Based on coffee’s unique and fascinating flavor, coffee has become the most popular nonalcoholic drink in the world and is a significant agricultural economic crop in tropical- and subtropical-planted coffee countries and regions. It is also beneficial for human health because of its rich active compounds, such as caffeine, chlorogenic acids, trigonelline, tryptophan alkaloids, diterpenes, melanoidins, etc. These compounds often relate to the prevention of cardiovascular disease, Alzheimer’s disease, and antibacterial, anti-diabetic, neuroprotection, and anti-cancer activities. The formation of coffee’s flavor results from various influence factors, including genetics, shade, elevation, post-harvest processing, fermentation, roasted methods, etc. The first stage of coffee production is obtaining green coffee beans through the primary process. Fermentation is critical in the primary process of coffee, which is often related to yeasts, bacteria, and filamentous fungi. Therefore, microorganisms play a key role in coffee fermentation and coffee flavor. To provide an understanding of the role of microorganisms in coffee fermentation, the coffee fermentation overview and microbial characteristics in different coffee primary processing methods and different coffee fermentation regions were reviewed in this paper. Brazil and China are the main study countries in coffee fermentation, which contribute a large number of technologies and methods to improve coffee flavor by fermentation. Different primary processing methods (wet, dry, or semi-dry processing) and coffee producer countries had obvious microbial community characteristics. Moreover, the application of yeast and bacteria for improving coffee flavor by microbial fermentation was also introduced.

Sichuan black tea (SCBT) is well known for its pleasant sweet and citrus-like aroma. However, the origin of this distinctive aroma remains unknown. Herein, the aroma characteristics of SCBT during processing were comprehensively investigated by sensory evaluation, gas chromatography–mass spectrometry, and odor activity value (OAV). A total of 764 volatile compounds were identified and grouped into 16 categories. Notably, terpenoids, heterocyclic compounds, and esters comprised 19.35%, 16.34%, and 16.08% of total volatile compounds produced during processing, respectively. Moreover, the fermentation and second drying stages exhibited the most striking variations, with 99 and 123 volatile compounds being significantly altered. In addition, the OAV analysis led to the identification of 17 volatile compounds as key differential volatile compounds (DVCs): these included citronellol, linalool, p-cymene, (E)-linalool oxide (furanoid), etc. Among them, (3Z)-3,7-dimethylocta-1,3,6-triene and D-limonene that exhibited a grassy aroma decreased during processing, while linalool and p-cymene that had a sweet and citrus aroma increased. Thus, based on a correlation between characteristic aroma data and descriptive sensory analysis data, linalool and p-cymene were identified as the primary volatiles responsible for the sweet and citrus-like aroma. In conclusion, this study improves our understanding of the components and formation mechanism of the sweet and citrus-like aroma of SCBT.

This study aimed to compare chemical compositions, antioxidant activities, and acetylcholinesterase inhibitory activities of coffee flowers (ACF) and coffee leaves (ACL) with green coffee beans (ACGB) of Coffea Arabica L. The chemical compositions were determined by employing high‐performance liquid chromatography–mass spectroscopy (HPLC–MS) and gas chromatography–mass spectroscopy (GC–MS) techniques. Antioxidant effects of the components were evaluated using DPPH and ABTS radical scavenging assays, and the ferric reducing antioxidant power (FRAP) assay. Their acetylcholinesterase inhibitory activities were also evaluated. The coffee sample extracts contained a total of 214 components identified by HPLC‐MS and belonged to 12 classes (such as nucleotides and amino acids and their derivatives, tannins, flavonoids, alkaloids, benzene, phenylpropanoids, and lipids.), where phenylpropanoids were the dominant component (>30%). The contents of flavonoids, alkaloids, saccharides, and carboxylic acid and its derivatives in ACF and ACL varied significantly (p < .05) compared to similar components in ACGB. Meanwhile, 30 differentially changed chemical compositions (variable importance in projection [VIP] > 1, p < .01 and fold change [FC] > 4, or <0.25), that determine the difference in characteristics, were confirmed in the three coffee samples. Furthermore, among 25 volatile chemical components identified by GC–MS, caffeine, n‐hexadecanoic acid, 2,2′‐methylenebis[6‐(1,1‐dimethylethyl)‐4‐methyl‐phenol], and quinic acid were common in these samples with caffeine being the highest in percentage. In addition, ACL showed the significantly highest (p < .05) DPPH radical scavenging capacity with IC₅₀ value of 0.491 ± 0.148 mg/ml, and acetylcholinesterase inhibitory activity with inhibition ratio 25.18 ± 2.96%, whereas ACF showed the significantly highest (p < .05) ABTS radical scavenging activity with 36.413 ± 1.523 mmol trolox/g Ex. The results suggested that ACL and ACF had potential values as novel foods in the future.