BitterMasS: Predicting Bitterness from Mass Spectra

Bitter compounds are common in nature and among drugs. Previously, machine learning tools were developed to predict bitterness from the chemical structure. However, known structures are estimated to represent only 5-10% of the metabolome, and the rest remain unassigned or "dark". We present BitterMasS, a Random Forest classifier that was trained on 5414 experimental mass spectra of bitter and nonbitter compounds, achieving precision = 0.83 and recall = 0.90 for an internal test set. Next, the model was tested against spectra newly extracted from the literature 106 bitter and nonbitter compounds and for additional spectra measured for 26 compounds. For these external test cases, BitterMasS exhibited 67% precision and 93% recall for the first and 58% accuracy and 99% recall for the second. The spectrum-bitterness prediction strategy was more effective than the spectrum-structure-bitterness prediction strategy and covered more compounds. These encouraging results suggest that BitterMasS can be used to predict bitter compounds in the metabolome without the need for structural assignment of individual molecules. This may enable identification of bitter compounds from metabolomics analyses, for comparing potential bitterness levels obtained by different treatments of samples and for monitoring bitterness changes overtime.

Identification of Compounds That Impact Consumer Flavor Liking of American-European Hazelnut Hybrids Using Nontargeted LC/MS Analysis

American-European (Corylus americana × Corylus avellana) hazelnut hybrids are being developed for the Midwest-growing region of the United States. However, an inadequate understanding of the compounds that impact the consumer acceptance of hazelnuts limits breeding programs. Nontargeted liquid chromatography/mass spectrometry (LC/MS) chemical profiles of 12 roasted hybrid hazelnut samples and the corresponding consumer flavor liking scores were modeled by orthogonal partial least squares with good fit and predictive ability (R2Y > 0.9, Q2 > 0.9) to identify compounds that impact nut liking. The five most predictive compounds (1-5) were negatively correlated to flavor liking, selected as putative markers, purified by multidimensional preparative LC/MS, structurally elucidated (nuclear magnetic resonance, MS), quantified, and validated for sensory relevance. Compound 1 was identified as 1″-O-3'-b-glucofuranosyl-1'-O-1-b-glucofuranosyl-(2,6-dihydroxyphenyl)-ethan-4-one. Compounds 2 and 4 were identified as rotamers of 2-(3-hydroxy-2-oxoindolin-3-yl) acetic acid 3-O-6'-galactopyranosyl-2″-(2″oxoindolin-3″yl) acetate, whereas compounds 3 and 5 were identified as rotamers of 1″-O-1'-b-glucofuranosyl-9-O-6'-b-glucopyranosyl-2″-(2″-oxoindolin-3″yl) acetate. Sensory evaluation determined that all compounds were characterized by bitterness and/or astringency. The sensory threshold values of compounds 1-5 were determined to be below the concentrations reported in 91, 83, 41, 25, and 41% of all 12 hybrid hazelnut samples, respectively, indicating they contributed to aversive flavor attributes.

Identification of compounds contributing to umami taste of pea protein isolate

The umami taste of pea protein ingredients can be desirable or undesirable based on the food application. The compounds contributing to the umami perception of pea protein isolate (PPI) were investigated. Sensory-guided prep-liquid chromatography fractionation of a 10% aqueous PPI solution revealed one well-known compound, monosodium glutamate (MSG), however, it was reported at a subthreshold concentration. Two umami enhancing compounds 5'-adenosine monophosphate (AMP) and 5'-uridine monophosphate (UMP) were subsequently identified after the LC fractions were re-evaluated with MSG. Sensory recombination studies, utilizing the aqueous PPI solution as the base, confirmed AMP and UMP were umami enhancers of MSG and contributed approximately 81% of the perceived umami intensity. However UMP was only reported to enhance umami perception in combination with AMP (not individually) indicating synergistic interactions were observed between the two enhancer compounds. Therefore the presence of all three compounds are important for umami perception and provide an improved basis to tailor the flavor profile in PPI products.

Impact of rebaudioside A degradation compounds on flavor perception

Rebaudioside A, a sweet-tasting steviol glycoside, is known to degrade in food products during storage and thought to contribute to flavor instability. The impact of rebaudioside A degradation compounds on flavor perception was investigated. Sensory descriptive analysis indicated rebaudioside A degradation compounds, at concentrations below detection thresholds, modified the perception of taste, somatosensorial, and retronasal aroma attributes of a strawberry-flavored model beverage. Gas chromatography/mass spectrometry analysis and orthonasal sensory tetrad tests further indicated the addition of the degradation compounds did not significantly alter the volatile aroma composition or orthonasal perception, respectively. Altogether, subthreshold unimodal and cross-modal integration of multisensory percepts were supported to impact the flavor performance of rebaudioside A.

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 a Bitter Peptide Contributing to the Off-Flavor Attributes of Pea Protein Isolates

The aversive bitter taste of pea protein ingredients limits product acceptability. Compounds contributing to the bitter perception of pea protein isolates were investigated. Off-line multi-dimensional sensory-guided preparative liquid chromatography fractionation of a 10% aqueous PPI solution revealed one main bitter compound that was identified by Fourier transform ion cyclotron resonance mass spectrometry and de novo tandem mass spectrometry (MS/MS) sequencing as the 37 amino acid peptide PA1b from pea albumin and further confirmed by synthesis. Quantitative MS/MS analysis reported that the concentration of the bitter peptide was 129.3 mg/L, which was above the determined bitter sensory threshold value of 3.8 mg/L and in agreement with the perceived bitter taste of the sample.

Mono-n-butyl Malate-Derived Compounds from Camu-camu (Myrciaria dubia) Malic Acid: The Alkyl-Dependent Antihyperglycemic-Related Activity

Malic acid derivatives from camu-camu (Myrciaria dubia) fruit exhibited a strong in vitro inhibitory activity toward pancreatic α-amylase and α-glucosidase enzymes. During a bioguided chromatographic fractionation process of the whole fruit (pulp and peelings) polar extract, isomers (S)-4-butoxy-2-hydroxy-4-oxobutanoic acid (1) and (S)-4-butoxy-3-hydroxy-4-oxobutanoic acid (2) (84:16) were isolated and identified as a potent inhibitor of α-amylase (IC₅₀= 11.69 ± 1.75 μg/mL) and α-glucosidase (IC₅₀ = 102.69 ± 4.16 μg/mL). The chemical structures were confirmed by HPLC-ESIMS and ¹H and ¹³C NMR (one- and two-dimensional) analyses. The structure-based virtual screening demonstrated that the aliphatic moiety plays a significant role in the binding mode of the test alkyl malate esters. Compound 1 exhibited the best interaction profile to bind both enzymes, having key structural features to form relevant contacts by involving adequate enzyme-ligand complex stabilization and compactness over time.

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-ɣ-quinide and 4-O-caffeoyl-ɣ-quinide significantly impacted the flavor stability of RTD coffee at subthreshold concentrations.

Identification of non-volatile compounds that impact consumer liking of strawberry preserves: Untargeted LC-MS analysis

Non-volatile compounds that impact the acceptability of strawberry preserves were investigated by untargeted LC-MS flavoromics analysis. Chemical profiles for fifteen strawberry preserves were modeled against consumer liking scores by orthogonal partial least squares (OPLS) with good fit (R²Y = 0.995) and predictive ability (Q² = 0.918). Four chemical compounds predictive of acceptability were identified, by accurate MS and NMR, as secoisolariciresinol monoglucoside, (+)-isolariciresinol monoglucoside, 1-hexanoyl-phloroglucinol-2-O-β-d-glucoside, and the novel compound decanoic acid-4-O-β-d-glucoside. Sensory recombination testing of preserve samples with added levels of the four predictive LC-MS compounds indicated perceivable sensory changes in the flavor profile. Female consumers significantly preferred the recombination preserve with added levels of both predictive GC-MS and LC-MS compounds as compared to the control preserve, demonstrating the applicability of the approach for understanding product liking.

Identification of volatile compounds correlated with consumer acceptability of strawberry preserves: Untargeted GC-MS analysis

Volatile compounds that impact the acceptability of strawberry preserves were investigated by untargeted GC-MS flavoromics analysis. Chemical profiles for fifteen strawberry preserves were modeled against consumer liking scores by orthogonal partial least squares (OPLS) with good fit (R²Y = 0.998) and predictive ability (Q² = 0.853). Ten highly predictive compounds were selected, nine of which were identified, and eight of which were quantified using tandem mass spectrometry. Sensory recombination difference testing revealed that the addition of predictive compounds to an average-liked preserve at levels found in the most-liked preserve induced a perceptible difference to frequent consumers of strawberry jams. One of the highly predictive compounds was identified (MS and synthesis) as a novel linalool oxide product 2-methyl-2-vinyl-tetrahydrofuran with a fruity, herbal-minty, piney aroma and a low odor threshold value.

Untargeted LC-MS based identification of Rebaudioside A degradation products impacting flavor perception during storage

Untargeted LC-MS flavoromics chemical profiling was used to identify compounds predictive of Rebaudioside A (Reb A) flavor instability in an acidified beverage after 6 weeks at 35 °C. High-quality orthogonal partial least squares analysis models were developed from the chemical data and d' values from tetrad sensory panel testing with good predictive ability. The top four highly predictive compounds were selected and identified as Reb A (negatively correlated) and three Reb A degradation compounds (positively correlated), which included a rearrangement, hydration, and an epoxidation/rearrangement of Reb A, termed compounds 1, 2, and 3, respectively. The concentrations of compounds 1-3 in the aged beverages were determined to be below the sensory recognition threshold values. However, sensory recombination testing of compounds 1-3 as a tertiary mixture revealed a perceivably significant flavor change that was aligned with the aged beverage.

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 non-volatile compounds that negatively impact whole wheat bread flavor liking

Untargeted LC-MS flavoromic analysis was utilized to identify chemical compounds that impact consumer liking of whole wheat bread. Chemical fingerprints of thirteen whole wheat breads were modeled against consumer flavor liking scores by orthogonal partial least squares (OPLS) with good fit (R²Y = 0.98) and predictive ability (Q² = 0.95). The four most predictive features (negatively correlated) were identified as 9S,12S,13S-trihydroxy-octadec-10E-enoic acid (pinellic acid), 9S,12S,13S-trihydroxy-octadeca-10E,15Z-dienoic acid, 8R*,9R*,10S*-trihydroxy-octadec-6Z-enoic acid, and 1-(octadeca-9Z,12Z-dienoyl)-sn-glycero-3-phosphocholine. Sensory validation studies including bitter threshold determination and recombination tests confirmed the contribution of these compounds to the perceived bitterness intensity of the bread samples and the overall negative impact on flavor liking. Lipoxygenase activity of the flour was reported to have a significant impact on the formation of the three bitter compounds (trihydroxy fatty acids) in the bread samples.

Characterization of bitter compounds in native and hybrid American hazelnuts

The main objective of this study was to identify compounds that contribute to the bitter taste attributes of American hazelnuts (C. americana) and derived hybrids. Sensory-guided Prep-LC fractionation analysis selected four compounds as bitter that were further identified by MS and NMR as carpinontriol B, 2-(3-hydroxy-2-oxoindolin-3-yl)acetic acid 3-O-6'-galactopyranosyl-2″-(2″oxoindolin-3″yl) acetate, giffonin-2-O-[(α-d-glucopyranosyl)-6'-O-(3-hydroxy-3-methylglutaric acid) and Afzelin, termed compounds 1-4, respectively. The concentrations of compounds 1, 2, 3, and 4 were determined across 88 American hybrid hazelnut genotypes and reported to be present at levels above their bitter threshold values in 94, 75, 25, and 0% of the samples, respectively. Moreover, the concentrations of compounds 1 and 3 were significantly higher for nuts dehusked prior to drying during post-harvest handling, which is expected to result in a higher perceived bitter intensity.

Identification of inhibitors of pinellic acid generation in whole wheat bread

Bitterness is a common aversive flavor attribute of foods associated with low consumer acceptance. Untargeted LC-MS flavoromic profiling was utilized to identify endogenous compounds that influence the generation of the bitter compound 9,12,13-trihydroxy-trans-10-octadecenoic acid (pinellic acid) during bread making. A diverse sample set of wheat germplasm was chemically profiled. The corresponding pinellic acid concentrations after dough formation were modeled by orthogonal partial least squares (OPLS) with good fit (R²Y = 0.8) and predictive ability (Q² = 0.6). The most predictive feature (negatively correlated), postulated to interfere with the biosynthetic pathway, was identified as schaftoside, an apigenin di-C-glycoside. Recombination experiments involving the addition of schaftoside to flour prior to breadmaking resulted in a 26% decrease in pinellic acid formation and significantly lower perceived bitterness intensity in whole wheat bread. This work provides novel understanding of bitter generation pathways in wheat products and new strategies to improve flavor profiles and consumer acceptability.

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-β-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 temperature and water activity on the aroma composition and flavor stability of pea (Pisum sativum) protein isolates during storage

Flavor stability of pea protein isolates (PPIs) during storage was investigated. Two commercial PPIs were stored at three water activities (0.128-0.501) under refrigerated (7 °C) and accelerated (37 °C) temperatures for 12 weeks. Eleven aroma compounds were monitored by gas chromatography-tandem mass spectrometry (GC/MS/MS) and results revealed significant changes in the aroma concentrations among the PPI samples during storage. In agreement with the chemical changes, significant differences in orthonasal aroma profiles were demonstrated using a sensory difference-from-control test. The sample stored under accelerated storage temperature (37 °C) and at the highest water activity showed the greatest degree of aroma change. An aroma recombination sensory study indicated the generation of two specific compounds, 1-octen-3-ol and nonanal, along with the degradation of 2-4-decadienal resulted in sensory changes during storage indicating lipid oxidation was the main mechanism of flavor instability in the PPI samples.

Identification of Aroma Differences in Refined and Whole Grain Extruded Maize Puffs

Differences in the aroma profiles of extruded maize puffs made from refined grain and whole grain flour were investigated. Gas chromatography/mass spectrometry/olfactometry (GC/MS/O) analysis reported 13 aroma compounds with a flavor dilution (FD) value ≥16. Quantitative analysis identified eight compounds as statistically different, of which seven compounds were higher in concentration in the whole grain sample. Sensory recombination and descriptive analysis further supported the analytical data, with higher mean aroma intensities for cooked, corn chip, roasted, and toasted attributes for the whole grain sample. Generally, the compounds responsible for perceived differences in whole grain maize extruded puffs were associated with increased levels of Maillard reaction products, such as 2-ethyl-3,5-dimethylpyrazine and 2-acetyl-2-thiazoline.

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.

Comparison of the Aroma Profiles of Intermediate Wheatgrass and Wheat Bread Crusts

The aroma profiles of bread crusts made from intermediate wheatgrass (Thinopyrum intermedium) and whole wheat (Triticum aestivum) flours were compared. Based on gas chromatography/mass spectrometry/olfactometry analysis, twenty-four odorants were identified and further quantified. The concentrations of seventeen compounds were significantly different between intermediate wheatgrass and whole wheat bread crusts, of which sixteen compounds were higher in the whole wheat sample. The aroma profiles of the bread samples were subsequently characterized using sensory descriptive analysis (DA) and indicated that the roasted attribute was perceived at a significantly higher intensity in the whole wheat sample due to a greater amount of Maillard reaction compounds. Alternatively, bran and green notes were perceived at higher intensities in the intermediate wheatgrass sample, however they were not attributed to the presence of specific compounds but rather to a change in the aroma composition. Aroma recombination DA of the whole wheat and intermediate wheatgrass aroma models was similar to the original aroma profiles of the bread samples, demonstrating the sensory relevance of the identified odorants.

Mechanisms non-enzymatic browning in orange juice during storage

The role of Reactive Carbonyl Species (RCS) derived from the Maillard reaction and ascorbic acid degradation on brown color formation was investigated in orange juice during storage. Eight RCS were monitored in aseptic juice over an 8-week period under refrigerated (4 °C) and accelerated conditions (35 °C). Significant changes in RCS concentrations were reported and positively correlated with color formation. Recombination experiments demonstrated the significant role of 3-deoxyglucosone and acetol on color formation as well as their interactions with glyoxal and methylglyoxal that lead to an increase in browning. Isotopic enrichment techniques further identified fructose as the main precursor of RCS, indicating the important role of Maillard reaction as a mechanism of non-enzymatic browning during orange juice storage. Finally, among the amino acids, tryptophan and glutamine showed the largest percentage losses in orange juice during storage and were reported to significantly impact the RCS composition and color formation.

Seasonal variation in equine follicular fluid proteome

BACKGROUND

Proteomic studies of follicular fluid (FF) exist for several species, including the horse; however, the seasonal influence on FF proteome has not been explored in livestock. The application of high-throughput proteomics of FF in horse has the potential to identify seasonal variations of proteins involved in follicle and oocyte growth.

METHODS

This study (i) profiles the proteomes of equine FF collected from dominant growing follicles during the spring anovulatory season (SAN), and spring (SOV), summer (SUM), and fall (FOV) ovulatory seasons; and (ii) identifies season-dependent regulatory networks and associated key proteins.

RESULTS

Regardless of season, a total of 90 proteins were identified in FF, corresponding to 63, 72, 69, and 78 proteins detected in the SAN, SOV, SUM, and FOV seasons, respectively. Fifty-two proteins were common to all seasons, a total of 13 were unique to either season, and 25 were shared between two seasons or more. Protein-to-protein interaction (PPI) analysis indicated the likely critical roles of plasminogen in the SAN season, the prothrombin/plasminogen combination in SUM, and plasminogen/complement C3 in both SOV and FOV seasons. The apolipoprotein A1 appeared crucial in all seasons. The present findings show that FF proteome of SUM differs from other seasons, with FF having high fluidity (low viscosity).

CONCLUSIONS

The balance between the FF contents in prothrombin, plasminogen, and coagulation factor XII proteins favoring FF fluidity may be crucial at the peak of the ovulatory season (SUM) and may explain the reported lower incidence of hemorrhagic anovulatory follicles during the SUM season.

Identification of objectionable flavors in purported spontaneous oxidized flavor bovine milk

Spontaneous oxidized flavor (SOF) has been reported over the past 5 decades as a sporadic objectionable flavor problem in bovine milk. Parameters previously reported to influence SOF development in milk have been contradictory, limiting the ability to monitor and develop mitigation strategies. The current paper investigates the causative compounds associated with milk identified as SOF milk in the Midwest dairy region of the United States. Based on GC/MS-olfactometry analysis, endo-borneol, 2-methylisoborneol, and α-terpineol were identified as the off-flavor compounds. Sensory recombination studies further confirmed the sensory contribution of these compounds to the noted off-flavor attributes in the original milk, which were described as "green," "musty," and "unclean." These compounds are known microbial-derived flavor taints, indicating oxidation was not the origin of the objectionable flavor in the milk. This noted misclassification of the milk as SOF indicates the challenge of defining flavor defects without the identification of the active compounds.

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.

Effects of polyol type and particle size on flavor release in chewing gum

The influence of polyol type and particle size on the flavor release profile of chewing gum was investigated in vivo. Four chewing gum samples with an average particle size of 62 or 246 μm for sorbitol and 57 or 184 μm for mannitol were analyzed. Chewing gum formulated with mannitol, in general, had a higher aroma release than chewing gum formulated with sorbitol. Polyol type did not influence the release profile of the high intensity sweeteners (HIS) aspartame and acesulfame K. However, a smaller particle size resulted in a significantly higher release of HIS. The release rate of polyol was not significantly changed by particle size. Sensory analysis was also in agreement with the HIS delivery; the smaller particle size polyol gum was significantly higher in perceived sweetness intensity. In summary, two physical attributes of polyols (solubility and surface area) were reported to uniquely alter the delivery of aroma and taste stimuli.

Identification and Validation of Sensory-Active Compounds from Data-Driven Research: A Flavoromics Approach

In this study, highly predictive LC-MS features (retention time_ m/ z) derived from untargeted chemical fingerprinting-multivariate analysis (MVA) previously used to model flavor changes in citrus fruits related to aging (freshness) were further isolated and analyzed for sensory impact, followed by structural elucidation. The top 10 statistical features from two MVA approaches, partial least-squares data analysis (PLS-DA) and Random Forrest (RF), were purified to approximately 70% via multidimensional liquid chromatography-mass-directed fractionation to screen for sensory activity. When added to a 'fresh' orange flavor model system, 50-60% of the isolates were reported to cause a sensory change. From the subset of the actives identified, two compounds were selected, on the basis of statistical relevance, that were further purified to >97% for identification (MS, NMR) and for sensory descriptive analysis (DA). The compounds were identified as nomilin glucoside and a novel ionone glucoside. DA evaluation in the recombination orange model indicated both compounds statistically suppressed the perceived intensity of the "orange character" attribute, whereas the novel ionone glycoside also decreased the intensity of the floral character while increasing the green bean attribute intensity.

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 Protein-Lipid-Salt Interactions on Sodium Availability in the Mouth and Consequent Perception of Saltiness: In Solutions

The influence of protein-sodium interactions on the availability of sodium in the aqueous phase of liquid samples and consequently on the perception of saltiness was investigated. The aqueous effluents of casein and casein emulsion-salt solutions were monitored for sodium availability from a tongue column system. In the aqueous protein-salt solutions, increasing the protein/salt ratio from 1:1 to 5:1 or 10:1 significantly decreased the initial salt concentration in the effluent and resulted in a higher salt concentration in the effluent over time. Sensory analysis was in agreement. Samples with increased protein were rated as having significantly lower initial saltiness and a higher salty aftertaste. However, when casein was formulated as an emulsion, the initial release of sodium in the effluent was enhanced (compared to nonemulsified protein). Increasing the emulsion interfacial area (more hydrophilic segments of the protein were structured into the aqueous phase) resulted in a higher salt concentration in the aqueous phase and greater perceived saltiness intensity. In summary, protein interactions, specifically ionic, were reported as food interactions that influence salt perception and provide a basis to develop higher flavor quality low-sodium food products.

Effect of Protein-Lipid-Salt Interactions on Sodium Availability in the Mouth and Consequent Perception of Saltiness: As Affected by Hydration in Powders

There is a broad need to reformulate lower sodium food products without affecting their original taste. The present study focuses on characterizing the role of protein-salt interactions on the salt release in low-moisture systems and saltiness perception during hydration. Sodium release from freeze-dried protein powders and emulsion powders formulated at different protein/lipid ratios (5:0 to 1:4) were characterized using a chromatography column modified with a porcine tongue. Emulsion systems with protein structured at the interface were found to have faster initial sodium release rates and faster hydration and were perceived to have a higher initial salt intensity with a lower salty aftertaste. In summary, exposure of the hydrophilic segments of the interface-structured proteins in emulsions was suggested to facilitate hydration and release of sodium during dissolution of low-moisture powder samples.

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 modulating maillard-catechin reaction products

The influence of thermally induced reaction products of a known dietary bitter compound, catechin, on bitterness perception was investigated. Catechin was reacted in low-moisture simple Maillard models (200 °C for 15 min) consisting of glycine and a reducing sugar (D-glucose, D-xylose, or D-galactose). Based on liquid chromatrography-mass spectrometry (LC-MS) isotopic labeling techniques, eight reaction products were identified and subsequently structurally elucidated by tandem LC-MS/MS and two-dimensional NMR analysis; six were report to be flavan-3-ol-spiro-C-glycosides reaction products. One of the spiro products was reported to significantly suppress the perceived bitterness intensity of a caffeine solution. Additionally, this specific spiro product was further identified in cocoa and reported to increase in concentration during bean roasting.

Control of Maillard-type off-flavor development in ultrahigh-temperature-processed bovine milk by phenolic chemistry

The application of phenolic compounds to suppress Maillard chemistry and off-flavor development in ultrahigh-termperature (UHT)-processed milk during processing and storage was investigated. Five phenolic compounds were examined for structure-reactivity relationships (catechin, genistein, daidzein, 1,2,3-trihydroxybenzene, and 1,3,5-trihydroxybenzene). The levels of key transient Maillard reaction (MR) intermediates (reactive carbonyl species) and select off-flavor markers (methional, 2-acetyl-2-thiazoline, 2-acetyl-1-pyrroline) were quantified by LC-MS/MS and GC-MS/ToF, respectively. The addition of phenolic compounds prior to UHT processing significantly reduced the concentration of MR intermediates and related off-flavor compounds compared to a control sample (p < 0.05). All phenolic compounds demonstrated unique structure reactivity and, notably, those with a more activated A-ring for aromatic electrophilic substitution (catechin, genistein, and 1,3,5-trihydroxybenzene) showed the strongest suppression effect on the off-flavor markers and reactive carbonyl species. Sensory studies were in agreement with the analytical data. The cooked flavor intensity was rated lower for the recombination model samples of the catechin-treated UHT milk compared to the control UHT milk. Additionally, consumer acceptability studies showed catechin-treated UHT milk to have significantly higher liking scores when compared the control sample (Fisher's LSD = 0.728).

Identification of bitter peptides in aged cheddar cheese

The compounds responsible for the bitter taste of aged "sharp" Cheddar cheese were characterized. Sensory-guided fractionation techniques using gel permeation chromatography and multi-dimension semi-preparative reversed-phase high-performance liquid chromatography revealed the presence of multiple bitter compounds. The compounds with the highest perceived bitterness intensity were identified by tandem mass spectrometry de novo peptide sequencing as GPVRGPFPIIV, YQEPVLGPVRGPFPI, MPFPKYPVEP, MAPKHKEMPFPKYPVEPF, and APHGKEMPFPKYPVEPF; all originated from β-casein. Subsequent quantitative liquid chromatography-tandem mass spectrometry analysis reported that the concentrations of GPVRGPFPIIV, YQEPVLGPVRGPFPI, and MPFPKYPVEP increased during maturation by 28.7-, 3.1-, and 1.8-fold, respectively. When directly compared to young "mild" Cheddar, APHGKEMPFPKYPVEPF was reported only in the sharp Cheddar cheese, whereas the concentration of MAPKHKEMPFPKYPVEPF did not change. Further taste re-engineering sensory experiments confirmed the importance of the identified peptides to the bitterness of sharp Cheddar. The bitter intensity of the aged "sharp" Cheddar model (mild Cheddar with equivalent concentrations of the five bitter peptides in the sharp sample) was rated as not significantly different from the authentic sharp Cheddar cheese. Among the five peptides, GPVRGPFPIIV was reported to be the main contributor to the bitterness intensity of sharp Cheddar. Furthermore, a difference from control sensory test also confirmed the significance of the bitter taste to the overall perception of aged Cheddar flavor. The sharp Cheddar model was reported to be significantly more similar to aged "sharp" Cheddar in comparison to the young "mild" Cheddar cheese sample.

Identification of bitter peptides in whey protein hydrolysate

Bitterness of whey protein hydrolysates (WPH) can negatively affect product quality and limit utilization in food and pharmaceutical applications. Four main bitter peptides were identified in a commercial WPH by means of sensory-guided fractionation techniques that included ultrafiltration and offline two-dimensional reverse phase chromatography. LC-TOF-MS/MS analysis revealed the amino acid sequences of the bitter peptides were YGLF, IPAVF, LLF, and YPFPGPIPN that originated from α-lactalbumin, β-lactoglobulin, serum albumin, and β-casein, respectively. Quantitative LC-MS/MS analysis reported the concentrations of YGLF, IPAVF, LLF, and YPFPGPIPN to be 0.66, 0.58, 1.33, and 2.64 g/kg powder, respectively. Taste recombination analysis of an aqueous model consisting of all four peptides was reported to explain 88% of the bitterness intensity of the 10% WPH solution.

Conjugated linoleic acids alter body composition differently according to physiological age in Moulard ducks

Conjugated linoleic acids (CLA) have been shown to have remarkable yet inconsistent metabolic effects in mice, rats, hamsters, chickens, cattle, and humans. In particular, effects on lipogenesis vary with tissue, physiological state, and species. In this study we tested the hypothesis that CLA would differentially affect ducks of the same genetic background but of differing age. Growing (7 wk) and maintenance (11 wk) Moulard ducks were grouped by age and fed a standard diet supplemented with 5% soybean oil (control) or 5% CLA isomer mixture. Birds were slaughtered after 3 or 6 wk for assessment of body composition including adipose, liver, viscera, and empty carcass weight. Serum nonesterified fatty acid (NEFA) and glucose concentrations were evaluated, and gene targets were cloned from the duck to use in quantifying mRNA abundance for genes involved in lipogenesis (fatty acid synthase, FAS; acetyl-CoA carboxylase, ACC) and lipid oxidation (carnitine palmitoyl transferase-1, CPT-1) in liver tissue from maintenance birds. After 3 wk, the growing CLA group exhibited a 24% decrease in dissectible adipose tissue (P < 0.05), whereas maintenance birds showed no significant diet effect. After 6 wk, the growing CLA group exhibited a 20% increase in liver mass compared with the control (P < 0.05), but no diet effect on adipose tissue. Maintenance birds receiving dietary CLA had a 42% decrease in adipose tissue mass after 6 wk; increased serum NEFA, ACC, and CPT-1 mRNA after 3 and 6 wk (P < 0.05); and increased FAS mRNA after 3 wk of treatment (P < 0.05). These data indicate that CLA have potent effects on lipid metabolism in ducks, but these effects differ depending on physiological age.