Food preservation has been a crucial practice throughout human history, dating back to ancient times when refrigeration and modern preservation methods were nonexistent. Ancient civilizations developed various techniques to preserve food, including salting, fermentation, and drying. In fact, there is evidence indicating that Middle Eastern and Oriental cultures were actively engaged in drying foods as far back as 12,000 B.C. Today, thanks to modern technology, a wide range of preservation techniques are available and continuously improving. One such effective food preservation technique is freezing.
By definition, freezing refers to the process of lowering the temperature of food items to below their freezing point, typically to around 0°C (32°F) or lower, in order to preserve them for extended periods. This preservation method involves storing food in a freezer or other cold environment where the low temperature inhibits microbial growth and enzymatic reactions that lead to spoilage. By freezing food, moisture within the food is converted into ice crystals, which slows down chemical reactions and microbial activity, effectively halting the deterioration of the food’s quality, flavor, and nutritional value.
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HOW FREEZING WORKS
When food undergoes the freezing process, its water content undergoes a transformative phase change as the temperature drops. Initially, water molecules within the food coalesce and align to form ice crystals. These crystals disrupt the structural integrity of the food’s cells, causing them to expand. Consequently, the growth of microorganisms such as bacteria, yeast, and mold is significantly inhibited.
The inhibition happens because these organisms depend on water for their growth and reproduction. Water plays a vital role in life, serving as a medium for biochemical reactions, dissolving nutrients and waste products, and providing structural support to cells. When lacking adequate water, microorganisms cannot perform essential metabolic processes, absorb nutrients, or uphold cellular structure and function, thus hindering their growth and reproduction.
Moreover, enzymes that catalyze biochemical reactions within the food are rendered inert at low temperatures, further impeding degradation processes. When fruits are frozen, the enzymes responsible for ripening and softening, such as pectinase and cellulase, are deactivated due to the cold temperatures. For instance, in frozen strawberries, the enzyme polygalacturonase, which breaks down pectin and leads to fruit softening, is inhibited. As a result, the strawberries maintain their firm texture and structural integrity even after thawing, preserving their quality and preventing mushiness.
The rate at which food freezes plays a pivotal role in preserving its overall quality. Rapid freezing, facilitated by placing the food in a freezer maintained at a sufficiently low temperature, fosters the formation of small ice crystals. These small crystals exert minimal damage on the cellular structure of the food. Conversely, slow freezing permits the formation of larger ice crystals. These larger crystals can puncture cell walls, resulting in a loss of texture and moisture when the food is eventually thawed.
FREEZING FOOD PROPERLY
Ensuring proper freezing of food preserves its quality, taste, and nutritional content by minimizing the formation of ice crystals and averting freezer burn. Adhering to appropriate freezing methods like rapid freezing and employing airtight packaging helps extend food shelf life, and minimize waste.
Choosing the appropriate packaging
When choosing packaging materials for freezing food, focus on options that provide both moisture-proof, airtight seals and durability to endure freezing conditions without becoming brittle or cracking. Consider utilizing alternatives such as resealable plastic bags, vacuum-sealed pouches, freezer-safe containers, and aluminum foil. By utilizing moisture-proof, airtight packaging, you protect against freezer burn. Freezer burn is a phenomenon that occurs when moisture evaporates on the food’s surface, leading to the formation of ice crystals, dehydration, and oxidation. This process alters the texture, flavor, and appearance of the food.
Preparing food items for freezing
Proper preparation and packaging are vital steps to maximize the quality of frozen food. It helps to minimize the risk of spoilage and ensures that frozen food remains a convenient and nutritious option for consumption.
- Flash freezing
During flash freezing, the food is exposed to either very cold air or liquid nitrogen, which freezes it rapidly. This rapid freezing helps to form smaller ice crystals within the food, minimizing damage to its cellular structure. When doing this, arrange each food item or portion in a single layer on a baking sheet lined with parchment paper. Allow them to freeze until firm before transferring them into freezer bags or containers. This method prevents the items from clumping together, making it easier to portion and retrieve them when needed.
- Prepare food items in portions
To expedite the thawing process and minimize food waste, it’s advisable to partition food into smaller servings before freezing. This strategy not only promotes faster thawing but also lowers the likelihood of discarding excess food. Moreover, dividing food into smaller portions enables you to thaw precisely the amount required for a particular meal, rather than defrosting an entire batch unnecessarily.
- Prevent overcrowing
Overcrowding can impede airflow and disrupt the freezing process, potentially leading to uneven freezing and extended freezing times. This can compromise the quality of the frozen food, affecting its texture and taste. By allowing adequate space between items, you facilitate efficient cooling and freezing, preserving the freshness and quality of your stored food items. Additionally, organizing the freezer with ample space ensures easier access to items and reduces the risk of items becoming buried and forgotten, ultimately minimizing food waste.
PRACTICES FOR COMMONLY FROZEN FOODS
Baked goods
Wrap individual servings of baked goods, such as muffins, cookies, and bread, with plastic wrap or aluminum foil before storing them in freezer bags or containers. Wrapping them individually allows for easy retrieval and thawing of single servings without affecting the rest.
For larger baked items like cakes or pies, freeze them without covering on a baking sheet until they become firm. Afterward, tightly wrap them with plastic wrap and aluminum foil. Larger baked items, due to their size, require a different freezing approach. Freezing them uncovered initially allows them to set without trapping moisture, preventing soggy textures. Subsequently, tightly wrapping them with plastic wrap and aluminum foil ensures maximum protection against freezer burn and maintains their quality during storage.
Meats and seafoods
Divide meats and seafood into individual meal portions before adding seasoning or marinade according to preference. This step involves dividing larger cuts of meat or seafood into smaller, ready-to-cook portions. Doing so allows for easier handling and portion control during meal preparation.After portioning and seasoning, lay the individual servings in a single layer on a baking sheet. Freezing them in this manner helps prevent them from sticking together and allows for uniform freezing, ensuring that each portion freezes evenly. After the portions have frozen completely, transfer them into freezer-safe bags or containers. This step helps protect the portions from freezer burn and maintains their quality during storage.
Fruits and vegetables
Prepare fruits and vegetables by washing, peeling, and cutting them into desired sizes before subjecting them to blanching in boiling water, followed by rapid cooling in an ice bath. Blanching helps to partially cook the produce, which can help preserve color, texture, and nutrients before freezing.
Once blanched, remove any excess water from the produce to prevent ice crystals from forming during freezing. Patting them dry helps to remove surface moisture, which can lead to freezer burn if left behind.
Soup and stews
Ensure that soups and stews have cooled down entirely before transferring them into containers suitable for freezing, leaving a slight gap at the top to accommodate expansion. Allowing soups and stews to cool completely before freezing prevents condensation inside the containers, which can lead to freezer burn. Leaving space at the top allows for the expansion of liquids as they freeze, preventing the containers from cracking or bursting.
