... is measured by the rate of microbial respiration, which is indicated by a fall in pH. A fall in pH is due the accumulation of lactic acid. The accumulation of lactic acid occurs when the density of bacteria increases through cell multiplication. As the density of bacteria increases the demand for oxygen increases, once all the oxygen is used up the conditions turn anaerobic, thus resulting in the production of lactic acid. Rate of microbial respiration in milk can be measured by measuring the rate of the colour change of rezazurin dye at 37°c and by the accumulation of lactic acid which is indicated by a fall in pH Apparatus Pasteurised milk i.e. samples of: -Full fat -Skimmed and -Semi-skimmed Sterilised milk i.e. samples of: -Ultra Heat Treated milk Rezazurin dye Water bath Test tubes Pipette Measuring cylinder Thermometer Rubber stopper Timer pH meter Method Measure 10 cm of each sample of milk, both the refrigerate samples and the room temperature samples, in a measuring ...

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