Grow Oyster mushrooms for nutrition and health
(Published in November 2008 issue of Goa Today)
Nandkumar Kamat
Goans are ecophiles and biophiles. They love outings, trekking, hiking, photography, greenery, indoor plants, gardening, sports fishing, making their own compost. Organic farming is growing in popularity. On the other side the morbidity and mortality profile of Goans show a record spurt in life style related and diet related diseases. This is possibly a combined effect of high calorie, high fat, low fibre diet , alcohol consumption and a fast, stressful routine. All types of tumours and cancers are commonplace. Obesity, Diabetes, hypertension, cardiovascular diseases are creating havoc. One way of finding a solution to some of these problems is including sufficient probiotics and immunomodulators in the diet on regular basis. Edible plants and mushrooms are nature’s ancient medicines. The cheapest sources of beneficial nutraceuticals are the edible mushrooms-especially those varieties which are suited to the region and climate and which one could grow like the vegetables in a small kitchen garden. The cultivation cycle could be planned in such a manner that everyday one can ensure supply of home grown oyster mushrooms. September to March is the best season for cultivation of Oyster mushrooms. November to February gives bumper crops as the Oyster mushroom species love the weather unless it becomes cold. Oyster mushrooms are a group of many species led by world’s second most popular edible mushroom species –Pleurotus ostreatus. The world consumes more than a million metric tones every year. India grows just a few thousand tones. I strongly recommend launching of a door to door movement to popularize cultivation of Oyster mushrooms-not for earning profits but purely for self consumption as essential natural nutraceuticals. Goans should learn to cultivate mushrooms as a kitchen garden crop. We rarely sell the produce of kitchen gardens unless it is in a marketable surplus. So cultivate oyster mushrooms to provide an important nutritional supplement, the necessary probiotics for your family. Anyone from five year old kid to a 90 years old healthy person can do it if the basics are learnt properly and simple hygienic practices are followed scrupulously. There are several advantages of growing oyster mushrooms at home. First it would teach one basics of biotechnology or how biodegradable materials like agrowaste can be converted into edible proteins. Second it would introduce one to microbiology-handling of the delicate living mushroom fungus unlike the green plants. Third it would teach one about physiology and technology of production-how to control temperature, light, humidity and ventilation. Fourth it would also teach the cultivator about farm hygiene, pathology and how it can affect the crop. Fifth, it would also generate excitement when first crop appears and produces good harvests. On the way cultivators could learn to keep their diary where they would be able to record their day to day observations. Oyster mushroom cultivation can be enjoyed individually or as a team by the family members. Self help groups can do it on larger scale. It is really a fun to grow your own, ready to cook food which also doubles up as a preventive medicine. As an illustrative example some of the benefits of Pleurotus ostreatus (Oyster mushroom) are given in the Box 1.
Box 1 Beneficial aspects of Oyster mushrooms
Mushrooms are nutritious
On a dry weight basis mushrooms have a high protein content (19-35%) . The quality of mushroom proteins is excellent because all essential amino acids for man including lysine and methionine, which are found. The protein content could be compared to 7.3% in rice, 13.2 % in wheat, 39.1 % in Soybean and 25.2 % in milk. Mushrooms have a high proportion of unsaturated fatty acids, supply vitamins such as riboflavin and nicotinic acid, pantothenic acid and appreciable amounts of thiamine , folic acid, and ascorbic acid. Mushrooms contain fibre, minerals and are low in calories, sodium, fat and cholesterol. This is a good news for patients with hypertension.
Oyster mushroom cultivation made easy
Pleurotus ostreatus is the second largest cultivated mushroom in the world. In India it
is commercially cultivated. Strain improvement and hybridization is mostly done with strains imported from Europe. Many varieties of Oyster mushrooms are cultivated in India. In Goa the white ‘florida’ variety, the strains released by IIHR, Bangalore and the Dharwad strains are popular. A brownish variety is know as sajor-caju which grows well. The raw material for oyster mushroom cultivation is any cheap biodegradable material with good moisture absorption capacity-most preferred is paddy or wheat straw. Beginners should not venture in any other material than paddy straw.
Basic principles
The oyster mushroom seed is known as spawn. It is grown on grains-from pure culture of commercial strain on sterilized wheat or jowar. Spawn is sold in glass bottles or polypropylene packs. Every grain is penetrated by thin filaments of fungus called mycelium. Under right conditions, the mycelium produces powerful enzymes and coverts lignocellulosic material into mushroom biomass. In the process carbon dioxide and some moisture is lost. So mushroom cultivation is solid state fermentation where carbohydrates are converted into protein rich edible fungal biomass. A cultivator learns to control the factors which permit good colonization of his substrate by mushroom mycelia and allows good conditions for fruiting while keeping away competitors and contaminants.
Identify a shaded place
You just need a tablespace or a canopied gallery to cultivate oyster mushrooms- a few kilograms at a time. Larger scales need rust proof shelves. The place need to be cool, free from mud, dirt, dust, insects, rats, squirrels and not exposed directly to sun, breeze or rains. There need to be provision for artificial light and ventilation and proper drainage.
Tools of trade
Paddy straw although not the cheapest is easily available local agrowaste. It is cellulosic material and is easily colonized by mushroom fungus after absorbing moisture. Ensure a good supply of crisp, fresh, well dried paddy straw. Store it in a dry place. Even the straw used for packaging would do. It can be sourced from glass dealers or fruit sellers in municipal markets. Polytheylene bags (45 X 30 cm) are preferable for cultivation. This techniques is known as polybag method. You need a chopper to cut the straw in small pieces. Use a plastic bucket or tub to soak the straw in water. A large utensil to boil the straw. Boiling at steaming temperature kills the surface contaminants.
The mushroom spawn
Oyster mushroom spawn of good quality can be ordered and purchased from mushroom laboratory, farmers’ training center, Ela farm, Old Goa or KVK, ICAR, Old Goa. A good spawn is recognized by uniform pure white colour and no foul odour. It needs to be used within 2-3 days.
Substrate treatment
Substrate means the raw material used to grow mushrooms. Its’ treatment involves, cleaning, chopping, soaking and boiling. The paddy straw has to be cut by chopper into finger size (3-5 cms long) pieces. Larger pieces are not good. Begin with two kilograms of fresh paddy straw. This would give you two to three filled bags. A kilogram of fresh paddy straw absorbs water about one and half times its’ weight after soaking overnight ( 8-12 hours). So two kilograms of chopped paddy straw would give a wet mass of about five to five and half kilograms. Take care that the straw pieces are kept under weight and do not float in the bucket or tub. After soaking drain the brownish water. Squeeze the excess moisture. Then use a large metallic vessel with a loose lid on top to boil the soaked pieces till steam builds up. Keep a lid till the straw gets cooled. Remove the boiled straw, drain excess water. Spread the straw on a clean plastic sheet. It is now ready to be filled in the cultivation bag.
Spawning and spawn run
The real fun begins now. All these operations have to be done on a clean surface, without any breeze. It is better to wash the hands with soap. Open the spawn bottle and remove the sticky spawn with a long spoon or clean knife. It could be emptied on a clean plastic plate. Loosen it to separate individual white grains. Remember, one bottle of spawn is about 200 grams and can be used for maximum three bags ( about six kg of wet straw). Make a small mound of the ramified white grains on plate from where you would take a handful each time to mix with the straw. This is like casting seeds in a farm. Open the polythene bags. Rinse with solution of Dettol. This kills any contaminants. Then put a layer of boiled straw, compress it evenly. Then on top of this layer, sprinkle in a spiral fashion a pinch or two of spawn grains taking care that full surface is covered. Then add another thick layer of straw to be topped by a layer of spawn grains. This is repeated 7-8 times to get a compact vertical cylindrical shape. Now you can see alternate layers of straw and spawn. A small space adequate to tie up the mouth of the bag is kept at top. The polybag can now stand on its’ base if it is properly and uniformly filled and compacted. The mouth is tied with a rubber band. Several bags like this could be prepared as per requirements. The bags are then kept in darkness in a clean, dry place to permit’ spawn run’ or multiplication of the mycelia from the grains on the straw. It may take from 8 days to 15 days depending on temperature and spawn ratio ( the ratio of weight of spawn to weight of straw). The favorable temperature for good spawn run is between 25-32 deg. Cel. And best is 27 deg. Check each bag for sign of contamination-by identifying any coloured patch.
Getting Ready for the harvest
One can notice that spawn run is complete when all the bags turn white and compact. The bags need to be brought out in light. Now the multiplied mycelium covering and binding the straw is looking for light, air and a semblance of rain. The top of the bags are rolled down to one third of the length and a gentle mist of water is sprayed from sides. This is done 2-3 times a day. The lights are needed at least 12 –16 hours a day. After opening of the bags, within two days small pinheads are noticed. If the full bag has uniform light then the pinheads would be found on all sides. If light falls on one part the pinheads would grow in that area first. The pinheads would now grow to produce oyster shaped mushrooms. The bags need ventilation to remove extra heat and trapped carbon dioxide. This is done using a pedestal, ceiling or table fan. Fans should be switched off during harvesting. Once the bunches of oyster mushrooms enlarge the spraying of water continues lightly so that the substrate does not become dry. When mushrooms reach a size of 4- 7 cms it is time to harvest them by detaching from the bag. This would be the first crop, known as ‘flush’. The flushes would continue for another 7-14 days with short gaps initially and long gaps for last few crops. Every time the older layer of substrate needs to be removed. Finally after 4-6 flushes no more nutrition is left in the bag and very few mushrooms may appear. The straw in the bag can then can be used either as a cattle feed after mixing it with jaggery or as an excellent soil conditioner after chopping it and mixing with soil or garden compost. Under normal conditions a polybag of two and half kg should yield at least a kg of fresh mushrooms. But getting 500-800 grams from all flushes is sufficient if it is your first trial. The freshly harvested mushrooms could be gently washed and used for many delicious recipes. Oyster mushrooms make excellent soups. The mushrooms can also be dried using a solar drier or a Stockli type dehydrator at 70 deg. cel. till they turn crisp as biscuits. The dried Oyster mushrooms need to be preserved in air tight containers.
What ensures success?
Success in cultivation depends on patience, understanding basic principles, choice of quality spawn, straw, strict compliance of microbiological and cultivation standards and farm hygiene. It helps to keep records for every batch. Two factors –consistent temperatures above 32 deg. or below 20 deg. and low (less than 60 % RH) or very high humidity (above 90% RH) affect crops. A cheap portable thermohygrometer would help to record both.
Value addition for surplus crops
In case there is a marketable surplus, ( few kgs per week or more) mushrooms can be processed. Mushroom soup powders, pickles, wafers and noodles are very popular in Goa. This market can be developed. The growers need to learn the basic techniques of processing mushrooms first. Only an outline is given below.
Mushrooms respire fast. They lack protective covering and being rich in water and soft in texture are highly perishable at ambient temperatures. The post-harvest technology of mushrooms focusses on the nullification of ill-effects such as decrease in freshness, water loss, browning, off-flavour development etc. Some methods of mushroom preservation include the following:-
1. Deep freezing
2. In 20% salt solution
3. In vinegar
4. In sodium or Potassium metabisulphite solution
5. Sun drying
6. Dehydration using an oven or drier
7. Freeze-drying
8. Frying and salting
9. Canning and bottling
10. Pickling
Of these freeze drying , canning and bottling methods are expensive and are used only by the large processing units whereas other methods are inexpensive and suitable for small quantities of mushrooms. More information could be obtained from Central Food Technological research institute-CFTRI, Mysore.
Readers could take practical advice on cultivation from Directorate of agriculture , Panaji, Mushroom laboratory Ela farm and From KVK, ICAR. Many technical details have been omitted to keep the methods as simple as possible. If one succeeds in gardening then mushroom cultivation is not difficult. Include Oyster mushrooms in your menu every day and fight ageing and diseases.
