Stable Carbon Isotope Ratio Analysis of Honey: Validation of Internal Standard Procedure for Worldwide Application

Abstract

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 (C4) sugars to honeys in amounts that do not produce a δ13C value greater than -23.5%o for the mixture cannot be detected by the original 1978 SCIRA procedure. Such adulteration however is detected by ISCIRA procedure from the δ13C value of the protein contained in the honey, which shows the isotopic composition of the honey before addition of C4 sugars. Fortythree percent of 98 honeys received in the United States in 1994-1997 with δ13C < -23.5%o were suspected and found to be adulterated.

Toxic compounds in honey

“…White (1978) and Başoğlu et al (1996) used a carbon stable isotopic ratio analysis method to determine that the content levels of proline, potassium and sodium were lower in adulterated honey. Furthermore, many researchers have found honey samples that were sold in open markets were adulterated with different sugars (cane or corn) White et al, 1998;Padovan et al, 2003). Guo et al (2011) demonstrated that pure honey samples had a higher dielectric constant than adulterated honey due to a lower ash content in adulterated honey.…”

Identification, quantification and carbon stable isotopes determinations of organic acids in monofloral honeys. A powerful tool for botanical and authenticity control

“…The d 13 C values of the honey samples and extracted proteins were measured as described previously. [19,21] Proteins were extracted as follows: 10 g of honey were dissolved in 4 mL of ultra-pure water. 2 mL of 10% sodium tungstate and 2 mL of 0.67 M sulfuric acid were added to the honey solution.…”

“…[17][18][19] Stable Isotope Ratio Analysis (SIRA) is efficient for indicating the addition of C4 plant sugars (corn or cane sugars) but the addition of C3 plant sugars (beet, wheat sugars) cannot be proved by this method. [17][18][19][20] Moreover, mistakes can occur when the honey is not saturated with its own pollen, resulting in the misinterpretation of authentic honeys as non-authentic ones. [21] Furthermore, the possibility of being able to carry out the filtration of honey leads to a limitation on the use of pollen and protein markers, as pollen is the main source of proteins for bees.…”

Classification of simple and complex sugar adulterants in honey by mid‐infrared spectroscopy

“…Authenticity testing is being done using different techniques such as spectroscopic, isotopic, chromatographic and trace element analysis. Stable carbon isotope ratio analysis of honey to detect the undeclared presence of cane or corn sugars is a standard technique researched during the past 20 years (White et al, 1998). This method is time consuming and expensive.…”