Cultivation Techniques of Edible Mushrooms:

Transcription

1 Cultivation Techniques of Edible Mushrooms: Agaricus bisporus, Pleurotus spp., Lentinula edodes and Volvariella volvocea PHP THE MAGIC OF MUSHROOM AND MOULD BIOLOGY Written By: MD. SAIFUL ISLAM Registration Number: Period 1; October, 2013

2 Table of contents Abstracts iii 1. Introduction 4 2. Nutritional and medicinal value 5 3. History of cultivation Agaricus bisporus (White button mushroom) Pleurotus spp. (Oyster mushroom) Lentinula edodes (Shiitake mushroom) Volvariella volvacea (Paddy straw mushroom) The mushroom cultivation process Agaricus bisporus (White button mushroom) Composting Spawning Casing soil Cropping and harvesting Pleurotus spp. (Oyster mushroom) Cultivation on synthetic log Lentinula edodes (Shiitake mushroom) Cultivation on natural log Cultivation on synthetic log Volvariella volvacea (Paddy straw mushroom) Cultivation Preservation Storage in fresh condition Controlled atmosphere Freeze drying Steeping Dehydration Canning Conclusions 28 References 29 Page 2

3 ABSTRACT Cultivation of edible mushrooms in the world started during 18 th century in France and white button mushroom (Agaricus bisporus) is the first cultivated species. However, Shiitake mushroom (Lentinula edodes) was started in 14 th century in China for its medicinal value. Nowadays, oyster mushroom (Pleurotus spp.) are popular because of its taste, flavor and easy to cultivate along with grow on lignocellulosic agricultural or industrial byproducts. As an ideal mushroom for cultivation button mushrooms are cultivated on substrate which has relatively low C:N ratio compared to others. Therefore, it can t be cultivated on natural wood logs. Commercial cultivation techniques of these edible mushrooms on synthetic substrates can be divided into multiple stages, firstly composting so that, most complex compounds are broken down. Subsequently, spawn production; mushroom seed is mixed with this compost and sealed off with a casing layer. Mushroom mycelia will grow and ultimately form fruiting bodies. In conclusion, edible mushrooms are a rich source of important nutrients such as, essential amino acid, vitamins and has nutriceutical value makes them valuable among consumers for their nourishment and rightly called as vegetarian meat. Page 3

4 1. Introduction The word mushroom may have different meanings and perspectives in different literatures and geographical territories. The term mushroom is not a taxonomic division. Mushrooms are macro fungi with distinctive fruiting body, which can be hypogeous or epigeous, large enough to be seen with the naked eye and to be picked by hand (Chang and Miles, 1992). Mushroom is the fleshy, spore-bearing fruiting body of a fungus, typically produced above ground on soil or on its food source. Mushrooms, a group known as fungi, lack chlorophyll and cannot therefore make its own food. It grows on dead organic matter either parasitically or symbiotically with other living organisms. Currently, 14,000 mushroom species have been identified, which would account for 10% of the estimated mushroom species of these, over 3,000 species from more than 30 genera are regarded as prime edible mushrooms, but of these only about 100 species are grown experimentally, 60 cultivated economically, around 30 cultivated commercially, and only 15 are produced on an industrial scale (Oei, 2003; Chang and Miles, 2004). Among the various mushroom species, button mushroom (Agaricus bisporus), oyster mushroom (Pleurotus species.), shiitake mushroom (Lentinula edodes) and paddy straw (Volvariella species) are most popular among the commercial growers. Mushroom which is a fleshy saprophyte fungus are found growing on damp rotten log of wood trunk of trees, decaying organic matter and in damp soil rich in organic substances. Mushrooms have been a component of our human diet since time immemorial. They were used as food before man understood the use of other organisms. Certainly mushrooms were one of man s most basic foods, and they were often considered an exotic and luxurious food reserved for the rich. Records of health promoting properties such as antioxidant, antimicrobial, anticancer, cholesterol lowering and immuno stimulatory effects have been reported for some species of mushrooms (Mau et al., 2004). Today mushrooms are food for both the rich and the poor. They can be grown anywhere as long as the conditions for their growth and cultivations are provided. Page 4

5 Figure 1. General morphology of Agaricus spp. fruiting body 2. Nutritional and medicinal value Edible mushroom are highly nutritious and can be compared with eggs, milk and meat called the food of the gods and still treated as a garnish or delicacy can be taken regularly as part of the human diet or be treated as healthy food or as functional food. Mushrooms are rich in proteins, vitamins, and minerals and called as the vegetarian s meat. Mushroom proteins are considered to be intermediate between that of animals and vegetables as it contains all the nine essential amino acids which are required for human body. Mushroom has a high protein content of 25 50%, fat (2 5%), sugars (17 47%), mycocellulose (7 38%), minerals (8 12%) and vitamins such as B 1, B 5, B 6, C and D, niacin and riboflavin. Apart from serving as a protein food, for which they are most popular in the world. Many of mushrooms produce a range of metabolites of intense interest to the nutriceutical and pharmaceutical (e.g. anti-tumor, immuno-modulation agents and hypocholesterol-aemic agents) and food (e.g. flavor compound) industries (Chang, 2007). Page 5

6 Mushrooms are devoid of starch, cholesterol and low in calories and other carbohydrates and very low in sodium, yet they provide important nutrients, including selenium, potassium, riboflavin, niacin, vitamin B & D and more. Apart from their nutritional value, mushrooms have potential medicinal benefits. Mushrooms are among the richest sources of selenium in the produce aisle and provide 8-22 µg per serving that works as an antioxidant to protect body cells from damage that might lead to heart disease, some cancers and other diseases of aging. It also has been found to be important for the immune system and fertility in men. This is good news for vegetarians, whose sources of selenium are limited. On the other hand, potassium is an important mineral many people don t get enough of it aids in the maintenance of normal fluid and mineral balance, which helps control blood pressure. It also plays a role in making sure nerves and muscles, including the heart, function properly. Mushrooms have milligram of potassium per 84 gm serving, which is 3-11% of the daily Value. They are an ideal food for diabetics and over-weight people. Preliminary research suggests increasing intake of low-energy-density foods (meaning few calories given the volume of food), specifically mushrooms, in place of high-energy-density foods, like lean ground beef, can be an effective method for reducing daily energy and fat intake while still feeling full after the meal for weight management/satiety. Many Asian countries use traditionally wild edible mushrooms as delicious and nutritional foods and medicine. Wild edible mushrooms are appreciated not only for texture and flavor but also for their chemical and nutritional characteristics. Page 6

7 3. History of cultivation 3.1 Agaricus bisporus (White button mushroom) Button mushrooms (Agaricus spp.) are most widely cultivated and consumed mushroom in the world. The mushroom grows naturally in grasslands and field in North America and Europe. Agaricus bisporus was first species cultivated, on compost in Western culture, in Paris, France, around By 1914, cultivation of button mushroom was becoming industrialized. Though, growing method is well known, but poorly understood. Substrate includes mostly horse manure, wheat straw, corn cobs, and several other waste plant products and animal waste. A brief detail of Agaricus bisporus is presented in (Table 1) (Figure 2). Table 1. A brief detail of Agaricus bisporus Taxonomic classification Mycological characteristics Kingdom: Phylum: Class: Order: Family: Genus: Species: Fungi Basidiomycota Agaricomycetes Agaricales Agaricaceae Agaricus A. bisporus gills on hymenium cap is convex hymenium is free stipe has a ring spore print is brown ecology is saprotrophic Page 7

8 Figure 2. Agaricus bisporus fruiting body on casing soil 3.2 Pleurotus spp. (Oyster mushroom) The cultivation of oyster mushroom (Pleurotus spp.) in history is unknown. The species epithet refers to the oyster shell like appearance and color of the fruiting bodies. There are about 40 species of Pleurotus mushrooms and they ranks second among the important cultivated mushrooms in the world for their excellent taste and flavor. Genus Pleurotus belongs to family Tricholomataceae is an efficient lignin-degrading mushroom and can grow well on different types of lignocellulolosic materials. An important reason for the increased popularity is that the fungus can degrade all three key categories of polysaccharides of forest and agricultural crop residues: lignin, cellulose and hemicelluloses (Chang and Miles, 2004). Cultivation of this Mushroom is very simple and low cost which gives consistent growth with high biological efficiency. Different species of Pleurotus can grow well in variable temperature conditions; hence they are ideally suited for cultivation throughout the year. Among the Pleurotus species, P. ostreatus is most popular for the cultivation. A brief detail of Pleurotus spp. is presented in (Table 2) (Figure 3). Page 8

9 Table 2. A brief detail of Pleurotus spp. Taxonomic classification Mycological characteristics Kingdom: Phylum: Class: Order: Family: Genus: Fungi Basidiomycota Agaricomycetes Agaricales Pleurotaceae Pleurotus gills on hymenium cap is offset hymenium is de-current stipe is bare spore print is white ecology is saprotrophic Figure 3. Pleurotus spp. fruiting body on natural log 3.3 Lentinula edodes (Shitake mushroom) The Japanese wood mushroom or shiitake (Lentinula edodes ) is the third most widely cultivated edible mushroom worldwide, surpassed only by Agaricus spp. and Pleurotus spp. (Chang and Miles, 1991) are known as the fragrant mushroom, is grown usually on logs of oak outdoors in forests. Shiitake are native to Japan, China and Korea and have been grown in all three countries since prehistoric times (Kazuko, 2006). They have been cultivated for over 1,000 years. The Japanese cultivated the mushroom by cutting shii trees with axes and placing the logs by trees that were already growing shiitake or contained shiitake spores. Before 1982, the Japanese variety of these mushrooms could only be grown in traditional Page 9

10 locations using ancient methods. In 1982, Gary F. Leatham published an academic paper based on his research on the budding and growth of the Japan Islands variety; the work helped make commercial cultivation possible in the United States (Leatham, 1982). Environmental manipulation of the crop is achieved by heavy watering, shading or positioning the logs in areas of different microclimate. A more intensive cultivation technique has recently been developed involving growth on synthetic logs made by compressing agricultural wastes, mainly sawdust, into plastic bags. Lentinula edodes is largely produced in Japan, China and South Korea, but commercial cultivation is spreading to other parts of the world. Lentinula edodes accounts for 15% of world production of cultivated mushrooms; the world-wide crop of L. edodes in 2002 has been estimated at 1.8 million tons (Chang, 2008). A brief detail of Lentinula edodes is presented in (Table 3) (Figure 4). Table 3. A brief detail of Lentinula edodes Taxonomic classification Mycological characteristics Kingdom: Phylum: Class: Order: Family: Genus: Species: Fungi Basidiomycota Agaricomycetes Agaricales Marasmiaceae Lentinula L. edodes gills on hymenium cap is convex hymenium is free stipe is bare spore print is white to buff ecology is saprotrophic Page 10

11 Figure 4. Lentinula edodes fruiting body on natural log 3.4 Volvariella volvacea (Paddy straw mushroom) Volvariella volvacea known as paddy straw mushroom or straw mushroom is a species of edible mushroom cultivated throughout East and Southeast Asia and used extensively in Asian cuisines. The "Paddy straw mushroom" Volvariella mushrooms account for 16% of total production of cultivated mushrooms in the world. They are popular for their pleasant tastes, higher protein content and shorter cropping duration compared to other cultivated mushrooms (Rajapakse, 2011). The mushrooms are grown on rice straw beds and picked immature, during the button or egg phase and before the veil ruptures. No record has been found of their cultivation before the 19th century (Hsiung, 2006). A brief detail of Volvariella volvacea is presented in (Table 4) (Figure 5). Page 11

12 Table 4. A brief detail of Volvariella volvacea Taxonomic classification Mycological characteristics Kingdom: Phylum: Class: Order: Family: Genus: Species: Fungi Basidiomycota Agaricomycetes Agaricales Pluteaceae Volvariella V. volvacea gills on hymenium cap is conical or umbonate hymenium is free stipe has a volva spore print is is salmon ecology is saprotrophic Figure 5. Volvariella volvacea fruiting body on straw bed Page 12

13 4. The mushroom cultivation process Mushrooms have a two-phase life cycle, the mycelium (vegetative or colonization phase) and the fruiting body (reproductive phase that bears the spores) (Chang and Buswell, 2008). The mycelium grows through the substrate, biodegrades its components and supports the formation of fruiting bodies. Mushroom growers call the switch from mycelial extension to the production of mushroom primordia pinning, the successive development of primordia into mushrooms fruiting. While growth of mycelium lasts for several days, weeks or months, production of fruiting bodies is short lived, and the phenomenon is called fructification (Royse, 2004). However, both vegetative and reproductive phases are very much influenced by the physiological condition and nutritional state of the mycelium. Hence, mushroom production depends on its own biology, environment and nutrient (compost) (Chang and Buswell, 2008) in (Figure 6). Figure 6. Mushroom Science: mushroom cultivation and production (Chang and Buswell, 2008) Page 13

14 Consistent production of successful mushroom crops will be built upon scientific knowledge and practical experience (Chang and Miles, 1989). Mushroom cultivation is a worldwide practice in terms of percentage approx. 80% of total world production of these four species, viz: Agaricus bisporus (31.8%); Lentinus edodes (25.4%), Pleurotus spp. (14.2%) and Volvariella volvaceae (7.9%) productions (Stamets, 2000; Royse 2004). In this chapter, cultivation process of each edible mushroom species is discussed separately. In each paragraph, an overview of the main commercial cultivation processes for the production of edible mushrooms is described. Overview of general techniques of cultivation of mushrooms is given below in a diagram regenerated from Stamets and Chilton, 1983 (Figure 7). Figure 7. Diagram illustrating overview of general techniques of cultivation of mushrooms regenerated from Stamets and Chilton, 1983 Page 14

15 4.1 Agaricus bisporus (White button mushroom) Button mushroom (Agaricus bisporus) is the most popular and economically sown to grow and is extensively cultivated throughout the world (Maheshwari, 2013). It can be grown anywhere if the essential conditions are obtained or controlled. These conditions included temperature, moisture, ventilation and good spawn. The temperature requirement for the spread of the mycelium or the vegetative growth is 22 to 25 0 C. For the reproductive stage the temperature requirement is 14 to 18 0 C. Within the limits prescribed, the temperature should be uniform throughout the growth of the crop. If it is too cold the development of the spawn will be retarded. A high temperature will favor the development of moulds and bacteria, which will soon destroy the spawn or crop (Maheshwari, 2013). Moisture is an important factor in the cultivation of the mushroom and needs careful application. The mushroom requires an atmosphere nearly saturated with moisture, get the direct application of water on the beds is more or less harmful to the growing crop. Good aeration is essential for a healthy crop, because ventilation is one of the important factors governing the mushroom production. Good ventilation is responsible for the maintenance of congenial environmental conditions and also for the removal of toxic gas by the introduction of adequate fresh air (Maheshwari, 2013). Good spawn is also very much essential. Spawn is merely the mycelium from a deleted mushroom grown in some convenient medium and it is the strain of mushroom selected which decides the types of mushroom the spawn will produce Composting Compost is the substrate on which mushroom grows. The biochemical activities of a number of micro-organisms make the substrate selective for the growth of mushroom, Agaricus spp. (Button mushroom) (Anonymous, 2006). The process of compost making is known as composting. Composting is defined as indefinite microbial degradation of organic wastes. The process of composting involves microbial decomposition of the organic materials, synthesis of microbial proteins and conditioning of the fibrous material to absorb and retain moisture. Compost is prepared by mixing wheat straw or paddy straw with a number of organic or inorganic fertilizers in fixed proportions. Horse manure and chicken manure can also be used besides wheat straw and paddy straw. Page 15

16 Good compost should be brown with a distinct but inoffensive smell. Natural drop in temperature and lack of free ammonia or no smell of ammonia are signs that the composting process has been completed (Moore and Chiu, 2001). When squeezed in the hand no water should trickle down, yet it should be moist. When rubbed between the fingers there should be no feel of greasiness. The entire compost will be placed in controlled environment. By raising the temperature of this environment to 54.4 C by peak heating for one week in order to kill all insect pests and fungal parasites is called pasteurization which may not be possible under normal environmental conditions. This is the second phase of composting Spawning After composting, the spawn will be introduced into the compost and the process is called spawning. Spawn is the mushroom seed, comparable to the vegetative seed in crop plants. It is merely the vegetative mycelium from a selected mushroom grown in a convenient medium and the particular strain of mushroom the spawn would produce. The success of mushroom cultivation and its yield depend to a large extent on the purity and quality of the spawn used. The amount of spawn should be sufficient to help rapid and vigorous coverage of the beds with the organism (Maheshwari, 2013). It must be sufficient to fight successfully against any other organism that are always present in manure and to overcome any slightly adverse conditions of moisture or consistency that are present. When conditions are ideal in the beds, less spawn is needed Casing soil Casing means covering the compost with a thin layer of soil or soil-like material after the spawn has spread in the compost. The development of fruit bodies of A. bisporus requires a non-nutritional layer of casing soil on top of the nutritious compost. Important are its relatively high water activity and its microbial Flora. The stimulatory effect of casing soil microbes on fruit body formation can be largely replaced, under axenic conditions, by activated charcoal (Noble et al., 2003) or by the removal of volatile organic compounds (Noble et al., 2009). A third factor for fruit body formation in commercial practice is the ample supply of fresh air with a lower temperature and lower CO 2 and moisture contents than the air used at rapid mycelial colonization; this process step to induce fruit body Page 16

17 formation is called airing or vent-off (Eastwood et al., 2013). Casing is also done due to give support to the mushroom. A good and ideal casing material should have good water holding capacity, otherwise the water will go straight to the compost and the surface of the compost will become water logged and will cause damage to the spawn. It should absorb water quickly and should release it slowly. It should have good aeration capacity, that is, it should be quite porous so that exchange of gases can take place easily. The texture of the casing material should be such that it should not be altered by watering. It should be free from disease organisms, insects and undecomposed vegetable matter. Soil has been recognized as the universal casing material. Soil contains many microorganisms. To use it as a casing material it should be sterilized in such a way that harmful micro-organisms are killed and the useful ones remain. Sterilization of casing materials is done either by chemicals or by heating. Sterilization under pressure is not advisable as the beneficial micro-organisms are also killed and leave the soil more susceptible to reinfection. Figure 8. Agaricus bisporus fruiting bodies with compost material and casing soil Cropping and harvesting Excessive humidity during the cropping will result in heavy concentration of carbon-dioxide. The more the volume of mushrooms grown in a room the more will be the need of fresh air. The greater the humidity and higher the temperature and it is therefore, essential to Page 17

18 keep the temperature low. Mushrooms mostly appear in "flushes" and at temperature of 68 o F; it generally takes 7 to 8 days to come to the button stage from the first appearance of the formation of a pin head (Maheshwari, 2013). The humidity of the mushroom house will determine whether there is any need of watering the bed. If the atmosphere is dry then frequent watering is essential. While watering, gentle spraying is essential, otherwise the casing soil will get disturbed. The duration of cropping varies with the circumstances. 4.2 Pleurotus spp. (Oyster Mushroom) The oyster mushroom (Pleurotus species) grows under natural conditions on trees or dead woody branches of trees. It needs moderate temperatures of C for its growth (Zang and Fadel, 2000). This mushroom is also known as "wood fungus". Following species of genus Pleurotus have been cultivated so far are Pleurotus ostreatus, Pleurotus flabettatus, Pleurotus sajor-caju, Plellrotus cryrgil, Pleurotus sapidus, Pleurotus cornucopiae etc Cultivation on synthetic log There are several methods of cultivation of Pleurotus species with only little difference or modification. Dried paddy straw was chopped into 1 to 2 cm long bits and soaked in water over-night. Excess water is drained off and horse gram powder and spawn were added and mixed with the wet straw. Polyethylene bags with holes were then filled with the foregoing mix (substrate) and kept in a room at 21 to 31 o C with sufficient light and ventilation. The mycelium took 11 to 14 days to permeate the substrate in the bags (Stamets, 2000). During the period the temperature of the substrate varied between 32 and 36 o C and later became almost constant at 25 to 28 o C with the appearance of mushroom pins on the upper side. The polythene bags were cut open on the sides without disturbing the bed, which had become quite compact by them. Water should be sprayed over it twice in a day. The bags were placed in a well-ventilated room with normal conditions of temperatures, relative humidity and light. In 3 to 4 days, the crop started coming up. The temperature range is 20 to 32 0 C with relative humidity 35 to 75%. The mushrooms are harvested from the 4th day onwards (Hall, 2010). The synthetic log cultivation procedure of oyster mushrooms is presented below in a flow diagram (Figure 10). Natural log cultivation procedure of oyster and shiitake mushrooms is similar and the procedure is discussed in shiitake mushroom cultivation part. Page 18

19 Figure 9. Pleurotus species fruiting bodies on natural and synthetic logs Substrate preparation (All kinds of straw and other agro-wastes) Chopped in small (1-2cm pieces), soaked in water for 2-3 hours Substrate can be pasteurized by hot water (80 C) for 2hours (no prior soaking required in this case), suitable for small scale production or steam pasteurization at 80 C for 2 hours (in autoclave or special steam chambers), suitable for semi-commercial production or sterilized in an autoclave (after filling in PP bags, plugged with cotton) at 121 C, 15 lb pressure for 15 minutes (best method for commercial production) Fill one Kg pasteurized substrate (65% moisture) in Polypropylene bags, plug with nonabsorbent cotton Spawning 5% of wet substrate) while filling in bags in pasteurization method or top spawning in sterilized method Spawn running in dark room (24-28 C, days variety dependent) Shift to cropping room and make large holes Pinhead initiation (2-7 days after opening, C, variety dependent, humidity 80-85%, light, ventilation) Harvesting (2-4 days after pinhead initiation, variety dependent) Figure 10. Cultivation procedure of oyster mushrooms Page 19

20 4.3 Lentinula edodes (Shiitake mushroom) Cultivation on natural log Lentinula edodes is one of the most popular edible mushrooms in the world because of its flavor, taste, nutritional and medicinal properties (Smith et al., 2002). This fungus can grow on synthetic logs as well as natural logs. The most traditional but laborious cultivation is carried out in wood logs, mainly oak. Once logs are cut to the desired length, they are ready for inoculation or spawning. Spawn is supplied in the form of wooden plugs or sawdust. Growers drill holes in the logs with high-speed drills, the holes corresponding to the diameter and length of the wood-plug spawn. One row of holes is drilled for each 2.5 centimeters of log diameter, and the holes are evenly spaced lengthwise every 15 centimeters along the row. Because shiitake mycelium grows much faster along the grain than across it, holes are commonly spaced in a diamond pattern to facilitate growth. After inoculation the logs are stored several months for mycelium colonization and finally for the formation of fruit bodies. Spawn run, or vegetative mycelial growth, may last from 6 to 18 months, depending on the tree species, log size, spawn cultivar, moisture content, temperature of the environment, and other variables. After the spawn run period, logs are transferred to a raising yard. Raising yards usually are cooler and moister than the spawn run areas. The change of conditions provides an optimum environment for the growth and development of shiitake. Also, in a form of shock treatment intended to stimulate primordial formation, logs may be banged with a hammer or dropped on end. No one is certain precisely why this stimulation benefits shiitake growth, but the shock treatment increases yields and facilitates more consistent fruiting on each log. In the raising yard, the logs are arranged to provide for convenient harvesting of the mushrooms. Most production occurs in the spring and fall when conditions are most favorable. This method is still used because of its high quality mushroom product (Royse, 2001), although leads to a severe threat to natural forests (Chiu et al., 2000) Cultivation on synthetic log The last decades, new methods for L. edodes cultivation on residue-based substrates have been developed using milled wood residues (sawdust) supplemented with nitrogen sources (e.g. rice bran). Sawdust is the most popular basal ingredient used in synthetic formulations Page 20

21 of substrate used to produce shiitake mushroom. Regardless of the main ingredient used, starch-based supplements such as wheat bran, rice bran, millet, rye, and maize are always added to the mix. Some formulations used consist of 80% sawdust and 20% bran; 80% sawdust, 10% bran and 10% wheat or millet; and 84% sawdust, 5% rice bran, 5% wheat bran, 3% soybean and 3% lime (Kalberer, 1987). These supplements serve as nutrients to provide an optimum growth medium. Other supplements, added in lesser quantities, include calcium carbonate (CaCO 3 ), gypsum, and table sugar. These produce a better, more nutritious diet for the shiitake. Other agricultural wastes that can be used as substrates (alone or in combination with other supplements) in L. edodes cultivation are cereal straw, corn cobs, sugarcane bagasse, tea waste, sunflower seed hulls, peanut shells, vineyard pruning s, cotton straw and seed hulls etc. (Philippoussis et al., 2003; Rossi et al., 2003, Gait an- Hern andez and Mata, 2004; Fan and Soccol, 2005; Royse and Sanchez, 2007). The principle of the cultivation method comprises mixing and compacting ingredients into plastic bags, followed by sterilization, inoculation with fungal mycelia, incubation in dark rooms with controlled temperature and humidity for 30 to 80 days and finally fruiting induced by temperature reduction. Substrate s ingredients are mixed, watered to gain moisture content around 60% and filled into polypropylene bags. The bags are made of heatresistant polypropylene and contain a special breather patch made of microporus plastic. The micropores in the patch allow the substrate to exhale carbon dioxide while not inhaling any bacteriological or fungal agents that could act as contaminants. The filled bags are stacked on racks, loaded into an industrialized autoclave, sterilized for 2 hours at 121 C, cooled in a clean room, and then inoculated with spawn. After 20 to 25 days spawn run, the bags are removed and the substrate blocks are exposed to an environment conducive for browning of the exterior log surfaces. As the browning process reaches completion (4 weeks), primordia begin to form about 2mm under the surface of the bag-log indicating that it is ready to produce mushrooms (Royse, 2004). Finally, yields and mushroom quality tend to be higher when logs are browned outside the bag. Once the synthetic logs are ready to fruit, primordia maturation is stimulated by soaking in cool water (12 C) for 3 to 4 hours. For logs that are browned inside the bag, soaking is not required because sufficient water is available to support the first flush of mushrooms. However, soaking of logs is required for Page 21

22 the second and subsequent flushes. Soaking allows water to rapidly displace CO 2 contained in air spaces and provides enough moisture for one flush of mushrooms. After soaking, the logs are placed on shelves and the mushrooms begin to enlarge. Approximately 7 to 11 days after soaking, mushrooms are ready for harvesting. During harvesting, the shiitake are twisted from the substrate surface by hand and any residual substrate on the mushrooms is removed with a knife or scissors. After all mushrooms have been harvested from the substrate, the logs are soaked in water again. The second soaking may require up to 12 hours, and the third soaking may require up to 18 hours replacing the water lost through mushroom tissue production and water evaporation. The average time from the peak harvest of one flush to the peak of the next flush is about 16 to 20 days. The main advantages of using synthetic medium over natural logs are time and efficiency (Royse, 2004). The production cycle for synthetic-medium cultivation lasts approximately 3 to 4 months from inoculation to cleanup. Biological efficiency for this method averages from 75 to 125 percent. In contrast with these excellent results, the natural-log cultivation cycle usually takes about 6 years with a maximum efficiency of around 33 percent. The total time required for production on synthetic substrate is about 6 percent of the natural system cycle time with about three times the yield efficiency (Salmones et al., 2005). Figure 11. Lentinula edodes fruiting bodies on synthetic logs Page 22

23 4.4 Volvariella volvacea (Paddy straw mushroom) Paddy straw mushroom is also known as warm mushroom as it grows at relatively high temperature between 30 and 45 C (Chang and Miles, 2004). It is a fast growing mushroom and under favorable growing conditions total crop cycle is completed within 4-5 weeks time. This mushroom can use wide range of cellulosic materials and the C: N ratio needed is 40 to 60, quite high in comparison to other cultivated mushrooms. It can be grown quite quickly and easily on uncomposted substrates such as paddy straw and cotton waste or other cellulosic organic waste materials (Ahlawat & Kumar, 2005). Moreover, cellulose/lignin ratios of wheat straw and cotton waste substrates were positively correlated to mycelial growth rates and mushroom yields of V. volvacea (Philippoussis et al., 2001a). It has been considered as one of the easiest mushrooms to cultivate. Among three species of genus Volvariella namely V. diplasia, v. volvacea and V. esculenta; Volvariella volvacea is the most commonly grown Cultivation Paddy straw which is to be used should be un-crumpled, not very leafy, with not more than one year old and preferably should be hand threshed (Ahlawat & Kumar, 2005). It should be stored at a proper place so that it does not get wet during rain. Paddy straw is made into bundles. The bundles are soaked in water for 18 to 24 hours. Soaking can be done in small tanks and the bundles should be completely immersed in water. The bundles are taken out and excess water drained off. The bundles are arranged such that they make one layer on which small bits of spawn are placed 3 to 4 inches inside the margin, leaving a space of 5 to 5.5 cm from each other. A small quantity of arhar or gram seed powder is sprinkled over the spawn bits. Each layer is spawned in the same way. Finally the last layer is spawned all over and covered with a thin layer of loose straw and the bed is pressed down. The bed is covered with a polythene sheet. Watering depends upon the humidity of the air. Mostly no watering is required for the first 3 or 4 days. Watering of the beds and temperature within the beds are very important factors for the yield of paddy straw mush- room. The bed temperature should remain between 30 and 35 0 C after spawning. The temperature should not go below 30 C during the growing period (Verma and Vijay, 2002). Small buttons start appearing 7 to 10 days after spawning. At that time the polythene sheet should Page 23

24 be removed from the bed. They remain in the button stage for 4 to 5 days and then grow into full size. Picking is done by gently twisting the fruiting bodies. Spawning the different layers of the bed is an influencing factor in straw mushroom production (Kaul and Dhar, 2007). Spacing between the spawn bits also influences the yield. Smaller spacing (5 cm) between small spawn bits (10 mm) and larger spacing (10 cm) between large spawn bits (100 mm) gives better yield. Volvariella species can also be grown in winter. The only care taken is to maintain the temperature of the bed. As the atmospheric temperature is low, the bed temperature will also be low. Hence, bed temperature is increased by incorporating the leaf materials which can be used fresh or partially dried (Verma, 2002). The bed is compacted and covered with transparent polythene sheet. Figure 12. Volvariella volvacea fruiting bodies Page 24

25 Figure 13. Outdoor method of straw mushroom cultivation Figure 14. Indoor method of straw mushroom cultivation Page 25

26 5. Preservation Mushrooms, like fruits and vegetables are highly perishable such as, Paddy straw mushroom has very little shelf life (Burnas et al., 2006). The demand for mushrooms never coincides with the supply, the day when there is good production the demand may be low and viceversa. To prevent such an overabundance in the fresh market it is necessary to preserve them. Mushrooms require a great deal of attention during storage, marketing and processing at the post harvest stage. Discoloration, weight and flavor loss are some of the problems. Mushrooms stored at 21 o C remained whiter than those stored at 1 0 C or 11 0 C, but they mature at a much faster rate (Burnas et al., 2006). The loss of whiteness during storage is a complex process. It was found that the mushrooms stored at 21 0 C hardened at a faster rate than mushrooms stored at 11 0 C or 1 0 C (Burnas et al., 2006). Chemical action plays a great role in the toughening process. Toughening arid the degree of maturity were greatest at 21 0 centigrade. Different methods are given here to increase the shelf-life of edible mushrooms ( ooms.pdf Preserving Mushrooms, Last accessed October 09, 2013). 5.1 Storage in fresh conditions Mushrooms have a high rate of respiration and hence proper attention should be given during storage. Vacuum cooling also helps in increasing the shelf life. In this case mushrooms are packed in a film which is punctured to allow evaporation from the mushrooms. The punctured hole is covered with a small piece of sticking tape after vacuum cooling, to stop the gas flow and to allow the over-wrap to function properly. 5.2 Controlled atmosphere Shelf-life of fresh mushrooms in increased in a controlled atmosphere consisting of 9 percent oxygen and 25% carbon-ill-oxide. Partial evacuation followed by flushing with carbon monoxide and storage at low temperature, can also extend the storage life up to 20 days. Page 26

27 5.3 Freeze drying Freeze drying is done by immersing the sliced mushroom in a solution of 0.05% sodium meta-bi-sulphate and 2 percent salt for about 30 minutes. These are then blanched in boiling water for 2 minutes, followed by cooling. The product is frozen at F for one minute. The frozen mushrooms are dried to a moisture content of 3 per cent in freeze drier and packed in cans under vacuum. 5.4 Steeping Edible mushrooms have been steeped in a solution of 2.5% salt, 02% citric acid, 0.1 % ascorbic acid, sodium bi-carbonate, potassium meta-bi-sulphate, which can preserve the mushrooms up to ten days without any microbial spoilage. 5.5 Dehydration For dehydration purpose, mushrooms are harvested at a mature stage. These can be dried in the sun or in mechanical dehydrator at C. Fresh mushrooms are reduced to one eighth their original weights after dehydration. Dried mushrooms can absorb water from the atmosphere, so they should be packed either in aluminum foil or in polythene bags. If they are not dried properly they give a foul smell, which however, goes off during cooking. Dried mushrooms can be stored for 6-7 months and better reconstituted by immersing in a solution of sugar and ascorbic acid. 5.6 Canning For canning purpose mushrooms should be picked up at an early stage. Fresh mushrooms are dipped in boiling water for two to three minutes and put in cold water. Blanching is necessary to control discoloration. Blanched and cooled mushrooms are filled in cans. Brine solutions (2% common salt + 2% sugar + 0.3% citric acid) are boiled and filtered and added into the cans. The cans are sterilized with boiling water at 85 C and later they are wiped dry and kept in cool dry place. Page 27

28 6. Conclusions In history, the cultivation of edible mushrooms has been refined and the efficiency as well improved significantly so that, high yield can be achieved nowadays. Each region of the world cultivates their own diversification of edible mushrooms and depends on the popularity among consumer society. In western countries, Button mushrooms (Agaricus species) are especially popular to both growers and consumers but, other edible mushrooms are becoming popular such as, Shiitake (Lentinula species) and Oyster mushrooms (Pleurotus species). Current mushroom industry is based on both applications of techniques for the production of mushroom fruiting bodies and the application of modern biotechnological techniques to produce medicinally beneficial compounds and nutriceutical products. Page 28

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33 Mushroom Growers' Handbook 1: Oyster Mushroom Cultivation, MushWorld ( (Last accessed October 09, 2013) Mushroom Growers' Handbook 2: Shiitake Cultivation, MushWorld ( (Last accessed October 09, 2013) Mush-World (Last accessed October 09, 2013) Preserving Mushrooms, mushrooms.pdf (Last accessed October 09, 2013) (Last accessed October 09, 2013) Page 33