In the food and beverage (F&B) industry, in particular in dairy applications, there is a continued trend towards in-line pH measurement using non-glass sensors. Several customers who produce yogurt, recently successfully finalized tests with METTLER TOLEDO's ISFET pH electrode, InPro 3300. Their common goal was to establish process control in yogurt production. One customer even utilized an ISFET system to find methods for the detection of infection with phages at an early stage of the production process.
When producing yogurt, in a first step all potential additives such as milk powder, protein, and sugar are added to the milk. After subsequent homogenization, the resulting mixture is pasteurized in order to avoid contamination with pathogenic microorganisms. It is then cooled down to approximately 40…45° C and inoculated with a culture of bacteria, most commonly a mixture of lactobacillus bulgaricus and streptococcus thermophilus. These are responsible for the fermentation of the milk sugar (lactose) and the formation of lactic acid, which results in a decrease of pH from 6.6 pH units to 4.4…4.6 pH units within the process time of three to six hours. When the desired final pH value has been reached, the product is stirred and cooled down in order to stop activity of the bacteria..…..
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