Sodium sulfite pH-buffering effect for improved xylose-phenylalanine conversion to N-(1-deoxy-d-xylulos-1-yl)-phenylalanine during an aqueous Maillard reaction

Novel comprehensive perspective on Amadori compounds: preparation, multiple roles and interaction with other compounds

Amadori compounds are pivotal intermediates in the Maillard reaction. Amadori compounds serve as flavor enhancers, browning precursors and bioactive components, so they are promising versatile food additives. Comprehensive reviews on multiple roles of Amadori compounds are scarce. Furthermore, there is a lack of reviews on green, efficient and commercially prospective preparation techniques of Amadori compounds and their interactions with other components. This paper reviewed preparation, multiple roles and interactions with other components in foods. Spray drying, microwave heating, natural deep eutectic solvents and vacuum dewatering were deemed as green, efficient and commercially prospective preparation techniques for Amadori compounds. Amadori compounds broadened the application field of Maillard reaction-obtained additives compared to final-products, enabling their uses not only in dark-colored foodstuffs but also in light-colored. Peptide-derived Amadori compounds showed greater potency for flavor generation compared to amino acid-derived. Amadori compounds presented eleven physiological activities. Amadori compounds exerted synergistic effect with essential nutrients (lipids, exogenous amino acids and carbohydrates), functional ingredients (polyphenols, carotenoids, glycosides) as well as several drugs. More preparation approaches of Amadori compounds and their synergistic effects with other ingredients await investigation. This review provided comprehensive theoretical guidance for industrial preparation and application of Amadori compounds as versatile additives.

Novel insight into Amadori compounds: Fate of Amadori compounds in food supply chain

Amadori compounds, pivotal intermediates in the Maillard reaction, act as flavor enhancer, browning precursor, and functional component. Amadori compounds consisting of diverse amino and carbonyl groups might show distinct flavor attributes and functional activities. Food production involves many supply chain stages where thermal treatment might produce Amadori compounds, and processing techniques and circumstances might affect the generation and stability of Amadori compounds. Moreover, gastrointestinal digestion might also influence the stability of Amadori compounds. To date, there is a lack of comprehensive review on the impact of various supply chain stages and digestion on Amadori compounds. This paper reviewed all reported Amadori compounds derived from diverse reducing sugars (glucose, xylose, ribose, maltose) and amino-containing compounds (common and specific amino acids, peptides), and compared differences in synthetic efficiency, flavor property, and functional activity among them; aggregated qualitative techniques; encapsulated quantitative techniques including indirect quantification and direct quantification, and intuitively compared strengths and weaknesses of these techniques; and outlined influence of processing, cooking, storage, and digestion on formation and stability of Amadori compounds. Appropriate processing techniques and conditions favored the generation and stability of Amadori compounds. Baking, frying, and roasting greatly facilitated Amadori compounds accumulation compared to steaming and boiling. Prolonged cooking at relatively low temperature favored Amadori compounds accumulation, whereas high-temperature cooking for a short duration resulted in fewer accumulation. Amadori compounds showed greater digestion resistance and could be absorbed by the intestine. This review offers scientific instruction for producing high-quality products with abundant Amadori compounds, or extracting plentiful Amadori compounds from processed foods as versatile food additives.

Extrusion of process flavorings from methionine and dextrose using modified starch as a carrier

This study aimed to produce process flavorings from methionine and glucose via Maillard reaction by extrusion method. Modified starch was used as a carrier to reduce the torque and facilitate the production process. Five formulations of process flavorings with different ratios of methionine: dextrose: modified starch: water as MS5 (72:18:5:5), MS15 (64:16:15:5), MS25 (56:14:25:5), MS35 (42:12:35:5), and MS45 (40:10:45:5) were prepared and feded into the extruder. The temperatures of the extruder barrel in zones 1 and 2 were controlled at 100, and 120°C, with a screw speed of 30 rpm. The appearance of the obtained products, torque, pH before and after extrusion, color, volatile compounds, and sensory evaluation were determined. The extrudate from the formulation containing the highest amount of modified starch (MS45) gave the highest L* (lightness) of 88.00, which increased to 93.00 (very light) after grinding into a powder. The process flavorings from all formulations exhibited similar sensory scores in terms of aroma, taste, and water solubility, with a very slight difference in color. However, MS25, MS35 and MS45 indicated the torque at 10 Nm/cm3, while MS5 and MS 15 exhibited higher torque at 18, and 25 Nm/cm3, respectively. Extruded process flavorings from MS25 were analyzed for their flavor profiles by gas chromatography-mass spectrometry. Twelve volatile compounds including the key volatile compounds for sulfurous and vegetable odor type, dimethyl disulfide, methional, and methanethiol, were found. Four pyrazine compounds presented nutty, musty and caramelly odor; and 3-hydroxybutan-2-one and heptane-2,3-dione, which gave buttery odor type, were also detected. The results demonstrated a successful production of process flavorings using modified starch as carrier to facilitate and reduce the torque during the extrusion process.

Food polyphenols and Maillard reaction: regulation effect and chemical mechanism

Maillard reaction is a non-enzymatic thermal reaction during food processing and storage. It massively contributes to the flavor, color, health benefits and safety of foods and could be briefly segmented into initial, intermediate and final stages with the development of a cascade of chemical reactions. During thermal reaction of food ingredients, sugar, protein and amino acids are usually the main substrates, and polyphenols co-existed in food could also participate in the Maillard reaction as a modulator. Polyphenols including flavan-3-ols, hydroxycinnamic acids, flavonoids, and tannins have shown various effects throughout the process of Maillard reaction, including conjugating amino acids/sugars, trapping α-dicarbonyls, capturing Amadori rearrangement products (ARPs), as well as decreasing acrylamide and 5-hydroxymethylfurfural (5-HMF) levels. These effects significantly influenced the flavor, taste and color of processed foods, and also decreased the hazard products' level. The chemical mechanism of polyphenols-Maillard products involved the scavenging of radicals, as well as nucleophilic addition and substitution reactions. In the present review, we concluded and discussed the interaction of polyphenols and Maillard reaction, and proposed some perspectives for future studies.

Glycine-Xylose Amadori Compound Formation Tracing through Maillard Browning Inhibition by 2-Threityl-thiazolidine-4-carboxylic Acid Formation from Deoxyosone and Exogenous Cysteine

The browning inhibition of cysteine on the Maillard reaction of glycine-xylose performed under stepwise increased temperature was investigated. The browning degrees of the final products prepared with cysteine addition at different time points were found dissimilar, and the addition time point of cysteine yielding the lightest browning products was consistent with the time when the glycine-xylose Amadori rearrangement product (GX-ARP) reached its maximum yield. To clarify the reason for browning inhibition caused by cysteine, the evolution of key browning precursors formed in the GX-ARP model with cysteine involved was investigated by HPLC with a diode array detector. The results on the browning degree of the thermal reaction products of GX-ARP with cysteine addition showed great inhibition of α-dicarbonyl generation, which resulted in a significant increase in the activation energy of GX-ARP conversion to browning formation during heat treatment. Strong evidence suggested that the additional cysteine got involved in GX-ARP degradation and reacted with the deoxyosones derived from GX-ARP to yield cyclic 2-threityl-thiazolidine-4-carboxylic acid (TTCA). TTCA formation shunted the degradation of deoxyosones into short-chain α-dicarbonyls, which were important browning precursors, and consequently inhibited the Maillard browning.

Amadori Reaction Products of Theanine and Glucose: Formation, Structure, and Analysis in Tea

Amadori rearrangement products (ARPs) derived from the Maillard reaction between theanine and glucose (ARP 1), as well as pyroglutamic acid and glucose (ARP 2), were identified by liquid chromatograph tandem mass spectroscopy methods. The effects of initial reactant ratio, temperature, pH, and heating time on ARP generation were analyzed. The formation of both ARPs was most favored under 100 °C, while an alkaline environment slightly promoted the generation of ARP 1 and acidic conditions contributed more to ARP 2 formation. The decomposition of ARP 1 was suggested to be the predominant formation mechanism of ARP 2. Preparation, purification, and structure identification of ARP 1 were conducted, with its structure confirmed as 1-deoxy-1-l-theanino-d-fructose. The contents of ARP 1 in green, black, dark, white, yellow, and Oolong teas were quantitatively determined, of which black teas contained the highest levels of ARP 1, possibly due to the high glucose content and processing techniques.

Inhibition of Maillard reaction during alkaline thermal hydrolysis of sludge

The Maillard reaction (MR) occurs during the alkaline thermal hydrolysis (ATH) of sludge, which affects the quantity and quality of recovered protein. In this paper, four different sulfites were added to investigate their inhibitory effects on melanoidin production. The results showed that sulfites inhibited melanoidin production during ATH of sludge and the inhibitory rate increased with their concentration. At a concentration of 5.71 g/L, the inhibitory rates of NaHSO₃ on melanoidin were 63.27%. Furthermore, the 3D-EEM (Three-Dimension Excitation-Emission-Matrix) fluorescence spectroscopy and protein testing data showed that the inhibition of melanoidin production was accompanied by an increased protein concentration, and protein increased with increasing sulfites concentration. A 2.5-fold increase in protein concentration with Na₂S₂O₄ significantly enhanced the quantity of protein recovered. Therefore, the addition of sulfite during ATH of sludge reduces the amount of non-biodegradable melanoidin, which in turn benefits protein recovery.

Dependence and Conversion Mechanism for Selective Preparation of a Xylose-Diglycine Amadori Compound and a Cross-linking Product in an Aqueous Maillard Reaction

The structure of the prepared Amadori rearrangement product of xylose-glycylglycine (XGG-ARP) and a cross-linking product (XGG-CP) was first characterized by liquid chromatography-mass spectrometry (LC-MS)/MS and NMR analysis, respectively. The dependences were then studied for the formation of XGG-ARP and XGG-CP in an aqueous Maillard reaction of a xylose-glycylglycine model system. The influence factors were the reaction temperature, pH, molar ratio of reactants, and the reaction time. It was found that XGG-ARP would acquire the highest yield of 73.8% when the thermal reaction was carried out at 70 °C and pH 8.0 for 10 min. A higher temperature and a lower pH might enhance the yield of the formation of XGG-CP. Combining the low-temperature dehydration reaction with the high-temperature aqueous-phase Maillard reaction increased the XGG-CP yield to 43.54%. The efficient and selective preparation of XGG-ARP and XGG-CP was controllable through the adjustment of reaction conditions. Moreover, the pathway of XGG-CP formation from XGG-ARP and Gly-Gly by the aldimine condensation reaction was also proposed. The high stability of an XGG-CP molecule enhanced by its p-π-p conjugated structure inhibited the occurrence of the Amadori rearrangement and led to a non-keto structure, blocking the further Maillard reaction of XGG-CP.

Key Aspects of Amadori Rearrangement Products as Future Food Additives

Flavor is one of the most important factors in attracting consumers and maximizing food quality, and the Maillard reaction (MR) is highly-involved in flavor formation. However, Maillard reaction products have a big drawback in their relatively low stability in thermal treatment and storage. Amadori rearrangement products (ARPs), MR intermediates, can alternatively act as potential flavor additives for their better stability and fresh flavor formation ability. This review aims to elucidate key aspects of ARPs’ future application as flavorings. The development of current analytical technologies enables the precise characterization of ARPs, while advanced preparation methods such as synthesis, separation and drying processes can increase the yield of ARPs to up to 95%. The stability of ARPs is influenced by their chemical nature, pH value, temperature, water activity and food matrix. ARPs are associated with umami and kokumi taste enhancing effects, and the flavor formation is related to amino acids/peptides of the ARPs. Peptide-ARPs can generate peptide-specific flavors, such as: 1,6-dimethy-2(1H)-pyrazinone, 1,5-dimethy-2(1H)-pyrazinone, and 1,5,6-trimethy-2(1H)-pyrazinone. However, further research on systematic stability and toxicology are needed.

Formation and Antioxidant Activity of Maillard Reaction Products Derived from Different Sugar-amino Acid Aqueous Model Systems of Sesame Roasting

This investigation was carried out to offer insight into the formation and antioxidant activity of Maillard reaction products (MRPs) derived from various sugar-amino acid model systems active in the roasting of sesame seeds. Reducing sugars (glucose, fructose, and xylose) and amino acids (serine, cystine, arginine, and lysine) present in sesame seeds were used to prepare the MRPs at various reaction times, and then the effect of reaction time on the MRPs derived from the various model systems was investigated. Within the first 15 min, the amounts of free amino groups decreased around 40% remaining amino groups of Lys-sugar model and around 75% remaining amino groups of Arg-sugar model. Results indicated that reducing sugar and free amino groups decreased obviously in Lys- and Arg-model systems. Based on correlation coefficient of antioxidant activities assessment and MRP formation in the Lys- and Arg-model systems above 0.978 and an extremely significant correlation in Pearson test exists, a conclusion could be made that these model systems are critical contributing factors in MRP formation during the roasting of sesame seeds. These findings offer insight into the formation and antioxidation of MRPs during the sesame seeds roasting.

Interaction of (-)-Epigallocatechin Gallate and Deoxyosones Blocking the Subsequent Maillard Reaction and Improving the Yield of N-(1-Deoxy-d-xylulos-1-yl)alanine

(-)-Epigallocatechin gallate (EGCG) had a significant effect on Maillard reaction intermediate formation in the xylose/alanine model system. A trapping effect of EGCG on the reactive deoxyosones was observed to change the reaction pathways. The rate constant of Amadori rearrangement product (ARP) conversion to deoxyosones was decreased with EGCG addition, indicating an inhibition of ARP degradation. Dehydration improved the ARP formation during the thermal reaction and synergistically improved the yield of ARP with the EGCG trapping effect on the deoxyosones. Additionally, EGCG decreased the activation energy for the conversion of xylose/alanine to ARP (from 77.8 to 62.8 kJ/mol) and in turn accelerated the ARP formation. The effect of EGCG was further facilitated at the optimal conditions of 90 °C, at pH 7.5, and a molar ratio of xylose to alanine of 2:1, which improved the yield of ARP (N-(1-deoxy-d-xylulos-1-yl)alanine) from 2 to 95%.

Characterization, Variables, and Antioxidant Activity of the Maillard Reaction in a Fructose⁻Histidine Model System

Fructose and its polysaccharides are widely found in fruits and vegetables, with the Maillard reaction of fructose affecting food quality. This study aimed to investigate the Maillard reaction of fructose using a fructose–histidine model system. The reaction process was characterized using fluorescence spectroscopy and ultraviolet spectroscopy. The effects of temperature, initial reactant concentration, initial fructose concentration, initial histidine concentration, and initial pH value on the different stages of the Maillard reaction were studied. Reactant reduction, ultraviolet and fluorescence spectra, acetic acid content, 5-hydroxymethylfurfural (5-HMF) content, and browning intensity were evaluated. The results showed that increasing the temperature and reactant concentration promoted the condensation reaction of fructose and amino acid in the early stage, the formation of intermediate products with ultraviolet absorption and fluorescence in the intermediate stage, and the formation of pigment in the final stage. The 5-HMF concentration decreased with increasing histidine concentration and initial pH value. Changes in the shape of ultraviolet and fluorescence spectra showed that the initial pH value affected not only the reaction rate, but also the intermediate product types. The 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging rate of the Maillard reaction products increased with increasing temperature, reactant concentration, and initial pH value.