Quantitation of α-Dicarbonyls and Advanced Glycation Endproducts in Conventional and Lactose-Hydrolyzed Ultrahigh Temperature Milk during 1 Year of Storage

Effect of brewer's spent grain melanoidins on maillard reaction products during storage of whey protein model systems

Maillard reaction readily takes place in dairy products because of the association between thermal treatments, extended storage and the matrix composition. Along with the impairment of protein digestion, the formation of glycation and α-dicarbonyl compounds is a concern for quality attributes of whey proteins when used as ingredients. In this paper, we outline the capacity of brewer's spent grain melanoidins in reducing the accumulation of α-dicarbonyl compounds, thus controlling the formation of dietary advanced glycation end-products in accelerated shelf life at 35 °C. Results revealed that brewer's spent grain melanoidins targeted methylglyoxal and glyoxal reactivity leading to the reduction of N-ε-carboxymethyllysine and methylglyoxal-hydroimidazolone up to 27 and 60%, respectively. We here describe that the presence of melanoidins is instrumental in limiting the undesired effects of α-dicarbonyl compounds on whey proteins.

Contents of ɑ-dicarbonyl compounds in commercial black tea and affected by the processing

The species and contents of ɑ-dicarbonyls in commercial black tea were examined, along with the effects of the manufacturing process and drying temperature on the formation of ɑ-dicarbonyls. Ten ɑ-dicarbonyls were quantified in commercial and in-process black tea samples by using UPLC-MS/MS and their derived quinoxalines. The ɑ-dicarbonyls content in commercial black tea decreased significantly (p < 0.05) in the following order: 3-deoxyglucosone > glucosone > 3-deoxypentosone = threosone > galactosone ≥ methylglyoxal = glyoxal ≥ 3-deoxygalactosone = 3-deoxythreosone = diacetyl. Except for 3-deoxyglucosone and 3-deoxygalactosone, a further eight ɑ-dicarbonyls were identified in all manufacturing steps of black tea. Except for the drying step, the rolling and fermenting played important roles in the formation of ɑ-dicarbonyls. The total contents of ɑ-dicarbonyls in black tea infusion ranged from 16.48 to 75.32 μg/g based on our detected ten ɑ-dicarbonyls.

Influence of Pasteurization on Maillard Reaction in Lactose-Free Milk

In order to improve the safety and quality of lactose-free milk (LFM) Maillard reaction products (MRPs), this study used raw cow's milk as raw material and lactase hydrolysis to prepare LFM, which was heat-treated using pasteurization and then placed in storage temperatures of 4 °C, 25 °C and 37 °C to investigate the changes in the Maillard reaction (MR). The results of the orthogonal test showed that the optimal conditions for the hydrolysis of LFM are as follows: the hydrolysis temperature was 38 °C, the addition of lactase was 0.03%, and the hydrolysis time was 2.5 h. Under these conditions, the lactose hydrolysis rate reached 97.08%, and the lactose residue was only 0.15 g/100 g as determined by high-performance liquid chromatography (HPLC), complying with the standard of LFM in GB 28050-2011. The contents of furoamic acid and 5-hydroxymethylfurfural were determined by high-performance liquid chromatography, the color difference was determined by CR-400 color difference meter, and the internal fluorescence spectrum was determined by F-320 fluorescence spectrophotometer. The test results showed that the variation range of furosine in lactose-free milk after pasteurization was 44.56~136.45 mg/100g protein, the range of 5-hydroxymethylfurfural (HMF) was 12.51~16.83 mg/kg, the color difference ranges from 88.11 to 102.53 in L*, from -0.83 to -0.10 in a*, and from 1.88 to 5.47 in b*. The furosine content of LFM during storage at 4, 25, and 37 °C ranged from 44.56 to 167.85, 44.56 to 287.13, and 44.56 to 283.72 mg/100 g protein, respectively. The average daily increase in protein content was 1.18-3.93, 6.46-18.73, and 15.7-37.66 mg/100 g, respectively. The variation range of HMF was 12.51~17.61, 12.51~23.38, and 12.51~21.1 mg/kg, and the average daily increase content was 0.03~0.07, 0.47~0.68, and 0.51~0.97 mg/kg, respectively. During storage at 4 °C, the color difference of LFM ranged from 86.82 to 103.82, a* ranged from -1.17 to -0.04, and b* ranged from 1.47 to 5.70. At 25 °C, color difference L* ranges from 72.09 to 102.35, a* ranges from -1.60 to -0.03, b* ranges from 1.27 to 6.13, and at 37 °C, color difference L* ranges from 58.84 to 102.35, a* ranges from -2.65 to 1.66, and b* ranges from 0.54 to 5.99. The maximum fluorescence intensity (FI) of LFM varies from 131.13 to 173.97, 59.46 to 173.97, and 29.83 to 173.97 at 4, 25, and 37 °C. In order to reduce the effect of the Maillard reaction on LFM, it is recommended to pasteurize it at 70 °C-15 s and drink it as soon as possible during the shelf life within 4 °C.

Advanced Glycation End Products: A Comprehensive Review of Their Detection and Occurrence in Food

The Maillard reaction (MR) is a complicated chemical process that has been extensively studied. Harmful chemicals known as advanced glycation end products (AGEs), with complex structures and stable chemical characteristics, are created during the final stage of the MR. AGEs can be formed both during the thermal processing of food and in the human body. The number of AGEs formed in food is much higher compared to endogenous AGEs. A direct connection exists between human health and the build-up of AGEs in the body, which can result in diseases. Therefore, it is essential to understand the content of AGEs in the food we consume. The detection methods of AGEs in food are expounded upon in this review, and the advantages, disadvantages, and application fields of these detection methods are discussed in depth. Additionally, the production of AGEs in food, their content in typical foods, and the mechanisms influencing their formation are summarized. Since AGEs are closely related to the food industry and human health, it is hoped that this review will further the detection of AGEs in food so that their content can be evaluated more conveniently and accurately.

Application of Molecular Transformer approach for predicting the potential reactions to generate advanced glycation end products in infant formula

Advanced glycation end products (AGEs) are associated with the occurrence of human chronic diseases, and exist commonly in thermally processed foods, such as infant formula. Existing research mainly focuses on the discrete simulation system, which is time-consuming and challenging, but accumulates of a large amount of valuable data. This study aimed to propose a specific Molecular Transformer-based model trained on the data curated from literature to predict the chemical reaction of AGEs, and apply it to infant formula to observe which new reactions could generate AGEs. The model achieved top-3 accuracy of 76.0% on the total dataset. Based on the model prediction results, five reactions were selected for experimental verification, and four of them were consistent with the model prediction results. This prospective study might potentially revolutionize the discovery of AGEs reactions and provide theoretical guidelines for designing a safer infant formula.

Quantitation of α-Dicarbonyls, Lysine- and Arginine-Derived Advanced Glycation End Products, in Commercial Canned Meat and Seafood Products

Commercial sterilization is a thermal processing method commonly used in low-acid canned food products. Meanwhile, heat treatment can significantly promote advanced glycation end product (AGE) formation in foodstuffs. In this research, the validated analytical methods have been developed to quantitate both lysine- and arginine-derived AGEs and their precursors, α-dicarbonyls, in various types of commercial canned meat and seafood products. Methylglyoxal-hydroimidazolone 1 was the most abundant AGEs found in the canned food products, followed by Nε-(carboxyethyl)lysine, Nε-(carboxymethyl)lysine, and glyoxal-hydroimidazolone 1. Correlation analysis revealed that methylglyoxal and glyoxal were only positively associated with the corresponding arginine-derived AGEs, while their correlations with the corresponding lysine-derived AGEs were not significant. Importantly, we demonstrated for the first time that total sugar and carbohydrate contents might serve as the potential markers for the prediction of total AGEs in canned meats and seafoods. Altogether, this study provided a more complete view of AGEs' occurrence in commercial canned food products.

Research advances of advanced glycation end products in milk and dairy products: Formation, determination, control strategy and immunometabolism via gut microbiota

Advanced glycosylation end products (AGEs) are a series of complex compounds which generate in the advanced phase of Maillard reaction, which can pose a non-negligible risk to human health. This article systematically encompasses AGEs in milk and dairy products under different processing conditions, influencing factors, inhibition mechanism and levels among the different categories of dairy products. In particular, it describes the effects of various sterilization techniques on the Maillard reaction. Different processing techniques have a significant effect on AGEs content. In addition, it clearly articulates the determination methods of AGEs and even discusses its immunometabolism via gut microbiota. It is observed that the metabolism of AGEs can affect the composition of the gut microbiota, which further has an impact on intestinal function and the gut-brain axis. This research also provides a suggestion for AGEs mitigation strategies, which are beneficial to optimize the dairy production, especially innovative processing technology application.

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.

Peptidomic Fingerprints of Stored UHT Milk Inoculated with Protease Extracts from Different Pseudomonas Strains Relative to aprX Expression and Visible Spoilage

Lately, concern about the protease AprX produced by Pseudomonas has increased in the dairy industry due to its ability to survive UHT treatment and spoil UHT milk. Efficient prediction methods for UHT milk spoilage are currently lacking, mainly due to high diversity in proteolytic potential between Pseudomonas strains. The present study aimed to gain more insight into the variability between Pseudomonas strains regarding proteolytic potential by comparing their proteolytic capability with their aprX expression levels and differences in peptide formation. The variability in aprX expression levels in four Pseudomonas strains were related to physical stability, milk proteolysis and peptidomic cleavage patterns of milk proteins in a storage experiment of UHT milk inoculated with protease extracellular extracts and stored for 45 days at 20 °C. A positive relationship was observed between the relative expression of aprX and milk proteolysis during storage, with the strain Pseudomonas panacis DSM 18529 showing the highest level in both parameters. This strain was the only strain to show visual gelation, which occurred after 21 days. The peptide formation analysis showed a similar protein hydrolysis pattern between strains and high hydrolysis of αs1-caseins during long-term spoilage putatively due to the activity of AprX was observed.

Ultra-High Temperature Treatment and Storage of Infant Formula Induces Dietary Protein Modifications, Gut Dysfunction, and Inflammation in Preterm Pigs

SCOPE

Ready-to-feed liquid infant formula is increasingly used for preterm infants when human milk is unavailable. These formulas are sterilized by ultra-high temperature treatment, but heating and storage may reduce bioactivity and increase formation of Maillard reaction products with potential negative consequences for immature newborns.

METHODS AND RESULTS

Using preterm pigs as a model for sensitive newborn infants, the study tests the intestinal responses of feeding experimental liquid formula within 5 days. A pasteurized formula (PAST) with the same nutrient composition but less protein modifications serves as control to ultra-high temperature-treated formula without (UHT) and with prolonged storage (SUHT). Relative to PAST, UHT contains lower levels of lactoferrin and IgG. Additional storage (40 °C, 60 days, SUHT) reduces antimicrobial capacity and increases non-reducible protein aggregates and Maillard reaction products (up to 13-fold). Pigs fed SUHT have more diarrhea and show signs of intestinal inflammation (necrotizing enterocolitis) compared with pigs fed PAST and UHT. These clinical effects are accompanied by accumulation of Maillard reaction products, protein cross-links, and inflammatory responses in the gut.

CONCLUSION

The results demonstrate that feeding UHT infant formulas, particularly after prolonged storage, adversely affects gut maturation and function in preterm pigs used as a model of preterm infants.

Evaluation of Fructo-, Inulin-, and Galacto-Oligosaccharides on the Maillard Reaction Products in Model Systems with Whey Protein

The present study aimed to investigate the effects of fructo-, inulin-, and galacto-oligosaccharides (FOS, IOS, and GOS) on forming the Maillard reaction products such as browning, α-dicarbonyl compounds, and advanced glycation end products (AGEs). The model solutions at pH 6.8 containing each carbohydrate (mono-, di-, and oligosaccharides) and whey protein were incubated at 50 °C for 8 weeks. In the IOS model, sugars of DP3 or larger were significantly decreased at 4 weeks, whereas at 6 weeks in the FOS model. The residual amount of GOS after 8 weeks was higher than FOS and IOS; however, a large amount of 3-deoxyglucosone was formed compared to the other models. N^ε-Carboxymethyllysine (CML) concentrations in oligosaccharide models were about half of those in monosaccharide and lactose models. The highest concentrations of glyoxal- and methylglyoxal-derived hydroimidazolones 3 (G-H3 and MG-H3) were observed in the IOS model, indicating the involvement of fructose units linked by β-2 → 1 bonds. G-H3 and MG-H3 quantification could be a useful indicator to reflect the modification of an arginine residue by fructose if used acid-hydrolysis for AGE analysis. CML, G-H3, and MG-H3 were considerably formed even in the FOS model, which has no reducing terminal site, suggesting that degradation products of oligosaccharides probably participated in the formation of AGEs.

Maillard reaction products and amino acid cross-links in liquid infant formula: Effects of UHT treatment and storage

The formation of Maillard reaction products, including Amadori compounds (determined as furosine), advanced glycation end products (AGEs), α-dicarbonyl and furfural compounds, as well as amino acid cross-links (lysinoalanine and lanthionine) was investigated in direct (DI) and indirect (IN) UHT-treated experimental liquid infant formula (IF) during storage at 40 °C. IN-IF had higher concentrations of all investigated compounds compared to DI-IF and low pasteurized IF. IN UHT treatment induced significantly higher concentrations of α-dicarbonyl compounds (glyoxal, methylglyoxal, 3-deoxyglucosone and 3-deoxygalactosone) compared to DI, which facilitated increased formation of AGEs (N-Ɛ-(carboxymethyl)lysine, methylglyoxal- and glyoxal-derived hydroimidazolones) in unstored IFs. During storage for 6 months, concentrations of furosine and AGEs increased while α-dicarbonyl compounds decreased. Principal component analysis indicated that differences between IN-IF and DI-IF disappeared after 2 months of storage. IN-IF had higher concentrations of lysinoalanine and lanthionine and lower concentrations of available lysine and arginine than DI-IF indicating higher loss of protein quality in IN-IF.

Development in Maillard Reaction and Dehydroalanine Pathway Markers during Storage of UHT Milk Representing Differences in Casein Micelle Size and Sedimentation

Ultra-high temperature (UHT) processing of milk can result in protein changes during storage; however, the progress of dehydroalanine (DHA) mediated protein cross-linking and Maillard reactions in relation to the sediment formation have not been investigated previously. Liquid chromatography–mass spectrometry, based on multiple reaction monitoring (MRM), was used to absolutely quantify concentrations of furosine, N-ε-(carboxyethyl)lysine (CEL), N-ε-(carboxymethyl)lysine (CML), lanthionine (LAN) and lysinoalanine (LAL) in skim milk and sediment of UHT milk produced from raw milk with either small or large casein micelles. The results showed a higher molar proportion of the advanced stage Maillard reaction products CEL and CML in the sediment, compared to early stage Maillard reaction product furosine, whereas furosine was predominant in the skim milk. Both LAL and LAN increased during storage in the skim milk phase, however only LAL was identified in the sediment. The milk pool with large native casein micelles, known to have a higher percentage of sedimentation, contained higher proportions of furosine, CEL, CML and LAL in the sediment compared to milk with smaller native casein micelles. The study demonstrates the potential contribution of processing-induced protein-protein interactions to sedimentation in UHT milk during storage.

Effect of pectin oligosaccharides supplementation on infant formulas: The storage stability, formation and intestinal absorption of advanced glycation end products

Pectin oligosaccharides with a molecular weight greater than 700 Da was obtained from the pomace of kiwi (Actinidia arguta). Based on characteristics analysis and inhibitory activity of advanced glycation end products (AGEs) formation in vitro, the target pectin oligosaccharides was added to infant formulas and then subjected to accelerated storage. Results showed that pectin oligosaccharides supplementation inhibited the browning of infant formulas and glassy transition of lactose, and slowed down the increase of water activity under accelerated storage conditions. Pectin oligosaccharides also inhibited the formation of AGEs in infant formulas, such as 5-(hydroxymethyl)furfural, N^ε-carboxymethyl-lysine, N^ε-carboxyethyl-lysine, methylglyoxal hydromidazolones, glyoxal hydromidazolones, glyoxal-lysine dimer, methylglyoxal-lysine dimer and pyrraline. Besides, permeability studies using Caco-2 cell monolayer also showed that pectin oligosaccharides supplementation inhibited the intestinal absorption of AGEs, especially 5-(hydroxymethyl)furfural, Nε-carboxymethyl-lysine, Nε-carboxyethyl-lysine and glyoxal hydromidazolones. These results provide a reliable theoretical basis for the application of pectin oligosaccharides in infant formulas.

Effect of Processing of Whey Protein Ingredient on Maillard Reactions and Protein Structural Changes in Powdered Infant Formula

The most widely used whey protein ingredient in an infant formula (IF) is the whey protein concentrate (WPC). The processing steps used in the manufacturing of both a powdered IF and a WPC introduce protein modifications that may decrease the nutritional quality. A gently processed whey protein ingredient (serum protein concentrate; SPC) was manufactured and used for the production of a powdered IF. The SPC and the SPC-based IF were compared to the WPC and the powdered WPC-based IF. Structural protein modifications were evaluated, and Maillard reaction products, covering furosine, α-dicarbonyls, furans, and advanced glycation end products, were quantified in the IFs and their protein ingredients. IF processing was responsible for higher levels of protein modifications compared to the levels observed in the SPC and WPC. Furosine levels and aggregation were most pronounced in the WPC, but the SPC contained a high level of methylglyoxal, revealing that other processing factors should be considered in addition to thermal processing.

Carbonyl Chemistry and the Formation of Heterocyclic Aromatic Amines with the Structure of Aminoimidazoazaarene

Recent studies have shown that the formation of heterocyclic aromatic amines (HAAs) with the structure of aminoimidazoazaarene is produced by reaction of specific reactive carbonyls with ammonia and creatin(in)e. These carbonyl compounds, which are usually the limiting reagents, have multiple origins. Therefore, HAA formation cannot be considered to be produced as a consequence of a single process, such as the Maillard reaction, but of any process that generates the involved reactive carbonyls. In addition, inhibition of HAA formation should be related to the control of these reactive carbonyls: inhibiting their formation, using conditions that limit their reactivity, and promoting their trapping.

UHT treatment and storage of liquid infant formula affects protein digestion and release of bioactive peptides

Ready-to-feed liquid infant formulas (IF) were subjected to direct (D) or indirect (ID) ultra-high-temperature (UHT) treatment and then stored at 40 °C under aseptic conditions for 60-120 days simulating global transportation which accelerates the Maillard reaction. Low pasteurized and unstored IF (LP) was included as a control for the UHT treatments. Simulated infant in vitro digestion was conducted. SDS-PAGE indicated that protein aggregate formation correlated with thermal treatment, being greatest after 60 days of storage. Limited protein digestion was observed after pepsin treatment for 2 h. Beta-lactoglobulin (β-Lg), alpha-lactalbumin (α-La) and protein aggregates remained undigested after 2 h of pepsin digestion in LP and D, but less β-Lg and α-La remained in ID. The digestion of β-Lg and α-La was enhanced in D and ID stored for 60 days, but aggregates remained undigested. After pepsin and pancreatin digestion, large amounts of β-Lg remained undigested in the LP, but digestion increased after UHT treatment (ID > D) and increased further after storage for 60 and 120 days, indicating that heat treatment and storage facilitate the digestion of unaggregated proteins. No aggregates remained after pancreatin digestion of LP, D, ID and D stored for 60 days, but were present in ID stored for 60 days. Aggregates were mainly disulphide-linked, but dityrosine linkages were detected in D and ID stored for 120 days. LC-MS/MS indicated limited proteolysis arising from endogenous milk proteases prior to in vitro digestion, being highest in D. Peptide numbers increased following pepsin and further during pancreatin digestion (β-casein > β-Lg > β-La), and released β-Lg peptides, typically 5-8 amino acids in length, contained several bioactivities, e.g., dipeptidyl-peptidase IV (DPP-IV) and angiotensin converting enzyme (ACE) inhibition.

Chemical Stability of Proteins in Foods: Oxidation and the Maillard Reaction

Protein is a major nutrient present in foods along with carbohydrates and lipids. Food proteins undergo a wide range of modifications during food production, processing, and storage. In this review, we discuss two major reactions, oxidation and the Maillard reaction, involved in chemical modifications of food proteins. Protein oxidation in foods is initiated by metal-, enzyme-, or light-induced processes. Food protein oxidation results in the loss of thiol groups and the formation of protein carbonyls and specific oxidation products of cysteine, tyrosine, tryptophan, phenylalanine, and methionine residues, such as disulfides, dityrosine, kynurenine, m-tyrosine, and methionine sulfoxide. The Maillard reaction involves the reaction of nucleophilic amino acid residues with reducing sugars, which yields numerous heterogeneous compounds such as α-dicarbonyls, furans, Strecker aldehydes, advanced glycation end-products, and melanoidins. Both protein oxidation and the Maillard reaction result in the loss of essential amino acids but may positively or negatively impact food structure and flavor. Expected final online publication date for the Annual Review of Food Science and Technology, Volume 13 is March 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

Comparison of metabolic fate, target organs, and microbiota interactions of free and bound dietary advanced glycation end products

Increased intake of Western diets and ultra-processed foods is accompanied by increased intake of advanced glycation end products (AGEs). AGEs can be generated exogenously in the thermal processing of food and endogenously in the human body, which associated with various chronic diseases. In food, AGEs can be divided into free and bound forms, which differ in their bioavailability, digestion, absorption, gut microbial interactions and untargeted metabolites. We summarized the measurements and contents of free and bound AGE in foods. Moreover, the ingestion, digestion, absorption, excretion, gut microbiota interactions, and metabolites and metabolic pathways between free and bound AGEs based on animal and human studies were compared. Bound AGEs were predominant in most of the selected foods, while beer and soy sauce were rich in free AGEs. Only 10%-30% of AGEs were absorbed into the systemic circulation when orally administered. The excretion of ingested free and bound AGEs was approximately 90% and 60%, respectively. Dietary free CML has a detrimental effect on gut microbiota composition, while bound AGEs have both detrimental and beneficial impacts. Free and bound dietary AGEs changed amino acid metabolism, energy metabolism and carbohydrate metabolism. And besides, bound dietary AGEs altered vitamin metabolism, and glycerolipid metabolism.

Quantification of advanced glycation end products and amino acid cross-links in foods by high-resolution mass spectrometry: Applicability of acid hydrolysis

An analytical method was developed and validated for simultaneous identification and quantification of advanced glycation end products (AGEs), amino acid cross-links, lysine and arginine in foodstuffs based on acid hydrolysis, hydrophilic interaction chromatography and high-resolution mass spectrometry. The method proved to be sensitive, reproducible and accurate for furosine, N-Ɛ-(carboxymethyl)lysine, N-Ɛ-(carboxyethyl)lysine, methylglyoxal and glyoxal-derived hydroimidazolones (MG-H and GO-H isomers, respectively), glyoxal lysine dimer, lysinoalanine, lanthionine, lysine and arginine. LOD and LOQ values in water were found to be 0.9-15.5 ng/mL and 2.8-47 ng/mL, respectively, and increased to 1.4-60 ng/mL and 4.4-182 ng/mL in liquid infant formula. Recovery values ranged from 76 to 118% in four different food matrices. Microwave-assisted hydrolysis for 11 min had similar efficiency as conventional hydrolysis, which requires overnight incubation. Acid stability of each compound was determined during microwave and conventional hydrolysis, and showed that the MG-H1 isomer is partially converted to the MG-H3 isomer during acid hydrolysis.

New Advanced Glycation End Products Observed in Rat Urine by Untargeted Metabolomics after Feeding with Heat-Treated Skimmed Milk Powder

SCOPE

Milk powder is commonly consumed throughout the world. However, advanced glycation end products (AGEs) will form in milk powder during thermal processing and long-term storage. This study aimed to identify such compounds with potential as new urinary biomarkers of intake of heat-treated skimmed milk powder (HSMP).

METHODS AND RESULTS

A parallel study is performed with different dosages of HSMP as well as hydrolyzed HSMP and untreated skimmed milk powder (SMP) in 36 rats. The 24-h urine samples on day 7 or 8 are collected and profiled by untargeted UPLC-Qtof-MS metabolomics. Statistical analysis revealed 25 metabolites differentiating SMP and HSMP; nineteen of these structures are proposed as lysine- and arginine-derived AGEs, and heterocyclic compounds.

CONCLUSION

These metabolites may potentially serve as biomarkers of food intake pending further validation to assess intakes of heat-processed dairy foods and thus help to elucidate the effects of HSMP consumption or dietary AGEs on human health.

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.

Impact of UHT treatment and storage on liquid infant formula: Complex structural changes uncovered by centrifugal field-flow fractionation with multi-angle light scattering

Protein modifications in liquid infant formula (IF) have been widely studied, but distinguishing between heat- and storage-induced structural changes remains challenging. A generic liquid IF was subjected to direct or indirect UHT treatment and stored at 40 °C up to 180 days. Colour and pH were monitored and structural changes were characterised by dynamic light scattering, SDS-PAGE and centrifugal field-flow fractionation (FFF) coupled with multi-angle light scattering (MALS) and UV detectors to evaluate whether heat-induced differences would level out during storage. Both direct- and indirect UHT treatment led to structural changes, where the higher heat load of the indirect UHT treatment caused more pronounced changes. Indications were that storage-induced changes in pH, browning and non-reducible cross-links were not dependent on UHT treatment. However, FFF-MALS-UV analysis allowed characterisation of complex aggregates, where structural changes continued to be most pronounced in indirect UHT treated samples, and different storage-induced aggregation behaviour was observed.

Methylglyoxal-hydroimidazolones (MG-Hs) instead of Nɛ-(carboxymethyl)-l-lysine (CML) is the major advanced glycation end-product during drying process in black tea

This study was to examine the formation of advanced glycation end-products (AGEs) in black tea during drying process at 90, 120, and 150 °C for 1 h. Nine AGEs including Nɛ-(carboxyethyl)-l-lysine (CEL), Nɛ-(carboxymethyl)-l-lysine (CML), three isomers of methylglyoxal-hydroimidazolones (MG-Hs), three isomers of glyoxal-hydroimidazolones (GO-Hs), and argpyrimidine were quantified by using HPLC-MS/MS with isotope-labelled internal standard. Results showed that each AGE during the drying process of 150 °C was significantly higher (p < 0.05) than at 90 and 120 °C, and argpyrimidine was only found in the treatment of 150 °C. MG-H1/3 was first quantified as the major AGE during drying at 120-150 °C, the content respectively reached to (39.66 ± 2.61) μg/g and (58.88 ± 1.76) μg/g after 1 h drying, where CML content only had (19.86 ± 1.02) μg/g and (23.71 ± 1.40) μg/g. This study indicated that arginine derived-AGEs are the key components of black tea AGEs.

Cocoa melanoidins reduce the formation of dietary advanced glycation end-products in dairy mimicking system

The control of Maillard reaction in foods is important to preserve protein nutritional quality. In this study, we investigated the effects of melanoidins obtained from different roasted cocoa beans toward the formation of dietary advanced glycation end-products (d-AGEs) in aqueous solution of whey protein (WP) and glucose, glyoxal and methylglyoxal at 35 °C and pH 7.0. Cocoa melanoidins (4 mg/mL) were more effective to inhibit glyoxal-derived d-AGEs than methylglyoxal-derived d-AGEs, with 74.4% and 48% reduction of N-ε-carboxymethyllysine and methylglyoxal-hydroimidazolone formation in WP/glyoxal and WP/methylglyoxal system, respectively. Furthermore, protein-bound N-ε-fructosyllysine, measured through furosine, decreased down to 57.2% in presence of cocoa melanoidins in WP/glucose model system suggesting an effective control of the Maillard reaction in an early stage. These findings highlighted that cocoa melanoidins are functional ingredients able to mitigate protein glycation in dairy products during storage.

Green Tea Extract Decreases Arg-Derived Advanced Glycation Endproducts but Not Lys-Derived AGEs in UHT Milk during 1-Year Storage

Epigallocatechin gallate (EGCG)-enriched green tea extract (GTE) was added to lactose-reduced UHT-treated milk to evaluate its role in perturbing the Maillard reaction and the formation of advanced glycation endproducts (AGEs) during 1-year storage. The UHT processing caused epimerization of EGCG into gallocatechin gallate (GCG). For milk samples with added 0.1% w/v GTE, a EGCG/GCG loss of 26% was found soon after the UHT treatment and the loss increased to 64% after the 1-year of storage. LC-MS/MS analysis revealed the presence of various EGCG/GCG-α-dicarbonyl adducts and EGCG/GCG-hydroxymethylfurfural adducts in milk samples, while EGCG/GCG-amino acid adducts were not detected. Although EGCG/GCG trapped α-dicarbonyl compounds including glyoxal, methylglyoxal, 3-deoxyglucosone/3-deoxygalactosone, and diacetyl, it did not lower their net steady-state concentrations, except of 3-deoxyglucosone. The addition of GTE reduced the formation of Arg-derived AGEs by 2- to 3-fold, but surprisingly enhanced the accumulation of furosine and lysine-derived AGEs [Nε-(carboxymethyl)lysine and Nε-(carboxyethyl)lysine)] by 2-4-fold depending on the concentration of the added GTE and storage time. The present study shows that trapping of α-dicarbonyl compounds by EGCG may not be the major pathway for inhibiting the formation of AGEs in milk.

Limitation of Maillard Reactions in Lactose-Reduced UHT Milk via Enzymatic Conversion of Lactose into Galactooligosaccharides during Production

Lactose-hydrolyzed (LH) ultrahigh temperature (UHT) processed milk is more prone to Maillard reactions and formation of advanced glycation end products (AGEs) during processing and storage than conventional (CON) UHT milk because of the presence of free galactose and glucose. Commercially available β-d-galactosidases with transgalactosylating activity can incorporate galactose into galactooligosaccharides (GOSs) and potentially limit Maillard reactions in this lactose-reduced GOS-containing milk. The aim of this study was to examine the extent of Maillard reactions in a lactose-reduced GOS milk compared to LH and CON milk after UHT processing. The GOS milk had significant lower levels of lysine- and arginine-derived AGEs compared to LH milk, while their concentrations were similar to those found in CON milk. The total concentration of measured Arg-derived AGEs was similar to the total concentration of Lys-derived AGEs in the three types of milk, indicating that Arg is an important source of AGEs in milks. Interestingly, the GOS milk generated threefold higher concentrations (up to 330 ± 6 μM) of 3-deoxyglucosone (3-DG, a C6 α-dicarbonyl). These results demonstrate that GOS milk could be a potential alternative for LH milk for lactose-intolerant individuals, although further studies are needed to understand the increased formation of 3-DG in GOS-containing milk.