Formation mechanism of volatile and non-volatile compounds in peptide–xylose Maillard reaction

The volatile organic compounds generated from the Maillard reaction between l-ascorbic acid and l-cysteine in hot compressed water

BACKGROUND

Hot compressed water (HCW), also known as subcritical water (SCW), refers to high-temperature compressed water in a special physical and chemical state. It is an emerging technology for natural product extraction. The volatile organic compounds (VOCs) generated from the Maillard reaction between l-ascorbic acid (ASA) and l-cysteine (Cys) have attracted significant interest in the flavor and fragrance industry. This study aimed to explore the formation mechanism of VOCs from ASA and Cys and examine the effects of reaction parameters such as temperature, time, and pH in HCW.

RESULTS

The identified VOCs were predominantly thiophene derivatives, polysulfides, and pyrazine derivatives in HCW. The findings indicated that thiophene derivatives were formed under various pH conditions, with polysulfide formation favored under acidic conditions and pyrazine derivative formation preferred under weak alkaline conditions, specifically at pH 8.0.

CONCLUSION

The Maillard reaction between ASA and Cys mainly produced thiophene derivatives, polysulfides, and pyrazine derivatives in HCW. The generation mechanism was significantly dependent on the surrounding pH conditions. © 2024 Society of Chemical Industry.

Creating alternative seafood flavour from non-animal ingredients: A review of key flavour molecules relevant to seafood

This review summarises current knowledge of the molecular basis for flavour profiles of popular seafood types (crustacean (crab, lobster, prawn, etc.), mollusc (oyster, squid, etc.), oily fish (salmon, sardine, etc.) and white fish (barramundi, turbot, etc.)), and provides a foundation for formulating improved plant-based seafood alternative (PBSA) flavours. Key odour-active volatile molecules were identified from a systematic review of published olfactometry studies and taste-active compounds and macronutrient profiles of different seafood species and commercial PBSAs from nutrition databases were compared. Ingredients commonly used in commercial BPSAs and new potential sources of flavouring agents are evaluated. While significant challenges in replicating seafood flavour and texture remain, this review provides some insights into how plant-based ingredients could be applied to improve the acceptability of PBSAs.

Maillard Reaction Process and Characteristic Volatile Compounds Formed During Secondary Thermal Degradation Monitored via the Change of Fluorescent Compounds in the Reaction of Xylose-Corn Protein Hydrolysate

Until now, no effective method has been found to monitor the Maillard reaction process for complex protein hydrolysates. Dynamic changes in the concentration of α-dicarbonyl compounds, fluorescence intensity, and browning degree were investigated during the Maillard reaction of corn protein hydrolysates. When the fluorescence intensity reached the peak, deoxyosones would continue to be increased by ARP's degradation. However, the reaction node with the highest fluorescence intensity coincided with the turning point of the browning reaction, and the subsequent browning rate remarkably increased. Therefore, the change in fluorescence intensity could be used to monitor the degradation of ARP and the formation of browning melanoidin at different stages of the Maillard reaction of complex systems, thus effectively indicating the process of the Maillard reaction. When Maillard reaction intermediates (MRIs) with maximum fluorescent compounds were heated, the most abundant pyrazines were subsequently achieved. However, furan compounds would be progressively increased during the thermal process of MRIs with continuously enhanced browning.

The number and position of unsaturated bonds in aliphatic aldehydes affect the cysteine-glucose Maillard reaction: Formation mechanism and comparison of volatile compounds

Nonanal, (E)-2-nonenal, (E,E)-2,4-nonadienal, and (E,Z)-2,6-nonadienal were used to reveal the effect of the number and position of unsaturated bond in aliphatic aldehydes on Maillard reaction for the generation of 88 stewed meat-like volatile compounds. The results showed that (E,E)-2,4-nonadienal and (E,Z)-2,6-nonadienal exhibited greater inhibition of the cysteine reaction with glucose than nonanal and (E)-2-nonenal. However, the positions of the unsaturated bonds in aliphatic aldehydes in the Maillard reaction stage were similar. A carbohydrate module labeling approach was used to present the formation pathways of 34 volatile compounds derived from the Maillard reaction with aliphatic aldehyde systems. The number and position of unsaturated bonds in aliphatic aldehydes generate multiple pathways of flavor compound formation. 2-Propylfuran and (E)-2-(2-pentenyl)furan resulted from aliphatic aldehydes. 5-Butyldihydro-2(3H)-furanone and 2-methylthiophene were produced from the Maillard reaction. 2-Furanmethanol, 2-thiophenecarboxaldehyde, and 5-methyl-2-thiophenecarboxaldehyde were derived from the interaction of aliphatic aldehydes and the Maillard reaction. In Particular, the addition of aliphatic aldehydes changed the formation pathway of 2-propylthiophene, thieno[3,2-b]thiophene, and 2,5-thiophenedicarboxaldehyde. Heatmap and PLS-DA analysis could discriminate volatile compound compositions of the five systems and screen the marker compounds differentiating volatile compounds.

Effect of Maillard Reaction Products Derived from Cysteine on the Formation of Dimethyl Disulfide and Dimethyl Trisulfide during Storage

The effect of Maillard reaction products derived from cysteine on dimethyl disulfide (DMDS) and dimethyl trisulfide (DMTS) was evaluated in the ternary mixture (methionine, cysteine, and xylose) and binary mixture (methionine and 2-threityl-thiazolidine-4-carboxylic acid) during 56 days storage. Changes in concentrations revealed that the methionine/cysteine/xylose model showed lower concentrations of DMDS and DMTS than those of the binary mixture. Antioxidant ability and labeled isotopomer proportion information indicated that low levels of DMDS and DMTS in the ternary mixture were attributed to not only 2-furfurylthiol and 2-methyl-3-furanthiol (MFT) reacting with methanethiol but also the ternary mixture having stronger antioxidant activity. Correlation analysis demonstrated that MFT reacting with methanethiol and strong antioxidant ability are considered major factors controlling the formation of DMTS and DMDS, respectively. Research on the reaction mechanism of the rate-limiting step would provide the basis for preventing the development of DMDS and DMTS during storage.

Production of nutty-like flavour from soybean protein isolate hydrolysate pretreated or assisted by microwave irradiation: impact of encapsulation on nutty flavour quality

The aim of this study was to prepare a nutty-like flavour from enzymatic hydrolysates of soybean protein isolate pretreated or assisted by microwave heating. In both cases the time of microwave heating was optimized and degree of hydrolysis (DH) and content of free amino acids in each hydrolysate were determined and compared with those of hydrolysate prepared by conventional method (E-HSC). The hydrolysates showed the best results were used as main precursors of nutty flavour. The generated volatiles were subjected to GC-MS analysis and odour evaluation. The effect of encapsulation and storage on the nutty flavour was evaluated. The results revealed that the hydrolysates pretreated (E-HSMP₇) or assisted (E-HSMA₆) by microwave at 7 and 6 min, respectively showed a significant increase in DH. The nutty flavour generated from these hydrolysates (NFMP₇ and NFMA₆) were dominated with pyrazines whereas, the volatiles from E-HSC (NFC) dominated with furans. NFMA₆ showed the highest intensity of nutty and overall acceptability notes, compared with NFMP₇ and NFC. Encapsulation resulted in a significant decrease in pyrazines, which are responsible for the nutty note. The significant increase in nutty aroma intensity of the stored encapsulated sample was correlated to the increase in pyrazines.

Characterization of Thermally Induced Flavor Compounds from the Glucosinolate Progoitrin in Different Matrices via GC-TOF-MS

As important flavor precursors, glucosinolates are ubiquitous in the plant family of Brassicaceae. Glucosinolate degradation products are the major volatile flavor compounds of rapeseed oil, accounting for up to 80% of the total volatiles. However, up to now, little attention has been paid to the volatile flavor products of the nonenzymatic thermal degradation of glucosinolates. One of the most important factors that determine the flavor of hot-pressed rapeseed oil is the roasting process, where the thermal degradation of glucosinolates mainly occurs. The thermal degradation behavior and volatile products of progoitrin (the main glucosinolate of rapeseed) in different matrices (phosphate buffer at a pH value of 5.0, 7.0, or 9.0, sea sand, and rapeseed powder) at different temperatures (150-200 °C) and times (0-60 min) were studied using HPLC and GC-TOF-MS. Thereby, the degradation rate of progoitrin decreased in the following order: pH 9.0 > sea sand > rapeseed powder > pH 7.0 > pH 5.0. Further, a higher degradation was observed with increasing temperature and time. Under the applied conditions in this study, 2,4-pentadienenitrile was the major nitrile and thiophenes were the major sulfur-containing volatile compounds formed. Possible formation pathways of main sulfur-containing and nitrogen-containing volatiles were proposed.

Maillard reaction of food-derived peptides as a potential route to generate meat flavor compounds: A review

Plant-based meat analogues (PBMA) are promising foods to address the global imbalance between the supply and demand for meat products caused by the increasing environmental pressures and growing human population. Given that the flavor of PBMA plays a crucial role in consumer acceptance, imparting meat-like flavor is of great significance. As a natural approach to generate meat-like flavor, the Maillard reaction involving food-derived peptides could contribute to the required flavor compounds, which has promising applications in PBMA formulations. In this review, the precursors of meat-like flavor are summarized followed by a discussion of the reactions and mechanisms responsible for generation of the flavor compounds. The preparation and analysis techniques for food-derived Maillard reacted peptides (MRPs) as well as their taste and aroma properties are discussed. In addition, the MRPs as meat flavor precursors and their potential application in the formulation of PBMA are also discussed. The present review provides a fundamental scientific information useful for the production and application of MRPs as meat flavor precursors in PBMA.

Development of Beef Volatile Flavor Compounds in Response to Varied Oven Temperature and Degree of Doneness

Beef volatile flavor compound (VFC) development at the center, mid, and surface layers of cooked steaks was evaluated through 18 cookery treatment combinations consisting of oven cooking temperature (OT; 177°C, 246°C, and 343°C) and final internal steak temperature (IT; 57°C, 63°C, 68°C, 74°C, 79°C, and 85°C). In total, 72 VFC were measured representing the Maillard reaction and lipid degradation. Five VFC were impacted by a three-way interaction of OT × IT × layer (P ≤ 0.030). Two VFC were impacted by a two-way interaction of OT × IT (P ≤ 0.010). Sixteen VFC were impacted by a two-way interaction of OT × layer (P ≤ 0.050). Sixteen VFC were impacted by a two-way interaction of IT × layer (P ≤ 0.050). Twenty VFC were impacted by the main effect of layer (P ≤ 0.010). Eight VFC were impacted by the main effect of IT (P ≤ 0.050). Maillard compounds were formed primarily at steak surfaces, with a general increase in content with greater final IT, and OT to a lesser extent. Lipid-derived compounds were diverse. Methyl esters and aldehydes had lower contents at steak surfaces and were primarily found within the inner portions of steaks. Conversely, certain alcohols and ketones were more prominent at steak surfaces. Development of compounds among layers was also consistently influenced by IT and OT. It may be concluded that flavor-contributing compounds vary among cooked beef steaks at different depths and cookery temperatures. As a result, OT and final IT may be utilized to mediate the final volatile compound composition.

New insight into the formation mechanism of 2-furfurylthiol in the glucose-cysteine reaction with ribose

The molecular formation mechanism of 2-furfurylthiol in the glucose-cysteine reaction is not reported. Knowledge of the molecular interaction of glucose and ribose on the generation of 2-furfurylthiol is still unclear. The carbon module labeling (CAMOLA) technical approach was applied to elucidate the formation mechanism of 2-furfurylthiol in the glucose-cysteine reaction. The effect of ribose on the glucose-cysteine reaction was also evaluated. The results showed that 2-furfural and 2-furanmethanol were important intermediates for the formation of 2-furfurylthiol. Irrespective of the heating time, 2-furfurylthiol was mainly generated from an intact C₅ glucose skeleton (88-89%), whereas the recombination of glucose fragments had minimal contribution. 2-Furfural could be generated from the Maillard reaction between glucose and cysteine or glucose alone, which further formed 2-furanmethanol. Immediately, 2-furfurylthiol could arise from the reaction of 2-furanmethanol and H₂S from cysteine. Moreover, the reaction of glucose, ribose, and cysteine could generate 2-furfural, 2-furanmethanol, and 2-furfurylthiol by an addition effect confirmed by the model reaction and food system.

Formation of Pyrazines in Maillard Model Systems: Effects of Structures of Lysine-Containing Dipeptides/Tripeptides

At present, most investigations involving the Maillard reaction models have focused on free amino acids (FAAs), whereas the effects of peptides on volatile products are poorly understood. In our study, the formation mechanism of pyrazines, which were detected as characteristic volatiles in sunflower seed oil, from the reaction system of glucose and lysine-containing dipeptides and tripeptides was studied. The effect of the amino acid sequences of the dipeptides and tripeptides on pyrazine formation was further highlighted. Four different dipeptides and six tripeptides were selected. The results showed that the production of pyrazines in the lysine-containing dipeptide models was higher than that in the tripeptide and control models. Compounds 2,5(6)-Dimethylpyrazine and 2,3,5-trimethylpyrazine were the main pyrazine compounds in the dipeptide models. Furthermore, the C- or N-terminal amino acids of lysine-containing dipeptides can exert an important effect on the formation of pyrazines. In dipeptide models with lysine at the C-terminus, the content of total pyrazines followed the order of Arg−Lys > His−Lys; the order of the total pyrazine content was Lys−His > Lys−Arg in dipeptide models with N-terminal lysine. Additionally, for the tripeptide models with different amino acid sequences, more pyrazines and a greater variety of pyrazines were detected in the tripeptide models with N-terminal lysine/arginine than in the tripeptide models with N-terminal histidine. However, the total pyrazine content and the percentage of pyrazines in the total volatiles were similar in the tripeptide models with the same amino acids at the N-terminus. This study clearly illustrates the ability of dipeptides and tripeptides containing lysine, arginine and histidine to form pyrazines, improving volatile formation during sunflower seed oil processing.

Generation of key aroma compounds in Beijing roasted duck induced via Maillard reaction and lipid pyrolysis reaction

This study explores the evolution of key aroma compounds and the chemical changes of their precursors, including reducing sugars, free amino acids, free fatty acids, thiamine and proximate compositions in Beijing roasted duck during roasting for 0-80 min. The results showed that the amounts and contents of 9 key aroma compounds in roasted ducks first quickly increased (p < 0.05) and subsequently remained constant (p > 0.05) after 50 min, except for a slight decrease between 70 and 80 min. Cysteine, cystine and methionine were the main free amino acids and could react with glucose and ribose to generate 2-furfurylthiol, dimethyl trisulfide and methional. Linoleic acid, α-linolenic acid and arachidonic acid had important effects on the increase of hexanal, octanal and nonanal together with the emergence and formation of heptanal, (E, E)-2,4-decadienal and 1-octene-3-ol. However, thiamine might not be the main precursor of the key aroma compounds in Beijing roasted duck.

Maillard reaction products derived from food protein-derived peptides: insights into flavor and bioactivity

Food protein-derived peptides serve as food ingredients that can influence flavor and bioactivity of foods. The Maillard reaction plays a crucial role in food processing and storage, and generates a wide range of Maillard reaction products (MRPs) that contribute to flavor and bioactivity of foods. Even though the reactions between proteins and carbohydrates have been extensively investigated, the modifications of food protein-derived peptides and the subsequent impacts on flavor and bioactivity of foods have not been fully elucidated. In this review, the flavor and bioactive properties of food-derived peptides are reviewed. The formation mechanisms with respect to MRPs generated from food protein-derived peptides have been discussed. The state-of-the-art studies on impacts of the Maillard reaction on flavor and bioactivity of food protein-derived peptides are also discussed. In addition, some potential negative effects of MRPs are described.

Aqueous Preparation of Maillard Reaction Intermediate from Glutathione and Xylose and its Volatile Formation During Thermal Treatment

Maillard reaction intermediate (MGX) generated from glutathione and xylose in aqueous medium was prepared via the Maillard reaction performed under a two-stage temperature increase process. The purified MGX was identified by Fourier-transform infrared spectroscopy, mass spectrometry, and nuclear magnetic resonance as N-(1-deoxy-d-xylulos-1-yl)-glutathione (Amadori compound, C₁₅ H₂₅ O₁₀ N₃ S) with five main isomers. The method of Maillard reaction performed under a two-stage temperature increase process was further verified by high-performance liquid chromatography. The optimal reaction time and temperature for the preparation of MGX was determined as 60 min at 90 °C. The yield of MGX was increased from 8.60% to 55.52% through thermal reaction coupled with vacuum dehydration. In addition, rapid and more Maillard-type volatile compounds were formed in MGX during thermal treatment than that in Maillard reaction products or glutathione-xylose mixture. Beside, MGX possessed more pleasing meat-like volatile profile compared with the Amadori compound of glutamic acid-xylose (AAX), cysteine-xylose (ACX), and glycine-xylose (AGX). Therefore, it suggested that the MGX had the potential to achieve a better flavor formation during thermal treatment. PRACTICAL APPLICATION: Maillard reaction intermediates, such as Amadori or Heyns rearrangement products (ARP or HRP), are important flavor precursors, which possess stable physicochemical properties, but tend to degrade into flavor compounds at high temperatures. Maillard reaction intermediate from glutathione and xylose acts as primary flavor enhancers to complete Maillard reaction to produce flavors in the subsequent thermal processing, which can significantly improve and stabilize the flavor quality of the meaty food, and deserves a very broad application prospects. The new developed method will be a significant theoretical basis on research preparation and properties of Maillard reaction intermediates in complex food systems.

Simultaneous roasting and extraction of green coffee beans by pressurized liquid extraction

Green coffee extracted by pressurized liquid extraction (PLE) was found to undergo a roasting process similar to traditional roasting. Liquid chromatography-tandem mass spectrometry was used to investigate the chlorogenic acid (CGA) composition and profiling changes by PLE under different extraction conditions and showed almost identical generation and degradation of CGAs occurring during traditional coffee roasting. Compared with the traditional extraction of roasted coffee, optimized PLE coffee showed three- and two-fold higher antioxidant activity and total CGA contents, respectively. Composition diversity and the content of volatile compounds in PLE coffee were found to increase as the PLE temperature increased but were lower than those of traditionally roasted coffee. The sensory attributes of PLE coffee were also evaluated to have be associated with a profile change in the volatile compounds and non-volatile CGA compounds.

Studies on the Origin of Carbons in Aroma Compounds from [13C₆]Glucose -Cysteine-(E)-2-Nonenal Model Reaction Systems

The thermal degradation of lipid oxidation products with amino acids and reducing sugars is known to be important for the characteristic aroma generation in both meat and meat-like process flavorings. SPME(solid phase microextraction)/GC-MS was used to analyze the volatiles produced from a solution of [¹³C₆]glucose, cysteine, and lipid degradation product- (E)-2-nonenal, heated at 130 °C for 90 min. Analysis of the mass spectra showed that the resulting 2-butyl-thiophene and 5-butyldihydro-2(3H)-furanone were ¹³C₆-labeled and hence stemmed from glucose. Glucose and (E)-2-nonenal were equally important for the formation of 2-pentylfuran, whether cysteine was present in the reaction or not. 2-Furanmethanol, (E)-2-(1-pentenyl)-furan, 2-hexanoylfuran, ethanethiol, 5-methyl-2(5H)-thiophenone, 1-methyl-5-mercaptotetrazole, 4-pentyl-pyridine, 2-pentyl-thiophene, and 2-mercaptopropanoic acid were virtually ¹³C₁-¹³C₄ labeled, suggesting an origin from both glucose and cysteine and/or (E)-2-nonenal carbons. Thus, the relative contribution of aldehyde to the C-skeleton of a particular aroma compound changed substantially when both glucose and cysteine were involved in its formation.

Meat flavor generation from different composition patterns of initial Maillard stage intermediates formed in heated cysteine-xylose-glycine reaction systems

Volatile compounds formed in model reactions involving synthesized initial Maillard intermediates Gly-Amadori and [¹³C₅]-2-threityl-thiazolidine-4-carboxylic acids ([¹³C₅]-TTCA) in different molar ratios and free cysteine and glycine were investigated by solid-phase microextraction/gas chromatography-mass spectrometry and gas chromatography-olfactometry. The 1:1 ratio composition pattern provided the highest yields of all the sulfur-containing compounds, the potent meaty flavors or their ¹³C-labeled/unlabeled fractions, indicating a moderate level of glycine relative to cysteine was optimum for maximally yielding meaty flavors in complex meat-like Maillard systems containing cysteine as well as glycine. In addition, the 1:1 ratio composition led to formation of ¹³C-labeled molecules of some key meaty flavors e.g. 2-furanthiol representing over 70%, indicating TTCA/glycine reaction was better than Gly-Amadori/cysteine to yield meaty flavors. Formation pathways of twenty-nine flavors were elucidated based on the detected isotope distribution patterns. In particular, 2-methyltetrahydrothiophen-3-one, 3-thiophenethiol, 2-ethylthiophene, 2,5-dimethylthiophene, and 5-methylthiophene-2-carboxaldehyde involved a new formation pathway. Thiophene-2-carboxaldehyde and 2-methylthieno[3,2-b]thiophene showed two formation pathways.

GC-O-MS technique and its applications in food flavor analysis

Gas chromatography-olfactometry-mass spectrometry (GC-O-MS) is a combination of gas chromatography-olfactometry (GC-O) and gas chromatography-mass spectrometry (GC-MS). GC-O-MS technique is a powerful tool to study food flavors and it has been widely applied for aroma and flavor analysis of various food items. In combination with different technologies, GC-O-MS can be applied to solve many flavor problems in the food industry such as quick mapping of aroma-active compounds, identification of key aroma-active compounds, cluster analysis based on the aroma-active compounds, relationship between odorants and sensory properties, and clarification of formation mechanism of important odorants. The newly proposed "molecular sensory science" concept (or sensory-directed flavor analysis) provides a much deeper research for the GC-O-MS application. Here, we have reviewed the operation, advantages and applications of GC-O-MS technique. Qualitative/quantitative analysis methods and sampling methods of aroma-active compounds have been described to introduce the different application areas of GC-O-MS. Case studies based on existing papers and our research have been discussed.

Formation mechanism of aroma compounds in a glutathione-glucose reaction with fat or oxidized fat

Glutathione and glucose with or without chicken fat/oxidized chicken fat were thermally reacted for generation of stewed meat-like aroma, where 42 sulfur-containing odorants were identified by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-olfactometry (GC-O). The observed effects or interactions on meat flavor formation due to the fats were similar to previous reports of cysteine-reducing sugar reactions. Carbohydrate module labeling approach demonstrated ten alkyl chain compounds were indeed resulted from the lipid degradation-Maillard reaction interactions, whereas the fats had little effect on formation pathways of compounds only derived from the Maillard reaction. Formation pathways of 26 potent aroma compounds were proposed, particularly, involving two benzene derivatives and seven complex thiophenes. Notably, it was found for the first time just 2-ethylthiophene could result from both an intact skeleton of glucose and the lipid degradation product of 2,4-hexadienal, and the carbohydrate modules methylglyoxal and hydroxyacetone could arise from the glutamic acid of GSH.

Effect of fermentation modes on nutritional and volatile compounds of Huyou vinegar

Semi-solid static mode was applied to brew Huyou (Citrus changshanensis) vinegar, called HV-SS, and changes of main nutrients, volatile compounds and antioxidant capacity at different brewing stages, i.e. Huyou puree (HP), Huyou wine (HW) and HV-SS, were investigated. Meanwhile, all these parameters of HV-SS and Huyou vinegar brewed by liquid static mode (HV-LS) were compared. The contents of the main nutrients except for vitamin C (Vc) and reducing sugar increased significantly after fermentation from HP to HV-SS. DPPH radical-scavenging capacity and reducing power of HW was the highest and ABTS⁺ scavenging capacity of HV-SS was the highest. Acids, flavonoids, phenolics and Vc jointly played important roles in the antioxidant capacity of HV-SS. Forty-six aroma compounds were detected in HP and alcohols were the principal components (15 alcohols accounted for 46.2%). During HW fermentation, most of the compounds in HP (d-limonene, hexanal, hexanol and 3-hexen-1-ol) were nearly disappeared, and some new alcohols, esters and alkanes were formed, being the abundant compounds in HW and accounting for 62.99%, 18.44% and 10.52% respectively. There were 51 aroma compounds detected in HV-SS and 10 more than those in HV-LS. The types or contents of esters (22.13%), acids (50.49%) and aldehydes (7.33%) in HV-SS were markedly different from those in HP, HW and HV-LS, giving the unique aroma and good flavor to HV-SS. Therefore, semi-solid static fermentation mode was more suitable for brewing Huyou vinegar on the aspect of balancing the nutrients characteristics and flavor compounds formation.

Discovery of Amadori-Type Conjugates in a Peptide Maillard Reaction and Their Corresponding Influence on the Formation of Pyrazines

Knowledge of the role of peptides in the Maillard reaction is rather limited. In this study, peptide Maillard reaction model systems were established. Volatile and nonvolatile MRPs (Maillard reaction products) were investigated by GC-O-MS and LC-MS. Carbohydrate module labeling (CAMOLA) experiments were performed to elucidate the carbon skeleton of these compounds. Results showed that the peptide reaction system generated more pyrazines than the free amino acid group. Several new Amadori-type conjugates were identified as novel Maillard reaction products that could greatly influence the formation of pyrazines. Our work suggested anew mechanism involving these Amadori-type conjugates and subsequent investigation revealed that the conjugates could be important intermediate products in the reaction between dicarbonyl and dipeptide. Our findings demonstrate anew pyrazine generation mechanism in the dipeptide Maillard reaction.

PRACTICAL APPLICATION

We found that a dipeptide Maillard reaction system generated more pyrazines than a reaction system composed of free amino acids. New cross-linked peptide-sugar compounds were identified and found to impact the formation of pyrazines. The results of this study may help in the preparation of thermal reaction flavors using enzymatically hydrolyzed vegetable/animal proteins, which contain a considerable amount of peptides, as one of the major reactants.

A combination of quantitative marinating and Maillard reaction to enhance volatile flavor in Chinese marinated chicken

BACKGROUND

A combination of quantitative marinating and Maillard reaction was investigated by adding d-xylose, l-cysteine and thiamine to the marinated brine of quantitative marinating, which was expected to enhance the volatile flavor of Chinese marinated chicken. Response surface methodology was used to optimize parameters, in which response was sensory evaluation scores of marinated chicken. A Box-Behnken center design was applied to the optimized added contents. The optimized contents were d-xylose (1-5‰), l-cysteine (1-5‰) and thiamine (1-3‰).

RESULTS

Analysis of variance indicated that a second-order polynomial equation could predict the experimental data well (R²  = 0.94), and sensory evaluation scores were significantly affected by the added amount of d-xylose, l-cysteine and thiamine. The optimal conditions that maximized the sensory evaluation score of Chinese marinated chicken were found to be 4.96‰ d-xylose, 2.28‰ l-cysteine and 2.66‰ thiamine (w/w). Given these optimal conditions, a number of meat-like flavor compounds such as 2-pentyl-furan, benzothiazole and 4-methyl-5-thiazoleethanol were identified by gas chromatographic-mass spectrometric analysis.

CONCLUSION

Our results suggested that a combination of quantitative marinating and Maillard reaction might be a promising method to enhance the volatile flavor, especially meat-like flavor, of Chinese marinated chicken. © 2016 Society of Chemical Industry.

Improvement of ACE inhibitory activity of casein hydrolysate by Maillard reaction with xylose

BACKGROUND

The Maillard reaction is widely used to improve the functional properties or biological activities of food. The purpose of this study was to investigate the effect of the Maillard reaction on angiotensin I converting enzyme (ACE) inhibitory activity in a casein hydrolysate-xylose system.

RESULTS

Two-step hydrolysis was used to prepare casein ACE inhibitory peptides. Maillard reaction products (MRPs) were prepared by heating hydrolyzed casein with xylose at pH 8.0, 110 °C for up to 16 h. The results showed that the content of free amino group decreased (P < 0.05); however, browning intensity and absorbance at 294 nm increased because of the Maillard reaction (P < 0.05). The ACE inhibitory activity improved greatly within 2 h (from 63.48% to 90.23%), which was mainly due to carbonyl ammonia condensation reaction in the MRPs.

CONCLUSION

The study shows that the Maillard reaction under appropriate conditions can improve the ACE inhibitory activity of casein hydrolysate effectively.