THERMAL PROCESSING 

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Module 8. Steam, Batch, Still 

Retorts 

Thermal Processing for Meat and Poultry 

Products Training 

1 
 

Advantages of Steam 

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 Excellent Medium for Heat 

Transfer 

 Temperature Easily 

Regulated 

 Pressure Can Counterbalance Internal Can 

Pressure 

 Easy to Produce and Stored 

for Instant Use 

2 
 

Description of the Retort 

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 Pressure Vessel 

 Batch-type 

 Non-agitating 

 Vertical or horizontal 

 With or without crates 

3 
 

 

 

Construction 

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 Boiler plate 

 Riveted or welded 

 Doors or lids 

 Lugs or locks 

4 
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Installation and Operation 

 Adequate steam supply 

 Adequate water supply 

 Proper venting 

5 
RETORT HOOK-UP AND SPECIFIC OPERATING INSTRUCTIONS 

VERTICAL RETORTS - Simple Process Without Pressure Cooling 

O e 

0 0 

0 

0 0 

FIGURE l 

COLOR LEGEND 

- -Steam 

-Water 

- - Drain, Overflow 

-Vents, Bleeders 

- - Air 

- Safety Valves, Pressure 

Relief Valves 

MANUAL VALVES 

® - Globe 

[8j - Gale 

1. Steam Inlet 

2. Steam Control Valve 

3. By-pass 

4. Air, Instrument 

5. Filter 

6. Pressure Regulator 

7. Drain 

8. Water Inlet 

9. Steam Spreader 

10. ~ket SUpRQrtS 

12. Bleeders 

13. Thermometer 

14. Pressure Gauge 

15. Safety' Valve 

16. Overflow 

17. Vent 

18. Control, Steam 

19. Control Element 

Vertical Retort 

6 

THERMAL PROCESSING 

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HORIZONTAL RETORTS Pressure Cooling Under Air Pressure-Venting Through Outside Manifold 

0 

FIGURE 6 

COLOR LEGEND 

- - -Steam 

- - Water 

- - Drain, Overflow 

- - Vents, Bleeders 

- - Alr 

- Safety Valves. Pressure 

Relief Valves 

MANUAL VALVES 

® - Globe 

~ -Gate 

1. Steam Inlet 

2. Steam Control Valve 

3. By-pass 

4. Air, Instrument 

5. FIiter 

6. Pressure Regulator 

7. Drain 

8. Water In let 

9. Stearn Spreader 

10. Basket Supports 

11. Water Baffle 

1·2. Bleeders 

13. Thermometer 

14. Pressure Gauge 

15. Safety Valve 

16. Overflow 

17. Vent 

18. Control, Steam 

19. Control Element 

20. Pressure Relief-Valve 

21. Air Inlet 

22. Pressure Regulator, Air 

Horizontal Retort 

7 

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Crateless Retort 

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8 
Crateless Retort 

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Cooling Canal 

9 
 

 

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Instrumentation 

 Temperature indicating device (Mercury-inGlass - MIG) or equivalent device (e.g., 

Resistance Temperature Device – RTD or 

Digital Temperature Gauge-DTG) 

 Temperature/time recording device 

 Installed in retort shell or external well 

10 
 

 

 

External Well 

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 Must be connected 

through at least a 

3/4” opening 

 Must have at least External 

a 1/16” bleeder Well 

opening 

Bleeder 

11 
 

 

THERMAL PROCESSING 

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Steam Inlet 

 Must be large enough for proper operation 

 Must facilitate air removal 

 Must be located opposite the vent 

12 
 

 

 

 

Steam Spreaders – Vertical Retorts 

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 Not required for 

vertical retorts 

 If used, usually in 

form of a cross 

 Perforations along 

the top or side 

13 
 

 

 

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Steam Spreaders 

Number of Spreader Perforations 

Total cross-sectional area should be equal to 

1.5 to 2 times the cross-sectional area of the 

smallest part of the steam inlet line. 

14 
 

 

 

 

 

 

 

THERMAL PROCESSING 

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Steam Spreaders 

Number of Holes in Steam Spreaders 

for Steam Inlet Pipe Sizes 

Size 

Holes 1 inch 11⁄4 inch 11⁄2 inch 2 inch 21⁄2 inch 

(inches) pipe pipe pipe pipe pipe 

3/16 47–63 82–109 111–148 183–244 261–347 

1/4 27–36 46–61 63–83 103–137 147–196 

3/8 — 21–28 28–37 46–61 66–87 

1/2 — 12–16 16–21 26–35 37–49 

15 
Steam Entry Into Vertical Retort 

16 

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l l 

l 

Steam Entry Into Horizontal Retort 

17 

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' ., • c:.: ,~ -

MORE THAN 30 FEET 

7 1 ~ ' ~ 

. ~ ,. 

) 4 ... ► 

I "-""' ~ I Iii . - , ' I - (STEAM) 

 

Steam Spreaders 

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A RETORT OVER 30 FEET NEEDS TWO 

STEAM SPREADER INLETS. 

18 
 

 

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Vents 

 Large valve-controlled openings to remove air 

from the retort 

 Located opposite steam inlet 

 Controlled by a full flow valve or equivalent 

 Atmospheric break between vent and closed 

drain required 

19 
 

 

 

Vents 

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Inadequate Removal of Air is Serious 

 Less efficient as a heating medium 

 Insulates containers 

 Air and moisture may cause rusting of cans 

20 

235 240 220 

240 on MIG 
0 

Vents 

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MAY USE TWO VENT PIPES FOR 

RETORTS OVER 30 FEET IN 

LENGTH 

21 
 

 

 

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Vents 

Vent Manifold: 

• Connects several vent pipes from same 

retort 

• Cross-sectional area of manifold pipe must 

be larger than cross-sectional area of all 

connecting vents 

22 
 

 

 

Venting and Come Up Time 

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Come Up Time (CUT) = Vent time + the time it 

takes to bring the retort to processing temperature 

 Venting 

removes air 

from the retort 

 Air transfers 

heat less 

efficiently than 

steam 

23 
 

 

 

 

 

THERMAL PROCESSING 

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Venting and Come Up Time 

 Established by process authority 

 May require both a set time and temperature 

 Can be established on the basis of reaching a 

certain temperature 

 Venting schedule must be met to assure 

adequate air removal 

 Retorts with unusual piping, loading or operating 

procedures must be tested for proper heat 

distribution 

24 
• • • • • • • • •••• • • • • • • ••••• • • • • • • • ••••••••• • • • • ••••• • • • • • • • • • •• • • • • • • • • • • • • • • • • • • ••• • •• •.:-:·•·ll!t · 

........ •-:·• .. • • • • • • • • ••• • • • • • • • • • • • • • • • • ••• • . . . . . • • • . . . • • • • • : ·• 

• • • • • • • • • • • • • • • • • • • • • • 

 

 

 

 

••••• 

Construction of Crates, Carts and Divider Plates 

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 Constructed of suitable 

materials 

 Perforations shall be 1” holes 

on 2” centers or equivalent 

(27% open area) 

25 
 

 

 

Effects of Divider Plates on Venting and CUT 

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 May require longer venting time 

 May inhibit steam flow among containers 

 Venting adequacy documented by heat 

distribution data 

26 
Effects of Divider Plates on Venting and CUT 

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27 
Distribution Based on Open Area 

(1) 200 _____ ,_____ ___ ----1----------------1 

~ 

::::s 

...., 

e 115 ----- ----1---- -------------1 

(1) 

C. E 150 -;-----,--- -------.~ ~ - ----------; 

~ 

100 ---i-::-------.----------.-----.---------.----~ 

0 5 10 15 20 25 

Time 

- Jumble loaded-100% 

- 40%open 

- 20%open 

 

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Effects of Divider Plates on Venting and CUT 

28 
 

 

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Bleeders 

 Remove air to provide circulation of steam 

 Must be opposite steam entry 

 Wide open during entire process 

 Arranged to observe functioning 

 Condensate bleeder requirement when steam 

entry is above the containers 

29 
 

 

 

 

 

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Bleeders 

 Small openings, normally 1/16 to 1/8 inch in 

diameter used to remove air from steam 

retorts and circulate the steam while they are 

in operation 

 Open during come up and processing 

 Bleeders must be within 1 foot of outermost 

containers and no more than 8 feet apart 

along the top of the horizontal retort. 

30 
Bleeders 

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Retort Bleeder with Valve 

31 
 

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Mufflers 

 Used on bleeders and vents to decrease 

noise 

 Must not impede normal operation 

32 
 

 

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Air Supply 

 For air-operated automatic steam controllers 

 For pressure cooling to prevent can buckling 

 Equip with a suitable valve to prevent leakage 

33 
 

 

 

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Water Supply 

 For cooling containers in retort 

 Equip with suitable valve to prevent leakage 

 Cool carefully to avoid condensing steam 

34 
 

 

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Temperature and Timing 

Initial Temperature — Must be determined for 

the coldest container 

Process Timing — Must not start until the 

venting schedule is completed and the process 

schedule retort temperature is achieved 

35 
 

 

THERMAL PROCESSING 

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Container Cooling 

 May need pressure cooling 

 Cool to at least 104°F 

 Suggest complete flooding of retort 

36 
000 000 

00 000 

000000 

00 00 

 

Container Cooling 

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Container cooling is done first by overhead 

37 sprays and then by flooding. 
 

 

Container Cooling 

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Valves must be tight fitting and maintained on water pipes to prevent 

leaking water into retort during thermal processing. 

38 
 

 

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Container Cooling 

Cooling Water Treatment 

Container cooling water shall be chlorinated or 

otherwise sanitized for cooling canals and recirculated water supplies. 

39 
 

 

 

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Recordkeeping Requirements 

 Critical factors must be measured and 

recorded in accordance with the method and 

frequency in the written procedure 

 Suggest 15 minute intervals 

40 
Questions 

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Questions?

41