J. Parcerisa

Analysis of olive and hazelnut oil mixtures by high-performance liquid chromatography-atmospheric pressure chemical ionisation mass spectrometry of triacylglycerols and gas-liquid chromatography of non-saponifiable compounds (tocopherols and sterols).

We analysed the triacylglycerol, tocopherol and sterol composition of hazelnut oil, olive oil and their mixtures (90% olive oil with 10% hazelnut oil, 70% olive with 30% hazelnut oil and 50% olive oil with 50% hazelnut oil). The main triacylglycerols were 1,2,3-trioleylglycerol, 2,3-dioleyl-1-palmitoylglycerol, 2,3-dioleyl-1-linoleylglycerol and 2,3-dioleyl-1-stearoylglycerol. Non-saponfiable compounds (tocopherols and sterols) were derivatised as O-trimethylsilyl ethers. Alpha-tocopherol was the main vitamin E isomer in all samples; however, small amounts of beta-tocopherol and gamma-tocopherol were also found. Beta-sitosterol and delta5-avenasterol were the principal sterols in all samples; campesterol and stigmasterol were minor sterol compounds in all samples. Obtusifoliol, which was a major sterol in olive oil and oil mixtures, was not found in hazelnut oil. The discriminant analysis showed that hazelnut oil, olive oil and oil mixtures were clearly separated according to their triacylglycerol composition.

Fatty acid, tocopherol and sterol content of some hazelnut varieties (Corylus avellana L.) harvested in Oregon (USA)

Abstract We analysed the fatty acid, tocopherol and sterol composition of several hazelnut varieties of different geographical origins harvested in Oregon. Monounsaturated and polyunsaturated fatty acids were the most predominant fatty acids in hazelnut oil extracted from samples. A one-way analysis of variance revealed significant differences for fatty acid content between varieties. Discriminant analysis using individual fatty acids as variables revealed that hazelnut samples were grouped according to their origin. α-Tocopherol, campesterol, stigmasterol, β-sitosterol and Δ 5 -avenasterol were predominant in the unsaponifiable lipid fraction of hazelnut samples. A Kruskall Wallis nonparametric test revealed significant differences between hazelnut varieties for α-tocopherol and sterol content. However, no significant differences were found in relation to geographical origin.

Influence of variety and geographical origin on the lipid fraction of hazelnuts (Corylus avellana L.) from Spain: (III) oil stability, tocopherol content and some mineral contents (Mn, Fe, Cu)

Abstract Induction time, acid value and α-tocopherol content of hazelnut oil and some mineral contents (manganese, iron and copper) of hazelnut kernels cultivated in Catalonia (Spain) are determined. Analysis of variance (ANOVA) showed that statistically significant differences existed for: α-tocopherol content, acid value and copper content in relation to the harvesting year of samples. Significant differences were also found for: induction time, manganese and copper contents in relation to the location of samples. On the other hand, no significant differences were found between varieties. In addition, a correlation study was performed between all parameters included in this work. A strong negative correlation was observed between linoleic acid and manganese content, and also copper content and oil stability (Rancimat).

INFLUENCE OF DRYING CONDITIONS ON THE HAZELNUT QUALITY. I. LIPID OXIDATION

ABSTRACT The influence of the drying conditions on the oxidation state of the lipidic fraction in hazelnut (Corylus avellana, L.) has been studied. Different hazelnut quality parameters (acidity index, KZI2 index, K270 index and oxidation stability) have been determined in unshelled and shelled hazelnuts dried under six drying air temperatures (30, 40, 50, 60, 70 and 80°). The drying experiments were done with forced air circulation, and two varieties of hazelnut were investigated, Negret and Pauetet. It has been observed that hydrolytic reactions affect dried Negret hazelnut, increasing with drying temperature. Also, drying temperatures higher than 50°C favour an increase of the rate of lipid oxidation in hazelnut, specially in shelled hazelnuts, with a decrease of the oxidation stability.

INFLUENCE OF DRYING CONDITIONS ON THE HAZELNUT QUALITY : II. ENZYMATIC ACTIVITY

ABSTRACT The influence of the drying conditions on the enzymatic activity in hazelnut (Corylus avellana, L.) has been studied. In this work, the activity of the enzymes lipase. peroxidase and polyphenoloxidase have been determined in hazelnuts dried under three temperatures (30, 50 and 70°C). The drying experiments were done with forced air circulation, and samples of Negret variety. unshelled and shelled, were used. It has been observed that the drying process reduces the activity of the enzymes lipase, peroxidase and polyphenoloxidase in hazelnut, and the results indicated that polyphenoloxidase is the most unstable to heat.