海鲜，水产，鱼类中挥发性氨基氮，TVBN检测方案(定氮仪)

APPLICATION NOTEF&F-K-004-2013/A2 TVBN DETERMINATION IN FISHCONWAY AND BYRNE METHOD Determination of the Total VolatileBasic Nitrogen (TVBN) in Fishaccording to Conway and Byrne method Reference： Conway and Byrne method (1933) Tested with VELP Scientifica UDK 159 Automatic Kjeldahl Distillation&Titration System (Code F30200150) Introduction Fish is one of the most easily perishable food because of its peculiar chemical composition； therefore， it's important toevaluate its freshness， both for commercial aspects， and from food safety and hygiene point of view. The proteindegradative processes， occurring during fish perishing， produce an increase of typical substances， such as ammoniaand volatile nitrogen compounds， and the concentrations of which are index of the deterioration status. The TVBN (Total Volatile Basic Nitrogen) is a method of analysis that quantifies the presence of nitrogenous compounds (ammonia and dimethyl and trimethyl amine) in fish from the sea or from river， revealing the degree of freshness. TVBN Determination in fresh and frozen fish One of the routine methods which may be used to check the TVBN is the “microdiffusion method" described by Conwayand Byrne (1933). The sample is alkalized by magnesium oxide (MgO). Then the TVBN is determined by steam distillation and titration：the Automatic Distillation and Titration System UDK 159 is suitable for this kind of application. Sample Standard FAPASCanned FishRef. NumberT25100QCQuantity150 gAnalyteTotal Volatile Basic NitrogenUnitsmg/100 gAssigned value25，03Satisfactory range20，03-30，03 Sample Preparation In this specific case， the standard doesn't need to be homogenized. Weight 10 g of sample and place it in a test tube along with 1 Antifoam S (Code CT0006600). Distillation and Titration Condition the UDK 159 unit by performing the Automatic Check up in Menu-System and a Wash down.The following parameters must be set： ●·H2O (dilution water)： 50 ml NaOH (32%)： none H3BO3 (4% with indicators)： 30 ml ● H2SO4 (0.1N) as titrant solution Steam power：30 % For collecting 100 ml in 10 min as required from the Conway Method (1933)， the steam power 30% must be set. In order to avoid damaging the distillation unit， it’s necessary to NOT use the "removal of distillation residues” function.Once accepted the blanks average， the samples have been distilled in series. Position the test tube with the sample into the unit UDK 159 and start the distillation. Results The results are calculated in mg of TVBN/100 g. Sample quantity (g) H2SO4(ml) TVBN mg/100 g 10.063 1.494 20.791 10.073 1.477 20.534 10.037 1.454 20.287 10.173 1.475 20.305 10.443 1.512 20.276 9.995 1.442 20.204 10.362 1.504 20.326 10.535 1.525 20.272 9.972 1.455 20.433 10.359 1.498 20.251 Average ± SD% 20.368±0.177 RSD%* 0.9 For the test with UDK 159， 0.065 ml of H2SO4 0.1 N has been accepted as blank value. Conclusion The obtained results are reliable and reproducible in accordance with the expected values， with a low relative standarddeviation (RSD <1%)， that means high repeatability.This makes the UDK 159 suitable for TVBN determination.The distillation and colorimetric titration system is able to provide precise and reliable results.Benefits of Conway and Byrne method by using UDK 159 are： High level of precision and reproducibility High productivity Worldwide official method Time saving Affordable equipment cost Moderate running costs Partly unsupervised Copyright C VELP Scientifica. All rights reserved.No part of this publication may be reproduced or transmitted in any form or for any purpose without the express permission of VELP.VELP Scientifica， Italy Tel：+ Fax： + www.velp.com 利用VELP UDK 159进行海鲜的新鲜度测定：本应用从样本准备，方法设计以及结果分析几个方面对挥发性氨基氮的测定进行介绍。在测定TVBN过程中UDK 159凯式定氮仪的蒸汽强度可以从10-100%之间调节，能够更有效充分低接收挥发性盐基氮。