Niacin, alkaloids and (poly)phenolic compounds in the most widespread Italian capsule-brewed coffees

Abstract

Coffee is one of the most popular beverages worldwide and, nowadays, one of the most practical way for its preparation is by prepacked capsules. The aim of this study was comparing the content in caffeine, trigonelline, N-methylpyridinium (NMP), niacin, and chlorogenic acids of 65 different capsule-brewed coffees, commercialised by 5 of the most representative brands in Italy. Coffees were prepared from capsules following manufacturer's instructions and analysed with an optimized UHPLC-MS/MS method able to assess all these phytochemicals in one single run. Inter-lot and capsule variability were also studied for a subset of coffee capsules. Except for decaffeinated coffees, caffeine amount accounted between 54 and 208 mg/serving. Regular espresso coffees showed higher trigonelline, NMP, and niacin concentrations than large (lungo) and decaffeinated samples, with average serving amounts of 17.96, 1.78, and 0.66 mg, respectively. Regarding chlorogenic acids, caffeoylquinic acids were the most relevant ones (20-117 mg/serving). Feruloylquinic acids were quantified between 8 and 50 mg/serving. Coumaroylquinic acids, hydroxycinnamate dimers, caffeoylshikimic acids, and caffeoylquinic lactones were also present at lower concentrations. Multivariate analysis provided comprehensive information on the phytochemical profile of the different types of coffee, showing a great variability among coffees with some brand-related insights. This study supports the need for accurately characterizing espresso coffees while investigating the beneficial effects of coffee on human health.

Figure 1

UHPLC-MS/MS profile of capsule-brewed coffees with detection of the considered compounds by SRM. Legend: m/z 95 for N-methylpyridinium (1); m/z 138 for trigonelline (2); m/z 124 for niacin (3); m/z 195 for caffeine (4); m/z 353 for caffeoylquinic acids (5–7); m/z 367 for feruloylquinic acids (8–10); m/z 337 for coumaroylquinic acids (11–12); m/z 335 for caffeoylshikimic acids and caffeoylquinic lactones (13–16); m/z 349 for feruloylquinic lactones (17). See Table 1 for further details.

Figure 2

Capsule variability of caffeine (A), trigonelline (B), N-methylpyridinium (C) and total caffeoylquinic acids (D) of capsule espresso coffee samples. Capsules were representative of regular, lungo, and decaffeinated coffees belonging to the five considered brands. CQAs, caffeolylquinic acids; EC, espresso coffee; NMP, N-methylpyridinium.

Figure 3

Loading plot (A) and score plot (B) obtained from the PCA with varimax of the considered bioactive compounds and capsule espresso coffees. Legend: n-CQA: n-O-caffeoylquinic acid; CSAn: caffeoylshikimic acid isomer; CQLn: caffeoylquinic lactone isomer; n-CouQA: n-O-coumaroylquinic acid; n-FQA: n-O-feruloylquinic acid; n-FQL: n-O-feruloylquinic lactone; NMP: N-methylpyridinium.