Caffeine content in Nepalese coffee: Influence of brewing methods and storage time

Abstract

Coffee’s global appeal, attributed to its caffeine content impacting flavor and health, lacks thorough exploration of Nepalese coffee despite its growing coffee sector. The lack of comprehensive studies inhibits informed choices on caffeine consumption and coffee selection. Here, we aimed to bridge this gap by assessing caffeine content and pH levels in Nepalese coffee beans using common extraction methods - boiling, French Press, and Moka pot. We compared ten locally sourced coffee brands from Pokhara, Nepal, conducting the experiment upon unsealing the coffee packets, designated as day 0, and repeated it after 21 days with the same samples, labeled as day 21. An Ultra Performance Liquid Chromatography (UPLC) with a UV/Visible detector was used to estimate caffeine concentration. The Moka pot maintained the highest average caffeine concentration at 14.39±1.87 mg/g (day 0) and 13.83±1.24
mg/g (day 21), followed by boiling at 11.63±1.17 mg/g (day 0) and 10.16±1.63 mg/g (day 21), with the French press yielding the lowest concentration at 10.11±0.96 mg/g (day 0) and 8.90±2.09 mg/g (day 21). pH values varied, with the boiling method resulting in the highest pH (5.51±0.22). Coffee pH increased from 5.41±0.20 to 5.45±0.21 over 21 days. Our findings underscore the importance of considering extraction methods when evaluating coffee’s caffeine content and pH levels. This study provides valuable insights for consumers to make informed choices about caffeine intake and coffee preferences. Further research could explore additional factors influencing caffeine content and pH levels, such as regional differences, cultivation practices, titratable acidity, sensory evaluations, and chemical profiling.

Key words: UPLC analysis; pH; moka pot; french press; boiling.