Yogurt Application Notes

Benefits of IQ ISFET pH meter:

	Rugged
	Portable
	Easy to use
	Easy to clean

Yogurt is a popular dairy product made from concentrated milk fermentation. The quality of the product depends on production control of lactic acid formed by fermentation. Lactic acid provides the tart flavor and the destabilization of milk protein forms the gel structure. pH measurement monitors lactic acid production and aids in the quality control of yogurt’s ingredients.

The production of yogurt starts by selecting and blending the correct ingredients, like milk concentrate and other dairy products, thickening agents, sweeteners and fruit. These ingredients add the correct solids, flavor and viscosity. The blend of ingredients is homogenized at high pressures to prevent fat separation and cause solid dispersion. Next, the temperature is raised to destroy harmful microorganisms and restructure protein to help with the viscosity. After cooling, the smarter culture, which contains a particular lactic fermentation bacteria, is added to the mix. Incubation then takes between 4 and 11 hours.

During fermentation, lactose (milk sugar) converts to lactic acid, decreasing the pH values to a range of 4.25 to 4.5. Bacterial action is stopped by rapid cooling at the right lactic acid level. pH meters are the best instrumentation to determine the completion time of fermentation. Incorrect pH levels can lead to discoloration, excessive free whey and excess or insufficient tartness.

The IQ ISFET Benchtop/ Portable pH meter will change the way you measure pH. The durable silicon chip sensor eliminates fragile glass bulb sensors and the built-in reference and temperature compensation make testing easier. The sensor can successfully be used in a wide temperature range from 0° C to 60° C with consistent accuracy and fast response times. To learn more details about IQ ISFET pH meters, click here.

TESTING TIPS

Perform the test on sample by putting the probe in the sample, gently stirring for a few moments to be sure no air bubble is trapped on the sensor surface.

Note: In 0.01 resolution, the endpoint time is about twice that of the 0.1 resolution. If you don’t need 0.01 precision, put the meter in 0.1 resolution to speed response time. The Model IQ240 is equipped with 0.001 resolution. This research grade resolution is not required in most dairy applications. Be sure not to use 0.001 resolution or unnecessary time will be spent reaching an endpoint reading.

Rinse probe with a jet of distilled or dionized water from a right angle squirt bottle. Point the stream right at the sensor to effectively remove any sample left on the probe.

Protein is the biggest single problem in pH testing of dairy applications. In glass electrodes it gets in the glass and is very difficult to remove. Traditional glass electrode manufacturers recommend HCl acid dips or pepsin solutions. In the case of silicon chip sensors, the proteins still attach to the sensor, but the sensor is non-porous so proteins can be removed without degradation of the sensor. The best approach is a 15 minute soak in our PCS 50 Probe Cleaning Solution. After this soak, use a gentle rub of the sensor surface (the recessed blue/green spot near the end of the probe) with a wooden toothpick. Rinse well, then recalibrate. It is not necessary to use the PCS Probe Cleaning Solution unless response time slows.