Amino Acids Inhibitory Effects and Mechanism on 2‐Amino‐1‐Methyl‐6‐Phenylimidazo [4,5‐b]Pyridine (PhIP) Formation in the Maillard Reaction Model Systems

This study was to investigate the inhibitory effects of amino acids (AAs) on the formation of 2‐amino‐1‐methyl‐6‐phenylimidazo [4,5‐b]pyridine (PhIP) and to evaluate the inhibition mechanism of PhIP in Maillard model systems. Different AAs were individually added into model systems heat‐treated at 180 °C/1 h. The PhIP, phenylacetaldehyde (PheAce), and pyrazines derivatives were determined using HPLC and GC‐MS. AAs significantly reduced (P < 0.05) PhIP levels in a dose‐dependent response, ranking as: Trp = Lys > Pro > Leu > Met > Val > Ile > Thr > Phe > Asp, at the highest molar ratio. The PheAce content was gradually reduced with increasing AAs levels, suggesting that AAs may inhibit PhIP formation through scavenging the available PheAce. A correlation between PhIP inhibition and PheAce‐scavenging activity of AAs was observed when PheAce and AAs were heated. The variety and quantity of pyrazines formed are highly depending on the type of AAs.     

Degradation of N‐(1‐Deoxy‐d‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐xylulos‐1‐yl)proline using thermal treatment

The formation and degradation of N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d ‐xylulos‐1‐yl)proline, derived from the secondary amine Maillard reaction in xylose‐amino acid model solutions, were detailed in this study. The identification and quantitative analysis of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline were carried out using high‐performance anion‐exchange chromatography and high‐performance liquid chromatography. The formation of intermediate and advanced products derived from N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline was also tested using an UV‐Vis spectrophotometer to gain a better comparing of the degradation process of the two important Maillard reaction products using thermal treatment. Results showed that the degradation of N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine was more significant than N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline. Moreover, xylose was tested in the degradation products of both N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)glycine and N‐(1‐Deoxy‐d‐ xylulos‐1‐yl)proline, which indicated that the degradation of N‐substituted 1‐amino‐1‐deoxyketoses was a reversible reaction to form reducing sugar.     

Interaction between Maillard reaction products and lipid oxidation in starch‐based model systems

The effect of Maillard reaction products (MRPs) on the kinetics of lipid oxidation in intermediate‐moisture model systems containing pregelatinised starch, glucose, lysine and soybean oil has been studied. The samples, either containing all components or excluding one or more of them, were heated at 100 °C for different times. Lipid oxidation and browning indices were measured and the results confirmed the ability of MRPs to retard peroxide formation. Under the conditions adopted, the rate of the Maillard reaction was increased by the presence of the oil and its oxidation products. The antioxidant action of MRPs was also evaluated using a peroxide‐scavenging test based on crocin bleaching. The results demonstrated that antioxidant activity developed with increased browning of the samples. © 2000 Society of Chemical Industry     

Phytosterols in banana (Musa spp.) flower inhibit α‐glucosidase and α‐amylase hydrolysations and glycation reaction

Three phytosterols were isolated from Musa spp. flowers for evaluating their capabilities in inhibiting glucosidase and amylase activities and glycation of protein and sugar. The three phytosterols were identified as β‐sitosterol (PS1), 31‐norcyclolaudenone (PS2) and (24R)‐4α, 14α, 4‐trimethyl‐5α‐cholesta‐8, 25(27)‐dien‐3β‐ol (PS3). IC₅₀ values (the concentration of inhibiting 50% of enzyme activity) of PS1, PS2 and PS3 against α‐glucosidase were 283.67, 11.33 and 43.10 μg mL^?1, respectively. For inhibition of α‐amylase, the IC₅₀ values of PS1, PS2 and PS3 were 52.55, 76.25 and 532.02 μg mL^?1, respectively. PS1 was an uncompetitive inhibitor against α‐amylase with K_m at 5.51 μg mL^?1, while PS2 and PS3 exhibited a mixed‐type inhibition with K_m at 52.36 and 2.49 μg mL^?1, respectively. PS1 and PS2 also significantly inhibited the formation of advanced glycation end products (AGEs) in a BSA–fructose model. The results suggest that banana flower could possess the capability in prevention of the diseases associated with abnormal blood sugar and AGEs levels, such as diabetes.     

Influence of Maillard reaction conditions on the antigenicity of bovine α‐lactalbumin using response surface methodology

BACKGROUND: Maillard reaction can modify functional properties of proteins. Bovine α‐lactalbumin (α‐LA) is often supplemented to the new generation of infant formulae, but it is considered to be a main allergen. However, there is little information on the effect of Maillard reaction on α‐LA antigenicity. The objective of this study was to investigate the influence of Maillard reaction on the antigenicity of α‐LA in conjugates of whey protein isolate (WPI) with glucose under different conditions of protein/sugar weight ratio (0.17–7.83), temperature (40–60 °C) and time (24–120 h) using response surface methodology. RESULTS: Conjugation of WPI with glucose markedly reduced the antigenicity of α‐LA. This reduction in antigenicity could be controlled by regulating the three independent variables weight ratio, temperature and time. A model of optimal reaction conditions for lower antigenicity of α‐LA was established. According to the model, the minimum antigenicity of α‐LA was achieved at 52.8 °C, 78 h and 5.96:1 WPI/glucose weight ratio. WPI/glucose weight ratio had the greatest effect on the antigenicity of α‐LA, while reaction temperature influenced α‐LA antigenicity to a lesser extent. CONCLUSION: Well‐controlled Maillard reaction between WPI and glucose is an efficient method to reduce α‐LA antigencity. Copyright © 2009 Society of Chemical Industry     

Formation of 4‐Hydroxyfuranones and their Precursors during Production of Worts and Beers

Laboratory beers and samples taken at each stage of production, were analysed for the flavour active 4‐hydroxyfuranones; 5‐methyl‐4‐hydroxy‐3(2H)‐furanone (MHF), 2,5‐dimethyl‐4‐hydroxy‐3(2H)‐furanone (DMHF) and 5‐(or 2)‐ethyl‐2(or 5)‐methyl‐4‐hydroxy‐3(2H)‐furanone (EMHF). The length and temperature of mashing, the length of boiling, the rate of cooling the worts and the effects of grist composition were investigated to identify the 4‐hydroxyfuranone content of worts and subsequent beers. Fermentation temperature and the use of the stabilising agents, PVPP and Lucilite PC5, on the 4‐hydroxyfuranone content of the beer was also investigated. The results demonstrated that several aspects of beer production procedures affect the furanone content of the beer, but in practice the important factors are grist composition, the rate at which the boiled wort is cooled and fermentation temperature. Fermentation has a major effect on final furanone content as yeast produces both DMHF and EMHF. The results suggest that malt levels of precursor compounds, which can be converted to 4‐hydroxyfuranones by the Maillard reaction or by yeast, may prove to be more important than the quantities of the furanones found in malt in determining the final furanone content of beer. A clearer understanding of the nature of the precursors should allow manipulation of their production and beer furanone content.     

Variation in 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and fructo‐oligosaccharide (FOS) status in onion bulbs. Influence of temperature and storage time

Effects of storage temperature and duration on 1‐fructo‐exohydrolase (1‐FEH) and 1‐kestose‐hydrolysing (1‐KH) activities and trisaccharide (Tri) and fructo‐oligosaccharide (FOS) status in onion bulbs var Tenshin kept for 24 weeks at 10 and 20 °C were investigated. 1‐FEH activity peaked sharply after 10 weeks and seemed to be triggered by a decrease in sucrose content. 1‐KH activity increased during the first 8 weeks and remained stable during the last 8 weeks. Contents of Tri, FOS and total FOS decreased abruptly during the first 8 weeks; however, at 10 °C, contents of Tri, FOS (DP 3–12) and total FOS were lower than those at 20 °C. The consumption rate of fructo‐oligosaccharides also appeared to be higher at 20 °C than at 10 °C, despite the slight degradation in activities observed at this low temperature. 1‐FEH seems to be under the control of a triggering signal which induces its activity, and sucrose seems to be this biochemical signal which initiates dormancy release and the onset of sprouting, as found previously. Thus changes in carbohydrates seem to be a strong indicator of the end of the dormant state of the bulb and the beginning of the sprouting period. Copyright © 2004 Society of Chemical Industry     

Glycation of caseinate by fructose and fructo‐oligosaccharides during controlled heat treatment in the ‘dry’ state

This paper investigates the controlled heating of caseinate with reducing sugars to produce glycoproteins with improved functionality for use in food. Caseinate was combined with inulin, fructose and a mixture of both inulin and fructose and the lyophilisates heated at a controlled water activity for up to 48 h. Caseinate–glucose and caseinate–lactose glycoconjugates were prepared for comparison. Conjugation between caseinate and fructose occurred readily at 60 °C and 67% relative humidity, modifying up to 75% of the lysine groups of caseinate within 48 h. Moreover, when reconstituted, the caseinate–fructose glycoconjugates showed a dramatic increase in viscosity relative to caseinate ‘dry’‐heated alone. At 80% relative humidity the reaction proceeded so rapidly that gels containing darkly coloured particulate matter were formed. Incorporation of inulin prevented formation of caseinate–fructose gels, and minimised browning development while still producing moderately viscous solutions. Based on ¹³C‐NMR, SDS‐PAGE and electron microscopy techniques, mechanisms by which inulin modified the reaction have been proposed. Copyright © 2005 Society of Chemical Industry     

Emulsifying properties and structural characteristics of β‐conglycinin and dextran conjugates synthesised in a pressurised liquid system

The purpose of this study was to characterise the Maillard reaction in a pressurised liquid system containing β‐conglycinin and dextran. The rate of browning and the free amino content in this liquid system, with an initial pH of 7.2, were measured after reaction under atmospheric pressure and at 10 MPa. The secondary and tertiary structures of the conjugates were analysed by circular dichroism, showing that the increased pressure accelerated the reaction rate of the free amino groups and reduced the rate of browning. Significant structural changes occurred in the tertiary structure of the conjugates. Additionally, the emulsifying properties of the β‐conglycinin–dextran conjugates produced were studied. The emulsifying properties of the conjugates produced at 10 MPa were higher than those made at atmospheric pressure.     

Validation of analytical method for α‐dicarbonyl compounds using gas chromatography–nitrogen phosphorous detector and their levels in alcoholic beverages

This study aimed to establish an analytical method for α‐dicarbonyl compounds (α‐DCs) including glyoxal, methylglyoxal and diacetyl, to determine the content of α‐DCs in 101 various alcoholic beverages using gas chromatography–nitrogen phosphorous detector (GC‐NPD) and to perform exposure assessment. The limit of detection and limit of quantification for α‐DCs were 0.05–0.22 and 0.15–0.70 μg g^?1, respectively. The accuracy and precision were validated in five matrices. The raspberry fruit wine had the highest value at 139.74 μg g^?1 total α‐DCs. The lowest α‐DC concentration among the beverages was detected in rice wine (Makgeolli) at 1.59 μg g^?1. The levels of α‐DCs in various samples were detected as follows: 1.59–56.68 μg g^?1 in rice wine (Makgeolli), 2.73–16.77 μg g^?1 in beer, 8.22–139.74 μg g^?1 in fruit wine and 8.17–91.56 μg g^?1 in rice wine (Cheongju). The estimated daily intake of α‐DCs in the intake‐only group and population group was calculated as 4.22–97.94 μg kg^?1 bw day^?1 and 0.28–7.13 μg kg^?1 bw day^?1, respectively.     

Emulsification properties of sodium caseinate‐based conjugates with selected polysaccharides

Sodium caseinate (SC) was conjugated with polysaccharides, viz. maltodextrin (MD), pectin (P) and gum arabic (GA) at protein:polysaccharide weight ratio of 1:2, 1:1 and 2:1. The emulsifying properties and other relevant chemical properties of these conjugates were compared. The visible colour change, SDS‐PAGE analysis and available reducing groups confirmed greater conjugation in SC‐MD conjugate than the SC‐GA and SC‐P conjugates. SC‐P conjugate at the weight ratio of 1:2 exhibited the best emulsifying properties (emulsifying activity – 46.7%, emulsion stability – 7 days at 5 ± 1 °C storage) and had better solubility (33.5%) near the iso‐electric pH.     

Kinetic Study on Peptide‐Bound Pyrraline Formation and Elimination in the Maillard Reaction Using Single‐ and Multiple‐Response Models

Pyrraline, an advanced glycation end product (AGE), is related to some chronic diseases and can be employed as an indicator for heat damage in food processing. In this study, the impact of changing the reactant concentration and ratio on the kinetic parameters describing peptide‐bound pyrraline (pep‐pyr) formation and elimination was evaluated in the Lys‐Gly/glucose model systems, with microwave heating treatment ranging from 120 to 200 °C. The maximum pep‐pyr concentration increased as follows: 200 °C ? 180 °C ? 160 °C ? 120 °C ? 140 °C. First, the pep‐pyr formation and elimination was modeled by using a single‐response modelling. The formation rate constant (k_F) of pep‐pyr was independent of the initial concentration of the reactants and ratios. However, the elimination rate constant of pep‐pyr (k_E) increased with increasing reactant concentrations. Second, a multiresponse modelling was performed to illustrate the pathways of pep‐pyr formation and elimination. Two adapted models can fit to the experimental data with the goodness‐of‐fit ranging from 0.663 to 0.920. Glucose‐to‐fructose isomerization rather than glucose‐to‐mannose epimerization was detected in an equimolar model system and the model system with an excess of any of the reactants. The caramelization reaction was negligible in the equimolar systems and the model systems with an excess of peptide. The reaction rate constant of glucose‐to‐fructose isomerization was independent of the initial reactant ratios. It was more difficult for pep‐pyr elimination in the model system with an excess of peptide than that in the other 2 model systems (the equimolar system and the system with an excess of glucose), whereas a reverse result in pep‐pyr formation was obtained.     

Radical-Scavenging Activity and Brightly Colored Pigments in the Early Stage of the Maillard Reaction

ABSTRACT: The relationship of radical-scavenging activity and formation of brightly colored pigments in the early stage of the Maillard reaction was investigated. The Maillard reaction products of xylose with glycine, histidine, and arginine formed blue, yellow, and red color pigments, respectively, in the early stage. Although radical-scavenging activity was found in the early stages of the Maillard reaction, the scavenging activity appeared before the formation of the pigments. The radical-scavenging activity in the early stage of the Maillard reaction was derived from uncolored reaction products smaller than the brightly colored pigments.     

The inhibition effects of reactive oxygen species by Maillard reaction products in Caco‐2 cells

Maillard reaction products (MRPs) were prepared by heating a mixture of rice starch with different dextrose equivalents (DE 10, 30, 50 and 70) and glycine. The glycine was added to the sample pastes at the same molar concentration as the sugar contained in each sample. As the dextrose equivalent of rice starch increased, the browning intensity and fluorescence of the MRPs increased. The antioxidant properties of the MRPs were investigated by DPPH radical scavenging activity, reducing power, and phenolic content in a chemical system, and were evaluated by measuring reactive oxygen species levels and antioxidant enzymes activities in Caco‐2 cells. The darkest MRPs, MRPs‐4, showed the highest antioxidant activity and phenolic content among the samples; in addition, it inhibited the cellular oxidative stress. The decrease of cell viability and antioxidant enzymes activities caused by reactive oxygen species and apoptosis were recovered by MRPs‐4. Actually, the addition of the MRPs suppressed apoptosis by decreasing the proportion of cells in the sub‐G1 phase. Therefore, these MRPs, as compounds formed by the Maillard reaction, are considered to possess an effective antioxidant activity against oxidizable substrates.     

Antioxidant capacity of Maillard reaction products’ fractions with different molecular weight distribution from chicken bone hydrolysate – galactose system

Maillard reaction products (MRP) were prepared from an aqueous chicken bone hydrolysate (CBPH) – galactose systems by heating at 100 °C for up to 7.5 h without pH control, and then separated into the <3‐, 3‐ to 10‐ and >10‐kDa fractions using ultrafiltration. Antioxidant capacity and spectral properties of these MRP fractions were studied. The scavenging activity towards DPPH and hydroxyl radicals as well as reducing power of each MRP fraction increased with the heating time, in accordance with the increase in UV absorbance, browning and fluorescence intensity. For the same MRP, the fraction with high molecular weight (MW) demonstrated the stronger radical scavenging activity and reducing power than that with low MW. Radical scavenging activities of MRP fractions largely depended on their MW, while their reducing powers were more related to the reaction progress. These results suggested that antioxidant capacity of MRP fractions should be positively related to its molecular size.