α-Dicarbonyl compounds in food products: Comprehensively understanding their occurrence, analysis, and control

Formation of amino acid-based imidazole salts considerably increased the determined level of fluorescent advanced glycation end products in biscuits

Glycine, serine, and γ-aminobutyric acid are effective scavengers of reactive carbonyl species and should inhibit the formation of advanced glycation end products (AGEs). However, here we found that amino acids unexpectedly increased the intensity of fluorescent AGEs in biscuits. This study aimed to elucidate these contradictory findings and highlight concerns regarding the determination of fluorescent AGEs in foods. In gliadin-methylglyoxal (MGO) glycation model, amino acids were found to induce formaldehyde formation from MGO. Thereafter, formaldehyde and MGO reacted with the amino acids to generate imidazole salts. The imidazole salts exhibited broad fluorescence range, overlapping with the fluorescence range used to determine fluorescent AGEs in foods, thus resulting in an apparent increase in fluorescent AGEs content after amino acid addition. Since amino acids are ubiquitous in food materials, the formation of imidazole salts during food processing may result in an overestimation of fluorescent AGEs in foods.

Lipid-involved browning mechanism during the drying process of squid

The present study evaluated lipid-involved browning mechanism during the drying process of squid. Initially, different lipid-Maillard reaction (MR) models were conducted based on the composition of squid (lipids, reducing sugars and amino acids). The degree of MR as well as α-dicarbonyl compounds (α-DCs) and lipid oxidation-mediated browning products (pyrroles and lipofuscin-like pigments) were detected. The results indicated that arginine and ribose were blamed for the browning of dried squid. Moreover, lipid oxidation provided glyoxal and methylglyoxal to participate in MR, and long-time heating and salting produced more α-DCs and accelerated browning. Meanwhile, dried squid contained hydrophilic pyrrole (17.45 μg/g lipid) and hydrophobic pyrrole (113.00 μg/g lipid), and the content of lipofuscin-like pigments increased by 1.5-fold after drying. Finally, defatting treatment demonstrated that the browning of dried squid was moderately alleviated by fat removal (L* ↑, a* ↓ and b* ↓). These findings offer a novel perspective on moderately preventing the browning of dried aquatic products.

Multi-response kinetic study of Maillard reaction hazards in the glucose-lysine model system

BACKGROUND

Nε-carboxymethyllysine (CML), Nε-carboxyethyllysine (CEL) and α-aminoadipic acid (AAA) are important foodborne hazards and their intake can cause a variety of diseases in humans. It is extremely important to investigate the formation mechanism of CML, CEL and AAA, as well as their association with each other when aiming to control their production.

RESULTS

A multi-response kinetic model was developed within the glucose-lysine Maillard reaction model system. The concentrations of glucose, lysine, glyoxal (GO), methylglyoxal (MGO), CML, CEL and AAA were quantified at different temperature (100-160 °C) and at different intervals (0-60 min). The experimental data were fitted to the proposed model to calculate kinetic parameters for the corresponding steps. The results indicated that the production of CML was primarily relied on the direct oxidative cleavage of the Amadori product, rather than the reaction between GO and Lys, whereas CEL and AAA were generated through the reaction of MGO with Lys. Significantly, the reaction between α-dicarbonyl compounds and Lys preferentially generated CML and CEL, resulting in the lower concentrations of AAA compared to CML and CEL.

CONCLUSION

The multi-response kinetic model developed in the present study can be applied well to the Maillard reaction. The relationship between the formation mechanisms of CML, CEL and AAA is also explained. © 2024 Society of Chemical Industry.

Effects of saccharide type and extended heating on the Maillard reaction and physicochemical properties of high-solid gelatin gels

This research delves into the Maillard reaction (MR) in high-solid gelatin-saccharide mixtures consisting of 8% and 72% of allulose, fructose, or fructo-oligosaccharides, which were subjected to varied duration (0-60min) of thermal processing prior to gelation. Physicochemical properties of the gels, including color, chemical composition, protein crosslinking, mechanical strength, in-vitro digestibility and antioxidant activities, were characterized. At pH ∼5.5 and intermediate water activities (0.6-0.7), fast browning was observed through sugar degradation and sugar-amine interactions, which were intensified by prolonged heating. The MR reactivity of saccharides followed: AL > FRU > FOS. Characteristic products (MRPs, e.g., α-dicarbonyls, 5-hydroxymethylfurfural, and advanced glycation end products) were identified, with the spectra of MRPs varying significantly between monosaccharides and oligosaccharides. The MR-induced protein glycation and crosslinking exhibited certain negative impacts on the gel strength and in-vitro protein digestibility. Furthermore, all gelatin-saccharide mixtures exhibited augmented antioxidant properties, with the gelatin-AL mixtures displaying the highest free radical scavenging rates.

Enhancing bread anti-staling with glucose-derived Maillard reaction products: In-depth analysis of starches, gluten networks, and moisture status

In this study, six types of amino acids (Ala, Phe, Glu, Gly, Ser, and Lys) were combined with glucose to produce Maillard reaction products (MRPs) named G-Ala, G-Phe, G-Glu, G-Gly, G-Ser and G-Lys. The effect of MRPs on bread staling was evaluated through texture and sensory analyses during storage. Furthermore, the study comprehensively analyzed the anti-staling mechanisms of MRPs by examining moisture content, starches, and gluten network changes. The results indicated that G-Gly and G-Glu delayed bread staling, with G-Gly showing the most significant effect. Compared with control, the staling rate and starch crystallinity of G-Gly bread decreased by 24.07% and 7.70%, respectively. Moreover, G-Gly increased the moisture content (3.48%), weakly bound water mobility (0.77%), and α-helix content (1.00%) of bread. Component identification and partial least squares regression further confirmed the aldonic acid, heterocyclic acids and heterocyclic ketones in MRPs inhibit water evaporation, gluten network loosening, and starch degradation, thereby delaying bread staling.

The Maillard reactions: Pathways, consequences, and control

The century old Maillard reactions continue to draw the interest of researchers in the fields of Food Science and Technology, and Health and Medical Sciences. This chapter seeks to simplify and update this highly complicated, multifaceted topic. The simple nucleophilic attack of an amine onto a carbonyl group gives rise to a series of parallel and subsequent reactions, occurring simultaneously, resulting into a vast array of low and high mass compounds. Recent research has focused on: (1) the formation and transformation of α-dicarbonyl compounds, highly reactive intermediates which are essential in the development of the desired color and flavor of foods, but also lead to the production of the detrimental advanced glycation end products (AGEs); (2) elucidation of the structures of melanoidins in different foods and their beneficial effects on human health; and (3) harmful effects of AGEs on human health. Considering that MRs have both positive and negative consequences, their control to accentuate the former and to mitigate the latter, is also being conscientiously investigated with the use of modern techniques and technology.

Advances of nanoparticle derived from food in the control of α-dicarbonyl compounds-A review

α-Dicarbonyl compounds (α-DCs) are predominantly generated through the thermal processing of carbohydrate and protein-rich food. They are pivotal precursors to hazard formation, such as advanced glycation end products (AGEs), acrylamide, and furan. Their accumulation within the body will be genotoxicity and neurotoxicity. Recently, significant advancements have been made in nanotechnology, leading to the widespread utilization of nanomaterials as functional components in addressing the detrimental impact of α-DCs. This review focuses on the control of α-DCs through the utilization of nanoparticle-based functional factors, which were prepared by using edible components as resources. Four emerging nanoparticles are introduced including phenolic compounds-derived nanoparticle, plant-derived nanoparticle, active peptides-derived nanoparticle, and functional minerals-derived nanoparticle. The general control mechanisms as well as the recent evidence pertaining to the aforementioned aspects were also discussed, hoping to valuable helpful references for the development of innovative α-DCs scavengers and identifying the further scope of research.

A Ratiometric Molecularly Imprinted Sensor for Visual Detection and Removal of α-Dicarbonyl Compounds Based on Biomass Carbon Dot-Embedded Fluorescent Covalent Organic Frameworks

α-Dicarbonyl compounds (α-DCs) are important intermediate products during the thermal processing of foods and are closely related to the development of chronic diseases in the human body. However, there remains a significant gap in the availability of rapid detection methods for α-DCs. So, the ratiometric molecularly imprinted polymers (RCDs@GCOFs@MIPs) based on red-emitting biomass carbon dots (RCDs) and green-emitting fluorescent covalent organic frameworks (GCOFs) were constructed for the detection and removal of α-DCs in food processing. The ratiometric fluorescent sensors exhibited satisfactory detection and had good spiking recoveries in milk samples. And the excellent inhibition of pyrraline (PRL) by ratiometric fluorescent sensors was verified by simulating the milk pasteurization process. In addition, rapid onsite detection of α-DCs was achieved by recognizing the RGB value of the ratiometric fluorescence sensors via the smartphone. The ratiometric fluorescence sensors presented a new strategy for detecting and removing hazardous substances in food processing.

Investigations of Major α-Dicarbonyl Content in U.S. Honey of Different Geographical Origins

α-Dicarbonyls are significant degradation products resulting from the Maillard reaction during food processing. Their presence in foods can indicate the extent of heat exposure, processing treatments, and storage conditions. Moreover, they may be useful in providing insights into the potential antibacterial and antioxidant activity of U.S. honey. Despite their importance, the occurrence of α-dicarbonyls in honey produced in the United States has not been extensively studied. This study aims to assess the concentrations of α-dicarbonyls in honey samples from different regions across the United States. The identification and quantification of α-dicarbonyls were conducted using reverse-phase liquid chromatography after derivatization with o-phenylenediamine (OPD) and detected using ultraviolet (UV) and mass spectrometry methods. This study investigated the effects of pH, color, and derivatization reagent on the presence of α-dicarbonyls in honey. The quantification method was validated by estimating the linearity, precision, recovery, method limit of detection, and quantification using known standards for GO, MGO, and 3-DG, respectively. Three major OPD-derivatized α-dicarbonyls including methylglyoxal (MGO), glyoxal (GO), and 3-deoxyglucosone (3-DG), were quantified in all the honey samples. 3-Deoxyglucosone (3-DG) was identified as the predominant α-dicarbonyl in all the U.S. honey samples, with concentrations ranging from 10.80 to 50.24 mg/kg. The total α-dicarbonyl content ranged from 16.81 to 55.74 mg/kg, with the highest concentration measured for Southern California honey. Our results showed no significant correlation between the total α-dicarbonyl content and the measured pH solutions. Similarly, we found that lower amounts of the OPD reagent are optimal for efficient derivatization of MGO, GO, and 3-DG in honey. Our results also indicated that darker types of honey may contain higher α-dicarbonyl content compared with lighter ones. The method validation results yielded excellent recovery rates for 3-DG (82.5%), MGO (75.8%), and GO (67.0%). The method demonstrated high linearity with a limit of detection (LOD) and limit of quantitation (LOQ) ranging from 0.0015 to 0.002 mg/kg and 0.005 to 0.008 mg/kg, respectively. Our results provide insights into the occurrence and concentrations of α-dicarbonyl compounds in U.S. honey varieties, offering valuable information on their quality and susceptibility to thermal processing effects.

Mechanism of Dihydromyricetin-Induced Reduction of Furfural Derived from the Amadori Compound: Formation of Adducts between Dihydromyricetin and Furfural or Its Precursors

Dihydromyricetin (DMY) was employed to reduce the yield of furfural derived from the Amadori rearrangement product of l-threonine and d-xylose (Thr-ARP) by trapping Thr-ARP, 3-deoxyxyosone (3-DX), and furfural to form adducts. The effect of different concentrations of DMY at different pH values and temperatures on the reduction of furfural production was studied, and the results showed that DMY could significantly reduce furfural production at higher pH (pH 5-7) and lower temperature (110 °C). Through the surface electrostatic potential analysis by Gaussian, a significant enhancement of the C6 nucleophilic ability at higher pH (pH ≥ 5) was observed on DMY with hydrogen-dissociated phenol hydroxyl. The nucleophilic ability of DMY led to its trapping of Thr-ARP, 3-DX, and furfural with the generation of the adducts DMY-Thr-ARP, DMY-3-DX, and DMY-furfural. The formation of the DMY-Thr-ARP adduct slowed the degradation of Thr-ARP, caused the decrease of the 3-DX yield, and thereby inhibited the conversion of 3-DX to furfural. Therefore, DMY-Thr-ARP was purified, and the structure was identified by nuclear magnetic resonance (NMR). The results confirmed that C6 or C8 of DMY and carbonyl carbon in Thr-ARP underwent a nucleophilic addition reaction to form the DMY-Thr-ARP adduct. In combination with the analysis results of Gaussian, most of the DMY-Thr-ARP adducts were calculated to be C6-DMY-Thr-ARP. Furthermore, the formation of DMY-furfural caused furfural consumption. The formation of the adducts also shunted the pathway of both Thr-ARP and 3-DX conversion to furfural, resulting in a decrease in the level of furfural production.

Study on the non-enzymatic browning of lotus rhizome juice during sterilization mediated by 1,2-dicarboxyl and heterocyclic compounds

BACKGROUND

Lotus rhizome juice (LRJ) is susceptible to the Maillard reaction (MR) and caramelization, which tend to cause a reduction in quality and lower consumer acceptance of the product. 1,2-Dicarbonyl compounds (DCs) and heterocyclic compounds have attracted increasing attention as key intermediates responsible for the formation of brown pigments during MR and caramelization. However, little is known about the effects of these two types of compounds on brown pigments in LRJ during sterilization. This study quantified the changes in brown intensity (A420), DCs, and heterocyclic compounds before and after spiking, and identified the precursors and intermediates for brown pigment formation as well as the formation pathways of the intermediates.

RESULTS

The spiking experiments suggested that spiking with fructose resulted in more 3-deoxyglucosone (3-DG) and 2,3-dihydro-3,5-dihydroxy-6-methyl-4(H)-pyran-4-one (DDMP), while that with lysine led to more glucosone (GS) and 2,3-butanedione (2,3-BD) in LRJ. The addition of glucose, asparagine, and glutamine promoted the formation of 5-hydroxymethylfurfural (HMF) significantly, whereas the addition of glucose, lysine, and asparagine resulted in more norfuraneol. Spiking with reducing sugars and amino acids promoted both glyoxal (GO) and methylglyoxal (MGO), and the effect of glucose on GO was particularly significant. Correlation analysis showed that A420 had the highest correlation with 3-DG in the fructose- and lysine-spiked group, and with HMF in the glucose-, asparagine-, and glutamine-spiked groups.

CONCLUSION

This study revealed that fructose, glucose, asparagine, glutamine, and lysine were essential precursors of MR and caramelization in LRJ during sterilization. 3-Deoxyglucosone and DDMP were mainly produced by caramelization with fructose as the primary precursor, whereas GS and 2,3-BD were primarily formed via MR with lysine catalysis. The MR and caramelization were the main formation pathways of HMF (catalyzed by asparagine and glutamine) and norfuraneol (catalyzed by lysine and asparagine), with glucose as the critical precursor. Methylglyoxal was mainly produced by MR or caramelization, and caramelization was the main formation pathway of GO, with glucose as the precursor. Dor brown pigment formation from fructose and lysine, 3-DG was identified as the most crucial intermediate, while for that from glucose, asparagine, and glutamine, HMF was found to be the most important intermediate. © 2023 Society of Chemical Industry.

Advanced glycation end products of dietary origin and their association with inflammation in diabetes - A minireview

Advanced glycation end products (AGEs) are a diverse group of compounds that are formed as a result of the non-enzymatic reaction between a reducing sugar such as glucose and the free NH2 groups of an amino acid in a protein or other biomolecule. The chemical reaction, by which these products are generated, is known as the Maillard reaction and occurs as a part of the body's normal metabolism. Such a reaction is enhanced during diabetes due to hyperglycemia, but it can also occur during the preparation, processing, and preservation of certain foods. Therefore, AGEs can also be obtained from the diet (d-AGE) and contribute to an increase of the total serum pool of these compounds. They have been implicated in a wide variety of pathological processes, mainly because of their ability to induce inflammatory responses and oxidative stress increase. They are extensively accumulated as a part of the normal aging, especially in tissues rich in long half-life proteins, which can compromise the physiology of these tissues. d-AGEs are abundant in diets rich in processed fats and sugars. This review is addressed to the current knowledge on these products and their impact on the immunomodulation of various mechanisms that may contribute to exacerbation of the diabetes pathophysiology.

Investigation of Advanced Glycation End-Products, α-Dicarbonyl Compounds, and Their Correlations with Chemical Composition and Salt Levels in Commercial Fish Products

The contents of free and protein-bound advanced glycation end-products (AGEs) including Nε-carboxymethyllysine (CML) and Nε-carboxyethyllysine (CEL), along with glyoxal (GO), methylglyoxal (MGO), chemical components, and salt in commercially prepared and prefabricated fish products were analyzed. Snack food classified as commercially prepared products exhibited higher levels of GO (25.00 ± 3.34-137.12 ± 25.87 mg/kg of dry matter) and MGO (11.47 ± 1.39-43.23 ± 7.91 mg/kg of dry matter). Variations in the contents of free CML and CEL increased 29.9- and 73.0-fold, respectively. Protein-bound CML and CEL in commercially prepared samples were higher than those in raw prefabricated ones due to the impact of heat treatment. Levels of GO and MGO demonstrated negative correlations with fat (R = -0.720 and -0.751, p < 0.05) in commercially prepared samples, whereas positive correlations were observed (R = 0.526 and 0.521, p < 0.05) in raw prefabricated ones. The heat-induced formation of protein-bound CML and CEL showed a negative correlation with the variations of GO and MGO but was positively related to protein levels in prefabricated products, suggesting that GO and MGO may interact with proteins to generate AGEs during heating. The influence of NaCl on the formation of GO and MGO exhibited variations across different fish products, necessitating further investigation.

Simultaneous determination of six α-dicarbonyl compounds in traditional Chinese medicines using high-performance liquid chromatography-fluorescence detector with pre-column derivatization

A reliable method for determination of six α-dicarbonyl compounds in traditional Chinese medicines was first developed and validated by high-performance liquid chromatography-fluorescence detector with pre-column derivatization. α-Dicarbonyl compounds in traditional Chinese medicines were extracted and derivatized with 2,3-diaminaphthalene. The derivatization procedure of six α-dicarbonyl compounds was confirmed by high-resolution mass spectrometry. The limits of quantitation for six α-dicarbonyl compounds ranged from 3.70 × 10-3 to 2.21 × 10-2  μM. The established method showed good linearity (regression coefficient > 0.9990), precision (relative standard deviation < 3.37%), and high recovery (97.8%∼113.1%). The developed method was successfully applied to detect the six α-dicarbonyl compounds in traditional Chinese medicines. The result exhibited six α-dicarbonyl compounds was found in the 15 kinds of traditional Chinese medicines, which suggested us that the determination of α-dicarbonyl compounds should be paid more attention in the quality control of traditional Chinese medicines.

Chaste honey in long term-storage: Occurrence and accumulation of Maillard reaction products, and safety assessment

Honey, a natural sweetener that can be stored long-term, is prone to Maillard reactions. Maillard reaction products (MRPs), such as 5-hydroxymethylfurfural (5-HMF), α-dicarbonyl compounds (α-DCs), and advanced glycation end products (AGEs), negatively affect human health. We analyzed MRP accumulation in chaste honey over four years. In the first year, α-DCs were dominant with total contents of 509.7 mg/kg. In the second year, Amadori compounds increased, accounting for the largest percentage. Their formation at the initial stage showed inhibition of the Maillard reaction over time. AGE contents were approximately 1.00 mg/kg over four years, which is negligible compared to other foods. Increased 5-HMF was significantly correlated with storage time (p < 0.01), making it a suitable indicator of honey quality. Due to the lack of MRP risk assessments, we compared our findings with daily intake of MRPs from other foods, and the levels of MRPs in honey over four years are acceptable.