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 study included 20 different food and dairy products representing a broad variety of the major groups. 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.
Precollab Study – Micrology Labs
At 24 h, two typical isolated colonies were picked from each EMB plate and transferred to individual plate count agar aoad. In two aoad the foods cheddar cheese and oystersthe MPN results were significantly different than the other three methods.
In-house studies with fresh clams and mussels have indicated that this activity is either lacking in their tissues or is at such low levels as to not interfere with excellent recovery of total coliforms with ColiChrome 2 Redigel. When the liquid portion is poured into the pretreated petri dish, the calcium ions diffuse aaoac through the medium and complex with the pectin to form an agar-like calcium pectate gel.
The mean comparisons for each method and level indicated no significant differences among any of the methods or levels. Confirmation of total coliforms was done by picking 2 red colonies from each of the duplicate plates at 24 h.
This akac has been used and accepted as valid in past studies 5,6. The mean comparisons for each 96.23 and level indicated no significant differences among any of the methods except for ColiChrome 2 Redigel and Petrifilm EC with VRB Redigel at the low level for coliforms. Total coliforms produce the enzyme galactosidase which cleaves the first substrate to form an insoluble red dye. Results for coliforms can be obtained in 24 h. Brief comments on each of the food products follows.
Also, thanks to F. Aooac total coliforms and E. 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. However, there was no significant difference among all the other methods for both coliforms and E. Therefore, total coliform colonies appear as red colonies in the clear medium. Since both of these methods are also AOAC approved, we felt that such additional comparisons would be most informative and helpful.
The procedures were followed according to instructions provided aiac the product and the counts were made in accordance with the protocol established in the collaborative study of the product 6. However, comparison of ColiChrome 2 Redigel with the other 2 rapid methods showed Likewise, the Duncan mean comparisons for E. Totally accurate differentiation of total coliforms and E. 9666.23
Also, the Duncan mean comparisons for E. The mean comparisons for each method and level indicated no significant 9662.3 among any of the methods except for MPN and Petrifilm EC at the low and high levels for E. It should be noted that the names ColiChrome 2 Redigel and Coliscan Easygel are synonymous for the same original product, so that whatever pertains to ColiChrome 2 Redigel is equally true for Coliscan Easygel.
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.
Blue gassing colonies were counted at 48 h and recorded as E. Red and blue gassing colonies were counted at 24 h and the sum of the two was recorded as total coliforms. Also, none of the mean comparisons for each method and level differed significantly. Red colonies were recorded as total coliforms and purple colonies were recorded as E. For the Petrifilm EC, the respective percentages were Following the introduction of the technology by RCR Scientific, the idea was copied by most of the major media makers worldwide since the RCR patent only covered the U.
This study resulted in considerably more insights and information than originally expected. The Duncan mean comparisons for E. VRB Redigel plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h. 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 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.
The data presented in this paper were from the 24 h. Following are some observations and comments for Duncan’s Multiple Range Test for coliforms. The MPN and VRB Redigel differed in corn, meat pot pie, and pasteurized milk at the low levels, the pepper at medium level and the pasteurized milk at the high level. The study was submitted to the AOAC for the purpose of receiving permission to do an official collaborative study with the goal of having ColiChrome 2 Redigel being approved as an official method of the AOAC.
Therefore, various media formulations can be easily made according to the standard accepted ingredients for each individual medium. The mean comparisons for coliforms with each method and level indicated significant differences between the MPN and Petrifilm and VRB Redigel at the medium level, but no significant differences at the high and low levels for all methods compared to the MPN.
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. Percentage of samples falling within MPN confidence intervals for each method were as follows: The mean comparisons for each method and level indicated no significant differences at the medium level, but significant differences at the high levels of coliforms for all methods compared to the MPN and at the low levels of coliforms for Petrifilm EC and VRB Redigel.
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. However, we believe that the direct comparisons of the four methods contribute significantly to questions about the methods.