Progress on the melanoidins produced by the Maillard reaction of fermented food and traditional Chinese medicine

FMs(Food-borne melanoidins)are brown high molecular weight polymers formed by the Mailiard reaction between carbohydrates and nitrogen-containing compounds during the processing of food or Traditional Chinese Medicine(TCM),and are widely found in food-borne products such as TCM concoctions,bakery,brewing,soy sauce,ferment and other food-borne products.FMs not only have a variety of biological activities,such as antioxidant,antibacterial,immunomodulation,regulation of intestinal flora,etc.,and can change the color,aroma and taste of food.The diversity of its components has become a research hotspot at home and abroad in recent years,with a wide range of application prospects.Therefore,this paper summarizes the existing information on FMs at home and abroad,mainly describes their preparation process,physicochemical properties,structural characteristics and functional activity research progress.Typical FMs,such as coffee,biscuits,wine and soy sauce in daily food,and Polygonatum,Perilla oil,Black ginseng,and Red jujube in T,were highlighted.Summarising the current status of research between the chemistry and pharmacodynamics of relevant FMs and presenting challenges and future recommendations for melanoidin research.In future research on FMs,one should pay more attention to basic research,especially isolation and purification and generation mechanisms,to further demonstrate the biological activity of FMs in vivo and in clinical trials.Thus,the potential value of its existence is deeply exploited to meet the needs of technology,production and health.

Decolorization of molasses melanoidins and palm oil mill effluent phenolic compounds by fermentative lactic acid bacteria

Lactobacillus plantarum SF5.6 is one of the lactic acid bacteria （LAB） that has the highest ability of molasses melanoidin （MM） decolorization among the 2114 strains of LAB. The strains were isolated from spoilage, pickle fruit and vegetable, soil and sludge from the wastewater treatment system by using technical step of enrichment, primary screening and secondary screening. This LAB strain SF5.6 was identified by 16S rDNA analysis and carbohydrate fermentation （API 50 CH）. The top five LAB strains having high MM decolorization （ 55%）, namely TBSF5.8-1, TBSF2.1-1, TBSF2.1, FF4A and SF5.6 were selected to determine the optimal condition. It was found that the temperature at 30°C under facultative conditions in GPY-MM medium （0.5% glucose, 0.1% peptone, 0.1% yeast extract, 0.1% sodium acetate, 0.05% MgSO4 and 0.005% MnCl2 in MM solution at pH 6） giving a high microbial growth and MM decolorization for all five strains. It was noticed that the decolorization of MM by LAB strains might be cell growth associated. L. plantarum SF5.6 grew rapidly within one day while the other strains took 2–3 days. This L. plantarum SF5.6 could rapidly decolorize MM to 60.91% without any lag phase, and it also had the ability to remove 34.00% phenolic compounds and 15.88% color from treated palm oil mill effluent.

Chemical Reactivity Theory (CRT) Study of the Melanoidin M8: Local Conceptual Density Functional Theory Descriptors

This study evaluated a fixed long-range corrected range-separated hybrid (RSH) density functional associated with the Def2TZVP basis set alongside the Solvation Model based on Density (SMD) for the computation of the structure, molecular properties and chemical reactivity of the M8 intermediate melanoidin pigment. The preference of the active sites pertinent to radical, nucleophilic and electrophilic attacks is made through linking them with the electrophilic and nucleophilic Parr functions, Fukui function indices, and condensed Dual Descriptor. This study showed that the MN12SX density functional is the most suitable one for predicting the chemical reactivity of this system.

Near-Infrared Light-Activatable Melanized Paclitaxel Nano-Self-Assemblies for Synergistic Anti-tumor Therapy

Building self-assembly nanostructures is an important way to overcome the limitations of paclitaxel in tumor therapy.However,this strategy is also faced with challenges,such as difficulties in efficient release and the potential for drug resistance.Herein,we developed a near-infrared light-activatable melanized paclitaxel self-assembly nanoparticles for synergistic anti-tumor therapy.In this strategy,paclitaxel dimer prodrugs were synthesized and paclitaxel nanoparticles were obtained through self-assembly.Finally,the paclitaxel dimer nanoparticles were capped with polydopamine(PDA,melanoidin)and human serum albumin(HSA).The disulfide bonds in paclitaxel dimeric prodrug specifically respond to high concentrations of glutathione(GSH)and reactive oxygen species(ROS)in tumor cells.PDA enhances the biocompatibility of the drug molecules and imparts near-infrared photothermal conversion capability to the nano-self-assemblies.Both the in vitro and in vivo experiments demonstrated that this paclitaxel nanoprodrug exhibited enhanced tumor therapeutic efficacy under near-infrared light irradiation.

Optimizing food waste hydrothermal parameters to reduce Maillard reaction and increase volatile fatty acid production

The occurrence of the Maillard reaction and melanoidins formation during the hydrothermal treatment of food waste can reduce the yield of volatile fatty acids(VFA);however, few studies have investigated the adverse effects of the Maillard reaction. This study identified the impact of hydrothermal treatment parameters on hydrolysis and melanoidins formation and optimized the hydrothermal treatment conditions to enhance VFA production by minimizing the impact of the Maillard reaction. A response surface methodology was employed to optimize the hydrothermal treatment parameters and VFA production was evaluated. Results showed that temperature, reaction time, and pH were significant interacting factors with respect to hydrolysis and melanoidins formation while the C/N ratio and moisture content of food waste had little impact. The optimal conditions for hydrothermal treatment(temperature of 132 °C, reaction time of 27 min, and a pH of 5.6) enhanced VFA production by 22.1%. Under optimal hydrothermal treatment conditions, a higher initial C/N ratio further increased VFA production.

Fate of proteins of waste activated sludge during thermal alkali pretreatment in terms of sludge protein recovery

Proteins are the major organic component s of waste activated sludge(WAS);the recovery of sludge proteins is economically valuable.To efficiently recover sludge proteins,WAS should undergo hydrolysis pretreatment to fully release proteins from sludge flocs and microbial cells into aqueous phase.One of the most widely used chemical methods for that is thermal alkali hydrolysis(TAH).Here,the soluble protein concentration achieved the highest level over 90 min of TAH pretreatment at 80°C;the sludge floc disintegration and microbial cell destruction were maximized according to the content profiles of bound extracellular polymeric substance(EPS)and ribonucleic acid(RNA)of sludge.Both less proteins broken down to materials with small molecular weight and less melanoidin generated were responsible.TAH pretreatment at 80°C for 90 min resulted in the solubilization of 67.59% of sludge proteins.34.64% of solubilized proteins was present in soluble high molecular;1.55% and 4.85% broke down to polypeptides and amino acids.The lost proteins via being converted to ammonium and nitrate nitrogen accounted for 9.44% of solubilized proteins.It was important to understand the fate of sludge proteins during TAH pretreatment in terms of protein recovery,which would be helpful for designing the downstream protein separation method and its potential application.

Effect of heavy metals and phenol on bacterial decolourisation and COD reduction of sucrose-aspartic acid Maillard product

Melanodins are amino-carbonyl complex, predominantly present in sugarcane molasses based distillery wastewater as major source of colourant. The microbial decolourisafion of melanoidin is a challenge due to its binding property with other co-pollutants of distillery waste. Results revealed that the presence of Zn2＋ （2.00-20.00 mg/L） in melanoidin solution （1200 mg/L） stimulated the bacterial growth and sucrose-aspartic acid Maillard product （SAA） decolourisation as compared to control, while Fe3＋ and Mn2＋ at the same concentration inhibited the process. However, the presence of phenol （100 mg/L） along with Zn2＋, Fe3＋ and Mn2＋ suppressed the bacterial growth, SAA decolourisation and MnP activity. The shrinkage and reduced number of bacterial cell count at higher concentration of heavy metals in presence of phenol was also observed under scanning electron microscope.