The main advantages of NMR are high precision, short analytical time, and easy sample preparation (Sacchi et al. A typical 1H NMR spectrum of an olive oil sample discriminates only classes of fatty acyls with 0, 1, 2 or 3 double bonds (Sacchi et al. One spectroscopic technique employed in olive oil analysis is high-resolution NMR (Alonso-Salces et al. Among various methods, spectroscopy has recently emerged as an important tool. For this reason, in order to contribute to the efforts of authentication studies, there is a need for analyzing olive oil samples from different countries such as Turkey.ĭue to such international requirements, there are several analytical protocols developed for the analysis of olive oil. However, there is still necessity for determining shelf life of olive oil due to its not only economic importance but also significance for human health.Ī significant act of legislation, the Protected Designation of Origin (PDO) allows the identification of some Mediterranean extra virgin olive oils with the names of their origins (Council Regulation 1992). Most olive oil producers and researchers consider 1–1.5 years as the maximum commercial storage period from bottling to consumption, depending on the varietal composition of the olive oil (Krichene et al. Because fats and oils decompose into different oxidation by-products over time, there is an increasing interest in determining shelf life of olive oil and studying the occurrence of the chemical process of the oxidation into by-products. Shelf life is considered as the finite length of time after food production and packaging needed to reach this acceptability level under well-defined storage conditions (Nicoli 2012). The quality level of food samples is directly related to acceptability limit, and upon reaching this limit the product defined as unsuitable for consumption due to different factors such as nutritional or sensory criticisms. One of the other important aspects of olive oil is its shelf life determination. Therefore, there are regulations that define olive oil genuineness and quality grade (Sacchi et al. The consumption of olive oil increases in the daily human diet due to its positive health effects (Manai-Djebali et al. The chemical composition of olive oil may change due to climate, genetics of the olive tree, agronomic factors, and the practice of farmers (Gurdeniz et al. Olive oil contains more than 98% triglycerides responsible for its nutritional and physico-chemical properties and 1–2% of minors such as sterols, squalene, and α-tocopherol, the unsaponifiable fraction (Alonso-Salces et al. Olive oil is a genuine fruit juice with excellent nutritional, sensory and functional quality obtained from the fruit of Olea europea L. The effects of altitude and soil quality on fatty acyl contents of olive oil samples from a small olive growing village in Northeastern Turkey were also tested. 1H NMR spectra of three olive oil samples with the production years of January 2013, January 2014, and January 2015 were acquired in 2016 for discussing shelf life of olive oil by quantifying fatty acyls content, and determining minor constituents and possible by-products during storage. Comparing the linoleoyl and oleoyl acyl contents of Turkish olive oils with these of some Mediterranean olive oils showed the possibility of distinguishing the Turkish olive oils. Applying both quantitative NMR and statistical analysis indicated that samples from different provinces within each geographical region (MR, AR, and MeR) could be discriminated. The best discriminative parameter was the 1H NMR signal of linoleoyl acyl content. ![]() ANOVA was employed for samples from three regions separately: Marmara Region (MR), Aegean Region (AR), and Mediterranean Region (MeR). The combination of discriminative screening by 1H NMR and ANOVA did not require further analysis of olive oil such as gas chromatography (GC). The 1H NMR data were subjected to principal component analysis (PCA) and analysis of variance (ANOVA) to discriminate the origin of olive oils. High-field proton ( 1H) nuclear magnetic resonance (NMR) spectroscopy was applied for screening the fatty acyl contents of 33 olive oil samples from five different geographical regions of Turkey to do geographical discrimination analysis.
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