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Abstract
Locust bean gum (E-410) and guar gum (E-412) are high molecular weight galactomannans used by the food industry as versatile food additives. The compounds, although chemically closely related, do not have the same functional properties when used in foods, and the substitution or unadvertised addition of either could change the desired qualities of the product. Analytical discrimination between E-410 and E-412 is technically difficult since they only differ in their galactose: mannose ratios, being 1 : 4 and 1 : 2 for locust bean gum and guar gum, respectively. A qualitative DNA-based method is reported for the authentication of additives E-410 and E-412 in finished food products (ice cream, dehydrated desserts, milk derivatives, dehydrated soups, salad dressing, marmalade and meat) from small quantities of food. DNA sequences from the nuclear ribosomal spacers of Ceratonia siliqua and Cyamopsis tetragonoloba, the plant sources of E-410 and E-412, respectively, were used to design polymerase chain reaction primers specific for each additive (PA23/PA21 and PG22/PG21). Twenty-two foods were analysed for the presence of E-410 and E-412 additives by this single-step polymerase chain reaction-based method. Positive DNA amplifications with the E-410 and/or E-412 primers were obtained in all 19 samples reported to contain either additive.
Acknowledgements
Work was supported by research grants (AGL2000-1397-C02-02, PTR 19995-0461-OP) to V. J. B., S. A. and J. A. R. The authors thank G. Bibiloni (Carob SA, Balearic Islands) for providing several locust bean and guar samples and for continuous support thorough the study, and the Servicio de Secuenciación del Centro de Investigaciones Biológicas for DNA sequencing. M. U. was supported by a predoctoral fellowship from IMEDEA-CSIC.