Optimized Extraction Method of Acetic Acid in Vinegar and Its Effect on SNIF-NMR Analysis to Control the Authenticity of Vinegar

• Published in: Food and bioprocess technology 2013-08, Vol.6 (8), p.2202-2206
• Main Authors: Ko, Wen-Ching, Cheng, Ju-Yun, Chen, Po-Yen, Hsieh, Chang-Wei
• Format: Article
• Language: English
• Subjects: Acetic acid; Acids; Agriculture; Biotechnology; Chemistry; Chemistry and Materials Science; Chemistry/Food Science; Communication; Design of experiments; Deuterium; Diethyl ether; Distillation; Ethyl acetate; Experimental design; Food; Food Science; Fractionation; Isotope fractionation; NMR; Nuclear magnetic resonance; Orthogonal arrays; Solvents; Vinegar
• ISSN: 1935-5130; 1935-5149
• DOI: 10.1007/s11947-011-0766-5

Site-specific natural isotope fractionation by nuclear magnetic resonance (SNIF-NMR) is an accurate method for examining food adulteration. SNIF-NMR can be used to determine the ratio of deuterium to hydrogen (D/H) of a specific molecule position. Because the quantity of D differs between synthetic and fermented acetic acids, the method can be used to accurately monitor food adulteration. However, the effect of pretreated food on the results of SNIF-NMR has rarely been discussed. We present an extractive distillation method to increase the purity of acetic acid for fractionation; we used an orthogonal array experimental design to determine the optimal extraction conditions. We discuss the influence of extract solvents and sample concentration on the (D/H) CH3 values calculated from the NMR results. The optimal conditions for extracting acetic acid were found to be a sample-to-solvent ratio of 1:1, seven extractions, and an extraction time of 15 min. The extraction rates for acetic acid were 93.65% and 80.57% when ethyl acetate and diethyl ether, respectively, were used. The acetic acid concentration of the ethyl acetate- and diethyl ether-extracted samples was further improved by distillation from 5 g/100 mL to 33.84 and 51.65 g/100 mL, respectively.