Sedimentation field-flow fractionation: Size characterization of food materials Sudarat Saeseaw, Juwadee Shiowatana, Atitaya Siripinyanond * Department of Chemistry, Mahidol University, Rama VI Rd., Bangkok 10400, Thailand Received 3 December 2004; accepted 6 April 2005 Abstract Sedimentation field-flow fractionation (SdFFF) was applied to characterize particle size distributions of food materials. Two types of food particles were examined, including milk suspensions and flour samples. Milk eluted in the normal mode SdFFF, whereas the steric mode of retention was used for flour samples. Various types of milk being investigated were from cereal and cowÕs origins. The cereal milk samples included corn, jobÕs tear, rice, and soy milk, whereas the bovine milk included chocolate and fresh full-fat milk. Most samples exhibited monomodal size distributions, whereas corn milk displayed a slight deviation from monomo- dal characteristic. The mean particle sizes were detected to be approximately 0.4 lm for all cereal milk, except that they were approximately 0.5 lm for corn and all bovine milk. The application of SdFFF for micrometer size food particles was demonstrated for four types of flour samples, including corn, mung bean, rice, and tapioca flours. Significantly differences in the particle size char- acteristics of all flour samples were observed, by which corn, mung bean, rice, and tapioca yielded mean particle sizes of 16.7, 31.5, 13.5, and 19.9 lm, respectively. The ability of SdFFF for size separation of flours was confirmed by comparing the results obtained with those from scanning electron microscopy (SEM). Further, a new way to examine flour swelling was proposed. This study has demonstrated the potential value of SdFFF technique for food scientists. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Sedimentation field-flow fractionation; Size distribution; Milk; Flour 1. Introduction Nowadays, cereal foods have gained popularity worldwide, owing to the increased health awareness of human (Durand, Franks, & Hosken, 2003). Therefore, research and development in food technology to im- prove the taste and quality of food products containing cereal is of central concern among food scientists. One of the important parameters affecting the quality and taste of final food products is the particle size of raw materials used. Thus, the detailed information about particle size and its impact on food texture and taste is important for the design of food processing and for the quality control of food. Various size characterization techniques for food materials have been reported, including sieving, optical microscopy, photon correlation spectroscopy (Regnault, Thiebaud, Dumay, & Cheftel, 2004), dynamic light scat- tering (Durand et al., 2003), and field-flow fractionation (FFF) techniques (Arfvidsson, Wahlund, & Eliasson, 2004; Contado, Riello, Blo, & Dondi, 1999; Caldwell, Li, Li, & Dalgleish, 1992; You, Stevenson, Izydorczyk, & Preston, 2002). In this study, FFF was employed 0963-9969/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.foodres.2005.04.001 Abbreviations: FFF, field-flow fractionation; SdFFF, sedimenta- tion field-flow fractionation; Sd/StFFF, sedimentation/steric field-flow fractionation; SEM, scanning electron micrograph; d, diameter; rpm, revolution per minute; s.d., standard deviation. * Corresponding author. Tel.: +66 2201 5129; fax: +66 2354 7151. E-mail address: scasp@mucc.mahidol.ac.th (A. Siripinyanond). www.elsevier.com/locate/foodres Food Research International 38 (2005) 777–786