Method for preserving strawberries by combining low-voltage electrostatic field with essential oil

Abstract

The invention discloses a method for preserving strawberries by combining a low-voltage electrostatic field with essential oil. The method comprises the following steps: taking fresh strawberries, spraying composite essential oil, and storing in a low-voltage electrostatic field and a low-temperature environment. The low-voltage electrostatic field is combined with the compound essential oil to preserve the strawberries, the preservation effect is obviously enhanced, the weight loss rate and the rotting rate of strawberry preservation are greatly reduced, and the combined use of the active ingredients of the tea tree essential oil and the cedar essential oil in the essential oil and the synergistic interaction of the filipendula essential oil and the mango seed essential oil are achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of food preservation, and in particular relates to a method for preserving strawberries using a low-voltage electrostatic field combined with essential oil. Background Art

[0002] Strawberry belongs to the Rosaceae family and is a widely cultivated herb. It has a sweet and sour taste, bright red color, beautiful appearance, soft and juicy texture, and rich aroma. Strawberry contains a variety of nutrients, including minerals, vitamins, anthocyanins, flavonoids and phenolic acids, which show beneficial biological properties in the human body.

[0003] During the ripening process, strawberry fruit will undergo a structural change, and the texture changes that occur are collectively referred to as softening. From the consumer's perspective, texture is the main quality attribute that determines the fruit's acceptance in the market. Usually, the main reason for the softening of strawberry fruit is the change in cell wall structure and components. Cell wall degradation is the result of the combined action of a variety of cell wall degrading enzymes or proteins, in which the content of cell wall components is reduced and the cell wall porosity is increased, which helps the cell wall degrading enzymes enter their substrates and accelerates the softening of the fruit. Slowing down the softening of strawberry fruit and extending the shelf life have become urgent issues to be addressed. At present, commonly used preservation methods include heat treatment, coating preservation, temperature regulation storage, modified atmosphere packaging and chemical reagent treatment. Compared with traditional preservation methods, physical preservation is an emerging green and efficient preservation technology.

[0004] Physical field preservation technology is to preserve agricultural products by using physical fields, which is safer, more effective and cleaner. Among them, low voltage electrostatic field (LVEF) preservation technology is particularly eye-catching. It is a non-toxic and pollution-free physical preservation method that does not damage the cell walls of fruits and vegetables, and can maintain the original quality to the maximum extent, reduce the waste of raw materials, and has no residue. It is safe and effective. It has a good preservation effect on cherry tomatoes, mushrooms, grapes and other fruits. However, the effect of simply using low voltage electrostatic field to preserve strawberries is limited and cannot meet the market requirements. Summary of the invention

[0005] The invention aims to provide a method for preserving strawberries by combining a low-voltage electrostatic field with essential oil.

[0006] The invention discloses a method for preserving strawberries by using a low-voltage electrostatic field and essential oil. The method comprises spraying the fresh strawberries with essential oil and then preserving them in a low-voltage electrostatic field and a low-temperature environment.

[0007] The essential oils are tea tree essential oil and cedar essential oil, and the usage mass ratio is 3:1.

[0008] The essential oils are mosquito grass essential oil and mango seed essential oil, and the usage mass ratio is 1:1.

[0009] The preparation method of the mosquito grass essential oil is as follows: take the stems and leaves of the mosquito grass, add them into a distillation kettle, control the steam pressure at 0.05-0.15MPa, distill for 2-3h, adopt a two-stage separation method, connect two oil-water separators in series to completely separate the oil and water, take out the essential oil floating on the upper layer, dry and filter, and obtain the mosquito grass essential oil.

[0010] The preparation method of the mango kernel essential oil is as follows: after drying the mango kernel, crush it through 40-80 meshes, and spray water until the moisture content of the mango kernel powder is 15-25%; the mango kernel powder is placed in an extraction kettle of a supercritical CO2 extraction device for supercritical CO2 extraction, and the extraction conditions are: CO2 flow rate of 10-35L / min, extraction pressure of 30-45MPa, extraction temperature of 30-50℃, decomposition temperature of 30-40℃, and extraction time of 1-3h; after extraction, the extract enters a separation tank for separation, and mango kernel crude essential oil is obtained from the bottom of the separation tank, and the obtained mango kernel crude essential oil is placed in a molecular distillation reactor for molecular distillation to obtain the mango kernel essential oil.

[0011] The field strength of the low-voltage electrostatic field is 0-2.5 kV / m.

[0012] The low temperature is 1-8°C.

[0013] The spraying amount of the essential oil is 5-20 g per 1 kg of strawberries.

[0014] Beneficial effects of the present invention: The present invention uses a low-voltage electrostatic field in combination with a composite essential oil to preserve strawberries, and the preservation effect is significantly enhanced, greatly reducing the weight loss rate and decay rate of the strawberries during storage. The combined use of the active ingredients tea tree essential oil and cedar essential oil in the essential oils, as well as mosquito grass essential oil and mango kernel essential oil, synergizes and enhances the effect. DETAILED DESCRIPTION

[0015] In order to facilitate the understanding of the present invention, the present invention will be described more fully below. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0016] The tea tree essential oil and cedar essential oil used in the following examples were purchased from Guangzhou Hongli Biotechnology Co., Ltd.

[0017] Example 1

[0018] A method for preserving strawberries by using a low-voltage electrostatic field in combination with essential oils, comprising: spraying fresh strawberries with essential oils and then preserving the strawberries in a low-voltage electrostatic field and in a 4°C environment; the essential oils are tea tree essential oil and cedar essential oil, with a usage mass ratio of 3:1; the field strength of the low-voltage electrostatic field is 2 kV / m; and the spraying amount of the essential oils is 12 g per 1 kg of strawberries.

[0019] Example 2

[0020] A method for preserving strawberries by using a low-voltage electrostatic field in combination with essential oils, comprising: spraying fresh strawberries with essential oils and then preserving the strawberries in a low-voltage electrostatic field and in a 4°C environment; the essential oils are mosquito grass essential oil and mango seed essential oil, with a usage mass ratio of 1:1; the field strength of the low-voltage electrostatic field is 1.5 kV / m; and the spraying amount of the essential oil is 10 g per 1 kg of strawberries.

[0021] The preparation method of the mosquito grass essential oil is as follows: take the stems and leaves of the mosquito grass, add them into a distillation kettle, control the steam pressure at 0.1MPa, distill for 2.5 hours, adopt a two-stage separation method, connect two oil-water separators in series to completely separate the oil and water, take out the essential oil floating on the upper layer, dry and filter, and obtain the mosquito grass essential oil.

[0022] The preparation method of the mango kernel essential oil is as follows: after drying the mango kernel, crush it through 60 meshes, and spray water until the moisture content of the mango kernel powder is 20%; the mango kernel powder is placed in an extraction kettle of a supercritical CO2 extraction device for supercritical CO2 extraction, and the extraction conditions are: CO2 flow rate 25L / min, extraction pressure 35MPa, extraction temperature 40°C, decomposition temperature 35°C, and extraction time 2h; after extraction, the extract enters a separation tank for separation, and mango kernel crude essential oil is obtained from the bottom of the separation tank, and the obtained mango kernel crude essential oil is placed in a molecular distillation reactor for molecular distillation to obtain the mango kernel essential oil.

[0023] Example 3

[0024] A method for preserving strawberries by combining a low-voltage electrostatic field with essential oils comprises spraying fresh strawberries with essential oils and then preserving them in a low-voltage electrostatic field and in an environment of 6°C; the essential oils are Filipendula essential oil and mango seed essential oil in a mass ratio of 1:1; the field strength of the low-voltage electrostatic field is 2.5 kV / m; and the spraying amount of the essential oil is 15 g per 1 kg of strawberries.

[0025] The preparation method of the mosquito grass essential oil is as follows: take the stems and leaves of the mosquito grass, add them into a distillation kettle, control the steam pressure at 0.08MPa, distill for 2h, adopt a two-stage separation method, connect two oil-water separators in series to completely separate the oil and water, take out the essential oil floating on the upper layer, dry and filter, and obtain the mosquito grass essential oil.

[0026] The preparation method of the mango kernel essential oil is as follows: after drying the mango kernel, crush it through 70 meshes, and spray water until the moisture content of the mango kernel powder is 18%; the mango kernel powder is placed in an extraction kettle of a supercritical CO2 extraction device for supercritical CO2 extraction, and the extraction conditions are: CO2 flow rate of 15L / min, extraction pressure of 32MPa, extraction temperature of 32°C, decomposition temperature of 32°C, and extraction time of 3h; after extraction, the extract enters a separation tank for separation, and mango kernel crude essential oil is obtained from the bottom of the separation tank, and the obtained mango kernel crude essential oil is placed in a molecular distillation reactor for molecular distillation to obtain the mango kernel essential oil.

[0027] Comparative Example 1

[0028] A method for preserving strawberries by combining a low-voltage electrostatic field with essential oil comprises the following steps: spraying tea tree essential oil on fresh strawberries and then preserving them in a low-voltage electrostatic field and a 4°C environment; the field strength of the low-voltage electrostatic field is 2 kV / m; and the spraying amount of the tea tree essential oil is 12 g per 1 kg of strawberries.

[0029] Comparative Example 2

[0030] A method for preserving strawberries by combining a low-voltage electrostatic field with essential oil comprises the following steps: spraying fresh strawberries with cedar essential oil and then preserving them in a low-voltage electrostatic field and a 4°C environment; the field strength of the low-voltage electrostatic field is 2 kV / m; and the spraying amount of the cedar essential oil is 12 g per 1 kg of strawberries.

[0031] Comparative Example 3

[0032] A method for preserving strawberries by combining a low-voltage electrostatic field with essential oil comprises the following steps: spraying fresh strawberries with Filipendula essential oil and then storing them in a low-voltage electrostatic field and in an environment of 4°C; the field strength of the low-voltage electrostatic field is 1.5 kV / m; and the spraying amount of the Filipendula essential oil is 10 g per 1 kg of strawberries.

[0033] The preparation method of the mosquito grass essential oil is as follows: take the stems and leaves of the mosquito grass, add them into a distillation kettle, control the steam pressure at 0.1MPa, distill for 2.5 hours, adopt a two-stage separation method, connect two oil-water separators in series to completely separate the oil and water, take out the essential oil floating on the upper layer, dry and filter, and obtain the mosquito grass essential oil.

[0034] Comparative Example 4

[0035] A method for preserving strawberries by combining a low-voltage electrostatic field with essential oil comprises the following steps: spraying mango seed essential oil on fresh strawberries and then preserving them in a low-voltage electrostatic field and a 4°C environment; the field strength of the low-voltage electrostatic field is 1.5 kV / m; and the spraying amount of the mango seed essential oil is 10 g per 1 kg of strawberries.

[0036] The preparation method of the mango kernel essential oil is as follows: after drying the mango kernel, crush it through 60 meshes, and spray water until the moisture content of the mango kernel powder is 20%; the mango kernel powder is placed in an extraction kettle of a supercritical CO2 extraction device for supercritical CO2 extraction, and the extraction conditions are: CO2 flow rate 25L / min, extraction pressure 35MPa, extraction temperature 40°C, decomposition temperature 35°C, and extraction time 2h; after extraction, the extract enters a separation tank for separation, and mango kernel crude essential oil is obtained from the bottom of the separation tank, and the obtained mango kernel crude essential oil is placed in a molecular distillation reactor for molecular distillation to obtain the mango kernel essential oil.

[0037] Experimental example:

[0038] The strawberries used in the experiment were freshly picked and of the "Hongyan" variety. Strawberry fruits with no mechanical damage, uniform size, and consistent maturity (80% ripe) were selected as experimental materials. They were randomly packed into PET boxes (170mm×140mm×55mm) and immediately transported to the laboratory.

[0039] Determination of weight loss rate: 30 strawberries in each group were fixed as the measurement objects of weight loss rate and weighed on an analytical balance. The mass of each group of strawberries was measured regularly to calculate its weight loss rate.

[0040]

[0041] Where M0 is the weight of strawberry fruit before storage, g; Mn is the mass of strawberry fruit after storage for n days, g.

[0042] Strawberries were preserved by the methods of Example 1 and Comparative Examples 1-2, and the weight loss rate of the strawberries was measured after 7 days of preservation. Each group of experiments was measured in parallel 3 times, and statistical analysis was performed using SPSS24.0 software.

[0043] The measurement data results were used (mean ± standard deviation), the Kolmogorov-Smirnov test was used for data normality test, and the t-test was used to compare the mean differences between the two groups for data that met the normal distribution, with P < 0.05 as the difference being statistically significant. The results are shown in Table 1:

[0044] Table 1

[0045]

[0046] Note: * represents P < 0.05 compared with the group in Example 1.

[0047] Determination of rot rate: 30 strawberries in each group are fixed as the rot rate. Any shrinkage, juice oozing, lesions and microbial growth in strawberries, no matter how serious, will be regarded as rotten fruit. The calculation method of rot rate is as follows:

[0048]

[0049] Wherein, DI is the decay rate, %; n is the number of rotten strawberries in each measurement.

[0050] Strawberries were preserved by the methods of Examples 2-3 and Comparative Examples 3-4, respectively. The rot rate of strawberries was measured after 7 days of preservation. Each group of experiments was measured in parallel 3 times. SPSS 24.0 software was used for statistical analysis.

[0051] The results of quantitative data are used for analysis. (mean ± standard deviation) was expressed, and the Kolmogorov-Smirnov test was used for data normality test. For data that met the normal distribution, the mean difference between the two groups was compared using the t test, and the difference was considered statistically significant when P < 0.05. The measurement results are shown in Table 2:

[0052] Table 2

[0053]

[0054] Note: * represents P < 0.05 compared with the group in Example 2.

[0055] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A method for preserving strawberries by using a low-voltage electrostatic field combined with essential oils, It is characterized in that Fresh strawberries are sprayed with essential oil and then stored in a low-voltage static electric field and low-temperature environment.

2. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 1, It is characterized in that The essential oils are tea tree essential oil and cedar essential oil, and the usage mass ratio is 3:

1.

3. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 1, It is characterized in that The essential oils are mosquito grass essential oil and mango seed essential oil, and the usage mass ratio is 1:

1.

4. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 3, It is characterized in that The preparation method of the mosquito grass essential oil is as follows: take the stems and leaves of the mosquito grass, add them into a distillation kettle, control the steam pressure at 0.05-0.15MPa, distill for 2-3h, adopt a two-stage separation method, connect two oil-water separators in series to completely separate the oil and water, take out the essential oil floating on the upper layer, dry and filter, and obtain the mosquito grass essential oil.

5. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 3, It is characterized in that The preparation method of the mango kernel essential oil is as follows: after drying the mango kernel, crush it through 40-80 meshes, spray water until the moisture content of the mango kernel powder is 15-25%; place the mango kernel powder in a supercritical CO 2 Supercritical CO 2 Extraction, the extraction conditions are: CO 2 The flow rate is 10-35L / min, the extraction pressure is 30-45MPa, the extraction temperature is 30-50℃, the decomposition temperature is 30-40℃, and the extraction time is 1-3h; after extraction, the extract enters a separation tank for separation, and mango kernel crude essential oil is obtained from the bottom of the separation tank. The obtained mango kernel crude essential oil is placed in a molecular distillation reactor for molecular distillation to obtain mango kernel essential oil.

6. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 1, It is characterized in that The field strength of the low-voltage electrostatic field is 0-2.5 kV / m.

7. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 1, It is characterized in that The low temperature is 1-8°C.

8. The method for preserving strawberries by using a low-voltage electrostatic field combined with essential oil according to claim 1, It is characterized in that The spraying amount of the essential oil is 5-20 g per 1 kg of strawberries.

Images