Functioning of Saccharomyces cerevisiae in honey coffee (Coffea canephora) and their effect on metabolites, volatiles and flavor profiles.

Post-harvesting and microbial activity of coffee play a critical role in the metabolites and the sensory quality of the brew. The pulped natural/honey coffee process is an improvised semi-dry technique consisting of prolonged fermentation of depulped coffee beans excluding washing steps. The starter culture application in coffee industry plays an important role to enhance the cup quality. This work focuses on the fermentation of pulped natural/honey Robusta coffee with a starter culture (Saccharomyces cerevisiae MTCC 173) and the identification of fermentation patterns through 1H NMR, microbial ecology, volatomics and organoleptics of brew. Fermentation was accelerated by yeast populace (10 cfu log/mL) for 192 h. Principal compound analysis performed on 1H NMR led to the investigation of metabolites such as sugars, alkaloids, alcohols, organic acids and amino acids. Detection of some sugars and organic acids represented that the starter cultures imparted few metabolic changes during the process. A major activity of sugars in fermentation with 83.3 % variance in PC 1 and 16.7 % in PC 2 was observed. The chemical characteristics such as carbohydrates (41.88 ± 0.77 mg/g), polyphenols (34.16 ± 0.79 mg/g), proteins (58.54 ± 0.66 mg/g), caffeine (26.54 ± 0.06 mg/g), and CGA (21.83 ± 0.04 mg/g) were also evaluated. The heatmap-based visualization of GC-MS accorded characterization of additional 5 compounds in treated (T) coffee contributing to sweet, fruity and caramelly odor notes compared to untreated (UT). The sensory outlines 72.5 in T and 70.5 in UT scores. Preparation of honey coffee with Saccharomyces cerevisiae is the first report, which modulated the flavor and quality of coffee.

Pulped natural/honey robusta coffee fermentation metabolites, physico-chemical and sensory profiles.

The pulped natural/honey coffee (HC) of Coffea canephora (Robusta) is an innovative modified semi-dry technique. Studies have focused on HC and washed coffee (WC) fermentation, microbial metabolites, quality of green and roasted, using 1H NMR, GC-MS, and sensory investigation. Pipecolate and 3-hydroxy-3-methyglutarate have been identified for the first time. Principal Component Analysis (PCA) variability of the roasted beans, with PC 1 depicting 87.4 % and 12.6 % PC 2 respectively highlights the impact of major sugars and secondary metabolites acquired through HC. The HC fermentation (192 h) influenced carbohydrates, organic acids, and secondary metabolites besides flavor precursors compared to WC (72 h). Although HC and WC beans share similar physical qualities, enhanced volatile compounds, enriched concentration, organoleptics with pleasant, sweet, tea rose and chocolaty flavors attributes were embodied in HC than WC. The pulped natural post-harvest technique in robusta is a value addition with quality that can fetch a better premium.

Existence of ß-diketone form of curcuminoids revealed by NMR spectroscopy.

Curcumin (CUR), demethoxycurcumin (DMC) and bisdemethoxycurcumin (BDMC) - the class of natural compound derived from turmeric can exist as keto-enol and ß-diketone tautomer form. The structure and dynamics of particular relevance CUR is reported in prior studies, whereas DMC and BDMC, by far, have not been scrutinized. In the present studies, we have investigated the detailed molecular structure of CUR, DMC and BDMC by employing NMR spectroscopy as a key tool. The bridging carbon as methylene in ß-diketone form and methine in keto-enol form shows significant difference in NMR spectrum. The results justified that Curcuminoids (CC) has nearly 3% of ß-diketone tautomer in DMSO solvent at 298 K. Further, results revealed that ß-diketone form was favoured in alkaline pH condition whereas acidic and neutral pH conditions favour keto-enol tautomer. However, at higher temperature equilibrium shift towards ß-diketone tautomer. Moreover, this is the first report by NMR for observing the presence of ß-diketone tautomer.

Facile NMR approach for profiling curcuminoids present in turmeric.

Curcumin, together with demethoxycurcumin and bisdemethoxycurcumin as a whole called curcuminoids, is an active phytochemical constituent present in the turmeric. When it comes to their analysis, most will rely on UV-Visible spectroscopy, HPLC and LC-MS methods. Looking to improve productivity, time and simplicity, we are proposing a 1H NMR based approach for curcuminoids analysis and its applications to different geographical regions. In the present work, sample preparation protocol is reported for the simultaneous determination of curcuminoids using 1H NMR. For the quantification of curcuminoids, 6-7 ppm vinylic proton region in the 1H NMR spectrum was used, where acetone was observed as the suitable solvent in terms of curcuminoids solubility and proper resolution of peak. The result shows that curcumin (46.8-59.50%) was major among all varieties, followed by DMC (22.15-27.70%) and BDMC (17.52-30.29%) except in Andhrapradesh variety, where BDMC (30.29%) was more than DMC (22.89%). These studies were further supported by HPLC analysis.