阅读说明：本技术 一种铁皮石斛冷冻干燥方法 (Dendrobium officinale freeze-drying method ) 是由 方良材 黄卫萍 黄少军 黄春秋 蒋瑜 戴传勇 于 2020-03-27 设计创作，主要内容包括：本发明公开了一种铁皮石斛冷冻干燥方法,包括熏蒸,保压,预冻,冷冻,升华等步骤。采用本发明的方法得到的铁皮石斛产品无表面硬化,组织呈多孔海绵状,加水后复水速度快,几乎立即恢复原来的性质,生物碱和多糖等物质在热水中的溶出率高,溶出速率快,挥发油成分相对其新鲜品来说损失量较小,有效保留了较多的挥发性成分,其品质与鲜品基本相同,营养成分损失小；增加了其营养价值和保健作用,即食方便。并且重量轻,耐保藏,对环境温度没有特别的要求,产品经过真空包装或充氮包装和避光保存,保质期长。更有利于铁皮石斛在贮存过程中的稳定性,对提高其市场竞争力,增加经济效益均有重要意义。(The invention discloses a freeze drying method of dendrobium officinale, which comprises the steps of fumigating, pressure maintaining, pre-freezing, subliming and the like. The dendrobium officinale product obtained by the method has no surface hardening, the tissue is in a porous sponge shape, the rehydration speed is high after water is added, the original property is almost immediately recovered, the dissolution rate of alkaloid, polysaccharide and other substances in hot water is high, the dissolution rate is high, the loss amount of volatile oil components is small compared with that of fresh products, more volatile components are effectively reserved, the quality of the volatile oil components is basically the same as that of the fresh products, and the loss of nutritional components is small; the nutritional value and the health care effect of the instant noodles are increased, and the instant noodles are instant and convenient. The product is light in weight, resistant to preservation and free of special requirements for environmental temperature, and is long in shelf life after being subjected to vacuum packaging or nitrogen-filled packaging and light-proof preservation. Is more beneficial to the stability of the dendrobium officinale in the storage process, and has important significance for improving the market competitiveness and increasing the economic benefit.)

1. A freeze-drying method of dendrobium officinale is characterized by comprising the following steps:

(1) fumigating: cutting the dendrobium officinale into segments, cleaning, draining surface water, fumigating with ethanol steam for 1-3 min, and cooling to room temperature;

(2) pressure maintaining: putting the dendrobium officinale into a high-pressure tank, filling nitrogen, adjusting the pressure in the high-pressure tank to be 100-260 MPa, maintaining the pressure for 1.5-3 min, and relieving the pressure to normal pressure;

(3) pre-freezing: taking out the dendrobium officinale obtained in the step (2), quickly transferring the dendrobium officinale into a freezer after absorbing the surface moisture, reducing the temperature of the dendrobium officinale to-40 to-30 ℃ within 1-2 h, and then freezing the dendrobium officinale at constant temperature for 1-2 h to finish pre-freezing;

(4) freezing: taking out the dendrobium officinale subjected to the pre-freezing in the step (3), placing the dendrobium officinale in a freeze dryer at the temperature of-70 to-65 ℃, replacing air in the freeze dryer with low-temperature nitrogen, enabling the air pressure in the freeze dryer to be higher than the standard atmospheric pressure, and keeping the pressure and the temperature to continuously freeze for 1.5 to 3 hours;

(5) sublimation: and adjusting the vacuum degree in the freeze dryer to 10-20Pa, controlling the temperature to rise to 18-20 ℃ at the speed of 0.5-1.5 ℃/min, and keeping the temperature for 1-2 h to finish freeze drying.

2. The freeze-drying method of Dendrobium officinale according to claim 1, wherein in step (1), Dendrobium officinale is cut into 2-5 cm small sections, cleaned, blown to the surface with gas at 15-20 ℃ until the surface is dried, and then fumigated.

3. The method for freeze-drying Dendrobium officinale Kimura et Migo as claimed in claim 1, wherein the temperature of the ethanol vapor is controlled not to be higher than 80 ℃ during the fumigation with the ethanol vapor in step (1).

4. The freeze-drying method for dendrobium officinale according to claim 1, wherein the pressure relief of the high-pressure tank in the step (2) is completed within 0.2-0.4 min.

5. The freeze-drying method for dendrobium officinale according to claim 1, wherein the cooling rate of dendrobium officinale in step (3) is controlled to be 0.5-1 ℃/min.

6. The freeze-drying method for dendrobium officinale according to claim 1, wherein the temperature of the low-temperature nitrogen in the step (4) is-10-0 ℃.

7. The method for freeze-drying Dendrobium officinale Kimura et Migo according to claim 1, wherein in step (4), after replacing air in the freeze-dryer with low-temperature nitrogen gas, the pressure in the freeze-dryer is 0.1-0.5kPa higher than the standard atmospheric pressure.

Technical Field

The invention relates to the field of food processing, and particularly relates to a freeze-drying method of dendrobium officinale.

Background

Dendrobium officinale Kimura et Migo is a dried stem of perennial epiphytic herbaceous plant of Dendrobium of Orchidaceae, is a famous and precious traditional Chinese medicinal plant, has sweet and slightly cold nature, enters stomach and kidney channels, has the effects of benefiting stomach and promoting fluid production, nourishing yin and clearing heat, and is used for treating fever and body fluid injury, dry mouth and polydipsia, stomach yin deficiency, anorexia and retching, after-disease deficiency heat unremoved, yin deficiency and fire excess, bone steaming and fatigue heat, dim and poor vision, and flaccidity bones and bones. Dendrobium officinale is a precious or endangered medicinal material, called as panda in the pharmaceutical kingdom in the international medicinal plant community, and called as life-saving Mesona chinensis by people. Modern clinical application and pharmacological research prove that the dendrobium officinale has the magical effects of nourishing yin and moisturizing lung, nourishing stomach and promoting fluid production, strengthening brain and improving eyesight, protecting liver and calming heart, clearing heat and reducing internal heat, tonifying consumptive disease of five internal organs, reducing weight and prolonging life. Has definite curative effect and conditioning and rehabilitation effect on diseases such as chronic fatigue syndrome, lung disease, coronary heart disease, nephropathy, chronic liver disease, hypertension, hyperlipidemia, hyperglycemia, diabetes, chronic gastropathy, sicca syndrome, cancer and the like. It also has effects of enhancing immunity, resisting oxidation, and resisting aging, and has special therapeutic effect on excessive smoking and drinking, overwork, overuse of night life, eye use brain, hoarseness, dry mouth and tongue, and asthenia and yin deficiency of old people.

Although the fresh dendrobium officinale product has high nutritive and medicinal values, the preservation time is short, and strict requirements are imposed on the preservation temperature, humidity and preservation conditions, which brings certain limitations to practical use. The stem of Dendrobium officinale Kimura et Migo is processed and twisted into spiral or spring shape while baking, and is called as maple funnel. The dendrobium officinale mainly has high polysaccharide content and tough stem skin, and is extremely difficult to dry in a straight line manner; twisting into spiral or spring shape can squeeze the stem meat and break the stem skin, so as to dry the water. Although the preservation problem is solved, the heat-sensitive active substances in the dendrobium officinale are damaged in the high-temperature processing process, the dendrobium officinale is hard and needs to be soaked or boiled by hot water, the dendrobium officinale can not be flexibly and immediately used, the mouthfeel of sticking teeth, having sweet taste after chewing and having more meat and less residues is lost, and the dendrobium officinale is inconvenient to eat and use.

Vacuum freeze drying, freeze drying for short, is a drying technique in which a wet material or solution is frozen into a solid state at a relatively low temperature, then the moisture in the wet material or solution is directly sublimated into a gaseous state without passing through the liquid state under vacuum, and finally the material is dehydrated. Lyophilization can maintain a bright appearance, good mouthfeel, and heat-sensitive active substances, such as lyophilized lemon slices. But the freeze-drying of the dendrobium officinale is difficult, the dendrobium officinale is generally cut into thin slices in the prior art, and the uniform freeze-drying is difficult if the thickness is slightly larger; or after cutting, the stem skin is punched with a needle to form dense holes, so that the product is poor in selling.

The research shows that the volatile components of the dendrobium officinale (excluding flowers) are researched and separated into 19 peaks by adopting a headspace solid phase microextraction method, 14 compounds are identified by combining retention indexes and matching degrees, and account for about 78.31 percent, and the whole herb of the dendrobium officinale also contains nonanal.

Disclosure of Invention

The invention aims to overcome the defects in the prior art and provides a freeze drying method for dendrobium officinale.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the dendrobium officinale freeze-drying method comprises the following steps:

(1) fumigating: cutting the dendrobium officinale into segments, cleaning, draining surface water, fumigating with ethanol steam for 1-3 min, and cooling to room temperature;

(2) pressure maintaining: putting the dendrobium officinale into a high-pressure tank, filling nitrogen, adjusting the pressure in the high-pressure tank to be 100-260 MPa, maintaining the pressure for 1.5-3 min, and relieving the pressure to normal pressure;

(3) pre-freezing: taking out the dendrobium officinale obtained in the step (2), quickly transferring the dendrobium officinale into a freezer after absorbing the surface moisture, reducing the temperature of the dendrobium officinale to-40 to-30 ℃ within 1-2 h, and then freezing the dendrobium officinale at constant temperature for 1-2 h to finish pre-freezing;

(4) freezing: taking out the dendrobium officinale subjected to the pre-freezing in the step (3), placing the dendrobium officinale in a freeze dryer at the temperature of-70 to-65 ℃, replacing air in the freeze dryer with low-temperature nitrogen, enabling the air pressure in the freeze dryer to be higher than the standard atmospheric pressure, and keeping the pressure and the temperature to continuously freeze for 1.5 to 3 hours;

(5) sublimation: and adjusting the vacuum degree in the freeze dryer to 10-20Pa, controlling the temperature to rise to 18-20 ℃ at the speed of 0.5-1.5 ℃/min, and keeping the temperature for 1-2 h to finish freeze drying.

Preferably, the dendrobium officinale in the step (1) is cut into small sections of 2-5 cm, the small sections are cleaned, then the surfaces of the small sections are blown by gas at the temperature of 15-20 ℃ until the surfaces are dried, and then fumigation is carried out.

Preferably, when the ethanol steam is used for fumigation in the step (1), the temperature of the ethanol steam is controlled to be not more than 80 ℃,

preferably, the pressure relief of the high-pressure tank in the step (2) is completed within 0.2-0.4 min.

Preferably, the cooling rate of the dendrobium officinale in the step (3) is controlled to be 0.5-1 ℃/min.

Preferably, the temperature of the low-temperature nitrogen in the step (4) is-10 to 0 ℃.

Preferably, after replacing the air in the freeze dryer with low-temperature nitrogen gas in the step (4), the pressure in the freeze dryer is made higher than the standard atmospheric pressure by 0.1 to 0.5 kPa.

Due to the adoption of the technical scheme, the invention has the following beneficial effects:

1. according to the invention, the dendrobium officinale is subjected to high-pressure maintaining before freeze drying, so that the surface and internal structures of traditional Chinese medicinal materials are effectively damaged, the structure of the traditional Chinese medicinal materials becomes loose, the tissue of the dendrobium officinale is in a porous sponge shape after the normal pressure is recovered, nitrogen is used for protection in the pressure maintaining process, the dendrobium officinale processing process is prevented from reacting with air, and the nutrient components, the shape, the natural color, the tissue structure and the flavor substances of the dendrobium officinale are maintained. Secondly, after high-pressure maintaining, pre-freezing and freezing are carried out, so that internal water is frozen into ice crystals, a stable solid framework structure is formed, nitrogen protection is adopted during freezing and is slightly larger than standard atmospheric pressure, the freezing point is reduced along with the increase of pressure below 2200 atmospheric pressure, the nucleation temperature for forming ice nuclei is increased, the problem that some bacteria (such as pseudomonas) synthesize protein which is helpful for forming ice nuclei in cold water solution in the freeze drying process, and the nucleation temperature for forming ice nuclei is increased is solved, and the product meets the regulations and the permission of FDA for freeze-dried pharmaceutical products. After freezing, drying at low temperature and low pressure can avoid loss or inactivation of heat-sensitive substances and volatile components of Dendrobium officinale, and the low pressure is anoxic, so that the easily-oxidizable components cannot be oxidized and deteriorated.

2. The dendrobium officinale provided by the invention is subjected to desorption drying after sublimation drying of the ice crystals, so that the dendrobium officinale is more sufficiently dried, and the storage stability of the dendrobium officinale is improved. On the premise of ensuring the product quality, the energy consumption is saved to the maximum extent, the freeze-drying time is shortened, and the defects of deformation, drying shrinkage, surface bulging, whitish color, poor crispy and delicious taste, reduction of effective components and the like caused by over-quick temperature rise are avoided. Is beneficial to improving the taste of the dendrobium officinale, improves the crispness of the dendrobium officinale and avoids the phenomenon of sticking teeth on the premise of not reducing the viscosity.

3. According to the invention, before high-pressure maintaining, the fresh dendrobium officinale product is fumigated by using ethanol steam, so that the generation rate of superoxide anions is inhibited, the activities of PPO and POD enzymes are reduced, the browning of the dendrobium officinale is inhibited, the content of reducing sugar is inhibited, bacteria on the surface of the dendrobium officinale are effectively killed, and the nutritive value and the freshness of the dendrobium officinale product are improved.

4. Tests prove that after the dendrobium officinale product is subjected to ultrahigh pressure and freeze-drying treatment, the dissolution amount and dissolution rate of active substances, namely dendrobium polysaccharide and dendrobine, in the freeze-dried dendrobium officinale product are remarkably increased in hot water, and the bioavailability is fully improved.

In conclusion, the processing technology of ethanol steam fumigation, high-pressure maintaining and freeze drying can destroy the texture and the connection and isolation among middle molecules of the dendrobium officinale, improve alkaloid and polysaccharide in the dendrobium officinale, prevent volatile oil components of the dendrobium officinale from being easily volatilized due to sudden reduction of environmental pressure in the freeze drying process, obtain the dendrobium officinale product without surface hardening, enable the tissue to be in a porous sponge shape, enable the rehydration speed to be fast after water is added, almost immediately recover the original properties, enable the dissolution rate of the alkaloid, polysaccharide and other substances in hot water to be high, enable the dissolution rate to be fast, enable the loss of the volatile oil components to be small compared with fresh products, effectively reserve more volatile components, enable the quality of the volatile oil components to be basically the same as fresh products and enable the loss of nutritional components to be small; the nutritional value and the health care effect of the instant noodles are increased, and the instant noodles are instant and convenient. The product is light in weight, resistant to preservation and free of special requirements for environmental temperature, and is long in shelf life after being subjected to vacuum packaging or nitrogen-filled packaging and light-proof preservation. Is more beneficial to the stability of the dendrobium officinale in the storage process, and has important significance for improving the market competitiveness and increasing the economic benefit.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention will be described in further detail below with reference to preferred embodiments. It should be noted, however, that the numerous details set forth in the description are merely for the purpose of providing the reader with a thorough understanding of one or more aspects of the present invention, which may be practiced without these specific details.