Seward Stomacher 400 Circulator Lab Blender – Used and Refurbished
The Seward Stomacher 400 Circulator Lab Blender is a high-performance paddle blender and laboratory homogenizer designed for fast, reproducible preparation of solid and liquid samples. Widely used in food microbiology, pathogen testing, environmental analysis, life science research, pharmaceutical quality control, and other microbiological applications, the Stomacher 400 Circulator processes samples inside disposable sterile bags to simplify sample preparation while reducing the risk of cross-contamination between specimens.
Designed for sample volumes from 80 to 400 mL, the Stomacher 400 Circulator uses Seward's distinctive kidney-shaped paddle system to generate effective sample circulation during processing. Rather than cutting or grinding the sample with blades, the paddles repeatedly compress and manipulate the sample inside a sealed Stomacher bag. This action helps release microorganisms and other analytes into the surrounding diluent while keeping the instrument itself isolated from the sample.
Programmable paddle speeds from 75 to 300 rpm and an adjustable timer from 0 seconds to 99 minutes 59 seconds allow laboratories to establish repeatable processing conditions for different sample types. Three commonly used programs are also available for rapid setup of routine workflows.
This Seward Stomacher 400 Circulator is used and refurbished by American Instrument Exchange. AIE technicians test the blender before shipment to verify paddle operation, speed control, timer functions, controls, and general operating condition. The instrument is thoroughly cleaned and includes a 90-day warranty.
Key Features
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Seward Stomacher 400 Circulator laboratory paddle blender
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80–400 mL recommended sample-volume range
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Patented kidney-shaped Circulator paddle design
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75–300 rpm adjustable paddle speed
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Speed adjustable in 5 rpm increments
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Programmable timer up to 99 minutes 59 seconds
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Adjustable 0–10 mm paddle clearance
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Continuous-duty design
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Processes samples inside disposable Stomacher bags
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Suitable for solid and liquid sample preparation
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Particularly useful for food microbiology and pathogen testing
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Compact benchtop design
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Used and refurbished by American Instrument Exchange
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90-day warranty included
Overview
The Seward Stomacher has become a familiar sample-preparation instrument in microbiology laboratories because it provides a simple method for homogenizing samples without placing the specimen directly in contact with the instrument.
A sample and the appropriate diluent are placed inside a disposable Stomacher bag. The bag is then positioned between the instrument's paddles and door.
During operation, the paddles repeatedly compress and release the bag. This mechanical action breaks down and mixes the sample while helping transfer microorganisms or other target material into the liquid phase.
Once processing is complete, the bag can be removed and the resulting homogenate used for downstream microbiological or analytical procedures.
Because the sample remains contained inside the bag, laboratories can move rapidly between specimens without having to clean a conventional blender vessel after every sample.
Common Applications
The Seward Stomacher 400 Circulator is widely applicable to food safety testing, food microbiology, pathogen detection workflows, environmental microbiology, pharmaceutical quality control, life science research, microbiome studies, sample extraction, dilution preparation, and other procedures requiring reproducible homogenization of solid or liquid samples.
Typical specimens may include meat, poultry, seafood, dairy products, fruits and vegetables, prepared foods, ingredients, environmental materials, and other samples that can be appropriately processed within the 80–400 mL working range.
The Stomacher prepares the sample for subsequent analysis; it does not itself detect or identify microorganisms.
Ideal Laboratory Types
The Stomacher 400 Circulator is particularly well suited to food-testing laboratories, commercial microbiology laboratories, food and beverage manufacturers, meat and poultry processors, dairy laboratories, environmental testing facilities, pharmaceutical quality-control laboratories, contract testing laboratories, public-health laboratories, academic microbiology departments, life science research laboratories, and other facilities routinely preparing samples for microbiological analysis.
Its continuous-duty construction and disposable-bag workflow also make it useful in higher-throughput laboratories processing many samples during a shift.
Key Specifications
| Specification |
Details |
| Manufacturer |
Seward |
| Product Family |
Stomacher 400 |
| Model |
Stomacher 400 Circulator |
| Equipment Type |
Laboratory Paddle Blender / Homogenizer |
| Recommended Sample Volume |
80–400 mL |
| Paddle Design |
Kidney-Shaped Circulator Paddles |
| Paddle Speed |
75–300 rpm |
| Speed Adjustment |
5 rpm Increments |
| Speed Accuracy |
±5% |
| Timer |
0 sec.–99 min. 59 sec. |
| Timer Accuracy |
±5% |
| Paddle Clearance |
0–10 mm |
| Disposable Bag Size |
177 × 304/305 mm |
| Maximum Recommended Sample Temperature |
60°C |
| Duty Cycle |
Continuous |
| Rated Load |
140 W |
| Dimensions |
330 mm W × 355 mm D × 300 mm H |
| Approx. Dimensions |
13"W × 14"D × 11.8"H |
| Weight |
23 kg / Approx. 51 lb |
| U.S. Supply Voltage |
100–120 V |
| Supply Frequency |
50–60 Hz |
| Condition |
Used / Refurbished |
| Warranty |
90 Days from American Instrument Exchange |
80–400 mL Sample Capacity
The Stomacher 400 Circulator is designed for sample volumes between approximately 80 and 400 mL.
This working range is particularly useful for routine microbiological testing because it accommodates many commonly used sample and diluent combinations.
The appropriate sample-to-diluent ratio should be determined by the laboratory's analytical method rather than by the blender itself.
Laboratories should also select a Stomacher bag appropriate for the sample type and downstream analytical procedure.
Kidney-Shaped Circulator Paddles
One of the primary differences between the Stomacher 400 Circulator and earlier conventional paddle blenders is the shape of its paddles.
The Circulator uses distinctive curved, kidney-shaped paddles rather than traditional square paddles.
The design promotes movement of the sample and diluent around the bag during processing, helping create effective mixing and extraction.
This is particularly relevant in microbiological sample preparation, where the objective is often to recover microorganisms from the surface and internal structure of a food or environmental sample into a liquid diluent for subsequent analysis.
Paddle Blending Without Blades
The Stomacher operates differently from a conventional blade blender.
Instead of using rotating blades to cut the sample, the system applies repetitive mechanical pressure through the walls of a disposable bag.
This process homogenizes and mixes the specimen while avoiding direct contact between the sample and moving mechanical components.
For microbiology laboratories, this can offer important workflow advantages because the sample remains contained throughout processing.
It also avoids the need to disassemble and clean a blade assembly between specimens.
Disposable Bag Sample Processing
Samples are processed inside purpose-designed disposable Stomacher bags.
The specimen and diluent are placed into the bag before loading, and the bag acts as the processing chamber during blending.
Once homogenization is complete, the bag is removed from the instrument and can be used for subsequent sample handling according to the laboratory's procedure.
This approach helps isolate the instrument from biological material and greatly simplifies changeover between samples.
Reducing Cross-Contamination
Cross-contamination is an important concern in microbiology laboratories, particularly when samples are being evaluated for low levels of microorganisms.
Because each specimen is processed in its own disposable bag, the Stomacher minimizes direct sample contact with the blender itself.
This reduces the number of reusable surfaces that must be cleaned between samples and helps separate consecutive specimens.
Appropriate aseptic technique and laboratory procedures remain necessary during sample loading, processing, and downstream analysis.
Adjustable 75–300 rpm Paddle Speed
The Stomacher 400 Circulator provides adjustable no-load paddle speeds from 75 to 300 rpm in 5 rpm increments.
Adjustable speed allows users to modify blending intensity according to sample characteristics.
Delicate or easily dispersed materials may require different processing conditions than dense, fibrous, or heterogeneous specimens.
Once an appropriate procedure has been established, programmable speed control helps laboratories reproduce those conditions between samples.
Programmable Processing Time
Processing time can be programmed from 0 seconds up to 99 minutes and 59 seconds.
Many routine Stomacher procedures require only relatively short blending cycles, but the broad timer range gives laboratories flexibility for specialized protocols.
Using a programmed processing time helps standardize sample preparation between operators.
Reproducible preparation is especially important when results from multiple samples, batches, technicians, or testing dates must be compared.
Preloaded Programs
The Stomacher 400 Circulator provides preloaded programs for commonly used combinations of speed and processing time.
These include settings of 200 rpm for 30 seconds, 230 rpm for 45 seconds, and 260 rpm for 1 minute.
Preset programs can simplify routine operation by reducing the number of parameters that must be entered for frequently repeated procedures.
Laboratories should select processing conditions according to their validated or established analytical method.
Adjustable Paddle Clearance
Paddle clearance can be adjusted from 0 to 10 mm.
This allows the mechanical action of the paddles to be adapted to different sample characteristics and bag contents.
Proper paddle adjustment helps create effective interaction between the paddles and sample without unnecessarily stressing the bag.
The appropriate clearance depends on specimen composition, sample volume, diluent volume, bag type, and processing requirements.
Food Microbiology Sample Preparation
Food microbiology is one of the principal applications for the Stomacher 400 platform.
Before a food sample can be tested microbiologically, organisms associated with the specimen often need to be transferred into a liquid suspension suitable for plating, enrichment, dilution, filtration, or another downstream method.
Paddle blending helps homogenize the sample with diluent and release microorganisms into the liquid phase.
Because the sample remains enclosed within a disposable bag, laboratories can process different food specimens rapidly while minimizing cleaning between samples.
Pathogen Testing Workflows
The Stomacher 400 Circulator is commonly used during sample preparation for foodborne-pathogen testing workflows.
Depending on the laboratory method, samples may subsequently be evaluated for organisms such as Salmonella, Listeria, E. coli, or other microorganisms of interest.
The Stomacher itself does not detect pathogens.
Its role is to prepare a representative homogenized sample that can be used with appropriate culture, immunological, molecular, or other analytical methods.
Meat and Poultry Testing
Meat and poultry products can be challenging to homogenize because of their fibrous and heterogeneous structure.
Paddle blending provides a practical way to combine these specimens with diluent without placing them directly into a reusable blade blender.
The Circulator paddle design promotes sample and fluid movement within the bag, helping create a suspension suitable for downstream microbiological analysis.
Actual preparation procedures should follow the laboratory's approved method.
Dairy and Food-Processing Laboratories
Dairy products, prepared foods, ingredients, and other manufactured food samples may require routine microbiological quality testing.
The Stomacher 400 can support sample preparation for these workflows by providing controlled mechanical blending at a defined speed and duration.
Programmable operation is particularly useful in production and quality-control laboratories where large numbers of samples must be prepared according to the same procedure.
Fruits, Vegetables, and Produce
Fresh produce can also require microbiological analysis for food-safety, quality-control, or research purposes.
The Stomacher 400 Circulator can process compatible fruit, vegetable, and produce specimens with the appropriate diluent and bag configuration.
Adjustable paddle speed and clearance allow laboratories to establish conditions appropriate for different sample textures.
Environmental Microbiology
The Stomacher can also support preparation of appropriate environmental samples.
Solid, semi-solid, or collected environmental materials may need to be mixed with diluent before microbiological analysis.
Bag-based processing can be particularly useful when laboratories need to process many unrelated environmental specimens while limiting carryover between samples.
Pharmaceutical and Quality-Control Applications
Pharmaceutical and industrial quality-control laboratories may use paddle blending for appropriate microbiological or sample-extraction procedures.
The Stomacher's programmable speed and time controls help establish repeatable preparation conditions.
For regulated procedures, laboratories should establish and document operating parameters according to their validated method, quality system, and applicable requirements.
Life Science and Microbiome Research
Paddle blending is also used in life science and microbiome research when biological material must be homogenized or organisms extracted from a sample matrix.
The broad 80–400 mL working range gives researchers flexibility when developing sample-preparation procedures.
Disposable bags can also simplify workflows involving large numbers of independent research specimens.
Continuous-Duty Operation
Seward specifies the Stomacher 400 Circulator for continuous-duty operation.
This makes the instrument particularly useful for busy testing facilities processing samples throughout the working day.
High-throughput laboratories can move from one specimen to the next by replacing the disposable bag rather than cleaning a reusable blender vessel after every cycle.
This combination of durable construction and rapid sample changeover is one reason the Stomacher platform has become widely used in routine microbiology laboratories.
Stomacher vs. Conventional Laboratory Blender
A conventional laboratory blender typically uses rotating blades inside a reusable vessel.
This can provide aggressive homogenization, but the vessel and blades come into direct contact with the sample and generally require cleaning between specimens.
The Stomacher uses external paddles to manipulate the specimen through a disposable bag.
For microbiological workflows, the bag-based approach can reduce cleanup and the potential for cross-contamination while providing reproducible sample homogenization.
Stomacher vs. Homogenizer
The term laboratory homogenizer encompasses many different technologies, including rotor-stator homogenizers, bead mills, ultrasonic homogenizers, blade blenders, and paddle blenders.
The Stomacher is specifically a paddle-type homogenizer.
It is particularly useful when a sample needs to be blended with a liquid diluent inside a closed disposable bag.
More aggressive technologies may be preferable when complete mechanical disruption of cells or hard materials is required.
Selecting Stomacher Bags
Bag selection should be based on sample characteristics and the downstream analytical method.
Seward offers standard Circulator bags as well as other bag configurations, including strainer and closure designs.
Strainer bags can be useful when a liquid homogenate must subsequently be pipetted or analyzed while larger sample particles are retained.
The Stomacher 400 Circulator uses bags approximately 177 mm wide × 305 mm long.
Maximum Recommended Sample Temperature
Seward specifies a maximum recommended sample temperature of 60°C.
Samples above the recommended temperature should not be processed without confirming compatibility with the instrument, bag, and analytical method.
The Stomacher does not provide temperature control.
If a protocol requires samples to be maintained at a particular temperature, appropriate sample-conditioning or temperature-control equipment should be used separately.
Compact Benchtop Footprint
Despite its ability to process samples up to 400 mL, the Stomacher 400 Circulator occupies a relatively compact laboratory footprint.
The instrument measures approximately 330 mm wide × 355 mm deep × 300 mm high, or about 13 × 14 × 11.8 inches.
Its benchtop configuration makes it straightforward to position near microbiological sample-preparation areas, biological safety cabinets, plating stations, or other analytical equipment.
Refurbishment and Testing by American Instrument Exchange
American Instrument Exchange tests used laboratory blenders before shipment to verify proper operation.
For the Seward Stomacher 400 Circulator, AIE technicians evaluate paddle movement, speed control, timer operation, digital controls, door operation, and other installed functions. The instrument is operated to confirm consistent mechanical performance.
Accessible surfaces are thoroughly cleaned prior to shipment.
If your laboratory has a particular speed, timer setting, or testing requirement, contact American Instrument Exchange before shipment. AIE will make reasonable efforts to test the instrument under conditions representative of the intended application.
Why Buy a Refurbished Seward Stomacher 400 Circulator?
The Stomacher 400 Circulator remains a highly useful sample-preparation platform for microbiology laboratories because its fundamental workflow is straightforward, reproducible, and efficient.
Programmable speed and timing, adjustable paddle clearance, kidney-shaped Circulator paddles, disposable-bag processing, and continuous-duty construction make it particularly well suited to laboratories performing repetitive microbiological sample preparation.
Purchasing a used and refurbished Stomacher 400 Circulator from American Instrument Exchange can provide these capabilities at a lower acquisition cost than purchasing new equipment.
AIE tests and cleans the instrument before shipment and includes a 90-day warranty.
Shipping and Installation
The Stomacher 400 Circulator is a benchtop instrument weighing approximately 23 kg, or 51 pounds.
It should be installed on a stable, level laboratory surface with adequate space for opening the door, loading and removing bags, and accessing the control panel.
The U.S. version operates from 100–120 V, 50–60 Hz power and has a rated load of 140 W.
Customers should verify the electrical information shown on the individual unit's nameplate before installation.
Related Equipment
Laboratories using the Seward Stomacher 400 Circulator may also require microbiology incubators, biological safety cabinets, autoclaves, centrifuges, laboratory refrigerators and freezers, water baths, balances, shakers, colony-counting equipment, and other instruments used for microbiological sample preparation and analysis.
American Instrument Exchange supplies used and refurbished laboratory equipment for food-testing laboratories, biotechnology companies, pharmaceutical facilities, environmental laboratories, academic research institutions, quality-control laboratories, and other scientific facilities.
Seward Stomacher 400 Circulator FAQs
What is a Seward Stomacher 400?
The Stomacher 400 is a laboratory paddle blender used to homogenize and mix samples inside disposable bags, particularly for microbiological sample preparation.
What is the Stomacher 400 Circulator?
The Circulator version uses Seward's kidney-shaped paddle design to promote sample circulation and efficient extraction during blending.
What sample volumes can the Stomacher 400 Circulator process?
Seward specifies a recommended sample-volume range of 80 to 400 mL.
What is the paddle-speed range?
The current Stomacher 400 Circulator specification is 75 to 300 rpm with adjustment in 5 rpm increments.
What is the timer range?
Processing time can be set from 0 seconds to 99 minutes and 59 seconds.
Does the Stomacher 400 use blades?
No. It uses reciprocating paddles to process a sample through the walls of a disposable bag.
Does the sample touch the blender?
The sample remains inside the disposable Stomacher bag rather than contacting the instrument's paddles directly.
Why is bag-based blending useful for microbiology?
Using a separate disposable bag for each specimen helps minimize direct sample contact with reusable instrument surfaces and simplifies changeover between samples.
What are the kidney-shaped paddles?
The Stomacher 400 Circulator uses curved paddles designed to promote movement and circulation of the sample and diluent during blending.
Is the Stomacher 400 used for food testing?
Yes. Food microbiology and food-safety sample preparation are among its principal applications.
Can it be used for Salmonella testing?
It can be used to prepare compatible food or environmental samples for downstream Salmonella testing. Detection is performed by the appropriate analytical method, not by the Stomacher itself.
Can it prepare samples for Listeria testing?
Yes. The Stomacher can prepare compatible specimens for subsequent Listeria analysis according to the laboratory's established method.
Can it be used for E. coli testing?
Yes. It can support sample preparation for compatible E. coli testing workflows.
Does the Stomacher detect bacteria?
No. It is a sample-preparation instrument. Microorganisms are detected or quantified using downstream culture, molecular, immunological, or other analytical methods.
What size bags does it use?
The Stomacher 400 Circulator uses bags approximately 177 mm wide × 304–305 mm long.
Are different bag styles available?
Yes. Seward offers multiple Stomacher 400 bag configurations, including standard, closure, strainer, and lateral-strainer designs.
What is the paddle-clearance range?
Paddle clearance can be adjusted from 0 to 10 mm.
Is the Stomacher 400 suitable for continuous use?
Yes. Seward specifies a continuous duty cycle.
What is the maximum recommended sample temperature?
Seward specifies a maximum recommended sample temperature of 60°C.
What are the dimensions?
The instrument measures approximately 330 mm W × 355 mm D × 300 mm H, or about 13"W × 14"D × 11.8"H.
How much does it weigh?
The Stomacher 400 Circulator weighs approximately 23 kg, or 51 pounds.
What power does the U.S. model require?
The U.S. version is specified for 100–120 V, 50–60 Hz operation.
Is this Seward Stomacher 400 Circulator refurbished?
Yes. This unit is used and refurbished by American Instrument Exchange.
How does AIE test a Stomacher?
American Instrument Exchange tests the mechanical paddle action, controls, speed adjustment, timer, door operation, and general instrument functionality before shipment.
Does it include a warranty?
Yes. American Instrument Exchange includes a 90-day warranty with this refurbished Stomacher 400 Circulator.
