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Abstract
The caffeine content of 124 products, including coffee, coffee-based beverages, energy drinks, tea, colas, yoghurt and chocolate, were determined using RP-HPLC with UV detection after solid-phase extraction. Highest concentrations of caffeine were found for coffee prepared from pads (755 mg l−1) and regular filtered coffee (659 mg l−1). The total caffeine content of coffee and chocolate-based beverages was between 15 mg l−1 in chocolate milk and 448 mg l−1 in canned ice coffee. For energy drinks the caffeine content varied in a range from 266 to 340 mg l−1. Caffeine concentrations in tea and ice teas were between 13 and 183 mg l−1. Coffee-flavoured yoghurts ranged from 33 to 48 mg kg−1. The caffeine concentration in chocolate and chocolate bars was between 17 mg kg−1 in whole milk chocolate and 551 mg kg−1 in a chocolate with coffee filling. A caffeine assessment tool was developed and validated by a 3-day dietary record (r 2 = 0.817, p < 0.01) using these analytical data and caffeine saliva concentrations (r 2 = 0.427, p < 0.01).
Acknowledgements
This study was supported by the Food Industries Association of Austria (FIAA).