1 BATCH AGITATING RETORTS Chapter 13. 2 Description of the Retorts Batch type pressure vessels that provide product agitation Referred to as “discontinuous

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BATCH AGITATING BATCH AGITATING RETORTSRETORTSChapter 13Chapter 13

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Description of the Description of the RetortsRetorts

• Batch type pressure vessels that provide product agitation

• Referred to as “discontinuous agitating retorts” in the FDA’s regulations

• Variety of retorts for many product types in an assortment of containers

• Use steam, water, or steam/air as heating medium

• Air or steam may be used as a source of overpressure

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• Majority provide continuous product agitation during the process

• Two basic types of agitation will be discussed• End-over-end• Side-over-side

• Some provide rocking or oscillating

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• Majority rotate the containers end-over-end during the entire processing cycle

• Containers are physically held in crates or racks

• The crates or racks are held and secured within the retort in a rotating frame work

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End-over-endAgitation

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WaterSprayRetort

Crate

Courtesy of FMC Food Tech

Rotating Framework

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• This type of retort can accommodate a wide range of container types and sizes

• Racks can be custom designed for specific containers

• These retorts may be designed for processing with overpressure in• Steam• Water (immersion, cascading, or spray• Steam/air

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• Another type provides side-over-side agitation in pure steam without overpressure

• Containers are loaded using the same design for continuous rotary retorts, reel and spiral T

• Cans loaded through a gate valve onto the rotating reel and with the spiral T the cans are fed into the retort

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• Cans are counted, when full the spiral T is released from the shell wall and locked to the reel, holding the cans in place

• This retort is limited to a narrow range of container sizes due to the spacing and configuration of the spiral T and the reel

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Side-over-sideAgitation

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• The advantages result from faster heating in certain products due to the continuous agitation• Because the containers are held in baskets

or racks in the retort, rotational speeds are generally faster

• Due to the faster rotation and resulting increased rate of product agitation, the process time is generally shorter than that in a still retort – improved quality of product

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• Possible disadvantages • Large initial capital cost• Need to monitor and control additional

critical factors

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• Recommended that the pertinent regulations be reviewed

• New retort systems not specifically mentioned = Other systems

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Agency Regulation Section Title

FDA 21 CFR 113.40(d)

21 CFR 113.40(e)

Equipment and procedures for pressure processing in steam in discontinuous

agitating retortsEquipment and procedures for pressure

processing in steam in discontinuous agitating retorts

21 CFR 113.40(j)

9 CFR 318.305 (b)(2)

9 CFR 381.305 (b)(2)

Other systems

Pressure processing in steam – batch agitating retorts

USDA-FSIS 9 CFR 318.305 (c)(2)

9 CFR 381.305 (c)(2)

9 CFR 318.305 (d)9 CFR 381.305 (d)

Pressure processing in water – batch agitating retorts

Pressure processing with steam/ air mixtures in batch retorts

U.S. regulations specific to batch agitating retorts

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Installation and Operation Installation and Operation of Retortsof Retorts

• Proper installation and operation essential to achieving satisfactory processing results• Installation considerations depend on the

heating medium and the source of overpressure

• These retorts equipped with various controls and alarms to monitor critical factors • The general specifications for these

instruments are outlined in Chapter 8

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Instrumentation and Instrumentation and EquipmentEquipment

• For each retort there shall be• one temperature-indicating device• one temperature-recording device

• Placement of sensors depends on the processing medium

• In addition each retort shall have• An automatic steam controller

• Can be a combination recording/controlling instrument

• Must respond only to temperature if retort operating with overpressure

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• A means shall be provided to circulate the heating medium• Ensures uniform temperature distribution

• Operating procedures developed to ensure uniform temperatures shall be documented by temperature distribution data or other documentation from a process authority

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• This documentation shall be maintained by the establishment

• Made available for inspection by the appropriate regulatory agency

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• For processes requiring overpressure, the USDA-FSIS specifies that the retort system shall be equipped with a pressure recording device, which may be combined with a pressure controller

• Each retort shall be equipped with a pressure gauge that can be easily read

• USDA-FSIS requires overpressure shall be maintained continuously

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• Overriding pressure may be supplied in the form of air or steam

• The retort shall have an automatic pressure control unit to control the air or steam entering or leaving the retort

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Rotational SpeedRotational Speed

• Rotational speed will be specified in the scheduled process

• The speed shall be adjusted, as necessary, to ensure that it remains as specified

• The speed shall be checked and recorded for each retort load processed

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Rotational SpeedRotational Speed

• Alternatively, a recording tachometer may be used to maintain a continuous record

• USDA-FSIS requires that the accuracy be determined and recorded at least once per shift – check with accurate stopwatch

• A means of preventing speed changes shall be provided- lock or notice• Only management authorized individuals

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Cooling Water SupplyCooling Water Supply

• When glass containers are processed, the cooling water should be introduced so it does not strike the containers directly

• This is to minimize breakage due to thermal shock

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• Depending on the system, water can be• Introduced directly into the processing

vessel• Introduced into the suction side of the

circulation pump• Introduced through a mixing chamber• Cooled through a heat exchanger

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• Cooling with water introduced via a mixing chamber or heat exchanger greatly reduces stress on packages and also simplifies control of overpressure

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Specific Types of Retorts Specific Types of Retorts Utilizing OverpressureUtilizing Overpressure

• Water Retorts (Total Immersion, Cascading or Sprays) with Overpressure

• Steam Retorts• Steam/Air Retorts

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Water Retorts Water Retorts (Total Immersion, Cascading or Sprays) with (Total Immersion, Cascading or Sprays) with

OverpressureOverpressure

• Retorts with water as the heating medium usually designed to provide end-over-end agitation

• The range of rotational speeds will vary depending on the manufacturer

• Features similar to those discussed in Chapter 10

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• USDA-FSIS requires that the sensor of the indicating device extend directly into the water without a separate well or sleeve

• The FDA allows the use of external wells • USDA-FSIS requires that the recorder-

controller sensor be located between the water surface and the horizontal plane passing through the center of the retort

• The FDA requires that this sensor be installed either in the shell or in a well

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• Care must be taken to ensure that steam used to heat the water does not directly strike the sensor of the temperature-recording device

• Due to the wide variety of retort types, alternate locations may be permitted provided the location is acceptable to the regulatory agency and temperature distribution data supports the accuracy of the measurements

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• Each retort shall have an automatic pressure control unit to introduce air or steam to maintain overpressure• If air used, a check valve shall be in the

air supply line• If steam is used, an independently

controlled steam source is needed• Separate from the system used to control

temperature

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• A pump is used to mechanically circulate the water within the retort to provide adequate temperature distribution

• The processing water is drawn from the bottom through a suction manifold

• Discharged through a manifold spreader or other distribution system

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• The pump shall be equipped with a pilot light or other signaling device to warn when it is not operating

• USDA-FSIS permits the use of a flow-meter alarm system

• Alternate methods of water circulation may be used provided adequate temperature distribution or other documentation is available

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• Retorts that require maintenance of a specific water level shall be equipped with a non-clogging watertight drain valve and screens over all drain openings and water suction outlets• Reduces the risk of water leaking and

protects pumps from foreign objects• A low water level may result in

underprocessing

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• A method shall be provided to monitor the water level during processing• Sight glass or low water level alarm

• For total immersion – water shall cover all the containers during the specified portion of the come-up and processing period

• Water should also cover the top layer during the cooling period

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Sight Glass With

Low-waterLevel

Sensor

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• Level in cascading water and water spray retorts must be maintained within the range specified by the manufacturer or processing authority during come-up, processing, and cooling

• The operator shall check and record the level if required by the processing authority

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Steam Retorts Steam Retorts • Depending on the design, retorts with

steam as the heating medium may provide either side-over-side or end-over-end agitation

• Similar to retorts discussed in Chapter 9, sensors for indicating and recording devices are inserted directly into the shell or in an external well

• Shall be vented or otherwise provide for removal of air before process timing begins

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Steam Retorts Steam Retorts

• Bleeders are required and shall be wide open during the entire processing period, including come-up

• All bleeders shall be arranged so the operator can observe that they are emitting steam

• Further information is found in Chapter 9

• Requirements are the same as for horizontal steam retorts

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Steam Retorts Steam Retorts • USDA-FSIS requires that provisions be

made for removal of condensate• Drain shall be open for a time sufficient

to remove condensate during initial venting

• Continuing drainage of condensate during the process

• Condensate bleeders shall be arranged so the operator can observe that condensate is adequately removed

• Bleeder shall be checked with sufficient frequency to ensure condensate removal – 15 minute interval suggested

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Steam Retorts Steam Retorts

• USDA-FSIS requires that intermittent condensate removal systems be equipped with an alarm system to serve as a continuous monitor

• The alarm system shall be checked at the beginning of each shift and the results recorded

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Steam/Air Retorts Steam/Air Retorts

• Usually designed to provide end-over-end container agitation

• Steam/air is the heating medium• Features of these retorts similar to

those discussed in Chapter 10

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Steam/Air Retorts Steam/Air Retorts

• USDA-FSIS requires that the sensors for indicating and recording devices be inserted directly into the retort shell so that steam does not strike them directly

• A fan is typically used to circulate the heating medium and maintain uniform temperature distribution

• The fan shall be equipped with a signaling device

• Provisions should be made to remove condensate

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Processing Processing ConsiderationsConsiderations

• Product movement inside the container is influenced by its thickness (consistency), the container head space, and the rotational speed of the retort

• For each product, container type, and retort type there is a range of rotational speeds that provide optimum product agitation

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Processing Processing ConsiderationsConsiderations

• It is important to note that minimum headspace, maximum consistency, and rotational speed may be specified as critical factors for the agitating process

• If these or other factors (e.g. vacuum, fill wt., container specifications) are not met, product agitation may be reduced or eliminated, resulting in underprocessing

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HeadspaceHeadspace• Normally expressed as gross headspace• It may be measured before or after

sealing the container• The measurement is taken by

determining the distance from the product level to the top of the open container (e.g. can body flange or double seam, glass jar finish)

• Measurement normally expressed in sixteenths or thirty-seconds of an inch

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Measuring Gross Headspace

A straight edge is placed over the top edges of an open container.The distance is measured from the bottom of the straight edge to the top of the product surface

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ConsistencyConsistency• Consistency and viscosity are objective

measurements of the thickness of the product – various instruments available for making these measurements

• If product is thicker than specified in the scheduled process, product may heat slower and the process may no longer be adequate

• Measurements shall be made on product taken from the location and at the conditions specified in the scheduled process

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Process Schedule Process Schedule ApplicationApplication

• The initial temperature of the coldest container in the retort at the time the processing cycle beings must be determined and recorded

• Process timing shall not start until venting or other required operating procedures have been completed and the required retort temperature is observed on the indicating device

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Record RequirementsRecord Requirements

• All critical factors specified in the scheduled process shall be measured and recorded at intervals of sufficient frequency to ensure that they remain within the limits specified

• These intervals should not exceed 15 minutes

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Record RequirementsRecord Requirements• Depending on the system, some

additional process parameters which may need to be monitored and recorded include:• Time steam on• Start of process timing• Time steam off• Actual processing time• Rotational speed (once per batch)• Maintenance of overpressure• Venting procedure• Maintenance of steam/air circulation system• Steam/air ratio• Actual venting time and temperature

Documents

1 BATCH AGITATING RETORTS Chapter 13. 2 Description of the Retorts Batch type pressure vessels that provide product agitation Referred to as “discontinuous