Development of the Maillard reaction in foods cooked by different techniques. Intake of Maillard-derived compounds

Specific and non-specific Maillard reaction (MR) indices such as CIELab colour, browning measurement, furosine, hydroxymethylfurfural (HMF) and furfural, as well as the nutrient content, were analysed for commonly consumed dishes, to test the effects of different culinary treatment on dishes composed of the same ingredients. In addition, the consumption of early MR products (MRP), Amadori compounds, HMF and furfural from a normal serving of these dishes was calculated. As expected, recipes including frying, apart from their particular composition, led to significantly higher values of furosine and HMF, ranging from 4.40 to 175 and from 0.30 to 22.7 mg/kg, respectively; consequently they provided the highest levels of Amadori compounds and HMF intake (0.42–26.8 and 0.02–2.38 mg/serving, respectively). Even so, MRP intake/serving was not very high in comparison with levels reported in the bibliography on some individual foods typically studied in terms of MR development, suggesting that the culinary treatments used do not make a great contribution to the daily MRP consumption.     

Optimisation of resistant starch II and III levels in durum wheat pasta to reduce in vitro digestibility while maintaining processing and sensory characteristics

Foods with elevated levels of resistant starch (RS) may have beneficial effects on human health. Pasta was enriched with commercial resistant starches (RSII, Hi Maize™ 1043; RSIII, Novelose 330™) at 10%, 20% and 50% substitution of semolina for RSII and 10% and 20% for RSIII and compared with pasta made from 100% durum wheat semolina to investigate technological, sensory, in vitro starch digestibility and structural properties. The resultant RS content of pasta increased from 1.9% to ∼21% and was not reduced on cooking. Significantly, the results indicate that 10% and 20% RSII and RSIII substitution of semolina had no significant effects on pasta cooking loss, texture and sensory properties, with only a minimal reduction in pasta yellowness. Both RS types lowered the extent of in vitro starch hydrolysis compared to that of control pasta. X-ray diffraction and small-angle scattering verified the incorporation of RS and, compared to the control sample, identified enhanced crystallinity and a changed molecular arrangement following digestion. These results can be contrasted with the negative impact on pasta resulting from substitution with equivalent amounts of more traditional dietary fibre such as bran. The study suggests that these RS-containing formulations may be ideal sources for the preparation of pasta with reduced starch digestibility.     

Identification of key aroma compounds generated from cysteine and carbohydrates under roasting conditions

 Application of the aroma extract dilution analysis to volatile fractions obtained from dry-heated (180  °C for 6 min on silica) mixtures of cysteine and ribose (I), glucose (II) or rhamnose (III) revealed the following compounds with the highest flavour dilution factors: 2-furfurylthiol (FFT) and 2-acetyl-2-thiazoline in I; 2-acetyl-2-thiazoline, 2-propionyl-2-thiazoline and FFT in II; 5-methyl-2-furfurylthiol, 4-hydroxy-2,5-dimethyl-3(2H)-furanone, 2-acetyl-2-thiazoline, 2-propionyl-2-thiazoline and (Z)-2-propenyl-3,5-dimethylpyrazine in III. A comparison of the data with results of previous studies, in which the same mixtures had been reacted under aqueous conditions (145  °C, 20 min) revealed that the dry-heating process favoured the formation of the roasty, popcorn-like smelling 2-acetyl- and 2-propionyl-2-thiazoline as well as the potato-chip-like 2-ethyl-3,5-dimethylpyrazine and 2,3-diethyl-5-methylpyrazine in all three reaction systems. 2-Ethenyl- and (Z)-2-propenyl-3,5-dimethylpyrazine, both having an intense roast potato smell were, however, selectively formed in the presence of ribose or rhamnose, respectively. Based on quantitative data, pathways generating the latter two pyrazines via their 1-desoxyosones as key intermediates are discussed. Received: 11 March 1998     

Evaluation of thermal treatment markers in wheat flour-derived products cooked in conventional and in low-emissivity ovens

Different markers for the assessment of thermal treatment entity of food products were investigated on a model bread prepared from wheat flour. Samples were submitted to different cooking procedures by combining three different times and temperatures, and employing two different ovens: a low-emissivity oven and a conventional one. The cook value index was calculated for each sample to evaluate the entity of the thermal treatment. Furosine, maltose:maltulose ratio, colour indexes (L, a, b) have been evaluated in all samples. Furosine has been quantified by capillary electrophoresis–mass spectrometry, maltose:maltulose ratio was determined by HPAEC-PAD, colour indexes were measured by spectrophotometer method. Values for weight loss during cooking and surface temperature have also been monitored. A statistical analysis showed good correlation between the cook value index and all the parameters evaluated. Low emissivity oven shown higher performances and lower energy consumption than conventional oven.     

Study of the Maillard reaction in model systems under conditions related to the industrial process of pasta thermal VHT treatment

Non‐enzymatic browning (NEB) due to the Maillard reaction (MR) was studied in a closed starch/glucose/lysine model system (20 g kg⁻¹ glucose, 10 g kg⁻¹ lysine) in order to analyse conditions favouring reactivity during an industrial process of pasta VHT (very high temperature) thermal treatment. The closed model pastes gave data on the NEB progress during the pasta drying cycle as a function of temperature, time and water activity (a_w). Indicators such as headspace CO ₂ , optical density and colour showed an increase of MR as the initial a_w increased from 0.50 to 0.91. During the initial stages of drying, a combination of high temperatures and high a_w led to the most likely conditions for NEB. © 1999 Society of Chemical Industry     

Identification and quantification of α-dicarbonyl compounds produced in different sugar-amino acid Maillard reaction model systems

A mixture of α-dicarbonyl compounds generated from Maillard reaction (MR) model systems, comprising of fructose with glycine (Fru-Gly) and lysine (Fru-Lys); glucose with glycine (Glu-Gly) and lysine (Glu-Lys); ribose with glycine (Rib-Gly) and lysine (Rib-Lys), were identified and quantified. α-Dicarbonyl compounds generated in the hexose models were predominantly glucosone and 3-deoxyglucosone (3-DG), with 3-deoxypentosone (3-DP) and pentosone being the major α-dicarbonyls produced in the pentose models. Ethyl acetate extraction of model MRPs resulted in poor recovery of 2,3-diaminonaphthalene benzoquinoxalines of glucosone, 3-DG, pentosone, 3-DP and methylglyoxal (MGO), respectively. The temporal profiles of pentosone, 3-DP, glyoxal (GO) and MGO were similar in the pentose models, with maximum concentration occurring within 5 min. These four α-dicarbonyl compounds were higher (P < 0.05) in Rib-Gly than in Rib-Lys MR systems. The quantity of α-dicarbonyl compounds was affected by the interaction among the type of sugar and amino acid and the reaction time. The type of sugar is the most important factor that affected both the quantity and quality of α-dicarbonyl compounds produced in MR mixtures.     

Impact of parboiling conditions on Maillard precursors and indicators in long-grain rice cultivars

The effect of steaming conditions (mild, intermediate and severe) during parboiling of five different long-grain rice cultivars (brown rice cultivars Puntal, Cocodrie, XL8 and Jacinto, and a red rice) on rice colour, and Maillard precursors and indicators was investigated. Rice colour increased with severity of parboiling conditions. Redness increased more than yellowness when parboiling brown rice. Parboiling turned red rice black. It changed the levels of glucose, fructose, sucrose, and maltose. Losses of the non-reducing sugar, sucrose were caused by both leaching into the soaking water and enzymic conversion, rather than by thermal degradation during steaming. Concentrations of the reducing sugars, glucose and fructose, in intermediately parboiled rice were higher than those of mildly parboiled rice. After severe parboiling, glucose levels were lower than those of intermediately parboiled rice, while fructose levels were higher. These changes were ascribed to the sum of losses in the Maillard reaction (MR), formations as a result of starch degradation and isomerisation of glucose into fructose. It was clear that the ε-amino group of protein-bound lysine was more affected by parboiling conditions and loss in MRs, than that of free lysine. Low values of the MR indicators furosine and free 5-hydroxymethyl-2-furaldehyde (HMF) in processed brown and red rices were related to mild parboiling, whereas high furosine and low free HMF levels were indicative of rices being subjected to intermediate processing conditions. High furosine and high free HMF contents corresponded to severe hydrothermal treatments. The strong correlation (r = 0.89) between the free HMF levels and the increase in redness of parboiled brown rices suggested that Maillard browning was reflected more in the red than in the yellow colour.     

Comparison of glucose, glucose 6-phosphate, ribose, and mannose as flavour precursors in pork; the effect of monosaccharide addition on flavour generation

The effect of glucose, glucose 6-phosphate, mannose and ribose on the generation of aroma volatiles in pork was investigated. The monosaccharides were added individually to minced pork prior to heat treatment (160°C for 10min) in the following concentrations: glucose (27.5μmol/g), ribose (1.2μmol/g), mannose (8.3μmol/g) and glucose 6-phosphate (0.5μmol/g). The natural concentrations of the monosaccharides in the pork used were found to be 4.0μmol/g for glucose, 0.1μmol/g for ribose, 0.3μmol/g for mannose and 2.6μmol/g for glucose 6-phosphate. The major aroma compounds identified in the headspace of the heated samples were pyrazines, aldehydes (Strecker and lipid-derived), ketones, and sulphides. Glucose generated the highest amounts of volatiles followed by glucose 6-phosphate. However, when related to the added concentration of glucose 6-phosphate, this phosphorylated monosaccharide showed the highest aroma generating potential. The addition of ribose did not increase the concentration of volatiles compared with pork without the added monosaccharide. The fates of ribose 5-phosphate and ribose in pork were studied over time. The concentrations of ribose and ribose 5-phosphate clearly decreased during 2h equilibration, which may be due to enzymatic activities. These precursors may, therefore, be less important pork flavour precursors than glucose and glucose 6-phosphate.     

Short communication: Suitability of fluorescence spectroscopy for characterization of commercial milk of different composition and origin

Thirteen milk brands comprising 76 pasteurized and UHT milk samples of various compositions (whole, reduced fat, skimmed, low lactose, and high protein) were obtained from local supermarkets, and milk samples manufactured in various countries were discriminated using front-face fluorescence spectroscopy (FFFS) coupled with chemometric tools. The emission spectra of Maillard reaction products and riboflavin (MRP/RF; 400 to 600 nm) and tryptophan (300 to 400 nm) were recorded using FFFS, and the excitation wavelengths were set at 360 nm for MRP/RF and 290 nm for tryptophan. Principal component analysis (PCA) was applied to analyze the normalized spectra. The PCA of spectral information from MRP/RF discriminated the milk samples originating in different countries, and PCA of spectral information from tryptophan discriminated the samples according to composition. The fluorescence spectral data were compared with liquid chromatography-mass spectrometry results for the glycation extent of the milk samples, and a positive association (R² = 0.84) was found between the degree of glycation of α-lactalbumin and the MRP/RF spectral data. This study demonstrates the ability and sensitivity of FFFS to rapidly discriminate and classify commercial milk with various compositions and processing conditions.     

Formation and antioxidant activity of volatile compounds produced by heating glucose with tyrosine/histidine in water-ethanol and water-glycerol media

Volatile compounds prepared by heating glucose-tyrosine and glucose-histidine models in water-ethanol and water-glycerol media were studied under different water contents (0%, 25%, 50%, 75%, 100%, v/v). Aliphatic compounds, cyclopentenones, pyrazines, furans, furanones and pyrones were identified by GC–MS and analysed by factor analysis which showed that the presence of ethanol or glycerol in water could result in the increase of most volatile compounds in the Maillard reaction with the higher amount of volatile compounds formed in water-ethanol media, especially in the 50% ethanol medium. The measurement of antioxidant activity revealed that volatile MRPs prepared in water-ethanol media showed greater DPPH radical scavenging activity than those in water-glycerol media with the maximal DPPH radical scavenging activity observed in 100% ethanol medium for the glucose-tyrosine model and in 75% ethanol medium for the glucose-histidine model. Hence, water-ethanol medium could be used to promote the formation of volatile compounds, especially those with antioxidant activity.     

Analysis of characteristic flavour compounds in Chinese rice wines and representative fungi in wheat Qu samples from different regions

The volatile flavour compounds of different Chinese traditional rice wines and the corresponding representative fungi in the wheat Qu (comparable to the koji used in sake brewing) samples were investigated. Results showed that alcohols, acids and esters were abundantly present in the three Chinese rice wines, but the types and concentrations of the volatile flavour compounds by fermentation from different wheat Qu samples were quite distinctive. Cladosporium cladosporioides, Penicillium chrysogenum, Aspergillus oryzae and Saccharomyces cerevisiae were the major components of the fungal flora in the three kinds of wheat Qu samples. Less prevalent genera and species represented in the fungal communities of the three kinds of wheat Qu samples, however, varied greatly, and the richer the flavour substances in the rice wines were, the more abundant the microbe species in the corresponding wheat Qu samples. The results indicate that the types and concentrations of volatile compounds were significantly influenced by the species of microorganisms (moulds and yeasts) in the wheat Qu, which brings a unique flavour to Chinese rice wine. Copyright © 2012 The Institute of Brewing & Distilling     

Environmental conditions affect semolina quality in durum wheat (Triticum turgidum ssp. durum L.) cultivars with different gluten strength and gluten protein composition

BACKGROUND: Sowing time may impact semolina and pasta cooking quality by changing the environmental conditions during grain filling. The effect of an optimum and a delayed sowing time on semolina quality was studied by comparing six cultivars under irrigation, in order to isolate temperature from drought effects. RESULTS: Protein content was higher in the old cultivars and in the late sowings, according to the number of days with temperature between 30 and 40 °C during ripening. Gluten index increased as temperature rose to a threshold of about 30 °C, then decreased under higher temperatures. Mixograph parameters were less sensitive to high temperatures. Gliadin:glutenin correlated with gluten strength. Spaghetti firmness and protein content were positively correlated independently of sowing date. Cultivars Trinakria and Cappelli had the highest spaghetti firmness (900 and 828 g). CONCLUSIONS: Late sowings may represent a way of increasing pasta cooking quality whenever they place grain filling under thermal conditions able to increase protein percentage, although the accompanying decrease in yield may represent a drawback in environments prone to drought stress during ripening. The lower protein percentages of modern durum wheat cultivars under conventional sowing times results in a lower pasta cooking quality despite higher gluten strength. Published 2011 by John Wiley & Sons, Ltd.     

Formation and source analysis of potentially hazardous compounds in fried pepper sauce under different high-temperature stir-fry conditions

In order to investigate the formation and main sources of potentially hazardous compounds in fried pepper sauce (FPS) during the high-temperature frying process, this study analysed the dynamic changes to the lipid oxidation indices (peroxide value, carbonyl value, polar components and malondialdehyde), components of raw materials and excipients (total sugar, reducing sugars and amino acids) and contents of potentially hazardous compounds (trans-fatty acids, benzo[a]pyrene and acrylamide) under different cooking conditions. Path analysis was applied to explore the relationships among the study variables. The results show that low-temperature frying (<190 °C) is beneficial to improve the safety of FPS products. The formation of trans-fatty acids is mainly related to the elevated carbonyl content caused by the high-temperature oxidation of lipids. The total sugar, reducing sugars and amino acids in pepper powder and the other ingredients were mainly responsible for the increase in the content of benzo[a]pyrene and acrylamide, which showed a weak correlation with lipid oxidation. Acrylamide is the main hazardous compound in FPS under high-temperature frying. Therefore, regulating the high-temperature process and the composition of the raw materials and excipients are beneficial to the high-quality production of FPS.     

Comparison of aroma properties of infant formulas: Differences in key aroma compounds and their possible origins in processing

Aroma is an important attribute of infant formula (IF). In this study, 218 volatiles and 62 odor-active compounds were detected from IF by dynamic headspace sampling combined with comprehensive 2-dimensional gas chromatography-olfactometry-mass spectrometry. Aldehydes and ketones were determined as the most abundant odor-active compounds. Among them, the contents of pentanal and hexanal were the most abundant, while 1-octen-3-one had the highest flavor dilution factor and odor activity value in most of the IF. Sensory evaluation and electronic nose analysis showed that the skimming process, the fatty acid composition, and powdered or liquid milk base used for the production of IF may be important factors resulting in their differences in aroma profiles and compounds. These differences were assumed to be mainly ascribed to the Maillard reaction and lipid oxidation, which were largely influenced by the temperature and water activity.     

Role of choline and glycine betaine in the formation of N,N-dimethylpiperidinium (mepiquat) under Maillard reaction conditions

This study is the first to examine the role of choline and glycine betaine, naturally present in some foods, in particular in cereal grains, to generate N,N-dimethylpiperidinium (mepiquat) under Maillard conditions via transmethylation reactions involving the nucleophile piperidine. The formation of mepiquat and its intermediates piperidine – formed by cyclisation of free lysine in the presence of reducing sugars – and N-methylpiperidine were monitored over time (240°C, up to 180 min) using high-resolution mass spectrometry in a model system comprised of a ternary mixture of lysine/fructose/alkylating agent (choline or betaine). The reaction yield was compared with data recently determined for trigonelline, a known methylation agent present naturally in coffee beans. The role of choline and glycine betaine in nucleophilic displacement reactions was further supported by experiments carried out with stable isotope-labelled precursors (¹³C- and deuterium-labelled). The results unequivocally demonstrated that the piperidine ring of mepiquat originates from the carbon chain of lysine, and that either choline or glycine betaine furnishes the N-methyl groups. The kinetics of formation of the corresponding demethylated products of both choline and glycine betaine, N,N-demethyl-2-aminoethanol and N,N-dimethylglycine, respectively, were also determined using high-resolution mass spectrometry.     

Volatile fraction of commercial thyme honeys produced in Mediterranean regions and key volatile compounds for geographical discrimination: A chemometric approach

The aim of the present study was to investigate the volatile fraction and discriminate 34 commercial thyme honeys from Morocco, Egypt, Spain, and Greece according to geographical origin, using key volatile compounds in combination with chemometrics. Sixty-two volatile compounds belonging to different classes were identified and semi-quantified using headspace solid phase micro-extraction coupled to gas chromatography/mass spectrometry (HS-SPME-GC/MS). Applying chemometric analyses to 17 volatiles (p < 0.05), honeys were successfully discriminated according to geographical origin. Correct classification rate was 88.2% using the cross-validation method. Volatile compounds proved to be a powerful tool for discriminating commercial thyme honeys from different countries.     

Deoxynivalenol and other Fusarium mycotoxins in bread,cake, and biscuits produced from UK-grown wheat under commercial and pilot scale conditions

Bread, cakes and biscuits were manufactured from flour containing deoxynivalenol (DON) and low concentrations of zearalenone (ZON) and nivalenol (NIV). The results show that these mycotoxins remain mostly unaffected during manufacture. Although the results indicate that the mycotoxins are largely stable and survive processing, when concentrations were determined on an ‘as is’ basis as stipulated in legislation, levels in finished products were usually lower than in the starting flour due to the dilution effect of other ingredients such as fat, sugar and water. Thus mean concentrations of DON in bread were reduced by about 35% and 39% in white and wholemeal bread respectively which are in close agreement with the reduction required by the regulations although the changes that occur during milling white and wholemeal flour from whole wheat also need to be taken into account. The reduction of DON during cake manufacture is greater than for bread because flour makes up only about 25% of the starting ingredients. However, in biscuit production, particularly for crackers for which flour constitutes about 90% of the recipe ingredients, the reduction indicated by the regulations is not achieved. It is concluded that for some commercial processes, the whole-wheat or flour ingredients used will need to contain DON levels lower than those set by legislation to ensure that the final products will still meet statutory limits. Limited results with consignments containing low concentrations of ZON and NIV suggest that their stability and survival are similar to those for DON.     

Determination of aflatoxins,deoxynivalenol, ochratoxin A and zearalenone in organic wheat flour under different storage conditions

Samples of flour derived from an organic wheat seed cultivated in the region Abruzzo (Central Italy) were examined for the detection of aflatoxins, deoxynivalenol, ochratoxin A and zearalenone after storage in the presence of oxygen or under vacuum, for one year. They were analysed by high-performance liquid chromatography with fluorescence detection for aflatoxins, ochratoxin A and zearalenone and with diode array detector for deoxynivalenol. An immunoaffinity column clean-up was applied for all the compounds, except for aflatoxin determination, which required a solid-phase extraction. Recoveries (range: 76–107%) and within-laboratory reproducibility (RSD% < 10.3) met the performance criteria of Commission Regulation (EU) No. 519/2014 amending Commission Regulation (EC) No. 401/2006 for the detection of mycotoxins in foodstuffs. Analytes were below the detection limit of the method, and this result was probably due to the quality of organic seed and good agricultural practices performed for the prevention of mycotoxin formation.     

Analysis of total polyphenols,bitterness and haze in pale and dark lager beers produced under different mashing and boiling conditions

Malting and brewing processes should be performed under process conditions in a way that minimizes beer bitterness, maximizes polyphenol content and reduces the amount of raw materials ending up in solution in the form of hazes, particles and precipitates. This work examined the influence of different mashing temperature conditions and boiling procedures on the total polyphenol content, bitterness and haze of pale and dark lager beers produced on an industrial scale. Two hop types (hop pellets and/or hop extract) and different hop varieties (Hallertau Magnum, Styrian Goldings, Saaz, Aurora and Sladek) were utilized with varying times of hop addition into the wort. Measurements of total polyphenols, colour, bitterness, alcohol content, CO₂ and pH were carried out on the beer samples. Results showed that pale lager beers had a lower total polyphenol concentration (110–179 mg/L) than dark beers (230–260 mg/L). Using hop extracts instead of hop pellets led to a lower total polyphenol concentration and to less beer foam creation. The change in the proteolytic temperature during mashing only had an influence on the total polyphenol content in the pale lager beer hopped with the pellets. Conducting proteolysis over a 20 min period led to a haze increase in all of the beers produced. In the dark beer, the haze was substantial after just 10 min at 52°C. Copyright © 2015 The Institute of Brewing & Distilling