© WILEY-VCH Verlag GmbH, 69451 Weinheim, 2002 0038-9056/2002/0505-0193 $17.50+.50/0 Starch/Stärke 54 (2002) 193–197 193 Research Paper 1 Introduction Okenia hypogaea (Schlech. & Cham.) belongs to the fam- ily of the Nyctaginacea, the plant probable originates from Mexico. It is a perennial herbaceous plant distributed throughout the Mexican Republic, as well as in great parts of the Pacific and the Atlantic coast of the United States and in Central America [1]. Okenia can be found in inund- able sandy soils as well as in soils of volcanic origin with poor content of organic matters and nitrogen, located from sea level up to 1110 m in altitude. The plant is able to grow wildly in humid, warm, semi-warm and subhumid tropical climates. O. hypogaea grows during the whole year as an abundant grass, close to the floor, with long branches and perfect flowers of live color. In Mexico, it is known by the common names of “cachás”, “cuachás”, “wild peanut” or “fox peanut” depending on the region where it is located [2]. This plant produces a seed that is composed mainly of starch. Some previous studies have been focused on the chemical composition of this seed [3]. However, there are not reports dealing with the phys- ical properties of okenia starch. The aim of this work was to isolate the starch from Okenia hypogaea and to evaluate its chemical composition, along with some physicochemical and functional proper- ties. 2 Materials and Methods 2.1 Starch isolation Mature seeds of O. hypogaea were harvested at a local experimental farm, the seeds were washed with distilled water to eliminate dust and other adhering substances and then cleaned and stored at 4 °C in sealed containers until use. Okenia starch was isolated using the method suggested by Adkins and Greenwood [4]. The seeds were soaked in a buffer solution of 0.02 M (pH 6.5) sodi- um acetate, containing 0.01 M mercury chloride. The ratio soaking solution to seeds was 2:1 (v/w). The mixture was kept at 5 °C, with agitation (50 rpm) in an orbital shaker for 24 h, changing the solution every 12 h. The solution was drained off and the softened seeds were washed thoroughly with distilled water. Afterwards, the crushed seeds were successively sifted through meshes no. 20, 40, 100, 200 and 320. In each mesh the residue was washed with distilled water until a mass of golden color was obtained without apparent leak out of residuals of starch. The starchy suspension obtained was centrifuged (6573 × g 5 °C, 30 min) and the supernatant was discard- ed. The precipitate consisted of two layers: an upper layer of slimy aspect and brown color, and a lower layer of white color (starch). The white starch precipitate was re- suspended in a solution of 0.1 M aqueous NaCl in toluene Laura Sánchez- Hernández a , Javier Solorza-Feria a , Guadalupe Méndez- Montealvo a , Octavio Paredes-López b , Luis Arturo Bello-Pérez a a Centro de Desarrollo de Productos Bióticos del IPN, Yautepec, Morelos, México b Centro de Investigación y de Estudios Avanzados del IPN, Irapuato Guanajuato, México Isolation and Partial Characterization of Okenia (Okenia hypogaea) Starch Okenia hypogaea (Schlech. & Cham.) belongs to the family of the Nyctaginacea, which produces a seed that is composed mainly of starch, the probable origin of Okenia hy- pogaea is Mexico. The aim of this work was to isolate the starch from Okenia hy- pogaea and to evaluate its chemical composition, along with some physicochemical and functional properties. Okenia gave a starch yield of 36 %; this starch had an amy- lose content of 26.1 %, with a fat content similar to corn starch, but with a higher ash fraction. Okenia starch possessed a small granule size (1–3 μm), the same as ama- ranth starch, with similar characteristics of stability and clarity of pastes as corn starch. At 60 °C the water retention capacity of okenia starch was higher than that of corn starch, but at higher temperatures an inverse pattern was found. When the temper- ature in the experiments increased, solubility and swelling values increased; okenia starch had higher swelling values than corn starch over the range of temperatures as- sayed. Okenia starch also presented a lower freeze-thaw stability than corn starch on the first two cycles. Overall, it was concluded that due to its physicochemical and func- tional properties, it is worthwhile to test the use of okenia starch in the cosmetic and food industry. Keywords: Starch; Okenia; Functional properties; Physicochemical properties Correspondence: Luis Arturo Bello-Pérez, Ceprobi-IPN (Center for Research on Biotic Products). Km 8.5 Carr. Yautepec-Jojutla, P.O. Box. 24, Z.C. 62731, Yautepec, Morelos, Mexico. e-mail: abello@hotmail.com.