ISO INTERNATIONAL STANDARD 18787 Firstedition 2017-11-30 Foodstuffs Determination of water activity Produits agricoles et alimentaires-Détermination de I'activitédel'eau Reference number AX ISO 18787:2017(E) ISO @ IS0 2017 IS0 18787:2017(E) COPYRIGHTPROTECTEDDOCUMENT @IS02017,Published inSwitzerland All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either ISO at the address below or ISO's member body in the country of the requester. ISO copyright office Ch. de Blandonnet 8 . CP 401 CH-1214 Vernier, Geneva, Switzerland Tel. +41 22 749 01 11 Fax +41 22 749 09 47 [email protected] www.iso.org ii @ IS0 2017 - All rights reserved IS0 18787:2017(E) Contents Page Foreword .iv 1 Scope. 2 Normative references 3 Terms and definitions. .1 4 Measurement principles 2 5 Apparatus. 2 5.1 Water activity measurement apparatus. 2 6 Reagents .3 6.1 Salts. 6.2 Standard solutions. 3 7 Sampling. .3 8 Procedure. 4 8.1 Sample preservation 4 8.2 Sample preparation 4 8.3 Testportion. 4 8.4 Storage before measurement (optional) 4 8.5 Measurement. 5 8.6 Calibration, adjustment and verification 5 9 Calculation and expression of results .5 10 Precision .6 10.1 Repeatability 6 10.2 Reproducibility 6 11 Test report .6 Annex A (normative) Water activity of saturated salt solutions at 25 °C .7 Annex B (informative) Interlaboratory studies .8 Bibliography 9 @ IS0 2017 - All rights reserved ii