Problems in Storage of Dendrobium officinale and Study on Its Preservation Technology

Yingjun ZHOU

Huizhou Engineering Vocational College, Huizhou 516023, China

Abstract Due to extensive harvesting, the ecological environment of Dendrobium officinale has been destroyed, and there are very few wild D. officinale today. As the tissue culture technology of D. officinale continues to mature, there are more and more imitation, wild cultivation, greenhouse cultivation and other large-scale production of D. officinale to meet the market demand, but the storage and preservation of fresh products is a big problem. The existing problems in storage of D. officinale and its preservation technology are discussed, so as to provide some reference for the storage and preservation of D. officinale fresh products.

Key words Dendrobium officinale, Fresh products, Storage, Preservation technology

1 Introduction

DendrobiumofficinaleKimura et Migo is a perennial herbaceous epiphyte ofD.nobilein Orchidaceae. Most of the plants are attached to cliffs and rock crevices with bryophytes,Selaginellatamariscinaand lichens, and their bare roots absorb water from the air.D.officinalehas high ornamental value and medicinal value, with functions of nourishing yin and clearing heat, nourishing stomach and generating fluid, brightening eyes and strengthening waist[1]. At present,D.officinalein the market is mainly divided into fresh and dry products. Fresh products are fresh, not artificially processed, crisp and juicyD.officinaleproducts, with yellowish green or yellowish purple surface, slightly sweet taste, high nutritional value, emitting a smell of grass, but not easy to store. Dry products refer to processedD.officinaleproducts, such as Fengdou; after the green leaves ofD.officinalefresh products are removed and the moisture is removed by drying with charcoal fire, the product is kneaded into spring shape, which can be stored for a long time, but can not completely replaceD.officinalefresh products[2].

2 Current situation of industrial development

2.1 WildD.officinaleThere are more than 70 species ofDendrobiumin China, andD.officinaleis the treasure of food.D.officinalecan be harvested after 1-2 years, and is distributed in many regions of China, such as Yunnan, Guizhou, Sichuan,etc.Despite of broader growth range, the growth and development ofD.officinaleis very slow in the natural environment. Meantime, it has higher requirements on the surrounding environment in the growth process, and is often found in hot and humid tropical and subtropical forests, cliffs and gaps in the rocks.D.officinaleis also fragile, which will easily die in case of strong light, heavy rain and other severe weather. Meantime, because of unique medicinal value,D.officinalehas been over-picked by a lot of people in the field, so the number of wildD.officinaleis decreasing year by year.

2.2 Artificially cultivatedD.officinaleIn order to protect the number ofD.officinalein the field and ensure its normal reproduction,D.officinalewas identified as a second-class protected plant by the state in 1987 and was included in theProtectionandManagementofWildMedicinalMaterialsResourcesand was also identified as a key protected wild rare medicinal materials species[3]. Later,D.officinalewas included in the first batch ofListofRareandEndangeredProtectedplantsinChina, which further clarified the rare status ofD.officinale. Due to unique medicinal value, the artificial cultivation techniques ofD.officinalehave been widely developed to ensure the yield and application demand ofD.officinale. At present, there are large artificial cultivation bases ofD.officinalein Zhejiang, Yunnan, Guangxi,etc.In terms of the medicinal value ofD.officinale, many researchers found that there was no significant difference in the medicinal value between wildD.officinaleand artificially cultivatedD.officinalethrough numerical comparison. Therefore, it is not necessary to pursue wildD.officinale, and the effect of artificially cultivatedD.officinaleis also very good. Therefore, in order to protect wildD.officinale, many policies have been introduced to promote the construction of artificial cultivation base ofD.officinale.

2.3 Composition and efficacy ofD.officinaleThe reason whyD.officinaleis widely used is its unique medicinal value. The medicinal value ofD.officinalewas first recorded inShengNong’sHerbalClassic, claiming thatD.officinalehas the functions of "eliminating bi, replenifying qi", "thickening intestines and stomach, and extending life with light body"[4]. In theCollectedTaoistScriptures, a Taoist medicine classic written thousands of years ago,D.officinalewas listed as the top of the "nine immortal herbs of China", further confirming its medicinal value.

In the present study ofD.officinale, it is found thatD.offi-cinalehas the following functions. (i) Generating fluid and benefiting stomach. Xu Jianhuaetal.[5]proved thatD.officinalehad the function of nourishing yin and generating body fluid. Xiao Linetal.[6]suggested thatD.officinaleextract could promote the expression of aquaporin-5 in labial glands, and effectively improve the condition of patients with Sjögren’s syndrome. (ii) Anti-tumor and anti-mutation effects. Experiments on mice showed thatD.officinalealso had certain anti-tumor effects[7]. Xuetal.[8]also pointed out thatD.officinalehad certain anti-tumor components. (iii) Lowering blood glucose and blood pressure. Wu Haoshuetal.[9]found thatD.officinalecontained substances that could prevent diabetes. Wu Renzhaoetal.[10]put forward thatD.officinalecould produce certain therapeutic effects on patients with hypertension. (iv) Enhancing the immunity. Li Biaoetal.[11]suggested thatD.officinalehad certain antioxidant activity and also had the effect of enhancing human immunity.

2.4 Current situation of industrial developmentTraditional Chinese medicine (TCM) has developed for thousands of years in China, and one of the keys to TCM treatment lies in Chinese medicinal materials. Although the rise of modern medicine has caused great impact on the development of TCM, and more people choose western medicine for treatment in their daily life, it is undeniable that TCM still occupies a place in people’s hearts. Especially in recent years, people pay more and more attention to TCM, and health preservation with TCM has begun to revive. The upsurge of health preservation withD.officinaleis also rising, andD.officinaleindustry has risen rapidly. There are three main reasons for the rapid rise ofD.officinaleindustry. First of all,D.officinaleis widely used because of its special medicinal function, so it has a large market demand. Secondly,D.officinaleis now usually used as a drink. AfterD.officinaledrinks are released to public hospitals, they are reimbursed by medical insurance, which is another reason for the increased use ofD.officinale. Finally,D.officinalealso has certain role in health care.D.officinalefresh products have been used in the production and sales of health food, and get a lot of consumer trust.

However, the artificial cultivation technology ofD.officinaleis not mature enough, so the supply of freshD.officinalehas been insufficient. In order to meet the market demand, the cultivation technology research ofD.officinaleis also vigorously developed in China, andD.officinalecultivation base has been established in many areas. Although it has gone through more than 10 years of development, the construction scale of these bases is not large according to the current actual situation, the influence of the products produced is not deep enough, and the cultivation ofD.officinaleartificial cultivation technology is just in the initial stage.

3 Application of fresh D. officinale

3.1 Application advantages of freshD.officinale

3.1.1Richer nutritional value. Compared with dryD.officinale, fresh product has more health care effect. FreshD.officinalehas more nutritional value than dry products because dry product goes through roasting and drying, which will destroy some nutrients inD.officinale. In addition, studies have proved that freshD.officinalecan completely retain its medicinal effects, and is more easily absorbed than dry products[12], and the consumption ways are more diversified.

3.1.2Traditional Chinese medicine recommends the use of freshD.officinale. From the use ofD.officinale, fresh and dry products are the only two utilization ways. Although dry products are more widely used, fresh products in fact, have higher medicinal value, and it is more recommended to use freshD.officinalein TCM. When the famous doctor Wei Changchun usedD.officinaleas medicine, he designated to use freshD.officinale[13]. The use of fresh Chinese medicinal materials is also the experience summed up by thousands of years of TCM treatment, which has very high practical value.

3.1.3Effectively avoid fake and shoddy products. AfterD.officinaleis dried, it is not easy to distinguish its shape and appearance. It is impossible to tell whether it is made of authenticD.officinaleor other kinds of medicinal materials by naked eye observation, and even experts in this field can only tell by tasting. As a result, there are many substandardD.officinaledry products sold on the market, and consumers do not know that this is not authenticD.officinaleafter buying it home, so they spend their money and can not get the due curative effect.

However, freshD.officinalecan greatly reduce this kind of phenomenon, because fresh plants preserve their original forms and external features. As long as consumers have a little knowledge ofD.officinale, they can effectively distinguish whether the product is authenticD.officinalewhen they buy it, so they are not susceptible to cheating by bad vendors.

3.2 Application status and prospect of fresh productsOne of the characteristics of TCM treatment is the use of fresh drugs, especially in Beijing area, famous doctors prefer to use fresh drugs as medicine, and they always add 2-3 fresh drugs when prescribing prescriptions, with very good curative effect. For example, the famous doctor Xiao Longyou was particularly good at using fresh medicine, especially according to different seasons and different symptoms, and often used different fresh medicine products to improve the curative effect. Kong Bohua also believed that fresh medicine had special medicinal functions, and he had rich experience in using fresh medicine to treat acute fever. Therefore,D.officinalefresh products are more favored by TCM, and the application prospect is very broad.

4 Problems in storage of D. officinale

BecauseD.officinaleis still a living plant after being picked, it is prone to a variety of problems during the storage.

4.1 MouldBecauseD.officinaleis rich in nutrients, and most of plants grow in humid tropical and subtropical areas, it is easy to develop mold infection at the fracture point after picking, and it is easy to form mildew spots. Mould mycelia will spread from the fracture to the middle in the propagation process, and gradually infect the wholeD.officinalefresh products, thus making it lose its original value, which not only will cause losses to the merchants, but also is a waste ofD.officinalematerials.

4.2 Sour and ethanol flavorManyD.officinaleproducts are sealed in vacuum packaging bags. If stored at room temperature for a period of time,D.officinaleproducts will develop sour taste and ethanol fermentation taste. And with the increase of storage time, the taste will become stronger, seriously affecting the quality ofD.officinaleproducts. This condition may be related to the physiological metabolism and anaerobic respiration ofD.officinaleafter harvesting. In addition, it is possible to discolorD.officinalewhen sealed in vacuum bags. Moreover, ifD.officinaleis not vacuum-packed, but in an aerobic environment, appropriate humidity may also cause the phenomenon of germination.

4.3 Weight lossThrough the study under the same storage temperature and humidity conditions, it was found that the weight loss rate of packagedD.officinalewould reach about 10% at 90 d post storage, while the weight loss rate of unpackagedD.officinalewould reach astonishing 54% at 90 d post storage, with very significant difference. There was no significant change in the data at low temperature or indoor storage. However, when unpackagedD.officinalewas stored in air-cooled refrigeratory, the effect on weight loss rate would be more obvious.

4.4 Condensate waterD.officinalestill performs respiration and transpiration after picking, so it is easy to produce condensed water droplets after packaging. After long-term observation of this phenomenon, it is concluded that: when the condensed water droplets come into contact withD.officinale, it is more likely forD.officinaleto breed mold, and may cause rot and deterioration ofD.officinale, which greatly affects the product quality ofD.officinale.

4.5 Fibrotic tasteAlthoughD.officinalecan be stored effectively for a period of time through refrigeration or other technical means to ensure thatD.officinaledoes not deteriorate, such storage will makeD.officinalelose its original fresh crisp taste, and make the taste become fibrosis. This change is probably due to the normal physiological metabolism and microbial reproduction ofD.officinaleafter harvesting.

5 Preservation technology

In order to explore the preservation technology ofD.officinale, the first step is to study its growth cycle. Generally, the growers will choose to plantD.officinalefor 1-2 years before harvest, because studies have shown that there is no great difference in the medicinal efficacy ofD.officinaleplanted for two or three years[14].D.officinaleleaves have a similar growth cycle to normal plants, which will germinate in the spring. They can be picked in November and all the way up to May. But onceD.officinalehas not been harvested beyond May, the stems start to dry out and its medicinal value becomes extremely low. Therefore, from the perspective of growth cycle, the supply time ofD.officinalefresh products is generally about only 7 months, but in some coastal more developed areas, July every year is the exuberant consumption period of newD.officinaleproducts. If you want to sell freshD.officinaleproducts in July, it is necessary to do a good job ofD.officinalestorage.

5.1 Refrigeration methodAt present, the refrigeration method is the most widely used fresh-keeping method, which controls the storage temperature of fresh products at 0-5 ℃. AfterD.officinaleis picked and cleaned, it is bagged according to the corresponding specifications, and then stored in a 0 ℃ freezer. In this way, the preservation period of freshD.officinalecan be extended for 2-3 months. It is obvious that the advantage of refrigeration method is that fresh products can be kept fresh for a long time and can be used on a large scale.

5.2 Quick-frozen and low-temperature preservationRefrigeration is the basis for the development of low-temperature preservation, and the main difference between refrigeration and low-temperature preservation is the difference in temperature. The products are stored at a temperature of 0-5 ℃ in refrigeration method, while fresh products are quickly frozen at -30 ℃ and then preserved at -18 ℃ in quick-frozen and low-temperature preservation, which can effectively extend the preservation period from 6 months to a year. Although this method can prolong the life of fresh products, it actually has two huge drawbacks. Firstly, the quality ofD.officinaleis sharply reduced after thawing, andD.officinalethawed in this way is more likely to rot at room temperature. Secondly, the use of quick-frozen and low-temperature preservation has an impact on sales and transportation. General sales and transportation methods are no longer applicable, and need to be improved and upgraded, resulting in increased costs.

6 Conclusions

The rich medicinal properties ofD.officinalemake it an important ingredient in both prescription medicine and health food. Meantime, the fresh products ofD.officinalehave higher medicinal value than dry products, so it is of good practical significance to open the market and improve profits ofD.officinaleby exploring the problems existing in storage and preservation technology ofD.officinalefresh products. Therefore, the preservation ofD.officinaleis analyzed by refrigeration method and quick-frozen and low-temperature preservation, in order to explore a better method of preservation.