Stable carbon isotope ratio analysis of honey: validation of internal standard procedure for worldwide application

Stable carbon isotope ratio analysis (SCIRA) of honey for undeclared presence of cane or corn sugars has been available for 20 years. Its use with domestic and imported honeys is reviewed. Six years of data from the Internal standard isotope ratio analysis (ISCIRA) method support its worldwide validity for honey analysis. The ISCIRA database of pure honeys has been increased from 64 U.S. samples to 224 by addition of data from Germany, United Kingdom, Mexico, Italy, and Spain. ISCIRA analyses of 131 commercial honeys from the United States, Mexico, and Spain found that 17 are adulterated. Analyses of 303 Chinese honeys proves that they should have carbon isotope values similar to honeys from other areas, contrary to claims that the observed differences are intrinsic because of the variability of environmental conditions and of plants used in honey production in China. Addition of corn or cane (C 4 ) sugars to honeys in amounts that do not produce a δ 13 C value greater than -23.5‰ for the mixture cannot be detected by the original 1978 SCIRA procedure. Such adulteration however is detected by ISCIRA procedure from the δ 13 C value of the protein contained in the honey, which shows the isotopic composition of the honey before addition of C 4 sugars. Forty-three percent of 98 honeys received in the United States in 1994-1997 with δ 13 C < -23.5‰ were suspected and found to be adulterated.