<b>PSYCHROPHILIC BACTERIA IN RAW AND COMMERCIALLY PASTEURIZED MILK</b>

Thomas, S. B.; Sekhar, C. V. Chandra

doi:10.1111/j.1365-2672.1946.tb04046.x

Cited by 16 publications

(6 citation statements)

References 3 publications

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“…I n commercially pasteurized milks only 37% of the samples exceeded this figure. These workers confirm the findings of Thomas & Sekhar (1946) that laboratory pasteurized samples contained no psychrophilic organisms. There appeared to be a broad general agreement between psychrophilic count and keeping quality (the clot-on-boiling test at 3-5').…”

Section: (F) Bacteriological Testing Aspectssupporting

confidence: 87%

“…Both raw and commercially pasteurized milk may contain large numbers of psychrophilic bacteria, but it has been reported that laboratory-pasteurized samples (63" for 35 min.) failed to produce any colonies in 31 days a t 3-5" (Thomas & Sekhar, 1946). It has also been found in India that no psychrophilic organisms are thermoduric, and the psychrophilic plate count has been proposed as an index of plant contamination (Sekhar, 1951), but as the test takes 31 days it is unlikely to supplant, the well-recognized and efficient coli-aerogenes test for this purpose.…”

mentioning

confidence: 99%

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The Effect of Cold on Micro‐organisms in Relation to Dairying

Davis

1951

Proceedings of the Society for Applied Bacteriology

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Section: (F) Bacteriological Testing Aspectssupporting

confidence: 87%

mentioning

confidence: 99%

The Effect of Cold on Micro‐organisms in Relation to Dairying

Davis

1951

Proceedings of the Society for Applied Bacteriology

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“…Thomas (1955) had previously reported that c. one third of 93 strains of K . cloacae, isolated a t 30" from farm milk supplies, produced proteolytic reactions in litmus milk incubated a t 22" for 72 h. Thomas, Griffiths & Foulkes (1960) also observed quite significant increases in the number of coli-aerogenes organisms in several samples of commercially pasteurized milk stored at 7" for 72 h, e.g. initial counts of < l/ml a t 30" increased to 103-104/ml after refrigeration.…”

Section: Pasteurized Milkmentioning

confidence: 76%

Psychrotrophic Coli‐aerogenes Bacteria in Refrigerated Milk: A Review

Panés¹,

Thomas²

1968

Journal of Applied Bacteriology

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“…There has been much investigation of the time of incubation at 5" which is necessary to give maximum psychrotrophic colony counts. Thomas & Chandra Sekhar (1946) reported that the average counts in 14 days a t 3-5" were 8 x those recorded in 7 days. Incubation a t 5" for 7 days frequently results in colonies so small as to make counting difficult, whereas after 10-14 days the colonies are larger and easier to count.…”

Section: Development Of Standard Methodsmentioning

confidence: 96%

Methods of Assessing the Psychrotrophic Bacterial Content of Milk

Thomas¹

1969

Journal of Applied Bacteriology

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Introduction . Development of standard methods . (a) Incubationat 10" . (b) Incubation a t 5" .(c) Incubation a t 7" . Standard reference method . . Technique of examination . (a) Age of raw milk on examination . (b) Age of pasteurized milk on examination . (c) Effect of sublethal heat treatment .(d) Diluent and preparation of dilutions . (e) Temperature of agar medium a t pouring .(f) Temperature variation in refrigerator incubators . (a) Violet red-bile agar . (b) Crystal violet agar (c) Penicillin agar . (d) Other selective media . (e) Oxidase positive colony count Selective media for Gram negative bacteria . Indicator agar media . Preliminary incubation of plates . Surface plating methods . Total colony count of refrigerated milk The Moseley method . Screening and quick methods . (a) Frost little plate method. . -. (b) Microcolonies in the drop plate method . (c) Microcolonies on membrane filters . Conclusions . Acknowledgments . References . PAQE 270 271 272 272 272 273 274 2 74 275 2 76 276 277 277 277 278 278 280 281 281 283 2 84 285 286 288 289 2 89 290 290 290 291 291 SUMMARY. The vaiious methods used for the determination of the psychrotrophic bacterial content of refrigerated milk are reviewed and assessed. A standard reference method, involving incubation of poured plates at 7" for 10 days, is recommended for the determination of psychrotrophic colony counts for investigational purposes. Many ingenious techniques, based on media selective for Gram negative bacteria, with incubation a t higher temperatures and shorter times are described and appraised. A simple procedure which would provide a more rapid assessment of the number of active milk spoilage types of psychrotrophs is needed for routine purposes, and i t is suggested that the enumeration of microcolonies by the drop plate or membrane filter methods with incubation at 7" for 72 h would provide a suitable technique for this purpose.Incubation of plates at 25" for 5 days is recommended as a standard reference method for determining the total colony count of bacteria in refrigerated milk, but for routine purposes where large numbers of milk samples are being examined incubation at 28-30" for 3 4 days would provide a sound enough estimate.

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PSYCHROPHILIC BACTERIA IN RAW AND COMMERCIALLY PASTEURIZED MILK

Cited by 16 publications

References 3 publications

The Effect of Cold on Micro‐organisms in Relation to Dairying

The Effect of Cold on Micro‐organisms in Relation to Dairying

Psychrotrophic Coli‐aerogenes Bacteria in Refrigerated Milk: A Review

Methods of Assessing the Psychrotrophic Bacterial Content of Milk

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