There are hundreds of new frozen food items introduced onto the market every year. Some frozen foods may be gourmet, some gluten-free, while others may be less specialized. Consequently, there are entire aisles in grocery stores completely dedicated to frozen foods. In 2010, for instance, during the so-called Great Recession, frozen food sales grew by 3.1%. By 2025, the global frozen food market is expected to reach $376.95 billion at a compound annual growth rate (CAGR) of 4.3%.
How Frozen Food Was Invented
Obviously, frozen food has existed for millennia in climates where food could be naturally frozen. In China, for instance, people were keeping foods preserved in ice cellars as early as 1000 BC. The reason for this is that freezing is an excellent and cost-effective method of preserving food. However, it was not until the 1920s that Clarence Birdseye, who is credited with inventing the quick freezing method, gave us the types of frozen foods we know today.
While he lived and worked in Labrador, NF, Canada, Birdseye realized that the fish he and the Inuit locals were catching would almost immediately freeze as they were pulling them from the water. To Birdseye’s delight, he also noticed that the fish remained delicious even after thawing several months later. He then theorized that if food can be frozen quickly enough, it will maintain similar levels of taste and texture as when it was fresh.
Birdseye developed two methods of quick freezing foods. Both methods employed the innovative measure of packaging the food beforehand. In the first method, the package is held between two metal belts chilled at -40°F to -45°F with a calcium chloride solution. The second, and more common technique, is to have the packaged food under pressure between two hollow metal plates that are chilled to -25°F through evaporation of ammonia. By using this method, freezing meat to 0°F took around 90 minutes, while freezing fruits and vegetables took about 30 minutes. In total, Birdseye received a whopping 168 patents related to his quick freezing method. Patents included everything from packaging materials, storage, and transportation.
Since then, the technology of frozen food and methods of food freezing preservation has advanced to include even healthier options and eco-friendlier packaging, allowing foods to remain fresher and more nutritious over longer periods of time. Freezing is among the easiest, most convenient, and the least time-consuming methods of food preservation. There are, however, several types of foods that are trickier to flash freeze effectively, like produce with high water content, several cooked starchy foods (cooked rice and noodles), and some cream-based items.
In this article, we’ll be discussing food freezing basics.
What Factors Affect Food Quality
Importantly, the condition of the food at the moment of freezing will determine the quality of the frozen food. In other words, frozen food’s quality cannot be any better than it was before freezing. Also, freezing does not sterilize foods as canning does. The preservation effects of freezing are only limited to the slowing down microorganism growth and chemical changes. Below are some of the most common factors that will influence frozen food quality.
- Enzymes – All fresh produce contains enzymes that help the fruit or vegetable ripen and mature. Freezing vegetables and fruits slows but does not completely stop enzyme action. If not properly deactivated, these enzymes can affect color, flavor, texture, and nutrient loss during storage. Freezing, heating, or introducing certain chemical compounds can control enzyme action. Freezing will slow down enzyme activity in meat and fruits enough that little to no further treatment is needed. Fruits and vegetables require blanching to deactivate the enzymes in. The blanching process is simply a short scalding in boiling water or steam.
- Microorganisms – Freezing also stops microorganism growth that can result in food spoilage and illness. Nevertheless, the freezing process will not destroy the microorganisms, and they will begin multiplying once the food is thawed and left at room temperature.
- Air – If improperly packaged, oxygen in the air can change flavors and colors.
- Ice Crystals – Before flash freezing, food was frozen slowly. As a consequence, large ice crystals had time to form inside the food. And when an ice crystal punctured and ruptured the cell membrane, all the water inside the cell would leak out during thawing, altering both the food’s flavor and texture. The speed of flash freezing prevents the formation of large ice crystals that would cause degradation.
- Fluctuating Temperatures – Maintaining a constant freezer temperature of 0 degrees Fahrenheit or below will ensure top quality. As the temperature rises, the storage life of frozen foods decreases. As an example, frozen beans when kept at 0°F have a shelf life of one year; when kept at 10°F, three months; and when kept at 30°F, only three weeks. Fluctuating freezing temperatures can also cause ice crystal growth and moisture evaporation.
- Moisture Evaporation – When food is improperly protected, it may lose moisture, flavor, color, and texture. Ice crystal evaporation can also happen on the surface of the food, leading to freezer burn. This is a dry, brownish, and tough area that is safe to eat, but is not desirable.
Prior Food Processing and Pretreatments
As previously mentioned, the quality level of each food item prior to freezing is a major factor in the overall success of the freezing process. Therefore, the use of high-quality materials based on food standards and grades needs to be maintained in order to get similarly high-quality frozen products. These food standards and grades involve the freshness and freezing sustainability of the product, soil nutrients for plant-based foods, dietary factors for animal-based foods, and the harvesting and slaughtering methods used.
In addition, the processing methods used before the freezing process also need to be taken into consideration. These may include blanching, cooking, chilling, or the addition of antioxidants. Additional methods must also be used to ensure the elimination of pathogenic organisms, particularly when it comes to frozen poultry, since freezing reduces, but does not eliminate, microbiological activity.
- Plate Freezing – In this method, the product is sandwiched between two metal plates with pressure, usually applied for adequate contact. This technique is only used for products that come in regular shapes or blocks.
- Immersion Freezing – This method uses a low-temperature, brine-like solution, typically of sodium chloride, sugar solutions, alcohol solutions, or glycol and glycerol solutions, in which the product is submerged. Freezing occurs through direct heat exchange. The solutes used need to be safe for the product’s taste, color, flavor, and healthfulness. Air-Blast Freezing – Cold air is circulated at relatively high speeds around the product. The air velocity needs to be around 16 ft/s to generate the most cost-effective heat transfer rate. There are several equipment arrangements used to accomplish this:
- Fluidized Bed Freezing
- Belt Freezing
- Spiral Freezing
- Tunnel Freezing
- Cryogenic Freezing – This technique utilizes liquefied gases, such as liquid nitrogen or liquid carbon dioxide, which are placed in direct contact with the product. Foods will be exposed to a temperature of -76°F. Though it has a low capital cost and provides a high degree of flexibility in terms of food-type compatibility, this method requires a high degree of control to achieve consistent quality.
Packaging, Storage, and Display
The packaging, storage, and display stages will also affect the overall frozen food quality. The loss in frozen food quality is gradual, cumulative, and irreversible. For optimum quality to be maintained, every stage of processing, packaging, storage, and display needs to be addressed. All throughout this distribution process, the product needs to be maintained at a maximum temperature of 0°F. Also, the packaging needs to fulfill several criteria:
- Be attractive to the customer.
- Protect the product from external contamination, permeable gases, and moisture transfer.
- Allow for rapid and efficient freezing.
- Easy handling.
- Be cost-effective.
It was found that heavy-duty aluminum foil laminated packages offer the best results due to their low levels of water vapor transmission, oxygen permeability, light transparency, their thermal and mechanical stability, and quality of sealing.
The Cablevey Frozen Food Conveyor Systems
Cablevey’s Frozen Food Conveyor Systems are suitable to move all sorts of food batch ingredients and finished products in a gentle and sanitary manner. These systems can be engineered to service any part of the production process from mixing, pretreatment, freezing, and packaging. Being modular cable and tube conveyor systems, they can be used in a wide range of applications. Cablevey’s frozen food conveyor systems come in different sizes and offer a full range of optional components to handle any facility layout and frozen food conveyor movement needed.