ABSTRACT: Physicochemical and instrumental characteriza- tion of rubber (Hevea brasiliensis Müll. Arg.) seed oil (RSO) was carried out for the purposes of quality assessment, identification, and authentication. Properties such as color (Lovibond), specific gravity, percent FFA (as oleic acid), acid value, saponification value, iodine value, and viscosity were determined. FA composi- tion and M.W. averages of RSO were determined using GLC and gel permeation chromatography (GPC), respectively. Structural features of RSO were also determined using FTIR, 1 H NMR, and 13 C NMR spectroscopy. The natural form of RSO is highly acidic (acid value ≈ 43.6 mg KOH/g). The saturated FA are palmitic (17.50%) and stearic (4.82%), and the main unsaturated FA are oleic (25.33%), linoleic (37.50%), and linolenic (14.21%). The oil can be classified as semidrying. GPC shows an unusual peak that is due to a very high M.W. (≈38,800) fraction that is not found in the chromatogram of known vegetable oils and is therefore unique to RSO. FTIR, 1 H NMR, and 13 C NMR analyses confirmed that RSO is composed mainly of TAG of saturated and unsatu- rated FA. Functional groups such as carbonyl, olefinic unsatura- tion, esters, glyceryl, methylene, and terminal methyl that are pre- sent in vegetable oils are also present in RSO. Paper no. J10960 in JAOCS 82, 465–469 (July 2005). KEY WORDS: Molecular weight averages, physicochemical properties, quality authentication, rubber seed oil, spectrometry. Vegetable oils are used not only for edible purposes but also for nonedible applications such as drying oils in paints. They are increasingly being used in the production of renewable in- dustrial resources such as long-chain FA and oleochemicals for the chemical industry, hydroxyl acids, epoxy FA, conjugated unsaturated FA, plasticizers, surfactants, and adhesives (1–4). Positive industry trends indicate the continued development, use, and expansion of vegetable oils in fields such as environ- mentally friendly water-reducible alkyd resins. With the devel- opment of these new applications, determination of the quality of vegetable oils that is required in a particular field has become an important subject from both commercial/industrial and ana- lytical perspectives. For instance, owing to price differentials between vegetable oils, a less expensive oil could be used to adulterate the more expensive one to the detriment of quality. A case in point was the adulteration of olive oil with rapeseed oil, the consumption of which led to the death of many persons (5). Characterization of vegetable oils and consequently their authentication help to control adulteration. Characterization also constitutes an integral part of determining their end uses, because the properties of the raw oil determine the quality of the derivable products (6). For example, the rate of drying of oil-modified alkyds is related not only to the level of unsatura- tion but also to the types and amounts of PUFA present in the oil. Most current work on vegetable oil quality assessment is based on a number of instrumental techniques such as gel per- meation chromatography (GPC), FTIR, MS, NMR, and HPLC (7–11). The technical literature is replete with information on the characteristics and authentication of vegetable oils with useful industrial applications (12–14). This study concerns the characterization of rubber seed oil (RSO), which is assuming prominence as a binder in surface coatings and as a plasticizer/stabilizer for PVC and natural rub- ber (15–19). Characterization and determination of the quality features that would distinguish RSO from other vegetable oils were carried out using GPC, GLC, and FTIR and NMR spec- troscopy as well as chemical analyses. The goals were to give better insight into the characteristic features of RSO in relation to its end uses and to establish a basis for studies of more com- plex products, e.g., alkyds, that are derivable. EXPERIMENTAL PROCEDURES Materials. Rubber seeds were collected from the estate of the Rubber Research Institute of Nigeria (RRIN). The 40-ha estate is planted with RRIN-developed high-latex-yielding clones (NIGERIA 800 series) that are about 17 yr old. The seeds were further dried, to a moisture content of about 7%, and their oil was extracted in the pilot mill of the institute. The yield was 23%. Potassium hydroxide, hydrochloric acid, potassium iodide, potassium iodate, sodium thiosulfate, iodine trichloride, and other reagents used in the chemical characterization of RSO were all of analytical grade and were obtained from British Drug House (BDH), Poole, England. Analysis of RSO. The physicochemical properties of RSO such as color, specific gravity, acid value, saponification value, iodine value, and viscosity were determined according to IUPAC standard methods (20). GLC. The FA composition of RSO was determined using its methyl esters on a Hewlett-Packard 5890 Series II gas chro- matograph with FID (Avondale, PA). The injection and detec- tion temperatures were 250 and 300°C, respectively. Nitrogen was used as the carrier gas at a flow rate of 20 mL/min. GPC. M.W. averages of RSO were determined using GPC, performed on a Hewlett-Packard 1081 B high-performance liq- uid chromatograph with refractive index detector consisting of Copyright © 2005 by AOCS Press 465 JAOCS, Vol. 82, no. 7 (2005) *To whom correspondence should be addressed at End-Use Division, Rub- ber Research Institute, of Nigeria, P.M.B. 1049, Benin City, Nigeria. E-mail: aigbodionai@yahoo.com Rubber Seed Oil Quality Assessment and Authentication A.I. Aigbodion* and I.O. Bakare End-Use Division, Rubber Research Institute of Nigeria, Benin City, Nigeria