Freezing is a food preservation method that inhibits microbial growth by reducing the temperature below the freezing point of water. Freezing does not kill microorganisms but stops their growth. The quality of frozen food depends on the freezing rate, storage temperature, and packaging. foods frozen quickly at minus 18 degrees Celsius (0 degrees Fahrenheit) or below retain better texture and nutritional value than foods frozen slowly.
Rapid freezing produces smaller ice crystals that cause less damage to cell walls than the large crystals formed during slow freezing. The temperature is lowered to minus 18 degrees Celsius (0 degrees Fahrenheit) as quickly as possible. The freezer is kept at a constant temperature; temperature fluctuations cause ice recrystallization, which damages food texture. Freezer burn, the grayish, dry appearance on improperly packaged frozen food, is caused by Dehydrating from air contact.
Most vegetables require blanching before freezing to inactivate enzymes that cause off-flavors, color changes, and nutrient loss during storage. The vegetable is immersed in boiling water for 1 to 5 minutes (depending on the vegetable), then immediately plunged into ice water to stop the cooking. The blanching time is specific to each vegetable. Underblanching stimulates enzyme activity worse than no blanching. Overblanching causes nutrient loss and texture deterioration.
food is packaged in materials that are moisture-vapor-proof and resistant to freezer temperatures. Options include rigid plastic containers, freezer-grade plastic bags, vacuum-sealed bags, and heavy-duty aluminum foil. Air is removed from the packaging to minimize freezer burn. A vacuum sealer provides the best protection. The package is labeled with the contents and date.
The freezer is maintained at minus 18 degrees Celsius (0 degrees Fahrenheit) or lower. The temperature is monitored with a thermometer. The freezer is defrosted when ice buildup exceeds 0.6 centimeters (0.25 inches). A full freezer maintains temperature better than an empty one. In a power outage, the freezer stays cold for 24 to 48 hours if unopened. A generator is recommended for off-grid freezers.