Storage Hazelnuts: Effect on Aromatic Profile and Sensory Attributes (original) (raw)

The hazelnuts quality was studied during and after the storage in selected maintenance conditions. Hazelnuts of 'Tonda Gentile Romana' cultivar and Turkish provenance were stored with and without oxygen presence (air, vacuum with or without nitrogen saturation packaging) at two different temperatures (4-20°C). During storage, the quality was monitored by assessment of the peroxides value, acidity level, sensory analysis, total phenolic compounds content and hexanal content. It was observed that after nine months storage period, the trials without oxygen were in better condition to preserve the hazelnuts from oxidative decline. The best analytical parameter to identify the oxidative state of hazelnuts was the hexanal content conducted through the SPME/GC method, and the decrease in amount of polyphenolic compounds. INTRODUCTION A study was carried out on fresh and stored, raw and roasted hazelnuts ('Tonda Gentile Romana' and 'Turkish') during storage under different conditions (room temperature, 4°C and vacuum, with and without nitrogen saturation) mainly on the volatile compounds, chemical parameters and sensory characteristics for monitoring shelf-life and the oxidation state of hazelnuts. The hazelnuts, as with most other foods with high fat content, are susceptible to lipid enzymatic or non-enzymatic oxidation. The primary oxidation products from unsaturated fatty acids, are the hydroperoxides, highly reactive compounds, that decompose rapidly, yielding a complex mixture of non-volatile and volatile compounds such as hydrocarbons (ethane, pentane), aldehydes (pentanal, hexanal, hexenal, 2-octenal, 2-nonenal) and ketones, which affect the overall quality of the product. Aldehydes are particularly important in relation to flavour alteration and from a toxicological perspective (Frankel, 1980,1982,1993). Extended storage of raw and roasted hazelnuts increases the production of fat oxidation off-flavours. The major product of fat oxidation that increases in content during storage is hexanal, more researchers have proposed it as an indicator of fat oxidation rather than the traditional oxidation indicators which are acidity or peroxide values (P.V.). The main aim of our work was to identify for hazelnuts good shelf-life indicators of the oxidative condition of the products during storage. MATERIALS AND METHODS Samples of hazelnuts of two different provenences, Italy, Latium Viterbo area, var. 'Tonda Gentile Romana' (TGR) and Turkish, both raw (Natural N) and roasted (R) were used. The hazelnuts were stored at 4°C (r) or room temperature 20-22°C (a), in open air (a) or into multilayer bags under vacuum. More specifically, the specimens were packed into 10 kg-multilayer bags that were under-vacuum sealed (V) or alternatively into 1 mg-multilayer bags, that were previously flushed with nitrogen to remove all the air and finally under-vacuum sealed (NV). All specimens were scheduled to be stored for 9 months, from February-November 2007 and to be sampled after 2, 4, 7 and 9 months (Fig. 1). All samples were provided by Stelliferi & Itavex (Caprarola-VT).