Physico-chemical characteristics and oxidative stability of walnut (Juglans regia L.): Oil from cultivar Geisenheim-139

Abstract

The aim of this work was isolation and determination of oil from the cultivar Geisenheim-139. Two techniques of oil extraction were implemented: cold pressing and organic solvent extraction. Composition of walnut kernels was determined and also the basic physico-chemical parameters of walnut oil. The oil content was 71.23%. The fatty acid composition was identified by gas chromatography and the main components were as follows: linoleic acid 58%, oleic acid 18,6% and linolenic acid 13,1% for sample obtained by cold pressing and 57,3%, 19,8%, 13,6% for sample obtained by solvent extraction. Total tocopherol content was analyzed by HPLC and ranged from 37,6 mg% for oil sample obtained by cold pressing and 42,40% for solvent extracted sample. Predominant tocopherol was γ-tocopherol. The content of sterols was determined from the unsaponifi able fraction. The dominant sterols were beta-sitosterol i Δ-5 avenasterol. Oxidative stability of samples was measured by Rancimat method. Oil sample obtained by organic solvent extraction had better oxidative stability (5,8h) than the sample obtained by cold pressing (5,0h).

Izolovano je ulje iz jezgra oraha sorte Gajzenhajm-139 primenom dve tehnike: hladno ceđenje i ekstrakcija organskim rastvaračem. Određeni su sastav i fizičko-hemijske karakteristike jezgra oraha i izdvojenog ulja. Sadržaj ulja je iznosio 71,23%. Sastav i sadržaj masnih kiselina je određen metodom gasne hromatografije. Dominantne masne kiseline su: linolna sa sadržajem od 58,0%, zatim oleinska 18,6% i linolenska 13,1% u ulju dobijenom hladnim ceđenjem odnosno 57,2%, 19,8%, 13,6% u ulju dobijenom ekstrakcijom organskim rastvaračem. Ukupan sadržaj tokoferola određen je HPLC metodom i iznosi 37,6 mg % u ulju dobijenom hladnim ceđenjem i 42,40 mg% u ulju dobijenom ekstrakcijom organskim rastvaračem. Dominantni tokoferol je bio γ-tokoferol. Određen je i sadržaj sterola iz frakcije neosapunjivih materija. Dominantni steroli su bili beta-sitosterol i Δ-5 avenasterol. Oksidativna stabilnost uzoraka je određena Rancimat testom i iznosi 5,0 h za ulje dobijeno hladnim ceđenjem odnosno 5,8 h za ulje dobijeno ekstrakcijom organskim rastvaračem. .