In this study, the levels of boron (B), cobalt (Co), copper (Cu), chromium (Cr), iron (Fe), lithium (Li), nickel (Ni), selenium (Se) and zinc (Zn) microelements in 16 hazelnut samples were determined by inductively coupled plasma mass spectrometry and atomic absorption spectroscopy after microwave digestion, and are discussed for human nutrition and health. Significant differences were observed between the microelement contents of the 16 varieties (P < 0.01). The average microelements concentrations in the varieties varied in the following ranges: B, 13.63-23.87; Co, 0.47-0.82; Cr, 0.22-0.52; Cu, 16.23-32.23; Fe, 31.60-51.60; Li, 0.035-0.042; Ni, 0.58-2.58; Se, 0.96-1.39; and Zn, 22.03-44.03 mg/kg. These results showed that hazelnuts can be an important microelement source for human nutrition and health. According to our trace element data, a daily consumption of 50 g hazelnut can supply easily about 6% for B, 9% for Co, 19% for Fe, 9% for Ni and 16% for Zn of the recommended daily allowance. On the other hand, Se, Cu and Cr levels of 50 g hazelnuts are higher than the respective daily requirements, but slight overdoses of these elements are non-toxic for human health.

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As part of a large-scale programme to investigate the health effects of exposure to borate minerals in Turkey, boron concentrations in vegetables, fruits and some other foods were determined. From all borate-producing regions of the country, 22 species of fruit, 17 species of vegetable, 12 species of cereal, legume and oilseed, three species of herbs and six types of other food were collected in 1999 and analysed for boron concentrations using the Azomethine H method. The results were compared with 37 types of food collected from areas well distant from the borate-producing areas. The total number of samples evaluated was 420. Pistachio (67.0 mg kg −1 ) had the highest concentration of boron, followed by grape leaf (60.48 mg kg −1 ), sour cherry (57.03 mg kg −1 ), quince (38.78 mg kg −1 ), peach (34.49 mg kg −1 ), grape (20.70 mg kg −1 ), green beans (19.49 mg kg −1 ), unripe peach (18.92 mg kg −1 ) and parsley (10.24 mg kg −1 ) from the borate-producing regions. A large number of foods contained boron at higher concentrations than those reported in the literature, most probably due to the high boron content of these Turkish soils. According to the results of t-tests, the area itself does not have a significant effect (p > 0.05) on boron concentration in all foods evaluated so far.

The phytosterol contents of the oils from 17 Turkish hazelnut cultivars were determined by gas chromatography with a flame ionization detector. The total phytosterol content varied from 1180.4 (UzunmusaOrdu) to 2239.4 mg/kg (Cavcava), and the average was 1581.6 6 265.1 mg/kg. One of the most significant commercial cultivars, Tombul, contained quite low total phytosterols (1297.7 mg/kg). Total and individual phytosterol contents of hazelnut cultivars were significantly different at p ,0.01, except for phytostanol and campestanol. The main component was b-sitosterol which ranged from 82.8 to 86.7% in all cultivars. This was followed by campesterol, D 5-avenasterol, sitostanol and stigmasterol. Interestingly, the same cultivars from different regions showed similar total phytosterol contents, and fall almost within the same range according to Duncan's test, which may indicate that the phytosterol content is highly related to the cultivar.

In this study, the effect of chlorogenic acid obtained as an antioxidant from Green Coffee Extract ( GCE ) on the shelf life of Hazelnut Paste ( HP ) was investigated at 4, 25, and 40 °C for 3 months. The analysis of variance showed that the effect of AR (Additive Ratio) × T (Temperature) × t (Storage Time) interaction on Peroxide Number ( PV ), tocopherols, and phenolics ( TPC ) of GCE-HP mixtures was found to be significant ( P < 0.05 ). ARxt factor on Hunter L*, a*, and b* color values, DPPH -radical scavenging activity and antioxidant activity ( AA ), Txt factor on oleic/linoleic acid ratio ( O/L ), and ARxT and ARxt interactions on free fatty acid were more effective ( P < 0.05 ). Regression equations of O/L , PV , AA , and TPC can be used to calculate the shelf life of HP due to high R 2 values (87.14–94.46%). In addition, according to the O/L regression equation, the shelf life of the HP control samples was 28 days at 22 °C, increased to 60 days at 0.5%- GCE and 90 days at 25.68 °C at 0.75%- GCE ( R 2 = 87.14%, P < 0.001 ). GCE (0.5–0.75%) was a promising antioxidant in increasing the shelf life of HP.