Comparison Between Standard Methods Procedure and a Surface Plate Method for Estimating Psychrophilic Bacteria in Milk1

Abstract

Summary Psychrophilic population levels were determined by Standard Methods procedure (1) and a surface plate method. Thirty-one samples of raw milk, 47 samples of commercial pasteurized milk, and 94 samples of milk containing pure cultures of selected psychrophiles were used in the comparisons. A statistical evaluation of the results indicated counts obtained by the surface plate method after incubation of the plates for five days at 6C were equivalent to counts obtained by the standard procedure after incubation for 7–8 days at 6C. Colonies on the surface plates were larger, more uniform in size, and consequently easier to count than those on poured plates. Also, enhanced pigmentation and more characteristic colonial morphology was observed with surface plates. Approximately 80% of the pinpoint colonies appearing on the poured plates after 8 days and on the surface plates after 7 days of incubation at 6C were Gram-positive cocci indicating the emergence of colonies of organisms not considered to be psychrophilic species important to the shelf life of milk.

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

“…Further differences between 6OC-14 d counts obtained after inoculation by the pour plate method and the Spiral Plate Maker may result from the contrasting availability of oxygen; anaerobic conditions may prevail in pour plates resulting in poor or arrested growth of psychrotrophs. This suggestion is supported by reports that the error and variability of counting methods are less for surface plating methods (Snyder, 1947), and also by the observation that growth occurs faster on plates which have undergone surface inoculation (Punch & Olson, 1964). The correlation between 21OC-25 h counts obtained by pour plate and 6OC-14 d counts by Spiral Plate Maker is higher than that for 21OC-25 h counts by Spiral Plate Maker and 6OC-14 d counts by pour plate (Table 3), again suggesting that the 6OC-14 d count by the pour plate method may underestimate the number of psychrotrophs present.…”

Risk Factors Associated with Prevalence of Brucellosis and Bacteria in Fermented Cow Milk Obtained from Kajiado Central Sub-County in Kenya

“…The microbiological quality of fermented milk product was further assessed by spread plate method [19]. The Violet Red Bile Glucose Agar was used to detect and enumerate Enterobacteriaceae in fermented milk [19].…”

“…The microbiological quality of fermented milk product was further assessed by spread plate method [19]. The Violet Red Bile Glucose Agar was used to detect and enumerate Enterobacteriaceae in fermented milk [19]. Briefly, 1 ml of the serial dilution was transferred to petri dishes using two plates for each dilution.…”

Aplicação do cloreto de trifeniltetrazólio no teste de limite microbiano em medicamentos e cosméticos

“…Nesse caso, os autores recomendam a contagem de cada ca que parece ser proveniente de uma fonte, como uma colÔnia. Em estudo comparativo, as contag efetuadas por esse método forneceram resultados com carga contaminante maior aquele de semeadura em profundidade, para algumas amostras36, 44,197,203. TYBRING 142 testaram 421 amostras de solução de uso oral, emprega teste preliminar.…”