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Hazelnut (Corylus avellana L.) samples were collected from six different cultivars of trees grown in an experimental orchard at Lincoln University. 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 oil, stability to oxidation of the oil, and fatty acid, tocopherol, and sterol composition were determined on samples of freshly extracted hazelnut 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 ranged from 15.6 to 25.3 h. The content of the monounsaturated oleic acid in the oils ranged from 73.8 to 80.1% of the total fatty acids, while the tocopherol content ranged from 225.8 to 552.0 mg/g freshly extracted oil. The major desmethylsterols were sitosterol, ranging from 1416 to 1693 µg/g, campesterol, ranging from 78 to 114 µg/g, and ∆5-avenasterol, ranging from 110 to 170 µg/g. The oil extracted from 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 γ-tocopherol when compared to the other cultivars. The higher levels 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 other nuts tested. JAOCS 74, 755-759 (1997).

Walnuts (Juglans regia L.) were collected during the 1997 harvest from 13 different cultivars of trees grown in a replicated trial in an experimental orchard at Lincoln University. Two U.S. commercial cultivars (Tehama and Vina), three European commercial cultivars (Esterhazy, G139, G120), and eight New Zealand selections (Rex, Dublin's Glory, Meyric, Stanley, Mckinster, 150, 151, 153) were evaluated. Total lipids were analyzed for fatty acids by capillary gas chromatography, tocopherols by high-performance liquid chromatography, and oxidation stability by Rancimat. The total oil content of the nuts ranged from 64.2 to 68.9% while the stability of the oil ranged from 3.9 to 7.8 h. The oleic acid content of the oils ranged from 12.7 to 20.4% of the total fatty acids, while 18:2 content ranged from 57.0 to 62.5% and the 18:3 contents ranged from 10.7 to 16.2%. Reduced stability of the oil as measured by the Rancimat method appears to be correlated to higher levels of 18:2 in the extracted oil. The total tocopherol contents of these nuts ranged from 268.5 to 436.0 µg/g oil. γ-Tocopherol dominated the profile while α-tocopherol was only 6% of the total content. Peroxide values of the fresh oil were measured spectrophotometrically to give an indication of the overall stability. The levels of total tocopherols when combined with the level of unsaturation in the oil in a multiple regression analysis had a significant relationship (R 2 = 45.2%, P < 0.001) with the peroxide value in the oil. a Means of duplicate analyses. Trace amounts of 14:0, 16:1, 20:0, and 22:0 were present in all cultivars; these fatty acids made up <0.2% of the total fatty acids. P < * = 0.05, *** = 0.001. Rancimat value a = 36.6 − 0.0377 [18:2] − 23.3 [20:1] − 8.04 [18.1 ∆11 ] c Peroxide value b = 8.49 − 0.0202 × [total tocopherol] + 21.7 [20:1]a Hours. b meq oxygen/kg fat. c Fatty acids as g/100 g oil, tocopherol as µg/g oil. P < * = 0.05, ** = 0.01, *** = 0.001. SS = sums of squares for regression component.

No abstract

Plant sterols are known to have serum cholesterol lowering effects. A high dietary intake might therefore have a positive impact on health. All food items of vegetable origin contain some amount of plant sterols. The aim of this study was to analyse the plant sterol content of vegetables and fruits commonly consumed in Sweden, and to compare fresh and cooked samples of the same items. Altogether 20 different vegetables and 14 fruits were analysed. All vegetables and fruits were purchased in two shops in the city of Gothenburg, Sweden. Lyophilization was performed within one month of the items being purchased. The samples were frozen at -20 (C and analysed within six months, with a GLC method after acid hydrolysis, alkaline hydrolysis and silylation with tri-methylsilylether. The acid hydrolysis was done in order to detect the fraction of glycosylated plant sterols, which are split during boiling with HCl. The median plant sterol content of vegetables was 14 (3.8-50) mg/100 g edible portion. The highest concentrations were found in broccoli. Brussels sprouts, cauliflower and olives. The median plant sterol content of fruits was 16 (3-44) mg/100 g edible portion. The highest concentrations were found in oranges and passion fruits. The plant sterol concentrations were thus low in vegetables and fruits commonly consumed in Sweden. A serum cholesterol lowering effect attributed to the plant sterols in vegetables and fruits would therefore be of limited significance.