96-12 |
An electric conductance method for estimating titratable acidity in fruit juice |
J. S. B. WU and C. S. Wang. Graduate Institute of Food Science & Technology, National Taiwan University, PO Box 23-14, Taipei, Taiwan Titratable acidity in fruit juice is commonly evaluated in the laboratory using a tedious titration process. Some researchers proposed to dilute the juice and to read the electric conductance as a way to estimate the titratable acidity. The method they proposed could be easy and quick, but inaccurate for applying to juices with different organic acid profiles as they differ in the extent of ionization. The purpose of this study was to investigate the relations between titratable acidity and electric conductance in juice and to develop a simple and accurate new method for predicting titratable acidity from electric conductance measurement in various fruit juices. The electric conductance in a model solution, which simulates juice, was evaluated theoretically based on ion mobility and chemical equilibrium equations. Experiments were performed to check the theoretical data. Equations for estimating titratable acidity from electric conductance were established. A method that involves the addition of equal volume of 0.2N NaOH to the model solution was developed, and its accuracy was reconfirmed in various juices. The results showed that the theoretical electric conductance values are close to the experimental ones. The coefficient of determination between electric conductance and titratable acidity in various juices increased to 0.96 by the addition of NaOH solution. A simple and accurate method for estimating the titratable acidity in various fruit juices by electric conductance measurement was developed. This method can be referred to construct a kit for field estimation of the titratable acidity in juice.
Session 96, Fruit & Vegetable Products
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