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USDA 

 

 

THERMAL PROCESSING 

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Module 10. Continuous Rotary 

(Agitating) Retorts 

Thermal Processing for Meat and Poultry 

Products Training 

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Introduction 

 Uses steam as the heating medium 

 Continuous container handling 

 Intermittent product agitation 

 At least two shells 

 Configuration will vary 

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OVERHEAD 

fEEl> ELEVATOR 

PRESS. COOKER 

• 

A MtJS. OR PRESS. 

COOl.fR 

TWO SHELL LINE ARIMNGEMENT 

ATMOS. COOLER 

____ ....,..,, 11 t,,II --

• 

PRESS., 

COOLER 

'TH~f,E SKBU. llNE ARRANGEMENT 

PRESS. COOKER 

I cvP FEEt> 

• 

fl'~ESS. 

COOLB! 

ATMOS. ·COO.Lf-R 

THREE SHEU. LINE ARitiiNGEMEN 

• 

Typical Arrangements of Continuous Rotary 

Retorts 

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discharge 

valve 

reel 

transfer valve 

Inlet valve 

shell 

spiral T 

steps 4 
STE:RILMATIC 

INFEEO 

DISCH.t;FIGE 

 

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CANS IN CARRIER STEPS 

ARE FORCED THROUGH 

RETORT BY SPIRAL T’S 

WELDED TO RETORT 

SHELL IN 

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End View of Continuous Rotary Retort 

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Retort Description 

 Rotating reel with steps to hold containers 

 Spiral T attached to shell to move containers 

through 

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Spiral T 

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The Reel 

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Number of Reel Steps for Can Diameters 

Can Size 

Steps Per Turn of 

Reel 

211 56 

300-303 47 

307-401 42 

404 35 

603 24 

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- ___ - .~ I 

.J~ 

~ 

....... 

~~ · 

CUP FEED DIRECT - (Wl,Il:LEREE RO T9 FEEiD VALVE LLER FEED.ER) 

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In-Feed 

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Transfer Valve 

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Retort Description 

 Advantages: 

• Short process time 

• Continuous input 

 Disadvantages: 

• Extra critical factors 

• Container size limits 

• Larger investment than a still steam retort 

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Retort Installation/Operation - Steam Inlet 

 Multiple feeder lines to trough at bottom of 

shell 

 Must be large enough for proper operation 

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Retort Operation - Condensate Removal 

 Required to remove it 

 Condensate interferes with container rotation 

 May reduce product agitation leading to under 

processing 

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Retort Operation - Condensate Removal 

Must: 

 Open drain for sufficient time during venting 

 Provide for continuous or intermittent removal 

 Have bleeder arranged for observation 

 Be observed and recorded frequently 

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Retort Operation - Pressure Cooling 

 May be needed to prevent container distortion 

 Cooler pressure should be slightly below 

cooker pressure so water does not enter 

cooker 

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Rotational Speed and Process Timing 

 Reel speed must be set as stated in process 

schedule before containers enter retort 

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Rotational Speed 

 Determines process time 

 Affects product agitation 

 Faster than calculated time results in shorter 

process time 

 Slower than required minimum speed reduces 

agitation 

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Rotational Speed 

The rotational speed must be: 

 Specified by process authority in the process 

schedule 

 Checked and adjusted when the retort is 

brought up to temperature and determined 

and recorded at intervals not to exceed 4 

hours 

Notice to prevent unauthorized changes 

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Ir\ 0 

FREE ~ CONTAINER CARRIED 

ROTATION SLIDING BY REEL 

ROTATION 

Rotational Speed 

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Intermittent Agitation 

Process Considerations: 

 Intermittent agitation provides more rapid 

heating and cooling when compared to no 

agitating 

 Container rotation is divided into carried, 

sliding and free phases 

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Intermittent Agitation 

 Product and headspace bubble mix during 

rotation 

 Solid pack items like beef stew and chili do 

not benefit from agitation 

 Brine-packed items, soups and sauces may 

benefit by faster heating and shorter 

processes 

 Dependent on headspace, consistency, reel 

speed and fill-in weight 

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Important Critical Factors 

 Condensate build-up 

 Headspace 

 Consistency 

 Reel speed 

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Headspace 

 Area not occupied by product 

 Critical factor for agitation 

 Net or gross headspace 

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Consistency 

 Measure of product thickness 

 Thicker product may reduce agitation 

 Measure consistency at location specified in 

the process schedule and in accordance with 

a written procedure, e.g., at the cooking kettle 

of filler at 160 F or higher temperature 

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Reel Speed 

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27 RETORT REEL TIMING 
 

 

 

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Reel Speed 

 For reel speed calculation you need: 

• Process time 

• Total container capacity of processing shells 

• Number of reel steps 

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Reel Speed 

Can Size 

Steps Per Turn of 

Reel 

211 56 

300-303 47 

307-401 42 

404 35 

603 24 

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Reel Speed 

Calculations 

• Reel Speed 

RPM = capacity/reel steps x process time 

• Cans Per Minute 

CPM = capacity/process time 

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Reel Speed 

Seconds for 10 Revolutions of Reel = 

10 revs x 60 sec/min x reel steps x process time 

Shell Capacity 

10 x 60 sec/min x 47 x 14 min = 39.48 secs 

10, 000 (303 diameter) 

10 x 60 sec/min x 24 x 10 min = 28.8 secs. 

5,000 (603 diameter) 

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Initial Temperature (IT) 

 Critical heating parameter specified in the 

process schedule 

 Measured on containers taken from line prior 

to inlet valve 

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Recordkeeping Requirements 

 Critical factors and IT must be measured and 

recorded in accordance with the method and 

frequency in the written procedure 

 Must include reel speed checks 

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Handling Process Deviations 

Retort Jam or Reel Breakdown In-Process: 

 Must reprocess, repack and reprocess, or 

destroy all containers 

 May use emergency still process before 

retort is cooled 

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Handling Process Deviations 

Emergency Still Process: 

 Obtained from a processing authority, if not 

process must be reviewed by a processing 

authority 

 Must reprocess, repack and reprocess or 

destroy containers in inlet and transfer valves 

 Records must be kept of actions including the 

time the retort stopped and the time retort was 

used for the still process 

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Handling Process Deviations 

Alternative Procedures in Case of Temperature 

Drop in the Retort: 

 < 10°F drop 

• Stop reel and use emergency still process on file 

• Stop container entry and use emergency 

agitating process on file 

• Have process evaluated by processing authority 

• Empty retort and reprocess, repack and 

reprocess, or destroy all containers 36 
 

 

 

 

 

 

 

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Handling Process Deviations 

Alternative Procedures in Case of Temperature 

Drop in the Retort: 

 ≥ 10°F drop 

• Stop reel and use emergency still process on file 

• Have process evaluated by processing authority 

• Empty retort and reprocess, repack and 

reprocess, or destroy all containers 

• Records must be kept of actions 

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Twin spira1

ls (Tr11ple available) 

Dedicated 1:ine system for high speeds, or separated multiple products/can sizes. In addition 

delicate products can be run at high speed with 

hatf the agitatlon of a single sp'iral. 

 

 

 

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Different can sizes or products can be introduced into 

custom reels. Spirals can be custom designed to handle 

different length cans or can be designed to provide 

39 different thermal process times to different cans. 
Questions? 

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Questions?

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