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 96.23 broad variety of the major groups. Spices – Grain Products – Nutmeat pepper black ground flour peanuts raw thyme rice walnuts.
The entire medium may apac on a very light-pink cast, seeming to indicate a high galactosidase level in the medium from the oyster tissue. ColiChrome 2 Redigel coliforms The decision to base this study on a comparison of ColiChrome 2 Redigel to the standard MPN method was influenced by the fact that other recent collaborative studies have been done and approved on the basis of this format 5,6.
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 966.223 detect glucuronidase activity.
It is particularly interesting to compare the three methods with the MPN method. 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.
Blue gassing colonies were counted at 48 h and recorded as E. Statistical analyses were done by Mr. Five separate lots of each product were tested and each lot was represented by low, medium and high total coliform and E. Red colonies were recorded as total coliforms and purple colonies were recorded as E.
Precollab Study – Micrology Labs
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.
The Duncan mean comparisons for E. Microbiological Analysis of Prepared Samples Each of the prepared samples was analyzed by the following methods: VRB Redigel plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h. Totally accurate differentiation of total coliforms and E.
Redigel is an agar plate substitute whose only basic difference to standard agar plate media is the substitution of a low methoxyl pectin for agar as the gelling agent in the media. This approach has been used and accepted as valid in past studies 5,6. 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.
Dairy – Seafoods 9666.23 Meats – 966.32 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 9662.3 – Nutmeat pepper black ground flour peanuts raw thyme rice walnuts Preparation of Test Samples Food samples were prepared according to instructions in AOAC Red and blue gassing colonies were counted at 24 h and the sum of the two was recorded as total coliforms.
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.
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.
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.
However, comparison of ColiChrome 2 Redigel with the other 2 rapid methods showed The mean comparisons for each method 96.623 level indicated no significant differences among any of the methods except for the MPN and Petrifilm EC at the high level of coliforms. References 1 Roth, J.
Aowc 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. 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.
The mean comparisons for each method and level indicated no significant differences among any of the methods or levels. The MPN and Petrifilm EC differed significantly in five other instances, those being in the pasteurized milk at the aac and high levels, the black pepper and mushrooms at the medium level and the shrimp at the high level.
966.32 comparisons were done for each level of each of the methods table 3 and the Duncan procedure for pairwise comparisons of the methods was also done table 4.
Procedures were followed in accordance with the protocol established in the collaborative study of the medium 2. It is our experience that if low populations of coliforms occur in oysters so that 1mL of a 1: Therefore, various media formulations can be easily made according to the standard accepted ingredients for each individual medium.
Percentage of samples falling within MPN confidence intervals for each method were as follows: At 24 h, two typical isolated colonies were picked from each EMB plate and transferred to individual plate count agar slants. 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.
Results for coliforms can be obtained in 24 h. The number of samples falling within the MPN method confidence intervals was calculated for each of the methods tested and an overall high degree of agreement occurred for each method. Cultures were grown 24 hours in tryptone broth at 35 C and then washed 3 times with Butterfield’s Phosphate Buffer.
Confirmation of total coliforms was done by picking 2 red colonies from each of the duplicate plates at 24 h. The results of samples of 20 foods were collected and statistically analyzed.