Maillard reactions lead to changes in food color, organoleptic properties, protein functionality, and protein digestibility. Numerous different strategies for controlling Maillard reactions in foods have been attempted during the past decades. In this paper, recent advances in strategies for controlling the Maillard reaction and subsequent downstream reaction products in food systems are critically reviewed. The underlying mechanisms at play are presented, strengths and weaknesses of each strategy are discussed, and reasonable reaction mechanisms are proposed to reinforce the evaluations. The review includes strategies involving addition of functional ingredients, such as plant polyphenols and vitamins, as well as enzymes. The resulting trapping or modification of Maillard targets, reactive intermediates, and advanced glycation endproducts (AGEs) are presented with their potential unwanted side effects. Finally, recent advances in processing for control of Maillard reactions are discussed.

The enzymatic hydrolysis of lactose to glucose and galactose gives rise to reactions that change the chemistry and quality of ambient-stored lactose-hydrolyzed ultra-high-temperature (UHT) milk. The aim of the present study was to investigate and compare chemical changes in lactose-hydrolyzed and conventional UHT milk during a 9 month ambient storage period. Several complementary analyses of volatiles, free amino acids, acetate, furosine, and level of free amino terminals were concluded. The analyses revealed an increased level of free amino acids and an increased formation rate of specific compounds such as furosine and 2-methylbutanal in lactose-hydrolyzed UHT milk compared to conventional UHT milk during storage. These observations indicate more favorable conditions for Maillard and subsequent reactions in lactose-hydrolyzed milk compared to conventional UHT milk stored at ambient temperature. Furthermore, it is postulated that proteolytic activity from the lactase-enzyme preparation may be responsible for the observed higher levels of free amino acids in lactose-hydrolyzed UHT milk.

Lactose reduced dairy products are more prone to Maillard reactions due to the presence of reactive monosaccharides. Conventional β-galactosidases, which are used for lactose hydrolysis in lactose-reduced dairy products, will lead to conversion of lactose into glucose and galactose, where especially galactose is very reactive during Maillard reactions. Some β-galactosidases have transgalactosylating activity and will thus convert lactose into galacto-oligosaccharides (GOS) and hereby limit the release of galactose. The aim of this study was to investigate the extent of participation of GOS in Maillard reactions in comparison to lactose, a 50:50 mixture of glucose and galactose, and galactose exclusively in sodium caseinate-based milk-like model systems heated at 130 and 75 °C at pH 6.8. The GOS system exhibited reduced loss of free amino groups; accumulated less furosine and less of the following advanced glycation end products (AGEs): Nε-carboxyethyl lysine, methylglyoxal-derived hydroimidazolone isomers, glyoxal-derived lysine dimer, and methylglyoxal-derived lysine dimer; and also developed less browning compared to monosaccharide models. However, the GOS–caseinate system accumulated more 3-deoxyglucosone and 3-deoxygalactosone, which resulted in higher concentrations of 5-(hydroxymethyl)­furfural and pyrraline. The results indicated that GOS overall participate less readily in Maillard reactions than the monosaccharides investigated but were more prone to degradation to C6 α-dicarbonyls species. Finally, relationship analysis indicated that C6 α-dicarbonyls seemed to primarily increase concentrations of 5-(hydroxymethyl)­furfural instead of AGEs. Our results suggest that conversion of lactose into GOS instead of monosaccharides in milk by transgalactosylating β-galactosidases could be a useful strategy for production of lactose-free milk for people with lactose intolerance.

The effect of epigallocatechin gallate enriched green tea extract (GTE) on flavor, Maillard reactions and protein modifications in lactose-hydrolyzed (LH) ultrahigh temperature (UHT) processed milk was examined during storage at 40 °C for up to 42 days. Addition of GTE inhibited the formation of Strecker aldehydes by up to 95% compared to control milk, and the effect was similar when GTE was added either before or after UHT treatment. Release of free amino acids, caused by proteolysis, during storage was also decreased in GTE-added milk either before or after UHT treatment compared to control milk. Binding of polyphenols to milk proteins was observed in both fresh and stored milk samples. The inhibition of Strecker aldehyde formation by GTE may be explained by two different mechanisms; inhibition of proteolysis during storage by GTE or binding of amino acids and proteins to the GTE polyphenols.

α-Dicarbonyls are reactive intermediates formed during Maillard reactions and carbohydrate degradation. The formation of seven α-dicarbonyls was characterized in solutions containing dairy related carbohydrates (galactose, glucose, lactose, and galacto-oligosaccharides (GOS)) during incubations at 40 and 50 °C with and without Nα-acetyl-L-lysine at pH 6.8 for up to 2 months. The concentrations of α-dicarbonyls in samples of monosaccharides with Nα-acetyl-L-lysine were found to be 3-deoxyglucosone (3-DG) > 3-deoxygalactosone (3-DGal) > glyoxal > glucosone, galactosone > methylglyoxal > diacetyl. The presence of Nα-acetyl-L-lysine resulted in up to 100-fold higher concentrations of C6 α-dicarbonyls but lesser formation of glyoxal in the monosaccharide-containing models compared to what was observed in the absence of Nα-acetyl-L-lysine. Galactose incubated with Nα-acetyl-L-lysine generated the highest concentrations of 3-DGal (up to 130 μM), glyoxal (up to 100 μM), and methylglyoxal (up to 9 μM) compared to the other carbohydrates during incubation. Surprisingly, 3-DG (1500 μM) and 3-DGal (80 μM) were formed at levels of 2 orders of magnitude higher in solutions of GOS in the absence of Nα-acetyl-Llysine as compared to the other carbohydrates at 40 °C, while GOS generated the lowest levels of glyoxal. GOS are widely used as an ingredient in various types of foods products, and it is therefore of importance to consider the risk of generating high levels of the reactive C6 α-dicarbonyl, 3-DG, in these types of products. This study contributes to the understanding of major αdicarbonyl formation as affected by the presence of primary amines in GOS-, lactose-, and galactose-containing solutions under moderate heating in liquid foods.

Proteolytic activity in milk may release bitter-tasting peptides and generate free amino terminals that react with carbohydrates, which initiate Maillard reaction. Ultrahigh temperature (UHT) heat treatment inactivates the majority of proteolytic enzymes in milk. In lactose-hydrolyzed milk a β-galactosidase preparation is applied to the milk after heat treatment, which has proteolytic side activities that may induce quality deterioration of long-term-stored milk. In the present study proteolysis, glycation, and volatile compound formation were investigated in conventional (100% lactose), filtered (60% lactose), and lactose-hydrolyzed (<1% lactose) UHT milk using reverse phase high-pressure liquid chromatography-mass spectrometry, proton nuclear magnetic resonance, and gas chromatography-mass spectrometry. Proteolysis was observed in all milk types. However, the degree of proteolysis was significantly higher in the lactose-hydrolyzed milk compared to the conventional and filtered milk. The proteins most prone to proteolysis were β-CN and αs1-CN, which were clearly hydrolyzed after approximately 90 days of storage in the lactose-hydrolyzed milk.

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.

et al.. Volatile component profiles of conventional and lactose-hydrolyzed UHT milk-a dynamic headspace gas chromatographymass spectrometry study.Abstract Lactose-hydrolyzed milk gains still increasing market share, and understanding the chemical characteristics of lactose-hydrolyzed milk products is important for the dairy industry. The aim of the present study was to identify and compare volatile compounds of commercial lactose-hydrolyzed and conventional ultra-high temperature (UHT) milk. For this purpose, the volatile compounds of lactose-hydrolyzed (<1% lactose), conventional (100% lactose), and filtered (60% lactose) UHT-treated milk were extracted using dynamic headspace sampling and analyzed by gas chromatography-mass spectrometry (GC-MS). A total of 24 volatile compounds were identified including ketones, aldehydes, and sulfides. Overall, principal component analysis (PCA) showed grouping of the different milk types, with loadings indicating a higher concentration of ketones in conventional versus lactose-hydrolyzed UHT milk, but PCA also indicated a marked batch-to-batch variation. Elucidation of individual volatile compounds detected also revealed that the content of ketones in general was higher in conventional UHT milk than in lactose-hydrolyzed milk; however, no significant differences in the volatile compound profiles could be identified between the various milk types as a result of the batch-to-batch variation. The present study