Development of stable isotope dilution assays for the quantitation of Amadori compounds in foods

Preparation of red jujube powder with high content of Amadori compounds and higher antioxidant activity by controlling the Maillard reaction

Amadori compounds (ACs) are stable compounds produced in the early stage of the Maillard reaction (MR) with health benefits such as immunomodulatory, antithrombosis, and tumor-preventive effects. Jujube is a medicinal and edible fruit in China. It is rich in free amino acids and reducing sugar, but traditionally, little attention was paid to the formation of ACs when jujube was processed, neither the influence of ACs on health effects. In this paper, we aimed to increase ACs through controlling the MR during different heating processes of jujube powder with adjusted water content and find the most effective AC that contributed to the antioxidant effects of jujube powder. The optimal dry-heating conditions to produce ACs were as follows: The water activity was 0.294, the heating temperature was 90°C, and the time was 120 min. After processing, the ACs content of jujube powder was 18.55 ± 0.19 mg/g dry weight (DW), which was more than 100 times of those in the unheated jujube powder (0.153 ± 0.003 mg/g DW). Besides, the antioxidant activity of jujube powder after dry-heating process was higher than that of unheated one. As the most abundant AC in the dry-heated jujube powder (12.90 ± 0.75 mg/g DW), N-(1-deoxy-d-fructose-1-yl) proline (Fru-Pro) showed the highest antioxidant activity (62% of equivalent l-ascorbic acid) among 12 ACs in ferric reducing antioxidant power assay. This result provided a method to produce jujube product with high content of ACs and confirmed the positive contribution of Fru-Pro to the antioxidant activity of the jujube powder.

Fate of Amadori compounds in processing and digestion of multi-ingredients tomato based sauces and their effect on other microconstituents

Amadori compounds (ACs), the first stable products of Maillard reaction, are detected in various products of fruits and vegetables, and show an antioxidant activity which can be related to beneficial effects in human health. In order to optimize the nutritional quality of a multi-ingredient tomato sauce (tomato puree - onion - olive oil - dried pepper), the fate of ACs during processing (drying, heating) and gastrointestinal digestion of a model meal was assessed as well as that of other microconstituents, i.e. carotenoids, phenolic compounds and capsaicinoids. The drying at 50 °C of fresh pepper induced the formation and accumulation of ACs after 6 days. During the heat treatment by microwave of multi-ingredient tomato sauce, Maillard reaction occurs in presence of dried pepper and the content in ACs in the tomato-based sauces increased (+33% to + 53%) depending of quantities of dried pepper added. The bioaccessibility of total ACs was 24-31% in duodenal phase and 18-22% in jejunal phase. Individual ACs have shown variable bioaccessibility, e.g. very high for Fru-Arg (50.8% to 71.3%), and very low for Fru-Met (1.8% to 2.2%). The kinetic monitoring of ACs in digestion medium showed that ACs are not stable (-46% in gastric phase, -49 % in intestinal phase) which indicated their potential degradation in the digestive tract. The presence of ACs in the multi-ingredients tomato sauces had no effect on the content of the other bioactive compounds monitored in the study and even promoted the bioaccessibility of total lycopene (+30%) but decreased the bioaccessibility of total phenolic compounds.

Mechanism of Pyrazine Formation Intervened by Oxidized Methionines during Thermal Degradation of the Methionine-Glucose Amadori Compound

Methionine (Met) oxidation was observed during thermal degradation of methionine/glucose-derived Amadori rearrangement product (MG-ARP). The effects of oxidized methionine products, methionine sulfoxide (MetSO) and methionine sulfone (MetSO₂), on pyrazine yields of the MG-ARP model were investigated. The pyrazine contents in the MG-ARP/Met and MG-ARP/MetSO models were found lower compared to those in the MG-ARP/MetSO₂ model, and the inefficiency of pyrazine formation in the MG-ARP/Met model was proposed due to the fact that Met oxidation competitively inhibited the oxidation of dihydropyrazines for pyrazine formation in spite of relatively high methylglyoxal (MGO) content. The models of MGO mixed with Met, MetSO, or MetSO₂ were established for further investigation of the mechanism for the involvement of Met oxidation in pyrazine formation. It was observed that the aldolization or carbonyl-amine reaction of MetSO with MGO was another important reason for the inhibition of pyrazine formation, except for the competitive inhibition of oxidative formation of MetSO on dihydropyrazine oxidation, and the adduct of MGO-MetSO was identified by MS/MS. These results also accounted for the phenomenon of low pyrazine yields but high yields of long-chain substituted pyrazines, which were converted from dihydropyrazines with the aldehyde involvement.

Comparison of the Phytochemical Variation of Non-Volatile Metabolites within Mother Tinctures of Arnica montana Prepared from Fresh and Dried Whole Plant Using UHPLC-HRMS Fingerprinting and Chemometric Analysis

Arnica montana L. has been recognized for centuries as an herbal remedy to treat wounds and promote healing. It also has a long tradition of use in homeopathy. Depending on its medicinal utilization, standardization regulations allow different manufacturing processes, implying different raw materials, such as the whole arnica plant in its fresh or dried state. In this study, an untargeted metabolomics approach with UHPLC-HRMS/MS was used to cross-compare the phytochemical composition of mother tinctures of A. montana that were prepared from either fresh whole plant (fMT) matter or from oven-dried whole plant (dMT) matter. The multivariate data analysis showed significant differences between fMT and dMT. The dereplication of the HRMS and MS/MS spectra of the more discriminant compounds led to annotated quinic acid, dicaffeoyl quinic acids, ethyl caffeate, thymol derivatives and dehydrophytosphingosine, which were increased in fMT, while Amadori rearrangement products (ARP) and methoxyoxaloyl-dicaffeoyl quinic acid esters were enhanced in dMT. Neither sesquiterpene lactones nor flavonoids were affected by the drying process. This is the first time that a sphingosine, ethyl caffeate and ARP are described in A. montana. Moreover, putative new natural products were detected as 10-hydroxy-8,9-epoxy-thymolisobutyrate and an oxidized proline fructose conjugate, for which isolation and full structure elucidation will be necessary to verify this finding.

Key Aspects of Amadori Rearrangement Products as Future Food Additives

Flavor is one of the most important factors in attracting consumers and maximizing food quality, and the Maillard reaction (MR) is highly-involved in flavor formation. However, Maillard reaction products have a big drawback in their relatively low stability in thermal treatment and storage. Amadori rearrangement products (ARPs), MR intermediates, can alternatively act as potential flavor additives for their better stability and fresh flavor formation ability. This review aims to elucidate key aspects of ARPs’ future application as flavorings. The development of current analytical technologies enables the precise characterization of ARPs, while advanced preparation methods such as synthesis, separation and drying processes can increase the yield of ARPs to up to 95%. The stability of ARPs is influenced by their chemical nature, pH value, temperature, water activity and food matrix. ARPs are associated with umami and kokumi taste enhancing effects, and the flavor formation is related to amino acids/peptides of the ARPs. Peptide-ARPs can generate peptide-specific flavors, such as: 1,6-dimethy-2(1H)-pyrazinone, 1,5-dimethy-2(1H)-pyrazinone, and 1,5,6-trimethy-2(1H)-pyrazinone. However, further research on systematic stability and toxicology are needed.

Vacuum Dehydration: An Excellent Method to Promote the Formation of Amadori Compounds (ACs, N-(1-Deoxy-d-fructos-1-yl)-amino Acid) in Aqueous Models and Tomato Sauce

Amadori compounds (ACs; N-(1-deoxy-d-fructos-1-yl)-amino acid) are superior flavor precursors and potential functional ingredients in food processing. In this study, vacuum dehydration as an excellent and universal method for the formation of ACs in both simulation systems and food processing was revealed. In total, 12 amino acids referring to all six categories were selected to conduct simulated reactions with glucose in aqueous models. At 90 °C, yields of 11 ACs were significantly increased by vacuum dehydration, reaching 4-198 times compared to a heat sealing reaction in aqueous systems, and formation of 5-hydroxymethyl-2-furaldehyde (5-HMF) and browning were slower than that by a dry powder reaction. In particular, the yields of Fru-Arg, Fru-His, and Fru-Glu reached 87.03, 90.73, and 89.88 mol %, respectively. The order of promotion effect was acid ACs > basic ACs > unique ACs > polar neutral ACs > aliphatic ACs > aromatic ACs. The excellent effect was mainly attributed to the control of water activity (Aw) and pH, which enabled the models to reach the optimal reaction state quickly by adjusting the vacuum degree at mild temperatures. The method was also applied to AC enrichment in tomato sauce processing; the AC content could rise to 30.72 mg/g, which was more than 17 times than those in samples without vacuum dehydration and two commercial tomato sauces.

LC-MS/MS for simultaneous detection and quantification of Amadori compounds in tomato products and dry foods and factors affecting the formation and antioxidant activities

In order to establish an efficient detection method to evaluate the formation of Amadori compounds (ACs) in food products and study the potential health effects, an ultra-high performance liquid chromatography-tandem mass spectrometric (UPLC-MS/MS) method using caffeine as internal standard was developed to determine eight ACs. The detection limits ranged from 0.0179 to 0.0887 mg/L for the ACs. The accuracy of the method was tested through measuring recovery of the spiked samples that varied from 81.90 ± 2.98% to 108.74 ± 2.34%. This method was further applied to detect ACs in 10 food products. Results showed that dry fruits and vegetables were rich in ACs, the total content of ACs varied from 1.36 ± 0.26 to 3415.91 ± 147.96 mg/100 g. The total amount of ACs in tomato juice heated under vacuum condition showed significant increment (P < 0.05) in 25 min at 80 °C comparing with that under atmospheric pressure due to the rapid loss of water. Besides, the amino acid content shows positive correlation with the corresponding AC formation in Maillard reaction during food drying. After heated at fixed water activity (Aw) for 4 hr by sous-vide process, the ACs content in tomato powder increased significantly and the antioxidant activity improved as well. PRACTICAL APPLICATION: Results of this study provided a valuable tool to evaluate the formation of ACs in complex dry food products, facilitated the quality control of food products. The knowledge obtained will offer useful information to food processors. The synthesized ACs would facilitate further study into the antioxidant activities and potential health effects of specified AC.

Interaction of (-)-Epigallocatechin Gallate and Deoxyosones Blocking the Subsequent Maillard Reaction and Improving the Yield of N-(1-Deoxy-d-xylulos-1-yl)alanine

(-)-Epigallocatechin gallate (EGCG) had a significant effect on Maillard reaction intermediate formation in the xylose/alanine model system. A trapping effect of EGCG on the reactive deoxyosones was observed to change the reaction pathways. The rate constant of Amadori rearrangement product (ARP) conversion to deoxyosones was decreased with EGCG addition, indicating an inhibition of ARP degradation. Dehydration improved the ARP formation during the thermal reaction and synergistically improved the yield of ARP with the EGCG trapping effect on the deoxyosones. Additionally, EGCG decreased the activation energy for the conversion of xylose/alanine to ARP (from 77.8 to 62.8 kJ/mol) and in turn accelerated the ARP formation. The effect of EGCG was further facilitated at the optimal conditions of 90 °C, at pH 7.5, and a molar ratio of xylose to alanine of 2:1, which improved the yield of ARP (N-(1-deoxy-d-xylulos-1-yl)alanine) from 2 to 95%.

Interaction of Added l-Cysteine with 2-Threityl-thiazolidine-4-carboxylic Acid Derived from the Xylose-Cysteine System Affecting Its Maillard Browning

The Maillard reaction under a stepwise increase of temperature using l-cysteine as the indicator was performed to determine the formation conditions for the preparation of 2-threityl-thiazolidine-4-carboxylic acid (TTCA) which was the main Maillard reaction intermediate (MRI) derived from the xylose (Xyl)-cysteine (Cys) model system in aqueous medium. To clarify the indicating mechanism of Cys for the TTCA formation, the thermal model systems of TTCA-Cys and TTCA solutions were investigated. The browning of the final Maillard reaction products (MRPs) and concentration of downstream degradation products of MRIs indicated that the added Cys could react with TTCA to inhibit the formation of visible color via preventing the generation of dicarbonyl compounds derived from MRIs. Through HPLC analysis, it was demonstrated that added Cys affected the normal reaction pathway from TTCA to ARP and other downstream products by restoring TTCA to sugar and amino acid under heat treatment.

Effective Mechanism of (-)-Epigallocatechin Gallate Indicating the Critical Formation Conditions of Amadori Compound during an Aqueous Maillard Reaction

The formation conditions of the Amadori compound (ARP) N-(1-deoxy-d-xylulos-1-yl)-alanine were determined in an aqueous Maillard reaction between l-alanine and d-xylose under a two-step temperature rising process with (-)-epigallocatechin gallate (EGCG) as an indicator followed by browning intensity detection of the final Maillard reaction products (MRPs). To clarify the mechanism of EGCG indication on the ARP formation, the change in the concentration of some key products generated during the Maillard reaction with EGCG addition was investigated. Results showed an inhibition effect of EGCG on the browning precursor formation through the generation of ARP-EGCG adducts and deoxyosone-EGCG adducts, which was proposed as an important pathway to inhibit browning during the Maillard reaction and to indicate ARP formation.

Discovery of Amadori-Type Conjugates in a Peptide Maillard Reaction and Their Corresponding Influence on the Formation of Pyrazines

Knowledge of the role of peptides in the Maillard reaction is rather limited. In this study, peptide Maillard reaction model systems were established. Volatile and nonvolatile MRPs (Maillard reaction products) were investigated by GC-O-MS and LC-MS. Carbohydrate module labeling (CAMOLA) experiments were performed to elucidate the carbon skeleton of these compounds. Results showed that the peptide reaction system generated more pyrazines than the free amino acid group. Several new Amadori-type conjugates were identified as novel Maillard reaction products that could greatly influence the formation of pyrazines. Our work suggested anew mechanism involving these Amadori-type conjugates and subsequent investigation revealed that the conjugates could be important intermediate products in the reaction between dicarbonyl and dipeptide. Our findings demonstrate anew pyrazine generation mechanism in the dipeptide Maillard reaction.

PRACTICAL APPLICATION

We found that a dipeptide Maillard reaction system generated more pyrazines than a reaction system composed of free amino acids. New cross-linked peptide-sugar compounds were identified and found to impact the formation of pyrazines. The results of this study may help in the preparation of thermal reaction flavors using enzymatically hydrolyzed vegetable/animal proteins, which contain a considerable amount of peptides, as one of the major reactants.

The quantification of free Amadori compounds and amino acids allows to model the bound Maillard reaction products formation in soybean products

The quantification of protein bound Maillard reaction products (MRPs) is still a challenge in food chemistry. Protein hydrolysis is the bottleneck step: it is time consuming and the protein degradation is not always complete. In this study, the quantitation of free amino acids and Amadori products (APs) was compared to the percentage of blocked lysine by using chemometric tools. Eighty thermally treated soybean samples were analyzed by mass spectrometry to measure the concentration of free amino acids, free APs and the protein-bound markers of the Maillard reaction (furosine, Nε-(carboxymethyl)-l-lysine, Nε-(carboxyethyl)-l-lysine, total lysine). Results demonstrated that Discriminant Analysis (DA) and Correlated Component Regression (CCR) correctly estimated the percent of blocked lysine in a validation and prediction set. These findings indicate that the measure of free markers reflects the extent of protein damage in soybean samples and it suggests the possibility to obtain rapid information on the quality of the industrial processes.

Measurement of Fructose-Asparagine Concentrations in Human and Animal Foods

The food-borne bacterial pathogen, Salmonella enterica, can utilize fructose-asparagine (F-Asn) as its sole carbon and nitrogen source. F-Asn is the product of an Amadori rearrangement following the nonenzymatic condensation of glucose and asparagine. Heating converts F-Asn via complex Maillard reactions to a variety of molecules that contribute to the color, taste, and aroma of heated foods. Among these end derivatives is acrylamide, which is present in some foods, especially in fried potatoes. The F-Asn utilization pathway in Salmonella, specifically FraB, is a potential drug target because inhibition of this enzyme would lead to intoxication of Salmonella in the presence of F-Asn. However, F-Asn would need to be packaged with the FraB inhibitor or available in human foods. To determine if there are foods that have sufficient F-Asn, we measured F-Asn concentrations in a variety of human and animal foods. The 400 pmol/mg F-Asn found in mouse chow is sufficient to intoxicate a Salmonella fraB mutant in mouse models of salmonellosis, and several human foods were found to have F-Asn at this level or higher (fresh apricots, lettuce, asparagus, and canned peaches). Much higher concentrations (11 000-35 000 pmol/mg dry weight) were found in heat-dried apricots, apples, and asparagus. This report reveals possible origins of F-Asn as a nutrient source for Salmonella and identifies foods that could be used together with a FraB inhibitor as a therapeutic agent for Salmonella.

Evaluation of the extent of initial Maillard reaction during cooking some vegetables by direct measurement of the Amadori compounds

BACKGROUND

During vegetable cooking, one of the most notable and common chemical reactions is the Maillard reaction, which occurs as a result of thermal treatment and dehydration. Amadori compound determination provides a very sensitive indicator for early detection of quality changes caused by the Maillard reaction, as well as to retrospectively assess the heat treatment or storage conditions to which the product has been subjected. In this paper, a hydrophilic interaction liquid chromatographic-electrospray ionization-tandem mass spectrometric method was developed for the analysis of eight Amadori compounds, and the initial steps of the Maillard reaction during cooking (steaming, frying and baking) bell pepper, red pepper, yellow onion, purple onion, tomato and carrot were also assessed by quantitative determination of these Amadori compounds.

RESULTS

These culinary treatments reduced moisture and increased the total content of Amadori compounds, which was not dependent on the type of vegetable or cooking method. Moreover, the effect of steaming on Amadori compound content and water loss was less than that by baking and frying vegetables. Further studies showed that the combination of high temperature and short time may lead to lower formation of Amadori compounds when baking vegetables.

CONCLUSION

Culinary methods differently affected the extent of initial Maillard reaction when vegetables were made into home-cooked products. © 2017 Society of Chemical Industry.

Sodium sulfite pH-buffering effect for improved xylose-phenylalanine conversion to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine during an aqueous Maillard reaction

The yield of the Maillard reaction intermediate (MRI), prepared in aqueous medium, is usually unsatisfactory. However, the addition of sodium sulfite could improve the conversion of xylose-phenylalanine (Xyl-Phe) to the MRI (N-(1-deoxy-d-xylulos-1-yl)-phenylalanine) in aqueous medium. Sodium sulfite (Na₂SO₃) showed a significant pH-buffering effect during the Maillard reaction, which accounted for its facilitation of the N-(1-deoxy-d-xylulos-1-yl)-phenylalanine yield. The results revealed that the pH could be maintained at a relatively high level (above 7.0) for an optimized pH-buffering effect when Na₂SO₃ (4.0%) was added before the reaction of Xyl-Phe. Thus, the conversion of Xyl-Phe to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine increased from 47.23% to 74.86%. Furthermore, the addition moment of Na₂SO₃ and corresponding solution pH were crucial factors in regulating the pH-buffering effect of Na₂SO₃ on N-(1-deoxy-d-xylulos-1-yl)-phenylalanine yield. Based on the pH-buffering effect of Na₂SO₃ and maintaining the optimal pH 7.4 relatively stable, the conversion of Xyl-Phe to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine was successfully improved.

Simultaneous quantification of twenty Amadori products in soy sauce using liquid chromatography-tandem mass spectrometry

A liquid chromatography-tandem mass spectrometry method using a pentafluorophenylpropyl-bonded silica column was developed to simultaneously quantify twenty Amadori products (APs), including N-(1-Deoxy-d-fructosyl-1-yl)-l-isoleucine (Fru-Ile) and N-(1-Deoxy-d-fructosyl-1-yl)-l-leucine (Fru-Leu), in soy sauce, without the need for an ion-pairing reagent or sample derivatization. The method was applied to six types of soy sauce, to determine the total AP levels and the levels of individual APs. The level of total APs widely varied between the eight samples, from 358mg/L to 24347mg/L. The concentrations of N-ε-(1-deoxy-d-fructosyl-1-yl)-l-lysine (Fru-Lys) and N-(1-deoxy-d-fructosyl-1-yl)-l-pyroglutamic acid (Fru-pGlu) were the highest among the APs and the level of Fru-pGlu was similar to that of Fru-Lys. Furthermore, fermentation periods of up to six months greatly influenced AP levels in soy sauce but the levels remained constant thereafter. Thermal treatment of soy sauce had little effect on AP levels.

Simultaneous quantification of ten Amadori compounds in tobacco using liquid chromatography with tandem mass spectrometry

Amadori compounds are aroma precursors formed in the initial phase of the Maillard reaction. Based on their similar structures, simultaneous quantification of more than six Amadori compounds in tobacco has not been reported yet. In this study, a simple and rapid method was developed to simultaneously quantify ten Amadori compounds including the isomers of Fructose-isoleucine and Fructose-leucine in tobacco. The separation was performed on an Atlantis T3 column (2.1 × 250 mm, 5 μm) by gradient elution using acetonitrile and water as the mobile phases. The quantification method was systematically evaluated and proven to be sensitive and accurate. The linearity was good, with correlation coefficients of 0.9977-0.9999. The limits of detection and quantitation were 1.354-2.532 and 4.516-8.444 ng/mL, respectively. The recoveries were 84.0-119.6%, and the relative standard deviations were 1.33-5.40%. The method was used to analyze the changes in the amounts of ten Amadori compounds in tobacco before and after tobacco primary processing. The analysis shows that the Maillard reaction occurs during the short processing period.

Free and Protein-Bound Maillard Reaction Products in Beer: Method Development and a Survey of Different Beer Types

The Maillard reaction is important for beer color and flavor, but little is known about the occurrence of individual glycated amino acids in beer. Therefore, seven Maillard reaction products (MRPs), namely, fructosyllysine, maltulosyllysine, pyrraline, formyline, maltosine, MG-H1, and argpyrimidine, were synthesized and quantitated in different types of beer (Pilsner, dark, bock, wheat, and nonalcoholic beers) by HPLC-ESI-MS/MS in the multiple reaction monitoring mode through application of the standard addition method. Free MRPs were analyzed directly. A high molecular weight fraction was isolated by dialysis and hydrolyzed enzymatically prior to analysis. Maltulosyllysine was quantitated for the first time in food. The most important free MRPs in beer are fructosyllysine (6.8-27.0 mg/L) and maltulosyllysine (3.7-21.8 mg/L). Beer contains comparatively high amounts of late-stage free MRPs such as pyrraline (0.2-1.6 mg/L) and MG-H1 (0.3-2.5 mg/L). Minor amounts of formyline (4-230 μg/L), maltosine (6-56 μg/L), and argpyrimidine (0.1-4.1 μg/L) were quantitated. Maltulosyllysine was the most significant protein-bound MRP, but both maltulosyllysine and fructosyllysine represent only 15-60% of the total protein-bound lysine-derived Amadori products. Differences in the patterns of protein-bound and free individual MRPs and the ratios between them were identified, which indicate differences in their chemical, biochemical, and microbiological stabilities during the brewing process.

Fructosyl-Valine Orally Administrated to Chickens is Absorbed from Gastrointestinal Tract

Amadori products are non-enzymatically formed by binding carbonyl groups and amino groups. Glycated amino acids generated by reacting amino acid and glucose are also in a group of Amadori products of which the transport and metabolism have been investigated mainly in mammals but not in avians. In the present study, therefore, we examined whether dietary fructosyl-valine, which is one of the glycated amino acids, orally administrated to chickens can be incorporated into blood or not. Fructosyl-valine was orally administrated to the chicken and blood samples were collected at 0, 20, 40, 60, 120 and 180 min after administration. Plasma concentration of fructosyl-valine was measured by using LC/MS. The plasma concentration of fructosyl-valine was increased by passing time from 0 to 180 min after administration, and no change was observed in the control group. Conclusively, it was clarified that fructosyl-valine orally administrated to the chicken could be absorbed from gastrointestinal tract and incorporated into blood.

Enhanced Approaches for Identifying Amadori Products: Application to Peanut Allergens

The dry roasting of peanuts is suggested to influence allergic sensitization as a result of the formation of advanced glycation end products (AGEs) on peanut proteins. Identifying AGEs is technically challenging. The AGEs of a peanut allergen were probed with nano-scale liquid chromatography-electrospray ionization-mass spectrometry (nanoLC-ESI-MS) and tandem mass spectrometry (MS/MS) analyses. Amadori product ions matched to expected peptides and yielded fragments that included a loss of three waters and HCHO. As a result of the paucity of b and y ions in the MS/MS spectrum, standard search algorithms do not perform well. Reactions with isotopically labeled sugars confirmed that the peptides contained Amadori products. An algorithm was developed on the basis of information content (Shannon entropy) and the loss of water and HCHO. Results with test data show that the algorithm finds the correct spectra with high precision, reducing the time needed to manually inspect data. Computational and technical improvements allowed for better identification of the chemical differences between modified and unmodified proteins.

Metabolite Profiling of Italian Tomato Landraces with Different Fruit Types

Increased interest toward traditional tomato varieties is fueled by the need to rescue desirable organoleptic traits and to improve the quality of fresh and processed tomatoes in the market. In addition, the phenotypic and genetic variation preserved in tomato landraces represents a means to understand the genetic basis of traits related to health and organoleptic aspects and improve them in modern varieties. To establish a framework for this approach, we studied the content of several metabolites in a panel of Italian tomato landraces categorized into three broad fruit type classes (flattened/ribbed, pear/oxheart, round/elongate). Three modern hybrids, corresponding to the three fruit shape typologies, were included as reference. Red ripe fruits were morphologically characterized and biochemically analyzed for their content in glycoalkaloids, phenols, amino acids, and Amadori products. The round/elongate types showed a higher content in glycoalkaloids, whereas flattened types had higher levels of phenolic compounds. Flattened tomatoes were also rich in total amino acids and in particular in glutamic acid. Multivariate analysis of amino acid content clearly separated the three classes of fruit types. Making allowance of the very low number of genotypes, phenotype-marker relationships were analyzed after retrieving single nucleotide polymorphisms (SNPs) among the landraces available in the literature. Sixty-six markers were significantly associated with the studied traits. The positions of several of these SNPs showed correspondence with already described genomic regions and QTLs supporting the reliability of the association. Overall the data indicated that significant changes in quality-related metabolites occur depending on the genetic background in traditional tomato germplasm, frequently according to specific fruit shape categories. Such a variability is suitable to harness association mapping for metabolic quality traits using this germplasm as an experimental population, paving the way for investigating their genetic/molecular basis, and facilitating breeding for quality-related compounds in tomato fruits.