ABSTRACT: Margarines made from refined, bleached, and de- odorized palm oil at different emulsion temperatures showed no significant difference in their consistency, polymorphic be- havior, and solid fat content (SFC) during storage, although dif- ferences were observed during processing. The emulsion tem- peratures studied were 40, 45, and 50°C, with other parameters such as emulsion flow rates, tube cooler temperature, and pin rotor speed kept constant. The SFC developed during process- ing and storage at 28°C was measured to evaluate the quality of margarine. The emulsion contained no SFC at any emulsion temperature studied. However, the amount of SFC in the per- fector or tube cooler unit increased to 15.9, 13.9, and 15.6% in margarine produced at emulsion temperatures of 40, 45, and 50°C, respectively. At 40°C, the lowest SFC was developed dur- ing storage even though this margarine had the highest consis- tency. The softening point of this sample was moderately high and closely related to the type of crystal developed, which was a mixture of β′ and β crystals. Emulsion at 45°C gave the most stable margarine consistency and SFC with crystal in the β′ form even after the fourth week. At 50°C, moderately soft product was produced, which might be undesirable for some applica- tions, although the crystals were in the β′ form. Paper no. J9899 in JAOCS 79, 1163–1168 (December 2002). KEY WORDS: Emulsion temperature, palm oil, solid fat con- tent (SFC), tube cooler. Margarine and table spreads are water-in-oil emulsions. The aqueous phase consists of water, salt, and preservatives (1,2). The oil phase, which contributes to the polymorphic behavior of margarine, is a blend of oils and fats (3–5). Lecithin, dis- tilled MAG, and distilled DAG are common emulsifiers added to the fat phase together with flavoring agents, antioxi- dants, and coloring agents. Emulsification is a process in which the water and oil phases are mixed to form a water-in-oil emulsion with the as- sistance of an emulsifier (1,6–8). Emulsification is a very im- portant step in margarine processing because it ensures the de- velopment of the desired crystal form (7). Different types of churns have been used to produce good margarine. These are jacketed with a flow of hot or cold water to allow temperature control of the emulsion. The temperature of the oil phase is maintained at 2–3°C above its m.p., whereas the aqueous phase is held at 7–10°C. After emulsification, the temperature in the churn is lowered to 7–8°C below the m.p. (7) to initiate the development of crystal nuclei. The emulsion is agitated for 10–15 min and, prior to its passing into the tube cooler unit, the temperature is raised to 2–3°C above the melting point. This heating avoids formation of microscopically sized crys- tals but does not destroy the previously formed nuclei. Some studies have shown that temperature control during emulsification influences the solidification and plasticizing process and the final texture of the margarine (7,9). However, other studies have considered the emulsification step less criti- cal than chilling (9,10). Borwanker (10) suggested that emulsi- fication should be done at 45–50°C when all the oil is liquid. However, according to Andersen and Williams (7), the optimal emulsification temperature varies with the oil blend and its m.p. The common practice for most margarine manufacturers in Malaysia is to keep the blend at 55–60°C before emulsification and maintain the emulsion tank at 50°C (Foo, T.K., personal communciation; Tan, T.K., personal communication). Lowering the emulsion temperature to provide precrystal- lization in the emulsion tanks, as suggested by Andersen and Williams (7), is less practical, and it would be preferable to install an extra tube cooler unit in the system (11). Partial crystallization of margarine emulsion could take place in the tube cooler and be completed before the product leaves the perfector plant after passing through the intermediate crystal- lizer and pin rotor. This study was undertaken to determine whether emulsion temperature in the mixing tank has an effect on the physical properties of the final product during storage. MATERIALS AND METHODS Materials. Refined, bleached, and deodorized (RBD) palm oil was obtained from a local refinery. The RBD palm oil had a slip melting point (SMP) of 35.1°C, dropping point of 38.6°C, and crystallization temperature of 22°C. Other ingredients in- cluded emulsifier (distilled MAG, 90% monoester, SMP 69°C; source: fully hydrogenated palm oil) from Danisco In- gredients (M) Sdn. Bhd (Prai Industrial Estate, Penang, Malaysia), water (filtered municipal water supply), and vac- uum-dried salt. Chemical and physical analysis. SMP by PORIM Test Method (12) was carried out by first dipping three open-ended capillary tubes with internal diameters of 1.1–1.3 mm and ex- ternal diameters of 1.4–1.7 mm in a filtered liquid oil so that a Copyright © 2002 by AOCS Press 1163 JAOCS, Vol. 79, no. 12 (2002) *To whom correspondence should be addressed. E-mail: yaakub@fsb.upm.edu.my Effect of Emulsion Temperature on Physical Properties of Palm Oil-Based Margarine M.S. Miskandar a,b , Y.B. Che Man a, *, M.S.A. Yusoff b , and R. Abdul Rahman a a Department of Food Technology, Faculty of Food Science and Biotechnology, Universiti Putra Malaysia, 43400 UPM Serdang, Selangor D.E., Malaysia, and b Malaysian Palm Oil Board, 43000 Kajang, Selangor D.E., Malaysia