Test lab helps optimize products' retort processing

Jack Mans, Plant Operations Editor

March 11, 2015

7 Min Read
Test lab helps optimize products' retort processing

A high-tech laboratory retort machine at the National Food Lab (NFL), Livermore, CA, is helping the world-renowned consulting and testing organization continue its efforts in shelf-life evaluations, pilot plant trials, food safety and quality assurance. 


Beyond the primary goal of ensuring 298460-rrrr1_retort_jpg.jpg

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product safety, retort process optimization helps minimize cycle time and improve finished product quality.

But how do you identify the best combination when there are so many variables, such as time, temperature, agitation and heating medium? To meet these requirements, the NFL has installed a Stretch 2402 multimode R&D retort from Allpax Products, a division of Pro Mach in its pilot plant. Using the Allpax system, the NFL can identify the optimal combination of processing parameters (agitation and heating media) that will result in the highest quality product and maximum process efficiency. 

Terry Berman, division manager at the NFL, says, "The NFL's new retort capability means faster time-to-market for new products and potentially better sterilization solutions for products already on the market. Companies can now use one pilot plant, not two or three as they had to do in the past, and have product preparation, multiple retort processes and control strategies at their fingertips."

Adam Reichert, Allpax process engineer/thermal processing specialist, says, "The NFL wanted to provide the most versatile retort testing service in the world and was the first Allpax customer to specify every Stretch 2402 mode available. They also requested a longer retort for greater capacity."


The Allpax Stretch 2402 at the NFL offers saturated steam, steam air overpressure, water immersion, water spray and water cascade processes in combination with seven easily changeable modular agitation modes: still, end-over-end, swinging, gentle-motion shaking (low-speed), The Shaka Process shaking (high-speed), hydrostatic simulation and axial rotation. The unit can handle cans, bottles, pouches, cups, trays, metals, glass, plastics, and double-seam film and foil closures.

Senior project leader Robert Kravets says, "Flexibility was a requirement for this lab retort. We never know what kind of products or containers that we will be testing. There were limitations on what we could do before we got the Allpax retort. Now, we are able to test many more possible operational parameters and achieve a better product."

This retort is equipped with the production version of the Allpax control software, which is 21 CFR Part 11 compliant for recipe editing, batch logs and security 298461-rrrr2_Robert_jpg.jpg

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functions. The Allen-Bradley PLC-based HMI from Rockwell Automation makes switching between sterilization processes fast and easy, creating an almost infinite number of processing possibilities as manufacturers look for optimum efficiency, quality and taste.


Testing pouches

During Packaging Digest's visit, NFL scientists were running tests on a low-acid vegetables with meat sauce product for a Fortune 50 food company. To run a test, pouches of product were placed into plastic trays, which were then stacked inside the retort. Thermocouples, which are supplied by Ecklund-Harrison Technologies Inc., were inserted into a number of the pouches, which were then placed in strategic locations inside the retort to monitor internal product temperature.

This particular test run consisted of 10 pouches each of three different flavor variations being processed in the gentle-motion shaking (low-speed) mode of operation. Further tests will encompass other flavor variations, other modes of operation, other operating temperature profiles and more. The number of tests required for a particular line of products can be extensive.

A mitigating factor is the experience of The NFL experts. Kravets says, "We've done literally hundreds of tests on every kind of product and container that you can imagine, so we have a good understanding of the types of tests required. We always have to keep in mind the type of operation that the production plant can use. It wouldn't make any sense to develop a process that the plant couldn't duplicate."


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The retort is equipped with the Allpax Monitor retort control system, which meets or exceeds the requirements of 21 CFR Part 11 including electronic data fingerprinting, audit trails and secure operator restrictions. The parameters for each recipe are configured for each processing step (such as come-up, cook and pressure cool) to control all valves automatically. Each processing step is defined by the time in the process step and the critical factor set-points. Cumulative product lethality is monitored in real time using a separate software.

Kravets says, "We can program this with all of the different operating parameters for every product, and then select the correct one for each test from the menu. The system also maintains historical archives, so we can look at past tests and compare the results." 


Trials on mac and cheese

The NFL recently executed a series of retort trials on a canned queso-style macaroni and cheese (penne pasta in a spicy cheese sauce with vegetables) in the Allpax Stretch 2402 R&D retort. 

Heat penetration data was collected during all trials and used to calculate process schedules, and the products were submitted for sensory evaluation. Results were then compared to determine the optimal processing parameters.

The NFL's product innovation team developed a recipe for the Queso-style macaroni and cheese, which was batched and packed into 15-oz (300 x 407) cans. 


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Cans were processed in the R&D retort using water spray and seven combinations of agitation and speed: still, end-over-end rotation (5, 10 and 15 revolutions per min), and gentle-motion at 30, 60 and 90 strokes/min. All of these processing modes are currently used for commercial production. 

Eight cans per trial were equipped with thermocouples and temperature data were collected. Samples were processed until the slowest heating can achieved minimum commercial sterility and then cooled below 130 deg F. 

Narrative sensory testing

Narrative descriptive analysis was used to provide in-depth descriptions of the product sensory characteristics, allowing a comparison of the sensory properties of multiple samples.


An NFL panel leader and three members of The NFL's trained descriptive panel independently evaluated each sample and described the major appearance, aroma, flavor and texture characteristics of the still-cook sample that was used as a reference. 

They then indicated the specific sensory attributes that differed in the variant samples and to what degree the variant samples differed from the reference sample in the specific attributes noted. In addition, they made note if a variant sample showed consumer relevant downsides compared to the reference sample. 298464-rrrr5_utilities_jpg.jpg

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The various agitation methods yielded large differences in processing time. Processing times also decreased as agitation speed increased. The total processing time (excluding come-up time) ranged from 129 minutes for the still-cook down to 48 minutes for gentle-motion (90 strokes/min).

Visual characteristics and flavor/texture characteristics of the various products were also evaluated. 

Different variables, different outcomes
Determining optimal processing parameters is not a straightforward task. In these trials, the two fastest processing methods each resulted in approximately a 60 percent total processing time reduction, but each had different sensory results. The end-over-end (15 rotations/min) showed only slight differences versus the reference sample, while the gentle-motion (90 strokes per min) showed noticeable consumer- relevant downsides. 

These results pertain only to these specific combinations of formula, packaging and processing. Changing any of these variables may result in different outcomes.


Allpax Products, a division of Pro Mach, 888-893.9277. www.allpax.com
Ecklund-Harrison Technologies Inc., 239-936-6032. www.ecklund-harrison.com
Rockwell Automation, 414-382-2000. www.rockwellautomation.com

About the Author(s)

Jack Mans

Plant Operations Editor

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