Effects of Roughage on the Lipid and Volatile-Organic-Compound Profiles of Donkey Milk

The lipid molecules and volatile organic compounds (VOCs) in milk are heavily influenced by diet. However, little is known about how roughage affects the lipid and VOC contents of donkey milk. Accordingly, in the present study, donkeys were fed corn straw (G1 group), wheat hulls (G2 group), or wheat straw (G3 group), and the lipid and VOC profiles of their milk were determined using LC-MS and GC-MS. Of the 1842 lipids identified in donkey milk, 153 were found to be differential, including glycerolipids, glycerophospholipids, and sphingolipids. The G1 group showed a greater variety and content of triacyclglycerol species than the G2 and G3 groups. Of 45 VOCs, 31 were identified as differential, including nitrogen compounds, esters, and alcohols. These VOCs were significantly increased in the G2 and G3 groups, with the greatest difference being between the G1 and G2 groups. Thus, our study demonstrates that dietary roughage changes the lipid and VOC profiles of donkey milk.

Progress of Mass Spectrometry-Based Lipidomics in the Dairy Field

Lipids play important biological roles, such as providing essential fatty acids and signaling. The wide variety and structural diversity of lipids, and the limited technical means to study them, have seriously hampered the resolution of the mechanisms of action of lipids. With advances in mass spectrometry (MS) and bioinformatic technologies, large amounts of lipids have been detected and analyzed quickly using MS-based lipidomic techniques. Milk lipids, as complex structural metabolites, play a crucial role in human health. In this review, the lipidomic techniques and their applications to dairy products, including compositional analysis, quality identification, authenticity identification, and origin identification, are discussed, with the aim of providing technical support for the development of dairy products.

Linseed oil supplementation and DGAT1 K232A polymorphism affect the triacylglycerol composition and crystallization of milk fat

We studied the effect of dietary linseed oil (LSO) supplementation and DGAT1 K232A (DGAT1) polymorphism on the triacylglycerol composition and crystallization of bovine milk fat. LSO supplementation increased unsaturated triacylglycerols, notably in the C52-C54 carbon range, while reducing the saturated C29-C49 triacylglycerols. These changes were associated with an increase in the low-melting fraction and the crystal lamellar thickness, as well as a reduction in the medium and high-melting fractions and the formation of the most abundant crystal type at 20 °C (β'-2 polymorph). Furthermore, DGAT1 KK was associated with higher levels of odd-chain saturated triacylglycerols than DGAT1 AA, and it was also associated with an increase in the high-melting fraction and the endset melting temperature. An interaction between diet and DGAT1 for the unsaturated C54 triacylglycerols accentuated the effects of LSO supplementation with DGAT1 AA. These findings show that genetic polymorphism and cows' diet can have considerable effects on milk fat properties.

A Comparative Study of Milk Fat Extracted from the Milk of Different Goat Breeds in China: Fatty Acids, Triacylglycerols and Thermal and Spectroscopic Characterization

Goat milk (GM) is an excellent alternative to cow milk and has recently been used in commercial infant formula preparation due to its superior fat composition. Here, the fatty acid (FA) composition, triacylglycerol (TAG) molecular species, thermal behavior and infrared spectra of extracted milk fat from the milk of the two main breeds of dairy goat bred in China (Guanzhong GM (GZG) and Xinong Saanen GM (XSG)) are investigated. Gas chromatography, Fourier-transform infrared spectroscopy, differential scanning calorimetry and ultra-performance convergence chromatography with quadrupole time-of-flight mass spectrometry are applied. The obtained results evidence significant fat compositional differences based on the breed that produced the considered GM. The major FAs in both GM fats were capric (C10:0), myristic (C14:0), palmitic (C16:0), stearic (C18:0) and oleic (C18:1 n-9c). GZG presented a higher content of medium-chain saturated FAs, while XSG had higher unsaturated FAs with higher ratios of L/Ln and n-6/n-3. A total of 339 and 359 TAGs were detected and quantified in GZG and XSG, and the major TAGs were those of m/z 740.6712 (14.10 ± 0.27%) and m/z 684.6094 (10.94 ± 0.02%), respectively. Milk TAGs of GZG and XSG showed 24–54 and 26–54 total acyl carbon numbers with a 0–4 and 0–5 double bond number at 68 and 72 various retention times, respectively. Thermal analysis showed that all GM fat samples melted below normal body temperature. Infrared spectra revealed higher absorption values of GZG milk fat. This study provides valuable information to the dairy industry sector about GM fat produced in China, assessing the appropriateness of Chinese GM fat to be applied in Chinese infant formula.

Synthesis and Investigation of Novel CHCA-Derived Matrices for Matrix-Assisted Laser Desorption/Ionization Mass Spectrometric Analysis of Lipids

A significant area of study and upgrading for increasing sensitivity and general performances of matrix-assisted laser-desorption ionization (MALDI) mass spectrometry (MS) is related to matrix design. Several efforts have been made to address the challenge of low-mass-region interference-free for metabolomics analysis and specifically for lipidomics. To this aim, rationally designed matrices as 4-chloro-α-cyanocinnamic acid (ClCCA) were introduced and reported to provide enhanced analytical performances. We have taken this rational design one step further by developing and optimizing new MALDI matrices with a range of modifications on the CHCA core, involving different functionalities and substituents. Of particular interest was the understanding of the electron-withdrawing (e.g., nitro-) or donating (e.g., methoxy-) effects along with the extent of conjugation on the ionization efficiency. In the present work, ten matrices were designed on a reasonable basis, synthesized, and characterized by NMR and UV spectroscopies and laser desorption ionization. With the assistance of these putative MALDI matrices, samples containing phospholipids (PL), and neutral di-/tri-acylglycerols (DAG, TAG) were investigated using milk, fish, blood, and human plasma extracts. In comparison with CHCA and ClCCA, four of them, viz. [(2E,4E)-2-cyano-5-(4-methoxyphenyl)penta-2,4-dienoic acid] (1), [(2E,4E)-2-cyano-5-(4-nitrophenyl)penta-2,4-dienoic acid] (2), [(E)-2-cyano-3-(6-methoxynaphthalen-2-yl)acrylic acid] (6) and [(E)-2-cyano-3-(naphthalen-2-yl)acrylic acid] (7) displayed good to even excellent performances as MALDI matrices in terms of ionization capability, interference-free spectra, S/N ratio, and reproducibility. Especially compound 7 (cyano naphthyl acrylic acid, CNAA) was the election matrix for PL analysis and matrix 2 (cyano nitrophenyl dienoic acid, CNDA) for neutral lipids such as DAG and TAG in positive ion mode.

A new update of MALDI-TOF mass spectrometry in lipid research

Matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS) is an indispensable tool in modern lipid research since it is fast, sensitive, tolerates sample impurities and provides spectra without major analyte fragmentation. We will discuss some methodological aspects, the related ion-forming processes and the MALDI MS characteristics of the different lipid classes (with the focus on glycerophospholipids) and the progress, which was achieved during the last ten years. Particular attention will be given to quantitative aspects of MALDI MS since this is widely considered as the most serious drawback of the method. Although the detailed role of the matrix is not yet completely understood, it will be explicitly shown that the careful choice of the matrix is crucial (besides the careful evaluation of the positive and negative ion mass spectra) in order to be able to detect all lipid classes of interest. Two developments will be highlighted: spatially resolved Imaging MS is nowadays well established and the distribution of lipids in tissues merits increasing interest because lipids are readily detectable and represent ubiquitous compounds. It will also be shown that a combination of MALDI MS with thin-layer chromatography (TLC) enables a fast spatially resolved screening of an entire TLC plate which makes the method competitive with LC/MS.

Seasonal variation in fatty acid and triacylglycerol composition of bovine milk fat

The aim of this study was to assess the effects of seasonal variation on the changes of the fatty acid (FA) and triacylglycerol (TAG) composition of bovine milk fat (MF) in a nonseasonal milking system. Weekly milk samples were collected from 14 dairy factories and pooled per week as representative samples of the average Dutch bovine milk. The sample collection started in May 2017 and finished in April 2018, resulting in a total of 52 samples, corresponding to each week of the year. The samples were analyzed for MF content (%) and FA and TAG composition using gas chromatography with flame-ionization detection. The increased intake of C18:3 cis-9,12,15 through grass feeding in spring and summer was associated with major changes in MF FA composition, including reduced proportions of de novo synthesized FA and presence of several rumen biohydrogenation products and conjugated linoleic acid isomers in MF. These changes in seasonal FA composition had an effect on TAG seasonal variation. The TAG seasonal variation showed that all TAG groups were significantly different between months. The low molecular weight and the medium molecular weight TAG groups increased in winter and decreased in summer, whereas the high molecular weight TAG groups increased in summer and decreased in winter. Based on pooled monthly samples, MALDI-TOF-mass spectrometry allowed the analysis of even- and odd-chain TAG species in MF based on their total carbon number and number of double bonds. These analyses indicated saturated TAG species to be greatest in winter, whereas monounsaturated, polyunsaturated, and odd-chain TAG species were greatest in summer. Our study showed that TAG seasonal variation in a nonseasonal milking system is influenced by the variation in FA composition throughout the seasons.

Short-term effects of dietary bovine milk on fatty acid composition of human milk: A preliminary multi-analytical study

The fatty acid (FA) composition of human milk (HM) from N = 9 Italian healthy donors following a free diet exhibited FA-dependent ranges of variability, as assessed by GC-FID. The possible short-term changes in the FA profile were monitored in the milk of lactating mothers (three) collected at five time points over a 6 h period, following an oral load (200 mL) of bovine milk. An array of techniques was exploited, including UHPLC-ESI-MS/MS of intact lipids and MALDI-TOF MS before and after chemical hydrogenation or bromination, in addition to MALDI-TOF MS analysis of FA after saponification, to monitor short-chain and odd-chain FA in HM as markers of bovine milk fat. A single administration of bovine milk did not appreciably modify the lipid pattern, suggesting that the maternal diet could induce not detectable short-term changes on the lipid composition of HM. Diet-induced increase of butyric acid was also excluded by ¹³C NMR. The functions that HM FA exert in infant physiology appear finely regulated through maternal metabolism.

Characterisation of triacylglycerols from bovine milk fat fractions with MALDI-TOF-MS fragmentation

In this study, we used MALDI-TOF-MS to profile and characterise the triacylglycerol (TAG) species of anhydrous bovine milk fat (AMF) and its low melting (olein) and high melting (stearin) fractions obtained by dry fractionation. Silver-ion solid phase extraction (Ag⁺-SPE) cartridges were utilised to separate the TAGs according to saturation degree. Then, several TAG species were selected and fragmented via post-source decay (PSD) fragmentation. MALDI-TOF-MS TAG profiles and fragmentation patterns were compared to the TAG and fatty acid (FA) compositions obtained by gas chromatography-flame ionization detector (GC-FID). We found that, olein was rich in medium length chain TAG species like CN38:0 and CN40:1, whereas stearin was rich in saturated long chain TAG species from CN42:0 to CN52:0. Separation of the TAGs based on saturation degree allowed successful selection of the TAG parent-ion for fragmentation by eliminating the interferences of TAG species that have the same carbon number but vary in number of double bonds. The TAG fragmentation patterns indicated significant differences between AMF, olein and stearin as a result of the dry fractionation process. Compared to AMF, olein yielded in higher fragments of short-chain saturated and middle-chain unsaturated FAs. Whereas, stearin yielded in saturated and monounsaturated long chain FA fragments. Fragmentation of unsaturated long chain TAGs showed that the TAGs in olein contained more C18:1 and C18:2 than that of AMF and stearin. Stearin on the other hand, contained higher amount of TAG species containing C16:0. These results were in line with the FA compositions obtained from GC-FID and suggest that Ag⁺-SPE cartridges coupled with MALDI-TOF-MS offer an informative and practical approach to characterise fats and oils with complex TAG composition.

Determination of Milk Products in Ceramic Vessels of Corded Ware Culture from a Late Eneolithic Burial

In this study, a soil from two ceramic vessels belonging to Corded Ware culture, 2707–2571 B.C., found in a cremation grave discovered in Central Moravia, Czech Republic, was analyzed using matrix-assisted laser desorption/ionization–mass spectrometry (MALDI–MS) combined with advanced statistical treatment (principal component analysis, PCA, and orthogonal projection to latent structures discriminant analysis, OPLS-DA) and by enzyme-linked immunosorbent assay (ELISA). MALDI–MS revealed the presence of triacylglycerols in both vessels. This analytical technique was used for the analysis of the soil content from archaeological ceramic vessels for the first time. Targeted ELISA experiments consequently proved the presence of milk proteins in both ceramic vessels. These results represent the first direct evidence of the use of milk or dairy products in the Eneolithic period in Moravian Corded Ware Culture and help to better understand the diet habits and living conditions of Eneolithic populations in Central Europe.

Establishment of a spectral database for classification of edible oils using matrix-assisted laser desorption/ionization mass spectrometry

In this study, we aim to establish a comprehensive spectral database for analysis of edible oils using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). More than 900 edible oil samples, including 30 types of edible oils, were analyzed and compared, and the characteristic peaks and spectral features of each edible oil were obtained. Edible oils were divided into eight groups based on their characteristic spectral patterns and principal component analysis results. An overall correct rate of 97.2% (98.1% for testing set) was obtained for classification of 435 edible oil products using partial least square-discriminant analysis, with nearly 100% correct rate for commonly used edible oils. Differentiation of counterfeit edible oils, repeatedly cooked edible oils and gutter oils from normal edible oils could also be achieved based on the MALDI-MS spectra. The establishment of this spectral database provides reference spectra for spectral comparison and allows rapid classification of edible oils by MALDI-MS.

MALDI-FT-ICR-MS for archaeological lipid residue analysis

Soft-ionization methods are currently at the forefront of developing novel methods for analysing degraded archaeological organic residues. Here, we present little-used soft ionization method of matrix assisted laser desorption/ionization-Fourier transform-ion cyclotron resonance-mass spectrometry (MALDI-FT-ICR-MS) for the identification of archaeological lipid residues. It is a high-resolution and sensitive method with low limits of detection capable of identifying lipid compounds in small concentrations, thus providing a highly potential new technique for the analysis of degraded lipid components. A thorough methodology development for analysing cooked and degraded food remains from ceramic vessels was carried out, and the most efficient sample preparation protocol is described. The identified components, also controlled by independent parallel analysis by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-combustion-isotope ratio mass spectrometry (GC-C-IRMS), demonstrate its capability of identifying very different food residues including dairy, adipose fats as well as lipids of aquatic origin. The results obtained from experimentally cooked and original archaeological samples prove the suitability of MALDI-FT-ICR-MS for analysing archaeological organic residues. Sample preparation protocol and identification of compounds provide future reference for analysing various aged and degraded lipid residues in different organic and mineral matrices.

A study of enhanced ion formation from metal-semiconductor complexes in atmospheric pressure laser desorption/ionization mass spectrometry

The study of the key parameters impacted surface-assisted laser desorption/ionization-mass spectrometry is of broad interest. In previous studies, it has been shown that surface-assisted laser desorption/ionization-mass spectrometry is a complex process depending on multiple factors. In the presented study, we showed that neither porosity, light absorbance nor surface hydrophobicity alone influence the enhancement phenomena observed from the hybrid metal-semiconductor complexes versus individual targets, but small changes in the analyte attaching to the target significantly affect laser desorption ionization-efficiency. By means of Raman spectroscopy and scanning electron microscopy, it was revealed that the formation of an amorphous analyte layer after drying on a solid substrate was essential for the enhanced laser desorption ionization-signal observed from the hybrid metal-semiconductor targets, and the crystallization properties of the analyte appeared as a function of the substrate. Obtained results were used for the screening of regular and lactose-free milk samples through the hybrid metal-semiconductor target. Copyright © 2016 John Wiley & Sons, Ltd.

Formation of β Polymorphs in Milk Fats with Large Differences in Triacylglycerol Profiles

In this study, we characterized the polymorphism of milk fat (MF) with various TAG compositions during isothermal crystallization at 20 °C. TAG composition of MF from seven individual cows was determined using GC-FID and MALDI-TOF MS, and MF polymorphism was studied using X-ray diffraction. Results showed that TAG profile determines the polymorphic behavior of MF. Saturated TAG with carbon numbers 34-38 promoted the formation of α polymorphs, whereas unsaturated TAG with 52-54 promoted the formation of the β polymorphs. Furthermore, MFs with unsaturated fatty acid profiles were increased in unsaturated TAG with 52-54 carbons. The presence of MF crystals in the β polymorph has been controversial over the years as most authors mainly find MF crystals in the α and β' form. In our work, we showed that the β polymorph is formed in MF on the basis of its TAG composition.

Ultrahigh resolution mass spectrometry and accurate mass measurements for high-throughput food lipids profiling

In the present study, accurate mass measurements by ultrahigh resolution mass spectrometry with Orbitrap-Exactive working at resolving power R: 100,000 (m/z 200, full width at half maximum) with an accuracy better than 2 ppm in all the mass range (m/z 200 to 2000) were used to show a detailed molecular composition of diverse edible oils and fats. Flow injection was used to introduce samples into the mass spectrometer, obtaining a complete analysis of each sample in less than 10 min, including blanks. Meticulous choice of organic solvents and optimization of the ion source and Orbitrap mass analyzer parameters were carried out, in order to achieve reproducible mass spectra giving reliable elemental compositions of the lipid samples and to prevent carry over. More than 200 elemental compositions attributable to diacylglycerols, triacylglycerols (TAGs), and their oxidation products have been found in the spectra of food lipids from different origin. Several compounds with very close molecular mass could only be resolved through ultrahigh resolution, allowing detailed and robust TAG profiling with a high characterization potential.

Distinct hepatic lipid profile of hypertriglyceridemic mice determined by easy ambient sonic-spray ionization mass spectrometry

Easy ambient sonic-spray ionization mass spectrometry (EASI-MS) was used to interrogate the hepatic lipid profiles of hypertriglyceridemic and control normotriglyceridemic mice. The analyses of ex vivo complex lipid mixtures were made directly with EASI-MS without accompanying separation steps. Intense ions for phosphatidylcholines and triacylglycerols were observed in the positive ion mode whereas the spectra in the negative ion mode provided profiles of phosphatidylethanolamines and phosphatidylinositol. EASI-MS was coupled to high-performance thin-layer chromatography for analysis of free fatty acids. Fourier transform-ion cyclotron resonance-mass spectrometry was also employed to confirm the identity of the detected lipids. We demonstrated higher incorporation of oleic acid in phosphatidylcholine and triacylglycerol composition, higher relative abundance of arachidonic acid containing phosphatidylinositol, and overall distinct free fatty acid profile in the livers of genetic hypertriglyceridemic mice. We propose that these alterations in liver lipid composition are related to the higher tissue and body metabolic rates described in these hypertriglyceridemic mice.

Authentication of animal fats using direct analysis in real time (DART) ionization-mass spectrometry and chemometric tools

A combination of direct analysis in real time (DART) ionization coupled to time-of-flight mass spectrometry (TOFMS) and chemometrics was used for animal fat (lard and beef tallow) authentication. This novel instrumentation was employed for rapid profiling of triacylglycerols (TAGs) and polar compounds present in fat samples and their mixtures. Additionally, fat isolated from pork, beef, and pork/beef admixtures was analyzed. Mass spectral records were processed by principal component analysis (PCA) and stepwise linear discriminant analysis (LDA). DART-TOFMS profiles of TAGs were found to be more suitable for the purpose of discrimination among the examined fat types as compared to profiles of polar compounds. The LDA model developed using TAG data enabled not only reliable classification of samples representing neat fats but also detection of admixed lard and tallow at adulteration levels of 5 and 10% (w/w), respectively. The presented approach was also successfully applied to minced meat prepared from pork and beef with comparable fat content. Using the DART-TOFMS TAG profiles of fat isolated from meat mixtures, detection of 10% pork added to beef and vice versa was possible.

Analytical strategies for discriminating archeological fatty substances from animal origin

Mass spectrometry (MS) is an essential tool in the field of biomolecular archeology to characterize amorphous organic residues preserved in ancient ceramic vessels. Animal fats of various nature and origin, namely subcutaneous fats of cattle, sheep, goats, pigs, horses, and also of dairy products, are those most commonly identified in organic residues in archeological pottery. Fats and oils of marine origin have also been revealed. Since the first applications of MS coupled with gas chromatography (GC) in archeology at the end of 1980s, several developments have occurred, including isotopic determinations by GC coupled to isotope ratio MS and identification of triacylglycerols (TAGs) structure by soft ionization techniques (ESI and APCI). The combination of these methods provides invaluable insights into the strategies of exploitation of animal products in prehistory. In this review, I focus on the analytical strategies based upon MS that allow elucidation of the structure of biomolecular constituents and determination of their isotopic values to identify the nature of animal fat components preserved in highly complex and degraded archeological matrices.

Biochemical traits of Ciauscolo, a spreadable typical Italian dry-cured sausage

Ciauscolo is a short-ripened fermented sausage manufactured in the Marche region (central Italy) that has recently received a protected geographical indication product classification (PGI). The aim of this study was the exploration of the biochemical traits of this traditional Italian salami, with a special focus on protein and lipid composition. Ciauscolo salami was characterized by pH of 5.1 and 0.91 water activity. A prevalence of lactic acid bacteria in the microbiota was found. The free amino acids and biogenic amines average content was 2657 and 255 mg/kg, respectively. With regards to lipids composition unsaturated fatty acids represented 63% and 72% of total and free fatty acids. Despite these results had wide statistical variability, attributable to differences in the processing parameters and raw matter used, some peculiar traits were found: (1) structural muscular proteins underwent to less proteolysis than sarcoplasmic ones; (2) glycogen phosphorylase, enolase, and aldolase were the most proteolyzed among the sacoplasmic proteins; (3) there was inverse correlation between histamine content and yeasts population, and a direct correlation between the gly-pro content and lactic acid bacteria counts; (4) the content of aspartic acid and methyonine seem to be a possible molecular marker able to distinguish between double and single milling.

An update of MALDI-TOF mass spectrometry in lipid research

Although matrix-assisted laser desorption and ionization (MALDI) mass spectrometry (MS)--often but not exclusively coupled with a time-of-flight (TOF) mass analyzer--is primarily established in the protein field, there is increasing evidence that MALDI MS is also very useful in lipid research: MALDI MS is fast, sensitive, tolerates sample impurities to a relatively high extent and provides very simple mass spectra without major fragmentation of the analyte. Additionally, MALDI MS devices originally purchased for "proteomics" can be used also for lipids without the need of major system alterations. After a short introduction into the method and the related ion-forming process, the MALDI mass spectrometric characteristics of the individual lipid (ranging from completely apolar hydrocarbons to complex glycolipids with the focus on glycerophospholipids) classes will be discussed and the progress achieved in the last years emphasized. Special attention will be paid to quantitative aspects of MALDI MS because this is normally considered to be the "weak" point of the method, particularly if complex lipid mixtures are to be analyzed. Although the detailed role of the matrix is not yet completely clear, it will be also explicitly shown that the careful choice of the matrix is crucial in order to be able to detect all compounds of interest. Two rather recent developments will be highlighted: "Imaging" MS is nowadays widely established and significant interest is paid in this context to the analysis of lipids because lipids ionize particularly well and are, thus, more sensitively detectable in tissue slices than other biomolecules such as proteins. It will also be shown that MALDI MS can be very easily combined with thin-layer chromatography (TLC) allowing the spatially-resolved screening of the entire TLC plate and the detection of lipids with a higher sensitivity than common staining protocols.

Maldi-tof mass spectrometry profiling of polar and nonpolar fractions in heated vegetable oils

Triacylglycerol oxidation of thermally stressed (6 h at 180 degrees C, simulating deep-frying conditions) edible vegetable oil (sunflower and olive) was studied using matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). Chromatographic separation of the nonpolar and polar components from the heated oil performed on silica gel prior to MS analysis significantly enhanced the detection of oxidized components. The spectra contained signals that were assigned to triacylglycerols (TAG), diacylglycerols (DAG), triacylglycerol oxidative dimers, oxidized TAG, and TAG fragments arising from the homolytic beta-scission of linoleyl, peroxy, and alkoxy radicals. Enrichment of the polar compounds prevented mass spectrometric ion suppression, thus allowing the detection of minor species originating from thermal oxidation. In addition, this allowed the monitoring of polar compounds in vegetable oils undergoing mild thermal treatment. As such, chromatographic separation coupled with MALDI-TOF MS analysis provided a rapid, sensitive, and specific tool to assess the thermal oxidation of vegetable oils.

Amazonian vegetable oils and fats: fast typification and quality control via triacylglycerol (TAG) profiles from dry matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry fingerprinting

Amazonian oils and fats display unique triacylglycerol (TAG) profiles and, because of their economic importance as renewable raw materials and use by the cosmetic and food industries, are often subject to adulteration and forgery. Representative samples of these oils (andiroba, Brazil nut, buriti, and passion fruit) and fats (cupuaçu, murumuru, and ucuúba) were characterized without pre-separation or derivatization via dry (solvent-free) matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS). Characteristic profiles of TAG were obtained for each oil and fat. Dry MALDI-TOF MS provides typification and direct and detailed information, via TAG profiles, of their variable combinations of fatty acids. A database from spectra could be developed and may be used for their fast and reliable typification, application screening, and quality control.

Characterization of natural wax esters by MALDI-TOF mass spectrometry

The applicability of matrix-assisted laser desorption/ionization time of flight mass spectrometry (MALDI-TOF MS) to the analysis of wax esters (WEs) was investigated. A series of metal salts of 2,5-dihydroxybenzoic acid (DHB) was synthesized and tested as possible matrices. Alkali metal (Li, Na, K, Rb, Cs) and transition metal (Cu, Ag) salts were studied. The matrix properties were evaluated, including solubility in organic solvents, threshold laser power that should be applied for successful desorption/ionization of WEs, the nature of the matrix ions and the mass range occupied by them, and the complexity of the isotope clusters for individual metals. Lithium salt of dihydroxybenzoic acid (LiDHB) performed the best and matrices with purified lithium isotopes ((6)LiDHB or (7)LiDHB) were recommended for WEs. Three sample preparation procedures were compared: (1) mixing the sample and matrix in a glass vial and deposition of the mixture on a MALDI plate (Mix), (2) deposition of sample followed by deposition of matrix (Sa/Ma), and (3) deposition of matrix followed by deposition of sample (Ma/Sa). Morphology of the samples was studied by scanning electron microscopy. The best sample preparation technique was Ma/Sa with the optimum sample to matrix molar ratio 1 : 100. Detection limit was in the low picomolar range. The relative response of WEs decreased with their molecular weight, and minor differences between signals of saturated and monounsaturated WEs were observed. MALDI spectra of WEs showed molecular adducts with lithium [M + Li](+). Fragments observed in postsource decay (PSD) spectra were related to the acidic part of WEs [RCOOH + Li](+) and they were used for structure assignment. MALDI with LiDHB was used for several samples of natural origin, including insect and plant WEs. A good agreement with GC/MS data was achieved. Moreover, MALDI allowed higher WEs to be analyzed, up to 64 carbon atoms in Ginkgo biloba leaves extract.