Using strontium isotopes and a dynamic confidence interval to counter food fraud in Alpine bread

Regional niche products are increasingly sought after by consumers but also prone to food fraud. South Tyrolean cereals are mostly consumed as traditional bread which must contain a minimum of 75 % regional flour to be marketed under the "Regiokorn" seal. Four typical bread types were prepared and their Sr isotopic ratio and content together with all used ingredients was analyzed. The overall strontium pool of bread is not governed by flour alone, but by all added ingredients (flour, water, salt and yeast), making it impossible to define a clear-cut ⁸⁷Sr/⁸⁶Sr window for Regiokorn bread. Nevertheless, the analysis of all ingredients and the application of a mixing model allow for the prediction of a theoretical ⁸⁷Sr/⁸⁶Sr value. A statistical error propagation method was employed to establish 95 % confidence intervals that react dynamically to the type and ratio of ingredients. This would enable to detect fraudulent adulterations with a high likelihood.