Diacetyl Concentration Research Articles

Characterisation and quantification of changes in odorants from litter headspace of meat chickens fed diets varying in protein levels and additives

The effect of dietary crude protein (CP) and additives on odor flux from meat chicken litter was investigated using 180 day-old Ross 308 male chicks randomly allocated to five dietary treatments with three replicates of 12 birds each. A 5 × 3 factorial arrangement of treatments was employed. Factors were: diet (low CP, high CP, high CP+antibiotic, high CP+probiotic, high CP+saponin) and age (15, 29, 35 days). The antibiotic used was Zn bacitracin, the probiotic was a blend of three Bacillus subtilis strains and the saponin came from a blend of Yucca and Quillaja. Odorants were collected from litter headspace with a flux hood and measured using selective ion flow tube mass spectrometry (SIFT-MS). Litter moisture, water activity (Aw), and litter headspace odorant concentrations were correlated. The results showed that low CP group produced lower flux of dimethyl amine, trimethyl amine, H2 S, NH3, and phenol in litter compared to high CP group (P < 0.05). Similarly, high CP+probiotic group produced lower flux of H2 S (P < 0.05) and high CP+saponin group produced lower flux of trimethylamine and phenol in litter compared to high CP group (P < 0.05). The dietary treatments tended (P = 0.065) to have higher flux of methanethiol in high CP group compared to others. There was a diet × age interaction for litter flux of diacetyl, 3-hydroxy-2-butanone (acetoin), 3-methyl-1-butanol, 3-methylbutanal, ethanethiol, propionic acid, and hexane (P < 0.05). Concentrations of diacetyl, acetoin, propionic acid, and hexane in litter were higher from low CP group compared to all other treatments on d 35 (P < 0.05) but not on d 15 and 29. A high litter moisture increased water activity (P < 0.01) and favored the emissions of methyl mercaptan, hydrogen sulfide, dimethyl sulfide, ammonia, trimethyl amine, phenol, indole, and 3-methylindole over others. Thus, the low CP diet, Bacillus subtilis based probiotic and the blend of Yucca/Quillaja saponin were effective in reducing the emissions of some key odorants from meat chicken litter.

Simultaneous analysis of some volatile compounds in food samples by array gas sensors based on polypyrrole nano-composites

PurposeThe purpose of this paper is to construct an array of sensors using polypyrrole–zinc oxide (PPy–ZnO) and PPy–vanadium (V; chemical formula: V2O5) fibers. To test responses of sensors, a central composite design (CCD) has been used. The results of the CCD technique revealed that the developed sensors are orthogonally sensitive to diacetyl, lactic acid and acetic acid. In total, 20 different mixtures of diacetyl, lactic acid and acetic acid were prepared, and the responses of the array sensors were recorded for each mixture.Design/methodology/approachA response surface regression analysis has been used for correlating the responses of the sensors to diacetyl, lactic acid and acetic acid concentrations during the gas phase in food samples. The developed multivariate model was used for simultaneous determination of diacetyl, lactic acid and acetic acid concentrations. Some food samples with unknown concentrations of diacetyl, lactic acid and acetic acid were provided, and the responses of array sensors to each were recorded.FindingsThe responses of each sensor were considered as target response in a response optimizer, and by an overall composite desirability, the concentration of each analyte was predicted. The present work suggests the applicability of the response surface regression analysis as a modeling technique for correlating the responses of sensor arrays to concentration profiles of diacetyl, lactic acid and acetic acid in food samples.Originality/valueThe PPy–ZnO and PPy–V2O5 nanocomposite fibers were synthesized by chemical polymerization. The provided conducting fibers, PPy–ZnO and PPy–V2O5, were used in an array gas sensor system for the analysis of volatile compounds (diacetyl, lactic acid and acetic acid) added to yogurt and milk samples.

Reduced production of diacetyl by overexpressing BDH2 gene and ILV5 gene in yeast of the lager brewers with one ILV2 allelic gene deleted.

Diacetyl causes an unwanted buttery off-flavor in lager beer. The production of diacetyl is reduced by modifying the metabolic pathway of yeast in the beer fermentation process. In this study, BDH2 and ILV5 genes, coding diacetyl reductase and acetohydroxy acid reductoisomerase, respectively, were expressed using a PGK1 promoter in Saccharomyces cerevisiae, which deleted one ILV2 allelic gene. Diacetyl contents and fermentation performances were examined and compared. Results showed that the diacetyl content in beer was remarkably reduced by 16.52% in QI2-KP (one ILV2 allelic gene deleted), 55.65% in QI2-B2Y (overexpressed BDH2 gene and one ILV2 allelic gene deleted), and 69.13% in QI2-I5Y (overexpressed ILV5 gene and one ILV2 allelic gene deleted) compared with the host strain S2. The fermentation ability of mutant strains was similar to that of S2. Results of the present study can lead to further advances in this technology and its broad application in scientific investigations and industrial beer production.

Diacetyl and 2,3-pentanedione in breathing zone and area air during large-scale commercial coffee roasting, blending and grinding processes.

Recently described scientific literature has identified the airborne presence of 2,3-butanedione (diacetyl) and 2,3-pentanedione at concentrations approaching or potentially exceeding the current American Conference of Industrial Hygienists' (ACGIH) Threshold Limit Values (TLVs) at commercial coffee roasting and production facilities. Newly established National Institutes of Occupational Safety and Health (NIOSH) Recommended Exposure Limits for diacetyl and 2,3-pentanedione are even more conservative. Chronic exposure to these alpha-diketones at elevated airborne concentrations has been associated with lung damage, specifically bronchiolitis obliterans, most notably in industrial food processing facilities. Workers at a large commercial coffee roaster were monitored for both eight-hour and task-based, short-term, 15-min sample durations for airborne concentrations of these alpha-diketones during specific work processes, including the coffee bean roasting, blending and grinding processes, during two separate 8-h work periods. Additionally, the authors performed real-time Fourier transform infrared spectroscopy (FTIR) analysis of the workers' breathing zone as well as the area workplace air for the presence of organic compounds to determine the sources, as well as quantitate and identify various organic compounds proximal to the roasting and grinding processes. Real-time FTIR measurements provided both the identification and quantitation of diacetyl and 2,3-pentanedione, as well as other organic compounds generated during coffee bean roasting and grinding operations. Airborne concentrations of diacetyl in the workers' breathing zone, as eight-hour time-weighted averages were less than the ACGIH TLVs for diacetyl, while concentrations of 2,3-pentanedione were below the limit of detection in all samples. Short-term breathing zone samples revealed airborne concentrations for diacetyl that exceeded the ACGIH short-term exposure limit of 0.02 parts per million (ppm) in two samples collected on a grinder operator. FTIR analysis of air samples collected from both the workers' breathing zone and area air samples revealed low concentrations of various organics with diacetyl and 2,3-pentanedione at concentrations less than the limit of detection for the FTIR methods. Neither the breathing zone nor area air samples measured using the FTIR reflected airborne concentrations of organic compounds that, when detected, approached the ACGIH TLVs or regulatory standards, when available. FTIR analysis of headspace of ground coffee beans revealed ppm concentrations of expected alpha diketones, carbon monoxide and other volatile organic compounds (VOCs). Coffee roasting and grinding, with adequate building ventilation and typical roasted bean handling and grinding, appears to generate very low, if any, concentrations of diacetyl and 2,3-pentanedione in the workers' breathing zones. This study also confirmed via FTIR that roasted coffee beans naturally generate alpha-diketones and other organic compounds as naturally occurring compounds resultant of the roasting and then released during the grinding process.

A Light-Addressable Potentiometric Sensor for Odorant Detection Using Single Bioengineered Olfactory Sensory Neurons as Sensing Element.

A light-addressable potentiometric sensor (LAPS), a silicon-based surface potential detector, is combined with bioengineered olfactory sensory neurons (OSN) for odorant detection. A LAPS chip is used as a transducer to monitor cell membrane potential changes. In addition, a focused movable laser with a diameter comparable to cell sizes is employed to select the desirable single cell for measurement under a microscope. Bioengineered OSNs are coupled to the LAPS surface and employed as sensing elements, which are prepared by the expression of an olfactory receptor of C. elegans, ODR-10, on the plasma membrane of rat primary OSNs via transient transfection. The responses of bioengineered OSNs to diacetyl, isoamyl acetate, and acetic acid are monitored by extracellular recording using the LAPS chip. Features of the recorded extracellular potential firings are analyzed in frequency and time domains. We have shown that bioengineered OSNs can generate specific response signals upon the stimulation of diacetyl, which is the natural ligand of ODR-10. Moreover, different concentrations of diacetyl can elicit different temporal firing patterns in bioengineered OSNs, which permits the concentration detection of specific odorant molecules in solution.

Technological Development of Brewing in Domestic Refrigerator Using Freeze-Dried Raw Materials.

Development of a novel directly marketable beer brewed at low temperature in a domestic refrigerator combined with yeast immobilization technology is presented in this study. Separately, freeze-dried wort and immobilized cells of the cryotolerant yeast strain Saccharomyces cerevisiae AXAZ-1 on tubular cellulose were used in low-temperature fermentation (2, 5 and 7 °C). The positive effect of tubular cellulose during low-temperature brewing was examined, revealing that freeze-dried immobilized yeast cells on tubular cellulose significantly reduced the fermentation rates in contrast to freeze-dried free cells, although they are recommended for home-made beer production. Immobilization also enhanced the yeast resistance at low-temperature fermentation, reducing the minimum brewing temperature value from 5 to 2 °C. In the case of high-quality beer production, the effect of temperature and initial sugar concentration on the fermentation kinetics were assessed. Sensory enrichment of the produced beer was confirmed by the analysis of the final products, revealing a low diacetyl concentration, together with improved polyphenol content, aroma profile and clarity. The proposed process for beer production in a domestic refrigerator can easily be commercialized and applied by dissolving the content of two separate packages in tap water; one package containing dried wort and the other dried immobilized cells on tubular cellulose suspended in tap water.

Inhalation dosimetry modeling provides insights into regional respiratory tract toxicity of inhaled diacetyl.

Vapor dosimetry models provide a means of assessing the role of delivered dose in determining the regional airway response to inspired vapors. A validated hybrid computational fluid dynamics physiologically based pharmacokinetic model for inhaled diacetyl has been developed to describe inhaled diacetyl dosimetry in both the rat and human respiratory tracts. Comparison of the distribution of respiratory tract injury with dosimetry estimates provides strong evidence that regional delivered dose rather than regional airway tissue sensitivity to diacetyl-induced injury is the critical determinant of the regional respiratory tract response to this water soluble reactive vapor. In the rat, inhalation exposure to diacetyl causes much lesser injury in the distal bronchiolar airways compared to nose and large tracheobronchial airways. The degree of injury correlates very strongly to model based estimates of local airway diacetyl concentrations. According to the model, regional dosimetry patterns of diacetyl in the human differ greatly from those in the rat with much greater penetration of diacetyl to the bronchiolar airways in the lightly exercising mouth breathing human compared to the rat, providing evidence that rat inhalation toxicity studies underpredict the risk of bronchiolar injury in the human. For example, repeated exposure of the rat to 200ppm diacetyl results in bronchiolar injury; the estimated bronchiolar tissue concentration in rats exposed to 200ppm diacetyl would occur in lightly exercising mouth breathing humans exposed to 12ppm. Consideration of airway dosimetry patterns of inspired diacetyl is critical to the proper evaluation of rodent toxicity data and its relevance for predicting human risk.

Co-inoculation with Yeast and LAB Under Winery Conditions: Modification of the Aromatic Profile of Merlot Wines

The present work reports the impact of yeast/LAB co-inoculation on the aromatic profile of Merlot wines made in wineries. This study was carried out over two consecutive years on five Merlot wines in Bordeaux and Swiss wineries, using Saccharomyces cerevisiae and Oenococcus oeni starter cultures. Seventy aromatic compounds were quantified and, in addition, the sensory profiles of two wines were determined in order to compare the aromatic notes of the sequential and co-inoculated wines. The influence of the timing of inoculation with lactic acid bacteria (LAB) on the metabolic profile of wines was observed. It confirmed previous work carried out on a micro-scale but, for the first time, the impact of yeast/LAB co-inoculation was significantly demonstrated from a sensory point of view under winery conditions. In particular, the fruity and lactic notes, as well as the markers associated with these descriptors, such as esters and diacetyl, were altered. Co-inoculation does not always favour fruity expression, nor does it reduce the diacetyl content and lactic aroma intensity. All of the trends were observed either in the production and degradation of metabolites, or by the development of an aromatic mask over the short and long term.

Surface-engineered Saccharomyces cerevisiae displaying α-acetolactate decarboxylase from Acetobacter aceti ssp xylinum.

To convert α-acetolactate into acetoin by an α-acetolactate decarboxylase (ALDC) to prevent its conversion into diacetyl that gives beer an unfavourable buttery flavour. We constructed a whole Saccharomyces cerevisiae cell catalyst with a truncated active ALDC from Acetobacter aceti ssp xylinum attached to the cell wall using the C-terminal anchoring domain of α-agglutinin. ALDC variants in which 43 and 69 N-terminal residues were absent performed equally well and had significantly decreased amounts of diacetyl during fermentation. With these cells, the highest concentrations of diacetyl observed during fermentation were 30% less than those in wort fermented with control yeasts displaying only the anchoring domain and, unlike the control, virtually no diacetyl was present in wort after 7days of fermentation. Since modification of yeasts with ALDC variants did not affect their fermentation performance, the display of α-acetolactate decarboxylase activity is an effective approach to decrease the formation of diacetyl during beer fermentation.

Effect of Sodium Chloride on α-Dicarbonyl Compound and 5-Hydroxymethyl-2-furfural Formations from Glucose under Caramelization Conditions: A Multiresponse Kinetic Modeling Approach.

This study aimed to investigate the kinetics of α-dicarbonyl compound formation in glucose and glucose-sodium chloride mixture during heating under caramelization conditions. Changes in the concentrations of glucose, fructose, glucosone, 1-deoxyglucosone, 3-deoxyglucosone, 3,4-dideoxyglucosone, 5-hydroxymethyl-2-furfural (HMF), glyoxal, methylglyoxal, and diacetyl were determined. A comprehensive reaction network was built, and the multiresponse model was compared to the experimentally observed data. Interconversion between glucose and fructose became 2.5 times faster in the presence of NaCl at 180 and 200 °C. The effect of NaCl on the rate constants of α-dicarbonyl compound formation varied across the precursor and the compound itself and temperature. A decrease in rate constants of 3-deoxyglucosone and 1-deoxyglucosone formations by the presence of NaCl was observed. HMF formation was revealed to be mainly via isomerization to fructose and dehydration over cyclic intermediates, and the rate constants increase 4-fold in the presence of NaCl.

An original method for producing acetaldehyde and diacetyl by yeast fermentation.

In this study a natural culture medium that mimics the synthetic yeast peptone glucose medium used for yeast fermentations was designed to screen and select yeasts capable of producing high levels of diacetyl and acetaldehyde. The presence of whey powder and sodium citrate in the medium along with manganese and magnesium sulfate enhanced both biomass and aroma development. A total of 52 yeasts strains were cultivated in two different culture media, namely, yeast peptone glucose medium and yeast acetaldehyde-diacetyl medium. The initial screening of the strains was based on the qualitative reaction of the acetaldehyde with Schiff's reagent (violet color) and diacetyl with Brady's reagent (yellow precipitate). The fermented culture media of 10 yeast strains were subsequently analyzed by gas chromatography to quantify the concentration of acetaldehyde and diacetyl synthesized. Total titratable acidity values indicated that a total titratable acidity of 5.5 °SH, implying culture medium at basic pH, was more favorable for the acetaldehyde biosynthesis using strain D15 (Candida lipolytica; 96.05 mg L−1 acetaldehyde) while a total titratable acidity value of 7 °SH facilitated diacetyl flavor synthesis by strain D38 (Candida globosa; 3.58 mg L−1 diacetyl). Importantly, the results presented here suggest that this can be potentially used in the baking industry.

Multiresponse kinetic modelling of Maillard reaction and caramelisation in a heated glucose/wheat flour system

The study describes the kinetics of the formation and degradation of α-dicarbonyl compounds in glucose/wheat flour system heated under low moisture conditions. Changes in the concentrations of glucose, fructose, individual free amino acids, lysine and arginine residues, glucosone, 1-deoxyglucosone, 3-deoxyglucosone, 3,4-dideoxyglucosone, 5-hydroxymethyl-2-furfural, glyoxal, methylglyoxal and diacetyl concentrations were determined to form a multiresponse kinetic model for isomerisation and degradation reactions of glucose. Degradation of Amadori product mainly produced 1-deoxyglucosone. Formation of 3-deoxyglucosone proceeded directly from glucose and also Amadori product degradation. Glyoxal formation was predominant from glucosone while methylglyoxal and diacetyl originated from 1-deoxyglucosone. Formation of 5-hydroxymethyl-2-furfural from fructose was found to be a key step. Multi-response kinetic modelling of Maillard reaction and caramelisation simultaneously indicated quantitatively predominant parallel and consecutive pathways and rate limiting steps by estimating the reaction rate constants.

Use of autochthonous lactic acid bacteria starters to ferment mango juice for promoting its probiotic roles

ABSTRACTStrains of Leuconostoc mesenteroides, Pediococcus pentosaceus, and Lactobacillus brevis were identified from mango fruits by partial 16S rDNA gene sequence. Based on the ability of producing mannitol and diacetyl, Leuconostoc mesenteroides MPL18 and MPL39 were selected within the lactic acid bacteria isolates, and used as mixed starters to ferment mango juice (MJ). Both the autochthonous strains grew well in fermented mango juice (FMJ) and remained viable at 9.81 log cfu mL−1 during 30 days of storage at 4°C. The content of total sugar of FMJ was lower than that of MJ, while the concentration of mannitol was higher than that of MJ, and the concentration of diacetyl was 3.29 ± 0.12 mg L−1. Among detected organic acids including citric acid, gallic acid, lactic acid, and acetic acid, only citric acid and gallic acid were found in MJ, while all detected organic acids were found in FMJ. The concentration of lactic acid of FMJ was the highest (78.62 ± 13.66 mM) among all detected organic acids. The DPPH radical scavenging capacity of FMJ was higher than that of MJ. Total phenolic compounds were better preserved in FMJ. The acidity and sweetness had a noticeable impact on the overall acceptance of the treated sample.

Impact ofPediococcusspp. on Pinot noir Wine Quality and Growth ofBrettanomyces

Pediococcus spp. were isolated from commercial wines from Oregon and Washington state, and the impacts of these isolates on the chemistry, microbiology, and sensory quality of Pinot noir wines were investigated. The pediococci isolates were inoculated into wines after alcoholic fermentation, and the wines were then chemically and sensorially analyzed after 60 days. All pediococci isolates partially degraded l-malic acid, with P. damnosus OW2 and P. parvulus OW7 completing malolactic fermentation (MLF). Despite having extensively large cell populations (>106 cfu/mL), the fermented wines had low concentrations of biogenic amines ( 5 mg/L). Production of d-lactic acid varied among the isolates, with strain OW7 producing the highest concentration (264 mg/L). Diacetyl concentrations also varied, with some wines containing low levels ( 15 mg/L). Furthermore, growth of some pediococci resulted in loss of red color and polymeric pigment content, potentially due to acetaldehyde degradation. Sensory analyses revealed differences in aroma (“floral”, “overall fruit”, “red fruit”, and “buttery”) and flavor (“sour” and “astringency”) among wines inoculated with different Pediococcus species or strains. Co-inoculation of P. parvulus and Brettanomyces bruxellensis resulted in wines having lower concentrations of 4-ethylphenol but reaching higher populations than in separate inoculations. This study has demonstrated the variability among Pediococcus species and strains in the production of various spoilage products and highlights the range of potential sensory effects these bacteria may have on a Pinot noir wine.

Effect of alkalization on the Maillard reaction products formed in cocoa during roasting

Cocoa beans are used in vast variety of food products whether as raw or after alkaline treatment. In this study, cocoa beans were treated with sodium carbonate or water and then roasted together with non-treated cocoa beans. To understand the effect of alkalization on Maillard reaction during cocoa roasting, changes in the concentrations of certain Maillard reaction compounds were determined. Additionally, changes in the concentrations of sugars and modification of lysine were also monitored. Alkaline treatment favored the degradation of sugars in cocoa together with roasting. The concentration of α-dicarbonyl compounds was higher in alkaline treated cocoa compared to water-immersed and non-treated cocoa. Roasting process substantially decreased the concentrations of 3-deoxyglucosone (3-DG), glucosone, glyoxal and diacetyl in alkaline treated cocoa. The concentrations of methylglyoxal and 5-hydroxymethylfurfural (HMF) increased in cocoa samples after roasting although this increase was less in alkaline treated cocoa compared to the other treatments. Most of the lysine was modified within 30min and fructoselysine, measured as furosine, gradually degraded independent of the treatments, but depending on temperature. N-ε-Carboxymethyllysine (CML) was doubled in alkaline treated cocoa although it did not change depending on the roasting.

Diacetyl content reduction in industrial brewer’s yeast through ILV2 disruption and BDH1 expression

Diacetyl is crucial to beer maturation because of its characteristic buttery taste. New industrial brewer’s yeast strains, including single ILV2 allele disruption (QI2), single ILV2 allele disruption and BDH1 overexpression (QI2GB1), and BDH1 overexpression (B1Y), were constructed by disrupting the gene (ILV2) involved in a-acetolactate synthesis and introducing the diacetyl reductase gene (BDH1). The diacetyl content and fermentation performance of the three recombinant strains were examined and compared. Results showed that the diacetyl concentration in QI2, QI2GB1, and B1Y decreased by 17.83, 28.26, and 9.57 %, respectively, compared with that in the host strain S2. The fermentation ability in terms of fermentation degree and major flavors yield of the three recombinant strains was similar to that of the host. This study may serve as a reference for the brewing industry and for research on diacetyl reduction.

Headspace and small-chamber studies of airborne diacetyl release from selected food flavoring mixtures: activity coefficients and air modeling implications

Laboratory studies were conducted to evaluate airborne release of diacetyl from selected mixtures simulating butter flavorings added to foods. The test materials included diacetyl (97% purity); 0.015%, 0.15%, 1.5%, and 3.0% diacetyl in a water/propylene glycol mixture; 1.5% diacetyl in deionized water or soybean oil; and 3% or 6% diacetyl in a commercial steam distillate from milk fermentation known as “butter starter distillate.” Diacetyl was quantified by gas chromatography with flame ionization detection. Expected concentration-dependent emission patterns based on liquid diacetyl content were demonstrated, but were significantly altered by mixture composition. Soybean oil and deionized water more readily released diacetyl when compared with starter distillate, propylene glycol solutions, and pure diacetyl. Measured diacetyl concentrations under static headspace and dynamic flow-chamber conditions were compared to estimated concentrations utilizing Raoult's law with published and fitted activity coefficient corrections for each mixture, indicating that published coefficients often understated the measured concentrations. It is concluded that headspace (static) and small-chamber (dynamic) measurements of airborne diacetyl provide data to assist in validating model-estimated airborne diacetyl concentrations by using mixture-specific activity coefficients. Implications of these empirical data for validating exposure estimates for diacetyl based on near-field/far-field modeling in workplace settings are discussed.

Comparison of carbonyl profiles from Czech and Spanish lagers: Traditional and modern technology

Beer is one from the most popular alcoholic beverages worldwide. For consumer acceptance, a significant factor is its flavour and taste; carbonyl compounds play an important role as indicators of the deterioration of flavour and aroma in beers. The aim of this study was to characterize differences in the carbonyl profile from Czech and Spanish beers, based on tradition and modern technology, respectively.Headspace solid-phase microextraction and gas-chromatography mass spectrometry were used to compare lager beers. The technique of on-fibre derivatization with O-(2,3,4,5,6-pentafluorobenzyl)hydroxylamine (PFBOA) was used to achieve satisfactory recovery and sensitivity.Statistical factor analysis showed three principal components, two of them explaining more than 79% of the variability and these results were related to ANOVA-significant difference analysis based on the country of origin. These two factors were related to Strecker aldehydes and Maillard products. PCA analysis scatterplot confirmed a significant difference between the Spanish and Czech beers, particularly with regard to the content of diacetyl and (E)-non-2-enal.

Diacetyl and 2,3-pentanedione exposure of human cultured airway epithelial cells: Ion transport effects and metabolism of butter flavoring agents

Inhalation of butter flavoring by workers in the microwave popcorn industry may result in “popcorn workers' lung.” In previous in vivo studies rats exposed for 6h to vapor from the flavoring agents, diacetyl and 2,3-pentanedione, acquired flavoring concentration-dependent damage of the upper airway epithelium and airway hyporeactivity to inhaled methacholine. Because ion transport is essential for lung fluid balance, we hypothesized that alterations in ion transport may be an early manifestation of butter flavoring-induced toxicity. We developed a system to expose cultured human bronchial/tracheal epithelial cells (NHBEs) to flavoring vapors. NHBEs were exposed for 6h to diacetyl or 2,3-pentanedione vapors (25 or ≥60ppm) and the effects on short circuit current and transepithelial resistance (Rt) were measured. Immediately after exposure to 25ppm both flavorings reduced Na+ transport, without affecting Cl− transport or Na+,K+-pump activity. Rt was unaffected. Na+ transport recovered 18h after exposure. Concentrations (100–360ppm) of diacetyl and 2,3-pentanedione reported earlier to give rise in vivo to epithelial damage, and 60ppm, caused death of NHBEs 0h post-exposure. Analysis of the basolateral medium indicated that NHBEs metabolize diacetyl and 2,3-pentanedione to acetoin and 2-hydroxy-3-pentanone, respectively. The results indicate that ion transport is inhibited transiently in airway epithelial cells by lower concentrations of the flavorings than those that result in morphological changes of the cells in vivo or in vitro.

Formation of α-dicarbonyl compounds in cookies made from wheat, hull-less barley and colored corn and its relation with phenolic compounds, free amino acids and sugars

Cookies are baked at elevated temperatures to obtain a desirable browning and flavor development, which are provided by Maillard reaction and caramelization. The drawback here is the formation of α-dicarbonyl compounds, and they are associated with many metabolic disorders besides involving in the development of the desired flavor and browning. Cookies are one of the major sources of α-dicarbonyl compounds in diet. This study was performed to evaluate the formation of α-dicarbonyl compounds in cookies prepared from different cereal flours consisting of diverse natural phenolic compounds. Flours of white wheat, hull-less barley and yellow, dark-red, blue, dark-blue colored corns containing different amount of phenolic compounds were selected as raw materials. A negative correlation was observed between total phenolic compounds and glyoxal, methylglyoxal and diacetyl concentrations after baking. α-Dicarbonyl compound-trapping ability of phenolic compounds was attributed to this reduction during baking of cookies. On the other hand, higher amounts of 3-deoxyglucosone and 1-deoxyglucosone were observed with increasing total phenolic compounds, which was in accordance with the higher sucrose hydrolysis.