the tartaric acid activation solution prepared in step (6), Staphylococcus aureus suspension prepared in step (5) (bacterial concentration is 10 7Mix 100 μL of 100 μL of 100-fold CFU / mL and 800 μL of sterile water uniformly, leave to stand for 10 minutes to sterilize, then place in a petri dish, pour in 15 mL of the plate count medium prepared in step (3), mix uniformly, culture at 37°C for 24 hours, and count.

[0044] Example 2 The remaining conditions were the same as in Example 1, except that the preparation time for the plasma activated water in step (1) in Example 1 was changed to 20 minutes, 30 minutes, 40 minutes, and 60 minutes, respectively.

[0045] Example 3 The remaining conditions were the same as in Example 1, except that the amount of tartaric acid added in step (6) in Example 1 was changed to 0.25 g, 0.5 g, and 1 g, respectively.

[0046] Example 4 The remaining conditions were the same as in Example 1, except that the sterilization time in step (7) in Example 1 was changed to 2 minutes, 4 minutes, 6 minutes, and 8 minutes, respectively.

[0047] Comparative Example 1 The remaining conditions were the same as in Example 1, except that the tartaric acid in step (6) of Example 1 was changed to 0.75 g of ascorbic acid.

[0048] Comparative Example 2 The remaining conditions were the same as in Example 1, except that the tartaric acid in step (6) of Example 1 was changed to 0.75 g of citric acid.

[0049] Comparative Example 3 The remaining conditions were the same as in Example 1, except that the tartaric acid in step (6) of Example 1 was changed to 0.75 g of gallic acid.

[0050] Comparative Example 4 The remaining conditions were the same as in Example 1, except that step (1) was omitted and the plasma-activated water in step (6) of Example 1 was replaced with deionized water.

[0051] Comparative Example 5 The remaining conditions were the same as in Example 1, except that tartaric acid was omitted and the tartaric acid activation solution in step (6) of Example 1 was replaced with plasma activated water.

[0052] Results measurement 1. The bacteria liquids of Example 1 and Comparative Examples 1 to 5 were counted and statistically analyzed. The results are shown in Table 1. TIFF0007662842000001.tif51170 Combining Table 1 and Figure 1, the bacteriostatic effect against Staphylococcus aureus was not very clear with only PAW (plasma activated water) treatment (Comparative Example 5), and the number of colonies was slightly reduced, by 1.28 ± 0.04 log 10 On the other hand, when treated with only the tartaric acid aqueous solution (Comparative Example 4), the bacteriostatic effect against Staphylococcus aureus was not very clear, and the number of colonies was only 1.08 ± 0.18 log 10 Only CFU / mL was reduced. Even when citric acid, ascorbic acid, and gallic acid were used in combination with plasma activated water, the bacteriostatic effect against Staphylococcus aureus was obviously lower than that of Example 1. This shows that the combination of TA and PAW treatment can significantly increase the inhibitory effect against Staphylococcus aureus and achieve good sterilization effect.

[0053] 2. Bacteriostatic effect of plasma-activated water prepared for different times on Staphylococcus aureus The results of counting and statistical analysis of the bacterial solution of Example 2 show that as the preparation time increases, the number of Staphylococcus aureus in the bacterial solution decreases steadily and the logarithm of the decrease increases, as shown in Figure 2. When the preparation time reaches 50 minutes, the number of Staphylococcus aureus in the bacterial solution reaches a nearly stable level, but even if the preparation time of the plasma activated water is further extended, the sterilization effect against Staphylococcus aureus in the bacterial solution is the same as when the preparation time is 50 minutes.

[0054] 3. Antibacterial effect of various concentrations of tartaric acid activating solution on Staphylococcus aureus The results of counting and statistical analysis of the bacterial solution of Example 3 showed that the number of Staphylococcus aureus in the bacterial solution was significantly reduced and the logarithm of the reduction increased with an increase in the mass concentration of the tartaric acid activation solution, as shown in Figure 3. When the concentration of the tartaric acid activation solution was about 0.75% and 1%, the reduction in Staphylococcus aureus in the bacterial solution became moderate, and at a concentration of 1%, the logarithm of the reduction in the bacterial solution was the highest, indicating the highest bacteriostatic effect.

[0055] 4. Staphylococcus aureus bacteriostatic effect by each sterilization time The results of counting and statistical analysis of the bacterial solution in Example 4 show that as the sterilization time increases, the number of Staphylococcus aureus in the bacterial solution is significantly reduced and the logarithm of the reduction increases, as shown in Figure 4. When the sterilization time reaches 10 minutes, the logarithm of the reduction of Staphylococcus aureus in the bacterial solution becomes moderate and reaches the highest level, indicating the highest bacteriostatic effect.

[0056] Example 5 A freshness preservation method for treating cut pineapple using a combination of plasma activated water and tartaric acid treatment, comprising the steps of:

[0057] (1) Washing: Select a fresh pineapple with undamaged skin and no disease, and wash it in clean water.

[0058] (2) Peeling and cutting: Peel the pineapple and first cut it crosswise to divide it into four parts, then cut it crosswise to obtain fresh pineapple chips about 0.5 cm thick.

[0059] (3) Preservative Immersion: Immerse the cut pineapple chips from step (2) in the tartaric acid activating solution prepared in Example 1 for 10 minutes, then remove and drain.

[0060] (4) Packaging and storage: After draining the water, place the pineapple chips in a sealed packaging bag and store in a constant temperature and humidity case at 4°C.

[0061] Comparative Example 6 The rest of the procedure was the same as in Example 1, except that step (3) in Example 5 was changed to immersion in fresh water for 10 minutes.

[0062] Comparative Example 7 The rest of the procedure was the same as in Example 1, except that step (3) in Example 5 was changed to 10 minutes of plasma-activated water immersion.

[0063] Comparative Example 8 The tartaric acid activation solution in step (3) of Example 5 was a tartaric acid solution of the same mass concentration prepared using deionized water, and the rest of the procedure was the same as in Example 1, except that the sample was immersed for 10 minutes, removed, and drained.

[0064] Results measurement For the pineapple chips treated for freshness preservation in Example 5 and Comparative Examples 6 to 8, the discoloration, change in polyphenol content, change in soluble solids content, and change in weight loss rate at different storage times were recorded.

[0065] Moisture loss can adversely affect the quality of fruits and vegetables, resulting in quality changes and poor color, which can lead to economic losses of fresh produce. As shown in Table 2, all samples experienced weight loss during storage, but the weight loss of the pineapple chip samples after treatment in Example 5 showed little significant change compared to Comparative Examples 6 to 8 during storage times of 2 to 8 days. This indicates that treating cut pineapple chips with a combination of tartaric acid and plasma-activated water can effectively reduce moisture loss and maintain the freshness of the pineapple chips.

[0066] As can be seen from the color statistical data, for the pineapple chips treated in Comparative Examples 6 to 8, the L* value continuously decreased with the increase in treatment time, and the degree of decrease showed a significant difference, while the L* value of the pineapple chips treated in Example 5 decreased to some extent, but the degree of decrease was small and there was no obvious difference. It was shown that the treatment of cut pineapple chips with tartaric acid and plasma activated water in combination can effectively maintain the color of cut pineapple chips and preserve the freshness of pineapple chips.

[0067] The soluble solids content is an important indicator of the sweetness of fruits and consumer acceptability. As can be seen from the statistical data, the soluble solids content of the pineapple chips treated in Example 5 and Comparative Examples 6-8 decreases with increasing treatment time, but the reduction in the soluble solids content in Example 5 is significantly lower than that in Comparative Examples 6-8. It is shown that the combined use of tartaric acid and plasma-activated water to treat pineapple chips can effectively reduce the loss of soluble solids content in pineapple chips.

[0068] In terms of the total acid content in the pineapple chips, the total acid content in the pineapple chips treated in Example 5 and Comparative Examples 6 to 8 all decreased with the extension of the storage time, but the rate of decrease in the total acid content in Example 5 was clearly smaller than that in Comparative Examples 6 to 8. It was shown that treating the pineapple chips with a combination of tartaric acid and plasma activated water can effectively reduce the total acid content in the pineapple chips.

[0069] Similarly, for the total phenol content in cut-cut pineapple chips, when the samples were treated with tartaric acid and plasma activated water in combination, the total phenol content increased from 84.34 g / kg to 90.14 g / kg. As the treatment time was extended, the total phenol content in the pineapple chips decreased continuously, for example, in Comparative Example 6, the total phenol content decreased from 84.34 g / kg to 48.54 g / kg after 0 and 8 days of treatment, the content was almost reduced by half. In Comparative Examples 7 and 8, the total phenol content also decreased significantly, by 22.9% and 39.5%, respectively. Meanwhile, in Example 5, the decrease was only 16.2%, from 90.14 g / kg to 75.56 g / kg. It was found that the decrease in the total phenol content in the cut pineapple chips treated in Example 5 was obviously lower than that in Comparative Examples 6 to 8. It was shown that the combined treatment of cut pineapple chips with tartaric acid and plasma-activated water could effectively reduce the loss of total phenolic content in the fruit and preserve the freshness of the fruit.

[0070] Table 2. Changes in discoloration, polyphenol content, soluble solid content, and weight loss rate of cut pineapple chips during storage for each period of time in Example 5 and Comparative Examples 6 to 8 TIFF0007662842000002.tif244170TIFF0007662842000003.tif243170TIFF0007662842000004.tif18170

Claims

1. A method for inhibiting Staphylococcus aureus by using plasma activated water in combination with tartaric acid, comprising: (1) dissolving tartaric acid in plasma activated water to obtain a tartaric acid activated solution; (2) inoculating Staphylococcus aureus into a tryptic soy broth medium, culturing overnight to obtain a bacterial suspension, and then centrifuging and collecting the bacterial suspension, and suspending it in a sterile aqueous sodium chloride solution to obtain a suspension; and step (3) of mixing the tartaric acid activation solution prepared in step (1) and the Staphylococcus aureus suspension prepared in step (2) in sterile water, homogenizing the mixture, and allowing it to stand to sterilize it. Thereafter, the mixture is placed in a petri dish, 15 to 20 mL of plate count medium is added, the mixture is homogenized, and the mixture is cultured and counted.

2. 2. The method according to claim 1, wherein the plasma activated water in step (1) is plasma activated water obtained by preparing the water at a power of 400 W for 30 to 60 minutes.

3. The method according to claim 1, characterized in that the concentration of the tartaric acid activation solution in step (1) is 0.25 to 1.0% by weight.

4. 2. The method according to claim 1, wherein the duration of the sterilization treatment in step (3) is 2 to 10 minutes.

5. 2. The method according to claim 1, wherein the volume ratio of the tartaric acid activation solution to the Staphylococcus aureus suspension in step (3) is 1:

1.

6. 2. The method according to claim 1, wherein the culturing in step (3) is carried out at 37° C. for 24 to 36 hours.

7. A freshness preservation method for treating cut fruit and vegetables using plasma activated water and tartaric acid in combination, comprising: (1) Pre-treating fresh fruit by washing and slicing the fresh fruit and vegetables; (2) preparing a tartaric acid activation solution using tartaric acid as a solute and plasma activated water as a solution; Step (3) of soaking the thin slices of cut fruit and vegetables pretreated in step (1) in the tartaric acid activating solution prepared in step (2), and draining the water after soaking; and (4) storing the fruit or vegetable by thoroughly drying, sealing and storing the fruit or vegetable processed in step (3).

8. The method according to claim 7, characterized in that the concentration of the tartaric acid activation solution in step (2) is 0.75 to 1.0% by weight.

9. 8. The method according to claim 7, wherein the soaking time of the cut fruit and vegetable in the tartaric acid activating solution in step (3) is 10 minutes.

10. Use of the method according to any one of claims 7 to 9 in freshness preservation treatment of fruit and vegetables.

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