Prediction of the keeping quality of pasteurized milk by the detection of cytochrome c oxidase

Abstract

The keeping quality (KQ) of pasteurized milk samples stored at 5 degrees C and 10 degrees C was satisfactorily predicted after 18 h pre-incubation with 0.05% benzalkonium chloride at 20 degrees C, by estimating the numbers of Gram-negative psychrotrophic bacteria using the simple, cheap and rapid (5 min) assay of cytochrome c oxidase. Correlation coefficients for the relationship between cytochrome c oxidase activity at 20 degrees C and KQ at 5 degrees C or 10 degrees C of -0.89 and -0.84 respectively were obtained. The method correctly predicted the KQ of more than 89% of the samples of pasteurized milk. The assay was not satisfactory for use on samples after pre-incubation at 30 degrees C.

Prediction of the shelf‐life of pasteurized milk at different storage temperatures

“…Probably the most successful have relied on a pre-incubation procedure in the presence of inhibitors for Gram-positive bacteria by enumeration by any one of a number of techniques (e.g. Griffths et al 1984;Phillips & Griffiths 1985;Kroll & Rodrigues 1986). However, these techniques have usually been related to shelf-life at a single storage temperature.…”

“…In the UK, pasteurized products are stored under a wide range of temperatures and an indication of the ability to withstand temperature abuse is desirable. Some work has been done to correlate the preincubation counts of pasteurized products with shelf-life at both 5°C and 10-1 1°C (Rodrigues & Pettipher 1984;Kroll & Rodrigues 1986).…”

The Influence of Biotechnological Developments on Cheese Manufacture

“…The nitrate reduction test was used in New Zealand for some years and probably does have some value for screening raw milk samples for high levels of psychrotrophs or coliforms (Luck, 1982;Kroll, 1989). Assays of bacterial cytochrome c oxidase or catalase have been suggested as quick, simple methods for assessing psychrotrophs in pasteurized milk, but may also have value for raw milk (Kroll and Rodrigues, 1986;Phillips and Griffiths, 1987;Kroll, Frears and Bayliss, 1989). Similarly, microbial lipases and proteases are known to affect the quality of liquid milk and milk products (Fairbairn and Law, 1986;Stead, 1986).…”

Methods of Rapid Microbiological Assay and Their Application to Pharmaceutical and Medical Device Fabrication

“…However, they are not always suited to pharmaceutical and medical devices due to the large difference in the number of contaminating microorganisms. Their procedures of detection may be direct, in which individual microorganisms or populations of organisms are directly observed, or indirect, whereby microbial metabolism, metabolites, or components can be Pettipher, 1983;Hutcheson et al, 1988;Rodrigues and Kroll, 1988;Rodrigues and Kroll, 1990;Diaper and Edwards, 1994;Nebe-von Caron et al, 1998;Newby, 2000;Van Poucke and Nelis, 2000;DeCory et al, 2005, electrical resistance Baynes et al, 1983Owens and WacherViveros, 1986;Silley and Forsythe, 1996;Newby, 2000 , enzyme monitoring Kroll andRodrigues, 1986;Watling and Leech, 1996;Newby, 2000 , Limulus amoebocyte lysate Jorgensen and Alexander, 1981;Bussey and Tsuji, 1984;Baines, 2000, nucleic acid probes Bauters et al, 1999Jordan, 2000;Newby, 2000;Dunsmoor et al, 2001;Jimenez et al, 2001;Serin et al, 2005;Chaieb et al, 2007;Zuluaga et al, 2009 , phage-interaction technology Wolber andGreen, 1990;Turpin et al, 1993;Stewart et al, 1996;Stewart et al, 1998;Mole et al, 1999;Wu et al, 2001 , andcarbon dioxide radiometry Cutler et al, 1989 . In addition to the methods summarized in Table 2, other techniques have been inve...…”