Mushroom processing and Preservation

Mushroom processing

Freshly harvested mushroom is highly perishable as it is susceptible to deterioration by the enzyme and microorganisms. It has been realized that merely producing mushroom is of no use unless these are properly preserved, keeping in view the export objectives. Hence, following proper processing and storage methods is of supreme importance. Two types of preservation techniques are available:

1) Short term preservation
2) Long term preservation

Short-term preservation

Low temperature is effective for short-term preservation. Mushrooms may be packed in wooden cases with three compartments; ice is placed in the central compartment and mushrooms are packed in the two other sections. Mushrooms may also be packed in bamboo baskets and transported by airfreight. An aeration channel is formed at the center of the basket and dry ice, wrapped in paper, is placed above the mushrooms.

Mushrooms stored in a perforated plastic box at 10-15ºC have excellent keeping quality for up to 4 days and the loss of moisture is less than 5 per cent. Straw mushroom can be stored more effectively at button stage than at any other stage. At temperatures below 10ºC, however, the mushrooms liquefy rapidly, irrespective of type of packaging due to chilling injury.

Long-term preservation

Canning, pickling, and drying processes are employed for long-term storage. These processes are not always suitable for all types of mushrooms. The quality of the finished product is rarely comparable with that of fresh mushrooms.

a) Canning

Canning is the most common process for preserving mushrooms. For this, cleaned mushrooms are placed in cans containing 2.5 % sodium chloride and 0.25–0.5 % citric acid. The cans are then sealed and sterilized in autoclave for one hour at 100-120ºC.

b) Drying

Mushrooms can be dried by sun drying and thermal power drying. For general drying, the picked mushrooms are exposed to the sun for about 2-4 days. Dried mushrooms are highly hygroscopic and readily absorb moisture from the air. The dried mushrooms should therefore, be put into polyethylene bags, sealed, and kept in a dry, cool, and dark place. For prolonged storage, dried mushrooms should be packed in cartons or wooden boxes and kept at 2-5ºC in a low temperature store.

c) Use of chemicals

Fresh mushrooms can be preserved for about 10 days at room temperature by steeping in a solution containing 2.5 per cent common salt, 0.2 per cent citric acid, 0.1 per cent ascorbic acid, 0.1 per cent sodium bicarbonate and 0.1 percent potassium metabisulphite. This method of preservation can be used at places where facilities for canning, freezing and dehydration do not exist.

Market potential

Mushrooms are delicacy with definite food value. It has already acquired commercial status almost all over the world. Govt. of India has declared mushroom cultivation as a major thrust area. Mushroom dish is a common item in all the big hotels.

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