Amount Of Ethylene Research Articles

Organic Acids and Volatile Flavor Components Evolved During Refrigerated Storage of Kefir

Kefir samples were prepared and transferred to sterile jars for storage at 4°C. After 0, 7, 14, and 21 d of storage, the pH, organic acid, and volatile flavor component content were determined to monitor possible flavor changes during storage. Stored samples were analyzed for organic acid (orotic, citric, pyruvic, lactic, uric, acetic, propionic, butyric, and hippuric) content by HPLC with UV detection at 275nm. Acetoin, ethanol, acetaldehyde, and diacetyl were monitored using gas chromatography equipped with a headspace autosampler. There was no significant decrease in average pH of samples between d 0 and 21 of storage (P>0.05). Lactic acid concentration increased during storage, reaching a maximum of 7739ppm by d 21. Orotic and citric acids increased slightly during storage. Although pyruvic and hippuric acids are produced during fermentation, neither was detected during storage. Acetic, propionic, and butyric acids were not detected during kefir storage. Ethanol concentrations increased during storage and reached 0.08% by d 21. The amounts of acetaldehyde and acetoin, common flavor substances in many cultured dairy products, increased during fermentation. Acetaldehyde content in kefir samples doubled from d 0 to 21, reaching a final concentration of 11μg/g. During storage, the concentration of acetoin decreased from 25ppm on d 0 to 16ppm on d 21. However, diacetyl, another common flavor component in cultured dairy products, was not detected during fermentation or storage.

Determination of Acetaldehyde Using Immobilized Aldehyde Dehydrogenase in a Flow System and Application to Analysis of Acetaldehyde Content in Liquors

The quantity of acetaldehyde was determined using an apparatus containing a reactor with immobilized aldehyde dehydrogenase in a flow line. NADH formed by an enzymatic reaction was fluorometrically detected. The optimal concentration of NAD+ in the carrier was determined. Various buffer types were examined as a carrier medium. When the pH of the carrier was 7.8, great peak areas due to NADH were observed for buffers of phosphate, pyrophosphate, HEPES, PIPES-(piperazine-N, N'-bis(2-ethanesulfonic acid)) and triethanolamine, compared with that for Tris buffer. In the pH range from 7.0 to 8.0, the peak area due to NADH increased with the increase of pH in the case of phosphate buffer, in contrast to the case of Tris buffer in which peak area decreased with the increase of pH. When the carrier composed of phosphate buffer (0.1M, pH7.8) was used, the calibration curve for acetaldehyde was linear in the range of 0.2-10μM (r=0.9994). Detection limit (S/N=3) was 0.1μM.Relative standard deviation of peak area at 2μM was 2.6% (n=7). The sampling rate was 40 samples h-1. This method was applied to the analysis of aldehyde in several liquors, and aldehyde content determined by the method agreed with that determined by a commercially available test-kit method.

Kinetic Spectrophotometric Determination of Acetaldehyde

ABSTRACT A method for determination of trace quantities of acetaldehyde based on its inhibition effect on the malachite green-sulfite reaction is described. The reaction is monitored spectrophotometrically by measuring the decrease in absorbance at 613 nm by a fixed time method of 60 seconds. The method allows the determination of acetaldehyde in the range of 0.2-10 μg/ml. The limit of detection was 0.1 μg/ml and the relative standard deviation for ten determinations of 2 μg/ml acetaldehyde was 1.8%. The method is applied to the determination of acetaldehyde in chemical industrial waste water with satisfactory results.

Acetaldehyde production by non-pathogenicNeisseria in human oral microflora: Implications for carcinogenesis in upper aerodigestive tract

Many epidemiological studies have identified chronic alcohol consumption as a significant risk factor for cancer of the upper aerodigestive tract (UAT) in human. Although acetaldehyde, the first metabolite from ethanol by alcohol dehydrogenase (ADH), is regarded as a carcinogen, how systemic production of acetaldehyde particularly affects the UAT remains unclear. In our study, we searched for the regional source of acetaldehyde in UAT, especially the involvement of bacteria in the human normal oral microflora. Here we demonstrate that, among the bacterial species identified from the human oral cavity, genus Neisseria had extremely high ADH activity and produced significant amounts of acetaldehyde when cultured with medium containing ethanol in vitro. The ability to produce acetaldehyde was more than 100-fold higher than that produced by any other genera we studied. Furthermore, alcohol ingestion influences the bacterial composition of the oral microflora, resulting in an increased proportion of Neisseria. Although Neisseria present in normal oral microflora is generally non-pathogenic, these findings suggest that this microbe can be a regional source of carcinogenic acetaldehyde and thus potentially play an important role in alcohol-related carcinogenesis in human UAT.

A novel approach for studying the thermal degradation, and for estimating the rate of acetaldehyde generation by the chain scission mechanism in ethylene glycol based polyesters and copolyesters

A novel approach to studying the thermal degradation of ethylene glycol based polyesters and copolyesters is described. The method involves the use of a gas chromatograph to measure the amount of acetaldehyde (a degradation by-product) generated over time at an elevated constant temperature for an extended period. We have found that at high temperatures, polyester resin show gradual decrease with time in the amount of acetaldehyde that is generated, and that this decline eventually approaches a near asymptotic value. A generalized polyester degradation mechanism for the generation and consumption of acetaldehyde is proposed which is consistent with the known literature. In this mechanistic picture, it is proposed that acetaldehyde is generated by three different routes involving first the hydroxyl-end groups, second the vinyl-end groups and finally the mid-polymer chain-scission. It is further suggested that of these, the hydroxyl and the vinyl end-group based acetaldehyde generation routes deplete with time leaving behind the last, but inexhaustible, chain-scission route. From the data in this study, it is possible to estimate the rate of acetaldehyde generation by this mid-polymer chain-scission route to be approximately 1.10–1.46 ppm per min at 280°C. For the various polyesters examined in this study, the above information was applied together with the (a) amount of residual acetaldehyde in the resin, (b) HO end-group concentration and (c) vinyl end-group concentration, to calculate the amount of acetaldehyde generation possible over a given period of time. This calculated [acetaldehyde] compared very well with the actual observed [acetaldehyde] over the same period of time as obtained by integrating the area under the curve in the [time]–[acetaldehyde] profiles, thereby validating the proposed mechanisms. In agreement with the thermodynamic principles, a near doubling of the chain-scission acetaldehyde generation rate was observed when the temperature was increased by 10 degrees centigrade. A further support for the mechanisms came from the observation that significant amounts of anhydride linkages are generated in polyesters upon exposure to heat for extended periods of time.

Release of fossil methane from mineral soil particles, and its implication for estimation of methane oxidation in a mineral subsoil

In a preliminary experiment we found that methane evolved from a sandy subsoil during aerobic incubation of shaken soil slurries. In the study presented here the methane was found to be released from the sand particles by mechanical weathering, caused by the grinding effect of the shaking. Large amounts of gas (about 0.5 ml gas g−1 soil) were extracted by intense grinding of the soil in gas tight serum vials. Methane was the main hydrocarbon in the emitted gas, but also a considerable amount of ethane was present, as well as minor amounts of heavier hydrocarbons (up to C6). The δ13C-values of the emitted methane and ethane were −33 ‰ and −29 ‰, respectively. Together these results demonstrate a thermogenic origin of the gas. This paper also reports the results of an incubation experiment where possible methane oxidation was looked for. If a possible release of methane is not accounted for, methane oxidation may be overlooked, as illustrated in this paper. Methane consumption was detected only in soil from 40 cm, in contrast to soil sampled at 100 cm and deeper where a slight production was measured. When methane oxidation was inhibited by dimethyl-ether, a significant release of methane was seen. The release was probably caused by chemical weathering. When this methane release was taken into account, methane oxidation was found to be present at all measured depths (40 to 200 cm). Fertilization with urea inhibited the methane oxidation at 40 cm but not at deeper layers. It is hypothesized that ammonia oxidizing bacteria were the main methane oxidizers in this mineral subsoil (deeper than 1 m), and that oxidation of methane might be a survival mechanism for ammonia oxidizers in ammonia limited environments.

Formation of malonaldehyde and acetaldehyde from the oxidation of 2'-deoxyribonucleosides.

2'-Deoxyribonucleosides, ribonucleosides, nucleobases, deoxyribose, and ribose were oxidized with Fenton's reagent. Malonaldehyde (MA) formed was derivatized with N-methylhydrazine to N-methylpyrazole, and acetaldehyde formed was derivatized with cysteamine to 2-methylthiazolidine. The resulting nitrogen-containing derivatives were quantitatively analyzed using gas chromatography with a nitrogen-phosphorus detector. MA and acetaldehyde were found in 2-deoxy-D-ribose and 2'-deoxyribonucleosides but not in ribonucleosides, nucleobases, and D-ribose. Amounts of MA formed from four deoxynucleosides were in the following order: 2'-deoxyguanosine > 2'-deoxycytidine > 2'-deoxyadenosine > or = thymidine. Amounts of acetaldehyde formed from four deoxynucleosides were in the following order: 2'-deoxycytidine > thymidine > 2'-deoxyadenosine > or = 2'-deoxyguanosine. The results suggest that the formation of MA and acetaldehyde requires a deoxy group on carbon 2' of a ribose moiety.

Photocatalytic decomposition of acetaldehyde over TiO 2/SiO 2 catalyst

To establish a promising method for the purification of air containing volatile organic compounds, photocatalytic decompositions of gaseous acetaldehyde over TiO 2 deposited on porous silica (TiO 2/SiO 2 catalyst) and over a platinized TiO 2/SiO 2 catalyst (Pt-TiO 2/SiO 2 catalyst) have been investigated including the capture of intermediates on the catalyst surface and regeneration of the deactivated catalyst by heating. Results of kinetic analysis show that these photocatalytic decompositions obey Langmuir-Hinshelwood kinetics. A comparison between the amounts of acetaldehyde decomposed and CO 2 produced reveals that about 10 % of acetaldehyde is missing. From the observation of the photocatalyst surface before and after the reaction by FT-IR spectroscopy, we conclude that this is due to the adsorption of intermediates such as formic acid and acetic acid on the porous catalyst as well as deposition of coke-like substances. When the Pt-TiO 2/SiO 2 catalyst is heated to a temperature above 473 K, these substances can be removed and discharged as CO 2. A series of results obtained in the present work suggests that the use of a Pt-TiO 2/SiO 2 catalyst will enable us to construct a multifunctional reaction process for air purification, in which volatile organic compounds are photocatalytically decomposed. The harmful intermediates formed during the reaction are partly adsorbed on the porous catalyst, remain in the reactor system, and together with deposited coke-like substances are converted into CO 2 by heat treatment of the catalyst. The catalyst is thus regenerated.

Is Acetaldehyde the Causal Agent in the Retardation of Carnation Flower Senescence by Ethanol?

Summary A 3 % ethanol holding solution inhibits the conversion of 1-aminocyclopropane-l-carboxylic acid (ACC) to ethylene, and doubles the vase-life of cut carnation flowers. Although the most effective concentration varies during experimentation, high concentrations of ethanol have negative effects. The most pronounced of these is the death of the ovary. Ethanol levels are much higher in the ovaries of treated flowers, than control flowers. A large amount of acetaldehyde was detected in the ovaries of treated flowers. Acetaldehyde was also detected in all other floral organs tested. Acetaldehyde is present in the head-space surrounding ethanol treated flowers, but not control flowers. This indicates that some of the ethanol applied as a post-harvest treatment is broken down to acetaldehyde, within the plant tissue, and released into the micro-atmosphere by the flower. If the conversion of ethanol to acetaldehyde is impeded, using an inhibitor of alcohol dehydrogenase, 4-methyl pyrazole, ethanol is no longer effective. Acetaldehyde, (1 and 3 %), as a holding solution, gave similar results as a 3 % ethanol holding solution. It appears that acetaldehyde, produced from ethanol, is the causal agent for the retardation of carnation flower senescence.

Formation of Acetaldehyde by the Lactobacillus Delbrückii Subsp. Bulgaricus and the Threonine Amino Acid in Dough Part Manufactured Products

ABSTRACTThe presented is a quantitative study of aromatic substances-carbonyl compounds: acetoin, glyoxal, methylglyoxal, diacetyl, acetaldehyde, propanal, isobutanal, isopentanal, hexanal in pre-ferment and in sour dough. During fermentation of pre-ferment and sour dough, L. bulgaricus produces greater quantity of acetaldehyde compared to L. brevis, L. casei and L. plantarum. It has been found that L. bulgaricus produces high quantity of acetaldehyde from the threonine amino acid during fermentation of pre-ferment and sour dough. Alongside, the threonine amino acid contributes to the increase of aromatic substances: acetoin, methylglyoxal, diacetyl, propanal, isobutanal, isopentanal, hexanal.

Determination of free acetaldehyde in total blood for investigating the effect of aspartate on metabolism of alcohol in mice

To explore the effect of sodium l-aspartate monohydrate (aspartate) as a NAD + regenerating agent for acetaldehyde in alcohol metabolism, a simple HPLC method has been developed for the measurement of free acetaldehyde in total mice blood digested with alcohol and aspartate. The blood samples were collected in EDTA Vacutainer tubes, and treated with 2,4-dinitrophenylhydrazine (DNP hydrazine) reagent in total blood. Acetaldehyde DNP hydrazone was extracted from total blood and analyzed by HPLC using an Ultrasphere ODS column. The compounds were separated using acetonitrile–water (50:50, v/v) as mobile phase and detected at 356 nm. The detection limit for acetaldehyde DNP hydrazone was 0.1 ppm. A blank determination was carried out for each analysis and subtracted from the results. The amount of acetaldehyde in blood has been determined as a function of time lapse after sole alcohol administration and aspartate ingestion followed by alcohol administration, respectively. This comparative analysis demonstrates that the ingestion of aspartate before the administration of alcohol dramatically decreases the aldehyde level in blood, and aspartate may be utilized as a prospective antagonist for acceleration of ethanol metabolism and prevention of acetaldehyde toxicity.

Diamond film deposition from the reaction of hydrogen atoms with acetaldehyde

Abstract Diamonds are deposited from a constant temperature flowing gas mixture, consisting of H, H 2 and Ar to which small amounts of acetaldehyde are added. Methyl radicals are rapidly generated from the reaction between H and CH 3 CHO. Deposits are formed on Si(111) wafers placed at different positions in the flow tube. Good quality diamonds are formed in the vicinity of the acetaldehyde inlet, but downstream deposits show few crystal facets. The best quality diamonds are formed at 500–600 °C, somewhat lower than the temperatures generally employed for CVD diamond deposition. Modeling of the gas phase chemistry indicates that methyl radicals are the only active species present in appreciable quantity in the region in which good diamond deposits are formed.

Role of Catalase in In Vitro Acetaldehyde Formation by Human Colonic Contents

Ingested ethanol is transported to the colon via blood circulation, and intracolonic ethanol levels are equal to those of the blood ethanol levels. In the large intestine, ethanol is oxidized by colonic bacteria, and this can lead to extraordinarily high acetaldehyde levels that might be responsible, in part, for ethanol-associated carcinogenicity and gastrointestinal symptoms. It is believed that bacterial acetaldehyde formation is mediated via microbial alcohol dehydrogenases (ADHs). However, almost all cytochrome-containing aerobic and facultative anaerobic bacteria possess catalase activity, and catalase can, in the presence of hydrogen peroxide (H2O2), use several alcohols (e.g., ethanol) as substrates and convert them to their corresponding aldehydes. In this study we demonstrate acetaldehyde production from ethanol in vitro by colonic contents in a reaction catalyzed by both bacterial ADH and catalase. The amount of acetaldehyde produced by the human colonic contents was proportional to the ethanol concentration, the amount of colonic contents, and the length of incubation time, even in the absence of added nicotinamide adenine dinucleotide or H2O2. The catalase inhibitors sodium azide and 3-amino-1,2,4-triazole (3-AT) markedly reduced the amount of acetaldehyde produced from 22 mM ethanol in a concentration dependent manner compared with the control samples (0.1 mM sodium azide to 73% and 10 mM 3-AT to 67% of control). H2O2 generating system [beta-D(+)-glucose + glucose oxidase] and nicotinamide adenine dinucleotide induced acetaldehyde formation up to 6- and 5-fold, respectively, and together these increased acetaldehyde formation up to 11-fold. The mean supernatant catalase activity was 0.53+/-0.1 micromol/min/mg protein after the addition of 10 mM H2O2, and there was a significant (p < 0.05) correlation between catalase activity and acetaldehyde production after the addition of the hydrogen peroxide generating system. Our results demonstrate that colonic contents possess catalase activity, which probably is of bacterial origin, and indicate that in addition to ADH, part of the acetaldehyde produced in the large intestine during ethanol metabolism can be catalase dependent.

Role of Catalase in In Vitro Acetaldehyde Formation by Human Colonic Contents

Ingested ethanol is transported to the colon via blood circulation, and intracolonic ethanol levels are equal to those of the blood ethanol levels. In the large intestine, ethanol is oxidized by colonic bacteria, and this can lead to extraordinarily high acetaldehyde levels that might be responsible, in part, for ethanol-associated carcinogenicity and gastrointestinal symptoms. It is believed that bacterial acetaldehyde formation is mediated via microbial alcohol dehydrogenases (ADHs). However, almost all cytochrome-containing aerobic and facultative anaerobic bacteria possess catalase activity, and catalase can, in the presence of hydrogen peroxide (H2O2, use several alcohols (e.g., ethanol) as substrates and convert them to their corresponding aldehydes. In this study we demonstrate acetaldehyde production from ethanol in vitro by colonic contents in a reaction catalyzed by both bacterial ADH and catalase. The amount of acetaldehyde produced by the human colonic contents was proportional to the ethanol concentration, the amount of colonic contents, and the length of incubation time, even in the absence of added nicotinamide adenine dinucleotide or H2O2. The catalase inhibitors sodium azide and 3-amino-1,2,4-triazole (3-AT) markedly reduced the amount of acetaldehyde produced from 22 mM ethanol in a concentration dependent manner compared with the control samples (0.1 mM sodium azide to 73% and 10 mM 3-AT to 67% of control). H202 generating system [β-D(+)-glucose + glucose oxidase] and nicotinamide adenine dinucleotide induced acetaldehyde formation up to 6- and 5-fold, respectively, and together these increased acetaldehyde formation up to 11-fold. The mean supernatant catalase activity was 0.53 ± 0.1 jumol/min/mg protein after the addition of 10 mM H202, and there was a significant (p < 0.05) correlation between catalase activity and acetaldehyde production after the addition of the hydrogen peroxide generating system. Our results demonstrate that colonic contents possess catalase activity, which probably is of bacterial origin, and indicate that in addition to ADH, part of the acetaldehyde produced in the large intestine during ethanol metabolism can be catalase dependent.

Characterization of Modified Silica Gel as a Source of Ethene for Standard Gaseous Mixtures

The application of chemically modified silica gel as a source of gaseous standard mixture containing ethene as a measured component is described. The surface of silica gel was chemically modified, which resulted in the formation of N-oxide of diethylaminopropylsilylated silica gel. This compound undergoes thermal decomposition at 245°C, yielding known amounts of ethene. The process of thermal decomposition of chemically modified silica gel took place in a desorber furnace connected on-line via a four-port valve to the device being calibrated. Such a solution provides convenient calibration of a GC/FID system after direct introduction of a stream of the generated mixture onto the front of a GC. It was found that 480 ± 15 mg of ethene can be generated per 1 g of the modified gel.

Dephosphorylation and aromatic nucleophilic substitution in nonionic micelles. The importance of substrate location

Reactions of OH-and F-with p-nitrophenyl diphenyl phosphate (pNPDPP) are inhibited by very dilute dodecyl (10) and (23) polyoxyethylene glycol (C12E10and C12E23, respectively), but rate constants become independent of surfactant concentrations at concentrations above the critical micelle concentration. Low charge density anions, e.g., ClO4-, inhibit and low charge density cations, e.g., (n-C7H15)4N+, accelerate reactions, probably by controlling concentrations of nucleophiles in the palisade layer. Diphenyl phosphorofluoridate, generated by attack of F-, is not detected but is rapidly hydrolyzed to phenyl phosphorofluoridate or diphenyl phosphate ion with loss of phenol or F-. The products are different in DMSO containing modest amounts (&lt;15 vol%) of water and no surfactant and are phenyl phosphorofluoridate and difluorophosphate ions generated by attack of F-on the initial phosphorofluoridate. These differences are consistent with the micellar palisade layer being water-rich. Although the nonionic surfactants do not intervene nucleophilically in reactions of pNPDPP, considerable amounts of ether are formed in the reaction of 2,4-dinitrochlorobenzene (DNCB), in C12E10and C12E23at high pH by attack of alkoxide ion with the relatively hydrophilic DNCB located close to the micellar surface. The differences in the chemistries of reactions of pNPDPP and DNCB appear to be associated largely with differences in locations of these substrates in the nonionic micelles.Key words: fluoridates, p-nitrophenyl diphenyl phosphate, 2,4-dinitrochlorobenzene, nonionic micelles, palisade layer.

Quiescent crystallization kinetics and morphology of isotactic polypropylene resins for injection molding. I. Isothermal crystallization

The quiescent isothermal crystallization kinetics of polypropylene was studied as a function of molecular weight (Mw), amount of ethene, and amount of maleic anhydride and acrylic acid grafting. Differential scanning calorimetry and polarized light optical microscopy were used to follow this kinetics. It was observed that the linear growth rate, G, decreased with the increase of Mw, but increased with the amount of ethene. In the grafted polymers, as the amount of grafting increased, G decreased. The fold surface free energy, σe, was found to increase with the increase in Mw. The heterophasic and grafted polymers had σe values higher than the homopolymers. All samples showed spherulitic morphology, except the acrylic acid-grafted polypropylene that showed axialitic morphology. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 68: 1159–1176, 1998

Effect of the Antioxidant 2‘‘-O-Glycosylisovitexin from Young Green Barley Leaves on Acetaldehyde Formaton in Beer Stored at 50 °C for 90 Days

Beer samples were stored at 50 °C for 90 days, and the amount of acetaldehyde in the samples was measured periodically by gas chromatography. Acetaldehyde in the beer sample was derivatized to 2-methylthiazolidine with cysteamine and quantitatively analyzed with a gas chromatograph equipped with a fused silica capillary column and a nitrogen−phosphorus detector. All beer samples contained acetaldehyde ranging from 30 to 80 μM before storage. The concentration of acetaldehyde in beer samples increased by 873% after 90 days of storage. Significant formation of off-flavor was observed in these samples. When a beer sample was stored at 50 °C for 10 days with 1 1 μg/mL of 2‘‘-O-glycosylisovitexin and butylated hydroxytoluene, the acetaldehyde content was reduced by 60 and 15%, respectively. On the other hand, addition of 1 μg/mL of α-tocopherol increased the acetaldehyde content by 18%. Keywords: Acetaldehyde; antioxidants; beer deterioration; off-flavor

Association of Oral Cancers With Alcohol Consumption: Exploring Mechanisms

Association of Oral Cancers With Alcohol Consumption: Exploring Mechanisms

Does ethylene play a role in thidiazuron-regulated somatic embryogenesis of geranium (Pelargonium × hortorum bailey) hypocotyl cultures?

The accumulation of ethylene in headspace of hypocotyl cultures of geranium (Pelargonium × hortorum Bailey) and its possible role in thidiazuron-mediated somatic embryogenesis was investigated. The action of ethylene as determined by various ethylene synthesis and action inhibitors was varied. Silver nitrate (AgNo3), aminoethoxyvinylglycine (AVG), and silver thiosulphate (STS) had no significant influence on the embryogenic response, while 1-methylcyclopropene (1-MCP) applied during the initial 3 d of induction or the expression phase, significantly increased the number of somatic embryos formed. Thidiazuron-treated tissues accumulated large quantities of ethylene within 6 h of culture, but the levels decreased after 12 h and reached very low levels after 3 d in culture. In the presence of acetylsalicylic acid (ASA), the levels of ethylene decreased by 20 to 50% during the first 48 h of culture. Analysis of endogenous auxin, cytokinins, and abscisic acid (ABA) indicated possible interactions of ethylene with other phytohormones during the induction of somatic embryos on geranium hypocotyl explants. Thidiazuron (10 µM) increased, while ASA decreased the levels of endogenous auxin, cytokinins, and abscisic acid during this period of induction.