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.

Let’s discuss further.

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.

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Are fresh foods superior to canned and frozen? Well, for most of the time, fresh foods are the best in terms of quality (flavor, texture, and nutrients). This is almost true if you were the one who raised and harvested them, and the food in question is in season. But if the food is out of season, we would be dealing with produce that require transport and extended storage period. In most cases, additional process like canning or freezing has to be carried out. This is to ensure the produce reaches the customer without compromising quality.

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However, the common belief is that fresh, especially fresh-from-the-farm fruits and vegetables are always superior to canned and frozen. For this reason, most people opt for fresh produce. Well, the truth is that the difference is not significant. And there are some instances that frozen foods contain more vitamins and minerals than their fresh counterparts. The same thing can be said for canned foods.

Here’s how.

FLASH FREEZING OF PRODUCE AT ITS PEAK QUALITY

Fruits and vegetables are perishable food items. To prevent them from deteriorating quickly, they are usually flash frozen at the same location where harvested. Clarence Birdseye, an American inventor, developed the concept of flash freezing in 1942 when he was looking for a way to eat fresh vegetables during the winter. Flash freezing is a process whereby the food is subjected to extremely low temperature in just a few hours. In the case of vegetables, they are first washed and blanched prior to freezing. Blanching involves placing the vegetables in boiling water for several minutes to kill the harmful microorganisms.The process also helps preserve the color, texture, and flavor by deactivating enzymes. Enzyme activity speeds up the degradation of fruits and vegetables.

Blanching is generally not performed for fruits prior to flash freezing as the blanching temperature may adversely affect their quality. However, adding vitamin C or sugar to fruits prior to flash freezing helps slow down enzyme activity.

Because flash freezing reaches ultra low temperatures in a short period, only small ice crystals form. This reduces the damage to the cell membrane of the produce. And since the produce is frozen at its peak quality, the nutrients and minerals are retained and maintained. In some cases, produce that has been frozen can contain more vitamins and minerals as compared to fresh produce that has been transported for a long period, or displayed at the market or sitting in your kitchen prior to consumption.

In fact, this work studied vitamin retention between frozen and fresh fruits and vegetables. The study found no consistent differences between frozen and fresh. However, frozen blueberries, corn, and green beans contained more vitamin C than their fresh counterparts. Furthermore, frozen broccoli contained more riboflavin (B vitamin) than fresh.

CANNING INCREASES BIOAVAILABILITY OF SOME NUTRIENTS

Canning involves placing foods in jars and then heating them at a temperature that prevents the growth of harmful microorganisms. However, the temperature can also lead to losses in nutrients as the vitamins leech into the liquid. The same thing happens when we boil vegetables or fruits at home. Exposure to oxygen and light also affects nutrients negatively. But more is lost during processing that involves heat. This is especially true for fruits and vegetables rich in water-soluble vitamins and minerals. Vitamins C and B vitamins are particularly sensitive.

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But how much exactly is lost during canning though?

Well, the amount of nutrient loss is not that significantly different from that of produce not consumed immediately. Remember that a vegetable or fruit starts dying once removed from the mother plant. And in some instances, some canned foods contain more nutrients than fresh.

How?

The heating and cooking increase the bioavailability of some nutrients.

One good example of this is canned tomatoes, the most consumed vegetables in the United States. When canned, tomatoes can significantly increase its lycopene content. This work studied the effect of heat treatment on carotenoid (lycopene is a carotenoid) content of cherry tomatoes. Canned tomatoes increased its lycopene content two-folds. The canned tomatoes contained 11.60 mg/100 g of lycopene, whereas the raw tomatoes only contained 5.12 mg/100 g of lycopene. Lycopene is an antioxidant that helps reduce the risk of developing prostate cancer.

Cooking also have a similar positive effect in the heart-protecting carotenoid content in carrots, spinach, and cabbage.

The post Are Fresh Foods Superior To Canned And Frozen? appeared first on The Food Untold.

We freeze meat to preserve them for longer. The mechanism is very simple. The residual moisture, which bacteria need to grow, turns into ice. This effectively inhibits the growth of bacteria, and prevents foodborne illness. But how about the quality of the meat when you prepare it? Is is good? How is the taste? The texture?

If you are used to “flash freezing” meat at home, you better think it over. Industrial freezing is not the same as just chopping meat into smaller pieces, and then freezing them in your home freezer.

Here is why.

Industrial freezers can flash freeze meat efficiently

Like the name suggests, flash freezing (or blast freezing) is subjecting meat to an extremely low temperature quickly. The temperature is far below the freezing point of water at 32 °F (0 °C). A flash freezer (like the one above) must be able to maintain a temperature of meat at least -0.4 °F (-18°C) or lower. And an increase in temperature is only tolerable in short periods. You may want to read more on this with this document provided by the Food and Agriculture Organization (FAO).

Unlike home freezers, industrial ones use more power to make the temperature of food from around 158 °F (70 °C) down to 0.4 °F (-18°C) in just 240 minutes! This is possible by using powerful blower fans, which navigate cold air across the inside of the freezer.

Depending on the design, other freezers can quick-freeze foods in other ways.

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Why the rush though?

It is simple—we do not want large ice crystals.

When we freeze meat, the water inside crystallizes, like I mentioned. The thing is that freezing produces ice crystals, which is normal. But the longer the freezing takes, these sharp crystals become bigger. And that is not desirable.

What is wrong with large ice crystals?

Freezing naturally involves the formation of ice crystals. A longer freezing time makes the ice crystals larger. These are sharp enough to pierce and damaged the meat’s structure. And the meat loses water once the meat thawed. Obviously, this is not a good thing as the meat becomes less tender and juicy.

This is why home freezing of meat is not recommended. Unlike the ones used in commercial kitchens and cold storages, home freezers do not have the capability to produce enough power to quick-freeze meat efficiently.

Freezer burned meat

A phenomenon referred to as freezer burn, this occurs when the water froze, and migrated out of the meat to find itself in the coldest part of the freezer. It is apparent when the meat looks discolored, tough, and shriveled. Furthermore, the fats in the meat gradually oxidize, degrade and turn rancid. Freezer burned meat is totally safe to cook and eat. But it is not appetizing to consume anymore.

One way to combat this is by placing the meat in an airtight wrapper before freezing it. It helps by trapping the water molecules. Remember though that the water will eventually escape. So do not freeze meat for too long.

How long can you freeze meat?

Frozen meat is safe indefinitely. But longer freezing time may result in loss of quality. Particularly, it affects the taste and texture. The below table are the guidelines for freezer storage of meats, as provided by Foodsafety.gov. You may want to check out the whole list on their page.

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