Simple and inexpensive tests for rapid qualitative assessment ofthe microbiological quality of raw milk were described in a recentissue of the Journal of Food Protection. Scientists from the Food Engineering Department at KasetsartUniversity, Thailand carried out a series of tests including themonitoring of dissolved oxygen levels and changes in the colour ofraw milk with time in a slightly modified methylene blue test using16 ppm of dye concentration.
The initial bacterial population in raw milk determined bystandard plate count could be estimated with coefficients ofdetermination (r2) of about 0.697 and 0.613 from the respectivenormalized voltage outputs of the dissolved oxygen probe andlight-sensing probes at selected time intervals in less than 1h.
However, the researchers report, a comparison of experimentaland estimated initial bacterial populations in raw milk showedcorrelation coefficients (r) of about 0.754 and 0.616 for thedissolved oxygen probe and light-sensing probe, respectively. They concluded that the results clearly indicated the potential andneed for improving such empirical models for grading raw milk withboth types of probes. Full findings are published in the November issue of the Journal ofFood Protection: Vol. 64, No. 12, pp. 1996-2000.