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

Abstract

A comprehensive quantitative characterization of Maillard reaction products was carried out for conventional (CON) and lactose-hydrolyzed (LH) ultrahigh temperature (UHT) milk during storage at 20, 30, and 40 °C for 1 year. The accumulation of 3-deoxyglucosone (3-DG) and 3-deoxygalactosone (3-DGal) in LH-UHT milk ranged from 20-fold (at 20 °C) to 44-fold (at 40 °C) higher than that in CON-UHT milk. High temperature storage (40 °C) significantly accelerated the accumulation of 3-DG, 3-DGal, and 5-hydroxymethyl furfural but not the majority of the analyzed advanced glycation endproducts (AGEs). The concentrations of major AGEs including N-ε-carboxymethyllysine (CML), N-ε-carboxyethyllysine (CEL), methylglyoxal-hydroimidazolone isomers (MG-H1/H3), glyoxal-hydroimidazolone isomers (G-H1/H3), and G-H2 detected in CON milk during storage were in the range 12–700, 1–14, 8–45, 4–13, and 1–30 μM, respectively, while they were 30–570, 2–88, 17–150, 9–20, and 5–34 μM, respectively, in LH milk. Pyrraline, S-(carboxymethyl)­cysteine (CMC), and glyoxal-lysine dimer were detected in lower levels, while MG-H2, methylglyoxal-lysine dimer, argpyrimidine, glyoxal-lysine-amide, glycolic acid-lysine-amide, and pentosidine were not detected in any of the milk samples. This work demonstrates for the first time that five of the analyzed AGEs (CML, CEL, MG-H1/H3, G-H1/H3, and G-H2) could be selected as markers for evaluation of the extent of the Maillard reaction in UHT milk. These results contribute to a better understanding of how Maillard reactions progress during storage of UHT milk and can be used to develop strategies to inhibit Maillard reactions in LH milk.

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

“…Microwave‐assisted acid hydrolysis of the samples was conducted to measure the total AGEs as previously described by Zhang et al. [ 30 ] Briefly, 29.41 mg of each powder (containing 10 mg protein) was mixed with 3 mL of 12 M HCl to obtain the final concentration of 6 M HCl and heated at 150°C for 1 min, followed by heating at 165°C for 10 min by using a Biotage Initiator and microwave synthesizer (Biotage, Uppsala, Sweden). Thereafter, 100 µL hydrolyzed sample was dried by vacuum evaporation and dissolved into 500 µL 0.01% formic acid.…”

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

“…To detect free adducts (nonprotein bound), proteins in milk samples were initially precipitated by adding ice-cold methanol (1:2 v/v) followed by centrifugation at 14,500 g for 10 min, and the supernatant was subjected to LC–MS/MS analysis. To detect protein-bound adducts (EGCG-protein amino acid adduct), samples were hydrolyzed with 6 M HCl (see LC–MS/MS analysis of AGEs below) or via enzymatic hydrolysis with pepsin, pronase E, aminopeptidase, and prolidase before LC–MS analysis.…”

“…The sample was incubated at 37 °C for 2 h in the dark and then filtered into an amber HPLC glass vial through a 0.22 μm membrane filter. A Thermo Ultimate 3000 UHPLC system coupled to a DAD and an Orbitrap Q Exactive mass spectrometer was used for the identification and quantification of derivatized α-dicarbonyl compounds using an LC–MS/MS chromatographic method described elsewhere . The DAD detection wavelength was set to 316 nm.…”

“…However, it is highly susceptible toward the Maillard reaction, as lactose hydrolysis increases the net concentration of reducing sugars and the heat load during the UHT treatment accelerates the rate of the Maillard reaction. Previous investigations have shown that lactose-reduced milk accumulates higher levels of α-dicarbonyl compounds and certain AGEs compared to nonhydrolyzed conventional milk during storage . Moreover, lactose-reduced UHT-treated milk is susceptible to rapid browning compared to conventional UHT-treated milk .…”

“…Several other investigations have reported that polyphenols inhibit the formation of AGEs by trapping α-dicarbonyl compounds. − These reports, nevertheless, present their conclusions based on qualitative analysis of the formation of polyphenol-α-dicarbonyl adducts but seldom measure the actual formation of individual AGEs. A few authors have indeed shown that certain flavonoids and plant extracts reduce the formation of AGEs by quantifying selected AGEs, mainly Lys-derived Nε-(carboxymethyl)­lysine (CML) and/or Nε­(carboxyethyl)­lysine) (CEL) in tea, beverages, milk, and in protein model systems. − Importantly, it has recently been demonstrated that Arg-derived AGEs must be considered in order to evaluate the extent Maillard reactions in UHT-treated milk …”