Continuous processing is more efficient than batch processing. Conduction heat transfer is more efficient than convection heat transfer. Spiral conveying is a more efficient use of space than straight line conveying. No secrets here. These are long-time, well-established, and well-used processing paradigms. So why hasn’t anyone combined all three?

The FPS Spiral Immersion System™ (the “SIS”) brings together the small footprint of spiral belting, the energy savings of conduction heat transfer and the labor savings of continuous processing. The SIS™ is basically a spiral conveyor in a tank of liquid, usually water or brine, that is designed to prevent the displacement of the product from the belt during processing. Developed by Intralox, experts in belting technology, FPS Food Process Solutions Corp, experts in spiral chillers and freezers and Steve Kelley, expert in immersion processing, the SIS is more energy efficient, uses less refrigeration and has a smaller footprint compared to traditional spiral freezers.

More Efficient Chilling and Freezing

It is well established that conduction heat transfer (heat transfer by direct contact) is significantly more efficient than convection heat transfer (heat transfer by air). The conduction heat transfer coefficient of water is 25 times faster than heat transfer coefficient of air. This is the driving force behind the increase in efficiency of the SIS™ compared to chilling or freezing in air. 

Water is easier to move around than air and water or brine can move at less than 10% of the speed that air needs to move to efficiently transfer away heat. So, the SIS only needs a 10 to 20 hp pump compared to 100 to 200 hp of fans for an air-based system. This increase in efficiency allows the SIS™ to be up to 50% of the size of an air-based chiller or freezer with the same product throughput. The result is that the SIS™ uses 80% less electricity, 30% less refrigeration tonnage and is 50% of the footprint of a similar throughput air spiral freezer. 

There are other advantages to the faster chilling and freezing provided by immersion processing. In food processing, the critical zone of water crystallization is from -1C to -8C. This is when the water within the cellular structure of the food is crystalized. The speed with which the temperature drops through the critical zone of water crystallization from -1C to -8C determines the size of the water crystals. The faster the temperature descent, the smaller the crystals. The larger the crystals, the more damage there is to the cellular tissue of the food product. The faster that you can take the food product through the critical zone of crystallization, the smaller the water crystals in the cells of the food product and the lower the degree of cellular rupture. The lower the degree of cellular rupture, the greater the preservation of the cellular tissue and the greater the preservation of the natural color, texture, flavor and quality of the food product.

Using brine as cold as -50F, the SIS™ freezes food products 20 to 70% faster than freezing in air. That equates to significantly less cellular disruption and substantially better retention of the natural color, texture, flavor and quality. Freezing with the SIS™ enhances the visual, textual, nutritional and flavor qualities of the food being processed.

The SIS™ instantly freezes the surface of the food product (25 times faster than in air). This creates an instant solid crust that prevents the osmotic transfer of water out of the cellular tissue and preserves an excellent natural and uniform appearance. There is minimal dehydration, and the mass loss is close to zero, while in air freezing the moisture losses are 2-3% or higher.

Safer Food and Longer Shelf Life

The “danger zone” in food processing operations is between 40 and 140F where bacteria growth is exponentially higher. Since most foods are either harvested or processed at a temperature in the danger zone and are stored at a temperature below the danger zone, the key to food safety and shelf life is to get the product out of the danger zone (40 to 140F) and into the safe storage zone (under 40F) as quickly as possible. 

The speed at which a product can be cooled to below 40F is directly proportional to the number of bacteria present in the food when it goes to storage; therefore the speed at which a product can be cooled to below 40F is directly proportional to food safety and shelf life.  Because immersion chilling is up to 70% faster than air chilling, immersion chilling results in a lower bacterium count in the food product and therefore a longer shelf life and safer food products than air chilling.

Sous Vide

The advantages of immersion processing apply to cooking and pasteurizing as well as chilling and freezing. The SIS™ operates in a temperature range from -50F to 210F. There are 3 related hot water applications for the SIS: cook/chill, pasteurize/chill and sous vide. They all involve heating the product in one SIS™ followed by chilling the product in another SIS™. Cook/chill is obvious, cooking the product in a bag followed by chilling in a separate SIS™. Pasteurization is usually something less than cooking and can mean heating to a target temp at the core of the food product or only a surface pasteurization. Both are followed by a chill step. The concept of sous vide means a slow cook. The benefits of the 3 x cook / chill functions are the same:

  • Low to zero yield loss as all the moisture is trapped inside the bag with the food. This compares to 2 to 5% yield loss for product cooked unpackaged in air.
  • Better quality food with a more tender texture, more flavor and better nutrient retention because all the moisture and nutrients stay in the bag and most are resorbed by the food when it cools.
  • Longer shelf life as the food reaches a bacterium kill step during heating in the bag.
    • Sometimes products are fully cooked prior to packaging, then packaged and then cooked again inside the bag to kill all the bacteria introduced during packaging.
    • Alternatively, the products are partly cooked prior to packaging and then “finish cooked” inside the package to establish the bacteria kill step.
    • Pasteurization can be a post packaging cook process or a separate step after cooking is completed. Pasteurization can heat to the core of the product or just the surface. The surface of the food product between the packaging and the food is the primary location of bacteria. 
    • Customers advise the shelf life of food products can be extended by 30 to 90 days or more.
    • Convenience. Sous vide and cook/chill products are ready to go. Just heat and serve. In the restaurant and institutional trade, you do not have to worry about the quality of your staff to handle and cook the food correctly. 

Reduce Labor Costs

Moisture in the air in a regular spiral freezer condenses on the freezer coils into snow and ice. Eventually this buildup of snow and ice retards heat transfer, and the freezer must be shut down and defrosted. This sacrifices production time and is a major labor cost. In addition, the spiral freezer must be cleaned a few times a week. Again, a major labor cost. The SIS™ uses a salt brine that is naturally anti-pathogenic and there is no exposed coil or other surface for the buildup of frost and ice from condensation. The result is that the SIS never needs to be shut down for defrosting and rarely needs to be shut down for cleaning. A significant increase in processing time and a huge reduction in labor cost.

One of the biggest advantages of the SIS™ is the continuous flow process. Most cook / chill or sous vide water bath processing arrangements are batch or semi-batch processes where food products are loaded into baskets and then placed in a tank filled with hot water. At the end of the cook time the water is dumped, and the tank is filled with cold water or the baskets are hoisted out and transferred to a cold-water tank. At the end of the process the baskets must be unloaded. This all requires a lot of labor. The SIS™ is a continuous conveyor belt-based process from start to finish. Products emerge from the bagger or vacuum sealer onto a conveyor belt and are fed directly into the SIS™ cooker. The products spiral through the SIS cooker and exit into the SIS chiller with little or no human interface. Fully automatic and continuous. The result is huge savings in labor costs.

Game-Changing Technology

Until now, water bath processing has been problematic because almost all food products float, are difficult to control when underwater, and they escape the belt path and get damaged. With the patented (pending) technology of the SIS and Intralox’s self-stacking belt, even floating food products are secured within the belt stack and the food product is treated very gently with no product or packaging damage. The belt above, below and on both sides of the product are moving along at the same speed as the product so there is no opportunity for bumping, rubbing or abrasion that could damage the product. This revolutionary technology allows the SIS™ to take advantage of the superior performance of water and brine immersion processing: energy savings, labor savings, higher yields, longer shelf life, safer and better-quality food products.

Steve KelleySteve Kelley developed the Spiral Immersion System. Kelley is a trained professional, MBA, CPA, LLB, and a dynamic business builder with a proven eye for innovation and a history of success delivering high-quality solutions to the food processing industry. Prior to joining FPS Food Process Solutions, Kelley was the President and CEO of Charlottetown Metal Products Ltd. (CMP).