• Journal of the Korean Society of Food Science and Nutrition
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• v.33 no.6
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• pp.1013-1016
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• 2004

The inhibitory effect of MRPs (Maillard reaction products) on enzymatic browning of taro was investigated. The MRPs prepared by heating glycine and glucose at 9$0^{\circ}C$ for 7 hr exhibited a strong inhibitory effect on taro polyphenol oxidase (PPO). The maximum inhibitory activity of MRPs against taro PPO was detected toward (＋)-catechin, catechol, 4-methylcatechol followed by L-$\beta$-3,4-dihydroxyphenylalanine (L-DOPA) and pyragallol as a substrate. The MRPs synthesized from fructose and glucose with glycine as a amino acid significantly reduced the taro PPO activity. MRPs prepared by higher glycine or glucose concentration showed stronger inhibition against taro PPO. Increasing reaction time of the glycine and glucose promoted the inhibitory effect of MRPs against the PPO activity of taro, whereas the color formation was gradually increased.

• Journal of Life Science
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• v.22 no.11
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• pp.1451-1455
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• 2012

The study was conducted to investigate the effect of Maillard reaction products (MRPs) on enzymatic browning of crown daisy (Chrysanthmum coronarium var. spatiosum). The MRPs prepared by heating various amino acid and sugar at $90^{\circ}C$ caused a strong inhibitory effect on crown daisy polyphenol oxidase (PPO, ${\sigma}$-diphenol oxygen oxidoreductase, EC 1.10.3.1). As the reaction time of the solution containing glycine and glucose increased at $90^{\circ}C$, the production of MRPs was increased, whereas the amounts of glycine and glucose were decreased. Accordingly, the inhibitory effect of crown daisy PPO activity by MRPs was increased as the amounts of synthesized MRPs were increased. The MRPs synthesized from the various amino acids and sugars significantly reduced the PPO activity, particularly MRPs prepared by glutamine and xylose. The Michealis-Menten constant value ($K_m$) of crown daisy PPO with catechol as a substrate was 22.0 mM, and MRPs were a noncompetitive inhibitor against crown daisy PPO.

• Korean Journal of Food Science and Technology
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• v.29 no.2
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• pp.309-313
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• 1997

Maillard reaction products (MRPs) added into a culture and the resultant bacterial growth were investigated using response surface methodology. The coefficients of determination $(R^{2})$ of response surface regression equations for bacteria were 0.9544 and 0.9578 in Bacillus subtilis and Bacillus natto, respectively. The MRPs produced at higher reaction temperature and for longer reaction time showed greater antimicrobial effect for Bacillus subtilis. Especially, the MRPs produced at temperature above $150^{\circ}C$ for 8 to 12 hrs showed the strongest antimicrobial effect. The MRPs produced at lower reaction temperature and for shorter reaction time showed greater microbial growth effect for Bacillus natto, but those produced at the reaction temperature higher than $160^{\circ}C$ showed the greatest antimicrobial effect. In the ridge analysis, the growth of Bacillus subtilis was the most significantly inhibited in the presence of MRPs prepared at $159.10^{\circ}C$ and pH 12.21 for 9.67 hrs, and the growth of Bacillus natto was the most significantly inhibited in the presence of MRPs prepared at $169.94^{\circ}C$ and pH 9.66 for 9.22 hrs.

• Preventive Nutrition and Food Science
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• v.15 no.4
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• pp.297-303
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• 2010

The present study compared the Maillard reaction products (MRPs) derived from aqueous and ethanolic fructoseglycine and its oligomer (dimer and trimer) solutions. The pH was lower in glycine (G) than in diglycine (DG) and triglycine (TG) in both aqueous and ethanolic solutions, but the pH difference between the DG and TG was not significant. MRPs derived from the DG had a greater absorbance at 294 and 420 nm in ethanolic solution than in an aqueous solution. In particular, the loss of sugar was higher in ethanolic solution than in aqueous solution. Enolization of fructose was observed in both aqueous and ethanolic MRP solutions; however, enolization was not observed for the G in aqueous MRP solutions. The glycine oligomer content in ethanolic MRP solutions remained higher than that in aqueous MRP solutions. Furthermore, neither diglycine nor triglycine were detected in the G aqueous or ethanolic MRP solutions, while triglycine was detected in both the DG aqueous and ethanolic MRP solutions. Absorption in the ultraviolet-visible (UV-Vis) spectra was higher with MRPs derived from the ethanolic solution than with those derived from the aqueous solution. MRPs derived from the DG in an ethanolic solution showed the highest absorption intensity.

• The Korean Journal of Food And Nutrition
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• v.30 no.5
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• pp.853-859
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• 2017

This study was conducted in an effort to investigate the effect of Maillard reaction products (MRPs) on enzymatic browning of burdock and their anti-oxidant activity. The MRPs were prepared by heating glucose and amino acids at $90^{\circ}C$, which served to produce a strong inhibitory effect on burdock polyphenol oxidase. As the reaction time of the solution containing glucose and amino acid increased at $90^{\circ}C$, the production of MRPs increased and intensity of the brown color deepened. When MRPs were prepared by heating at $90^{\circ}C$ for five hours, the absorbance of MRPs from glucose and lysine was 6.44, while those of glucose and glycine was 1.95. The MRPs synthesized from the glucose and lysine also reduced the pH of MRPs from 5.60 to 4.51, but those from glucose and glycine decreased slightly from 5.57 to 5.33. The Michealis-Menten constant value ($K_m$) of burdock PPO with pyrocatechol as a substrate was 16.0 mM, and MRPs were a non-competitive inhibitor against burdock PPO. The anti-oxidant activity of MRPs was measured by evaluating its radical scavenging activities of DPPH radicals, ABTS radicals and reducing power. The color intensity of MRPs produced by lysine and glucose were deeper than that produced by glucose and glycine. It was also found that MRPs produced from glucose and lysine exhibited stronger anti-oxidant properties than those produced by glucose and glycine.

• Journal of Ginseng Research
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• v.36 no.3
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• pp.256-262
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• 2012

Reactive oxygen species play critical role in kidney damage. Free radical-scavenging activities of Panax ginseng are known to be increased by heat-processing. The structural change of ginsenoside and the generation of Maillard reaction products (MRPs) are closely related to the increased free radical-scavenging activities. In the present study, we have demonstrated the Maillard reaction model experiment using ginsenoside Re and glycine mixture to identify the renoprotective effect of MRPs from ginseng or ginsenosides. Ginsenoside Re was transformed into less-polar ginsenosides, namely Rg2, Rg6 and F4 by heat-processing. The free radical-scavenging activity of ginsenoside Re-glycine mixture was increased in a temperature-dependant manner by heatprocessing. The improved free radical-scavenging activity by heat-processing was mediated by the generation of antioxidant MRPs which led to the protection of LLC-PK1 renal epithelial cells from oxidative stress. Although the free radical scavenging activities of less-polar ginsenosides were weak, they could protect LLC-PK1 cells from oxidative stress. Therefore, MRPs and less-polar ginsenosides contributed to the combined renoprotective effects against oxidative renal damage.

• Preventive Nutrition and Food Science
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• v.15 no.4
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• pp.287-296
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• 2010

This study was designed to investigate the influence of the pH and enantiomer on the antioxidant activity of Maillard reaction mixture solution in model systems. The loss of glucose in MRPs did not show different characteristics for the different amino acid enantiomers; however, the concentration of glucose decreased as the pH levels increased. The enolization of sugars was observed in all MRP samples according to increase of pH levels. In addition, D-amino acids were detected in L-amino acid systems and L-amino acids could also be observed in D-amino acid systems. Formation of the isomer was the highest in the Glc/L-Lys system. The browning development increased as pH levels increased; however, browning development did not show different characteristics based on the use of L- versus D-isomers of the same amino acid. The L- and D-isomers show different absorption values in the UV-Vis spectra, but the absorption patterns display a similar shape. The antioxidant activities of MRPs derived from the Glc/Gly, Glc/L-Asn and Glc/D-Asn systems at pH 7.0 were greater compared to those of pH 4.0 and pH 10.0. The antioxidant activities of MRPs derived from the Glc/L-Lys and Glc/D-Lys systems decreased as the pH increased. In addition, the results show that the MRPs derived from the D-isomers have similar antioxidant activities as those from L-isomer. Therefore, the MRPs have the different antioxidant activities on the basis of the pH level, but not on the basis of different amino acid enantiomers.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.7
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• pp.2522-2527
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• 2010

The aim of this study was to investigate the tyrosinase inhibitory activity and antimicrobial activity by mixtures of ultrasonicated chitosan and Maillard reaction products. Analysis of tyrosinase was purified from potato and confirmed by active staining after SDS-PAGE. Maillard reaction products (MRPs) were formed from various sugars (glucose, fructose, galactose, xylose, arabinose or ribose) and cystein. MRPs inhibited the tyrosinase purified from potato. The highest tyrosinase inhibitory activity was shown by MRP from glucose and cystein. Ultrasonicated chitosan (over 1 hr) showed antimicrobial activity at the concentration of 1% against E. coli and S. aureus. For the development of antibrowning agent with antimicrobial activity, tyrosinase inhibitory and antimicrobial activity by the mixtures of ultrasonicated chitosan and MRP were tested. 1:1 mixture of ultrasonicated chitosan and MRP from glucose and cystein was the best antibrowning agent having antimicrobial activity.

• Journal of the Korean Society of Food Science and Nutrition
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• v.38 no.1
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• pp.62-69
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• 2009

Maillard reaction products (MRPs) were produced from aqueous solution of various sugars with defatted hydrolyzed soybean protein (DFHSP) with different temperatures and pressures. Physicochemical properties of MRPs were investigated; also, DPPH and hydroxyl radical scavenging activity and sensory properties were evaluated. MRPs from ribose and DFHSP had the highest reactivity with larger pH reduce, higher browning index increase and higher antioxidant activity than other MRPs from other sugars. The antioxidant activities were increased with increasing temperatures and pressures of reaction. The highest antioxidant activity and sensory preference were obtained from MRPs with ribose at $140^{\circ}C$ with 2.8 kg/$cm^2$ for 30 mins.

• Korean Journal of Food Science and Technology
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• v.41 no.2
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• pp.122-130
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• 2009

Maillard reaction products (MRPs) were produced from aqueous solution of various sugars with hydrolyzed wheat gluten (HWG) with different temperatures, pressures, pH values and solvents. The physicochemical properties of MRPs were investigated and DPPH and hydroxyl radical scavenging activity and sensory properties were also assessed. MRPs from ribose and HWG evidenced the highest preference for meaty flavor and antioxidant activity and also evidenced higher antioxidant activity with larger pH reductions and higher browning index increases than were observed in other MRPs. The antioxidant activities were increased with increased reaction temperature and pressure. The most preferred meaty flavor was obtained from MRPs with ribose at 140$^{\circ}C$ in an oil bath with the pH adjusted to 9 in water as a solvent, and heated for 30 mins.