Investigating C-4 Sugar Contamination of Manuka Honey and Other New Zealand Honey Varieties Using Carbon Isotopes

Abstract

Carbon isotopes (δ(13)C honey and δ(13)C protein) and apparent C-4 sugar contents of 1023 New Zealand honeys from 15 different floral types were analyzed to investigate which New Zealand honey is prone to failing the AOAC 998.12 C-4 sugar test and evaluate the occurrence of false-positive results. Of the 333 honey samples that exceeded the 7% C-4 sugar threshold, 324 samples of these were New Zealand manuka honey (Leptospermum scoparium, 97.2% of all fails found in the study). Three monofloral honeys (ling, kamahi, and tawari) had nine samples (2.8% of all fails found in the study) with apparent C-4 sugars exceeding 7%. All other floral types analyzed did not display C-4 sugar fails. False-positive results were found to occur for higher activity New Zealand manuka honey with a methylglyoxal content >250 mg/kg or a nonperoxide activity >10+, and for some ling, kamahi and tawari honeys. Recommendations for future interpretation of the AOAC 998.12 C-4 sugar method are proposed.

Antimicrobial properties and isotope investigations of South African honey

“…Interestingly, perceived unadulterated New Zealand manuka honeys routinely fail the AOAC adulteration test, especially manuka honeys with high antimicrobial activity (Rogers et al 2010(Rogers et al , 2013 and similar situations have been reported in other European honeys (White 1992;Cotte et al 2007). To date, the factors underpinning this phenomenon are largely unexplained; however, work done by Rogers et al (2010Rogers et al ( , 2013Rogers et al ( , 2014a has clearly shown that in many cases the current official methods (AOAC, 1999) are not sufficiently sensitive for C 4 level detection in some honeys and have called for a revision to the accepted protocols.…”

“…Further reasons for the possible misclassification of honeys as ‘adulterated’ may result from the improper storage of honey at high temperatures, that is, > 27·0°C (Rogers et al . ,b). Although in this study all honeys were stored at ~20°C, the possibility of higher storage temperatures prior to arrival at the laboratory cannot be excluded.…”

Authenticity and geographic origin of global honeys determined using carbon isotope ratios and trace elements

“…Moreover, the manuka samples had δ 13 C honey values of −25.13‰ and −25.58‰ respectively, which is inconsistent with Rogers et al . 45 who suggested that δ 13 C values in authentic manuka honey should not be less than −24.7‰. Therefore, the multiple criteria used here to assess honey authenticity indicates that both the manuka honey samples analysed were non-authentic products.…”

Determination of honey adulteration with beet sugar and corn syrup using infrared spectroscopy and genetic‐algorithm‐based multivariate calibration

“…Furthermore, gas chromatography 6,7 and high-performance liquid chromatography [8][9][10][11][12][13] are also used to detect adulterated honey samples. Moreover, carbon isotope ratio (C 12 /C 13 ) analysis [14][15][16][17][18][19][20] (IR-MS) is used as a standard technique to detect the presence of artificial sweeteners in honey. Although there has been a great deal of study in the literature, IR-MS analysis requires more elaborate sample preparation techniques and therefore takes a lot of time.…”