The Relationship of Electrical Conductivity with pH, Acidity and Total Microbial Count in Raw Milk

Electrical conductivity (EC) is the ability to conduct electricity which is expressed as micro Siemens per centimeter (µs/cm). The conductance of the milk is attributed mainly to its salts content especially Na، K and Cl ions. Since measuring the milk’s EC is a rapid and inexpensive method for determining of the milk quality، therefore correlation between EC with pH، acidity، and total microbial count (TC) in raw milk was studied in order to assess the freshness of milk in this research. In a pilot study، using skim milk، pH، acidity، and TC were changed and EC measured at 25ºc. Then a total of 200 samples of whole milk were obtained from the receiving platform of a dairy plant in Tehran. In one trial 100 samples of whole milk were examined for pH، acidity and TC. Also EC was measured in different temperatures of milk samples at the time of the analysis. In the second 100 samples of whole milk، pH، acidity and TC determined and EC measured at 25ºC. According to the results obtained from the pilot study (with 10 repetition)، increasing the pH caused a decrease in EC and vice versa (P0/05). No significant correlation was found between EC with pH، acidity and TC in other trials (P>0. 05). It seems many factors may affect the EC in raw whole milk. Therefore measuring EC solely can not determine the milk quality.