As the number of microbiology tests performed in the food industry increases due to companies meeting new regulatory requirements, fulfilling customer demands and with added emphasis on internal QA/QC programs, efforts are being made to streamline testing methods–both hands-on time to set up a test and time to final result.

One important line of development has been to improve ready-to-use plates in which the only requirement is to add sample without the need for molten agar. The latest, and most significant improvement, is the Peel Plate® developed by Charm Sciences and available from Weber Scientific. It consists of a dehydrated medium contained in a molded plastic dish with a flexible film cover to maintain sterility before use and during incubation.

Features of Peel Plate
1.    It is very easy to inoculate, and the gel characteristics allow the sample to wick and diffuse through the entire plate in just a few seconds.

2.    Once inoculated, all that is required is to replace the peel back cover. No unique spreading devices are needed.

3.    Following standard microbiology practice, plates are inverted and can be stacked easily, because of how the Peel Plate is molded. This prevents them from sliding around and also maximizes air circulation because of the space between each plate.

4.    Colonies are easy to count and read, thanks to clear color formation from the indicator dyes that are used.

Available Tests
Several tests are available: Aerobic Plate Count (AC); coliforms (CC); combined coliforms/E. coli (EC); Enterobacteriaceae (EB) and yeast and molds (YM). Colony counting is easily quantified by color: AC colonies are red; coliforms and Enterobacteriaceae are also red, while E. coli colonies are blue-black–this also avoids having to note gas formation, which is not always obvious. YM colonies are blue, green or gray.

The chemistry of the indicator dyes is well-known to microbiologists. For AC, tetrazolium chloride is used; for other tests, substrates that are targets for characteristic enzymes. So the methods are based on a well-established principle and presented in a format that is very user-friendly.

Regulatory Approvals
These are important, and studies have been carried to obtain the following certifications. Aerobic Plate Count and coliform/E. coli are both AOAC-RI and PMO-NCIMS approved; YM is AOAC-RI approved. Samples tested included a wide variety of dairy products including raw milks (from cows, sheep and goats), a wide range of pasteurized and flavored milks and other products such as ice cream, UHT milk, creams and fermented milk products. This list is by no means exhaustive, and neither is it limited to dairy products–meat and poultry matrices have been tested–ground beef and turkey, liquid egg and carcass rinses.

Environmental Testing
The Peel Plate is also suitable for environmental samples, an area of testing that has been increasingly recognized as important in reducing microbial contamination of product. For example, sponges used to sample surfaces are placed in a suitable resuspension medium in which they are squeezed to maximize recovery of microorganisms. From this suspension, a 1-mL sample is taken and used to inoculate a plate.

If a larger sub-sample is required, then a high-volume version of Peel Plate is also available which will accommodate a 5-mL sample.

Automated Colony Counter
While colonies are easy to see and record with the naked eye, the latest development is an automated colony counter that reads Peel Plates in a few seconds and retains an electronic record of the result. According to Sharon Wilson, senior national accounts manager for Weber Scientific, “This adds further savings in terms of time to analyze a result, and record-keeping is becoming increasingly important as food companies seek to comply with FSMA regulations.”

Market Acceptance
Fred Weber, President, Weber Scientific, also notes, “The interest in this product is outstanding. Of all the many benefits that people often mention, the ability to stack plates 20 high without them sliding around and the convenience of the rapid self-wicking with no spreading device required.” This was borne out at major food conventions during the summer of 2016. At both the Institute of Food Technologists (IFT) annual meeting in Chicago and the International Association for Food Protection (IAFP) convention in St. Louis, there was a very high level of interest from attendees, who immediately appreciated what the Peel Plate had to offer, and its advantages. 

Free Samples
Free samples of Peel Plate are available. Please contact Weber Scientific at 1-800-328-8378 or