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This review (open access) presents a comprehensive summary of the principles and recent advancements in the application of stable isotope techniques for authenticity assessment. It examines their use in detecting fraud (e.g., identifying edible alcohol, exogenous water, carbonylation, and trace compounds), vintage identification, and geographical origin determination across various alcoholic beverages, with a particular focus on wine, Chinese baijiu, and beer.   It cites over 100 publications from the past 15 years.

The authors conclude that stable isotope analysis is a powerful tool for verifying the authenticity of alcoholic beverages, offering effective solutions to combat counterfeiting, mislabeling, and adulteration. They recommend that future studies should focus on understanding the ecological, biological, and hydrometeorological factors influencing isotope signatures and develop advanced multi-isotope and chemometric approaches to improve reliability. Expanding global databases and integrating emerging technologies such as artificial intelligence (AI) and machine learning will further enhance the effectiveness and accessibility of stable isotope techniques, ensuring safer and higher-quality alcoholic beverages for consumers worldwide.

Photo by Ibrahim Boran on Unsplash

This study (open access) examined how variations in δ²H and δ¹⁸O values of cooking water affect the isotopic fingerprint of noodles with different gluten-to-starch formulations.

Eight differently formulated noodles were boiled using waters with six distinct isotopic compositions ranging from of −160‰ to +50‰ for δ²H and from −22.9‰ to +99.9‰ for δ¹⁸O, respectively.

It was found that formulation and water isotopic composition significantly affected the δ²H in cooked noodles. Additionally, the δ²H values of noodles changed with the isotopic signatures of the cooking water. Conversely, δ¹⁸O in the noodles remained stable despite boiling processing and was also not changed by the water's isotopic signature.

The authors derived an equation for determining the exchange factor (f(H)ex) between noodles and cooking water. The fraction of hydrogen atoms in different noodles for exchange was highest at 19.3% in noodles with the formulation of 45:55(gluten-to-starch) and the lowest at 11.1% in noodles with 100% gluten.

The authors conclude that cooking water systematically alters the isotopic signatures of noodles, underscoring the necessity of considering this type of effect in food authentication and traceability practices.

Photo by M. W on Unsplash

There is a price premium for tomato sauce labelled as “natural” or “no artificial additives”.  Citric acid (E330) is a common component of tomato sauces, and the cheapest form is biosynthetic (i.e. it is not “natural”).  There is therefore an incentive for deliberate misrepresentation on the label, and a consequential need for test verification methods as to whether the citric acid is “natural”.  Current reference specifications (e.g. AIJN) do not include tomato sauce.

In this conference presentation (open access) the authors report the successful use of Stable Isotope Ratio Analysis to discriminate the botanical source of the citric acid in tomato sauce  Biosynthesised citric acid is from cane or corn feedstock (C4 plants) whereas inherent tomato citric acid is C3.  The researchers established threshold values for citric acid carbon isotope ratios from authentic “natural” tomato sauces and used these to test a range of products on the market.

Photo by sentidos humanos on Unsplash

Isotope ratio data are increasingly used in a variety of fields including, ecology, marine sciences, earth and geosciences, forensic science, hydrology, medicine, food (including food authenticity and origin), and climate science.
 
Over the years, there have also been changes to guidelines for measurement methods, calibration conventions and even to international measurement standards that form the base of the traceability chain for isotope delta values for H, C, N, O and S.
 
It is impossible to combine isotope ratio data from a variety of sources unless the data are accompanied by a clear description of traceability and other method details.

The UK National Measurement Laboratory at LGC was part of an international group that compiled the IUPAC Technical Report presenting minimum requirements for reporting isotope ratio data, covering analytical procedure, traceability, data processing and uncertainty evaluation.

This report will help in the standardisation of methods that involve the measurement of stable isotopes.

Read the IUPAC Technical Report on minimum requirements for publishing hydrogen, carbon, nitrogen, oxygen and sulfur stable-isotope delta results.