Abstract
A novel method for determining the titratable acidity of a pH adjuster using a flow-injection analysis system with electrochemical detection (FIA-ECD) has been developed. The detection is based on the voltammetric reduction prepeak of vitamin K3 in the presence of acids. The prepeak current is proportional to the equivalent concentration of the acids. A pH adjuster (DP-7L) for boiled noodle to prevent proliferation of bacteria, which contains lactic, phosphoric, and gluconic acid was used as an example in this study. Using FIA-ECD, the peak current height was proportional to the concentration of DP-7L between from 0.0012% to 0.01% (r = 0.997). The relative standard deviation (RSD) of DP-7L at 0.0075% was determined to be 3.8% (n = 5). The result obtained from the proposed method agreed well to with that from the titration volume of a NaOH standard solution by neutralization titration (r = 0.989). Thus, the titratable acidity of the DP-7L pH adjuster can be determined by the present method. An auto analyzer being incorporated with the FIA-ECD would be useful for monitoring the titratable acidity of pH adjusters in the manufacturing process of boiled noodles.
