[Quantitative Evaluation of Sorbic Acid Isomers in Preservative Products Used as Food Additives by Single-Reference High-Performance Liquid Chromatography].

Abstract

Sorbic acid and its salts, listed as Sorbic Acid (SOA) and Potassium Sorbate (SOK) in the current Japan's Standard and Specification for Food Additives (JSFA), are widely used as food additive preservatives. In the JSFA monographs, titration is used as a quantitative method, and the SOA or SOK contents are quantified as sorbic acid or its salt, including their stereoisomers. Although sorbic acid can be converted into its stereoisomers under certain conditions, the actual isomer content in food additive products has not been accurately analyzed on the JSFA titration assay. In this study, we used a previously developed single-reference high-performance liquid chromatography (SR-HPLC) method to accurately analyze sorbic acid and its three isomers, enabling the individual quantification of these components in commercial SOA and SOK products used as food additives. Analysis of five lots of the SOA products and eight lots of the SOK products revealed that the 2E,4Z-isomer was the predominant stereoisomer, with contents ranging up to 0.011% in SOA and up to 0.15% in SOK. Thus, the stereoisomer content was extremely low compared with that of sorbic acid or potassium sorbate. The total contents of sorbic acid and the isomers in SOA or those of potassium sorbate and the isomers in SOK obtained using SR-HPLC were equivalent to those determined using the JSFA titration method. This suggests that the SR-HPLC method is a viable alternative to the titration-based quantitative method, enabling simultaneous quantification of stereoisomers in food additives. These findings demonstrate the utility of SR-HPLC as an alternative assay for regulatory and quality-control purposes, offering improved chemical specificity and stereoisomeric profiles compared with conventional titration methods.