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Comprehensive two-dimensional gas chromatography with time-of-flight mass spectrometry (GC × GC-TOFMS) is one the most powerful analytical platforms for chemical investigations of complex biological samples. It produces large datasets that are rich in information, but highly complex, and its consistency may be affected by random systemic fluctuations and/or changes in the experimental parameters. This study details the optimization of a data processing strategy that compensates for severe 2D pattern misalignments and detector response fluctuations for saliva samples analyzed across 2 years. The strategy was trained on two batches: one with samples from healthy subjects who had undergone dietary intervention with high/low-Maillard reaction products (dataset A), and the second from healthy/unhealthy obese individuals (dataset B). The combined untargeted and targeted pattern recognition algorithm (i.e., UT fingerprinting) was tuned for key process parameters, the signal-to-noise ratio (S/N), and MS spectrum similarity thresholds, and then tested for the best transform function (global or local, affine or low-degree polynomial) for pattern realignment in the temporal domain. Reliable peak detection achieved its best performance, computed as % of false negative/positive matches, with a S/N threshold of 50 and spectral similarity direct match factor (DMF) of 700. Cross-alignment of bi-dimensional (2D) peaks in the temporal domain was fully effective with a supervised operation including multiple centroids (reference peaks) and a match-and-transform strategy using affine functions. Regarding the performance-derived response fluctuations, the most promising strategy for cross-comparative analysis and data fusion included the mass spectral total useful signal (MSTUS) approach followed by Z-score normalization on the resulting matrix.

The Maillard reaction products (MRPs) 3-deoxyglucosone (3-DG) and 5-hydroxymethylfurfural (HMF), which are formed during the thermal processing and storage of food, come into contact with technologically used yeasts during the fermentation of beer and wine. In order for the yeast cells to work efficiently, handling of the stress-inducing carbonyl compounds is essential. In the present study, the utilization of 3-DG and HMF by 13 Saccharomyces yeast strains (7 brewer’s yeast strains, 1 wine yeast strain, 6 yeast strains isolated from natural habitats) was investigated. All yeast strains studied were able to metabolize 3-DG and HMF. 3-DG is mainly reduced to 3-deoxyfructose (3-DF) and HMF is completely converted to 2,5-bishydroxymethylfuran (BHMF) and 5-formyl-2-furancarboxylic acid (FFCA). The ratio of conversion of HMF to BHMF and FFCA was found to be yeast strain-specific and no differences in the HMF stress tolerance of the yeast strains and species were observed. After incubation with 3-DG, varying amounts of intra- and extracellular 3-DF were found, pointing to a faster transport of 3-DG into the cells in the case of brewer’s yeast strains. Furthermore, the brewer’s yeast strains showed a significantly higher 3-DG stress resistance than the investigated yeast strains isolated from natural habitats. Thus, it can be shown for the first time that Saccharomyces yeast strains differ in their interaction of 3-DG induced carbonyl stress. Graphical abstract

The aim of this study was to investigate the amino acid composition and the amount of individual glycation compounds in hot trub formed during boiling of wort prepared from different malts. Compared to the initial amino acid composition of the used malts, some Maillard reaction products (namely MG-H1, pyrraline) and hydrophobic amino acids (leucine, isoleucine, valine, phenylalanine) accumulated in the hot trub, whereas hydrophilic amino acids remained in the boiled wort. For MG-H1, a threefold increase was observed during wort boiling, whereas the other Maillard reaction products, namely CML, CEL, pyrraline and maltosine increased only slightly (1.1–2-fold). Furosine as a hallmark for peptide-bound Amadori compounds showed a small decrease. The results suggest that mainly glycated amino acids derived from small dicarbonyl compounds such as methylglyoxal and glyoxal are formed during wort boiling. Furthermore, the studies indicate that the modification of the protein structure as a result of the Maillard reaction has an influence on the hydration of the denatured proteins during the wort boiling process, thus affecting the coagulation process and, therefore, precipitation of the hot trub. The work carried out contributes to the understanding of the chemical reactions influencing the amino acid and Maillard reaction product transfer from malt to beer. Graphical abstract

To investigate the influence of the internal micellar structure on the course of enzymatic cross-linking especially in the initial phase of the reaction, casein micelles isolated from raw milk via ultracentrifugation were incubated with microbial transglutaminase (mTG) in comparison with non-micellar sodium caseinate. Reactive lysine and glutamine residues were identified using a label-free approach, based on the identification of isopeptides within tryptic hydrolysates by targeted HRMS as well as manual monitoring of fragmentation spectra. Identified reactive sites were furthermore weighted by tracking the formation of isopeptides over an incubation time of 15, 30, 45 and 60 min, respectively. Fifteen isopeptides formed in the early stage of mTG cross-linking of caseins were identified and further specified concerning the position of lysine and glutamine residues involved in the reaction. The results revealed lysine K176 and glutamine Q175 of β-casein as the most reactive residues, which might be located in a highly flexible region of the molecule based on different possible reaction partners identified in this study. Except for the isopeptide αs1 K34–αs2 Q101 in sodium caseinate (SC), all reactive sites were detected in micellar and in non-micellar casein, indicating that the initial phase of enzymatic cross-linking is not affected by micellar aggregation of caseins. Graphical abstract

For peanuts, roasted at 170 °C, the formation of selected glycerol-bound oxidized fatty acids (GOFAs), namely 9-oxononanoic acid (9-ONA), azelaic acid (AZA) and octanoic acid, was observed by GC-MS (EI). The content of octanoic acid as well as AZA increased with continuous roasting time (from 59 mg/kg peanut oil to 101 mg/kg peanut oil and from not detectable to 8 mg/kg peanut oil, respectively), whereas the content of 9-ONA initially decreased from 25 mg/kg peanut oil to 8 mg/kg peanut oil (20 min) and increased again up to 37 mg/kg peanut oil following roasting for 40 min. Due to its aldehyde function, 9-ONA could contribute to amino acid side chain modifications as a result of lipation, which could directly influence the functional properties of peanut proteins. Both 9-ONA and octanoic acid are potential markers of thermal processes. Furthermore, in model experiments using methyl linoleate and methyl oleate, up to 18 oxidized fatty acids could be identified as methyl esters, 9-ONA as well as octanoic acid as major components and a faster formation of GOFAs under roasting conditions (170 °C, 20 min). In addition, 9-ONA contributes to the formation of AZA and octanoic acid in both free and bound form as a result of oxidative subsequent reactions in presence of iron (III).

Subsequent to the dietary uptake of nitrate/nitrite in combination with acetaldehyde/ethanol, combination effects resulting from the sustained endogenous exposure to nitrite and acetaldehyde may be expected. This may imply locoregional effects in the upper gastrointestinal tract as well as systemic effects, such as a potential influence on endogenous formation of N-nitroso compounds (NOC). Salivary concentrations of the individual components nitrate and nitrite and acetaldehyde are known to rise after ingestion, absorption and systemic distribution, thereby reflecting their respective plasma kinetics and parallel secretion through the salivary glands as well as the microbial/enzymatic metabolism in the oral cavity. Salivary excretion may also occur with certain drug molecules and food constituents and their metabolites. Therefore, putative combination effects in the oral cavity and the upper digestive tract may occur, but this has remained largely unexplored up to now. In this Guest Editorial, published evidence on exposure levels and biokinetics of nitrate/nitrite/NOx, NOC and acetaldehyde in the organism is reviewed and knowledge gaps concerning combination effects are identified. Research is suggested to be initiated to study the related unresolved issues. published

This opinion of the Senate Commission on Food Safety (SKLM) of the German Research Foundation (Deutsche Forschungsgemeinschaft, DFG) presents arguments for an updated risk assessment of diet-related exposure to acrylamide (AA), based on a critical review of scientific evidence relevant to low dose exposure. The SKLM arrives at the conclusion that as long as an appropriate exposure limit for AA is not exceeded, genotoxic effects resulting in carcinogenicity are unlikely to occur. Based on the totality of the evidence, the SKLM considers it scientifically justified to derive a tolerable daily intake (TDI) as a health-based guidance value. published

Background Even though some Dracaena species are used as medicine, their utilization as food is rather unusual. In northern Angola, however, leaves and underground tubers of Dracaena camerooniana Baker are frequently consumed. In particular, the leaves are of increasing economic value in the region. But the anatomy and nutritional aspects of the plant have not been studied so far. Therefore, a detailed anatomic description of the plant was conducted. In a second step the nutritional value of the defined material was analysed, providing a basis for the discussion of a more intensive utilisation of this rainforest shrub. Results The leaf anatomy of Dracaena camerooniana differs from the species of the genus that have been examined so far, in showing adaptations to wet climatic conditions. The stems produce a secondary thickening meristem with amphivasal secondary vascular bundles. During tuber formation, the parenchyma of the pith in the vascular cylinder of the root markedly increases. From a nutritional point of view, leaves do not noteworthy contribute to vitamin intake. The nutritional composition of the tubers is comparable to that of cassava (Manihot esculenta Crantz ) and potatoes (Solanum tuberosum L.). However, a high fructose value indicates inulin as a storage carbohydrate. Conclusion Inspite of its rather moderate nutritional values, Dracaena camerooniana is an indigenous addition to the diet of the Angolan population that could also be cultivated in the future due to the easy vegetative propagation.

The Maillard reaction is traditionally subdivided into three stages that start consecutively and run in parallel. Here, we show that N-ε-carboxymethyllysine (CML), a compound formed in the late stage of the reaction, can undergo a second glycation event at its secondary amino group leading to a new class of Amadori rearrangement products. When N-α-hippuryl-CML was incubated in the presence of reducing sugars such as glucose, galactose, ribose, xylose, maltose, or lactose in solution for 1 h at 75 °C, the compound was degraded by 6–21%, and N-ε-carboxymethyl-N-ε-deoxyketosyl lysine derivatives were formed. Under the same conditions, lysine was 5–10 times more reactive than CML. N-α-hippuryl-N-ε-carboxymethyl-N-ε-(1-deoxyfructosyl)-l-lysine (hippuryl-CMFL) and N-ε-carboxymethyl-N-ε-(1-deoxyfructosyl)-l-lysine (CMFL) were synthesized, isolated and characterized by MS/MS and NMR experiments. Depending on the reaction conditions, up to 21% of CMFL can be converted to the furosine analogue N-ε-carboxymethyl-N-ε-furoylmethyl-l-lysine (CM-Fur) during standard acid protein hydrolysis with hydrochloric acid. Incubation of bovine serum albumin (BSA) with glucose for up to 9 weeks at 37 °C revealed the formation of CMFL in the protein as assessed by HPLC–MS/MS in the MRM mode. Under these conditions, ca. 13% of lysine residues had been converted to fructosyllysine, and 0.03% had been converted to CMFL. The detection of glycation products of glycated amino acids (heterogeneous multiple glycation) reveals a novel pathway in the Maillard reaction.

Glycation and caramelization reactions in malt lead to the formation of 1,2-dicarbonyl compounds, which come in contact with yeast during fermentation. In the present study, the metabolic fate of 5-hydroxymethylfurfural (HMF) and 1,2-dicarbonyl compounds (3-deoxyglucosone, 3-deoxygalactosone, 3-deoxypentosone, 3,4-dideoxyglucosone-3-ene) was assessed in the presence of Saccharomyces cerevisiae. HMF is degraded very fast by yeast with the formation of 2,5-bis(hydroxymethyl)furan (BHMF). By contrast, only 7-30% of 250 μM dicarbonyl compounds is degraded within 48 h. The respective deoxyketoses, 3-deoxyfructose (3-DF), 3-deoxytagatose, 3-deoxypentulose, and 3,4-dideoxyfructose, were identified as metabolites. While 17.8% of 3-deoxyglucosone was converted to 3-deoxyfructose, only about 0.1% of 3-deoxypentosone was converted to 3-deoxypentulose during 48 h. Starting with the parent dicarbonyl compounds, the synthesis of all deoxyketose metabolites was achieved by applying a metal-catalyzed reduction in the presence of molecular hydrogen. In a small set of commercial beer samples, BHMF and all deoxyketoses were qualitatively detected. 3-DF was quantitated in the four commercial beer samples at concentrations between 0.4 and 10.1 mg/L.

Since the addition of fluoride to drinking water in the 1940s, there have been frequent and sometimes heated discussions regarding its benefits and risks. In a recently published review, we addressed the question if current exposure levels in Europe represent a risk to human health. This review was discussed in an editorial asking why we did not calculate benchmark doses (BMD) of fluoride neurotoxicity for humans. Here, we address the question, why it is problematic to calculate BMDs based on the currently available data. Briefly, the conclusions of the available studies are not homogeneous, reporting negative as well as positive results; moreover, the positive studies lack control of confounding factors such as the influence of well-known neurotoxicants. We also discuss the limitations of several further epidemiological studies that did not meet the inclusion criteria of our review. Finally, it is important to not only focus on epidemiological studies. Rather, risk analysis should consider all available data, including epidemiological, animal, as well as in vitro studies. Despite remaining uncertainties, the totality of evidence does not support the notion that fluoride should be considered a human developmental neurotoxicant at current exposure levels in European countries.

Protein-polyphenol interactions affect the structure, stability, and functional properties of proteins and polyphenols. Oxidized polyphenols (o-quinones) react rapidly with the sulfhydryl group of cysteine (Cys) residues, inducing covalent bonding between proteins and polyphenols. However, quantitative data on such reactions remain elusive, despite the importance of depicting the significance of such interactions on food structure and function. This work reports the synthesis, purification, and characterization of caffeic acid-cysteine (CA-Cys) and chlorogenic acid-cysteine (CGA-Cys) adducts and their stable isotope analogs, CA-[13C3,15N]Cys and CGA-[13C3,15N]Cys. A sensitive LC-MS/MS isotope dilution method was developed to simultaneously quantify these adducts in foods and beverages. Protein-bound CA-Cys and CGA-Cys were detected in the micro-molar range in milk samples with added CA and CGA, confirming covalent bonding between milk proteins and CA/CGA. These adducts were detected in commercial coffee-containing beverages but not in cocoa-containing drinks. Furthermore, the adducts were found to be partially stable during enzymatic protein hydrolysis.

3-Deoxyglucosone (3-DG) is a Maillard reaction intermediate, which forms known beer aging compounds such as Strecker aldehydes. However, the role of 3-DG in beer aging stability has not been described yet. To investigate the influence of 3-DG toward beer aging stability, different concentrations of 3-DG were added to the freshly brewed beer at the beginning of storage. Analysis of well-known degradation products of 3-DG such as 3-deoxygalactosone (HPLC-UV), 5-hydroxymethylfurfural (HPLC-UV), Strecker aldehydes (GC-MS), and free glycated amino acids (HPLC-MS/MS) during beer aging revealed that a higher initial 3-DG concentration increases the formation of the products. In this study, the significant importance of 3-DG as a key precursor compound in beer aging has been shown, especially the increase of Strecker aldehydes.

Individual Maillard reaction products (MRPs), namely, free and protein-bound glycated amino acids as well as dicarbonyl compounds, were quantitated in various types of brewing malt using chromatographic means. Among the protein-bound glycated amino acids, which were analyzed following enzymatic hydrolysis, N-e-fructosyllysine was the dominating compound in light (EBC < 10) and dark (10 < EBC < 500) malts, accounting for up to 15.9% of lysine derivatization, followed by N-e-maltulosyllysine (light malts, up to 4.9% lysine derivatization) or pyrraline (dark malts, up to 10.4% lysine derivatization). Roasting of malt led to the degradation of most of the protein-bound glycated amino acids. The same trends were visible for free glycated amino acids. A novel MRP-derived Strecker aldehyde, namely, 5-(2'-formyl-5'-hydroxymethylpyrrol-1'-yl)-pentanal (pyrralinal), was detected in dark malt. The most abundant 1,2-dicarbonyl compound in malt samples was 3-deoxyglucosone (up to 9 mmol/kg), followed by 3-deoxymaltosone (up to 2 mmol/kg). Only few MRPs such as 5-hydroxymethylfurfural, furfural, the dicarbonyl compounds glyoxal, methylglyoxal, and diacetyl as well as protein-bound rhamnolysine and MG-H1 correlated with the malt color. A comparison of MRPs present in malt with corresponding amounts in beer points to neoformation of MRPs such as MG-H1 and 3-deoxygalactosone during the brewing process.

Thermally processed food is an important part of the human diet. Heat-treatment, however, promotes the formation of so-called Amadori rearrangement products, such as fructoselysine. The gut microbiota including Escherichia coli can utilize these compounds as a nutrient source. While the degradation route for fructoselysine is well described, regulation of the corresponding pathway genes frlABCD remained poorly understood. Here, we used bioinformatics combined with molecular and biochemical analyses and show that fructoselysine metabolism in E. coli is tightly controlled at the transcriptional level. The global regulator CRP (CAP) as well as the alternative sigma factor σ32 (RpoH) contribute to promoter activation at high cAMP-levels and inside warm-blooded hosts, respectively. In addition, we identified and characterized a transcriptional regulator FrlR, encoded adjacent to frlABCD, as fructoselysine-6-phosphate specific repressor. Our study provides profound evidence that the interplay of global and substrate-specific regulation is a perfect adaptation strategy to efficiently utilize unusual substrates within the human gut environment.

Herbivorous animals that regularly consume tannin-rich food are known to secrete certain tannin-binding salivary proteins (TBSPs), especially proline-rich proteins and histidine-rich proteins, as an effective measure to counteract the antinutritive effects of dietary tannins. Due to their high binding capacity, TBSPs complex with tannins in the oral cavity, and thereby protect dietary proteins and digestive enzymes. Although the natural diet of great apes (Hominidae) is biased toward ripe fruits, analyses of food plants revealed that their natural diet contains considerable amounts of tannins, which is raising the question of possible counter-measures to cope with dietary tannins. In our study, we investigated the salivary amino acid profiles of zoo-housed Pan paniscus, Pan troglodytes, Gorilla gorilla, and Pongo abelii, and compared their results with corresponding data from Homo sapiens. Individual saliva samples of 42 apes and 17 humans were collected and quantitated by amino acid analysis, using cation-exchange chromatography with postcolumn derivatization, following acid hydrolysis. We found species-specific differences in the salivary amino acid profiles with average total salivary protein concentration ranging from 308.8 mg/dL in Po. abelii to 1165.6 mg/dL in G. gorilla. Total salivary protein was consistently higher in ape than in human saliva samples (174 mg/dL). All apes had on average also higher relative proline levels than humans did. Histidine levels had the highest concentration in the samples from Po. abelii followed by P. paniscus. In all ape species, the high salivary concentrations of proline and histidine are considered to be indicative of high concentrations of TBSPs in hominids. Given that the species differences in salivary composition obtained in this study correspond with overall patterns of secondary compound content in the diet of wild populations, we assume that salivary composition is resilient to acute and long-lasting changes in diet composition in general and tannin content in particular.

Using reversed phase high-performance liquid chromatography with ultraviolet (UV) detection and electrospray ionization (ESI)-quadrupole time-of-flight mass spectrometry (RP-HPLC-UV-ESI-Q-TOF), the lysozyme content in the milk of 10 volunteering mothers was quantified, ranging from 29 to 96 μg/mL. Following ultracentifugation, it was found that the lysozyme in human milk, unlike other whey proteins, is mainly bound to casein micelles (ca. 75%). The enzymatic activity of human lysozyme, measured as lytic activity against cell walls of

Detailed investigations of the reaction pathway to trinuclear oxo-bridged uranyl complexes.

Acetaldehyd kommt natürlicherweise in zahlreichen Lebensmitteln vor und wird aufgrund seines fruchtigen Aromas auch als Aromastoff eingesetzt. Die Internationale Agentur für Krebsforschung (IARC) stufte Acetaldehyd als möglicherweise krebserregend sowie in Verbindung mit der oralen Aufnahme über alkoholhaltige Getränke als humanes Kanzerogen ein. Vor diesem Hintergrund stellt sich die Frage, ob die Verwendung von Acetaldehyd als Aromastoff weiterhin vertretbar ist. Die Senatskommission zur gesundheitlichen Bewertung von Lebensmitteln (SKLM) der Deutschen Forschungsgemeinschaft (DFG) hat die aktuelle Datenlage zur Bewertung des gesundheitlichen Risikos der Verwendung von Acetaldehyd als Aromastoff geprüft und hierzu eine Stellungnahme verabschiedet. Demnach kann die Frage, ob Acetaldehyd nach oraler Exposition in vivo gentoxisch und mutagen wirkt, derzeit nicht abschließend beantwortet werden. Weiterhin ist auch unklar, welchen Beitrag die Verwendung von Acetaldehyd als Aromastoff zur Gesamtexposition des Verbrauchers gegenüber Acetaldehyd leistet. Eine wissenschaftliche Bewertung des gesundheitlichen Risikos der Verwendung von Acetaldehyd als Aromastoff ist daher weiterhin nicht möglich. Die SKLM weist darauf hin, dass aufgrund des gentoxischen Gefährdungspotenzials sowie zahlreicher Datenlücken, die für eine vollständige Risikobewertung geschlossen werden müssen, Zweifel an der Sicherheit von Acetaldehyd als Aromastoff bestehen. Nach Ansicht der SKLM sollte der gezielte Zusatz von Acetaldehyd als Aromastoff aus Gründen des vorsorgenden Verbraucherschutzes neu beurteilt werden. Acetaldehyde occurs naturally in many foods and is also used as a flavouring due to its fruity aroma. The International Agency for Research on Cancer (IARC) classified acetaldehyde as possibly carcinogenic to humans and, in combination with oral intake via alcoholic beverages, as carcinogenic to humans. Therefore, the question arises whether the use of acetaldehyde as a flavouring agent is still justifiable. The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) reviewed the scientific basis for health risk assessment of the use of acetaldehyde as a flavouring substance and adopted an opinion. Based on the available data, it is at present not possible to conclude if acetaldehyde is genotoxic and mutagenic in vivo after oral exposure. There is also uncertainty regarding the contribution of acetaldehyde as a flavouring substance to the overall exposure to acetaldehyde. Therefore, a science-based assessment on health risk related to the use of acetaldehyde as a flavouring is not possible at present. Considering the genotoxic potential as well as numerous data gaps that need to be closed for a full risk assessment, the SKLM is concerned about the safety of acetaldehyde as a flavouring substance. For reasons of precautionary consumer protection, the SKLM considers that the use of acetaldehyde as a food additive should be re-evaluated.

The adsorption of bovine milk caseins on the tooth surface might have a positive impact on the prevention of dental diseases. Therefore, the present study aimed to investigate the efficacy of mouthrinses with different types of bovine milk and milk protein isolates to accumulate caseins in the pellicle. An indirect enzyme-linked immunosorbent assay (ELISA) was established to quantify the amount of caseins adsorbed into the in situ pellicle. In situ pellicle samples were collected from 2 volunteers on ceramic specimens (A = 8 cm2). After 10 min of pellicle formation, different types of bovine milk, 3% micellar casein in synthetic milk ultrafiltrate (SMUF) or 3% non-micellar caseinate in SMUF, were used as mouthrinses for 10 min. The pellicle material was harvested after 30 min in situ and examined for caseins by the indirect ELISA. Selected pellicle samples were subjected to TEM analysis. All mouthrinses accumulated caseins in the in situ pellicle (2.0 ± 0.7–20 ± 1.7 μg/ml) that, under native conditions, expressed no casein signal. Micellar protein association increased the adsorption of casein into the pellicle. Milk homogenization also had an influence on the casein accumulation in the pellicle. TEM analysis confirmed the integration of micellar casein into the pellicle. The mouthrinses altered the protein composition and the ultrastructure of the in situ pellicle to a different extent: bovine milk with 3.8% fat content and 3% micellar casein in SMUF being particularly effective. The study provides interesting perspectives for innovative prevention strategies in dentistry.

The influence of covalent protein modifications resulting from the Maillard reaction (glycation) of casein and lactose on the noncovalent association behavior of the protein was studied. Nonenzymatic cross-linking with methylglyoxal (MGO) and glutaraldehyde (GTA) as well as enzymatic cross-linking with microbial transglutaminase (mTG) was investigated in comparison. Molar mass, particle size, and conformational characteristics of nonmicellar casein associates as well as the extent of intraparticle protein cross-linking were examined utilizing size-exclusion chromatography (SEC) combined with UV detection and static and dynamic light scattering. Cross-linking resulted in the stabilization of a certain fraction of casein associates, with particle sizes of approximately 30 nm in radius of gyration (

Individual Maillard reaction products (MRPs), namely furosine, which is formed from Amadori product of lysine during acid hydrolysis, as well as N-ε-(carboxymethyl)lysine (CML), pyrraline and the arginine derivative MG-H1 (methylglyoxal-derived hydroimidazolone 1) were quantified in 78 samples of animal feed, belonging to 17 different feed types. The concentrations of the MRPs were dependent on the heat treatment during processing. Within similar feed types, significant differences in concentrations could be observed. MRPs can be suitable indicators to evaluate the impact of technological processing on the nutritional quality of animal feed.

Flavor instability of beer is affected by the rise of aroma-active aldehydes during aging. Aldehydes can be either released from bound-state forms or formed de novo. This second part of our study focused on the de novo formation of aldehydes during the Maillard reaction, Strecker degradation, and oxidation reactions. Key precursor compounds for de novo pathways are free amino acids. This study varied the potential for reactions by varying free amino acid content in fresh beer using different proteolytic malt modification levels (569–731 mg/100 g d. m. of soluble nitrogen) of the used malt in brewing trials. Overall, six pale lager beers were produced from three malts (different malt modification levels), each was made from two different barley varieties and was naturally and forcibly aged. It was found that higher malt modification levels in fresh beer and during beer aging increased amino acid and dicarbonyl concentrations as aging precursors and Strecker aldehyde contents as aging indicators. Dicarbonyls were degraded during aging. Advanced glycation end products as possible degradation products showed no consistent formation during aging. Therefore, Strecker reactions were favored during beer aging. No alternative oxidative formation of Strecker aldehydes from their corresponding alcohols could be confirmed. Along with the preceding part one of our investigation, the results of this study showed that de novo formation and release occur simultaneously. After 4 months of natural aging, aldehyde rise is mainly accounted for by de novo formation.

During food processing and storage, and in tissues and fluids under physiological conditions, the Maillard reaction occurs. During this reaction, reactive 1,2-dicarbonyl compounds arise as intermediates that undergo further reactions to form advanced glycation end products (AGEs). Diet is the primary source of exogenous AGEs. Endogenously formed AGEs have been proposed as a risk factor in the pathogenesis of diet-related diseases such as diabetes, insulin resistance, cardiovascular diseases, or chronic disease. AGEs may differently contribute to the diet-related exacerbation of oxidative stress, inflammation, and protein modifications. Here, to understand the contribution of each compound, we tested individually, for the first time, the effect of five 1,2-dicarbonyl compounds 3-deoxyglucosone (3-DG), 3-deoxygalactosone (3-DGal), 3,4-dideoxyglucosone-3-ene (3,4-DGE), glyoxal (GO), and methylglyoxal (MGO) and four different glycated amino acids N-ε-(carboxyethyl)lysine (CEL), N- ε -(carboxymethyl)lysine (CML), methylglyoxal-derived hydroimidazolone-1 (MG-H1), and pyrraline (Pyrr) in a cell line of human keratinocytes (HaCaT). We found that most of the glycated amino acids, i.e., CEL, CML, and MG-H1, did not show any cytotoxicity. At the same time, 1,2-dicarbonyl compounds 3-DGal, 3,4-DGE, GO, and MGO increased the production of reactive oxygen species and induced cell death. MGO induced cell death by apoptosis, whereas 3-DGal and 3,4-DGE induced nuclear translocation of the proinflammatory NF-κB transcription pathway, and the activation of the pyroptosis-related NLRP3 inflammasome cascade. Overall, these results demonstrate the higher toxic impact of 1,2-dicarbonyl compounds on mucosal epithelial cells when compared to glycated amino acids and the selective activation of intracellular signaling pathways involved in the crosstalk mechanisms linking oxidative stress to excessive inflammation.

Evidence has suggested that major peanut allergen Ara h 1 activates dendritic cells (DCs) via interaction with DC-SIGN (dendritic cell-specific intercellular adhesion molecule-3-grabbing non-integrin), a C-type lectin receptor, and contributes to development of peanut allergy. Since macrophages, as well as DCs, play a crucial role in innate immunity, we investigated whether natural Ara h 1 (nAra h 1) activates two different subsets of macrophages, human monocyte derived macrophage type 1 (hMDM1: pro-inflammatory model) and type 2 (hMDM2: anti-inflammatory model). hMDM1 and hMDM2 predominantly produced pro-inflammatory cytokines (IL-6 and TNF-α) and an anti-inflammatory cytokine (IL-10) in response to nAra h 1, respectively. hMDM2 took up nAra h 1 and expressed DC-SIGN at higher levels than hMDM1. However, small interfering RNA knockdown of DC-SIGN did not suppress nAra h 1 uptake and nAra h 1-mediated cytokine production in hMDM2. Inhibitors of scavenger receptor class A type I (SR-AI) suppressed the response of hMDM2, but not of hMDM1, suggesting that SR-AI is a major receptor in hMDM2 for nAra h 1 recognition and internalization. nAra h 1 appears to exert stimulatory capacity on DC and macrophages via different receptors. This study advances our understanding how a major peanut allergen interacts with innate immunity.