Freezing is a food preservation method that has been used for thousands of years. In the past, the method was to surround food with blocks of freshly cut ice to keep the food’s core temperature below the freezing point of water. However, today’s frozen food technologies now encompass numerous types of equipment and methods to preserve food.
Flash freezing is one of the most common methods used in food preservation today. During the 1920s Clarence Birdseye discovered the benefits of freezing fish, noting that lower temperatures accelerated the freezing process and made the fish more palatable. This discovery, in turn, suggested that food could be stored for longer. In 1925, Birdseye invented a device that used a pressurized brine and water solution to rapidly reeze vegetables for transport. This technology allowed producers to sell their frozen products all across the country.
To this day, flash freezing has remained a popular method of preserving foods for transport and long-term storage. This century-old, safe, and cost-effective method is being refined constantly. In this article, we will be looking at some of the most common frozen food processing equipment in the industry today.
Main Equipment Considerations for Frozen Foods
Today’s freezing equipment can generally be divided into two principal groups:
- Those integrated into the processing line for continual flow.
- Those operating in batches.
Depending on the heat-transfer method, freezing equipment can also be classified into three main groups:
- Air-Blast Freezers – Simply use moving, frigid air to cool the food. These are the most common freezers and are available in many different designs.
- Contact Freezers – Conduction is the main method of heat transfer in contact freezers. The food is frozen by bringing it in contact with one or more extremely cold surfaces or immersion in a cold liquid.
- Cryogenic Freezers – This technology uses liquefied gases, such as nitrogen or carbon dioxide, to produce extremely cold temperatures.
Depending on necessity, there may be combinations of these three heat-transfer methods used in special designs.
In addition, freezing equipment can also be categorized into two main groups based on the frozen food product. These include:
- Individually Quick-Frozen (IQF) Products – IQFs are food products where each piece of food is frozen separately prior to packaging. Common examples include fruits (i.e., blueberries or strawberries), vegetables (i.e., peas, corn, green beans), seafood (i.e., scallops or shrimp), or poultry (i.e., individual chicken breasts). Even whole poultry products, like frozen turkeys, are processed under the IQF method.
- Packaged Products – These are typically bulk frozen foods that are packaged before freezing.
While all of these freezing methods are used in the frozen food processing industry, the systems preferable for high production rates are those that are integrated with packaging operations to provide a continuous flow of product. A piece of comprehensive freezing equipment needs to be designed to accommodate all the stages of the freezing process, optimizing the entire system as a whole. It also needs to be hygienically designed to comply with all safety and sanitation standards, ensure product quality and shelf life, and minimize product losses. Freezing equipment should be reliable and easy to operate, and require minimal maintenance to provide a cost-efficient freezing process.
Below, we’ll be providing a short rundown of the technologies and equipment used in the frozen food industry.
Food Freezing Equipment
As we previously discussed, freezing equipment can be classified into three broad categories based on the heat transfer method. The categories can be further divided as follows:
- Sharp Freezers – Also known as blast rooms, sharp freezers are cold storage rooms. There usually isn’t any forced airflow, resulting in a slow freezing rate. This equipment is typically used for bulk products, such as beef quarters, and not on processed foods.
- Tunnel Freezers – Refrigerated air is circulated over the product that’s placed on trays or special spacers. These either stand in or are passed through the tunnel in racks or trolleys.
- Belt Freezers – Single-, multi-, or spiral-belt freezer systems typically use a vertical airflow, forcing cold air through a product layer that’s evenly distributed over the entire belt area. This creates ample contact with all product particles. Of the three models, the spiral belt freezer offers the most flexibility in regard to the product range handled and maximizes the belt surface area in a given floor space. Meat patties, bakery goods, fish cakes, and filets are commonly processed in these systems. They can either be frozen raw or prepared, packaged or unpackaged.
- Fluidized-Bed Freezers – Fluidization occurs when individual food particles of relatively uniform shapes and size (i.e., peas) are subject to an upward airstream. After a certain air velocity, these particles will float in the air stream and separate from one another, allowing for more uniform freezing.
- Immersion Freezers – These consist of a tank of a cooling solution, such as salt, sugar, or alcohol and water. The product is immersed in this brine or is spayed while being conveyed. Turkeys or other poultry are typically frozen with this method.
- Plate Freezers – Either vertical or horizontal, manual or automatic, plate freezers sandwich the product between two metal plates for rapid heat transfer.
- Band Freezers – These are used to freeze thin product layers. The product is formed and frozen between two endless stainless steel bands, resulting in a frozen mat. Typical products include fruit pulps, egg yolks, sauces, chopped spinach puree, or liquid food such as soups.
Some freezing processes require a cryogenic fluid, either liquid nitrogen or carbon dioxide, to achieve quick, low-temperature freezing. This is particularly useful for small-scale operations in the early stages of product development. Cryogenic freezing is also used as a pre freezer for quick crust freezing for wet, sticky, or otherwise sensitive products that can then be handled by either airflow or contact freezers.
Frozen Food Packaging Technology
Depending on their moisture content, most frozen foods can expand by as much as 9%. As such, the frozen food packaging material needs to accommodate for these changes. In addition, the type of packaging chosen needs to:
- Withstand freezing temperatures of -40°F.
- Have a food packaging design that offers a good visual appeal.
- Sustain the sealing, freezing, storage, and transportation processes, as well as, in some cases, cooking pressure.
Below are some of the commonly-used materials used in the packaging process:
- Polyethylene (PE) Film – PE films can withstand low temperatures of -40°F, have good mechanical strength, and are puncture resistant.
- PE Derivatives – Different types of plastics can be used for frozen food packaging, such as shrink wraps, rigid materials, flexible plastics, and single-use packaging.
- Polyethylene Terephthalate (PET) – This material can withstand abrupt temperature changes and is generally used in microwavable or boil-in-the-bag products.
- Cardboard and Laminated Paper – Commonly used in fast-moving consumer goods (FMCGs), these packages have a limited shelf life after taking the product out of the freezer.
- Tin Cans – These were the traditional frozen food packaging material but are less cost-efficient when compared to the alternatives.
- Aluminum Foil Laminates – These tend to offer the best results in terms of water transmission, oxygen permeability, thermal and mechanical stability, and sealing quality.
Maintaining proper hygiene during the frozen foods packaging process is of the utmost importance. Even if freezing stifles microbial growth, it doesn’t eliminate it completely. And after thawing, microbial growth will pick up again. Frozen food manufacturers have several options for cleaning within the packaging line. Below are some of the most common:
- Dry Wipedown – This process involves cleaning the product and packaging with a microfiber cloth at room temperature.
- Low-Pressure Cleaning – Also known as soft-wash, this process involves low-pressure nozzles that spray distilled water or other solutions to wash off packaging and product surfaces.
- High-Pressure Cleaning – Generally, high-pressure cleaning for frozen food packaging equipment includes spray nozzles, air-dryers, and a hot/cold water setting.
Frozen Food Packaging Sealing Technology
A good sealing will ensure the overall safety and quality of the end product by protecting it from the external environment. Depending on the type of packaging film, there are several methods and packaging machines available:
- Direct Heat Sealing – This system can be used on a wide range of plastic packaging materials, particularly thicker ones like polypropylene.
- Impulse Heat Sealing – This system applies an electrical impulse in a piece of wire that’s heated and cooled. Impulse heat sealing is a more cost-effective alternative to direct heat sealing.
- VFFS Systems – VFFS packaging implies vertical forming, filling, and sealing technology, which is a packaging system of filling and sealing the product within the same production line.
- Zip-Locks – This type of sealing technology is gaining popularity in the frozen food market because of the increased convenience and overall quality and visual appeal of the packaging. They are often used in combination with a heat sealing method.
Frozen Food Conveyor Systems
Regardless of the freezing or packaging equipment, frozen food manufacturers need to maintain their food safety and food quality standards throughout the entirety of the process. To do so, they need a conveyor system that will not only guarantee this high level of security but also one that will minimize or even eliminate any product loss during frozen food production and processing.
Cablevey’s Frozen Food Conveyor Systems are suitable to move all sorts of food batch ingredients and finished products in a safe, gentle, and sanitary manner, no matter the material. These highly flexible systems can be engineered to service any part of the production process from mixing, pretreatment, freezing, and packaging, and 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 different components to cover any facility layout and conveyor movement needed.
In most frozen food applications, bucket elevators and/or open conveyors such as belts can often result in significant product spillage and warming, which can be a serious quality and efficiency concern. With cable, disc and tube conveyors, however, these are no longer an issue as the product travels through an enclosed environment. Utilizing clear tubing can eliminate the appearance of black specks occurring on the product, which many companies have noticed while using other types of conveyors. Cablevey’s Conveyor Systems are able to minimize this problem by using Clear Tubing and there is an additional benefit because of their ability to be cleaned-in-place.