Processing method of lithocarpus litseifolius

Abstract

The invention belongs to the field of food processing, and particularly relates to a processing method of lithocarpus litseifolius, which comprises the following steps: carrying out microwave fixation on lithocarpus litseifolius leaves; performing vacuum low-temperature drying on the Lithocarpus litseifolius leaves subjected to fixation treatment until the water content is 30-45%; and performing vacuum freeze drying to obtain the lithocarpus litseifolius leaves with the water content of 5-7%. Through fixation, the browning degree of the lithocarpus litseifolius leaves is reduced, and the color of the lithocarpus litseifolius leaves can be better reserved. Lithocarpus litseifolius flavonoid substances are easy to oxidize, and through vacuum low-temperature drying or vacuum freeze drying, on one hand, the drying time can be shortened, and on the other hand, the retention rate of flavones of the finally obtained product is high in a vacuum environment. In the subsequent brewing stage, the obtained lithocarpus litseifolius can slowly dissolve out flavonoid substances, the brewing time can be properly prolonged, and the lithocarpus litseifolius can be brewed for multiple times.

Description

Technical Field

[0001] The invention belongs to the field of food processing, and particularly relates to a processing method of Ligusticum chuanxiong. Background Art

[0002] Lithocarpus litseifolius (Hance) Chun belongs to the genus Lithocarpus of the Fagaceae family. People pick its young leaves and make tea for drinking. Lithocarpus litseifolius is a tree with hairless branches and leaves. The leaves are papery to nearly leathery. The leaves are elliptical, obovate-elliptical or ovate, with acuminate or short cusps at the top, cuneate to wide cuneate at the base, entire margin, and the midrib is raised on the leaf surface. The male spike inflorescence is arranged in a panicle, and the female inflorescence usually has 2-6 spikes clustered at the top of the branch. The cupule is shallow saucer-shaped or short funnel-shaped with a wide top and narrow bottom. The nut is a wide conical or nearly spherical nut with a cone-shaped top, chestnut brown or reddish brown. Its young leaves are sweet and viscous when chewed. Most mountain residents in the south of the Yangtze River use its leaves as a tea substitute, commonly known as sweet tea. The flavonoids it contains have antioxidant and cholesterol-lowering effects, making it an ideal natural antioxidant. However, during the processing, different processing techniques will cause partial loss of flavonoids in tea. Therefore, how to reduce flavonoid loss and improve product quality is the key to enhancing competitiveness in the market. Summary of the invention

[0003] In order to solve the above-mentioned deficiencies of the prior art, a processing method of Ligusticum chuanxiong is provided, which can effectively reduce the loss of Ligusticum chuanxiong during the processing and improve the product quality.

[0004] The purpose of the present invention is achieved through the following technical solutions:

[0005] A method for processing Litsea cubeba comprises the following steps:

[0006] 1) Microwave sterilization of the leaves of Ligusticum chuanxiong;

[0007] 2) The leaves of the Artemisia selengensis leaf blade that have been treated with greening are vacuum dried at low temperature to a moisture content of 30-45%;

[0008] 3) Vacuum freeze drying to obtain leaves of Alpinia zedoaria with a water content of 5-7%.

[0009] Preferably, the microwave power in step 1) is 400-500 W and the time is 5-6 min.

[0010] Preferably, the vacuum degree of the vacuum low-temperature drying in step 2) is 0.03-0.06 MPa.

[0011] Preferably, the vacuum low-temperature drying temperature in step 2) is 30°C to 50°C.

[0012] Preferably, the pre-freezing temperature of the vacuum freeze-drying in step 3) is -40°C to -50°C, and the pre-freezing time is 1-2h.

[0013] Preferably, the temperature of the sublimation stage of the vacuum freeze drying in step 3) is increased from 0°C to 40°C at a rate of 0.5h / 10°C.

[0014] The present application reduces the browning degree of the leaves of the Ligustrum lucidum by killing the green, and can better retain the color of the leaves of the Ligustrum lucidum. The flavonoids of the Ligustrum lucidum are easily oxidized. On the one hand, vacuum low-temperature drying or vacuum freeze drying can reduce the drying time, and on the other hand, the flavonoid retention rate of the final product is high under a vacuum environment. In the subsequent brewing stage, the obtained Ligustrum lucidum can slowly dissolve the flavonoids, the brewing time can be appropriately extended, and multiple brewing can be performed. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below in conjunction with specific examples, but the embodiments of the present invention are not limited to the scope represented by the examples. These examples are only used to illustrate the present invention, but are not used to limit the scope of the present invention. In addition, after reading the content of the present invention, those skilled in the art can make various modifications to the present invention, and these equivalent changes also fall within the scope limited by the appended claims of the present invention.

[0016] Example 1

[0017] (1) Collect the young leaves of Ligusticum chuanxiong, wash them and drain the surface water. Microwave sterilize the leaves of Ligusticum chuanxiong with a microwave power of 400 W and a time of 5 min.

[0018] (2) The leaves of the Ligusticum chuanxiong that had been treated with withering were subjected to vacuum low-temperature drying, and the vacuum degree of the vacuum low-temperature drying was set to 0.03 MPa and the temperature was set to 30° C. to obtain Ligusticum chuanxiong leaves with a water content of 30%.

[0019] (3) Vacuum freeze drying is then performed. The leaves of the Ligustrum lucidum obtained in the above step are pre-frozen at -40°C for 1 hour, the cold trap temperature of the freeze dryer is set to -45°C, the vacuum degree of vacuum freeze drying is 30Pa, and the temperature of the sublimation stage of vacuum freeze drying is increased from 0°C to 40°C at a rate of 0.5h / 10°C, and finally Ligustrum lucidum leaves with a water content of 5% are obtained.

[0020] Example 2

[0021] (1) Collect the young leaves of Ligusticum chuanxiong, wash them and drain the surface water. Microwave sterilize the leaves of Ligusticum chuanxiong with a microwave power of 450 W and a time of 5 min.

[0022] (2) The leaves of the Ligusticum chuanxiong that had been treated with greening were subjected to vacuum low-temperature drying, and the vacuum degree of the vacuum low-temperature drying was set to 0.05 MPa and the temperature was set to 40° C. to obtain Ligusticum chuanxiong leaves with a water content of 35%.

[0023] (3) Vacuum freeze drying is then performed. The leaves of the Ligustrum lucidum obtained in the above step are pre-frozen at -45°C for 1.5 h, the cold trap temperature of the freeze dryer is set to -45°C, the vacuum degree of vacuum freeze drying is 40 Pa, and the temperature of the sublimation stage of vacuum freeze drying is increased from 0°C to 40°C at a rate of 0.5h / 10°C, and finally Ligustrum lucidum leaves with a water content of 6% are obtained.

[0024] Example 3

[0025] (1) Collect old leaves of Ligusticum chuanxiong, wash them and drain the surface water. Microwave sterilize the leaves of Ligusticum chuanxiong with a microwave power of 500 W and a time of 6 min.

[0026] (2) The leaves of the Ligusticum chuanxiong that had been treated with greening were vacuum-dried at low temperatures, and the vacuum degree of the vacuum-drying process was set to 0.06 MPa and the temperature was set to 50° C. to obtain Ligusticum chuanxiong leaves with a water content of 45%.

[0027] (3) Vacuum freeze drying is then performed. The leaves of the Ligustrum lucidum obtained in the above step are pre-frozen at -50°C for 2 h, the cold trap temperature of the freeze dryer is set to -45°C, the vacuum degree of vacuum freeze drying is 50 Pa, and the temperature of the sublimation stage of vacuum freeze drying is increased from 0°C to 40°C at a rate of 0.5h / 10°C, and finally Ligustrum lucidum leaves with a water content of 7% are obtained.

[0028] Example 4

[0029] Refer to the method of Example 1, except that step (2) produces leaves of Ligusticum chuanxiong with a water content of 35%.

[0030] Example 5

[0031] Refer to the method of Example 1, except that step (2) produces leaves of Ligusticum chuanxiong with a water content of 40%.

[0032] Example 6

[0033] Refer to the method of Example 1, except that step (2) produces leaves of Ligusticum chuanxiong with a water content of 45%.

[0034] Comparative Example 1

[0035] Refer to the method of Example 1, except that step (2) produces leaves of Ligusticum chuanxiong with a water content of 25%.

[0036] Comparative Example 2

[0037] Refer to the method of Example 1, except that step (2) produces leaves of Ligusticum chuanxiong with a water content of 50%.

[0038] The dried leaves of Ligustrum lucidum obtained in the examples and comparative examples were crushed with a grinder and passed through a 0.250 mm sieve to prepare the test tea samples. The test tea samples were extracted in boiling water at a ratio of 0.2% tea to water for 2 minutes, and stirred several times during the extraction. After the extraction was completed, the leaves were cooled naturally and filtered with a quantitative filter paper to obtain the sample tea soup.

[0039] According to the method established in the literature (Xia Xu, Yu Zhuosi, Lu Zonghao, Yang Jianlin, Hu Yingxiang, Xiang Xiaole; ​​Processing stability of total flavonoids in ginger leaf tea; Food Industry; Issue 12, 2022), the standard curve of rutin was drawn and the total flavonoids of Ligusticum chuanxiong were determined. 200 mg of rutin standard was accurately weighed in a 100 mL volumetric flask and fixed to volume with 70% methanol as the mother solution. 0, 0.5, 1, 2, 3 and 4 mL of rutin mother solution were respectively placed in 25 mL volumetric flasks, 70% methanol was added to 10 mL, and 1 mL of 5% NaNO2 solution was added, shaken, and placed for 6 min; 1 mL of 10% Al(NO3)3 aluminum nitrate solution was added, shaken, and placed for 6 min; 10 mL of 4% NaOH sodium hydroxide solution was added, and 70% methanol was added to dilute to the scale, shaken, and placed for 15 min; the blank reagent was used as a reference, and the standard curve of rutin and the total flavonoids of Ligusticum chuanxiong were drawn at a wavelength of 510 nm.

[0040] The total flavonoids contained in the tea obtained by soaking the dried leaves of Ligusticum chuanxiong prepared in each embodiment and comparative example are shown in Table 1:

[0041] Table 1 Total flavonoids content of dried leaf tea of ​​Ligusticum chuanxiong in various embodiments and comparative examples

[0042] Total flavonoids content (mg / mL) Example 1 0.016 Example 4 0.011 Example 5 0.007 Example 6 0.014 Comparative Example 1 0.022 Comparative Example 2 0.025

[0043] As shown in Table 1, the moisture content of the leaves of Ligusticum chuanxiong is 30-45% after vacuum low-temperature drying. The total flavonoids dissolved in the dry leaves obtained by subsequent vacuum freeze-drying are relatively slow. The brewing time can be appropriately extended, and the leaves can be brewed multiple times to savor the flavor of the Ligusticum chuanxiong.

Claims

1. A method for processing Ligustrum lucidum, characterized in that: The method comprises the following steps: 1) Microwave sterilization of the leaves of Ligusticum chuanxiong; 2) The leaves of the Artemisia selengensis leaf blade that have been treated with greening are vacuum dried at low temperature to a moisture content of 30-45%; 3) Vacuum freeze drying to obtain leaves of Alpinia zedoaria with a water content of 5-7%.

2. The processing method of Ligusticum chuanxiong according to claim 1, characterized in that: The microwave power in step 1) is 400-500W, and the time is 5-6min.

3. The processing method of Ligusticum chuanxiong according to claim 1, characterized in that: The vacuum degree of the vacuum low-temperature drying in step 2) is 0.03-0.06 MPa.

4. The processing method of Ligusticum chuanxiong according to claim 3, characterized in that: The vacuum low-temperature drying temperature in step 2) is 30°C to 50°C.

5. The processing method of Ligusticum chuanxiong according to claim 1, characterized in that: The pre-freezing temperature of the vacuum freeze drying in step 3) is -40°C to -50°C, and the pre-freezing time is 1-2h.

6. The processing method of Ligusticum chuanxiong according to claim 5, characterized in that: The temperature of the sublimation stage of the vacuum freeze drying in step 3) is increased from 0°C to 40°C at a rate of 0.5h / 10°C.