General Description/History

• A fungi
• Does not photosynthesise, instead they require an external source of food
• Umbrella shaped with soft brown/pink gills under the cap.

Freshness, colour and shape are the three points to consider when buying mushrooms. Select smooth, clean, white mushrooms, avoid withered product as this is a sign of age.

Mushrooms are extremely versatile, adding exciting flavour and texture to meat, poultry and seafood. Cheese and eggs also team well with mushrooms. Button mushrooms can be filled with a wide variety of stuffings including rice, vegetables, oysters, cream cheese etc.

Mushroom cultivation began in Australia in the 1930’s in the then incomplete and unused Circular Quay railway tunnel in Sydney. In the 1950’s most mushrooms were grown outdoors in heaped or ‘ridge-beds’ of compost in disused railway tunnels. In the last 20 years there has been considerable technical change in the method and degree of sophistication of mushroom cultivation techniques. Most growers have invested large sums of capital in specially designed and insulated buildings that control temperature, humidity and ventilation, and where pest and disease prevention and control is easier. Earliest references to mushrooms date back 3,000 years or more to the days when the pharaohs of Egypt monopolised its uses as a food, the mushroom being much too fine a delicacy to be eaten by common people. Whether the mushroom was a native of the Nile Valley, early chronicles failed to say. The chances are, however, that this food, “fit for a king”, grew rather widely wherever soil and climatic conditions were hospitable to it’s delicate nature. The first record of the cultivation of mushrooms dates back to the reign of Louis XIV (1638 to 1715). In the year 1707 a Frenchman called “Tournefort”, wrote a description of the methods of cultivation. He writes that in Paris, there were many caves from which building stone had been quarried and it was in these caves that the cultivation of mushrooms was carried out. There is a record dated 1867 stating that one of these caves housed 21 miles of mushroom beds producing 3,000 pounds of mushrooms daily.

Three systems, shelf, tray and bag, are used for mushroom growing. Tray systems are used by larger growers and are the major production method. The bag system, which allows for a smaller financial outlay is becoming increasingly popular. This method also helps to alleviate pest and disease problems by allowing fast and easy removal of infected bags.

Mushroom growing is highly technical and the use of a number of technical terms is unavoidable. It involves the preparation and pasteurisation (peakheating) of the substrate (compost), the addition of fungal inoculum grown on cereal grain (spawn), and covering the compost surface after it has been colonised by the mushroom mycelium with a layer of peat or soil (casing). Mushrooms usually can be harvested 29-32 days after spawning. The normal period of cropping varies from 6-8 weeks with mushroom fruit bodies appearing in flushes approximately one week apart. The compost is then discarded and the cycle starts again. Commercially, almost without exception, mushrooms are grown in specially constructed sheds. Existing farm buildings such as fruit packing sheds and poultry sheds can be used, but require major modifications and then can still have limitations, because of their construction and pest and disease problems.

Mushroom growing sheds provide:

1. Insulation to prevent fluctuations in temperature and energy losses from heating and cooling. A common insulation construction material used is polystyrene sandwich panels similar to those used to construct coolrooms.
2. Humidity and heat controls so that during mushroom growing, the temperature and humidity conditions can be evenly maintained regardless of the weather. 
3. Ventilation so that growing mushrooms have a supply of fresh air and their growth is notinhibited by a build up of carbon dioxide. An air filtering mechanism to help keep out airborne spores and insects is desirable. Crops at different stages of production should be separated to prevent the spread of pests and diseases from older to newer crops. 
4. Cement floors with adequate drainage.

Mushrooms are harvested in 7-10 day cycles, but this may be longer or shorter depending upon the temperature, humidity, strain, and the stage when they are picked. Mushrooms are harvested by hand using a twisting motion to remove them from the bed, then the stalk is trimmed and usually graded straight into the boxes they will eventually be sold in. Approximately 60% of labour cost or 40% of total costs on a mushroom farm are picking costs. The performance of pickers will vary according to the experience and agility of the picker, free space available between the trays, beds or bags, lighting, and the size and number of mushrooms standing singly or clumped on the bed. An average picking rate (including grading) is 12-15 kg/hour of good quality button/cup white mushrooms. Off white strains and large flat mushrooms generally have a higher picking rate. Mushrooms have the ability to double their size in 24 hours. They can easily grow into an inferior, lower value product if not picked at the correct time. Fresh mushrooms are sold in three grades, namely buttons, cups and flats, each grade referring to a stage of growth. Buttons are small unopened mushrooms and are nominally sold for the higher price. A cup is when the button is allowed to grow and the cap is beginning to open so that some gills can be seen. If the mushroom cap expands fully so that all the gills are visible it is referred to as a flat.

Further grading into large and small buttons, large and small cups, etc is desirable. Mushrooms are picked and packed with the stems upwards, directly into the box or crate for distribution to minimise the handling of the easily bruised mushroom fruit bodies. Signs of deterioration of mushrooms are a brownish discolouration of surfaces, opening of veils, elongation of stalks and a general softening of the surfaces due to loss of moisture. Deterioration of the mushrooms will be minimised if they are cooled immediately and kept cool throughout the distribution chain. Mushrooms are very perishable and their appearance deteriorates each day. No attempt should be made to store them for any length of time. Mushrooms are marketed in 3kg cartons.

Nutritional Value

Mushrooms are a good source of riboflavin and niacin and also contain protein, folic acid and vitamin B12. 100kJ/100g.

Storage/Handling

0°C and 90 – 100% relative humidity. Keep covered and away from refrigeration fans.

Consumer Storage: Store mushrooms in a brown paper bag in the refrigerator crisper.

Interesting Facts and Myths?

Mushrooms are found all over the world and have been a very honoured food in many cultures. Ancient Egyptians considered them to be food for the royals. The French adored the fungus and began harvesting them in caves during the seventeenth century.

The largest living organism ever found is a honey mushroom, Armillaria ostoyae. It covers 8.8 square kilometres of land in the Blue Mountains of eastern Oregon, and it’s still growing!

Some mushrooms are extremely poisonous. Some famous victims of mushroom poisoning: The Great Buddha, the Roman Emperors Tiberius and Claudius, banquet guests of the Emperor Nero, Alexander I of Russia, Pope Clement II, King Charles V of France. It’s best to buy your mushrooms from a reputable grower or grocer instead of hunting them yourself.

There are close to 40,000 varieties of mushrooms.

Mushrooms are not a true vegetable in the sense that they do not have any leaves, roots, or seeds, and do not need light to grow. So what exactly is a mushroom? It is a fungus, which grows in the dark and creates more mushrooms by releasing spores.

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Botanical Name: Agaricus bisporus (Button Mushroom) (Agraiceae)

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Growing Areas: 

QLD – Brisbane Metropolitan Area, Granite Belt, Maclean 
NSW – Gosford, Hunter Valley, Windsor 
VIC – Mernda SA Hills District