Quinones are a group of semi-volatile organic substances, ubiquitous in nature, belonging to the class of oxygenated polycyclic aromatic hydrocarbons (Oxygenated PAH). These compounds are formed in ...biogenic processes, through the oxidative metabolism of endogenous compounds, such as catecholamines, estrogen hormones and xenobiotics, as well as directly emitted to the atmosphere, through the incomplete combustion of organic matter, especially the fossil fuels. Additionally, the quinones are formed in the atmosphere by photooxidation of Polycyclic Aromatic Hydrocarbons (PAH). Their reduction products (semiquinones and hydroquinones) are of toxicological interest, due to their ability in generate reactive oxygen species, which may cause damage to membranes, proteins and DNA and, among others damages, may lead to carcinogenesis and induce apoptosis. The most frequently used analytical methods for quantification of quinones in the atmosphere, either in its original form or as derivatized compounds, are high-performance liquid chromatography coupled to mass spectrometry (HPLC-MS) and gas chromatography coupled to mass spectrometry (GC-MS). This review aims to highlight the chemical properties of 1,2-naphthoquinone, 1,4-naphthoquinone, 1,4-benzoquinone, 9,10-phenanthraquinone and 9,10-anthraquinone, the more volatile, reactive and abundant quinones in the atmosphere, as well as the methods usually employed for their determination.
Apple volatile aroma depends of complex interaction among organic compounds. The aim of the present study was to evaluate the effect of 1-methylcyclopropene (1-MCP) application on volatile profile ...and quality on 'Royal Gala ' apples produced in Southern Brazil and stored under controlled atmosphere condition (CA; 1.0kPa O.sub.2+1.2kPa CO.sub.2; 0.5 ± 0.1°C; 94 ± 1% relative humidity). Volatile profile was determined after eight month of CA storage plus 7 days of shelf life via solid-phase microextraction (HS-SPME) and analyzed by gas chromatography coupled to mass spectrometer. In the volatile profile were identified 8 esters, 11 alcohols, 6 aldehydes, 6 acids, 2 ketones, 1 ether and 1 terpene. 1-MCP application reduced significantly the main volatile compounds production by 'Royal Gala ' apples produced in Southern Brazil. Its application decreases significantly the esters production, especially 2-methyl-butyl acetate and hexyl acetate, compared to 'Royal Gala ' apples storage under CA. 1-methylcyclopropene application decrease ethylene production and respiration rate. Apples treated with 1-MCP exhibit higher hexanal and 2(E)-hexenal production. Key words: Malus domestica, solid phase microextraction, fruits, GC/MS. O aroma de macas depende de uma complexa interacao entre compostos organicos. O objetivo do presente estudo foi avaliar o efeito da aplicacao de 1-metilciclopropeno (1-MCP) sobre o perfil volatil e a qualidade de macas 'Royal Gala'produzidas no Sul do Brasil e armazenadas em atmosfera controlada (AC; 1,0kPa O.sub.2+1,2kPa CO.sub.2; 0,5 ± 0,1°C; 94 ± 1% umidade relativa). O perfil volatil foi determinado apos oito meses de armazenamento mais seis dias de vida de prateleira atraves de micro extracao em fase solida (HS-SPME) e analisado por cromatografia gasosa acoplado a espectrofotometro de massa. No perfil volatil, foram identificados 8 esteres, 11 alcoois, 6 aldeidos, 6 acidos, 2 cetonas, 1 eter e 1 terpeno. Aplicacao de 1-MCP reduziu significativamente os principais compostos volateis produzidos pela maca 'Royal Gala'. Sua aplicacao reduziu significativamente a producao de esteres, especialmente 2-metil-butil acetato e hexil acetato, quando comparado a maca 'Royal Gala'produzidas no Sul do Brasil e armazenada em AC. Aplicacao de 1-metilciclopropeno reduziu a producao de etileno e respiracao dos frutos. Macas tratadas com 1-MCP apresentam maior producao de hexanal e 2(E)-hexenal. Palavras-chave: Malus domestica, micro extracao em fase solida, frutos, GC/MS.
Volatile organic compounds as biomarkers of the freshness of poultry meat packaged in a modified atmosphere Tomankova, J., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Masa; Borilova, G., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Masa; Steinhauserova, I., Veterinarni a Farmaceuticka Univ., Brno (Czech Republic). Ustav Hygieny a Technologie Masa ...
Czech Journal of Food Sciences,
01/2012, Letnik:
30, Številka:
5
Journal Article
Recenzirano
Odprti dostop
Volatile organic compounds (VOCs) in the packing of chicken meat in a modified atmosphere (MA) were qualitatively and quantitatively evaluated. Seventy-two samples of chicken hindquarters were stored ...under two different MAs (70% O2, 30% CO2, and 70% argon, 30% CO2) for 20 days. Analyses were performed on Days 0, 4, 8, 12, 16, and 20. VOCs in the headspace samples were detected and quantified by gas chromatography/mass spectrometry every fourth day of storage. Pentamethylheptane, dimethylsulphide, dimethyl disulphide, dimethyl trisulphide, dimethyl tetrasulphide, hydrogen sulphide and ammonia were detected. Pentamethylheptane and ammonia had similar values for both MAs. The other compounds were found only in argon MA from the Day 16 of storage with a subsequent increase of values. The measured values for dimethylsulphide were 10.7 and 13.8 mg/L, for dimethyl disulphide they were 1.9 and 10.7 mg/L, dimethyl trisulphide levels were 15.7 and 19.3 mg/L and dimethyl tetrasulphide levels were 93.2 and 418.3 mg/L for Day 16 and 20, respectively. The hydrogen sulphide level was detected from 80 to 370 mg/L after the 8th day of storage. We showed that the argon MA is less suitable for packaging raw chicken parts than the oxygen MA in view of the increased amount of microflora and unpleasant odour as assessed by sensory analysis. Oxygen prolonged the shelf life by about four days in comparison with argon. Sensory evaluation was similar for both atmospheres after air exhaustion.
Tree rings, carbon dioxide, and climatic change Jacoby, G.C. (Lamont-Doherty Earth Observatory, Palisades, NY.); D'Arrigo, R.D
Proceedings of the National Academy of Sciences - PNAS,
08/1997, Letnik:
94, Številka:
16
Journal Article
Recenzirano
Odprti dostop
Tree rings have been used in various applications to reconstruct past climates as well as to assess the effects of recent climatic and environmental change on tree growth. In this paper we briefly ...review two ways that tree rings provide information about climate change and CO2: (i) in determining whether recent warming during the period of instrumental observations is unusual relative to prior centuries to millennia, and thus might be related to increasing greenhouse gases; and (ii) in evaluating whether enhanced radial growth has taken place in recent decades that appears to be unexplained by climate and might instead be due to increasing atmospheric CO2 or other nutrient fertilization. It is found that a number of tree-ring studies from temperature-sensitive settings indicate unusual recent warming, although there are also exceptions at certain sites. The present tree-ring evidence for a possible CO2 fertilization effect under natural environmental conditions appears to be very limited
Ocean Circulation and Climate Siedler, Gerold; Gould, John; Church, John A
2001, 2001-03-27, Letnik:
v.Volume 103
eBook
The book represents all the knowledge we currently have on ocean circulation. It presents an up-to-date summary of the state of the science relating to the role of the oceans in the physical climate ...system.The book is structured to guide the reader through the wide range of World Ocean Circulation Experiment (WOCE) science in a consistent way. Cross-references between contributors have been added, and the book has a comprehensive index and unified reference list.The book is simple to read, at the undergraduate level. It was written by the best scientists in the world who have collaborated to carry out years of experiments to better understand ocean circulation.
The aroma profiles of two sweet cherry cultivars (Kordia and Vanda) were investigated during storage at different oxygen and carbon dioxide levels and at a low temperature using solid phase ...microextraction gas chromatography combined with mass spectrometry (SPME-GC-MS). The most abundant aroma volatiles observed in both sweet cherry cultivars were alcohols, esters, terpenoids and aldehydes. Fifteen alcohols (but principally ethan-1-ol, (E)-2-hexen-1-ol and phenethyl alcohol) provided approximately 39% of the total volatile production and eight esters (principally (E)-2-hexenyl acetate and pentyl butyrate) were responsible for another 39% of the volatile production. Four terpenoids (principally limonene and alpha-linalool) were responsible for a further 15% of volatile production, and 10 aldehydes (principally (E)-2-hexenal and (E)-2-octen-1-al) were responsible for the remaining 7% of total volatile production. However, out of all the volatile compounds detected, a total of just 6 compounds (phenethyl alcohol, (E)-2-hexenal, (E)-2-octen-1-al, pentyl butyrate, (E)-2-hexenyl acetate and limonene) made up 80% of the total volatile production. Fruit stems remained green during all 54 days of the storage period, although one tenth of the stems slowly dessicated in each of the three controlled atmospheres. This is in marked contrast to the stems of fruit held in a regular atmosphere, which turned completely brown.
This second edition retains the general structure of the first edition, buthas been updated in the light of recent oceanographic research, and improvedas a teaching text on the basis of feedback from ...past students and otherreaders.
Notable additions include new sections addressing the topic ofnumerical modelling, and more discussion of natural oscillations in theocean-atmosphere system (previously confined to the El Niño phenomenon). Inparticular, the Chapter on the North Atlantic now includes a discussion ofthe North Atlantic Oscillation, as well as of the Great Salinity Anomaly. Inthe final Chapter, treatment of water mass formation has been updated toreflect recent ideas about the processes involved and how they relate toclimatic change over different time-scales, from decades to millennia.
High quality full colour diagramsSubstantial chapter summaries ideal for revisionAnswers, hints and notes for questions at back of the book
Orientadores: Maria Aparecida Silva, Lauro Euclides Soares Barata
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
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Previous issue date: 2007
Resumo: Modificações da atmosfera ao redor do produto têm sido utilizadas para prolongar o armazenamento de frutas e vegetais frescos. Atualmente, esta técnica tem-se estendido também a processos de secagem, influenciando características sensoriais do produto desidratado. Durante a secagem de frutas, uma fração de compostos volúveis importantes para a composição do aroma é perdida durante a retirada da água. Para muitos produtos alimentícios, a presença de voláteis é um fator fundamental de qualidade. Com o objetivo de verificar a influência da atmosfera modificada na retenção de compostos voláteis, o presente trabalho analisa os experimentos de secagem de abacaxi (Smooth Cayenne) sob composição normal do ar e atmosfera modificada por etanol (0,5% v/v), variando temperatura e velocidade do ar, avaliando a variação da composição volátil durante o processo. Os experimentos de secagem foram conduzidos num túnel, feito com paredes de policarbonato e um sistema de aquisição para controle de dados, onde se pôde acompanhar continuamente o peso da amostra e controlar a temperatura do gás de secagem. Para quantificar a retenção dos voláteis, foi utilizada a metodologia de microextração por fase sólida acoplada a cromatógrafo gasoso com espectrômetro de massa (SPME-GC-MS). A modificação da atmosfera de secagem com vapor de etanol promoveu uma evaporação mais intensa da água, assim como uma maior retenção de compostos voláteis. A composição volátil mudou significativamente durante a secagem, não somente pela perda de alguns componentes, mas também pela produção de outros
Abstract: Modifications of the atmosphere surrounding the product have been used to prolong the storage of fresh fruits and vegetables. Currently, this technique has also been extended to drying processes, influencing sensorial characteristics of the dried product. During the drying of fruits, a fraction of the volatile compounds that are important for the aroma composition is lost during water removal. For many food products, the presence of volatile is a basic factor of quality. To verify the influence of the modified atmosphere on volatiles retention, the present work analyzed experiments of pineapple (Smooth Cayenne) drying under normal air composition and in atmosphere modified by ethanol (0.5% v/v), varying temperature and air velocity, evaluating the variation of the volatile composition of the product during the process. The drying experiments were carried out in a tunnel, with walls made of policarbonate and an acquisition system for data control, which could continuously monitor the weight of the sample and also control the temperature of the drying gas. To quantify the volatiles retention, a solid phase microextration methodology coupled to gas chromatography-mass spectrometry (SPME-GC-MS) was used. The modification of the drying atmosphere with ethanol vapour promoted more intense water evaporation as well as higher volatiles retention. The volatile composition was changed significantly during drying, not only due to the loss of some compounds, but also due to the production of others
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