Detection of Abnormal Milk with Impedance Microbiology Instrumentation

Abstract

Mastitic milk was detected by obtaining conductance measurements using an impedance microbiology Bactomatic 120 SC instrument. Conductance readings separated normal and abnormal milks after 30 min at 25°C when readings differed by more than 2 to 3% and exceeded the variance among instrument module wells. Samples blended from four quarters of a cow indicated milk from one quarter was abnormal if the salt level in the abnormal quarter raised the blend conductivity above that of normal samples and variance among the wells. Either solid or liquid substrates that contained stimulants could be used to accelerate bacterial acid production or reduce impedance detection times and did not affect the ability to detect abnormal milk. However, measurements varied with the volume of sample in the well, suggesting that fixed 1-ml liquid volumes of milk be used. Such volumes would allow detection of abnormal milk and bacterial load on the same sample.

Impedimetric method for estimating the residual activity of freeze-dried Lactobacillus delbrueckii ssp. bulgaricus

“…Research in the dairy industry has primarily focused on the application of impedimetric methods for the detection of abnormal milk (Khayat & Richardson, 1986), for the estimation of total, mesophilic and psychrotrophic counts of bacteria in raw milk (Firstenberg-Eden & Tricarico, 1983;Nieuwenhof & Hoolwerf, 1987), and for the selective enumeration of specific yoghurt bacteria (Pirovano et al, 1995). Impedimetric assays are regularly performed by monitoring impedance detection time (IDT).…”

Series quartz crystal sensor for remote bacteria population monitoring in raw milk via the Internet

“…4(B), there was only a 20 Hz difference when the concentration of bacteria in solution increased from 10 2 to 10 7 CFU ml −1 (six logs). This phenomenon may be explained by the observation that all curves cannot be expected to originate at the same frequency because many parameters could affect the initial frequency once the raw milk was placed into the reaction cell, including temperature, initial ion concentration (Yoa et al, 1994b), somatic cell (Khayat and Richardson, 1986) and/or the separation of fat from the raw milk. Although the detection system used in this study was only set up once and was reused for all measurements of raw milk (not dilutions), the differences in fundamental frequency between each experiment were not associated with the concentration of bacteria in solution.…”

“…Since it is unlikely that cells died immediately and protein could not be adsorbed this fast, the rapid drop of frequency in the initial period might also be attributable to other parameters, e.g. the presence of somatic cells (Khayat and Richardson, 1986) and/or the separation of fat from the raw milk. The frequency drop continued throughout the period of bacterial growth but with a slower rate.…”

“…In the preliminary experiment, a greater frequency drop was observed when the solutions had higher initial bacteria levels. However, many parameters could affect the frequency profile in the initial period once the raw milk was placed into the reaction cell, including temperature, initial ion concentration (Yoa et al, 1994b), somatic cell (Khayat and Richardson, 1986) and/or the separation of fat from the raw milk. The frequency fluctuated rapidly and all curves cannot be expected to originate at the same frequency when the solutions had more initial bacteria.…”

ESTIMATION of MICROBIAL NUMBERS FROM PURE BACTERIAL CULTURES and FROM MINCED BEEF SAMPLES BY REFLECTANCE COLORIMETRY WITH OMNISPECTM 40001

“…Recent developments in rapid analytical methodology are aimed at estimating the total microbial load as a hygiene parameter, predicting spoilage or shelf-life or detecting and enumerating specific pathogenic or toxigenic microorganisms and their metabolites. Time and labor saving techniques or instruments that enumerate microorganisms in quality assurance programs include impedimetry (Bulte and Reuter 1984;Firstenberg-Eden 1986; Khayat and Richardson 1986;Schaertel et al 1987), turbidimetry (Jorgensen and Schulz 1985;Mattila 1987; Mattila and Alivehmas 1987;Schulz et al 1988;Haikara et al 1987;Manninen et al 1990; Haikara et al 1990), radiometry (Caslow et al 1974;Lampi et al 1974), microcalorimetry (Gram and Sogaard 1985), microcolony counting (Rodrigues and Kroll 1988), ATP-luminometry (Bulte and Reuter 1985;Kennedy and Oblinger 1985), gas liquid chromatography (Jackson and Kempton 1973;Gverzoni et al 1987), enzyme immunoassays (Swaminathan d al. 1985; Ibrahim and Lyons 1987), and DNA probes (Fitts 1985).…”