Free amino acid composition of quince (Cydonia oblonga Miller) fruit (pulp and peel) and jam   总被引：2，自引：0，他引：2  

Silva BM  Casal S  Andrade PB  Seabra RM  Oliveira MB  Ferreira MA 《Journal of agricultural and food chemistry》2004,52(5):1201-1206

Twenty-one free amino acids present in several samples of quince fruit (pulp and peel) and quince jam (homemade and industrially manufactured) were analyzed by GC/FID. The analyses showed some differences between quince pulps and peels. Generally, the highest content in total free amino acids and in glycine was found in peels. As a general rule, the three major free amino acids detected in pulps were aspartic acid, asparagine, and hydroxyproline. For quince peels, usually, the three most abundant amino acids were glycine, aspartic acid, and asparagine. Similarly, for quince jams the most important free amino acids were aspartic acid, asparagine, and glycine or hydroxyproline. This study suggests that the free amino acid analysis can be useful for the evaluation of quince jam authenticity. It seems that glycine percentage can be used for the detection of quince peel addition while high alanine content can be related to pear addition.  相似文献   

Functional properties of purified vicilins from cowpea (Vigna unguiculata) and pea (Pisum sativum) and cowpea protein isolate     

Rangel A  Domont GB  Pedrosa C  Ferreira ST 《Journal of agricultural and food chemistry》2003,51(19):5792-5797

The major storage globulins (vicilins) of cowpea (Vigna unguiculata) and pea (Pisum sativum) seeds were purified by ammonium sulfate precipitation, and a semipurified cowpea protein isolate (CPI) was prepared by isoelectric precipitation. Some of the functional properties of these proteins, including solubility, foaming, and emulsifying capacities, were investigated and compared. The solubility of purified cowpea vicilin was reduced at pH 5.0, increasing markedly below and above this value. Pea vicilin exhibited poor solubility between pH 5.0 and pH 6.0, and CPI was little soluble in the pH range from 4.0 to 6.0. At neutral pH, the emulsifying activity indexes (EAI) of purified pea vicilin and CPI were 194 and 291 m(2)/g, respectively, which compare quite favorably to EAIs of 110 and 133 m(2)/g for casein and albumin, respectively. Remarkably, purified cowpea vicilin exhibited an EAI of 490 m(2)/g, indicating a very high emulsifying activity. Purified cowpea and pea vicilins exhibited lower foaming capacities and foam stablity indexes (FSI) than CPI. FSI values of 80 and 260 min were obtained for purified pea and cowpea vicilin, respectively, whereas a FSI value of 380 min was obtained for CPI. These results are discussed in terms of the possible utilization of purified vicilins or protein isolates from pea and cowpea in the food processing industry.  相似文献   

Chemical characterization of the aroma of Grenache rosé wines: aroma extract dilution analysis,quantitative determination,and sensory reconstitution studies     

Ferreira V  Ortín N  Escudero A  López R  Cacho J 《Journal of agricultural and food chemistry》2002,50(14):4048-4054

The aroma of a Grenache rosé wine from Calatayud (Zaragoza, Spain) has been elucidated following a strategy consisting of an aroma extract dilution analysis (AEDA), followed by the quantitative analysis of the main odorants and the determination of odor activities values (OAVs) and, finally, by a series of reconstitution and omission tests with synthetic aroma models. Thirty-eight aroma compounds were found in the AEDA study, 35 of which were identified. Twenty-one compounds were at concentrations higher than their corresponding odor thresholds. An aroma model prepared by mixing the 24 compounds with OAV > 0.5 in a synthetic wine showed a high qualitative similarity with the aroma of the rosé wine. The addition of compounds with OAV < 0.5 did not improve the model, whereas the aroma of a model containing only odorants with OAV > 10 was very different from that of the wine. Omission tests revealed that the most important odorant of this Grenache rosé wine was 3-mercapto-1-hexanol, with a deep impact on the wine fruity and citric notes. The synergic action of Furaneol and homofuraneol also had an important impact on wine aroma, particularly in its fruity and caramel notes. The omission of beta-damascenone, which had the second highest OAV, caused only a slight decrease on the intensity of the aroma model. Still weaker was the sensory effect caused by the omission of 10 other compounds, such as fatty acids and their ethyl esters, isoamyl acetate, and higher alcohols.  相似文献   

Organic Glasses: A New Class of Photorefractive Materials     

PM Lundquist  R Wortmann  C Geletneky  RJ Twieg  M Jurich  VY Lee  CR Moylan  DM Burland 《Science (New York, N.Y.)》1996,274(5290):1182-1185

The performance of amorphous organic photorefractive (PR) materials in applications such as optical data storage is generally limited by the concentration of active molecules (chromophores) that can be incorporated into the host without forming a crystalline material with poor optical quality. In polymeric PR systems described previously, performance has been limited by the necessity of devoting a large fraction of the material to inert polymer and plasticizing components in order to ensure compositional stability. A new class of organic PR materials composed of multifunctional glass-forming organic chromophores is described that have long-term stability and greatly improved PR properties.  相似文献   

Consumer Versus Resource Control in Freshwater Pelagic Food Webs     

MT Brett  CR Goldman 《Science (New York, N.Y.)》1997,275(5298):384-386

Models predict that food-web structure is regulated by both consumers and resources, and the strength of this control is dependent on trophic position and food-web length. To test these hypotheses, a meta-analysis was conducted of 11 fish (consumer)-by-nutrient (resource) factorial plankton community experiments. As predicted, zooplankton biomass was under strong consumer control but was weakly stimulated by nutrient additions; phytoplankton biomass was under strong resource control with moderate control by fish. However, the phytoplankton and zooplankton responses to nutrient additions did not follow theoretical predictions based on the number of trophic levels in the food web.  相似文献   

Carbon-based supercapacitors produced by activation of graphene     

Zhu Y  Murali S  Stoller MD  Ganesh KJ  Cai W  Ferreira PJ  Pirkle A  Wallace RM  Cychosz KA  Thommes M  Su D  Stach EA  Ruoff RS 《Science (New York, N.Y.)》2011,332(6037):1537-1541

Supercapacitors, also called ultracapacitors or electrochemical capacitors, store electrical charge on high-surface-area conducting materials. Their widespread use is limited by their low energy storage density and relatively high effective series resistance. Using chemical activation of exfoliated graphite oxide, we synthesized a porous carbon with a Brunauer-Emmett-Teller surface area of up to 3100 square meters per gram, a high electrical conductivity, and a low oxygen and hydrogen content. This sp(2)-bonded carbon has a continuous three-dimensional network of highly curved, atom-thick walls that form primarily 0.6- to 5-nanometer-width pores. Two-electrode supercapacitor cells constructed with this carbon yielded high values of gravimetric capacitance and energy density with organic and ionic liquid electrolytes. The processes used to make this carbon are readily scalable to industrial levels.  相似文献   

Analytical and sensorial characterization of the aroma of wines produced with sour rotten grapes using GC-O and GC-MS: identification of key aroma compounds     

Barata A  Campo E  Malfeito-Ferreira M  Loureiro V  Cacho J  Ferreira V 《Journal of agricultural and food chemistry》2011,59(6):2543-2553

In the present work, the aroma profiles of wines elaborated from sound and sour rot-infected grapes as raw material have been studied by sensory analysis, gas chromatography-olfactometry (GC-O), and gas chromatography-mass spectrometry (GC-MS), with the aim of determining the odor volatiles most likely associated with this disease. The effect of sour rot was tested in monovarietal wines produced with the Portuguese red grape variety Trincadeira and in blends of Cabernet Sauvignon and sour rotten Trincadeira grapes. Wines produced from damaged berries exhibited clear honey-like notes not evoked by healthy samples. Ethyl phenylacetate (EPhA) and phenylacetic acid (PAA), both exhibiting sweet honey-like aromas, emerged as key aroma compounds of sour rotten wines. Their levels were 1 order of magnitude above those found in controls and reached 304 and 1668 μg L(-1) of EPhA and PAA, respectively, well above the corresponding odor thresholds. Levels of γ-nonalactone also increased by a factor 3 in sour rot samples. Results also suggest that sour rot exerts a great effect on the secondary metabolism of yeast, decreasing the levels of volatiles related to fatty acids and amino acid synthesis. The highest levels of γ-decalactone of up to 405 μg L(-1) were also found in all of the samples, suggesting that this could be a relevant aroma compound in Trincadeira wine aroma.  相似文献   

The use of different doses of metamizol for post-operative analgesia in dogs     

Imagawa VH  Fantoni DT  Tatarunas AC  Mastrocinque S  Almeida TF  Ferreira F  Posso IP 《Veterinary anaesthesia and analgesia》2011,38(4):385-393

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Heterocyclic acetals from glycerol and acetaldehyde in Port wines: evolution with aging     

da Silva Ferreira AC  Barbe JC  Bertrand A 《Journal of agricultural and food chemistry》2002,50(9):2560-2564

In Port wine, isomers of glycerol and acetaldehyde acetals have been found at total contents ranging from 9.4 to 175.3 mg/L. During oxidative aging, the concentrations of the 5-hydroxy-2-methyl-1,3-dioxane and 4-hydroxymethyl-2-methyl-1,3-dioxolane isomers increased with time showing a linear correlation (r > 0.95). The flavor threshold for the mixture of the four isomers was evaluated in wine at 100 mg/L. Thus, it is expected that they contribute to "old Port wine" aroma in wines older than 30 years. Experiments with model solutions and wine clearly demonstrated that SO(2) combines with acetaldehyde and blocks the acetalization reaction.  相似文献   

Gas chromatography-olfactometry and chemical quantitative study of the aroma of six premium quality spanish aged red wines   总被引：5，自引：0，他引：5  

Culleré L  Escudero A  Cacho J  Ferreira V 《Journal of agricultural and food chemistry》2004,52(6):1653-1660

The aroma of six premium quality Spanish red wines has been studied by quantitative gas chromatography-olfactometry (GC-O) and techniques of quantitative chemical analysis. The GC-O study revealed the presence of 85 aromatic notes in which 78 odorants were identified, two of which-1-nonen-3-one (temptatively) and 2-acetylpyrazine-are reported in wine for the first time. Forty out of the 82 quantified odorants may be present at concentrations above their odor threshold. The components with the greatest capacity to introduce differences between these wines are ethyl phenols produced by Brettanomyces yeasts (4-ethylphenol, 4-ethyl-2-methoxyphenol, and 4-propyl-2-methoxyphenol), 2,5-dimethyl-4-hydroxy-3(2H)-furanone (furaneol), (Z)-3-hexenol, thiols derived from cysteinic precursors (4-methyl-4-mercaptopentan-2-one, 3-mercaptohexyl acetate, and 3-mercaptohexanol), some components yielded by the wood [(E)-isoeugenol, 4-allyl-2-methoxyphenol, vanillin, 2-methoxyphenol (guaiacol), and (Z)-whiskylactone], and compounds related to the metabolism (2-phenylethanol, ethyl esters of isoacids, 3-methylbutyl acetate) or oxidative degradation of amino acids [phenylacetaldehyde and 4,5-dimethyl-3-hydroxy-2(5H)-furanone (sotolon)]. The correlation between the olfactometric intensities and the quantitative data is, in general, satisfactory if olfactometric differences between the samples are high. However, GC-O fails in detecting quantitative differences in those cases in which the olfactive intensity is very high or if odors elute in areas in which the odor chromatogram is too complex.  相似文献