Formation and elimination of pyrraline in the Maillard reaction in a saccharide-lysine model system

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.

Effect of milk fat and its main fatty acids on oxidation and glycation level of milk

Milk is a highly nutritional food rich in protein and fat that is prone to deterioration by oxidation and glycation reactions at storage and processing. In this study, glycation products and lipid oxidation products contents in skim milk, whole milk, and milk fat simulation groups were determined to evaluate the effect of milk fat components on glycation at 120 °C for 60 min. The increase rate of carbonyl compound, main advanced glycation end products (AGEs) levels, and glycation sites number of α-casein and β-casein are higher in whole milk than that in skim milk, indicating that milk fat promoted protein glycation significantly. In milk fat simulation groups, oleic acid and linoleic acid (LA) were added to milk fat in skim milk proportionally, promoting the formation of glycation products; however, palmitic acid had no such effect. LA exhibited strong promotion on AGEs formation. Lipid oxidation radicals, protein carbonyl amine condensation, and carbonyl compound formation were critical factors for milk glycation, according to OPLS-DA results. Therefore, radicals of fat oxidation are speculated to trigger the early glycation, and carbonyl compounds of fat oxidation act as important intermediates of glycation, fat type, form, and its degradation rate, thus play essential roles in milk glycation.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s13197-022-05658-z.

Dietary polyphenols: regulate the advanced glycation end products-RAGE axis and the microbiota-gut-brain axis to prevent neurodegenerative diseases

Advanced glycation end products (AGEs) are formed in non-enzymatic reaction, oxidation, rearrangement and cross-linking between the active carbonyl groups of reducing sugars and the free amines of amino acids. The Maillard reaction is related to sensory characteristics in thermal processed food, while AGEs are formed in food matrix in this process. AGEs are a key link between carbonyl stress and neurodegenerative disease. AGEs can interact with receptors for AGEs (RAGE), causing oxidative stress, inflammation response and signal pathways activation related to neurodegenerative diseases. Neurodegenerative diseases are closely related to gut microbiota imbalance and intestinal inflammation. Polyphenols with multiple hydroxyl groups showed a powerful ability to scavenge ROS and capture α-dicarbonyl species, which led to the formation of mono- and di- adducts, thereby inhibiting AGEs formation. Neurodegenerative diseases can be effectively prevented by inhibiting AGEs production, and interaction with RAGEs, or regulating the microbiota-gut-brain axis. These strategies include polyphenols multifunctional effects on AGEs inhibition, RAGE-ligand interactions blocking, and regulating the abundance and diversity of gut microbiota, and intestinal inflammation alleviation to delay or prevent neurodegenerative diseases progress. It is a wise and promising strategy to supplement dietary polyphenols for preventing neurodegenerative diseases via AGEs-RAGE axis and microbiota-gut-brain axis regulation.

Sodium Ions Affect Pyrraline Formation in the Maillard Reaction With Lys-Containing Dipeptides and Tripeptides

Advanced glycation end products (AGEs) are potentially-hazardous chemical compounds, produced by the Maillard reaction between reducing sugars and Lysine side-chain amino groups in proteins. AGEs are strongly associated with diabetes, Alzheimer's disease and atherosclerosis. Pyrraline, a sugar derivative of Lysine, is a major AGE and an established marker for the presence of dietary AGEs. In this study, the effects of NaCl and different dipeptide and tripeptide structures were compared on the formation of pyrraline-containing peptides and the glucose derivative 3-deoxyglucosone in the presence of glucose and at different NaCl concentrations. The physicochemical properties (polarizability, dipole moment, molecular volume and dissociation constant) and the thermodynamic properties of the peptides were determined. The amount of the pyrraline decreased significantly in the following order of peptides (at the same concentrations): Lys-Phe > Lys-Ala > Lys-Gly; Lys-Gly-Phe > Lys-Gly-Ala > Lys-Gly-Gly. The highest levels of both pyrraline and 3-deoxyglucosone occurred at 0.2 mol/L Na⁺. Sodium ions appear to alter the intramolecular electron density and charge distribution of the peptides and facilitate the reaction by stabilizing some of the intermediates in the reaction sequence.

Quantitation of furosine, furfurals, and advanced glycation end products in milk treated with pasteurization and sterilization methods applicable in China

Pasteurization and sterilization, normally carried out in milk, can induce the Maillard reaction, which can produce substances that are harmful to health. Quantitation of initial, intermediate, and advanced Maillard reaction products in milk was conducted for pasteurization (low-temperature long-time [LTLT], high-temperature short-time [HTST]) and sterilization (ultra-high temperature [UHT], in-bottle sterilization [BS]) methods. Total lysine and lactose decreased by 32.8% and 6.7% in BS milk, respectively. The generation of furosine in sterilized milk and pasteurized milk ranged from 2.5- to 5.0-fold and 1.4- to 2.8-fold higher, respectively, than those in raw milk. 5-(Hydroxymethyl)furfural increased by 4.7- and 8.4-fold in UHT and BS milk, and 2-furaldehyde (F) was not quantified in raw and LTLT milk. The concentrations of Nε-(carboxymethyl)lysine (CML) was nearly 4.4- to 6.7-fold higher than that of Nε-(carboxyethyl)lysine in the heated milk samples. CML in UHT and BS milk were around 1.4-fold and 1.6-fold higher than that in raw milk, respectively. The concentration of these Maillard reaction products in sterilized milk was significantly higher than those in raw, LTLT, and HTST milk. The results of this study could improve safety control in the dairy industry with respect to pasteurization and sterilization procedures.

Comparison of Free and Bound Advanced Glycation End Products in Food: A Review on the Possible Influence on Human Health

Debate on the hazards of advanced glycation end products (AGEs) in food has continued for many years as a result of their uncertain bioavailability and ability to bind to their receptors (RAGEs) in vivo. There are increasing evidence that free and bound AGEs have many differences in gastrointestinal digestion, intestinal absorption, binding with RAGEs, in vivo circulation, and renal clearance. Therefore, this paper compares these aspects between free and bound AGEs by summarizing the available knowledge. On the basis of the current knowledge, we conclude that it is time to differentiate free AGEs from bound AGEs in food in future studies, because they vary in many aspects that are closely related to their influence on human health. Several perspectives were proposed at the end of this review for further exploring the difference between free and bound AGEs in food.

Pyrraline Formation Modulated by Sodium Chloride and Controlled by Encapsulation with Different Coating Materials in the Maillard Reaction

Advanced glycation end products (AGEs), which are present in heat-processed foods, have been associated with several chronic diseases. Sodium chloride (NaCl) modulates the formation of furfurals and acrylamide in the Maillard reaction; however, the effects of NaCl on AGE formation are inconsistent. In this study, we investigated the effects of NaCl on pyrraline formation using glucose-lysine model systems. NaCl, especially at 0.50%, promoted Maillard browning and pyrraline formation, with a simultaneous increase in the 3-deoxyglucosone concentration. To reduce the rate of pyrraline formation, NaCl coated with different gums and starches were used. The results showed that NaCl encapsulation is an effective approach to mitigate pyrraline and 3-deoxyglucosone formation. The content of NaCl in the microparticles were 284 ± 12, 269 ± 6, 258 ± 8, 247 ± 10, 273 ± 16, and 288 ± 15 mg/g (coated with waxy maize starch, normal maize starch, HYLON VII high amylose maize starch, gelatinized resistant starch, xanthan gum, and gum arabic, respectively). The heat resistance of the coating material was negatively correlated with the pyrraline and 3-deoxyglucosone formation, whereas the solubility of the coating material had the opposite results. Coating the material with gum had little effects on the reduction of pyrraline and 3-deoxyglucosone.

d-Ribose contributes to the glycation of serum protein

d-Ribose is active in glycation and rapidly produces advanced glycation end products, leading to cell death and to cognitive impairment in mice. Glycated serum protein (GSP) is a relatively short-term biomarker for glycemic control in diabetes mellitus. However, whether d-ribose is related to GSP is unclear. The aim of this work was to identify the contribution of d-ribose to GSP compared to d-glucose. Here, we showed that the yield of glycated human serum albumin with d-ribose was at least two-fold higher than that with d-glucose in a 2-week incubation. The glycation of human serum albumin (HSA) with d-ribose was much faster than that with d-glucose, as determined by monitoring changes in the fluorescent intensity of glycation products with time. Liquid chromatography-mass spectrometry/mass spectrometry revealed that 17 and 7 lysine residues on HSA were glycated in the presence of d-ribose and d-glucose, respectively, even when the concentration ratio [d-ribose]/[d-glucose] was 1/50. The intraperitoneal injection of d-ribose significantly increased the GSP levels in Sprague Dawley rats, but the injection of d-glucose did not. The level of d-ribose was more positively associated with GSP than the level of d-glucose in streptozotocin-treated rats. In diabetic patients, the levels of both d-ribose and d-glucose were closely related to the level of GSP. Together, these in vitro and in vivo findings indicated that d-ribose is an important contributor to the glycation of serum protein, compared to d-glucose. To assess GSP levels in diabetes mellitus, we should consider the contribution from d-ribose, which plays a nonnegligible role.

Effect of fatty acids and triglycerides on the formation of lysine-derived advanced glycation end-products in model systems exposed to frying temperature

Lysine-derived advanced glycation end-products (AGEs), including N^ε-carboxymethyllysine (CML), N^ε-carboxyethyllysine (CEL) and pyrraline, are prevalent in processed foods. The impact of lipids on AGE formation is still contentious and most of our current knowledge is based only on CML. Little is known about how lipids impact the formation of CEL and pyrraline, or their involvement in formation pathways. This study investigated the effect of lipids (fatty acids and triglycerides) on the formation of CML, CEL and pyrraline simultaneously in model systems subjected to frying temperature. The results showed the presence of the lipids promoted the formation of CML, CEL and pyrraline. The promotion effects on CML and CEL were not dependent on the unsaturation degree and addition level (50, 100 or 150 μmol) of lipid, while pyrraline formation depended on lipid type (fatty acids vs. triglycerides) and level. The concentration of CML and CEL was statistically correlated with the concentration of glyoxal (GO) and methylglyoxal (MGO), respectively. The pyrraline concentration was statistically correlated with fructoselysine concentration. These results suggested that lipids promote the formation of lysine-derived AGEs by impacting the generation of Amadori products and α-dicarbonyl compounds. This information may be useful for optimizing the formulation and processing conditions to create tastier and healthier foods.

Fatty acids and triglycerides impact lysine-derived AGE formation through modulating the formation of α-dicarbonyl compounds and Amadori products.

Apparent ileal digestibility of Maillard reaction products in growing pigs

The absorption of Maillard reaction products (MRP) from dietary origin has been linked to the occurrence of chronic diseases. The aim of the present study was to determine the effects of toasting time of rapeseed meal (RSM) and the processing method of the diets (pelleting and extrusion) that included RSM on the apparent ileal digestibility (AID) of total lysine, fructosyl-lysine (FL), carboxymethyl-lysine (CML), carboxyethyl-lysine (CEL), lanthionine (LAN) and lysinoalanine (LAL) in growing pigs. The study consisted of a 2×3 factorial design with toasting time of RSM (60, 120 min) and diet processing method (mash, pelleted, extruded) as factors. Fifty growing pigs were individually fed one of the experimental diets for 4.5 consecutive days. Following euthanasia, samples of digesta were collected from the terminal 1.5 m of the small intestine. Increasing the toasting time of RSM increased the contents of FL, CML and CEL, whereas the additional effects of the diet processing methods were relatively small. Lysinoalanine and lanthionine were not detected in the diets; therefore, digestibility of these compounds could not be determined. The contents of FL, CML and CEL in the ileal chyme were positively correlated to their contents in the diets. The AID of the MRP from thermally-treated RSM were overall low and were not related to their contents in the diets. The AID of FL ranged between -8.5 and 19.1%, whilst AID of CML and CEL ranged from -0.2 to 18.3 and 3.6 to 30%, respectively. In conclusion, thermal treatments have clear effects on the contents of MRP in the diets. These compounds have relatively low digestibility in growing pigs.

Review of pentosidine and pyrraline in food and chemical models: formation, potential risks and determination

Pyrraline and pentosidine are advanced Maillard reaction products derived from the reaction of glucose with the lysine amino group on proteins. They have been implicated in uremia, diabetes, and related complications, including inflammation, retinopathy, and nephropathy. This review focuses on the formation mechanism, human potential risks, and detections of pentosidine and pyrraline and lays the foundation for further study of pentosidine and pyrraline. © 2017 Society of Chemical Industry.

Kinetic Study on Peptide-Bound Pyrraline Formation and Elimination in the Maillard Reaction Using Single- and Multiple-Response Models

Pyrraline, an advanced glycation end product (AGE), is related to some chronic diseases and can be employed as an indicator for heat damage in food processing. In this study, the impact of changing the reactant concentration and ratio on the kinetic parameters describing peptide-bound pyrraline (pep-pyr) formation and elimination was evaluated in the Lys-Gly/glucose model systems, with microwave heating treatment ranging from 120 to 200 °C. The maximum pep-pyr concentration increased as follows: 200 °C ˂ 180 °C ˂ 160 °C ˂ 120 °C ˂ 140 °C. First, the pep-pyr formation and elimination was modeled by using a single-response modelling. The formation rate constant (k_F ) of pep-pyr was independent of the initial concentration of the reactants and ratios. However, the elimination rate constant of pep-pyr (k_E ) increased with increasing reactant concentrations. Second, a multiresponse modelling was performed to illustrate the pathways of pep-pyr formation and elimination. Two adapted models can fit to the experimental data with the goodness-of-fit ranging from 0.663 to 0.920. Glucose-to-fructose isomerization rather than glucose-to-mannose epimerization was detected in an equimolar model system and the model system with an excess of any of the reactants. The caramelization reaction was negligible in the equimolar systems and the model systems with an excess of peptide. The reaction rate constant of glucose-to-fructose isomerization was independent of the initial reactant ratios. It was more difficult for pep-pyr elimination in the model system with an excess of peptide than that in the other 2 model systems (the equimolar system and the system with an excess of glucose), whereas a reverse result in pep-pyr formation was obtained.

Formation of Peptide Bound Pyrraline in the Maillard Model Systems with Different Lys-Containing Dipeptides and Tripeptides

Peptide-bound advanced glycation end-products (peptide-bound AGEs) can be formed when peptides are heated with reducing saccharides. Pyrraline is the one of most commonly studied AGEs in foods, but the relative importance of the precursor peptide structure is uncertain. In the present study, model systems were prepared by heating peptides with glucose from 60 °C to 220 °C for up to 65 min, and the amounts of peptide-bound pyrraline formed were monitored to evaluate the effect of the neighboring amino acids on the peptide-bound pyrraline formation. The physico-chemical properties were introduced to explore the quantitative structure-reactivity relationships between physicochemical properties and peptide bound formation. 3-DG content in dipeptide-glucose model system was higher than that in the corresponding tripeptide-glucose model systems. Dipeptides produced higher amounts of peptide-bound pyrraline than the corresponding tripeptides. The peptide-bound pyrraline and 3-DG production were influenced by the physico-chemical properties of the side chain of amino acids adjacent to Lys in the following order: Lys-Leu/glucose > Lys-Ile/glucose > Lys-Val/ glucose > Lys-Thr/glucose > Lys-Ser/glucose > Lys-Ala/ glucose > Lys-Gly/glucose; Lys-Leu-Gly/glucose > Lys-Ile-Gly/glucose > Lys-Val-Gly/glucose > Lys-Thr-Gly/glucose > Lys-Ser-Gly/glucose > Lys-Ala-Gly/glucose > Lys-Gly-Gly/glucose. For the side chain of amino acids adjacent to Lys in dipeptides, residue volume, polarizability, molecular volume and localized electrical effect were positively related to the yield of peptide bound pyrraline, while hydrophobicity and pK_b were negatively related to the yield of peptide bound pyrraline. In terms of side chain of amino acid adjacent to Lys in tripeptides, a similar result was observed, except hydrophobicity was positively related to the yield of peptide bound pyrraline.