Impedance Measurement of Changes in Activity of Lactic Cheese Starter Culture After Storage at 4°C

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Abstract
Impedance, titratable acidity, and change in pH were used to measure activity of lactic cheese starter culture held up to 7 d at 4.degree. C. The impedance microbiologgy, as quantified by the impedance detection time method, provided an activity estimate within 37 to 53 min, and the results were similar to the activity measurements using titratable acidity (3.5 h) and change in pH (2.5 h). The impedance detection time, titratable acidity, and pH activity tests showed that the culture activity decreased most rapidly between 2 and 5 d. The slope of the impedance curve, 15 min after the impedance detection time, decreased as storage time increased with the sharpest decrease occurring during the first 3 d of storage.