Unit 4: Storage and Nutrition

Storage

Fresh mushrooms are highly perishable. They have a high water content (80-90%) and continue to respire after harvesting, which leads to rapid browning, texture loss, and spoilage. Proper storage is essential to extend their shelf life.

Short-term Storage

• Refrigeration: This is the most common short-term method. Storing mushrooms in a refrigerator (around 4°C) slows down respiration and microbial growth.
• Packaging: They should be stored in a porous paper bag, not a sealed plastic bag (which traps moisture and causes them to become slimy).
• Shelf Life: This method can keep mushrooms fresh for up to 24 hours or a few days, depending on the species.

Long-term Storage

To preserve mushrooms for weeks or months, they must be processed. Methods include:

Drying

• Method: This is one of the oldest and easiest methods. Mushrooms are sliced and sun-dried, oven-dried, or dried in a food dehydrator until brittle.
• Principle: Removing water (down to 10-15%) inhibits the growth of bacteria and molds.
• Result: Dried mushrooms (like dried Shiitake or Oyster) have a very long shelf life and their flavor becomes more concentrated. They must be rehydrated in water before use.

Canning

• Method: Mushrooms (usually button mushrooms) are cleaned, blanched (briefly boiled), and sealed in cans with a brine (salt solution). The sealed cans are then pressure-cooked to kill all bacteria and spores, making them shelf-stable for years.
• Result: This method preserves the mushroom but changes its texture and flavor.

Pickling

• Method: Mushrooms are cooked and preserved in a high-acid (vinegar) and/or high-salt solution, often with spices and oil.
• Principle: The high acidity and/or salinity creates an environment where microbes cannot grow.
• Result: A "pickle" with a tangy flavor, common in many cuisines.

Storage in Salt Solutions (Brining)

• Method: Mushrooms are stored in a strong salt solution (brine).
• Principle: The high salt concentration draws water out of the mushroom and inhibits microbial growth.
• Result: This is often used as a temporary bulk storage method by industries before the mushrooms are canned or processed further.

Papads

• Method: Mushroom paste or powder is mixed with lentil or rice flour, spiced, rolled thin, and dried in the sun.
• Result: A dry, storable 'papad' that can be roasted or fried. This is a value-added product.

Nutritional Profile

Mushrooms are a "superfood" because they offer a unique combination of nutrients.

Macronutrients

• Proteins: Mushrooms are a significant source of protein (20-30% on a dry weight basis). The protein quality is high, containing most of the essential amino acids needed by humans.
• Carbohydrates: They are low in simple carbohydrates but rich in complex ones. They contain no starch.
• Crude Fibre Content: Mushrooms are an excellent source of dietary fiber, particularly beta-glucans and chitin (from the fungal cell walls). This fiber is good for digestion and has cholesterol-lowering effects.
• Fats: They are very low in fat.

Micronutrients

• Vitamins: Mushrooms are one of the few non-animal sources of Vitamin D (especially if exposed to sunlight or UV light). They are also a powerhouse of B-complex vitamins, such as:
  • B2 (Riboflavin)
  • B3 (Niacin)
  • B5 (Pantothenic Acid)
• Mineral Elements: They provide essential minerals that are often lacking in a typical diet, including:
  • Selenium: A powerful antioxidant.
  • Potassium: Important for fluid balance and blood pressure.
  • Copper: Needed for iron absorption.
  • Phosphorus: Important for bones and energy.