Neoformed Compounds Research Articles

Integrated effect of yeast inoculation and roasting process conditions on the neo formed contaminants and bioactive compounds of Colombian roasted coffee (Coffea arábica)

The rational design of methodologies to control the neoformed compounds occurrence (NFCs), such as acrylamide and hydroxymethylfurfural (HMF) in roasted coffee, must consider the preservation of the bioactive compounds contained in this beverage. The aim of this work was to evaluate the integrated effect of yeast inoculation during the fermentation stage and the modification of roasting parameters on the final concentrations of NFCs and bioactive compounds of roasted coffee. A completely randomized factorial design was used to evaluate the effect of yeast inoculation (with and without inoculation), roasting temperature (150, 180 and 210 °C) and roast degree (medium, dark) on the (i) physicochemical characteristics (volume change, mass loss, water activity, non-enzymatic browning index, antioxidant capacity, total polyphenols, chlorogenic acid and caffeine) as well as HMF and acrylamide levels of roasted coffee. Response variables were analyzed separately by ANOVA and clustering of treatments was explored by PCA. Yeast inoculation did not significantly (p > 0.05) affect volume change, mass loss, antioxidant capacity, total polyphenols content, and caffeine contents. The interaction of evaluated factors significantly decreased (p < 0.05) the acrylamide and HMF contents of roasted coffee (43 % and 56.0 %, respectively). Based on PCA grouping the best treatments were medium roast at 210 °C (inoculated and uninoculated) and at 180 °C (inoculated). Under these conditions it is possible to produce a roasted coffee mitigated in neo formed contaminants that present the physicochemical properties of original product.

The application of ion mobility time of flight mass spectrometry to elucidate neo-formed compounds derived from polyurethane adhesives used in champagne cork stoppers

Polyurethane adhesives are used to bond agglomerated cork and natural disk cork to produce cork stoppers that are used in champagne bottles. These adhesives are manufactured by reacting polyols with an excess of diisocyanates. Isocyanates are highly reactive compounds that have a propensity to form non-intentionally added substances (NIAS) in the end product. In this work, ion mobility-time of flight-mass spectrometry was used to elucidate such NIAS, through the comparison of accurate mass spectra with the fragmentation patterns of proposed candidates. Twelve neo-formed compounds, including amines, amides and urethanes, resulting from the reaction of isocyanates with acetic acid and ethanol used as food simulants, were identified. Additionally, markers from champagne vs. champagne after its exposure to the adhesive were investigated using the supervised multivariate analysis method of Orthogonal Projection to Latent Structures – Discriminant Analysis. Four neo-formed compounds, resulting from the reaction of diisocyanates with malic acid or tartaric acid contained in the champagne, were identified for the first time in this work. All of the compounds identified were subsequently quantified using ultra-high pressure liquid chromatography coupled to a triple quadrupole mass spectrometer. Limits of detection were below 5 μg/kg in the food simulants and below 30 μg/kg in champagne samples. Migration levels ranged from 70 to 721 μg/kg, with most of them exceeding the specific migration limit established for Cramer class III compound (90 μg/kg).

Inhibition Mechanism of L-Cysteine on Maillard Reaction by Trapping 5-Hydroxymethylfurfural.

The Maillard reaction (MR) can affect the color, flavor, organoleptic properties, and nutritional value of food. Sometimes, MR is undesirable due to lowering the nutrient utilization, producing harmful neo-formed compounds, etc. In this case, it is necessary to control MR. Some chemical substances, such as phenolic acid, vitamins, aminoguanidine, and thiols extracted from garlic or onion, can effectively prevent MR. In this study, L-cysteine (L-cys) was found to inhibit MR after screening 10 sulfhydryl compounds by comparing their ability to mitigate browning. The inhibition mechanism was speculated to be related to the removal of 5-hydroxymethylfurfural (HMF), a key mid-product of MR. The reaction product of HMF and L-cys was identified and named as 1-dicysteinethioacetal–5-hydroxymethylfurfural (DCH) according to the mass spectrum and nuclear magnetic resonance spectrum of the main product. Furthermore, DCH was detected in the glutamic–fructose mixture after L-cys was added. In addition, the production of DCH also increased with the addition of L-cys. It also was worth noting that DCH showed no cell toxicity to RAW 264.7 cells. Moreover, the in vitro assays indicated that DCH had anti-inflammatory and antioxidant activities. In conclusion, L-cys inhibits MR by converting HMF into another adduct DCH with higher safety and health benefits. L-cys has the potential to be applied as an inhibitor to prevent MR during food processing and storage.

The antibacterial and antiproliferative ability of kānuka, Kunzea ericoides, leaf extracts obtained by subcritical water extraction

AbstractBACKGROUNDSubcritical water kānuka leaf extracts contain high levels of polyphenols. However, whether these extracts can serve as natural antimicrobial and chemopreventive agents is still a question. This study aimed to evaluate the antibacterial and antiproliferative efficacy of SWE kanuka leaf extracts. Subcritical water extraction (SWE) was used to obtain natural extracts from kānuka leaves potentially rich in biologically active compounds. The antibacterial and antiproliferative capacities were assessed by broth microdilution assay and MTT‐assay, respectively. The assessed properties were compared to extraction from ethanol extraction (EE).ResultsThe screening results for antibacterial properties demonstrated that subcritical water kānuka leaf extracts were active against Escherichia coli (minimum conc. 0.8 mg/mL) and Staphylococcus aureus (minimum conc. 3.8 mg/mL). These extracts also exerted dose‐dependent antiproliferative effects on the viability of cancerous human cervical cell lines (Hep‐2 and RD cells) and mouse cell lines (L cells). The extraction temperature had significantly affected the extract's activities by enhancing neoformed compounds with beneficial effects.CONCLUSIONSSubcritical water extracts of kānuka demonstrated a better efficacy against bacterial growth and malignant cells viability in comparison to extracts obtained using conventional ethanol extraction. This SWE kānuka leaf product could be used in a range of applications where antimicrobial and antiproliferative properties are required. Further studies are needed to examine the mechanism and markers of these properties. © 2020 Society of Chemical Industry

Development and validation of a modified QuEChERS protocol coupled to UHPLC-APCI-MS/MS for the simple and rapid quantification of 16 heterocyclic aromatic amines in cooked beef

Heterocyclic aromatic amines (HAAs) are neo-formed compounds generated during the cooking of meats and are known or suspected to be mutagenic and carcinogenic. In this study, a novel, simple, and fast methodology combining salting-out liquid–liquid microextraction, solid-phase extraction (SPE), and UHPLC–APCI–MS/MS was developed for the analysis of 16 HAAs. The QuEChERS extraction (quick, easy, cheap, efficient, rugged, and safe) was revisited and modified using mixed-mode SPE purification to adapt the method to the particular physicochemical properties of HAAs and the fatty nature of the beef matrix. The UHPLC–MS/MS analysis was performed on a C8 column in less than 4 min using positive APCI ionisation and an internal standard. The method was validated according to the European Medicines Agency and Eurachem guidelines and was successfully applied to beef samples of various cooking degrees, showing HAA levels similar to those shown by previous studies.

Peroxide Index, Trans Fatty Acids, Acrylamide and Polycyclic Aromatic Hydrocarbons (Pah) Contents in Frying Oils and Fried Tuna Fish Involved in “Garba” Production in C&amp;#244;te d’Ivoire

This current study aims at determining the profile and contents of degradation compounds produced during the interaction between the frying oils and tuna fish involved in the cooking of “Garba”, a street food largely consumed in Côte d’Ivoire. For this purpose, the peroxide index and the neoformed compounds, especially trans fatty acids, acrylamid, polycyclic aromatic hydrocarbons were determined. This trial was carried out on 90 samples of frying oils and fried tuna fish collected from restaurant owners of “Garba” food in three locations in Abidjan. The samples were divided into three groups (G1, G2, and G3) according to the similarity of the practices adopted by the restorers. The results show that the peroxide values (14.95; 15.01 and 11.97 meqO2/kg) of the oils respectively for G2, G3, and G1 are higher than the values fixed by the Codex Alimentarius. The trans fatty acid contents of the frying oils were 56.80%; 61.01% and 55.18% respectively for G3, G2 and G1. The average acrylamide content of fried Tuna (69.43 μg/kg) is higher than the value recorded in the cooking oil (19.99 μg/kg). The average contents of the eleven HAPs determined in the oils are higher than those of the Tuna. The Benzo (a) pyrene contents of both matrices are lower than the EU standard 1881/2011 except for the G2 oil (2.66 μg/kg). Increased consumption of “Garba” may pose health risks to consumers as practices of frying Tuna generate compounds that are harmful to human health.

Nanoscale investigation by TEM and STEM-EELS of the laser induced yellowing

Nd-YAG QS laser cleaning of soiled stone at 1064 nm can sometimes result in a more yellow appearance compared to other cleaning techniques. Especially in France, this yellowing effect is still considered as a major aesthetic issue by the architects and conservators. One explanation states that the yellowing is linked to the formation of iron-rich nanophase(s) through the laser beam interaction with black crusts that would re-deposit on the cleaned substrate after irradiation. To characterize these nanophases, a model crust containing hematite was elaborated and laser irradiated using a Nd-YAG QS laser. The color of the sample shifted instantaneously from red to a bright yellow and numerous particles were ablated in a visible smoke. Transmission electron microscopy (TEM) was used to examine the morphology and the crystallinity of the neo-formed compounds, both on the surface of the samples and in the ablated materials. In addition, an investigation of the chemical and structural properties of the nanophases was conducted by X-ray dispersive energy (EDX) and electron energy loss (EELS) spectroscopies. It was found that both the surface of the sample and the ablated materials are covered by crystallized nano-spheres and nano-residues, all containing iron and oxygen, sometimes along with calcium and sulfur. In particular an interfacial area containing the four elements was evidenced between some nanostructures and the substrate. Magnetite Fe3O4 was also identified at the nanoscale. This study demonstrates that the laser yellowing of a model crust is linked to the presence of iron-rich nanophases including CaxFeySzOδ nanostructures and magnetite Fe3O4 at the surface after irradiation.

Maillard reaction products from highly heated food prevent mast cell number increase and inflammation in a mouse model of colitis

Links between food and inflammatory bowel diseases (IBDs) are often suggested, but the role of food processing has not been extensively studied. Heat treatment is known to cause the loss of nutrients and the appearance of neoformed compounds such as Maillard reaction products. Their involvement in gut inflammation is equivocal, as some may have proinflammatory effects, whereas other seem to be protective. As IBDs are associated with the recruitment of immune cells, including mast cells, we raised the hypothesis that dietary Maillard reaction products generated through heat treatment of food may limit the colitic response and its associated recruitment of mast cells. An experimental model of colitis was used in mice submitted to mildly and highly heated rodent food. Adult male mice were divided in 3 groups and received nonheated, mildly heated, or highly heated chow during 21 days. In the last week of the study, each group was split into 2 subgroups, submitted or not (controls) to dextran sulfate sodium (DSS) colitis. Weight variations, macroscopic lesions, colonic myeloperoxidase activity, and mucosal mast cell number were evaluated at the end of the experiment. Only highly heated chow significantly prevented DSS-induced weight loss, myeloperoxidase activity, and mast cell number increase in the colonic mucosa of DSS-colitic mice. We suggest that Maillard reaction products from highly heated food may limit the occurrence of inflammatory phases in IBD patients.

Neoformed Compounds from the Maillard Reaction in Infant Formulas: A New Risk Factor for Allergy?

Food allergies, which are T helper cell Type 2 aberrant responses of the immune system to food proteins, are increasing. Environmental factors, including food contaminants, are often mentioned to explain this increase. Heat treatment of food induces the Maillard reaction, a non-enzymatic reaction between reducing sugars and free amino groups of proteins or free amino acids. This leads to the genesis of neoformed compounds, including advanced Maillard reaction products (also called dietary advanced glycation end-products [AGEs]). Infant formulas are very sensitive to the Maillard reaction because of their high content of lactose and proteins and their long shelf life. The dietary AGEs content is particularly high in hydrolysed infant milk. Among dietary AGEs, Nε-carboxymethyllysine is the main form in milk. An increasing number of studies show potentially deleterious effects of dietary AGEs, including inflammation genesis. These effects seem to be in a great part dependent on the receptor of AGEs (RAGE). RAGE is present on immune cells and studies have shown that RAGE is involved in T helper cell priming, proliferation, and differentiation. Moreover, there is increasing evidence that the Maillard reaction enhances the allergenicity of proteins. All these data indicate a potential role of dietary AGEs in allergies. Nevertheless, the impact of dietary AGEs on the immune system favouring the T helper cell Type 2 profile and consequently predisposition to develop allergy is poorly documented and needs further investigation.

Protection against neo-formed contaminants (NFCs)-induced toxicity by phytochemicals

Neo-formed compounds (NFCs) are commonly found in all kinds of foods due to the complex reaction between components during processing. Acrylamide, benzo(a)pyrene and heterocyclic aromatic amines are the main types of NFCs in foods enriched with carbohydrate, fats and proteins, respectively. They have exhibited diverse toxicity, such as neurotoxicity, genotoxicity, potentially carcinogenic and reproductive toxicity. In recent years, various phytochemicals have been found to be effective in alleviation of their related toxicities both in vitro and in vivo. This review provides evidences on the protection roles of phytochemicals against the diverse toxicity induced by three NFCs. Moreover, the prevention mechanisms of phytochemicals are summarized. Three potential aspects involving excellent antioxidant activity, DNA protection and enzyme induction contribute to the successful protection mechanism. Meanwhile, the limitations from existing knowledge have been illustrated and the possible perspectives for the further study have also been considered. The information from this review would be useful to provide an easier and better way to improve human health when considering the possibility of using foods enriched with phytochemicals for prevention of the toxicity of exogenous pollutants.

Effect of metronidazole supplemented with hydroquinone on the adhesion of Lactobacillus acidophilus in ovine vaginal cells

This work demonstrates that the addition of metronidazole together with a ubiquitous quinone compound reduces adherence of Lactobacillus acidophilus to ovine vaginal cells.Spectrophotometric and voltammetric studies have shown that neoformed compounds were observed in these systems; there were also changes in their electroactive composition, and the oxidant status had a significantly higher value compared to the control (p<0.05). Based on reduction potential (E; mV), the distribution of electroactive compound concentrations suggests that the compounds with low reduction potential induce this behavior, which would indicate that the addition of metronidazole with a ubiquitous quinone compound to the vaginal system might increase the reductive capacity of these systems.This work shows that the study of behavior and fluctuations of the redox compounds that compose the vaginal environment, in terms of concentration and species of redox molecules, must be hierarchized in order to better understand the early stages of colonization by microorganisms.

Determination of caramel colorants’ by-products in liquid foods by ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)

2-Methylimidazole, 4-methylimidazole (2-MI and 4-MI), 2-acetyl-4-(1,2,3,4-tetrahydroxybutyl) imidazole (THI) and 5-hydroxymethylfurfural (5-HMF) are neo-formed compounds generated during the manufacture of caramel colours and are transferred to the processed food. These contaminants are known to have a toxicological profile that may pose health risks. Hence, to characterise THI, 2- and 4-MI and 5-HMF levels in liquid foods, an ultra-high-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and sample preparation was divided into two analytical strategies depending on the concentration range expected in the type of foods targeted. For the determination of the imidazole substitutes (THI, 2- and 4-MI), a sample enrichment and clean-up step by strong cation solid-phase extraction was developed. This method is capable of quantifying over a range of 5 ng ml–1 (LOQ) to 500 ng ml–1 with recoveries of 75.4–112.4% and RSDs of 1.5–15%. For determination of 5-HMF, a standard addition method was applied covering the linear range of 0.25–30 µg ml–1 with RSDs from 2.8% (for intraday precision) to 9.2% (for intermediate precision). The validated analytical methods were applied to 28 liquid food samples purchased from local markets. THI was found only in the beer samples at levels up to 141.2 ng ml–1. For 2-MI, non-quantifiable traces were observed for all samples, while 4-MI was observed in all samples with large concentration variations (from < LOQ to 563.9 ng ml–1). 5-HMF was found at expected concentrations, except for a sherry vinegar sample (113 µg ml–1), which required a high level of dilution before following the standard addition protocol.

Influence of microwave heating time on the structure and properties of chitosan films

ABSTRACTThe aim of this study was to investigate chitosan film behavior during microwave heating for 10 different heating times from 0 to 40 min. Chitosan films were produced by casting. Their structure and properties were investigated with several techniques, including Fourier transform infrared spectroscopy and differential scanning calorimetry, but also by the measurement of the film color and the mechanical properties or by the study of the rheological properties of the rehydrated films. An original technique of gas chromatography (electronic nose) was used to analyze the film odor and highlight the presence of volatile compounds related to the Maillard reaction occurring during film heating. The results show that structural modifications occurred in two steps; this affected the polymer structure, such as the crystallization and chain scission. The appearance of the neoformed compounds was also observed and must be controlled to guarantee the safety of this food‐contact packaging material. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40779.

Potential of front face fluorescence as a monitoring tool of neoformed compounds in industrially processed carrot baby food

The aim of this study was to evaluate the potential of using front face fluorescence (FFF) to monitor the impact of industrial process on carrot baby food, and to calibrate their content in neoformed compounds (NFC). Chromatographically measured NFC included furosine, carboxymethyllysine, and furan. The effect of using different raw material, fresh carrots, frozen cubes or pasteurized puree on NFC content in the resultant sterilized puree was also tested. Bidimensional FFF spectra acquired on the samples were decomposed using multiway PARAFAC model and used to predict the chromatographically measured NFC. FFF PARAFAC sample intensities systematically evolved with successive industrial process steps. The levels of NFC increased the most during heat treatment operations. Frozen cubes resulted in the purees with the lowest content in NFC, compared to fresh or pasteurized carrot cubes. Satisfactory calibration models (R2 > 0.94) of the chromatographically measured NFC were obtained using FFF PARAFAC sample intensities as predictors. The multivariate regression models root mean square of cross validation for furosine, carboxymethyllysine, and furan were 3.98 mg/kg, 1.38 mg/kg and 5.23 µg/kg, respectively. From these first results we conclude that FFF is a promising tool to monitor fast and easily vegetable processing in a quality control approach.

Antioxidants Release from Solvent-Cast PLA Film: Investigation of PLA Antioxidant-Active Packaging

The release study of natural antioxidants, i.e., ascorbyl palmitate and α-tocopherol, and synthetic phenolic antioxidants including butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), propyl gallate, and tert-butylhydroquinone (TBHQ) from polylactic acid (PLA) film into food simulants were accomplished. PLA antioxidant films were placed in contact with 95, 50, and 10 % ethanol at 40 and 20 °C. Released antioxidants were regularly measured by high-performance liquid chromatography system for 60 days. Ascorbyl palmitate was completely degraded during film preparation and is not a suitable antioxidant for PLA antioxidant-active packaging. The diffusion coefficient (D) and partition coefficient (K) of antioxidants were calculated based on obtained data. Diffusion of the antioxidants from PLA to the simulants showed a Fick’s behavior with the diffusion coefficient (D) value between 10−9 and 10−11 cm2 s−1 with 0–100 % of release. Faster and higher release of antioxidants occurred at 40 °C according to Arrhenius law. At 40 °C, TBHQ in 95 % ethanol decomposed to 2-tert-butyl-1,4-benzoquinone and other quinone derivatives, and α-tocopherol in 50 % ethanol decomposed to some unknown neoformed compounds. Antioxidants molecular weight, Log P, simulant polarity, and temperature were the most influencing factors on antioxidants release rate from PLA films in contact with food simulants. The D and K coefficients of studied antioxidants from PLA in three food simulants and two temperatures can be used to create PLA antioxidant-active packaging to continually control the oxidation reactions in diverse foodstuffs to ensure higher food qualities. The PLA antioxidant-active packaging approach also permits to reduce the amounts of directly added antioxidants in foods to provide safer foods.

Inhibition of enzymatic browning in actual food systems by the Maillard reaction products

The Maillard reaction occurring between amino acids and sugars produces neo-formed compounds having certain levels of antioxidant activity depending on the reaction conditions and the type of reactants. The objective of this study was to investigate enzymatic browning inhibition capacity of Maillard reaction products (MRPs) formed from different amino acids including arginine (Arg), histidine (His), lysine (Lys) and proline (Pro). The inhibitory effects of the MRPs on polyphenol oxidase (PPO) were determined. The total antioxidant capacity (TAC) of MRPs derived from different amino acids were in the order Arg > His > Lys > Pro. The TAC and PPO inhibition of MRPs were evaluated as a function of temperature (80-120 °C), time (1-6 h) and pH (2-12). Arg-Glc and His-Glc MRPs exhibited strong TAC and PPO inhibition. Increasing temperature (up to 100 °C) and time also increased TAC and PPO inhibition. Kinetics analysis indicated a mixed type inhibition of PPO by MRPs. The results indicate that the MRPs derived from Arg and His under certain reaction conditions significantly prevent enzymatic browning in actual food systems. The intermediate compounds capable of preventing enzymatic browning are reductones and dehydroreductones, as confirmed by liquid chromatographic-mass spectrometric analyses.

Facts about the formation of new antioxidants in natural samples after subcritical water extraction

Subcritical water extraction (SWE) is a very promising technique for obtaining bioactives (mainly antioxidants) from natural sources; even if sometimes the high operation temperatures have been suggested as responsible for thermal degradation of bioactives, the fact is that this type of extraction processes may generate new bioactive (antioxidant) compounds. The present study involved the analysis of antioxidants either naturally found in raw samples and/or those formed during extraction via Maillard reaction and other chemical events. Samples of different nature like microalgae ( Chlorella vulgaris), algae ( Sargassum vulgare, Porphyra spp., Cystoseira abies-marina, Sargassum muticum, Undaria pinnatifida, and Halopitys incurvus) and plants (rosemary, thyme and verbena) were studied. Amino acid availability, sugar content, fluorescence and absorbance at different wavelengths were determined to follow chemical changes due to reactions such as Maillard, caramelization and thermoxidation. Folin reaction also provided information related to total phenol content of the samples. ABTS +, peroxyl as well as superoxide radical scavenging assays were used to measure the antioxidant capacity of the extracts. Results obtained from this study suggest that neoformed compounds derived from Maillard, caramelization and thermoxidation reactions affect the overall antioxidant capacity of water subcritical extracts depending on the nature of the sample. The brown algae U. pinnatifida was the sample in which these chemical events contributed to a higher extent to improve the antioxidant capacity (from 0.047 to 1.512 mmol/g and from 45.356 to 1522.692 μmol/g for the TEAC and ORAC FL methods, respectively) when the extraction temperature was raised from 100 to 200 °C. To the best of our knowledge, this is the first work supporting the formation of neoantioxidants in natural complex matrices during subcritical water extraction.

Rapid assessment of neoformed compounds in nuts and sesame seeds by front-face fluorescence

The potential of a rapid spectral method, based on front-face fluorescence, to monitor lipid neoformed compounds (NFC) during processing of nuts and sesame seeds was investigated. Fluorescence fingerprints were obtained from front-face fluorescence acquisition directly on crushed nuts and sesame seed samples obtained at different stages of processing. Fluorescence was very sensitive to physicochemical changes induced by the heat process, namely roasting. Parallel factor (PARAFAC) analysis of the fluorescence landscapes revealed four main fluorescence profiles in the nuts, and five in the sesame seeds. These were associated with peptidic tryptophan, tocopherols and process derived products. Various regression models between fluorescence spectra and NFC appearing during the process, carboxymethyllysine (CML) and trans fatty acids (tFA) showed good correlations ( R > 0.89) and satisfactory prediction errors (RMSECV < 1.67). When applied to indicators of lipid peroxidation, good regression models were also obtained allowing prediction of the pAV ( p-anisidine value) and TBARs (thiobarbituric acid reactive substances): R = 0.73 and 0.96 in nuts and sesame seeds, respectively, with prediction errors lower than 0.78. This study demonstrates the interest of front-face fluorescence as a promising tool for quality control of nuts and seeds roasting.

The fate of furfurals and other volatile markers during the baking process of a model cookie

This work investigates the generation and the evolution of some neoformed compounds formed during the baking of a model biscuit. Thank to their physicochemical properties of volatility and hydrophobicity, furfurylic compounds were followed by a double approach: the analysis of the volatile fraction extracted from food matrix and from the vapours released during the thermal process. 5-Hydroxymethylfurfural (HMF) was the main furfurylic compound formed, it followed an exponential kinetic in both the matrix and the vapours of baking biscuits. However, at the very final stage of baking a drop in HMF was observed in the cookie matrix whereas increasing amounts of HMF were still found in the vapours of baking. Moreover, some degradation products of HMF such as furaldehyde (F) and 2-methylfurfural (MF) were also detected. These observations support the hypothesis of a concomitant volatilization and degradation of HMF during the baking of the model cookie, under our experimental conditions. Monitoring of baking vapours by dynamic SPME coupled to quantitative analysis of chemical and physical markers in the food matrix seems to be a powerful tool to gain knowledge on the behaviour of neoformed compounds generated by thermal processes in solid food systems.

Inhibition of polyphenoloxidase activity by mixtures of heated cysteine derivatives with carbonyl compounds

It had previously been shown that soluble Maillard reaction products (MRP) made from thiol compounds and glucose or fructose contained powerful inhibitors of various fruit and vegetable polyphenoloxidase (PPO) activity. In MRP from cysteine and glucose, the amount of hydroxymethylfurfural (HMF) formed increased with the increase in glucose concentration (0-1 M), particularly under acidic (pH 2) conditions. Using model mixtures containing a preheated cysteine-derived compound and a carbonyl component, especially HMF, furfural and benzaldehyde, we showed that the neoformed compounds produced exhibited a stronger inhibitory potency toward PPO activity of eggplant, apple, and mushroom than former MRP. Optimal reaction conditions for the formation of inhibitory compounds when HMF reacted with preheated cysteine were investigated. It was found that a reactants molar ratio of 1:1 and a reaction time exceeding 1 h were the most efficient reaction conditions to generate inhibitory compounds. The stability of the newly formed products, evaluated during storage, showed that their inhibitory potency was globally kept at 4, 21, and 37 degrees C for 72 h but was unstable when stored at -20 degrees C and lost when exposed to UV radiations for 24 h.