FSTest Aerobic Count Plate (Gel-Type) (25 Tests)

Product Overview

The FSTest Aerobic Count Plate (Gel-Type) is a ready-to-use, disposable cold-water-soluble cultural medium designed for the rapid and precise enumeration of total aerobic bacteria in food safety auditing and water environmental testing. This simplified plate structure replaces conventional, time-consuming agar preparation, autoclaving, and tedious pouring workflows.

By integrating specialized dry nutrient ingredients with a cold water-soluble gelling matrix and a built-in biochemical metabolic indicator, the system streamlines routine microbial monitoring for food processing plants, quality assurance labs, and water utilities striving for seamless HACCP regulatory compliance.

Product Highlights & Key Benefits

· Accelerated Incubation & Visible Results: Most foodborne aerobic bacterial colonies manifest as distinct red spots in 24 hours, dramatically saving holding time compared to traditional agar plate methodologies.

· High Visual Counting Accuracy: Pre-loaded with triphenyl tetrazolium chloride (TTC)—a highly stable dehydrogenase indicator. Active bacterial metabolism reduces TTC into an insoluble vibrant red complex, making tiny colonies exceptionally easy to spot and count.

· Equipment-Free Medium Preparation: Eliminates the need for traditional boiling, cooling, and pH adjustment of agar medium. Simply uncover the film, pipette the sample directly, and let it solidify.

· Integrated Built-In Grid System: Features a standard circular layout overlaid with precise small square grids, allowing operators to use cross-sectional calculations if colonies are too numerous to count.

· Room Temperature Stable Transport: Formulated to withstand standard room temperature transport for up to 15 days, providing unparalleled logistics cost advantages before cold refrigeration storage.

Technical Principle & Color Expression

The FSTest Aerobic Count Plate relies on a specialized microbial respiration indicator mechanism. The matrix contains cold water-soluble absorbent gel, standard microbiological nutrients, and the tetrazolium salt indicator (TTC).

During the active incubation period, living bacterial cells produce dehydrogenase enzymes as part of their metabolic respiratory chain. These enzymes reduce the colorless triphenyl tetrazolium chloride (TTC) into a highly visible, stable red dye known as triphenylformazan:

Bacterial Respiration (Dehydrogenase Enzyme) + TTC (Colorless) → Triphenylformazan (Vibrant Red Spots)

This specific biological reduction explicitly markers colony localization, rendering clear red dots that completely remove guesswork during final enumeration.

Specifications & Limit of Detection

Step-by-Step Procedure

1. Serial Dilution (Sample Treatment)

·  Primary 1:10 Dilution: Weigh or measure exactly 25 g (or mL) of your sample matrix and add it into a sterile sampling container or homogenization bag containing 225 mL of sterile water, sterile saline, or standard phosphate buffer solution. Homogenize thoroughly to get the 1:10 sample homogenate.

·  Subsequent Dilutions: Pipette 1 mL of the 1:10 homogenate into a tube containing 9 mL of sterile diluent to establish a 1:100 dilution ratio. Repeat sequentially to reach 1:1000 or lower, making sure to use a brand-new pipette tip for each single serial step. (Note: Undiluted original liquid samples can be used directly when required.)

2. Inoculation Workflow

· Place the test count plates onto a sterile, clean laboratory bench or clean biosafety cabinet.

· Carefully lift and uncover the top protective film barrier layer.

· Pipette exactly 1 mL of the selected dilution solution and dispense it directly onto the precise center of the circular inoculation area.

· Carefully lower and recover the top film, executing the motion smoothly to completely avoid trapping air bubbles.

· Gently place and use a standard plate spreader on top of the film to evenly distribute the liquid sample over the entire circular matrix. Let it stand undisturbed for at least 10 seconds until the cold-water gel solidifies completely.

· Inoculate duplicate plates for each dilution level alongside one blank negative control.

3. Incubation Settings

Stack the solidified plates horizontally with their front sides facing upward. To ensure uniform thermal regulation inside the incubator, do not stack more than 20 plates together at one time. Incubate according to your matrix type (36 ± 1°C for 24h for general foods, or 30 ± 1°C for 48h for seafood).

Results Determination & Mathematical Enumeration

· Standard Counting Range: Select plate diluents that generated a moderate distribution between 30–300 CFU. Take the average colony count of the duplicate plates and multiply it directly by the corresponding dilution factor.

· High-Density Overload Estimation: If all dilution levels exceed 300 CFU, locate the highest dilution plate. Select several representative small square grids, calculate the average colony count per square, and multiply that average by 28. This estimates the total plate count, which you then multiply by the highest dilution factor. Record all other lower dilution levels as 'Too Numerous To Count' (TNTC).

· Low-Count Estimation: If all plates remain below 30 CFU, calculate the average of the lowest dilution level and multiply it by its dilution factor. If absolutely no spots appear, report the final figure as 'less than 1' multiplied by the lowest dilution factor.

· Control Validity Check: If any red bacterial colonies manifest on the blank negative control plate, the entire test batch is strictly invalid and must be re-run.