International Journal of Engineering & Technology IJET-IJENS Vol:09 No:10 8 90910-2727 IJET-IJENS © December 2009 IJENS I J E N S Abstract — The characterizations of coconut milk fouling deposits formed during pasteurization process at temperature from 70 to 80ºC were investigated. Both in-situ (using lab-scale plate heat exchanger) and ex-situ methods (using shakable water bath) were applied in preparing the fouling sample and for cleaning study. A few microanalyses such as proximate analysis, texture analysis and microstructure analysis were carried out to examine the characteristics of the coconut milk fouling deposits. Selection of raw material and determination of the optimal process parameters for pasteurization process were done to obtain a typical pasteurization condition as applied in the coconut milk product industry in Malaysia. The changes of the overall heat transfer coefficient (U) during the process were studied. The removal/cleaning of coconut milk fouling deposit was also studied at 80°C, 2 LPM and with 2 %V/V hydroxide of alkaline solution (optimal condition obtained from ex-situ method). The results indicate that fouling period was occurred during coconut milk pasteurization and it caused a resistance to heat transfer. Coconut milk fouling deposit which contains of high fat content (29.25%) can be removed by applying single stage clean-in-place (CIP) method with alkaline solution. The factors causing fouling were studied Index Term— coconut milk, fouling deposit, cleaning, pasteurization process, plate heat exchanger I. INTRODUCTION Fouling deposit generally is defined as the deposition of soils or unwanted material on the heat transfer surfaces. Despite a great technical achievement in the design and manufacture of heat exchangers in the past two decades, the problem of fouling deposit on heat exchanger surfaces still remains one of the major unresolved problems in thermal science. In food processing, fouling (i) causes increase in pressure drop through the plant, (ii) lowers the effectiveness of heat transfer, (iii) limits the operational time of the plant, and most importantly (iv) endangers plant and process sterility [1]. It also compromise product quality by cross-contamination or This work was supported by Universiti Putra Malaysia. N. Ab. Aziz is with the Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, MALAYSIA (corresponding author, phone: +603- 89464302; fax: +603-89464440; e-mail: shekeen@eng.upm.edu.my). F. S. Taip is with the Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, MALAYSIA (e-mail: saleena@eng.upm.edu.my). N. Muda is with the Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, MALAYSIA (e-mail: noraziah@eng.upm.edu.my). H. Y. Law is a student in Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, MALAYSIA. C. I. Ong is a student in Faculty of Engineering, Universiti Putra Malaysia, 43400 UPM, Serdang, MALAYSIA. microbial growth [2]. Fouling condition in a heat exchanger depends on local thermal and hydraulic conditions, together with the chemistry and process history of the fluid [3]. In order to produce consistent and quality product which safe for human consumption, frequently cleaning of the plant is needed. It is important to study the fouling deposit characteristics and cleaning mechanisms in order to get the best performance of cleaning. CIP (clean-in-place) technique is the common cleaning practice used in industry nowadays. It is used in processing plant to clean tanks, piping and workspaces between production batches by automatically recirculating cleaning chemical and rinsing liquid. There are two types of CIP treatment [4]: 1. Two-stage cleaning, using alkali commonly sodium hydroxide and acid wash (e.g. nitric or phosphoric acid). 2. Single-stage cleaning, using formulated detergents containing wetting and other surface agents as well as chelating compounds. Coconut milk is the liquid obtained by mechanical extraction of grated coconut meat. Heating process normally takes place in a system of indirect plate heat exchangers, which consists of preheating, heating, and cooling sections. Pasteurization process has been found to be a short-term preservation process in which the coconut milk is heated to pasteurization temperature of 72-75ºC for 20 min [5]. Coconut milk is a complex biological fluid, typically composed of fat, protein, carbohydrates, and minerals as a milky white oil-in- water emulsion; a percentage of fat is adjusted depending upon local requirement, between 15-40%. At high temperature, some components can lose their rheological properties and/or denature to form a fouling deposit on the heating surface. As with other food fouling, the rate of deposit build-up is quite rapid. Thus coconut milk fouling deposit can affect greatly the performance of the process. This work aims to understand the influence of process condition and raw coconut milk properties on fouling and cleaning, which can provide a fundamental knowledge for future studies in this field. The deposit characteristics such as, strength, texture, composition, microstructure and absorption rate, are important in determining the fouling rate and cleaning performance of heat exchanger. The findings from these works provide preliminary data of coconut milk fouling deposit characteristics and its cleaning process. Preliminary Work on Coconut Milk Fouling Deposits Study Hui Yin Law, Chin Im Ong, Norashikin Ab. Aziz, Farah Saleena Taip and Noraziah Muda