Matrices, Fish/Cooked Seafood, Meat/Frozen Cooked Meat Products, Nuts and Nut Products/Tree Nut Meats. Approved By, AOAC. Method Number, recommended by AOAC Official Method (1). The ap- propriate dilutions were analyzed by the AOAC pour plate method (AOAC ) and the SimPlate . AOAC Compendium of Methods for the Microbiological Examination of Foods 4th Edition: Chapter 7. FDA Bacteriological Analytical Manual: Chapter 3.
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The mean comparisons for each method and level indicated no significant differences among any of the methods or levels. Further confirmation of the E. Total coliforms produce the enzyme galactosidase which cleaves the first substrate to form an insoluble red dye.
The total coliforms and E. Therefore, 15 samples of each of the 20 products were tested by aaoac method. Likewise, the Duncan mean comparisons for E.
The mean comparisons for each method and level indicated no significant differences among any of the methods except for the MPN and Petrifilm EC at the high level of coliforms. This study was designed in consultation with Dr.
The MPN and Petrifilm EC differed significantly in five other instances, those being in the pasteurized milk at the low and high levels, the black pepper and mushrooms at the medium level and the shrimp at the high level.
The mean comparisons for each method and level indicated no significant differences among any of the methods. This study resulted in considerably more insights and information than originally expected. VRB Redigel plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h.
However, comparison of ColiChrome 2 Redigel with the other 2 rapid methods showed The mean comparisons for each method and level indicated no significant differences among any of the methods except for MPN and Petrifilm EC at the low and high levels for E. The mean comparisons for each method and level indicated no significant differences among the MPN and any of the other methods except for MPN and Petrifilm EC at the medium level for coliforms.
Statistical analyses were done by Mr. This kind of result raises the question of the accuracy of the MPN method for those cases. The Redigel Pectin Gel Method consists of two parts, the first being the liquid portion containing the ingredients plus the gelling agent, and the second part consisting of a petri dish coated with a thin gel layer containing calcium ions.
The study included 20 different food and dairy products representing a broad variety of the major groups. The ColiChrome 2 Redigel method consists of a medium incorporating growth nutrients, selective factors and two substrates containing chromogenic indicators, one to detect activity and one to detect glucuronidase activity. Based upon the results of this study, we believe that any of the three rapid methods may be used effectively to differentiate and confirm coliforms or E.
Also, thanks to F. Confirmation of total coliforms was done by picking 2 red colonies from each of the duplicate plates at 24 h. Other companies in the U. The mean comparisons for each method and level of coliforms indicated no significant differences among any of the methods except for Petrifilm EC and VRB Redigel and at the low level. This technology represents the first use of more than one chromogenic enzyme substrate being used in a diagnostic medium and the first patent was issued in For the Petrifilm EC, the respective percentages were In the general linear models procedure for coliforms, the MPN differed from all 3 other methods in two foods, but the differences were not for all levels of bacteria in each food Flour, at low level only; oysters, at low level only.
Red or pink colonies were counted and recorded as total coliforms. The mean comparisons for each method and level indicated no significant differences among any of the methods except for MPN and Petrifilm EC at the low level for E. Due to our awareness that MPN methods have been reported to exhibit significant variability 7the authors decided to also include as part of the study a comparison to the VRB Redigel method for total coliforms and a comparison to the Petrifilm EC method for total coliforms and E.
The food groups tested were as follows: ColiChrome 2 Redigel coliforms This study was originally designed to satisfy the requirements of a precollaborative study leading to the approval and implementation of a collaborative study on the use of ColiChrome 2 Redigel for the differentiation of total coliforms and E.
ColiChrome 2 Redigel method for total coliforms and E. A precollaborative study was conducted to compare a pectin gel ColiChrome 2 Redigel plating method to the MPN fermentation tube method, The precollaborative study therefore has lain dormant since then until the reacquisition of the ColiChrome technology by RCR Scientific who sold it to Micrology Laboratories The mean comparisons for each method and level indicated no significant differences among any of the methods and levels except for MPN with all the others at the low levels for coliforms.
Each test was done with the three tube MPN procedure and with duplicate plates in each of the other methods. Petrifilm plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h.
Dairy – Seafoods – Meats – Vegetables cheddar cheese fish frozen beef raw ground broccoli frozen cottage cheese oysters fresh meat pot pie frozen corn frozen milk pasteurized shrimp fresh turkey raw ground mushrooms fresh milk raw yogurt Spices – Grain Products – Nutmeat pepper black ground flour peanuts raw thyme rice walnuts Preparation of Test Samples Food samples were prepared according to instructions in AOAC The AOAC responded favorably with permission to proceed with a collaborative study, but at that point in timethe patents and technology for the ColiChrome 2 Redigel method were purchased by 3M Company, and it became their option whether to do the study.
They chose not to do the study for unexplained reasons, although it is noted that their Petrifilm EC competed for the exact same niche in the food and dairy market.
The ColiChrome 2 Redigel plates were incubated for 48 h at 35 C. The complete set of data for all samples is given in Table 5.
Precollab Study – Micrology Labs
qoac However, there was no significant difference between the MPN and other methods for coliforms. Also, none of the mean comparisons for each method and level differed significantly. Bontrager of RCR Scientific.