LIPID-COMPOSITION AND OXIDATIVE STABILITY OF OILS IN HAZELNUTS (CORYLUS-AVELLANA L) GROWN IN NEW-ZEALAND

Hazelnut (Corylus avellana L.) samples were collected from six differe nt cultivars of trees grown in an experimental orchard at Lincoln Univ ersity. Three U.S. commercial cultivars (Butler, Ennis, and Barcelona) , two European commercial cultivars (Tonda di Giffoni and Campanica), and one New Zealand selection (Whiteheart) were evaluated. The total o il, stability to oxidation of the oil, and fatty acid, tocopherol, and sterol composition were determined on samples of freshly extracted ha zelnut oil. The total oil content of the seeds ranged from 54.6 to 63. 2% while the stability of the oil, as measured by the Rancimat test ra nged from 15.6 to 25.3 h. The content bf the monounsaturated oleic aci d in the oils ranged from 73.8 to 80.1% of the total fatty acids, whil e the tocopherol content ranged from 225.8 to 552.0 mg/g freshly extra cted oil. The major desmethylsterols were sitosterol, ranging from 141 6 to 1693 mu g/g, campesterol, ranging from 78 to 114 mu g/g, and Delt a 5-avenasterol, ranging from 110 to 170 mu g/g. The oil extracted fro m the cultivar Whiteheart was more stable (measured by Rancimat) than the oil from all other cultivars grown at the same location and under the same conditions. Whiteheart contained higher levels of total and g amma-tocopherol when compared to the other cultivars. The higher level s of tocopherol in Whiteheart help to explain the greater stability of the oil during the oxidative stress test. These results suggest that nuts from the cultivar Whiteheart could be stored longer than the othe r nuts tested.