Retort Processing Shakes Up New Interest

From agitation to AGVs to software, this old-school manufacturing process continues to evolve.

By David Phillips, Plant Operations Editor

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Retorting is the old reliable of food processing — providing safe, effective shelf stability with fairly simple equipment and packaging. But that doesn't mean there is nothing new in the retort room. New packaging formats that have emerged in the past decade make retorting more desirable. In addition, the latest agitation processes have reduced cook times, making for both energy savings and less degradation of food quality.

Retort processing deserves its reputation as the old reliable food processing option, and that's not a bad rep to have. "Retorting is a proven safe technology," says Greg Jacob, general manager with Allpax Products, Covington, La.

Proven, but not stodgy, he adds. "It has actually been over 10 years that retorts have been successfully used to process pouches, plastic bowls and even paperboard composites. Plastics continue to evolve into a major player in packaging. This is one of the main reasons why today's processors gravitate toward multi-mode retorts."

Nor does one size fit all. Jeff Dahl, business manager-food processing systems in JBT FoodTech's Madera, Calif., office, notes his company makes retorts from pilot models to 1,800mm ones that are fed by automatic guided vehicles (AGVs). And this doesn't have to be a batch process. JBT's Rotary Pressure Sterilizer and Continuous Rotary Atmospheric Sterilizer "permit short-time, high-temperature cooking and rapid, efficient cooling in an automatic, continuous operation."

Multi-mode retorts, agitating units and sophisticated software to model and then document food sterilization make modern retorting a far cry from simple stove-top canning of domestic engineers of yesteryear.

Retort processing can be a batch or continuous process that provides in-container sterilization to low acid (pH greater than 4.6) food products to render them shelf stable, as opposed to refrigerated or frozen low acid products.

Batch retorting offers maximum flexibility related to products and containers since the retorts are recipe-driven for each cycle. That being said, batch No. 1 can be peas in a can, batch No. 2 can be sauce in a pouch and batch 3 can be a coffee beverage in a glass jar. This flexibility is offered with the simple change of a recipe versus other types of sterilization technology that would have defined container and product.

"With batch retorts, the manufacturer has an asset that can be used for present products. [But he also has] the ability to change products and containers as the market changes, using the same asset if planned properly," Jacob says. "Today's batch retorts can be configured to run multiple processes to afford the manufacturers maximum flexibility."

Glass jars and metal cans are the traditional packaging formats for retort, but as Jacob notes that has changed significantly in the past decade or so. Meal replacement beverages used prevalently in medical institutions are typically packaged in retortable plastic bottles for shelf stability. Retail products including juices and dairy based sports recovery beverages have followed suit. Pouches have become popular for a variety of food categories.

All this makes retort equipment more flexible than competing processing systems. Their ability to accept a variety of packaging types means that retorts can deal with present conditions (i.e., cans or glass), but also have a tool for the future (plastic semi-rigid). Jacob points to four areas where retort has evolved in recent years:

  • Jumbo-sized retorts now use automated material handling systems, including automatic guided vehicles, to keep up with very high line speeds on the filling and case packing ends
  • New agitation technologies reduce cycle times and can improve quality in retort products. 
  • Energy conservation techniques have been developed to recapture cooling water, take advantage of vented steam, etc., thereby saving energy.
  • Using advanced control system technology, retorts can now be "multi-mode," meaning that more than one commercially approved process can be run on the same retort and can be alternated batch to batch, giving the processor an asset that will offer maximum flexibility with products and containers in today's evolving markets.

"Retorts today are certainly much more 'green' than they were 10 years ago," Jacob says. "With sustainability objectives as a high priority for all of our products, we have developed methods to improve on energy usage," he says. "With retorts, it is BTUs in and BTUs out, so our opportunities come in shortening cycle times using agitation along with steam and water recapture and reuse." Recaptured hot water can be used for heating buildings, sanitation water, heat exchangers and other uses.

Agitation systems are evolving too. Gentle agitation systems like Allpax' Gentle Motion line have been in use for several years, but those introduced more recently, like the company's Shaka, provide additional agitation.

"Both take advantage of reciprocating agitation best suited for horizontally oriented containers like bowls and pouches," Jacob says. "Shaka is a very dramatic agitation style that shortens cycle times by as much as 90 percent. Gentle Motion is a much slower agitation that can save as much as 40 percent in cycle time. Both are available in R&D and production size retorts."

Almost as important as the equipment is the documentation that the food product has been safely sanitized. JBT FoodTech, formerly part of FMC Corp., offers the Log-Tec Process Management System, which controls every aspect of the sterilization process and generates records to meet both FDA and USDA requirements. "Log-Tec is complemented by our family of NumeriCAL thermal process modeling software," adds a spokesperson for the company.

JBT also opens the doors to its Thermal Process Laboratories and Pilot Plants in Madera, Calif., and Sint-Niklaas, Belgium (and two smaller ones in China and Brazil). The facilities provide such services as thermal process design and validation, temperature distribution studies and heat penetration measurements. JBT FoodTech is a recognized USDA and FDA process authority.

This article originally appeared in the January 2013 issue of Food Processing Magazine.

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