Rapid plate counting techniques for enumeration of psychrotrophic bacteria in pasteurized double cream

Griffiths, Mansel W.; Phillips, John D.; Muir, D. D.

doi:10.1111/j.1471-0307.1980.tb01455.x

Cited by 22 publications

(3 citation statements)

References 12 publications

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“…The bacterial quality of pasteurized milk samples from the U.K. and Canada was investigated using a number of preincubation conditions (see Materials and Methods) reported to give rapid estimates of postpasteurization contamination (Anon. 1988;Bishop and White 1986;Laleye and Mannen 1990;Griffiths and Phillips 1988b;Phillips et af. 1983;Phillips and Griffiths 1985).…”

Section: Pasteurized Milksmentioning

confidence: 99%

THE APPLICATION of ATP BIOLUMINESCENCE FOR the ASSESSMENT of MILK QUALITY and FACTORY HYGIENE

Bautista

McIntyre

Laleye³

et al. 1992

Rapid Methods Automation Mic

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The speed of ATP bioluminescence assays makes them very useful for assessing product quality and efficiency of sanitation at food plants. the suitability of a new method for evaluating the quality of raw milk was compared with plate count. A good correlation was obtained between the ATP method and plate count for milks with counts above 1 × 104 cfu/ml. the combination of ATP bioluminescence with preincubation procedures was investigated for predicting the shelf‐life of pasteurized milk. the best correlations were obtained when milks were preincubated at 15C for 25 h or at 21C for 25 h in the presence of an inhibitor system to prevent Gram‐positive bacterial growth. Hygiene monitoring using bioluminescence gave a better indication of surface cleaniness than conventional swab counts. the reasons for the discrepancies in a small percentage of cases are discussed.

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Section: Pasteurized Milksmentioning

confidence: 99%

THE APPLICATION of ATP BIOLUMINESCENCE FOR the ASSESSMENT of MILK QUALITY and FACTORY HYGIENE

Bautista

McIntyre

Laleye³

et al. 1992

Rapid Methods Automation Mic

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“…On arrival, samples of cream were removed and plated out on milk agar medium using a Spiral Plater (Don Whitley Scientific Ltd). The initial psychrotroph counts were determined after incubation at 21°C for 25 h (Griffiths et a!. 1980) and initial mesophile counts obtained after incubation at 30°C for 3 d. Samples of cream (10 g) were weighed into sterile 150 ml containers (Sterilin Ltd) and mixed thoroughly with 0.1 ml of an inhibitor solution containing 2 mg/ml of crystal violet, 40000 U/ml of nisin and 20000 U/ml of penicillin (Griffiths et al 1983).…”

Section: S a M P I E Smentioning

confidence: 99%

Detection of post‐pasteurization contamination of cream by impedimetric methods

Griffiths

Phillips

1984

Journal of Applied Bacteriology

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Impedimetric methods for evaluating post-pasteurization contamination and shelf-life of cream were assessed. Over 94% of the samples tested were in agreement, using selected cut-offs of 20 h for detection time measured at 21 degrees C with creams containing inhibitors for the growth of Gram positive bacteria on standard plate count agar as growth media, and 3.2 X 10(7) cfu/g for plate counts obtained on cream which had been pre-incubated in the presence of inhibitors for the growth of Gram positive organisms, and on cream stored at 6 degrees C for 7 d. Agreement between the impedimetric method and plate count was not as good if either Brain Heart Infusion or Milk Agar was used in place of Plate Count Agar in the former technique. A poor correlation was obtained between plate count methods for enumerating post-pasteurization contamination and keeping quality with impedimetric measurements on cream alone. It was possible, with a reasonable degree of certainty, to determine if cream had suffered post-pasteurization contamination within 20 h of production.

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“…Because psychrotrophs can grow at low temperatures initial small numbers can multiply on cold storage and cause spoilage of the milk. The EC test, which is based on preincubation methods such as those of Moseley (1975), involves preincubation of the milk at 6°C for five days to allow psychrotrophs to grow to detectable levels; a plate count is then performed at 21°C for 25 hours, a protocol under which psychrotrophs will outgrow other organisms (Oliveria and Parmelee, 1976;Griffiths et al, 1980). There has been criticism of the test by the UK dairy industry and work carried out by the Milk Marketing Board of England and Wales has given some evidence of poor reproducibility (personal communication), a concern which has also been expressed by others (Anon, 1989).…”

Section: Introductionmentioning

confidence: 99%

Evaluation of the incubated plate count test for pasteurized milk

Sutherland

Limond

MacDonald

et al. 1993

Int J of Dairy Tech

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Factors were examined which may influence bacterial psychrotroph counts obtained by the European Community's directed preincubation test for pasteurized milk. Studies to determine the best protocol for sampling milk indicated that the least counting error was obtained by taking at least five consecutive samples of milk. Increasing the number of replicate plates or making subsamples did not decrease counting error. When milk samples from five commercial dairies were examined over an 11 month period there was a significant difference (p < 0·001) in counts obtained over the period, but this did not seem to be a seasonal effect. The counts between dairies were not significantly different nor was the position in the pasteurization run from which the samples were taken significant. The proportion of samples which failed the test standard was 9.7% over the period. The bacterial flora isolated from plate count agar were identified; Gramnegative rods were the most common isolates. The spiral plater system was compared with the pour plate method in the preincubation test and results were found to be in close agreement, suggesting that the spiral plater could be used to improve the current official methods. Varying the time and temperature of sample preincubation was found to give significantly different results in plate counts. This suggested that preincubation conditons were critical and that variation in conditions even within the specified ranges of the test could significantly alter the bacterial psychrotroph counts obtained. Because of these results, the validity of the statutory test was questioned.

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Rapid plate counting techniques for enumeration of psychrotrophic bacteria in pasteurized double cream

Cited by 22 publications

References 12 publications

THE APPLICATION of ATP BIOLUMINESCENCE FOR the ASSESSMENT of MILK QUALITY and FACTORY HYGIENE

THE APPLICATION of ATP BIOLUMINESCENCE FOR the ASSESSMENT of MILK QUALITY and FACTORY HYGIENE

Detection of post‐pasteurization contamination of cream by impedimetric methods

Evaluation of the incubated plate count test for pasteurized milk

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