Evaluation on Uncertainty of Detection Results of Aerobic Plate Count

[Objectives]To determine the aerobic plate count(APC)in the milk samples,evaluate the uncertainty of the test results,and to provide a scientific basis for the quality control of the testing process.[Methods]In compliance with the national food safety standard Food Microbiological Examination:Aerobic Plate Count(GB 4789.2-2016),the aerobic plate count in the milk samples was detected.The source of the uncertainty of the test result was analyzed and a mathematical model was established in accordance with Evaluation and Expression of Uncertainty in Measurement(JJF 1059.1-2012).Then,the introduced uncertainty components were evaluated to determine the uncertainty of the final combined aerobic plate count.[Results]The expanded uncertainty of the test result of the aerobic plate count in the milk samples was 0.0434,and the logarithmic value interval of the results was(3.924,4.010),and the antilogarithm was taken to get the aerobic plate count in the sample to be 8395-10233 CFU/mL.[Conclusions]This method can effectively evaluate the uncertainty of the aerobic plate count,and ensure the accurate and scientific laboratory test data.

Comparison of 3 M^TM Petrifilm^TM Aerobic Count Plates with Pour Plates for Determination of Aerobic Plate Counts in Fermented Chile Mash

Fermented chile pepper mash is a major food product in New Mexico. There are few reports on the fermentation process or on methods to monitor it, In the current study we examined a pour plate procedure with an overlay using plate count agar and 3 MTM PetrifilmTM Aerobic Count （AC） plates for determination of total aerobic bacterial counts during the fermentation of chile mash. Fifty chile mash samples were obtained directly from commercial fermentation vats and examined within 2 h of collection. Serial dilutions of the chile mash were prepared in Butterfield＇s Phosphate Buffer. 1 mL portions of the diluted samples were aliquoted in duplicate onto the AC plates and into empty Petri dishes. Plate count agar was poured and once the plates had solidified, they were overlaid with about 10 mL of PCA to minimize spreaders. Plates were incubated at 30 ℃ for 48 h and enumerated. Paired difference tests were conducted on log transformed data to compare the results of the two plating procedures. For commercial chile mash samples, we did not show any significant differences between the AC plate counts and the pour plate counts （α = 0.05）, 3 MTM PetrifilmTM AC plates are a good alternative to pour plates for the determination of the total aerobic counts in fermented chile mashes.

Bacteriological Assessment of the Quality of Raw-mixed Vegetable Salads Prepared and Sold by Street Food Vendors in Korle-Gonno, Accra Metropolis, Ghana

It is known that raw-mixed vegetable salads are essential part of people＇s diet all around the world. These vegetables salads are consumed raw and often without heat treatment or thorough washing. Raw-mixed vegetable salads therefore can serve as vehicle for the transmission of pathogenic microorganisms associated with human diseases. The aim of this study was to isolate and analyze the common bacterial pathogens associated with raw-mixed vegetable salads prepared and sold by street food vendors in Korle-Gonno, Accra, Metropolis, Ghana. A total of 75 different raw-mixed vegetable salads were sampled from the open places and were subjected to bacteriological analysis using standard Food and Agriculture Organization （FAO） of the United Nations （UN） total aerobic plate count method. A total mean colony count of bacteria ranged 0.87-5.6 log10 CFU/g was isolated. Escherichia coli （35%）, Staphylococcus aureus （33%）, Klebsiella sp. （17%）, and Bacillus sp. （15%） were the bacteria isolated from the various raw-mixed vegetables salads investigated. This study has shown that all the raw-mixed vegetable salads sampled from Korle-Gonno, Accra Metropolis, Ghana had a high bacterial contamination and their persistence and proliferation is a reflection of poor hygienic practices by the street food vendors. The use of unsafe or contaminated water to irrigate the vegetables when growing on the farm or garden could also be a contributing factor.

Microbial profile of some ready-to-cook frozen food items sold in Dhaka city,Bangladesh

This study aimed to assess the microbiological quality of 159 animal-and plant-based ready-to-cook(RTC)frozen food items currently popular in Dhaka.Microbiological analyses were carried out to enumerate total aerobic counts of mesophilic bacteria,yeast and mold and to detect some common foodborne pathogens according to standard microbiological criteria.Higher microbial loads in all animal-based food types,other than chicken strips were found.In contrast,plant-based items were relatively safe except paratha,dal-puri,rooti chapati,and aloo-puri.Several common pathogenic bacterial species were screened by analyzing their morphological,cultural,and biochemical characteristics.Escherichia coli was prevalent in most samples,while Salmonella species were least reported.A considerable number of samples exhibited enough microbial loads at infection or intoxication levels.