Use of NIR spectroscopy and chemometrics for on-line process monitoring of ammonia in Low Methoxylated Amidated pectin production Christian B. Zachariassen a, * , Jan Larsen a , Frans van den Berg b ,Sbren Balling Engelsen b a Quality Control Development Group, CP Kelco ApS, Ved Banen 16, DK-4623 Lille Skensved, Denmark b Department of Dairy and Food Science, Centre for Advanced Food Studies, Food Technology, The Royal Veterinary and Agricultural University, Rolighedsvej 30, DK-1958 Frederiksberg C, Denmark Received 18 March 2004; received in revised form 13 October 2004; accepted 13 October 2004 Available online 20 December 2004 Abstract The development of an on-line process monitoring and control system for the automatic dosing of ammonia for production of Low Methoxylated Amidated (LMA) pectin is described. The system is based on on-line optical fibre Near Infra-Red (NIR) transmittance spectroscopy of the amidation liquid, consisting of ammonia, isopropylic alcohol, water and minor impurities. The focus in this paper is on the chemometric calibration development and validation, and the improvement on the ammonia dosing for the production. Feasibility studies revealed that the calibration for ammonia, based on NIR transmittance spectra (spectral region from 5300 to 11000 cm À1 ) is highly temperature dependent in the range À9–20 8C, but careful choice of spectral pre-processing and wavelength selection could eliminate the temperature dependency. Using the first derivative of the NIR spectra and the selection of the spectral region 5423–6658 cm À1 , the average Partial Least Squares regression prediction error was reduced to 1.75% of the full range of the initial calibration, as determined from an independently validated data set one full year after initial implementation in the factory. D 2004 Elsevier B.V. All rights reserved. Keywords: NIR spectroscopy; Ammonia; On-line; Process monitoring and control; Pectin 1. Introduction Low Methoxylated Amidated pectin (LMA pectin) is typically produced by amidating conventional High Methoxylated pectin (HM pectin) by ammonia in an alcoholic suspension [1–3]. Fluctuations in the feed of ammonia to the amidation reactors lead to less controlled amidation and thereby undesired product quality variation. In the traditional off-line measurements approach, the total consumption of ammonia could not be estimated accurately before amidation took place. Traditionally, the concentration of ammonia in the amidation reactors at the CP Kelco pectin manufacturing site in Denmark (Lille Skensved) was measured once every hour, through titration by skilled operators, in a non-laboratory environment. If judged necessary, the titrations would be followed up by manual dosing of ammonia. For these reasons, it was not feasible to closely monitor and act upon the fluctuations in ammonia concentration with sufficient accuracy. It was anticipated that an automated on-line, higher frequency determination of the ammonia concentration during amidation, coupled with an automated dosing of ammonia would result in a better control of the process. This would in turn improve process capability, product consistency and improve adher- ence to product specifications. After thorough feasibility studies, it was decided to pursue an on-line Near Infra-Red (NIR) transmittance setup to monitor the amidation reaction as input to a high frequency dosing-control of ammonia in the reactor fluids, i.e. optimize the reaction conditions. Based on the process and factory layout, it was decided to establish on-line NIR measurement points at three different tanks. Tank 1 and Tank 3 are auxiliary tanks; Tank 2 contains the liquids during the amidation reaction. Ammo- nia can be fed to the process liquids in Tank 2 from external 0169-7439/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.chemolab.2004.10.005 * Corresponding author. Tel.: +45 5616 5616; fax: +45 5616 9446. E-mail address: Christian.Zachariassen@cpkelco.com (C.B. Zachariassen). Chemometrics and Intelligent Laboratory Systems 76 (2005) 149 – 161 www.elsevier.com/locate/chemolab