1 The quality of high-quality shiitake mushrooms
The quality of linden shiitake mushrooms includes morphological quality, nutritional quality and commodity quality. Take the standard of dried shiitake mushroom made by China National Corporation for Import and Export of Native Specialties as follows: the form should be round and square, the body of mushroom is light chestnut brown with scales; the size of mushroom cap is above 4cm, the edge is inwardly rolled and the cap is flat-topped; the mushroom meat is thick and solid, and the shank is thick and short. If there are longitudinal cracks on the surface of the cap, with deep and white flesh that makes the whole body appear white, and if the moisture content meets the standard after baking and the flavor is strong, then this is the flower mushroom, the most beautiful of all mushrooms. Under natural conditions, the incidence of Flowering Mushroom is 6%. In some places, the rate of flower mushroom can reach 25% in individual years. In the south of Gansu in China, the Bailongjiang River, Jialing River upstream and Baishui River, West Han River area, every year in the spring and fall season, often subject to the influence of the northwest dry and cold airflow, linden flower mushroom rate of more than 35% [1], to become China's high-grade linden shiitake mushrooms, one of the suitable production areas.
High-quality linden shiitake mushrooms are processed and eaten after foaming, the mushroom meat is solid, tough and brittle, the mushroom soup is clear but not muddy, and the flavor is strong and fresh. In addition to the Flower Mushroom, there is also the Thick Mushroom, which is a type of Flower Mushroom without a pattern. Both the Flower Mushroom and the Thick Mushroom have the same characteristics as the Large Mushroom, the Thick Meat, the Inwardly Rolled Cap and the Short Stalk, etc***. Domestic and foreign market sales show that the price of high-quality shiitake mushrooms per unit weight is 10-20 times that of ordinary shiitake mushrooms.
2 Natural conditions of linden shiitake mushroom
Shiitake mushroom belongs to wood-rotting fungi, which can decompose and corrode the wood with huge mycelium, and convert the main components of wood, such as cellulose, hemicellulose, lignin, sugar, protein, etc. into nutrients of mycelium. Unlike general wood-rotting fungi, shiitake mushrooms can decompose lignin as the main carbon nutrient, and lignin accounts for about 20% to 30% of the mature wood components. Shiitake mushrooms can produce polyphenol oxidizing enzymes, of which laccase and guaiacol oxidase are the most important, which can convert insoluble aromatic polymer components of wood into water-soluble simple compounds containing benzene rings, which are finally destroyed to produce organic small molecule compounds that can be absorbed by the mycelium [2]. This property of mushroom mycelium is not only essential for the production of mushroom substrates, but also an important step in the degradation of lignin and the multistage recycling of elements in wood and many kinds of crop straws in nature.
The production process of linden shiitake is the process of transforming linden wood components into shiitake mushrooms. This process is divided into the period of mycelium colonization, mycelium spreading period, the formation of the substrate of the substrate and the substrate growth period, and each period can not be separated from the cooperation of suitable natural environmental conditions. Mycelium can grow at 5-32 ℃, air relative humidity above 60%, of which 22-26 ℃ is the optimal temperature for mycelium growth. Mycelium colonization period and mycelium spreading period should be centered on controlling the temperature, in order to achieve the survival rate of mycelium colonization of more than 90%, mycelium in linden wood along the longitudinal, transverse, tangential and other directions in three-dimensional three-dimensional space to spread rapidly. Rely on its mycelium of a variety of enzyme system decomposition, absorption of mushroom wood in a variety of nutrients, such as water, carbohydrates, nitrogenous compounds and a variety of mineral elements, etc., and will be stored in the mycelium or used for mycelium to continue to reproduce and grow. After the mushroom wood is decomposed by the mycelium, its degree of decay increases and the void degree within the wood increases. Tests have shown that mycelial growth in mushroom wood reaches its maximum when the moisture within the wood reaches about 60% of the saturated moisture content. This is also the period when the maximum number of mushroom fruiting bodies occurs. It takes about 5 to 6 years for the inoculated mushroom wood to completely decay, and the production of shiitake mushrooms reaches its maximum in the second to fourth cultivation years. When the mycelium fully occupies the mushroom wood, sucks up enough rich nutrients and enters physiological maturity to become a nutritive mycelium, it can only accept the induction of low temperature, light, biochemical changes and various stimuli, such as scratching the mushroom, artificial handling, lightning and vibration, and so on. Under the action of a series of comprehensive factors, light is the first factor which can make the nutritive mycelium under the bark of mushroom wood to form some white disk-shaped mycelial aggregates, which is the original substrate of the initial fruiting body. Under the action of the low temperature factor, a series of physiological changes take place in the substrate, and the mushroom stalk, cap and gill are differentiated. After the initial differentiation of the substrate base, the nutrients stored in the nutrient mycelium and the mycelium continue to absorb nutrients from the mushroom wood to nourish the growth of the young substrate. Cultivation practice shows that the mushroom wood in the water stimulation after the 5th d, the seed body can break through the bark, and the formation of the cap, the 12th d seed body open the umbrella to reveal the gills, the 15th d cap spread. [3]
The speed and quantity of mycelium spreading directly affects the decomposition of mushroom wood and the formation of nutritive mycelium. Nutritional mycelium is the basis for the formation of the substrate base, the degree of decay of the mushroom wood and the amount of mycelium, related to whether the substrate base can grow into a substrate, as well as the quantity and quality of the substrate produced. All these constitute the intrinsic factors for the occurrence of high-quality linden shiitake mushrooms. Conditions such as natural temperature of 5～15℃, no precipitation process within 15～20d, relative humidity of 50%～80%, and sunshine during the growing period of the substrate are the external factors for the production of linden quality shiitake mushrooms. When the young mushrooms in the growth period of the fruiting body are under the conditions of low temperature, slow growth, natural thickening of the mushroom flesh and sunlight irradiation, the white lines of cracks in the cap of the mushroom which are interwoven longitudinally and horizontally in the form of a net will be formed and the cracks will be further deepened with the prolongation of the growth period, so that the whole mushroom body will be a white "mushroom flower". When the flower mushroom encounters rainfall or increased air humidity during the period of occurrence, the white lines that have been formed will soon turn brown and become chaga mushrooms or thick mushrooms; if thick mushrooms can not be harvested in time, the lines will basically disappear, the cap will spread out, and the edge of the mushroom will become thin, becoming thin mushrooms or plate mushrooms, and the quality will be greatly reduced.
3 linden shiitake high quality product production path
Hubei is one of the linden shiitake planting areas in China, the annual linden shiitake inoculation in 1.6 to 1.8 million sheds (50 linden per shed, each linden diameter of 10 to 15cm, length of 1m), with an annual output of dry shiitake mushrooms of about 2,700t. Examined in general, shiitake mushrooms produced in Hubei are mostly dried naturally, with poor air-drying technology, high water content in the product, many wrinkles on the surface, and sloppy grading, long shanks, blackened color, and serious damage to the mushroom body. According to the 3650kg mushrooms purchased in Baokang County, only 8% of the products were in line with high quality mushrooms. According to the author in Xingshan, Danjiangkou and other places, to revitalize the Hubei mushroom industry, in addition to comprehensively promote the existing mature technology of mushroom production, should pay special attention to the following key technical points.
3.1 Selection of good mushroom wood
Hubei Province, there are 1,185,000hm2 of mushroom resources, suitable for the cultivation of shiitake mushroom species are mainly hemp oak (Quercus acutissima) gown oak (Q.gladulifera), cork oak (Q.variabilis), oak (Q.hirsutula), chinkapin (Castanopsis cuspiclata), oak (Q.hirsutula), and the Chinese chinkapin (Q.cuspiclata). Castanopsis cuspiclata), maple (Liquidambar formosana), and so on. Should choose solid wood, nutrient-rich, thicker bark, not easy to fall off, more sapwood, less heartwood, high lignin content, resistance to decay, non-toxic sap, no odor cork oak, Quercus robur, maple trees, such as 15 to 25 years old, 12-20cm in diameter trees for cultivation materials. This can do 1 year inoculation, 3 to 5 years harvesting mushrooms, is conducive to the protection of mushroom wood resources from annual logging, to promote the development of sustainable agriculture.
3.2 Adopting medium and low temperature type strains
There are more than 30 main strains of linden shiitake mushroom in our province since 80's. The medium and high temperature type linden shiitake mushroom strain is represented by "7925", the medium temperature type is represented by HUNAO No.1, and the low temperature type of late maturing species is represented by "8404". The medium temperature type is represented by Huanong No. 1, and the low temperature type with late maturity is represented by "8404". The general production of dry mushrooms should be based on the use of medium and low temperature type strains, so that the product quality is high and the economic value is large.
3.3 Build artificial mushroom shed, avoiding rain to produce mushrooms
Rain and air humidity have an important effect on the formation of high-quality shiitake mushrooms, and avoiding rain to produce mushrooms is an important prerequisite for the high-quality and high-yield of linden shiitake mushrooms. Yao Shuxian et al. (1995) suggested that the mature mushroom wood should be concentrated in the site which is favorable for mushroom management, and the artificial plastic mushroom shed can also be set up to prevent rainwater from washing away. The author in 1995 in danjiangkou city survey, in the spring rainy years, the city due to continuous rain caused linden mushroom mold up to 20 ~ 25 million kg, such as can change the current mountain linden open ground mushroom for artificial mushroom sheds to avoid the rain out of the mushroom, one can realize the uniformity and order of mushrooms, and the second can reduce the "rainwater mushrooms", reduce the difficulty of baking. The construction of standard artificial mushroom sheds optimizes the environment for mushroom production, so that the cultivation of linden mushroom can be changed from the traditional "one-field system" to the "two-field system", or even to realize "mushroom production in different places". The environment and management level of mushroom production fully meet the requirements of producing high-quality shiitake mushrooms.
3.4 Reasonable and dense planting, quantitative mushroom production
Correct and reasonable inoculation is a necessary condition to realize the reproduction of shiitake mushroom mycelium into linden wood, and the inoculation method and inoculation density can be determined by the production habits of different places. Hubei Shiitake production areas are mostly used belt punch artificial holes to access the wood chips strains. A 1m long, 12cm diameter linden, take the longitudinal perforation 4 rows, 8 ~ 9 holes per row, each linden to inoculate 32 ~ 36 holes is appropriate. On the hard material, linden thicker (diameter 18cm or more) appropriate increase inoculation density, can effectively accelerate the spread of mycelium in the linden, and can enhance the ability of resistance to miscellaneous bacteria.
Basswood cultivation of shiitake mushrooms, in 3 to 4 cultivation years, each basswood can be harvested about 200 shiitake mushrooms, fresh mushrooms weighing 3000g [4]. If each linden wood can control the total quantity of mushrooms by thinning the buds and other ways to about 30, then the average weight of each fresh shiitake mushroom is 100g, and by controlling the mushroom environment, creating a microclimate of high-quality mushrooms, and drying each fresh mushroom according to the 5-7:1 system, then it can be baked into a dry product of 14.3-20g, and each linden wood can produce high-quality shiitake mushrooms of 429-600g, and according to the price of the place of origin of each 500g of dry products of 40-70 yuan, can create an output value of 40.16-72.7 yuan, and can create an output value of 40.16-72.5 yuan. According to the price of 40～70 yuan per 500g of dried products, it can create 40.16～72.03 yuan of output value.
3.5 Implementation of scientific baking
In the mushroom producing areas in Hubei, the drying technology of shiitake mushroom combined with baking is popularized. Firstly, it can avoid the adverse effects of autumn rain or spring rainy season on the production of mushrooms and reduce the losses caused by rain; secondly, the mushrooms occurring in the spring and autumn seasons are generally of better quality, and the mushrooms are harvested at the right time and then sunbathed in the sunlight for 4-6h, and then baked in the room, and the mushrooms processed by this method are of good color and lustre, with rounded shape, strong fragrance and high value.
In short, mushroom production is the "specialty agriculture", "fine agriculture", "efficient agriculture" in our country's agricultural industrialization, One of the leading industries of "foreign exchange earning agriculture". According to authoritative sources: the relevant state departments to be along the Dabie mountain area, Tongbai mountain area, the Fuyao mountain area to the Qinba mountain area line construction of the largest mushroom gold production line, which undoubtedly gives the development of linden mushrooms in Hubei Province has brought a new opportunity to greatly promote the development of high-quality mushroom industrialization in Hubei
.