Huri Ilyasoglu

Aflatoxin levels in raw and processed hazelnuts in Turkey

Aflatoxin levels in hazelnut samples obtained from exporter companies were monitored over a 3-year period. A total of 3188 samples of raw and processed hazelnuts were analysed using an HPLC method. The total aflatoxin content of the contaminated samples was in the range of 0.02–78.98 µg kg−1 for hazelnut kernels, 0.07–43.59 µg kg−1 for roasted hazelnut kernels, 0.02–39.17 µg kg−1 for roasted sliced hazelnut kernels, and 0.02–11.20 µg kg−1 for hazelnut purees, respectively, showing that the variations of aflatoxin contamination were very high. The results of aflatoxin analysis revealed that the aflatoxin contamination in the hazelnut samples was at a tolerable level. A total of 3147 samples were contaminated with aflatoxins, although below the legal limits. However, the aflatoxin contents of 41 samples exceeded the legal limits. Therefore, aflatoxin contents of hazelnuts should be monitored regularly to minimise the risk of aflatoxin hazard, and pre- and post-harvest strategies should be developed to prevent aflatoxin formation.

Characterization of Rosehip (Rosa canina L.) Seed and Seed Oil

In this study, the nutritional composition and phytochemical composition of the rosehip seed, and the fatty acid and sterol compositions of the seed oil were investigated. The rosehip seed contained valuable phytochemicals such as phenolic compounds (2554 μg/g), carotenoids (2.92 μg/g), and ascorbic acid (1798 μg/g). Furthermore, the rosehip-seed oil was rich in polyunsaturated fatty acids, linoleic acid (54.05%), linolenic acid (19.37%), and phytosterols, mainly β-sitosterol (82.1%). The rosehip seed and seed oil were found to have antioxidant activity measured by trolox equivalent antioxidant capacity assay. It can be concluded that the rosehip seed and seed oil may be utilized as a source of phytonutrients.

Effect of Domestic Cooking Methods on Antioxidant Capacity of Fresh and Frozen Kale

The aim of this study was to evaluate the changes in the antioxidant capacity of fresh and frozen kale during domestic cooking methods (e.g., boiling, microwaving, and steaming). The antioxidant activities of the samples were measured using three in vitro assays (1,1-diphenyl-2-picrylhydrazyl assay, 2, 2’-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid assay, and ferric reducing antioxidant power assay). The steaming treatment was found to be the best cooking method to retain antioxidant compounds, followed by the microwaving and boiling treatments. The frozen uncooked samples exhibited a higher antioxidant capacity than the fresh, uncooked samples, indicating that the freezing process could enhance the antioxidant capacity of the kale.

Changes in Sterol Composition of Hazelnut During Fruit Development

Hazelnut is a valuable source of fat-soluble bioactive components. Among the fat-soluble bioactive components, phytosterols have gained much interest due to their cholesterol reducing properties. This study presents the evaluation of changes in the sterol composition of Turkish hazelnut cultivars (Tombul, Palaz, and Sivri) during fruit development. Three major sterols (β-sitosterol, campesterol, and Δ5-avenasterol), and five minor sterols (clerosterol, brassicasterol, stigmasterol, Δ7-stigmastenol, and Δ7-avenasterol) were detected in all hazelnut cultivars during all stages. The total sterol contents of Turkish hazelnut cultivars reached the maximum values at the early stage and a significant reduction in the total sterol content occurred at the harvest stage.