Beef authentication and retrospective dietary verification using stable isotope ratio analysis of bovine muscle and tail hair   总被引：2，自引：0，他引：2  

Osorio MT  Moloney AP  Schmidt O  Monahan FJ 《Journal of agricultural and food chemistry》2011,59(7):3295-3305

Stable isotope ratio analysis (SIRA) was used as an analytical tool to verify the preslaughter diet of beef cattle. Muscle and tail hair samples were collected from animals fed either pasture (P), a barley-based concentrate (C), silage followed by pasture (SiP), or silage followed by pasture with concentrate (SiPC) for 1 year (n = 25 animals per treatment). The (13)C/(12)C, (15)N/(14)N, (2)H/(1)H, and (34)S/(32)S isotope ratios in muscle clearly reflected those of the diets consumed by the animals. By applying a stepwise canonical discriminant analysis, a good discrimination of bovine meat according to dietary regimen was obtained. On the basis of the classification success rate, the (13)C/(12)C and (34)S/(32)S ratios in muscle were the best indicators for authentication of beef from animals consuming the different diets. Analysis of (13)C/(12)C and (15)N/(14)N in tail hair sections provided an archival record of changes to the diet of the cattle for periods of over 1 year preslaughter.  相似文献   

Creaming in black tea   总被引：1，自引：0，他引：1  

Jöbstl E  Fairclough JP  Davies AP  Williamson MP 《Journal of agricultural and food chemistry》2005,53(20):7997-8002

Tea cream is the precipitate formed as tea cools. Its formation has been studied by X-ray scattering, and it is shown that a higher tea concentration leads to earlier onset of creaming and larger particles and that addition of theaflavin and calcium promotes creaming. Association constants between the major components of black tea have been obtained using NMR and show that calcium and glucose enhance the self-association of caffeine, polyphenols, and theaflavin but have little effect on hetero-association. Glycosylation of a polyphenol reduced self-association and reduced binding to caffeine. We conclude that theaflavin is important for the initiation of creaming, forming nanoclusters of typically 3 nm diameter, whereas caffeine acts more to fill in the gaps within the clusters and thus adds to the bulk of tea cream without being necessary for its initiation. Tea creaming may be reduced by increasing the solubility of the polyphenols (i.e., by glycosylation) or by removing calcium. Tea cream; theaflavin; caffeine; small-angle X-ray scattering; NMR; colloid.  相似文献   

Characterization of selenium species in Brazil nuts by HPLC-ICP-MS and ES-MS     

Vonderheide AP  Wrobel K  Kannamkumarath SS  B'Hymer C  Montes-Bayón M  Ponce De León C  Caruso JA 《Journal of agricultural and food chemistry》2002,50(20):5722-5728

Brazil nuts have been classified as the foodstuffs that contain the highest level of unadulterated selenium, an essential trace element that appears to prevent cancer. To date, characterization of the selenium species in brazil nuts has not yet been investigated. In this work, various sample preparation approaches, including microwave extractions and enzymatic treatments, are examined with the goal of species preservation and subsequent selenium speciation; of these approaches, an enzymatic treatment with Proteinase K proved most effective. High-performance liquid chromatography (HPLC) separation strategies and inductively coupled plasma mass spectrometry (ICP-MS) detection schemes will also be presented. Extracts are evaluated against available standards for the commercially obtainable seleno-amino acids, selenomethionine (SeMet), selenoethionine (SeEt), and selenocystine (SeCys); selenomethionine was demonstrated to be the most abundant of these seleno-amino acids. Further characterization of unidentified selenium-containing peaks is attempted by the employment of several procedures, including electrospray-mass spectrometry (ES-MS). A peptide structure was identified; however, this was considered a tentative proposal due to the large background produced by the extremely complicated brazil nut matrix.  相似文献   

Analysis of bitter limonoids in citrus juices by atmospheric pressure chemical ionization and electrospray ionization liquid chromatography-mass spectrometry     

Manners GD  Breksa AP  Schoch TK  Hidalgo MB 《Journal of agricultural and food chemistry》2003,51(13):3709-3714

Improved analytical techniques for bitter limonoids in citrus and citrus juices can expedite the evaluation of freeze-induced citrus damage for citrus growers and juice quality for citrus juice producers. Microbore normal-phase and reverse-phase chromatography coupled to a mass spectrometer operating in a positive ion atmospheric pressure chemical ionization and electrospray ionization modes were found to be rapid, selective, and sensitive methods for the analysis of the bitter limonoids limonin and nomilin in citrus juices. Analysis was performed on a chloroform extract of citrus juice to which an internal standard was added. The methods are capable of detecting citrus limonoids in citrus juice in the 60-200 picogram range and quantifying citrus juice limonoids in concentrations as low as 120 picograms. An accurate "total limonoid bitterness" in citrus juice, as represented by the combined occurrence of limonin and nomilin, is easily determined by these methods.  相似文献   

低温贮藏下芒果的后熟   总被引：1，自引：0，他引：1  

Medl.  AP 《热带作物译丛》1991,(5):36-41

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农业机械中的振动控制     

Shar.  AP 郑铁志 《农机质量与监督》1990,(5):12-14

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THE SOCIETY OF AMERICAN BACTERIOLOGISTS. II     

Hitchens AP 《Science (New York, N.Y.)》1913,38(977):409-416

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香蕉和芒果成熟过程颜色变化的测定     

Medi.  AP 林野 《热带作物译丛》1993,(2):28-33

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油梨的落果和无籽果的形成与内源激素的关系     

董建华 《热带作物研究》1992,(3):64-71

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Vc等生长调节剂对橡胶树种子活力的影响   总被引：2，自引：0，他引：2  

王秉忠  董建华 《热带作物学报》1995,16(2):23-31

用０．１％浓度的Ｖｃ处理橡胶树种子，提高了种子的活力指数，并促进脂质降解和核酸合成等代谢活性，但对种子的水分吸收没有效应。  相似文献