Mushroom Storage and Processing
Mushrooms are rich in the following nutrition; proteins, antioxidants and are known to have a low calorie source of fiber. Mushroom has zero sodium (or fats) and are also known to have zero cholesterol, which partly help a person to have lower chances of developing high blood pressure, stroke, and heart disease, which are caused by taking too much sodium and cholesterol. This article discusses mushroom storage and processing methods. Mushrooms are known to have a high respiration rate, which continues the moment you harvest your Mushroom vegetable (Botanically classified as fungi, but considered as a vegetable). For example, if we compare the respiration rate of oyster mushrooms with other fruits, we can see that it is three times greater, which agrees that Mushrooms have a higher respiratory rate. For this reason, you need to handle them with great care. What causes Mushroom spoilage when keeping or storing them are bacteria and fungi within the mushrooms. In cold storage places, the Bacteria and enzyme activities within the mushrooms continue to increase and this has a negative effect. Mushrooms have 85 to 95% and this acts as a favorable condition for bacterial growth which is bad. Mushroom also has no barriers to water loss from their surface. After harvesting, Mushroom lose much of its water through humidity and atmospheric pressure.
If we compare the fresh Mushroom with other crops, we can see that mushroom has a shorter shelf life, therefore, it is very important to preserve it with a special care or market it as soon as the harvesting is done. After harvesting, mushrooms can either be stored in cold storage or other places or environments where you are able to control it from spoilage.
The following are the commonly used methods to preserve your Mushrooms:
1. Short Term Storage
This is prolonging the shelf life of fresh mushrooms by refrigerating it at a temperature of 1 to 4℃. Cooling the mushrooms at such a lower temperature, resulting in lower rates of all the physiological process within the mushrooms (also called a lower respiration rate). Mushrooms' shelf life varies from 1 day to 2 weeks. Cooling Mushroom under a temperature of 1 to 4 °C is considered as an effective short term preservation. This is done by retarding the growth of microorganisms, reducing the rate of post harvest metabolic activities of the mushroom tissues, among others. After harvesting, Mushrooms have a metabolic rate temperature of a range of 15 to 18 °C and to stop this metabolic process rapidly, make sure mushrooms are cooled to a storage temperature of 0 to 2℃ within five hours of picking. Oyster mushroom can best be kept in a temperature range of 8-10℃ in packed container wrapped in plastic film.
2. Long Term Storage
For long-term storage of mushrooms, the following is used; canning, pickling and drying. Take note that these long term storage processes are not always suitable for all types of mushrooms.
(i ) Drying
Drying is best suitable preserving method for edible shiitake mushrooms. This method, is not necessarily used for button Mushrooms or Oyster Mushrooms, but oyster mushrooms can also be stored and marketed in dried form. After drying mushrooms are nearly 10% of total weight. Drying is used to preserve the mushrooms by removing enough water and this is important as it inactivate the enzymes and microorganisms. Dried mushrooms are good for long-term storage and transportation. The following are the commonly used methods for preserving Mushrooms through drying.
a. Sun drying
Under this method, you spread your mushrooms on the shelves in such way that the gills face upward and are directly exposed to sunlight for drying. Amount of time taken to dry under this method, it varies depending on weather conditions. Sun-dried Mushrooms have lower quality than thermal power drying or hot-air drying. The moisture content is also high under this method and this encourages the Mushroom to be susceptible to mold and pests.
b. Thermal power drying
Under this method, the process of thermal power drying, start on mushrooms at a relatively low temperature. Make sure the Mushrooms are dried during sunny days at an initial temperature of 35℃, while during damp days, mushrooms should be dried at an initial temperature of 30℃. Thereafter, you increase the temperature gradually and then kept at 40-60℃ for 12-18 hours. This method is able to preserve Mushroom appearance and flavor.
c. Hot-air drying
Under this method, hot air is blown into the dryer and mushrooms on the shelves are exposed to hot air for drying. The heaters and recirculation are used to control temperature and air humidity to an optimal condition. Make sure the drying chamber is heated to a temperature of 40 to 50℃ before loading the mushrooms. The size of the drying chamber depends on the production scale. Under this method, Mushroom moisture content is absorbed to 20%. You can then store your hot-air dried Mushrooms in boxes or containers having a temperature of 2 to 5°C.
(ii) Canning and bottling
This method is commonly used in preserving Mushrooms. Canning process is divided into seven basic operations: cleaning, blanching, canning, sterilization, cooling, labeling, and packing. Take note that if the Mushrooms are not canned immediately, they should be refrigerated until processing starts. Batch process can be used where the cans can be placed in an autoclave and sterilized for one hour 120-130℃.