阅读说明：本技术 一种植物体涂膜预处理干燥方法及挥发油提取工艺 (Plant body coating pretreatment drying method and volatile oil extraction process ) 是由 李远辉 齐娅汝 伍振峰 万娜 王学成 杨明 于 2020-12-29 设计创作，主要内容包括：本发明公开了一种植物体涂膜预处理干燥方法,包括如下步骤：S1涂膜预处理：称取一定量的可溶性高分子材料配置成水溶液,即得膜材料；将植物体完全浸没于膜材料中,再取出,用滤纸除去多余的膜材料,备用；S2干燥：将涂有膜材料的植物体低温热风干燥,干燥温度低于100℃。本发明通过对植物体进行涂膜预处理干燥可提高挥发油成分的保有率,且不影响干燥效率。(The invention discloses a plant body coating pretreatment drying method, which comprises the following steps: s1 film coating pretreatment: weighing a certain amount of soluble polymer material to prepare an aqueous solution to obtain a membrane material; completely immersing the plant body in the membrane material, taking out, and removing the redundant membrane material by using filter paper for later use; s2 drying: drying the plant body coated with the membrane material by hot air at low temperature, wherein the drying temperature is lower than 100 ℃. The invention can improve the retention rate of volatile oil components by performing film coating pretreatment drying on the plant body without influencing drying efficiency.)

1. A plant body coating pretreatment drying method is characterized by comprising the following steps:

s1 film coating pretreatment: weighing a certain amount of soluble polymer material to prepare an aqueous solution to obtain a membrane material; completely immersing the plant body in the membrane material, taking out, and removing the redundant membrane material by using filter paper for later use;

s2 drying: drying the plant body coated with the membrane material at a temperature lower than 100 ℃.

2. The method as claimed in claim 1, wherein the film material is one of carboxymethyl cellulose, chitosan, starch, gelatin, and methyl cellulose aqueous solution.

3. The method as claimed in claim 1, wherein the film material is carboxymethyl cellulose with a mass concentration of 2%.

4. The method as claimed in claim 1, wherein the film material is chitosan with a mass concentration of 2%.

5. The method for pre-treating and drying the plant body coating film according to claim 1, which is characterized in that the method comprises the following steps of: the drying temperature is 60 ℃ and the pressure is 50 mbar.

6. The method for pre-treating and drying the plant body coating film according to claim 1, wherein the method comprises the following steps: the drying temperature was 60 ℃.

7. The method as claimed in claim 1, wherein the drying is microwave vacuum drying with microwave power of 480W and pressure of 100 Pa.

8. The method for pre-treating and drying the plant body coating film according to claim 1, wherein the drying mode is far infrared drying: the power was 1000W.

9. The method as claimed in claim 1, wherein the plant is fresh prickly ash.

10. A volatile oil extraction process based on film pretreatment drying comprises weighing a certain amount of soluble polymer material to prepare into aqueous solution to obtain film material; completely immersing the plant body in the membrane material, taking out, and removing the redundant membrane material by using filter paper for later use; drying the plant body coated with the membrane material; extracting volatile oil from the dried plant body by steam distillation.

Technical Field

The invention relates to the technical field of drying, in particular to a plant body coating pretreatment drying method and a volatile oil extraction process.

Background

Volatile oil, also known as essential oil, is a generic term for water-immiscible volatile oily components that can be obtained with steam distillation. It is widely present in plants, and it can be said that: all odorous plants contain varying amounts of volatile oils. The volatile oil has strong aromatic odor, and wide pharmacological activities such as antidepressant, antianxiety, antiinflammatory, antiallergic, antimicrobial, antimutagenic and anticancer, anthelmintic, and skin caring effects, and can be widely used in food, cosmetic, medicine and pesticide fields. Generally, fresh plants such as herbs, fruits, vegetables, etc. are not easily stored after harvesting, and are usually dried to reduce their moisture content, prolong their shelf life, and facilitate their transportation. However, the volatile oil component has strong volatility and is unstable when heated, and the loss of the volatile oil is large after drying, thereby causing the serious reduction of the product quality. Therefore, the finding of suitable drying technology with the function of protecting the volatile oil is of great significance.

The film coating pretreatment is used for preserving fruits and vegetables which can be used as medicine and food, and the method reduces the loss of water by coating a layer of film material, such as carboxymethyl cellulose, chitosan, starch, gelatin, methyl cellulose aqueous solution and the like, on fresh materials or isolates the materials from contacting oxygen in the environment to prevent the loss of effective components caused by oxidation. However, no relevant research report has been found on the technology of the coating film pretreatment for the drying process, and it is unknown whether the coating film pretreatment affects the drying efficiency.

The study takes pepper as an example, and the pepper is subjected to film coating pretreatment and drying, and the result proves that the method can improve the retention rate of volatile oil components, does not influence the drying efficiency, and has important application value.

Disclosure of Invention

The invention aims to provide a plant body film coating pretreatment drying method, which can improve the retention rate of volatile oil components by performing film coating pretreatment drying on a plant body, does not influence the drying efficiency, has important application value and provides an extraction process capable of improving the extraction rate of volatile oil.

In order to achieve the purpose, the invention adopts the following technical scheme: a plant body coating pretreatment drying method comprises the following steps:

s1 film coating pretreatment: weighing a certain amount of soluble polymer material to prepare an aqueous solution to obtain a membrane material; completely immersing the plant body in the membrane material, taking out, and removing the redundant membrane material by using filter paper for later use;

s2 drying: drying the plant body coated with the membrane material at a temperature lower than 100 ℃.

More preferably, the membrane material is one of carboxymethyl cellulose, chitosan, starch, gelatin and methyl cellulose aqueous solution.

Further preferably, the membrane material is carboxymethyl cellulose with a mass concentration of 2%.

Further preferably, the membrane material is chitosan with a mass concentration of 2%.

More preferably, the drying method is hot air drying: in order to ensure the product quality, the low-temperature drying temperature is 60 ℃.

More preferably, the plant is fresh zanthoxylum bungeanum.

The invention also provides a volatile oil extraction process based on film pretreatment drying, which comprises the steps of weighing a certain amount of soluble high polymer material to prepare an aqueous solution to obtain a film material; completely immersing the plant body in the membrane material, taking out, and removing the redundant membrane material by using filter paper for later use; drying the plant body coated with the membrane material; extracting volatile oil from the dried plant body by steam distillation.

The invention has the beneficial effects that: the protective effect of the plant cell tissue structure is an important factor for reducing the loss of the volatile oil in the drying process, and the film coating pretreatment drying can reduce the pressure stress on the volatile oil due to shrinkage by inhibiting the shrinkage of the cell tissue structure so as to protect the internal environment of the tissue where the volatile oil exists and further reduce the loss of the volatile oil component caused by drying; meanwhile, the coating film layer on the surface of the material can play a role of a physical barrier to prevent volatile oil in the material from escaping from the surface of the material after being heated and vaporized. Therefore, the film coating pretreatment drying method is expected to play a role in preventing or reducing the loss of the volatile oil components of the medicinal and edible fruits and vegetables in the drying process so as to protect the volatile oil components and improve the quality of dried products. The method takes pepper as an example, and performs film coating pretreatment and drying on the pepper, and the result proves that the method can improve the retention rate of volatile oil components, does not influence the drying efficiency, and has important application value.

Drawings

FIG. 1 is a graph showing changes in water content of a 2% carboxymethyl cellulose film and a 2% chitosan film without a film under hot air drying conditions.

FIG. 2 is a graph showing the change in drying rate of an uncoated film, a 2% carboxymethyl cellulose coated film, and a 2% chitosan coated film under hot air drying conditions.

Detailed Description

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments.

Example 1

1. Film coating pretreatment: weighing a certain amount of carboxymethyl cellulose to prepare an aqueous solution with the concentration of 2 percent, namely the membrane material. Completely immersing 200g of fresh pepper in the membrane material, taking out, and removing the redundant membrane material by using filter paper for standby.

2. And (3) drying: and (3) drying the fresh pepper coated with the carboxymethyl cellulose membrane by hot air at 60 ℃ under 50mbar until the moisture content is lower than 10%, and taking out to finish drying.

3. Drying kinetics: sampling and weighing every half hour in the drying process, calculating the water content corresponding to each time point in the drying process according to the initial water content of the pepper, and drawing a drying kinetic curve. And calculating the drying rate according to the change of the water content at two adjacent time points in the drying process, and drawing a change curve of the drying rate along with the time.

The water content calculation formula is shown in formula (1), and the drying rate calculation formula is shown in formula (2).

In the formula M₀As initial water content of the sample, M₁Is the initial mass of the sample, M₂Is the sample mass of the sampling point in the drying process.

In the formula M₁And M₂The mass of the samples at two adjacent sampling points in the drying process is respectively shown, and t (h) is the interval time between two adjacent sampling points in the drying process.

4. The yield of the volatile oil is as follows: the dried pepper is extracted by adopting a steam distillation method, wherein the material-liquid ratio is 1: 5, extracting for 5h, and measuring the volume of the volatile oil after the extraction is finished. The volatile oil yield calculation formula is as follows:

in the formula, V is the volume of the volatile oil obtained by extraction, and M is the mass of the fresh plant (350 g in the experiment).

Example 2

1. Film coating pretreatment: weighing a certain amount of carboxymethyl cellulose to prepare an aqueous solution with the concentration of 2 percent, namely the membrane material. Completely immersing 200g of fresh pepper in the membrane material, taking out, and removing the redundant membrane material by using filter paper for standby.

2. And (3) drying: and (3) drying the fresh pepper coated with the carboxymethyl cellulose membrane at 60 ℃ in vacuum, taking out the pepper when the moisture content is lower than 10%, and finishing drying.

3. Drying kinetics: sampling and weighing every half hour in the drying process, calculating the water content corresponding to each time point in the drying process according to the initial water content of the pepper, and drawing a drying kinetic curve. And calculating the drying rate according to the change of the water content at two adjacent time points in the drying process, and drawing a change curve of the drying rate along with the time.

The water content calculation formula is shown in formula (1), and the drying rate calculation formula is shown in formula (2).

In the formula M₀As initial water content of the sample, M₁Is the initial mass of the sample, M₂Is the sample mass of the sampling point in the drying process.

In the formula M₁And M₂The mass of the samples at two adjacent sampling points in the drying process is respectively shown, and t (h) is the interval time between two adjacent sampling points in the drying process.

4. The yield of the volatile oil is as follows: the dried pepper is extracted by adopting a steam distillation method, wherein the material-liquid ratio is 1: 5, extracting for 5h, and measuring the volume of the volatile oil after the extraction is finished. The volatile oil yield calculation formula is as follows:

in the formula, V is the volume of the volatile oil obtained by extraction, and M is the mass of the fresh plant (350 g in the experiment).

Example 3

Different from the example 1, the drying method is microwave vacuum drying, the microwave power is 480W, and the pressure is 100 Pa.

Example 4

Unlike example 1, the drying mode was far-infrared drying and the power was 1000W.

Example 5

1. Film coating pretreatment: weighing a certain amount of chitosan to prepare an aqueous solution with the concentration of 2 percent, namely the membrane material. Completely immersing 200g of fresh pepper in the membrane material, taking out, and removing the redundant membrane material by using filter paper for standby.

2. And (3) drying: and (3) drying the fresh pepper coated with the chitosan film by hot air at 60 ℃ under 50mbar until the moisture content is lower than 10%, and finishing the drying.

3. Drying kinetics: sampling and weighing every half hour in the drying process, calculating the water content corresponding to each time point in the drying process according to the initial water content of the pepper, and drawing a drying kinetic curve. And calculating the drying rate according to the change of the water content at two adjacent time points in the drying process, and drawing a change curve of the drying rate along with the time.

The water content calculation formula is shown in formula (1), and the drying rate calculation formula is shown in formula (2).

In the formula M₀As initial water content of the sample, M₁Is the initial mass of the sample, M₂Is the sample mass of the sampling point in the drying process.

In the formula M₁And M₂The mass of the samples at two adjacent sampling points in the drying process is respectively shown, and t (h) is the interval time between two adjacent sampling points in the drying process.

4. The yield of the volatile oil is as follows: the dried pepper is extracted by adopting a steam distillation method, wherein the material-liquid ratio is 1: 5, extracting for 5h, and measuring the volume of the volatile oil after the extraction is finished. The volatile oil yield calculation formula is as follows:

in the formula, V is the volume of the volatile oil obtained by extraction, and M is the mass of the fresh plant (350 g in the experiment).

Example 6

Unlike example 5, the drying was carried out in a vacuum at a temperature of 60 ℃.

Example 7

Different from the example 5, the drying method is microwave vacuum drying, the microwave power is 480W, and the pressure is 100 Pa.

Example 8

Unlike example 5, the drying mode was far infrared drying and the power was 1000W.

Comparative example 1

1. Film coating pretreatment: film coating was omitted and fresh pricklyash peel was used as a control without film coating pretreatment.

2. And (3) drying: drying fresh fructus Zanthoxyli without film-coating pretreatment with hot air at 60 deg.C under 50mbar until the moisture content is less than 10%, and drying.

3. Drying kinetics: sampling and weighing every half hour in the drying process, calculating the water content corresponding to each time point in the drying process according to the initial water content of the pepper, and drawing a drying kinetic curve. And calculating the drying rate according to the change of the water content at two adjacent time points in the drying process, and drawing a change curve of the drying rate along with the time.

The water content calculation formula is shown in formula (1), and the drying rate calculation formula is shown in formula (2).

In the formula M₀As initial water content of the sample, M₁Is the initial mass of the sample, M₂Is the sample mass of the sampling point in the drying process.

In the formula M₁And M₂Respectively the sample mass of two adjacent sampling points in the drying process, and t (h) is the sample mass of two adjacent sampling points in the drying processThe interval of (c).

4. The yield of the volatile oil is as follows: the dried pepper is extracted by adopting a steam distillation method, wherein the material-liquid ratio is 1: 5, extracting for 5h, and measuring the volume of the volatile oil after the extraction is finished. The volatile oil yield calculation formula is as follows:

in the formula, V is the volume of the volatile oil obtained by extraction, and M is the mass of the fresh plant (350 g in the experiment).

Comparative example 2

Unlike comparative example 1, the drying manner was vacuum drying at a drying temperature of 60 ℃.

Comparative example 3

Different from comparative example 1, the drying method was microwave vacuum drying, the microwave power was 480W, and the pressure was 100 Pa.

Comparative example 4

Unlike comparative example 1, the drying mode was far infrared drying and the power was 1000W.

FIG. 1 is a graph showing changes in water content of a 2% carboxymethyl cellulose film and a 2% chitosan film without a film under hot air drying conditions. FIG. 2 is a graph showing changes in water content of a 2% carboxymethyl cellulose film and a 2% chitosan film without a film under hot air drying conditions. According to the experimental result, the film is not coated, the film is coated with 2% chitosan water solution and is treated with 2% carboxymethyl cellulose, the time required for drying until the water content reaches 8.64%, 8.73% and 8.79% is 780min, and the drying efficiency is not influenced by the pretreatment of the 2% chitosan water solution and the 2% carboxymethyl cellulose coating. The reason analysis is as follows: although the chitosan and the cellulose membrane can prevent the moisture in the material from vaporizing and evaporating from the surface, the chitosan and the cellulose membrane both have hydrophilicity and can absorb the moisture and water vapor which are diffused to the surface in the pepper, and further evaporate from the coating layer, so the resistance to hot vapor is small, and the drying efficiency is not reduced. As can be seen from the drying curve, the water content of the material after the coating pretreatment is increased because the membrane material contains 98 percent of water; in the early stage of drying, the drying rate of the film coating pretreatment is higher than that of the film coating pretreatment, because the water content of the film coating layer is high and is positioned on the surface of the pepper, the evaporation is easier; as drying proceeded, the drying curves for the coated and uncoated pre-treated samples nearly coincided, indicating that the coating layer did not affect the drying rate.

The yields of the volatile oils of examples 1 to 8 and comparative examples 1 to 4 are given in the following table:

the result shows that the oil yield of fresh pepper is 1.65%, the volatile oil yield shows a large difference after the sample subjected to film coating pretreatment and the sample not subjected to film coating pretreatment are dried, the oil yield of the sample subjected to pretreatment is obviously higher than that of the sample not subjected to pretreatment and can be increased by about 10% -50%, and the result proves that the oil yield of the sample subjected to film coating pretreatment can obviously improve the retention rate of pepper and is beneficial to protecting volatile oil components. The analysis reason is as follows: the coating layer is made of hydrophilic materials and is not dissolved with the fat-soluble volatile oil, so that the volatile oil can be effectively prevented from escaping through the coating layer after being vaporized from the interior of the pepper; meanwhile, the coating layer can form a skeleton structure between cell walls on the surfaces of the peppers, so that the mechanical strength of the surfaces of the peppers is enhanced, shrinkage in the drying process is reduced, oil chamber cells are protected, and the loss of volatile oil caused by the damage of the oil chamber cells is avoided.

The invention provides an example of using 2% of carboxymethyl cellulose and chitosan, but the dosage is not limited to the use amount, and can be 1-5%, and carboxymethyl cellulose and chitosan can also be used as materials with similar film properties such as starch, gelatin, methyl cellulose aqueous solution and the like.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art should be considered to be within the technical scope of the present invention, and the technical solutions and the inventive concepts thereof according to the present invention should be equivalent or changed within the scope of the present invention.