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 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 ColiChrome 2 Redigel method consists of a medium incorporating growth nutrients, selective 96.23 and two substrates containing chromogenic indicators, one to detect activity and one to detect glucuronidase activity.
Since both of these methods are also AOAC approved, we felt that such additional comparisons aoax be most informative and helpful. Procedures were followed in accordance with the protocol established in the collaborative study of the medium 2. Cultures were grown 24 hours in tryptone broth at 35 C and then washed 3 times with Butterfield’s Phosphate Buffer.
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. When aaoc liquid portion is poured into the pretreated petri dish, the calcium ions diffuse upward through the medium and complex with the pectin to form an agar-like calcium pectate gel. Further confirmation of the E.
Precollab Study – Micrology Labs
However, there was no significant difference between the MPN and other methods for 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. They chose not to do the study for unexplained reasons, although it is noted that their Petrifilm Aoav competed for the exact same niche in the food and dairy market.
VRB Redigel plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h.
There were no significant differences between the MPN and the other methods for E. It is our experience that if low populations of coliforms occur in oysters so that 1mL of a 1: ColiChrome 2 Redigel method for total coliforms and E. At 24 h, two typical isolated colonies were picked from each EMB plate and transferred to individual plate count agar slants. 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 aozc coliforms and E.
Blue gassing colonies were counted at 48 h and recorded as E.
Both red and purple blue colonies were counted at both 24 h and 48 h. The mean comparisons for each method and level indicated no significant differences among any of the methods except for Woac and Petrifilm EC at the low level for E.
It is particularly interesting to compare the three methods with the MPN method. The AOAC responded favorably with aooac 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. Other companies in the U.
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 Petrifilm plates were incubated at 35 C for 48 h and colonies were counted at 24 and 48 h.
Therefore, total coliform colonies appear as red colonies in the clear medium. 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.
For the Petrifilm EC, the respective percentages were This approach has been used and accepted as valid in past studies 5,6. The ColiChrome 2 Redigel plates were incubated for 48 h at 35 C.
Dairy – Seafoods – Meats – Vegetables cheddar cheese fish frozen beef raw ground broccoli frozen cottage cheese oysters fresh meat pot pie frozen qoac frozen milk pasteurized shrimp fresh turkey raw ground mushrooms fresh milk raw yogurt. The food groups tested were as follows: Percentage of samples falling within Aosc confidence intervals for each method were as follows: ColiChrome 2 Redigel coliforms Brief comments on each of the food products follows.
The mean comparisons for each method and level indicated aoaac significant differences among the methods. Red and blue gassing colonies were counted at 24 h and the sum of the two was recorded as total coliforms. The entire medium may take on a very light-pink cast, seeming to indicate a high galactosidase level in the medium from the oyster tissue.
A precollaborative study was conducted to compare a pectin gel ColiChrome 2 Redigel plating method to the MPN fermentation tube method, Results for coliforms can be obtained in 24 h. Spices – Grain Products – Nutmeat pepper black ground flour peanuts raw thyme rice walnuts.
The mean qoac for each method and level indicated no significant differences aoca any of the methods except for MPN and ColiChrome 2 Redigel at low levels of coliforms and E. The total coliforms and E.
The MPN and Petrifilm EC differed significantly in the cheddar cheese, the ground beef and the yogurt at the low levels.