Integrated metabolomics and lipidomics profiling reveals beneficial changes in sensory quality of brown fermented goat milk

Advances in High-Resolution Mass Spectrometry-Based Metabolomics: Applications in Food Analysis and Biomarker Discovery

Consumer concerns regarding food nutrition and quality are becoming increasingly prevalent. High-resolution mass spectrometry (HRMS)-based metabolomics stands as a cutting-edge and widely embraced technique in the realm of food component analysis and detection. It boasts the capability to identify character metabolites at exceedingly low abundances, which remain undetectable by conventional platforms. It can also enable real-time monitoring of the flux of targeted compounds in metabolic synthesis and decomposition. With the emergence of artificial intelligence and machine learning, it has become more convenient to process the vast data sets of metabolomics and identify biomarkers. The review summarizes the latest applications of HRMS-based metabolomics platforms in traditional foods, novel foods, and pharmaceutical-food homologous matrices. It compares the suitability of HRMS to nuclear magnetic resonance (NMR) in metabolomics across three dimensions and discusses the principles and application scenarios of various mass spectrometry technologies.

Comparative analysis of the fatty acid profiles in goat milk during different lactation periods and their interactions with volatile compounds and metabolites

This study aimed to compare the composition of fatty acids in goat milk during lactation with human milk, as well as analyze the differences in their interaction with odor and metabolites. Polyunsaturated fatty acids content was higher in human milk, while odd-chain, branched-chain, and monounsaturated fatty acids content were higher in goat milk with a decreasing trend during lactation. PUFAs in human milk undergo auto-oxidation to produce aldehydes (hexanal), giving it a mild aroma. Butyric acid in goat colostrum mediates the synthesis and auto-oxidation of PUFA, while taurine mediated the hydrolysis of amino acids. They produce a furanone compound (2(5H)-furanone) with a buttery flavor. The presence of butyric acid in goat transitional milk had an impact on flavor and metabolites. The medium chain fatty acid composition of the goat mature milk was affected by nucleic acid compounds, which then oxidized to produce methyl ketone (2-nonanone), giving it an unpleasant flavor.

Revealing the mechanism of flavor improvement of fermented goat milk based on lipid changes

The mechanism of goat milk (GM) flavor improvement based on lipid changes requires understanding. According to sensory evaluation results, the texture, taste, appearance, aroma, and overall acceptability score of Guishan fermented goat milk (GMF) were higher than those of GM. In total, 779 lipid molecules and 121 volatile compounds were formed from the metabolite-lipid level in the GM and GMF, as determined through lipidomics and gas chromatography-mass spectrometry. The key volatile flavor compounds in the GMF were (E,E)-2,4-decadienal, ethyl acetate, acetoin, 2,3-pentanedione, acetic acid, and 2,3-butanedione. Of them, 60 lipids significantly contributed to the flavor profiles of the GMF, based on the correlation analysis. The triacylglycerides (TAGs) 12:0_14:0_16:0 and 13:0_13:0_18:2 contributed to aroma retention, while TAG and phosphatidylethanolamine were identified as key substrates for flavor compound formation during fermentation. Lipids associated with glycerophospholipid and linoleic acid metabolism pathways significantly affected volatile compound formation in the GMF. This study provides an in-depth understanding of the lipids and flavors of the GMF, and this information will be useful for the development of specific GMF products.

Graduate Student Literature Review: Network of flavor compounds formation and influence factors in yogurt

Yogurt is popular as a natural and healthy food, but its flavor greatly affects acceptability by consumers. Flavor compounds of yogurt are generally produced by the metabolism of lactose, protein, and fat, and the resulting flavors include carbonyls, acids, esters, alcohols, and so on. Each flavor compound can individually provide the corresponding flavor, or it can be combined with other compounds to form a new flavor. The flavor network is formed among the metabolites of milk components, and acetaldehyde, as the central compound, plays a role in connecting the whole network. The flavor compounds can be affected by many factors, such as the use of different raw milks, ways of homogenization, sterilization, fermentation, postripening, storage condition, and packaging materials, which can affect the overall flavor of yogurt. This paper provides an overview of the volatile flavor compounds in yogurt, the pathways of production of the main flavor compounds during yogurt fermentation, and the factors that influence the flavor of yogurt, including type of raw milk, processing, and storage. It also aims to provide theoretical guidance for the product of yogurt in ideal flavor, but further research is needed to provide a more comprehensive description of the flavor system of yogurt.

Interference of endogenous benzoic acid with the signatures of sulfonic acid derivatives and carbohydrates in fermented dairy products

Endogenous benzoic acid causes detrimental effects on public health, but the underlying mechanisms often remain elusive. Benzoic acid (0.00-40.00 mg L -1) was detected from sixty fermented goat milk samples in six replicates, indicating the existence of endogenous benzoic acid. Herein, we investigated the effects of benzoic acid on the variations of metabolome and proteome signatures in fermented goat milk via integrative metabolomics (LOQ 2.39-98.98 μg L -1) and proteomics approach based on UHPLC-Q-Orbitrap HRMS. Explicitly, benzoic acid reduced the content of taurine (7.06-4.80 mg L -1) and hypotaurine (3.86-1.74 mg L -1) due to a significant decrease in the levels of glutamate decarboxylase 1 by benzoic acid. The reduction in lactose (7.13-5.31 mg L -1) and d-galactose (4.39-3.37 mg L -1) content was related to the decrease in α-lactalbumin and β-galactosidase levels, respectively, in fermented goat milk containing 40.00 mg L -1 benzoic acid. Meanwhile, the levels of maltose (22.84-16.53 mg L -1) and raffinose (4.19-3.10 mg L -1) progressively decreased with increasing benzoic acid concentrations (0.00-40.00 mg L -1), which had detrimental effects on the nutritional quality of fermented goat milk. Additionally, the concentration of benzoic acid and fermentation temperature are the most important factors to control the loss of nutrients in fermented dairy products.

High-confidence structural annotation of substances via multi-layer molecular network reveals the system-wide constituent alternations in milk interfered with diphenylolpropane

The spectral database-based mass spectrometry (MS) matching strategy is versatile for structural annotating in ingredient fluctuation profiling mediated by external interferences. However, the systematic variability of MS pool attributable to aliasing peaks and inadequacy of present spectral database resulted in a substantial metabolic feature depletion. An amended procedure termed multiple-charges overlap peaks extraction algorithm (MCOP) was proposed involving identifying collision-trigged dissociation precursor ions through iteratively matching mass features of fragmentations to expand the spectral reference library. We showcased the versatility and utility of established strategy in an investigation centered on the stimulation of milk mediated by diphenylolpropane (BPA). MCOP enabled efficient unknown annotations at metabolite-lipid-protein level, which elevated the accuracy of substance annotation to 85.3% after manual validation. Arginase and α-amylase (|r| > 0.75, p < 0.05) were first identified as the crucial issues via graph neural network-based virtual screening in the abnormal metabolism of urea triggered by BPA, resulting in the accumulation of arginine (original: 1.7 μg kg-1 1.7 times) and maltodextrin (original: 6.9 μg kg-1 2.9 times) and thus, exciting the potential dietary risks. Conclusively, MCOP demonstrated generalisation and scalability and substantially advanced the discovery of unknown metabolites for complex matrix samples, thus deciphering dark matter in multi-omics.

Exploring the oxidative rancidity mechanism and changes in volatile flavors of watermelon seed kernels based on lipidomics

Watermelon seed kernels (WSK) are prone to oxidative rancidity, while their evaluation biomarkers and changes in volatile flavor are still unknown. The research tracked the changes in volatile compounds and lipid components before and after rancidity using HS-SPME-GC-O-MS and lipidomic techniques. The results showed the flavor of watermelon seed kernels changed significantly before and after rancidity, from mild aroma to rancidity. A total of 42 volatile compounds were detected via GC-O-MS, and a total of 220 lipid molecules were detected via lipidomic technology. 55 lipids with significant differences were screened via multivariate statistical analysis. Combining the above analysis, it found that glycerol phospholipid and glyceride pathways were the most important metabolic pathways and 1-Pentanol and styrene could be used as potential biomarkers to judge the rancidity process of watermelon seed kernels. The research could provide powerful technical support for the storage, transportation and freshness preservation of watermelon seed kernels.

Stress adaptation in Tibetan cashmere goats is governed by inherent metabolic differences and manifested through variable cashmere phenotypes

Tibetan cashmere goats are not only served as a valuable model for studying adaptation to hypoxia and high-altitude conditions but also playing a pivotal role in bolstering local economies through the provision of premium quality cashmere yarn. In this study, we performed an integration and network analysis of metabolomic, transcriptomic and proteomic to elucidate the role of differentially expressed genes, important metabolites, and relevant cellular and metabolic pathways between the fine (average 12.04 ± 0.03 μm of mean fiber diameter) and coarse cashmere (average 14.88 ± 0.05 μm of mean fber diameter) producing by Tibetan cashmere goats. We identified a distinction of 56 and 71 differential metabolites (DMs) between the F and C cashmere groups under positive and negative ion modes, respectively. The KEGG pathway enrichment analysis of these DMs highlighted numerous pathways predominantly involved in amino acid and protein metabolism, as indicated by the finding that the most impactful pathway was the mammalian target of rapamycin (mTOR) signalling pathway. In the F group, we identified a distinctive metabolic profile where amino acid metabolites including serine, histidine, asparagine, glutamic acid, arginine, valine, aspartic acid, tyrosine, and methionine were upregulated, while lysine, isoleucine, glutamine, tryptophan, and threonine were downregulated. The regulatory network and gene co-expression network revealed crucial genes, metabolites, and metabolic pathways. The integrative omics analysis revealed a high enrichment of several pathways, notably encompassing protein digestion and absorption, sphingolipid signalling, and the synaptic vesicle cycle. Within the sphere of our integrative analysis, DNMT3B was identified as a paramount gene, intricately associated with significant proteins such as HMCN1, CPB2, GNG12, and LRP1. Our present study delineated the molecular underpinnings governing the variations in cashmere characteristics by conducting comprehensive analyses across metabolomic, transcriptomic, and proteomic dimensions. This research provided newly insights into the mechanisms regulating cashmere traits and facilitated the advancement of selective breeding programs aimed at cultivating high-quality superfine Tibetan cashmere goats.

Metabolic Evaluation of Lupin-Enriched Yogurt by Nuclear Magnetic Resonance Metabolomics

Untargeted nuclear magnetic resonance (NMR) metabolomics was used to evaluate compositional changes during yogurt fermentation upon lupin enrichment compared to traditional conditions. Lupin significantly changed the sample metabolic profile and its time course dynamics, seemingly delaying microbial action. The levels of organic and amino acids were significantly altered, along with those of some sugars, nucleotides, and choline compounds. Lupin seemed to favor acetate and formate synthesis, compared to that of citrate and fumarate; a higher formate levels may suggest increased levels of Streptococcus thermophilus action, compared toLactobacillus bulgaricus. Lupin-yogurt was poorer in hippurate, lactose (and hence lactate), galactose, glucose-1-phosphate, and galactose-1-phosphate, containing higher orotate levels (possibly related to increased uridine derivatives), among other differences. Trigonelline was confirmed as a lupin marker, possibly together with glutamate and histidine. Other metabolite trajectories remained unchanged upon lupin addition, unveiling unaffected underlying processes. These results demonstrate the usefulness of untargeted NMR metabolomics to understand/develop new foodstuffs and their production processes, highlighting the identity of a variety of bioactive metabolites with importance for human health.

An overview of food lipids toward food lipidomics

Increasing evidence regarding lipids' beneficial effects on human health has changed the common perception of consumers and dietary officials about the role(s) of food lipids in a healthy diet. However, lipids are a wide group of molecules with specific nutritional and bioactive properties. To understand their true nutritional and functional value, robust methods are needed for accurate identification and quantification. Specific analytical strategies are crucial to target specific classes, especially the ones present in trace amounts. Finding a unique and comprehensive methodology to cover the full lipidome of each foodstuff is still a challenge. This review presents an overview of the lipids nutritionally relevant in foods and new trends in food lipid analysis for each type/class of lipids. Food lipid classes are described following the LipidMaps classification, fatty acids, endocannabinoids, waxes, C8 compounds, glycerophospholipids, glycerolipids (i.e., glycolipids, betaine lipids, and triglycerides), sphingolipids, sterols, sercosterols (vitamin D), isoprenoids (i.e., carotenoids and retinoids (vitamin A)), quinones (i.e., coenzyme Q, vitamin K, and vitamin E), terpenes, oxidized lipids, and oxylipin are highlighted. The uniqueness of each food group: oil-, protein-, and starch-rich, as well as marine foods, fruits, and vegetables (water-rich) regarding its lipid composition, is included. The effect of cooking, food processing, and storage, in addition to the importance of lipidomics in food quality and authenticity, are also discussed. A critical review of challenges and future trends of the analytical approaches and computational methods in global food lipidomics as the basis to increase consumer awareness of the significant role of lipids in food quality and food security worldwide is presented.

Magnetic field-driven biochemical landscape of browning abatement in goat milk using spatial-omics uncovers

Influence of magnetic field (MF) treatment on the glycation of goat milk proteins is yet to be elucidated. Proteomic and metabolomic analyses of brown goat milk samples with and without MF treatment were performed. Assessed glycation degree and structural modification of proteins explained that MF treatment dramatically down-regulated the glycation of brown goat milk protein, possibly due to the aggregation behavior induced by MF treatment, which consumed additional glycation sites as well as altered their accessibility and preference. Integrated datasets uncovered that the energy metabolism-related biological events including carbohydrate metabolism, glycerophospholipid metabolism, TCA cycle may mainly account for the browning abatement mechanism of MF. In addition, MF treatment enhanced both the quality and flavor of brown goat milk. This study suggests the feasibility of MF treatment to reduce glycation in brown goat milk for producing high-quality dairy ingredients and products.

Characterization of a fermented dairy, sour cream: Lipolysis and the release profile of flavor compounds

Lipolysis and flavor development during fermentation of sour cream were studied by evaluating the physicochemical changes, sensory differences and volatile components. The fermentation caused significant changes in pH, viable count and sensory evaluation. The peroxide value (POV) decreased after reaching the maximum value of 1.07 meq/kg at 15 h, while thiobarbituric acid reactive substances (TBARS) increased continuously with the accumulation of secondary oxidation products. The Free fatty acids (FFAs) in sour cream were mainly myristic, palmitic and stearic. GC-IMS was used to identify the flavor properties. A total of 31 volatile compounds were identified, among which the contents of characteristic aromatic substances such as ethyl acetate, 1-octen-3-one and hexanoic acid were increased. The results suggest that lipid changes and flavor formation in sour cream are influenced by fermentation time. Furthermore, flavor compounds may be related to lipolysis such as 1-octen-3-one and 2- heptanol were also observed.

Non-gene-editing microbiome engineering of spontaneous food fermentation microbiota-Limitation control, design control, and integration

Non-gene-editing microbiome engineering (NgeME) is the rational design and control of natural microbial consortia to perform desired functions. Traditional NgeME approaches use selected environmental variables to force natural microbial consortia to perform the desired functions. Spontaneous food fermentation, the oldest kind of traditional NgeME, transforms foods into various fermented products using natural microbial networks. In traditional NgeME, spontaneous food fermentation microbiotas (SFFMs) are typically formed and controlled manually by the establishment of limiting factors in small batches with little mechanization. However, limitation control generally leads to trade-offs between efficiency and the quality of fermentation. Modern NgeME approaches based on synthetic microbial ecology have been developed using designed microbial communities to explore assembly mechanisms and target functional enhancement of SFFMs. This has greatly improved our understanding of microbiota control, but such approaches still have shortcomings compared to traditional NgeME. Here, we comprehensively describe research on mechanisms and control strategies for SFFMs based on traditional and modern NgeME. We discuss the ecological and engineering principles of the two approaches to enhance the understanding of how best to control SFFM. We also review recent applied and theoretical research on modern NgeME and propose an integrated in vitro synthetic microbiota model to bridge gaps between limitation control and design control for SFFM.

Integration of lipidomics and metabolomics approaches for the discrimination of harvest time of green tea in spring season by using UPLC-Triple-TOF/MS coupled with chemometrics

The production season is one of the judgment standards of the green tea quality and spring tea is generally considered of higher quality. Moreover, early spring tea is usually more precious and sells for a higher price. Therefore, a multifaceted strategy that integrates lipidomics and metabolomics, based on UPLC-Triple-TOF/MS coupled with chemometrics, was developed to discriminate early spring green tea (ET) and late spring green tea (LT). Twenty-six lipids and forty-five metabolites were identified as characteristic components. As for characteristic lipids, most of glycerophospholipids and acylglycerolipids have higher contents in ET. By contrast, glycoglycerolipids, sphingolipids and hydroxypheophytin a were shown higher levels in LT samples. Most of the differential metabolites identified were more abundant in ET samples. LT samples have much higher catechin, procyanidin B2, and 3',8-dimethoxyapigenin 7-glucoside contents. Based on the integration of differential lipids and metabolites, the reconstructed orthogonal partial least squares discriminant analysis (OPLS-DA) model displayed 100% correct classification rates for harvest time discrimination of green tea samples. These results demonstrated that the integration of lipidomics and metabolomics approaches is a promising method for the discrimination of tea quality.

Comprehensive Evaluation of Quality Characteristics of Four Oil-Tea Camellia Species with Red Flowers and Large Fruit

Red-flowered oil-tea camellia (ROC) is an important woody oil species growing in the south, and its oil has high nutritional value. There are four main species of ROC in China, namely, Camellia chekiangoleosa (CCH), Camellia polyodonta (CPO), Camellia semiserrata (CSE) and Camellia reticulata (CRE). Reports on the comprehensive comparative analysis of ROC are limited. This study investigated the fruit characteristics and nutritional components of four ROC fruits, and the results showed that ROC had high oil content with levels of 39.13%-58.84%, especially the CCH fruit, which reached 53.6-58.84%. The contents of lipid concomitants of ROC oil were also substantial, including β-amyrin (0.87 mg/g-1.41 mg/g), squalene (0.43 mg/g-0.69 mg/g), β-sitosterin (0.47 mg/g-0.63 mg/g) and α-tocopherol (177.52 μg/g-352.27 μg/g). Moreover, the transverse diameter(TD)/longitudinal diameter (LD) of fruits showed a significant positive correlation with the oil content, and ROC fruits with thinner peels seemed to have better oil quality, which is similar to the result of the oil quality evaluation obtained by the gray correlation coefficient evaluation method. Four ROC oils were evaluated using the gray correlation coefficient method based on 11 indicators related to the nutritional value of ROC. CCH oil had the highest score of 0.8365, and YS-2 (a clone of CCH) was further evaluated as the best CCH oil. Finally, the results of heatmap analysis showed that triglycerides could be used as a characteristic substance to distinguish CCH oil from the other three ROC oils. The PLSDA (Partial least squares regression analysis) model and VIP (Variable important in projection) values further showed that P/S/O, P/O/O, P/L/L, P/L/Ln, S/S/O, S/O/O and P/S/S (these all represent abbreviations for fatty acids) could be used as characteristic differential triglycerides among the four ROC oils. This study provides a convenient way for planters to assess the nutritional quality of seed oil depending on fruit morphology and a potential way to distinguish between various ROC oils.

A point of view on human fat olfaction - do fatty derivatives serve as cues for awareness of dietary fats?

Fat (triglycerides) consumption is critical for the survival of animals, including humans. Being able to smell fat can be advantageous in judging food value. However, fat has poor volatility; thus, olfaction of fat seems impossible. What about fatty acids that comprise fat? Humans smell and discriminate medium-chain fatty acids. However, no conclusive evidence has been provided for the olfactory sense of long-chain fatty acids, including essential acids such as linoleic acid (LA). Instead, humans likely perceive the presence of essential fatty acids through the olfaction of volatile compounds generated by their oxidative breakdown (e.g., hexanal and γ-decalactone). For some people, such scents are pleasing, especially when they come from fruit. Nonetheless, it remains unclear whether the olfaction of these volatiles leads to the recognition of fat per se. Nowadays, people often smell LA-borne aldehydes such as E,E-2,4-decadienal that occur appreciably, for example, from edible oils during deep frying, and are pronely captivated by their characteristic "fatty" note, which can be considered a "pseudo-perception" of fat. However, our preference for such LA-borne aldehyde odors may be a potential cause behind the modern overdose of n-6 fatty acids. This review aims to provide a view of whether and, if any, how we olfactorily perceive dietary fats and raises future purposes related to human fat olfaction, such as investigating sub-olfactory systems for detecting long-chain fatty acids.

Novel insight into the transformation of peptides and potential benefits in brown fermented goat milk by mesoporous magnetic dispersive solid phase extraction-based peptidomics

Brown fermented goat milk as an excellent source of bioactive peptides has only been partially elucidated. Meticulously synthesized MOF@MG as magnetic sorbent for enriching endogenous peptides owned higher reproducibility and uniform distribution of peptides PI compared with ultrafiltration. Combined with UHPLC-Q-Orbitrap, fermentation for 12 h in brown goat milk with the highest overall acceptable degree through sensory evaluation was utilized to explore the transformation of peptides and health benefits, with trypsin or plasmin hydrolyzing proteins and aminopeptidase or carboxypeptidase hydrolyzing peptides to small peptides or amino acids. A total of 1317 peptides were identified by database matching (1259) and de novo sequencing (58), among 18 peptides could originate from gene-independent enzymatic formation and top 25 characteristic peptides were quantified with concentration ranging from 0.12 to 6.40 mg L^-1. Bioinformatic analysis results indicated that brown fermented goat milk possesses higher health benefits because of more than 50 peptides with potential bioactivity.

SWATH-MS2&1: Development and Validation of a Pseudotargeted Lipidomics Method for the Analysis of Glycerol Esters in Milk

Glycerol ester (GE) is a kind of important lipid in milk, which varies greatly depending on many factors. In this study, a novel pseudotargeted lipidomics strategy, named SWATH-MS2&1, was developed for the detection of GEs in milk and the Folch method was selected for the sample preparation. The developed method exhibited a competitive alternative to the acknowledged pseudotargeted strategy, including wider coverage (12 more GEs detected), higher repeatability (12 more GEs, whose coefficient of variation < 0.3), better linearity (5 more GEs, whose R² > 0.8), and similar sensitivity (only 2 GEs less than P-MRM after dilution). SWATH-MS2&1 was applied in the investigation of GEs from different milk samples. The orthogonal partial least-squares difference analysis of 219 GEs identified from SWATH-MS2&1 showed satisfying differentiation of different milk samples, and 76 GEs were screened out as potential markers. Our findings demonstrated that SWATH-MS2&1 could offer an accurate method to measure a wide spectrum of GEs in milk.

Impact of lactic acid bacteria and their metabolites on the techno-functional properties and health benefits of fermented dairy products

After conversion of lactose to lactic acid, several biochemical changes occur such as enhanced protein digestibility, fatty acids release, and production of bioactive compounds etc. during the fermentation process that brings nutritional and quality improvement in the fermented dairy products (FDP). A diverse range of lactic acid bacteria (LAB) is being utilized for the development of FDP with specific desirable techno-functional attributes. This review contributes to the knowledge of basic pathways and changes during fermentation process and the current research on techniques used for identification and quantification of metabolites. The focus of this article is mainly on the metabolites responsible for maintaining the desired attributes and health benefits of FDP as well as their characterization from raw milk. LAB genera including Lactobacillus, Streptococcus, Leuconostoc, Pediococcus and Lactococcus are involved in the fermentation of milk and milk products. LAB species accrue these benefits and desirable properties of FDP producing the bioactive compounds and metabolites using homo-fermentative and heterofermentative pathways. Generation of metabolites vary with incubation and other processing conditions and are analyzed and quantified using highly advanced and sophisticated instrumentation including nuclear magnetic resonance, mass-spectrometry based techniques. Health benefits of FDP are mainly possible due to the biological roles of such metabolites that also cause technological improvements desired by dairy manufacturers and consumers.