Agricultural and horticultural use of paddy straw, Biomass Management for Fodder & Energy | Biomass Management for Fodder & Energy - Agricultural Engineering PDF Download

12.2. Paddy straw mushroom

The mushroom defined as “a macro fungus with a distinctive fruiting body, large enough to be seen with the naked eye and to be picked up by hand” (Chang and Miles, 1991). In a narrow sense, the world mushroom also refers only to the fruit body. Unlike green plants, mushrooms are heterotrophs. Not having chlorophyll, they cannot generate nutrients by photosynthesis, but take nutrients from outer sources.

12.2.1. History of Paddy straw mushroom

Paddy straw mushroom (Volvariella volvacea) belongs to the family Pluteaceae. Chinese growers developed its cultivation more than 300 years ago. Therefore, it was named “Chinese Mushroom” (Zhanxi and Zhanhua, 2000).  Paddy straw mushroom is a popular variety among people because of its distinct flavor, pleasant tastes, higher protein content and shorter cropping duration compared to other cultivated mushrooms. 2000). Volvariellarequires a high temperature (35 ± 2 ºC) for better and early hyphal growth. Also 32±2 ºC and 80-90 % RH (relative humidity) are needed for the formation of fruiting bodies. Paddy straw Mushroom is quick growing fungus, which can be harvested on 12^th or 13^th day. Paddy straw mushroom was first cultivated in India in 1940 and is more popular in coastal states like Orissa, Andhra Pradesh, Tamil Nadu, Kerala and West Bengal, however, it can also be cultivated in most of the states, where agroclimatic conditions suit and agrowaste is available in plenty.

12.2.2. Cultivation of paddy straw mushroom

A small raised platform is prepared with bricks or wooden planks to drain the excess water that drips from the bed. Both indoor cultivation and the product of thatched sheds yield a good harvest all through the year. Paddy straw is tied in bundles of 500 g and soaked in water for 24 hours. The excess water is drained off. For a good yield of quality buttons, the bundles are preferably sterilized (under 13.5 kg/cm2 steam pressure for 15 minutes) using a autoclave for large scale production or atleast by immersing in boiling water for about an hour. The sterilized straw is shade dried for about 30 minutes on a clean surface in order to cool it as well as to remove excess water. The stacks are kept inside a bamboo or wooden frame of 1 m2 in 4 to 5 layers, each consisting of 6 to 8 bundles. The beds are arranged on a raised platform and the bundles are placed opposite to the first layer.

About 200g of chick pea or pigeon pea powder is added to enrich the bed except on the top layer. The grain spawn is shifted from the container on to a clean surface using a glass rod or stick and is laid over this bed. The beds are covered with perforated plastic bags and incubated at 20-30 ^oC under adequate humid conditions (relative humidity 70 – 85%) preferably in a dark room for about 15 – 20 days.

12.2.3. Spawn

Spawn is the preparation of the seedling material grown on substrates like sorghum seeds. The seeds (200-300g) are cooked under sterile conditions and usually milk bottles are used as containers. The sterilization can be done using a pressure cooker or an autoclave for large scale production. The fungus (inoculum) grown in test tubes can be transferred to the substrate under sterile conditions. One spawn bottle is used for preparing three mushroom beds under aseptic conditions. The spawn can be obtained ready made from the mushroom growers or from the mycology unit of any agricultural university. 

12.2.4. Harvest

The bed is covered with a polythene sheet, which should not touch the straw, to create high humid conditions. After 12-15 days, the beds will be completely covered by a white cottony fungus. It is now time to remove the polythene bags. The beds are arranged on the raised platform are watered twice a day to ensure the presence of humidity. Wet gunny bags may be hung for the same purpose. Small button like growths (fruit formation) will appear within a week and are ready for harvest. Harvesting should start a day before the buttons open or after the volva ruptures and can be continued for a couple of weeks. Three to four flushes appear within a period of 4-5 weeks. The fruit bodies arise in clumps of variable sizes and shapes and should be harvested by cutting or plucking them at the stacking region in uniform size.  The yield will be about 50% or more than the weight of the substrate.

12.2.5. Processing

Paddy straw mushroom is more perishable than other edible mushrooms and cannot be stored at 4 ^oC as it undergoes autolysis at this temperature. Paddy straw mushroom can be stored at a temperature of 10 to 15 ^oC for 3 days and little more at 20 ^oC or under controlled atmosphere storage. The loss of moisture in 4 days stored mushroom could be as high as 40-50% in unpacked mushroom, while it can be reduced to 10% on packaging in perforated polythene begs. Paddy straw mushroom can be processed by canning, pickling and drying.

12.2.6. Nutritional value

Mushrooms have been recognized as a source of protein rich food. In general, paddy straw mushroom contains 100 g of fresh mushroom contains 1-2 g of carbohydrates, 5 – 8 g of proteins, 0.2-1 g of fat, 5-15 mg of vitamins, 0.5-1g of minerals and rest is moisture.  The straw mushroom is known to be rich in minerals such as potassium, sodium and phosphorus.