1976 Volume 23 Issue 6 Pages 262-267
A new rapid and convenient method was developed for measuring sourness of food based on conductometry.
Comparing the difference of the electrochemical behavior between weak electrolyte, organic acid, and strong one, potassium chloride, it was found that the hydrogen ion concentration dissociated from organic acid could be accurately estimated in the presence of strong electrolyte ions. An equation(1)is set up between the content of organic acid in sample solution(y), and the specific conductance of the properly diluted solution(x). Where, the proportionality constant(a) is associated with the nature of organic acid, closely related to the dissociation constant of the acid,
y=ax+b (1)
and(b)is the constant due to the content of the strong electrolytes in the sample solution.
For Citrus fruits, the equation(2)was obtained.
y(% as citric acid)=0.02678x-0.4641, r=0.998 (2)
In this case, the fruit juice was diluted 300 times with water and the specific conductance(μmho·cm-1)was measured at 25°C. This equation was applicable to the Citrus fruits containing 0.5-3% organic acid(as citric acid content)and independent of variety, strain, region and ripening period of the fruits.
