Influence of Harvest Method and Period on Olive Oil Composition: an NMR and Statistical Study

Abstract

The influence of harvest period and harvest method on olive oil composition was investigated by nuclear magnetic resonance (NMR) spectroscopy and by some quality parameters such as free acidity, peroxide value, and UV spectrophotometric indices. This work focuses on two secondary factors (harvest period and harvest method) and investigated their interactions with primary (genetic and pedoclimatic) and secondary (agronomic practices and technological procedures) factors. To avoid misinterpretation, the general linear model analysis (GLM) was used to adjust the result obtained from the analysis of variance (ANOVA). In this way, the effect of the factor of interest was corrected for the effects of the other factors that might influence the variable under investigation. The weight of each factor was evaluated by the variance component analysis (VCA). Finally, multivariate statistical analyses, namely, principal component analysis (PCA) and linear discriminant analysis (LDA), were applied. Samples were grouped according to the harvest period and harvest method. Volatile compounds, that is, hexanal and trans-2-hexenal, as well as the sn-1,3-diglycerides and squalene, significantly decreased during the ripening. The relative value of the ΔK parameter and the hexanal amount were higher in the olive oils obtained from olives harvested by one type of hand-held machine (shaker), whereas the unsaturated fatty chains in the olive oils were higher when another type (comb) was used.

High resolution NMR characterization of olive oils in terms of quality, authenticity and geographical origin

“…One of the best-known conventional analyses is the measure of the free acidity, which is obtained with traditional chemical [57] b-sitosterol, squalene, linolenic acid, linoleic acid, saturated fatty acids 1 H, 600 Adulteration with hazelnut oil [67] Terpenes, aldehydes, sn-1,3 diacylglycerol, sn-1,2 diacylglycerol, squalene, unsaturated fatty chains, saturated fatty chains, wax, b-sitosterol 1 H, 600 Geographical origin (Mediterranean scale) [58] Terpenes, aldehydes, sn-1,3 diacylglycerol, sn-1,2 diacylglycerol, squalene, unsaturated fatty chains, saturated fatty chains, wax, b-sitosterol 1 H, 600 Harvest method [81] Metabolic fingerprinting 1 H, 500 Geographical origin (national and regional scale), harvesting [38] 1 H, 500 Geographical origin (Mediterranean scale) [37] 1 H, 600 Geographical origin (national scale) [39] Metabolic fingerprinting + metabolic profiling alcohols, sterols, hydrocarbons, tocopherol fractions 1 H, 500 Geographical origin (Mediterranean areas) [59] 1 H, 300 diffusion Adulteration with seed oils [68] Type of analysis, analyzed compounds, type of NMR spectroscopy and NMR frequency and application are reported. a Magnetic field is reported as corresponding 1 H Larmor frequency even for 31 P and 13 C.…”

Volatile compounds of Algerian extra-virgin olive oils: Effects of cultivar and ripening stage

“…[8,9] Another important factor that influences VOO volatile compounds composition, is the ripening degree which is in turn strongly dependent on other factors; ripening is in fact directly related to both genetic characteristics, and environmental conditions. [7,11] In Algeria, olive trees existed since the 12th millennium BC. The olive growing area is spread over an area of 330,000 hectares and concentrated mainly in the central region of the country, i.e., the Kabylie area.…”

“…[7,8] The cultivar is one of the main factors that can determine the content and profile of VOO volatile compounds. [5,8] Its effect was evidenced by the presence of different amounts of C6 compounds arising from oils produced under the same operating conditions of the extraction process of different fruit cultivars harvested at the same ripening stage.…”

Dynamic changes in composition of extracts of natural products as monitored by in situ NMR

“…The glycosidic bond of 1 (Scheme ) is easily hydrolyzed to yield the aglycon during the fruit ripening, crushing, and manufacturing process, which causes subsequent biotransformation of the oleuropein aglycon due to a keto‐enol tautomeric equilibrium that involves ring opening and, lastly, decarboxylation . Numerous spectroscopic techniques, such as 1 H NMR, 1 H gradient diffusion NMR, carbon‐13 NMR, phosphorus‐31 NMR, gas chromatography‐mass spectrometry, liquid chromatography‐NMR, ion‐spray ionization, LC‐atmospheric pressure chemical ionization, electron spray time‐of‐flight mass spectrometry, and ion‐trap multiple mass spectrometry, have been utilized to separate and identify phenolic compounds in olive oil and olive leaves. Nevertheless, the complete structural characterization is very problematic because of the variety in the structures of secoiridoids and the complexity of their interconversion …”