In this study, the microbial community in Catimor coffee cherries produced in Yunan during anaerobic pretreatment was investigated by 16S rDNA and internal transcribed spacer (ITS) amplicon sequencing and the characteristic flavor substances of roasted coffee beans were analyzed by gas chromatography-mass spectrometry (GC-MS). Furthermore, this study examined the correlation between microbial communities and flavor substances. Results revealed that anaerobic pretreatment significantly promoted the proliferation of bacterial genera including Leuconostoc, Pediococcus and Lactobacillus as well as fungal genera such as Wickerhamomyces, Candida, Saccharomyces, Pichia and Aspergillus. The anaerobic pretreatment group exhibited substantial increases in lactic acid, acetic acid, malic acid, and succinic acid contents, with Leuconostoc, Pediococcus, Lactobacillus and Wickerhamomyces identified as possibly key contributors to lactic acid production. Through orthogonal partial least square-discriminant analysis (OPLS-DA), isoamyl acetate, ethyl hexanoate, and acetic acid were identified as characteristic volatile components based on variable importance in projection (VIP > 1) and odor activity value (OAV > 1). Principal component analysis (PCA) further demonstrated that the dominant microbial communities under anaerobic pretreatment played a crucial role in generating key flavor substances such as lactic acid, acetic acid, ethyl hexanoate and isoamyl acetate.

In this study, light, medium, and dark roasted Catimor coffee beans from Yunnan, China and Sumatra Indonesia were selected to compare the differences in the extract concentration, extraction efficiency, titratable acid, total phenols, total sugar, caffeine, trigonelline, chlorogenic acid, antioxidant activity and volatile components of cold and hot brew coffee. Principal component analysis (PCA) was carried out to explore the effect of roasting degree on the physicochemical indexes and flavor components of cold brew coffee. The results showed that with the increase of roasting degree, the extract concentration and extraction efficiency of cold brew coffee increased significantly, and the levels of titratable acid, total phenols, total sugar, trigonelline, chlorogenic acid, and antioxidant activity decreased significantly (P < 0.05). Cold brew coffee had higher extract concentration, extraction efficiency and total sugar levels than hot brew coffee, while the levels of titratable acid, total phenolic content, and antioxidant activity were significantly lower than those of hot brew coffee (P < 0.05). The headspace solid phase microextraction combined with gas chromatography (HS-SPME-GC-MS) analysis showed that the content of volatile components in light roasted coffee was significantly lower than that in medium roasted coffee, and dark roasted coffee had the highest number and amount of volatile components. Furthermore, PCA could distinguish between cold and hot brew coffee, and the contribution rate of volatile components was quite different between them. 2-Butanone, 2-butenal and other substances responsible for floral aroma had a higher contribution rate to cold brew light roasted coffee, while compounds contributing to roasted nut-like aroma including 2-methylpyrazine and furfuryl alcohol had a higher contribution rate to hot brew light roasted coffee. 2,6-Diethylpyrazine, ligustrazine and other compounds contributing to roasted nut-like aroma had a higher contribution rate to both cold and hot brew middle roasted coffee. 2-Vinylfuran, methylfurfuryl mercaptan, 2,5-diethylpyrazine, and furfuryl methyl sulfide had a higher contribution rate to cold brew dark roasted coffee, and cresol and 1-methylpyrrole had a higher contribution rate to hot brew dark roasted coffee. Compared with hot brew coffee, roasting degree had a greater impact on the antioxidant capacity and volatile components of cold brew coffee.

This study aimed to explore the intervention effects of coffee extracts with different roasting levels on lipid metabolism disorders and gut microbiota in high-fat diet mice. Specifically, 45 C57BL/6J male mice were randomly divided into five groups, which were fed a control diet (CON), a high-fat diet (HFD) alone and supplemented with lightly roasted (LC), moderately roasted (MC) and highly roasted (HC) coffee extracts, respectively for 9 weeks. After completion of the experimental period, changes in body mass and blood lipids were determined and the composition of the gut microbiota was identified using 16S rRNA gene sequencing. The results demonstrated that highly roasted coffee showed significantly better ameliorative effects on obesity, dyslipidemia and inflammatory reactions compared with moderately and lowly roasted coffee (P < 0.05). The gut microbiota diversity analysis showed that highly roasted coffee significantly increased the ratio of relative abundance between Firmicutes and Bacteroidetes in HFD-fed mice and promoted the enrichment of probiotics such as Oscillospirales and Odoribacter. Meanwhile, it significantly increased the production of short-chain fatty acids (P < 0.05), compared with the high-fat diet-fed group. Additionally, highly roasted coffee was significantly more effective in up-regulating the mRNA expression of the colonic tight junction protein Claudin-1 than moderately and lowly roasted coffee (P < 0.05). In summary, highly roasted coffee had more significant intervention effects on obesity, and this may be attributed to the structural regulation of the gut microbiota.

This study aimed to clarify the oxidative damage in human skin fibroblasts (HSF) treated with trimethylamine oxide (TMAO) and to elucidate its pro-aging effect in skin cells in terms of antioxidant indicators, levels of inflammatory cytokines, levels of collagen and matrix metalloproteinases, and mRNA expression of related genes. The results showed that TMAO treatment significantly increased the levels of reactive oxygen species (ROS) and malondialdehyde (MDA), and decreased the content of reduced glutathione, superoxide dismutase (SOD) activity, and total antioxidant capacity (TAC) in HSF cells (P < 0.05). TMAO treatment was found to significantly elevate the mRNA levels of inflammatory cytokines, including tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and matrix metalloproteinase-1 (MMP-1), and decrease the mRNA transcript levels of collagen synthesis-related genes and the inducible nitric oxide synthase (iNOS) gene by reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and enzyme-linked immunosorbent assay (ELISA). Western blot analysis showed that the protein expression level of phosphorylated p65 (p-p65) significantly increased (P < 0.05). Vitamin C (VC) was able to protect against TMAO-induced oxidative stress in HSF cells, and reduce inflammation and collagen loss. These results indicated that TMAO can produce oxidative stress in HSF cells, which may activate the signaling pathway of nuclear factor kappa-B (NF-κB), promote NF-κB phosphorylation in HSF cells, induce inflammatory responses, reduce collagen synthesis, and accelerate collagen degradation, thus possibly promoting skin cell aging.