Variable retention time freezers offer advantages over other technologies

by Thomas Jensen

A solution at the end of the line

This article was featured in Eurofish Magazine 6 2022.

The world has become a very uncertain place in which to live and operate. Even before the difficulties imposed by COVID-19, Brexit, and now the war in Ukraine, energy costs were rising, labour availability was precarious, and production mistakes were devastating previously profitable companies.

Food processors, whether they want to or not, must pursue strategic technology investments to deliver on their business objectives. Whether those objectives include streamlining processes and increasing efficiency across the plant, positioning themselves as a company with societal purpose, or reimagining their business to lead the direction of their industry, technology now plays a pivotal role. So, why do many fish companies still rely on aged and outdated ­technologies?

The reason behind deploying technology is critical

Evolving your processes in a unified way can be exciting, but knowing where to start can be overwhelming. Major fish processors are looking to innovate and transform their operations to create best-in-class production facilities. And rightly so, but it’s not always straightforward. The market and the fish industry as a whole are at an inflection point. If you don’t spend time, energy, and investment to realise the full benefits of technology, you risk falling behind and will likely never catch up. Technology offers countless benefits, but it provides no real long-term value without clearly identifying the why of using it. Labour and skills shortages in the fish processing industry are the why. They are now a day-to-day issue and often result in highly inefficient operations. Difficulties in attracting and retaining labour also increase business risk, including the risk of lost contracts and reduced market share.

Air blast freezers are no longer the most advanced

The one area that many fish processors ignore during their ­technology review is the end-of-line freezing. Air blast freezers are still seen as the main technology. In most operations, fish is batch frozen in boxes that are loaded manually into a freezing system. Blast freezers require double handling, and achieving uniform freezing conditions is difficult. They also require large areas of real estate, both in the freezer and externally in marshalling areas.


Some fish processors opt to use plate freezers, which are contact freezers where a refrigerant is passed through hollow metal horizontal or vertical plates that are pressed on either side of the box being frozen. Plate freezers are best suited to limited, regularly shaped products with a maximum thickness of 50–70 mm. Air spaces in packaging and fouling of the plates have significant effects on cooling time. Although modern plate freezers appear to be fast and energy efficient, most still require a substantial labour input and often burn the product when freezer plates make close contact with the fish. And they have high peak electrical loads.

So, you ask, is there a better way to eliminate labour, reduce energy costs, provide certainty in the freezing process, and automate warehousing? Like many great innovations, proven technologies in one industry can bring transformational change when applied in another industry.

Better product finish, reduced freezing times, automated palletising, and more

Variable retention time (VRT) freezers and chillers were first introduced just over 40 years ago. Initially, they were applied to automating cheese cooling but quickly found a use in meat and chicken processing. The major advantage of a VRT is that it can freeze several different products, each with different freezing times and different size packages using a programmable computer that controls its operation. Variable retention time freezers are energy efficient with the ability to reduce freezing times by up to 200% over blast freezers. Their controlled cooling curve also assures a ­better product finish. Internal product tracking provides the possibility to isolate and quarantine product. 

When linked directly to the fish processing lines on the infeed side and to an automated palletising line on the outfeed, virtually no labour is required from packing all the way to the loading dock. With the right dedicated SCADA system, you have total, real-time visibility of processing, stock control, and shipping. Energy consumption is generally as low as 50% less than a similar blast freezer installation, and VRTs don’t have the electrical peak load requirement of a plate freezer. Variable retention time freezers can be designed to process 4–40 tonnes per hour and hold more than 400 tonnes of fish, all within a floor space of 1,000 sq. metres. With automated infeeds, outfeeds, and palletising, there is virtually no need for forklifts, with a consequential reduction in the risk of injury and ­damage to the building.

Overall, VRTs provide lasting benefits for your businesses, such as reduced processing times, costs, and error rates, increased throughput and quality, and better inventory management and sales projections.

For more information, contact:
John Magill
Executive Director
Power Food Technology Ltd
Site E1, Clane Business Park
Clane, Co. Kildare,
Ireland W91 C2H5

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