Carbohydrate specification limits for the authenticity assessment of soluble (instant) coffee: statistical approach

Carbohydrates are very good tracers for the authenticity assessment of soluble (instant) coffee. Total glucose and total xylose were determined in 1002 samples of commercial soluble coffees using high-performance anion-exchange chromatography with pulsed amperometric detection (HPAEC-PAD) according to AOAC Method 995.13 and ISO standard 11292. The samples analyzed included both authentic and adulterated coffees but were all sold as 100% pure soluble coffee. The statistical model, called "mixture of distributions," was applied to all results and allowed to derive the maximum content of the 2 carbohydrates in the population of products corresponding to pure soluble coffee: 2.32% for total glucose and 0.42% for total xylose. The specification limits, above which a soluble coffee should be considered as adulterated, were calculated by adding the corresponding expanded measurement uncertainty to the maximum content. Specification limits of 2.46% for total glucose and 0.45% for total xylose were obtained. The data statistically confirm previously established criteria for the authenticity assessment of commercial soluble coffee.