Rune Christina J Birke, Giacalone Davide, Steen Ida, Duelund Lars, Münchow Morten, Clausen Mathias Porsmose
Department of Technology and Innovation, University of Southern Denmark, Campusvej 55, 5230, Odense M, Denmark.
CoffeeMind, Hansstedvej 35, 2500, Valby, Denmark.
Curr Res Food Sci. 2023 Mar 22;6:100485. doi: 10.1016/j.crfs.2023.100485. eCollection 2023.
Coffee brewed on light, and very light-roast coffee beans have emerged as a recent trend among specialty coffee drinkers. The acidity of such light-roast coffee, and coffee in general, is an important sensory characteristic, as there is demonstrated a clear correlation between the roast level and perceived acidity in brewed coffee. The acidity is believed to be strongly linked to the content and composition of organic acids in coffee. Still, there is limited literature on acid content in brewed coffee and on the relevance of specific acid concentrations to sensory perception. In this study, we determined concentrations of acids and sugars in French-press brewed specialty coffee. We used varying roast degrees in the light to very light range using five coffees from different geographical locations (Brazil, Bolivia, and Kenya) and determined the sensory detection threshold and recognition for selected acids. The concentration of all individual acids except one (formic) either significantly decreased (citric, malic, and chlorogenic acid) or increased (acetic, lactic, phosphoric, quinic, and glycolic acid) systematically with an increasing roast degree, while no systematic trends were found between the different coffee samples. The sugar content decreased with an increasing roast degree. The sensory detection threshold for malic, acetic, and lactic acid was determined to be above the actual concentration of said acids in the coffee and just below for phosphoric acid, indicating that these compounds are unlikely to individually be perceived in coffee. Only citric acid can be clearly detected in the threshold test (not identified by experts in coffee) in concentrations above the measured concentrations, as the detection threshold was below (<0.16 g/L) the concentration found in the investigated coffees (0.23-0.60 g/L). The measured citric acid concentration was found to be much higher for the Brazil coffees (0.49 ± 0.08 g/L) compared to the Bolivia coffee (0.40 ± 0.11 g/L), and the Kenya coffees (0.30 ± 0.07 g/L). Furthermore, none of the acids added to the coffee were correctly recognized by coffee experts when spiked with measured average concentrations. Combined, the results question the direct relation between individual organic acids and acidity in coffee and point towards a more complex understanding of perceived acidity.
用轻度烘焙及极轻度烘焙咖啡豆煮制的咖啡，近来在特色咖啡饮用者中成为一种潮流。这种轻度烘焙咖啡以及一般咖啡的酸度，是一项重要的感官特性，因为已证明烘焙程度与煮制咖啡中感知到的酸度之间存在明显关联。酸度被认为与咖啡中有机酸的含量和组成密切相关。然而，关于煮制咖啡中酸含量以及特定酸浓度与感官感知相关性的文献有限。在本研究中，我们测定了法式滤压壶煮制的特色咖啡中的酸和糖浓度。我们使用了来自不同地理位置（巴西、玻利维亚和肯尼亚）的五种咖啡，在轻度到极轻度范围内采用不同的烘焙程度，并确定了选定酸的感官检测阈值和识别情况。除一种酸（甲酸）外，所有单一酸的浓度随着烘焙程度的增加要么显著降低（柠檬酸、苹果酸和绿原酸）要么系统性增加（乙酸、乳酸、磷酸、奎宁酸和乙醇酸），而不同咖啡样品之间未发现系统性趋势。糖含量随着烘焙程度的增加而降低。苹果酸、乙酸和乳酸的感官检测阈值被确定高于咖啡中这些酸的实际浓度，而磷酸的感官检测阈值略低于其实际浓度，这表明这些化合物不太可能在咖啡中被单独感知到。在阈值测试中，只有柠檬酸能在高于测量浓度的情况下被清晰检测到（咖啡专家未识别出），因为检测阈值低于（<0.16 g/L）所研究咖啡中发现的浓度（0.23 - 0.60 g/L）。与玻利维亚咖啡（0.40 ± 0.11 g/L）和肯尼亚咖啡（0.30 ± 0.07 g/L）相比，巴西咖啡中测得的柠檬酸浓度要高得多（0.49 ± 0.08 g/L）。此外，当添加到咖啡中的酸达到测量平均浓度时，咖啡专家无法正确识别其中任何一种酸。综合来看，这些结果对咖啡中单一有机酸与酸度之间的直接关系提出了质疑，并指向对感知酸度的更复杂理解。
