Metabolomic approach for determination of key volatile compounds related to beef flavor in glutathione-Maillard reaction products

The potential meat flavoring derived from Maillard reaction products of rice protein isolate hydrolysate-xylose via the regulation of temperature and cysteine

Maillard reaction products (MRPs) derived from rice protein isolate hydrolysate and D-xylose, with or without L-cysteine, were developed as a potential meat flavoring. The combined impact of temperature (80-140 °C) and cysteine on fundamental physicochemical characteristics, antioxidant activity, and flavor of MRPs were investigated through assessments of pH, color, UV-visible spectra, fluorescence spectra, free amino acids, volatile compounds, E-nose, E-tongue, and sensory evaluation. Results suggested that increasing temperature would reduce pH, deepen color, promote volatile compounds formation, and reduce the overall umami and bitterness. Cysteine addition contributed to the color inhibition, enhancement of DPPH radical-scavenging activity and reducing power, improvement in mouthfulness and continuity, reduction of bitterness, and the formation of sulfur compounds responsible for meaty flavor. Overall, MRPs prepared at 120 °C with cysteine addition could be utilized as a potential meat flavoring with the highest antioxidant activity and relatively high mouthfulness, continuity, umami, meaty aroma, and relatively low bitterness.

Efficient Formation of N-(1-Deoxy-d-ribulos-1-yl)-Glutathione via Limited Oxidation and Degradation of Glutathione during the Atmospheric-Vacuum Thermal Reaction

The efficient preparation of the ribose-glutathione (Rib-GSH) Amadori rearrangement product (RG-ARP) as a potent precursor of meaty flavor was studied through the atmospheric-vacuum thermal reaction. Liquid chromatography-mass spectrometry (LC-MS) analysis revealed that the oxidation and degradation of GSH occurred during the preparation of RG-ARP via the atmospheric thermal reaction, especially at a low molar ratio of Rib to GSH and high reaction temperature. The RG-ARP and the ARPs derived from the products of GSH oxidation and degradation with the participation of Rib were identified by MS/MS as N-(1-deoxy-d-ribulos-1-yl)-glutathione, N-(1-deoxy-d-ribulos-1-yl)-cysteinylglycine, and N-(1-deoxy-d-ribulos-1-yl)-glutathione disulfide. The selective formation of RG-ARP was disrupted due to the multiple consumption pathways of GSH and Rib. The removal of water and the reduction of oxygen content during vacuum dehydration exhibited an obvious inhibitory effect on the oxidation of cysteinyl and the cleavage of glutamyl, limiting the oxidation and degradation of GSH. Meanwhile, the rapid evaporation of water promoted the molecular collision between the reactants, which allowed the glycation reaction of GSH to be advanced and fragmentation of RG-ARP to be inhibited at a mild dehydration temperature. Accordingly, the atmospheric-vacuum thermal reaction was proposed to limit the generation of secondary byproducts and enhance the yield of RG-ARP, enabling the RG-ARP yield to reach 49.23% at 80 °C and a molar ratio of 2:1 (Rib/GSH) for 20 min.

Insight into the differences of meat quality between Qinghai white Tibetan sheep and black Tibetan sheep from the perspective of metabolomics and rumen microbiota

The purpose of this study was to investigate the differences in meat quality between two local breeds of Tibetan sheep, the White Tibetan sheep and the Black Tibetan sheep in Qinghai, and to search for metabolic mechanisms that produce meat quality differences by analyzing differential metabolites and key rumen microorganisms. The meat quality results showed that one breed, SG73, was superior to the other (WG). Further investigation identified differences in the composition of muscle metabolites and rumen microorganisms between the two Tibetan sheep breeds. It also regulates muscle tenderness, water retention, fat content and the composition and content of AA and FA through two major metabolic pathways, AA metabolism and carbohydrate metabolism. These findings could be beneficial for the development of breeding strategies for Tibetan sheep in Qinghai in the future.

Emerging trends and applications of metabolomics in food science and nutrition

The study of all chemical processes involving metabolites is known as metabolomics. It has been developed into an essential tool in several disciplines, such as the study of plant physiology, drug development, human diseases, and nutrition. The field of food science, diagnostic biomarker research, etiological analysis in the field of medical therapy, and raw material quality, processing, and safety have all benefited from the use of metabolomics recently. Food metabolomics includes the use of metabolomics in food production, processing, and human diets. As a result of changing consumer habits and the rising of food industries all over the world, there is a remarkable increase in interest in food quality and safety. It requires the employment of various technologies for the food supply chain, processing of food, and even plant breeding. This can be achieved by understanding the metabolome of food, including its biochemistry and composition. Additionally, Food metabolomics can be used to determine the similarities and differences across crop kinds, as an indicator for tracking the process of ripening to increase crops' shelf life and attractiveness, and identifying metabolites linked to pathways responsible for postharvest disorders. Moreover, nutritional metabolomics is used to investigate the connection between diet and human health through detection of certain biomarkers. This review assessed and compiled literature on food metabolomics research with an emphasis on metabolite extraction, detection, and data processing as well as its applications to the study of food nutrition, food-based illness, and phytochemical analysis. Several studies have been published on the applications of metabolomics in food but further research concerning the use of standard reproducible procedures must be done. The results published showed promising uses in the food industry in many areas such as food production, processing, and human diets. Finally, metabolome-wide association studies (MWASs) could also be a useful predictor to detect the connection between certain diseases and low molecular weight biomarkers.

Roles of sulfur-containing compounds in fermented beverages with 2-furfurylthiol as a case example

Aroma is a critical component of the flavor and quality of beverages. Among the volatile chemicals responsible for fragrance perception, sulfur compounds are unique odorants due to their extremely low odor threshold. Although trace amounts of sulfur compounds can enhance the flavor profile of beverages, they can lead to off-odors. Sulfur compounds can be formed via Maillard reaction and microbial metabolism, imparting coffee aroma and altering the flavor of beverages. In order to increase the understanding of sulfur compounds in the field of food flavor, 2-furfurylthiol (FFT) was chosen as a representative to discuss the current status of their generation, sensory impact, enrichment, analytical methods, formation mechanisms, aroma deterioration, and aroma regulation. FFT is comprehensively reviewed, and the main beverages of interest are typically baijiu, beer, wine, and coffee. Challenges and recommendations for FFT are also discussed, including analytical methods and mechanisms of formation, interactions between FFT and other compounds, and the development of specific materials to extend the duration of aroma after release.

Free-Choice Feeding of Whole Grains Improves Meat Quality and Intestinal Development of Pigeon Squabs Compared with Complete Pelleted Feed

Effects of different feeding strategies on meat quality and intestinal development in pigeon squabs were investigated. 120 pairs of pigeons with two squabs each were assigned to five groups (four free-choice feeding systems and one complete feeding system): T1 (corn, pea, wheat, and pelleted feed), T2 (corn, wheat, and pelleted feed), T3 (corn, pea, and pelleted feed), T4 (corn and pelleted feed), and T5 (complete pelleted feed). Compared with T5, the diet in T4 made the breast meat redder and more yellow (p < 0.05). T2 and T4 resulted in an enhanced total superoxide dismutase activity of meat. Breast muscle in T1 and T2 was determined to have higher contents of nonessential amino acids, glycine, alanine, and glutamic acid (p < 0.05). The contents of the essential amino acids, lysine, threonine, valine, histidine, and arginine were also higher in T1 (p < 0.05). Villus height, surface area, and alkaline phosphatase activity of the duodenum and jejunum in T2 were the highest among the treatments (p < 0.05). In conclusion, free-choice feeding system can improve the meat quality and intestinal development of pigeon squabs, but which combination method of whole grains to use in the production depends on the feeding purpose.

Effect of Aliphatic Aldehydes on Flavor Formation in Glutathione-Ribose Maillard Reactions

The Maillard reaction (MR) is affected by lipid oxidation, the intermediate products of which are key to understanding this process. Herein, nine aliphatic aldehyde−glutathione−ribose models were designed to explore the influence of lipid oxidation products with different structures on the MR. The browning degree, fluorescence degree, and antioxidant activity of the MR products were determined, and the generated volatile organic compounds (VOCs) and nonvolatile compounds were analyzed by gas chromatography-mass spectrometry and ultra-performance liquid chromatography-mass spectrometry. A total of 108 VOCs and 596 nonvolatile compounds were detected. The principal component and hierarchical clustering analyses showed that saturated aldehydes mainly affected the VOCs generated by the MR, while unsaturated aldehydes significantly affected the nonvolatile compounds, which changed the taste attributes of the MR products. Compared with the control group, the addition of unsaturated aldehydes significantly increased the sourness score and decreased the umami score. In addition, the addition of unsaturated aldehydes decreased the antioxidant activity and changed the composition of nonvolatile compounds, especially aryl thioethers and medium chain fatty acids, with a strong correlation with umami and sourness in the electronic tongue analysis (p < 0.05). The addition of aliphatic aldehydes reduces the ultraviolet absorption of the intermediate products of MR browning, whereas saturated aldehydes reduce the browning degree of the MR products. Therefore, the flavor components of processed foods based on the MR can be effectively modified by the addition of lipid oxidation products.

Metabolites Analysis on Water-Holding Capacity in Beef Longissimus lumborum Muscle during Postmortem Aging

Currently, the metabolomic research on water-holding capacity (WHC) of beef during postmortem aging is still insufficient. In this paper, the kit method was adopted for energy metabolites testing, the ultra-high-performance liquid chromatography (UHPLC) system was used for sample separation, and the mass spectrometer was applied to collect the primary and secondary spectra of the samples. The results showed that lactic acid reached saturation at day 2 postmortem, while energy metabolites changed significantly within day 2 postmortem (p < 0.05). Based on these findings, it was suggested that the energy metabolism qualities of the beef had already achieved a largely stable state at around day 2 postmortem. Then, through metabolomic analysis, 25 compounds were differentially abundant at days 0, 0.5, 1, and 2 during postmortem aging. Within the period of day 0−2 postmortem, the purine metabolism in beef was relatively active until 0.5 d postmortem, while glycolysis metabolism remained active until day 2 postmortem. The functions of the identified metabolites contribute to a more detailed molecular view of the processes behind WHC and are a valuable resource for future investigations into the flavor of postmortem beef.

Current State of Metabolomics Research in Meat Quality Analysis and Authentication

In the past decades, as an emerging omic, metabolomics has been widely used in meat science research, showing promise in meat quality analysis and meat authentication. This review first provides a brief overview of the concept, analytical techniques, and analysis workflow of metabolomics. Additionally, the metabolomics research in quality analysis and authentication of meat is comprehensively described. Finally, the limitations, challenges, and future trends of metabolomics application in meat quality analysis and meat authentication are critically discussed. We hope to provide valuable insights for further research in meat quality.

Unraveling the chemosensory characteristics of strong-aroma type Baijiu from different regions using comprehensive two-dimensional gas chromatography-time-of-flight mass spectrometry and descriptive sensory analysis

Comprehensive 2D gas chromatography-time-of-flight mass spectrometry was combined with descriptive sensory analysis to elucidate the specificity of strong-aroma type Baijiu (Chinese liquor) from different regions, based on regionally distinct flavor characterized by chemical and sensory profiles. Numerous potential aroma compounds (262) were identified, among which 58 aroma compounds were significantly different between the samples from Sichuan and Jianghuai regions. Relationships between these potential aroma compounds and sensory attributes were investigated by partial least squares regression and network analysis. The compounds that dominantly contributed to the important sensory attributes were identified. The high pyrazines, furanoids, and carbonyls amounts contributed to the high intensities of the cellar, toasted, and grain aroma profiles of the Sichuan region samples, while the high ester and alcohol levels contributed to the fruity and floral aroma profiles of the Jianghuai region samples. This approach may have practical application in flavor characterization of other alcoholic beverages.

MEATabolomics: Muscle and Meat Metabolomics in Domestic Animals

In the past decades, metabolomics has been used to comprehensively understand a variety of food materials for improvement and assessment of food quality. Farm animal skeletal muscles and meat are one of the major targets of metabolomics for the characterization of meat and the exploration of biomarkers in the production system. For identification of potential biomarkers to control meat quality, studies of animal muscles and meat with metabolomics (MEATabolomics) has been conducted in combination with analyses of meat quality traits, focusing on specific factors associated with animal genetic background and sensory scores, or conditions in feeding system and treatments of meat in the processes such as postmortem storage, processing, and hygiene control. Currently, most of MEATabolomics approaches combine separation techniques (gas or liquid chromatography, and capillary electrophoresis)-mass spectrometry (MS) or nuclear magnetic resonance (NMR) approaches with the downstream multivariate analyses, depending on the polarity and/or hydrophobicity of the targeted metabolites. Studies employing these approaches provide useful information to monitor meat quality traits efficiently and to understand the genetic background and production system of animals behind the meat quality. MEATabolomics is expected to improve the knowledge and methodologies in animal breeding and feeding, meat storage and processing, and prediction of meat quality.

Effects of cottonseed meal on slaughter performance, meat quality, and meat chemical composition in Jiangnan White goslings

Cottonseed meal (CSM), which is an unconventional protein material with abundant sources, high protein content, and a relatively cheap price, can be used in poultry diets. The aim of this study was to investigate the effects of CSM on slaughter performance, meat quality and meat chemical composition in Jiangnan White goslings. A total of 300 healthy 28-day-old male goslings were randomly divided into 5 treatments, with 6 pens containing 10 geese each. Five isonitrogenous and isocaloric experimental diets were formulated such that 0% (a corn-soybean meal basal diet, control), 25% (CSM25), 50% (CSM50), 75% (CSM75), and 100% (CSM100) protein from soybean meal was replaced with CSM (corresponding to 0, 6.73, 13.46, 20.18, and 26.91% CSM in the feed, respectively). On day 70, 1 goose from each pen (6 geese per treatment) was randomly selected and killed to measure the slaughter performance, meat quality, and the meat amino acid (AA) and fatty acid (FA) compositions. The results showed that dietary CSM did not affect the slaughter performance or meat quality of geese (P > 0.05). The fat content of breast muscle in the CSM100 group was higher than that in the control group (P < 0.05). A concentration of 13.46% or more dietary CSM increased the threonine content but decreased the cysteine content, and 20.18% dietary CSM also decreased the valine content (P < 0.05). Dietary CSM concentration had no effect on the content of total saturated FAs (SFAs, P > 0.05), but 20.18 and 26.91% dietary CSM increased the content of total monounsaturated FAs and decreased the content of total polyunsaturated FAs (PUFAs) and PUFA/SFA in the breast muscle of geese (P < 0.05). In conclusion, dietary CSM did not affect the slaughter performance or meat quality of geese, but the replacement of soybean meal with CSM in whole or high proportion altered the composition of AAs and FAs in breast muscle.

Effect of Gender, Rearing, and Cooking on the Metabolomic Profile of Porcine Muscles

To clarify the relationship between the fiber type composition and meat quality, we performed metabolomic analysis using porcine longissimus dorsi (LD) muscles. In the LD of pigs raised outdoors, the expression of myosin heavy chain (MyHC)1 (slow-twitch fiber marker protein) was significantly increased compared with that of MyHC1 in pigs raised in an indoor pen, suggesting that rearing outdoors could be considered as an exercise treatment. These LD samples were subjected to metabolomic analysis for examining the profile of most primary and secondary metabolites. We found that the sex of the animal and exercise stimulation had a strong influence on the metabolomic profile in the porcine skeletal muscles, and this difference in the metabolomic profile is likely in part due to the changes in the muscle fiber type. We also examined the effects of cooking (70 °C for 1 h). The effect of exercise on the metabolomic profile was also maintained in the cooked muscle tissues. Cooking treatment resulted in an increase in some of the metabolite levels while decreasing in some other metabolite levels. Thus, our study could indicate the effect of the sex of the animal, exercise stimulus, and cooking on the metabolomic profile of pork meat.

Characterization and Discrimination of Chinese Marinated Pork Hocks by Volatile Compound Profiling Using Solid Phase Microextraction Gas Chromatography-Mass Spectrometry/Olfactometry, Electronic Nose and Chemometrics

The primary aim of this study was to investigate volatile constituents for the differentiation of Chinese marinated pork hocks from four local brands, Dahongmen (DHM), Daoxiangcun (DXC), Henghuitong (HHT) and Tianfuhao (TFH). To this end the volatile constituents were evaluated by gas chromatography-mass spectrometry/olfactometry (GC-MS/O), electronic nose (E-nose) and chemometrics. A total of 62 volatile compounds were identified and quantified in all pork hocks, and 24 of them were considered as odour-active compounds because their odour activity values (OAVs) were greater than 1. Hexanal (OAV at 3.6⁻20.3), octanal (OAV at 30.3⁻47.5), nonanal (OAV at 68.6⁻166.3), 1,8-cineole (OAV at 36.4⁻133.3), anethole (OAV at 5.9⁻28.3) and 2-pentylfuran (OAV at 3.5⁻29.7) were the key odour-active compounds contributing to the integral flavour of the marinated pork hocks. According to principal component analysis (PCA) and partial least squares-discriminant analysis (PLS-DA) of GC-MS/O and E-nose data, the results showed that the marinated pork hocks were clearly separated into three groups: DHM, HHT, and DXC-TFH. Nine odour-active compounds, heptanal, nonanal, 3-carene, d-limonene, β-phellandrene, p-cymene, eugenol, 2-ethylfuran and 2-pentylfuran, were determined to represent potential flavour markers for the discrimination of marinated pork hocks. This study indicated the feasibility of using GC-MS/O coupled with the E-nose method for the differentiation of the volatile profile in different brands of marinated pork hocks.

Nontargeted Detection Methods for Food Safety and Integrity

Nontargeted workflows for chemical hazard analyses are highly desirable in the food safety and integrity fields to ensure human health. Two different analytical strategies, nontargeted metabolomics and chemical database filtering, can be used to screen unknown contaminants in food matrices. Sufficient mass and chromatographic resolutions are necessary for the detection of compounds and subsequent componentization and interpretation of candidate ions. Analytical chemistry–based technologies, including gas chromatography–mass spectrometry (GC-MS), liquid chromatography–mass spectrometry (LC-MS), nuclear magnetic resonance (NMR), and capillary electrophoresis–mass spectrometry (CE-MS), combined with chemometrics analysis are being used to generate molecular formulas of compounds of interest. The construction of a chemical database plays a crucial role in nontargeted detection. This review provides an overview of the current sample preparation, analytical chemistry–based techniques, and data analysis as well as the limitations and challenges of nontargeted detection methods for analyzing complex food matrices. Improvements in sample preparation and analytical platforms may enhance the relevance of food authenticity, quality, and safety.

Investigation of low molecular weight peptides (<1 kDa) in chicken meat and their contribution to meat flavor formation

BACKGROUND

Low molecular weight peptides (LMWPs) (<1 kDa) generated in meat during chilled conditioning can act as flavor precursors in the Maillard reaction with a potential contribution to key volatile organic compound (VOC) formation upon heating. Liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF-MS) successfully detected 44 LMWPs in chicken breast and thigh muscles stored at 4 °C for up to 6 days. Carnosine (350 mg per 100 g), glutathione (GSH, 20 mg per 100 g) (concentrations based on reported values in the literature) and cysteine glycine (Cys Gly, 5 mg per 100 g) (concentration based on results from LC/QTOF-MS) were used in model systems containing ribose (25 mg per 100 g). The three model systems were heated at 180 °C for 2 h at pH 6.3. VOCs were measured by simultaneous distillation solvent extraction/gas chromatography/mass spectrometry.

RESULTS

Of 33 VOCs detected, 26 were significantly different (P ≤ 0.05) between the three peptides. The majority of nitrogen-containing volatiles, pyrazines and pyridines, dominated the carnosine mixture, while sulfur-containing VOCs dominated the GSH and Cys Gly peptide mixtures.

CONCLUSION

Known key aroma compounds such as thiazole (meaty), 2-methyl-3-furanthiol (beef and meat), 2-furfurylthiol (roasted), dihydro-2-methyl-3(2H)-thiophenone (meaty), 2-acetylthiazole (meaty and roasted) and pyrazine (meaty) were detected under conditions specific to aged and thermally treated chicken, suggesting a potential contribution to the overall sensory quality of cooked meat. © 2018 Society of Chemical Industry.

Metabolomic approach to key metabolites characterizing postmortem aged loin muscle of Japanese Black (Wagyu) cattle

OBJECTIVE

Meat quality attributes in postmortem muscle tissues depend on skeletal muscle metabolites. The objective of this study was to determine the key metabolic compounds and pathways that are associated with postmortem aging and beef quality in Japanese Black cattle (JB; a Japanese Wagyu breed with highly marbled beef).

METHODS

Lean portions of Longissimus thoracis (LT: loin) muscle in 3 JB steers were collected at 0, 1, and 14 days after slaughter. The metabolomic profiles of the samples were analyzed by capillary electrophoresis time-of-flight mass spectrometry, followed by statistical and multivariate analyses with bioinformatics resources.

RESULTS

Among the total 171 annotated compounds, the contents of gluconic acid, gluconolactone, spermidine, and the nutritionally vital substances (choline, thiamine, and nicotinamide) were elevated through the course of postmortem aging. The contents of glycolytic compounds increased along with the generation of lactic acid as the beef aging progressed. Moreover, the contents of several dipeptides and 16 amino acids, including glutamate and aromatic and branched-chain amino acids, were elevated over time, suggesting postmortem protein degradation in the muscle. Adenosine triphosphate degradation also progressed, resulting in the generation of inosine, xanthine, and hypoxanthine via the temporal increase in inosine 5'-monophosphate. Cysteine-glutathione disulfide, thiamine, and choline increased over time during the postmortem muscle aging. In the Kyoto encyclopedia of genes and genomes database, a bioinformatics resource, the postmortem metabolomic changes in LT muscle were characterized as pathways mainly related to protein digestion, glycolysis, citric acid cycle, pyruvate metabolism, pentose phosphate metabolism, nicotinamide metabolism, glycerophospholipid metabolism, purine metabolism, and glutathione metabolism.

CONCLUSION

The compounds accumulating in aged beef were shown to be nutritionally vital substances and flavor components, as well as potential useful biomarkers of aging. The present metabolomic data during postmortem aging contribute to further understanding of the beef quality of JB and other breeds.

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.

Metabolomic Profiling as a Possible Reverse Engineering Tool for Estimating Processing Conditions of Dry-Cured Hams

Dry-cured hams are popular among consumers. To increase the attractiveness of the product, objective analytical methods and algorithms to evaluate the relationship between observable properties and consumer acceptability are required. In this study, metabolomics, which is used for quantitative profiling of hundreds of small molecules, was applied to 12 kinds of dry-cured hams from Japan and Europe. In total, 203 charged metabolites, including amino acids, organic acids, nucleotides, and peptides, were successfully identified and quantified. Metabolite profiles were compared for the samples with different countries of origin and processing methods (e.g., smoking or use of a starter culture). Principal component analysis of the metabolite profiles with sensory properties revealed significant correlations for redness, homogeneity, and fat whiteness. This approach could be used to design new ham products by objective evaluation of various features.

Carcass composition and quality of meat from Pekin ducks finished on diets with varying levels of whole wheat grain

The aim of the research was to determine the effect of replacing part of a commercial feed mixture with whole wheat grain on the bodyweight, carcass composition and meat quality of Pekin ducks. A total of 160 1-day-old sexed SM3 Heavy hybrid ducks were used in the study. Two diets were given during the rearing period (36–49 days): (1) a complete commercial diet ad libitum, and (2) restricted amounts of a commercial diet (85%) and whole wheat grain (15%). Each treatment consisted of four replications of 20 birds each. Adding whole wheat grain to the ration resulted in no significant (P > 0.05) changes in bodyweight (3475.8 g), feed conversion ratio (0–49 days, 2.50 kg DM intake/kg liveweight gain) dressing percentage (70.1%) and carcass tissue composition in ducks at 49 days of age. Breast muscle (superficial pectoral muscle) from ducks fed the commercial diet and whole wheat grain was significantly (P < 0.05) lighter in colour (L* = 39.9 vs 38.0) and a deeper yellow colour (b* = 1.7 vs 0.8), as compared with that from birds receiving the complete commercial diet alone. Breast muscle (superficial pectoral muscle and profound pectoral muscle) also had significantly (P < 0.05) higher threonine (3.9 vs 5.1 g/100 g DM) and valine content (4.0 vs 5.0 g/100 g DM). However, leg muscle (thigh and drumstick muscles) from experimental ducks had a significantly (P < 0.05) lower content of crude fat (5.1% vs 4.2%) and collagen (1.5% vs. 1.1%), as well as less glutamic acid (14.2 vs 12.5), proline (3.5 vs 3.2), alanine (3.0 vs 2.5) and arginine (6.5 vs 5.6 g/100 g DM), as compared with the control birds.

High-intensity ultrasound production of Maillard reaction flavor compounds in a cysteine-xylose model system

Application of high intensity ultrasound has shown potential in the production of Maillard reaction odor-active flavor compounds in model systems. The impact of initial pH, sonication duration, and ultrasound intensity on the production of Maillard reaction products (MRPs) by ultrasound processing in a cysteine-xylose model system were evaluated using Response Surface Methodology (RSM) with a modified mathematical model. Generation of selected MRPs, 2-methylthiophene and tetramethyl pyrazine, was optimal at an initial pH of 6.00, accompanied with 78.1 min of processing at an ultrasound intensity of 19.8 W cm(-2). However, identification of volatiles using gas chromatography-mass spectrometry (GC/MS) revealed that ultrasound-assisted Maillard reactions generated fewer sulfur-containing volatile flavor compounds as compared to conventional heat treatment of the model system. Likely reasons for this difference in flavor profile include the expulsion of H2S due to ultrasonic degassing and inefficient transmission of ultrasonic energy.

Analysis of meat flavor compounds in pedigree and two-strain Yangzhou geese

In this study, we evaluated the meat flavor compounds of Yangzhou geese, including one group of pedigree strain (AA group) and 4 groups of 2-strain crossbreds (KA, KB, CA, and SA). Each group consisted of 100 geese comprised of 5 replicates of 10 males and 10 females each. Inosine 5'-monophosphate (IMP), amino acid (AA), and fatty acid (FA) levels in breast and thigh muscle were determined. Results showed that AA group had the highest levels of total amino acid (TAA) and dissolved free amino acids (DFAA) in breast muscle and of polyunsaturated fatty acids (PUFA) in thigh muscle (P<0.05). In SA group, the levels of C17:1, C22:0, C22:1, C20:4, and C24:1 in breast muscle were significantly higher in SA than in other groups (P<0.05). KB group had the lowest glycine levels in breast muscle (P<0.05) while MUFA levels were significantly higher in KB than in other groups (P<0.05). In KA, the levels of C18:3 in breast muscle in were higher than in CA and KB (P<0.05). CA had relevant higher IMPc levels in breast muscle than SA (P<0.05) and other groups (P>0.05); however, no significant differences were obtained in thigh muscle (P>0.05). In conclusion, Yangzhou AA goose has high levels of meat flavor compounds than its crossbreeds. Future efforts should focus on assessing meat flavor through measurement of sensory characteristics of Yangzhou geese.

The food metabolome: a window over dietary exposure

The food metabolome is defined as the part of the human metabolome directly derived from the digestion and biotransformation of foods and their constituents. With >25,000 compounds known in various foods, the food metabolome is extremely complex, with a composition varying widely according to the diet. By its very nature it represents a considerable and still largely unexploited source of novel dietary biomarkers that could be used to measure dietary exposures with a high level of detail and precision. Most dietary biomarkers currently have been identified on the basis of our knowledge of food compositions by using hypothesis-driven approaches. However, the rapid development of metabolomics resulting from the development of highly sensitive modern analytic instruments, the availability of metabolite databases, and progress in (bio)informatics has made agnostic approaches more attractive as shown by the recent identification of novel biomarkers of intakes for fruit, vegetables, beverages, meats, or complex diets. Moreover, examples also show how the scrutiny of the food metabolome can lead to the discovery of bioactive molecules and dietary factors associated with diseases. However, researchers still face hurdles, which slow progress and need to be resolved to bring this emerging field of research to maturity. These limits were discussed during the First International Workshop on the Food Metabolome held in Glasgow. Key recommendations made during the workshop included more coordination of efforts; development of new databases, software tools, and chemical libraries for the food metabolome; and shared repositories of metabolomic data. Once achieved, major progress can be expected toward a better understanding of the complex interactions between diet and human health.

Fluoroacetylation/fluoroethylesterification as a derivatization approach for gas chromatography-mass spectrometry in metabolomics: preliminary study of lymphohyperplastic diseases

Metabolic fingerprinting in combination with gas chromatography and multivariate analysis is being extensively employed for the improved understanding of biological changes induced by endogenous or exogenous factors. Chemical derivatization increases the sensitivity and specificity of gas chromatography-mass spectrometry (GC-MS) for polar or thermally labile biological compounds, which bear derivatizable groups. Thus, there is a constant demand for simple methods of derivatization and separation that satisfy the need for metabolite analysis, identifying as many chemical classes of compounds as possible. In this study, an optimized protocol of extraction and derivatization is established as a generally applicable method for the analysis of a wide range of classes of metabolites in urine, whole blood and saliva. Compounds of biological relevance bearing hydroxyl- carboxyl- and amino-groups are derivatized using single-step fluoroacetylation/fluoroethylesterification after proper optimization of the protocol. Subsequently, the developed derivatization procedure is engaged in finding blood metabolic biomarkers, induced by lymphohyperplastic disease, through the metabolomic fingerprinting approach, the multivariate modeling (hierarchical cluster analysis) and GC-MS. Our preliminary, GC-MS-based metabolomic fingerprinting study underlines the contribution of certain metabolites to the discrimination of patients with lymphohyperplastic diseases.