Melanoidins present in traditional fermented foods and beverages

Unraveling the mysteries of melanoidins: insights into formation, structure, and health potential in fermented blacken foods

Fermentation is widely known for its ability to enhance the food nutritional ingredients, and its products are with improved texture, flavor, and nutritional. Fermented blacken foods (FBF) are a unique group of foods characterized by their darker hue while retaining nutritional benefits. Despite their popularity, research on melanoidins, the compounds responsible for the characteristic color and health-promoting properties of FBF, remains limited. This review summarizes the formation, extraction, purification, structural features, and health benefits of melanoidins in FBF. The relationship between preparation methods, and physicochemical properties and bioactivities was elucidated. The formation of melanoidins in FBF, influenced by the Maillard reaction (MR) and microbial metabolic activity is analyzed, highlighting the dynamic nature of melanoidin synthesis in fermentation systems. Furthermore, the review addresses the characteristics of FBF production processes and the role of microorganisms and enzymes in melanoidin formation. Melanoidins in FBF exhibit diverse chemical compositions and molecular structures, influenced by precursor molecules, reaction pathways, and environmental factors. These compounds contribute to the sensory attributes, stability, and bioactivity of FBF including antioxidant, antimicrobial, and prebiotic properties. This review underscores the importance of melanoidins in FBF and their influences on food quality, nutrition, and health.

Novel Pink Pigments Produced by Thermal Interaction of Theaflavins, Theanine, and Glucose: Color Formation, Isolation, and Structural Characterization

A color-deepening effect of theaflavins on the theanine-glucose thermal reaction model was revealed. Generated chromogenic intermediates in the initial stage and an accelerated browning rate through the promoted degradation of theanine-glucose Amadori rearrangement product in the intermediate and final stages are responsible for the color-deepening effect. Four pink-to-red theaflavin-theanine intermediates were verified as theaflavinies referencing the nuclear magnetic resonance and liquid chromatography-mass spectrometry information on theaflavins and l-theanine, including one accurately identified as theaflavinie 4. Theaflavinie 4 showed two maximum absorption peaks at 401 and 506 nm with parallel intensities, which resulted in a significant dichromic color change from pale pink to orange and red. Theaflavinies also could undergo further thermal reactions to yield brown polymers under higher temperatures (130 and 140 °C). This research provided new insight into realizing thermally formed polymers during black tea processing, which may be formed by oxidation products and amino acids or proteins through non-enzymatic thermal reactions.

Structure, spectral properties and antioxidant activity of melanoidins extracted from high temperature sterilized lotus rhizome juice

Melanoidins are complex macromolecular compounds closely associated with the browning phenomenon in high-temperature sterilized lotus rhizome juice (HTSL). This study aimed to preliminarily investigate the structural properties of melanoidins extracted from HTSL. Results showed that the average molecular weight of HTSL melanoidins ranged from 1.48 to 41.40 kDa. Medium and high molecular weight melanoidins were the main contributors to the brown color of HTSL. Sugars, proteins, and phenolics were present in HTSL, among which sugar was the most abundant, with glucose being the predominant monosaccharide in acid degradation products of melanoidins. Through fluorescence and ultraviolet spectral analysis, we found that the melanoidins contained carboxyl and carbonyl compounds, as well as furan and pyran heterocyclic compounds. The infrared spectra and nuclear magnetic resonance spectra revealed a prominent sugar absorption peak, indicating that sugar was the main component of the melanoidins of HTSL. Furthermore, in vitro antioxidant experiments showed that the antioxidant activity of melanoidins was significantly positively correlated with phenolic compounds. Our results indicated that there were differences in the structural properties of melanoidins fractions with different molecular weights. MW-H fraction significantly impacted the color and antioxidant activity of HTSL.

Isolation, structural characterization and biological activity evaluation of melanoidins from thermally processed cocoa beans, carob kibbles and acorns as potential cytotoxic agents

The aim of this study was to determine the chemical structure and biological activity of melanoidin fractions derived from cocoa beans, carob kibbles, and acorns roasted at different temperature-time conditions. The results showed that plant origin and roasting conditions had significant effects on the chemical composition, structural features, and morphology of melanoidins. All tested melanoidins exhibited significant antioxidant properties in three in vitro assays. In addition, they show significant in vitro anti-inflammatory activity by reducing lipoxygenase. The results from MTT assay showed that the all studied melanoidins had a cytotoxic effect against SW-480 cells in a dose- and time-dependent manner. Furthermore, the most pronounced activity was observed for acorn melanoidins. This is a unique finding, as the specific cytotoxic effect has not been reported for cocoa, carob and acorn melanoidins, and opens up a great opportunity to develop a potential novel cytotoxic agent against deadly colon cancer in the future.

Antioxidant and antibrowning properties of Maillard reaction products in food and biological systems

Oxidative damage refers to the harm caused to biological systems by reactive oxygen species such as free radicals. This damage can contribute to a range of diseases and aging processes in organisms. Moreover, oxidative deterioration of lipids is a serious problem because it reduces the shelf life of food products, degrades their nutritional value, and produces reaction products that could be toxic. Antioxidants are effective compounds for preventing lipid oxidation, and synthetic antioxidants are frequently added to foods due to their high effectiveness and low cost. However, the safety of these antioxidants is a subject that is being discussed in the public more and more. Synthetic antioxidants have been found to have potential negative effects on health due to their ability to accumulate in tissues and disrupt natural antioxidant systems. During thermal processing and storage, foods containing reducing sugars and amino compounds frequently produce Maillard reaction products (MRPs). Through the chelation of metal ions, scavenging of reactive oxygen species, destruction of hydrogen peroxide, and suppression of radical chain reaction, MRPs exhibit excellent antioxidant properties in a variety of food products and biological systems. Also, the capacity of MRPs to chelate metals makes them as a potential inhibitor of the enzymatic browning in fruits and vegetables. In this book chapter, the methods used for the evaluation of antioxidant activity of MRPs are provided. Moreover, the antioxidant and antibrowning activities of MRPs in food and biological systems is discussed. MRPs can generally be isolated and used as commercial preparations of natural antioxidants.

Role of Proteins in the Formation of Melanoidins during Coffee Roasting

The objective of the study was to investigate structural changes in the protein-rich, high-molecular-weight fraction of coffee during roasting and their contribution to the melanoidin formation in the course of the Maillard reaction. For this purpose, high- and low-molecular-weight fractions of one raw and five coffee beans with an increased roasting degree were analyzed in terms of general (color, molecular weight, functionality, elemental composition) and specific parameters (amino acid composition, Maillard reaction products). It could be demonstrated that the high -molecular-weight fraction undergoes significant changes during roasting, where proteins appear to play an important role in melanoidin formation due to their diverse nucleophilic side chains. Modification of the amino acid side chains with known Maillard reaction products (MRPs) occurs in the early stages of roasting and decreases rapidly as color development progresses. The decrease suggests that MRPs are involved in further reactions and thus extend the functionality of the amino acid side chains, opening further possibilities for protein modification. Overall, the large number of reaction pathways leads to the formation of a well-mixed, continuous melanoidin spectrum covering a wide range of molecular masses. In this process, cross-linking and fragmentation reactions oppose each other, leading to an approximation of the molecular weight.

Isotope dilution-HPLC-MS/MS to investigate the production patterns and possible pathways of free and protein-bound AGEs and 4-MI in cookies

A qualitative and quantitative method for detecting free and protein-bound advanced glycation end products (AGEs) and 4-methylimidazole (4-MI) was established using isotope dilution-HPLC-MS/MS, and successfully applied in cookies and model systems. The effects of different temperatures (160-220 °C) on the formation of free and protein-bound AGEs and 4-MI in cookies were discussed, and the possible model systems (Maillard reaction pathway 1 using wheat gluten protein + glucose + sucrose; direct addition pathway 1 using wheat gluten protein + CML/CEL/4-MI) of protein-bound AGEs and 4-MI were verified. The results showed that the contents of protein-bound CML, CEL, and 4-MI were higher than free content with a tendency of increasing first and subsequently decreasing with temperature, reaching a maximum at 200 °C in cookies. In the model systems, the levels of protein-bound CML, CEL, and 4-MI are higher than those of free CML, CEL, and 4-MI. The protein-bound CML, CEL, and 4-MI accounted for 90.73, 87.64, and 97.56% of the total amount in the model system 1, while accounting for 68.19, 59.00, and 50.96% in the model system 2, respectively. In comparison, protein-bound CML, CEL, and 4-MI could be easily generated directly by Maillard reaction.

Bioaccessibility and Genoprotective Effect of Melanoidins Obtained from Common and Soft Bread Crusts: Relationship between Melanoidins and Their Bioactivity

Bread crust constitutes an important by-product of the bakery industry, and its utilization for the isolation of melanoidins to be used as a functional ingredient can enhance its added value and contribute to health. The aim of this study was to evaluate the bioaccessibility, bioactivity, and genoprotective effect of melanoidins derived from bread crust. Bioaccessibility was assessed in gastric, intestinal digestion, and colonic fermentation fractions. The results revealed a relationship between bioaccessible melanoidins and their type (common or soft bread). No cytotoxicity effects were observed for bioaccessible fractions, as assessed by MTT and RTA methods, and they did not affect the distribution of E-cadherin in Caco-2 cells, confirming their ability to maintain membrane integrity. Furthermore, our study demonstrated that the gastrointestinal and colonic fermentation fractions successfully transported across the intestinal barrier, without affecting cell permeability, and showed antioxidant activity on the basolateral side of the cell monolayer. Remarkably, both fractions displayed a significant genoprotective effect in Caco-2 cells. Our findings provide crucial insights into the relationship between the melanoidins and their bioactivity and genoprotective effect. These results demonstrated the potential of bioaccessible melanoidins as valuable bioactive compounds for the development of functional foods, without showing toxic effects on gastrointestinal cells.

Roles of sulfur-containing compounds in fermented beverages with 2-furfurylthiol as a case example

Aroma is a critical component of the flavor and quality of beverages. Among the volatile chemicals responsible for fragrance perception, sulfur compounds are unique odorants due to their extremely low odor threshold. Although trace amounts of sulfur compounds can enhance the flavor profile of beverages, they can lead to off-odors. Sulfur compounds can be formed via Maillard reaction and microbial metabolism, imparting coffee aroma and altering the flavor of beverages. In order to increase the understanding of sulfur compounds in the field of food flavor, 2-furfurylthiol (FFT) was chosen as a representative to discuss the current status of their generation, sensory impact, enrichment, analytical methods, formation mechanisms, aroma deterioration, and aroma regulation. FFT is comprehensively reviewed, and the main beverages of interest are typically baijiu, beer, wine, and coffee. Challenges and recommendations for FFT are also discussed, including analytical methods and mechanisms of formation, interactions between FFT and other compounds, and the development of specific materials to extend the duration of aroma after release.

A multi-omics-based investigation into the flavor formation mechanisms during the fermentation of traditional Chinese shrimp paste

The fermentation process of traditional shrimp paste is closely associated with the production of flavor substances, but the formation mechanism of key aroma components is still unclear. In this study, a comprehensively flavor profile analysis of traditional fermented shrimp paste was carried out by E-nose and SPME-GC-MS. A total of 17 key volatile aroma components with OAV > 1 contributed greatly to the overall flavor formation of shrimp paste. In addition, high-throughput sequencing (HTS) analysis revealed that Tetragenococcus was the dominant genera in the whole fermentation process. Moreover, metabolomics analysis showed that the oxidation and degradation of lipids, protein, organic acids and amino acids produced a large number of flavor substances and intermediates, which laid the foundation for the Maillard reaction in term of generating the distinct aroma of the traditional shrimp paste. This work will provide theoretical support for the realization of flavor regulation and quality control in traditional fermented foods.