Characterization of the impact of chlorogenic acids on tactile perception in coffee through an inverse effect on mouthcoating sensation.

Coffee "body" is acknowledged by coffee industry professionals to be an attribute which contributes meaningfully to overall coffee quality and is defined as the collective tactile sensation imparted by the beverage. Currently, there is limited knowledge of the chemical compounds that contribute to tactile attributes in coffee. In the present work, coffee body was determined to be comprised of 4 sub-attributes including mouthcoating, astringency, chalkiness, and thickness and the specific constituents contributing to the tactile sensation of mouthcoating were further pursued using sensory-guided fractionation via preparative-scale liquid chromatography. Signal detection-based sensory methodologies were employed to characterize the sensory effects elicited by selected compounds in water and coffee matrices. Two chlorogenic acids, 3-O-caffeoylquinic acid (3-CQA) and 4-O-caffeoylquinic acid (4-CQA), were observed to impart subtle but significantly perceptible mouthcoating effects in water and/or coffee. Counterintuitively, sensory perception was inversely related to compound concentration. Complex receptor-ligand interactions or salivary lubrication dynamics are discussed as two potential mechanisms to explain this inverse relationship. Taken together, the outcomes of the present study (1) provide new targets for coffee tactile sensation optimization and modulation, (2) identify a novel dimension of sensory impact for two compounds of the chlorogenic acid family, and (3) present a need for deeper investigation into 3-CQA and 4-CQA mechanisms of sensation.

Identification of compounds that enhance bitterness of coffee brew.

The bitterness perception of coffee is a key attribute that impacts consumer acceptance. Nontargeted liquid chromatography/mass spectrometry (LC/MS) flavoromics analysis was applied to identify compounds that enhance the bitter perception of roasted coffee brew. Orthogonal partial least squares (OPLS) analysis was used to model the comprehensive chemical profiles and sensory bitter intensity ratings of fourteen coffee brews with good fit and predictivity. Five compounds that were highly predictive and positively correlated to bitter intensity were selected from the OPLS model, further isolated, and purified using preparative LC fractionation. Sensory recombination testing demonstrated that five compounds significantly enhanced the bitter perception of coffee when presented as a mixture, but not when presented individually. In addition, a set of roasting experiments revealed the five compounds were generated during the coffee roasting process.

Identification of subthreshold chlorogenic acid lactones that contribute to flavor instability of ready-to-drink coffee.

Flavor instability of ready-to-drink (RTD) coffee during storage negatively impacts product quality. Untargeted liquid chromatography/mass spectrometry (LC/MS) analysis was applied to identify chemical compounds that degraded during storage and impacted the flavor attributes of RTD coffee. LC/MS chemical profiles of non-aged and aged coffee samples were modeled against the degree of difference sensory scores by orthogonal partial least squares with good fit (R2Y = 0.966) and predictive ability (Q2 = 0.960). The top five predictive chemical features were subsequently purified by off-line multidimensional Prep-LC, revealing ten coeluting chlorogenic acid lactones (CGLs) compounds that were identified by LC/MS and nuclear magnetic resonance (NMR). The concentrations of eight CGLs significantly decreased in the coffee during the 4-month storage. Sensory recombination testing revealed the degradation of 3-O-caffeoyl-É£-quinide and 4-O-caffeoyl-É£-quinide significantly impacted the flavor stability of RTD coffee at subthreshold concentrations.

Identification of Non-Volatile Compounds Generated during Storage That Impact Flavor Stability of Ready-to-Drink Coffee.

Coffee brew flavor is known to degrade during storage. Untargeted and targeted LC/MS flavoromics analysis was applied to identify chemical compounds generated during storage that impacted the flavor stability of ready-to-drink (RTD) coffee. MS chemical profiles for sixteen RTD coffee samples stored for 0, 1, 2, and 4 months at 30 °C were modeled against the sensory degree of difference (DOD) scores by orthogonal partial least squares (OPLS) with good fit and predictive ability. Five highly predictive untargeted chemical features positively correlated to DOD were subsequently identified as 3-caffeoylquinic acid, 4-caffeoylquinic acid, 5-caffeoylquinic acid, 3-O-feruloylquinic acid, and 5-O-feruloylquinic acid. The increase in the six acidic compounds during storage was confirmed by sensory recombination tests to significantly impact the flavor stability of RTD coffee during storage. A decrease in pH, rather than an increase in total acidity, was supported to impact the coffee flavor profile.

Identification of coffee compounds that suppress bitterness of brew.

Untargeted LC-MS flavoromic profiling was utilized to identify compounds that suppress bitterness perception of coffee brew. The chemical profiles of fourteen brew samples and corresponding perceived bitterness intensities determined by descriptive sensory analysis were modeled by orthogonal partial least squares (OPLS) with good fit (R2Y > 0.9) and predictive ability (Q2 > 0.9). Ten chemical markers that were highly predictive and negatively correlated to bitter intensity were subsequently purified by multi-dimensional preparative LC-MS to conduct sensory recombination testing and/or confirm compound identifications by NMR. Three of the ten compounds evaluated, namely 4-caffeoylquinic acid, 5-caffeoylquinic acid, and 2-O-ß-d-glucopyranosyl-atractyligenin were identified as bitter modulators in coffee, and significantly decreased the perceived bitterness intensity of the brew.

Identification of Somatosensory Compounds Contributing to Slipperiness and Thickness Perceptions in Canned Prunes (Prunus domestica).

The role of small molecules on the somatosensory properties of prunes (Prunus domestica) was investigated. Sensory descriptive analysis defined two main somatosensations, "thickness" and "slippery". On the basis of these two attributes, sensory-guided multidimensional fractionation techniques allowed for the isolation of four main compounds, which were identified by mass spectrometry and comparison to authentic standards. Three compounds were identified as monosubstituted isomers of chlorogenic acid, namely, 1-O-caffeoylquinic acid (1-CQA), 3-O-caffeoylquinic acid (3-CQA), and 4-O-caffeoylquinic acid (4-CQA), in addition to a fourth, vanillic acid glucoside (VG). Sensory recombination model analysis of each compound at endogenous concentrations of the prunes indicated that all compounds significantly contributed to slippery sensations, whereas 3-CQA, 4-CQA, and VG contributed to thickness sensations (α = 0.05).

Identification of Compounds that Negatively Impact Coffee Flavor Quality Using Untargeted Liquid Chromatography/Mass Spectrometry Analysis.

Untargeted liquid chromatography/mass spectrometry (LC/MS) flavoromics analysis was carried out on 18 coffee brews ranging in Specialty Coffee Association (SCA) cup scores. Six compounds highly predictive of low cup score were isolated from coffee using multidimensional preparative LC/MS and further evaluated by sensory recombination analysis with certified SCA quality graders. A significant decrease in cup score was demonstrated with four of the six compounds when added to a specialty coffee brew. High-resolution mass spectrometry and mono- and bidimensional nuclear magnetic resonance experiments were used to successfully elucidate four of the structures as 16α,17-dihydroxy-ent-kauran-19-oic acid (compound 1), its diglycosidic compound 16α,17-dihydroxy-ent-kauran-19-diglycoside (compound 2), 16α,17,18-trihydroxy-ent-kauran-19-oic acid (compound 5), and 16α-hydroxy-17-ent-kauren-19-oic acid (compound 6). All four ent-kaurane diterpene compounds were endogenous to green coffee beans, providing direct chemical indicators of low-quality coffee.

Impact of bitter tastant sub-qualities on retronasal coffee aroma perception.

The impact of different bitter taste compounds on the retronasal perception of coffee aroma was investigated. A sorted napping experiment was carried out on thirteen compounds at iso-intense bitter concentrations. Differences in perceptual bitter sub-qualities among the compounds were reported by Multidimensional Scaling (MDS) and Multiple Factor Analysis (MFA) analyses. Seven exemplar compounds were further selected to investigate the impact of taste sub-qualities on cross-modal flavor interactions. In general, the different bitter compounds, when paired with a coffee aroma isolate, significantly modified the perception of the retronasal coffee aroma profile. Interestingly, the three bitter compounds endogenous to coffee had the most similar impact on the coffee aroma profile. Further sensory analysis of these sample sets indicated no significant effect of the bitter compounds on the orthonasal perception. Gas Chromatography/Mass Spectrometry (GC/MS) analysis of the volatile composition of the samples headspace also indicated negligible impact of the bitter compounds on aroma release. Altogether evidence of cross-modal interactions occurring at a higher cognitive level were demonstrated in a complex food sample, supporting the importance of multi-modal sensory integration on flavor perception.

Identification of flavor modulating compounds that positively impact coffee quality.

Untargeted LC/MS flavoromic profiling was utilized to identify compounds that positively impact coffee quality. The chemical profiles of eighteen coffee samples and the corresponding Specialty Coffee Association (SCA) cup scores were modeled by orthogonal partial least squares (OPLS) analysis with good fit and predictive ability (R2Y > 0.9, Q2 > 0.9). Four highly predictive chemical compounds positively correlated to cup score were subsequently isolated and purified (>90%) by multi-dimensional preparative LC/MS fractionation. Sensory recombination analysis by certified SCA Q-graders (n = 5) confirmed three out of four compounds significantly increased cup score when added to a control coffee (p < 0.001). Based on accurate mass spectrometry and NMR experiments, the compound structures were identified as novel compounds 3-O-caffeoyl-4-O-3-methylbutanoylquinic acid, and the corresponding lactone 3-O-caffeoyl-4-O-3-methylbutanoyl-1,5-quinide, as well as an unknown phenolic derivative containing a 3-methylbutanoyl moiety ([M-H]-1, m/z 671). No direct flavor activity was observed for each compound, indicating these compounds act as flavor-modifiers.

Storage conditions modulate the metabolomic profile of a black raspberry nectar with minimal impact on bioactivity.

Pre-clinical and clinical studies suggest black raspberries (BRBs) may inhibit the development of oral cancer. Lyophilized BRB powder is commonly used in these studies, but processed BRB products are more often consumed. The objective of this work was to understand how storage conditions influence the phytochemical profile and anti-proliferative activity of a BRB nectar beverage. Untargeted UHPLC-Q-TOF-MS based metabolomics analyses demonstrated that large chemical variation was introduced by storage above -20 °C over 60 days. However, minimal change in anti-proliferative activity was observed when stored nectar extracts were applied to SCC-83-01-82 premalignant oral epithelial cells. As proof of concept, cyanidin-3-O-rutinoside and its degradation product, protocatechuic acid, were administered in different ratios maintaining an equimolar dose, and anti-proliferative activity was maintained. This study shows the utility of metabolomics to profile global chemical changes in foods, while demonstrating that isolated phytochemicals do not explain the complete bioactivity of a complex food product.

Identification of a novel umami compound in potatoes and potato chips.

The influence of frying time on the taste profile of potato chips was characterized. Direct comparison of isolates from potato chip samples fried for 170s and 210s indicated longer frying time increased the perceived umami intensity and decreased the sour intensity. The compounds responsible for the greater umami intensity were identified as monosodium l-pyroglutamate (l-MSpG) and monosodium d-pyroglutamate (d-MSpG). The reduction in sour intensity was attributed to the degradation of d-chlorogenic acid. MSpGs were endogenous in raw potatoes and also thermally generated from glutamic acid during frying. Taste recombination studies further confirmed the contribution of both compounds to the umami character of potato chips. Furthermore, time-intensity taste analysis revealed that topical addition of both l- and d-MSpG enhanced the perceived intensity of the umami taste and the overall flavor characteristic of the potato chips.

Identification of Aging-Associated Food Quality Changes in Citrus Products Using Untargeted Chemical Profiling.

Chemometric techniques have seen wide application in biological and medical sciences, but they are still developing in the food sciences. This study illustrated the use of untargeted LC/MS chemometric methods to identify features (retention time_m/z) associated with food quality changes as products age (freshness). Extracts of three citrus fruit varietals aged over four time points that corresponded to noted changes in sensory attributes were chemically profiled and modeled by two discriminatory multivariate statistical techniques, projection partial least-squares discrimant analysis (PLS-DA) and machine learning random forest (RF). Age-associated compounds across the citrus platform were identified. Varietal was treated as a nuisance variable to emphasize aging chemistry, and further variable selection using age-related piecewise model generation and meta filtering to emphasize features associated with general aging chemistry common to all the citrus extracts. The identified features were further replicated in a validation study to illustrate the validity and persistence of these markers for applications in citrus food platforms.

Spermidine Derivatives in Lulo (Solanum quitoense Lam.) Fruit: Sensory (Taste) versus Biofunctional (ACE-Inhibition) Properties.

The bitterness in lulo (Solanum quitoense Lam.) fruit is increased during processing (juicing or drying). To identify the bitter-active compounds, the ethanolic fruit pulp extract was subjected to RP-18 solid-phase extraction, and then sensory-guided fractionated by HPLC. Two spermidine derivatives, N(1),N(4),N(8)-tris(dihydrocaffeoyl)spermidine and N(1),N(8)-bis(dihydrocaffeoyl)spermidine, were isolated and their structures confirmed by analysis of their HPLC-ESI/MS and (1)H and (13)C NMR data. The N(1),N(4),N(8)-tris(dihydrocaffeoyl)spermidine was synthesized and used as an authentic sample to unequivocally confirm the structure of this compound and to quantitate it in both fresh and dried fruit. In silico analyses demonstrated that spermidine derivatives identified in lulo pulp exhibited a strong ACE-I (angiotensin I-converting enzyme) inhibitory activity. Subsequently, these results were confirmed by in vitro analyses and showed the potential use of lulo fruit pulp as an ingredient of functional foods related to the prevention of blood hypertension.

Effect of olive mill wastewater phenol compounds on reactive carbonyl species and Maillard reaction end-products in ultrahigh-temperature-treated milk.

Thermal processing and Maillard reaction (MR) affect the nutritional and sensorial qualities of milk. In this paper an olive mill wastewater phenolic powder (OMW) was tested as a functional ingredient for inhibiting MR development in ultrahigh-temperature (UHT)-treated milk. OMW was added to milk at 0.1 and 0.05% w/v before UHT treatment, and the concentration of MR products was monitored to verify the effect of OMW phenols in controlling the MR. Results revealed that OMW is able to trap the reactive carbonyl species such as hydroxycarbonyls and dicarbonyls, which in turn led to the increase of Maillard-derived off-flavor development. The effect of OMW on the formation of Amadori products and N-ε-(carboxymethyl)-lysine (CML) showed that oxidative cleavage, C2-C6 cyclization, and the consequent reactive carbonyl species formation were also inhibited by OMW. Data indicated that OMW is a functional ingredient able to control the MR and to improve the nutritional and sensorial attributes of milk.

Identification of bitter compounds in whole wheat bread.

Bitterness in whole wheat bread can negatively influence product acceptability and consumption. The overall goal of this project was to identify the main bitter compounds in a commercial whole wheat bread product. Sensory-guided fractionation of the crust (most bitter portion of the bread sample) utilising liquid-liquid extraction, solid-phase extraction, ultra-filtration and 2-D offline RPLC revealed multiple bitter compounds existed. The compounds with the highest bitterness intensities were selected and structurally elucidated based on accurate mass-TOF, MS/MS, 1D and 2D NMR spectroscopy. Eight bitter compounds were identified: Acortatarins A, Acortatarins C, 5-(hydroxymethyl)furfural(HMF), 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), N-(1-deoxy-d-fructos-1-yl)-l-tryptophan (ARP), Tryptophol (TRO), 2-(2-formyl-5-(hydroxymethyl-1H-pyrrole-1-yl)butanoic acid (PBA) and Tryptophan (TRP). Based on the structures of these compounds, two main mechanisms of bitterness generation in wheat bread were supported, fermentation and Maillard pathways.

The anti-inflammatory effects of selenium are mediated through 15-deoxy-Delta12,14-prostaglandin J2 in macrophages.

Selenium is an essential micronutrient that suppresses the redox-sensitive transcription factor NF-kappaB-dependent pro-inflammatory gene expression. To understand the molecular mechanisms underlying the anti-inflammatory property of selenium, we examined the activity of a key kinase of the NF-kappaB cascade, IkappaB-kinase beta (IKKbeta) subunit, as a function of cellular selenium status in murine primary bone marrow-derived macrophages and RAW264.7 macrophage-like cell line. In vitro kinase assays revealed that selenium supplementation decreased the activity of IKKbeta in lipopolysaccharide (LPS)-treated macrophages. Stimulation by LPS of selenium-supplemented macrophages resulted in a time-dependent increase in 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) formation, an endogenous inhibitor of IKKbeta activity. Further analysis revealed that inhibition of IKKbeta activity in selenium-supplemented cells correlated with the Michael addition product of 15d-PGJ2 with Cys-179 of IKKbeta, while the formation of such an adduct was significantly decreased in the selenium-deficient macrophages. In addition, anti-inflammatory activities of selenium were also mediated by the 15d-PGJ2-dependent activation of the peroxisome proliferator-activated nuclear receptor-gamma in macrophages. Experiments using specific cyclooxygenase (COX) inhibitors and genetic knockdown approaches indicated that COX-1, and not the COX-2 pathway, was responsible for the increased synthesis of 15d-PGJ2 in selenium-supplemented macrophages. Taken together, our results suggest that selenium supplementation increases the production of 15d-PGJ2 as an adaptive response to protect cells against oxidative stress-induced pro-inflammatory gene expression. More specifically, modification of protein thiols by 15d-PGJ2 represents a previously undescribed code for redox regulation of gene expression by selenium.