Isolation and characterization of oil bodies from Oryza sativa bran and studies of their physical properties Nantaprapa Nantiyakul a , Samuel Furse b , Ian D. Fisk a , Gregory Tucker c , David A. Gray a, * a Division of Food Sciences, School of Biosciences, University of Nottingham, College Lane, Sutton Bonington, Leicestershire LE12 5RD, UK b School of Biosciences, University of Nottingham, College Lane, Sutton Bonington, Leicestershire LE12 5RD, UK c Nutritional Sciences, School of Biosciences, University of Nottingham, College Lane, Sutton Bonington, Leicestershire LE12 5RD, UK article info Article history: Received 25 July 2012 Received in revised form 30 October 2012 Accepted 7 November 2012 Keywords: Rice bran Oil bodies Oil production abstract In this paper, we demonstrate a novel and environmentally-conscious approach to the isolation of oil bodies (OBs) from the bran arising from the milling of Oryza sativa (Basmati rice). We have used several physical techniques to determine the effect of the steps of the process on the OBs, and describe an isolation process that is scalable to an industrial level. The physical techniques [microscopy, particle size determination (diameter 1.9e5.8 mm), z-potential (40 mV at pH 8.0, 0 mV at pH 4.0,17 mV at pH 2.0), and relative turbidity measurements (pH 3.0e5.0 unstable, pH 6.0e8.0 stable)] and chemical analyses (lipid 83.7%, protein 11.5% dry basis) also give us an insight into the physical properties of OBs in general. This understanding has implications for the use of OBs in food manufacturing, and on the isolation of OBs from a variety of cereal crops. Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. 1. Introduction Oil bodies (OBs) are energy-storage organelles used by plants to facilitate germination and radicle growth (Huang, 1996; Murphy, 2001). OBs are therefore particularly important in oleaginous seeds, in which they can form as much as 40% of the mass of the cotyledon (Murphy, 2001). The use of these organelles in food manufacturing, as well as their biological function is therefore of high importance in the understanding and handling of oleaginous seeds. OBs are generally 0.5e2.5 mm in diameter and composed of a mass of triglycerides surrounded by a mono-layer composed of lipids and proteins (Huang, 1996). The proteins are particular to OBs and are of three types known to date, namely oleosins (15e25 kDa), with caleosins (27 kDa) and steroleosins (39 kDa) (Chen et al., 1998; Lin et al., 2002; Qu et al., 1986; Tzen et al., 1993). The mono-layer forms a defining barrier between the triglycerides and the cytosol. Evidence also suggests that this mono-layer is adapted to stabilize the oil bodies through being negatively charged at physiological pH (Tzen et al., 1992). This charge is reported to be an important factor in suppressing the aggregation and coalescence of OBs observed at lower pH (Tzen and Huang, 1992) and thus maintains the organelles’ structural integrity. Despite this work, little is known about the physical properties of OBs. OBs can be isolated from a number of sources, but there is little data available on the OBs from the bran of Oryza sativa (Nantiyakul et al., 2012). Rice bran is a by-product from milling and is a rich source of fatty acids (15e20 % oil depending on variety of rice and type of milling) (McCaskill and Zhang, 1999) as well as lipo- philic bioactive compounds including tocotrienols, tocopherols and g-oryzanol (Nantiyakul et al., 2012). Current commercial practice for the extraction of fats from rice bran involves using a volatile organic solvent such as hexane followed by refining the crude oil (Nicolosi et al., 1994). Although this conventional extraction is efficient with respect to isolating the fatty acid content of the starting material, and cheap, the use of a toxic, carbon-based and inflammable organic solvent results in envi- ronmental damage. However, the extraction of OBs using aqueous media has been known for some time (Murphy and Cummins, 1989). Isolation of OBs using aqueous extraction has obvious environmental benefits not afforded to the industrial use of an organic solvent. Additionally, employing an aqueous medium ensures that the OB isolate is in the form of an emulsion that is a physically and chemically stable on a food manufacturing time scale (Fisk et al., 2011 , 2008; Gray et al., 2010). No work has yet been done on the chemical and physical robustness of rice bran OBs and thus how maximum yield from the rice bran may be Abbreviations: OB, oil body. * Corresponding author. Tel.: þ44 1159 516147; fax: þ44 1159 516142. E-mail addresses: samuel@samuelfurse.com, samuel.furse@nottingham.ac.uk (S. Furse), David.Gray@nottingham.ac.uk (D.A. Gray). Contents lists available at SciVerse ScienceDirect Journal of Cereal Science journal homepage: www.elsevier.com/locate/jcs 0733-5210/$ e see front matter Crown Copyright Ó 2012 Published by Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.jcs.2012.11.002 Journal of Cereal Science 57 (2013) 141e145