Complementary Untargeted and Targeted Metabolomics for Differentiation of Extra Virgin Olive Oils of Different Origin of Purchase Based on Volatile and Phenolic Composition and Sensory Quality.

In order to differentiate the extra virgin olive oils (EVOO) of different origin of purchase, such as monovarietal Italian EVOO with protected denomination of origin (PDO) and commercial-blended EVOO purchased in supermarkets, a number of samples was subjected to the analysis of volatile aroma compounds by both targeted gas chromatography/mass spectrometry (GC-MS) and untargeted profiling by comprehensive two-dimensional gas chromatography/mass spectrometry (GC×GC-TOF-MS), analysis of phenols by targeted high-performance liquid chromatography/mass spectrometry (HPLC-DAD-ESI/MS), and quantitative descriptive sensory analysis. Monovarietal PDO EVOOs were characterized by notably higher amounts of positive LOX-derived C6 and C5 volatile compounds, which corresponded to the higher intensities of all the assessed positive fruity and green odor sensory attributes. Commercial-blended EVOOs had larger quantities of generally undesirable esters, alcohols, acids, and aldehydes, which coincided with the occurrence of sensory defects in many samples. Many minor volatile compounds that were identified by GC×GC-TOF-MS were found to differentiate each of the two investigated groups. The differences between the groups with respect to phenols and taste characteristics were evident, but less pronounced. The results that were obtained in this study have undoubtedly confirmed the existence of the large heterogeneity of oils that are sold declared as EVOO. It was shown that GC-MS, GC×GC-TOF-MS, and HPLC-DAD-ESI/MS analyses have complementary outputs, and that their use in combination has advantages in supporting the results of sensory analysis and objectively differentiating these groups of EVOO.

Effect of Different Clarification Methods on Volatile Aroma Compound Composition of Virgin Olive Oil.

This study investigates the effect of industrial scale filtration of fresh monovarietal virgin olive oil from Buza and Istarska bjelica cultivars on their volatiles, total phenols and sensory characteristics, and compares the oil samples clarified by filtration with those clarified by natural sedimentation/decantation after six months of storage. Filtration had a different effect on volatiles from the oil samples obtained from different cultivars. In the oil from Buza cultivar immediately after filtration only the amount of (Z)-2-pentenol slightly increased, but in Istarska bjelica the oil filtration affected eight compounds (the amount of hexanal, (E)-2-pentenal, (Z)-3-hexenal, (Z)-2-pentenol and (Z)-3-hexen-1-ol increased, while of hexyl acetate, (E)-2-penten-1-ol and (E)-2-hexen-1-ol decreased). In fresh filtered oil from Buza cultivar a slight decrease of total phenols was observed, while in those from Istarska bjelica the decrease was sharp, causing a decrease in the pungency and bitterness. Sedimentation/decantation had advantages over oil filtration of both cultivars, due to improved effect on the preservation of the sensory profile and the level of total phenols. Tentative aroma profiles based on odorant series obtained from the odour activity values were compared to the actual olive oil sensory profiles. These results could have a high level of applications in the olive oil industry for the optimization of the technology for obtaining monovarietal virgin olive oil with preserved specific and typical sensory characteristics, but also may serve experts to choose an appropriate virgin olive oil clarification method prior to analysis of volatile compounds.

Exploring the Connection between the Occurrence and Intensity of "Grubby" Defect and Volatile Composition of Olive Oil.

In order to investigate the relationship between the occurrence of the "grubby" sensory defect caused by olive fruit fly (Bactrocera oleae (Rossi)) infestation and the resulting volatile composition, virgin olive oils were extracted from olives of the Leccino cultivar with 0%, 50%, and 100% olive fly infestations and subjected to analysis of the basic chemical quality parameters, fatty acids and volatiles, and sensory analysis by the Panel test. A 100% olive fly infestation reduced the basic chemical quality of the oil, while the fatty acid composition was not affected in any case. The overall sensory quality score and intensity of the positive sensory attributes decreased, while the intensity of the "grubby" defect increased proportionally to the degree of infestation. The occurrence and intensity of this defect were clearly causally related to the concentrations of 3-methylbutanal, 2-methylbutanal, ß-ocimene, ethyl 2-methylbutyrate, dimethyl sulfoxide, 4-methyl-5H-furan-2-one, α-farnesene, 6-methyl-5-hepten-2-one, 1-octanol, E-2-nonen-1-ol, benzeneacetaldehyde, heptanal, and octanal, implying that the perception of "grubby" comes from their joint contribution to the overall olive oil flavour. In addition to contributing to the understanding of the chemical origin of "grubby", the results obtained could potentially be used to develop strategies to support sensory analysis in the classification of olive oil quality and the confirmation of the presence of this sensory defect in oil samples.

Compositional Changes during Storage of Industrially Produced Olive Oils Co-Milled with Olive Leaves.

The possibility of enriching the oil produced from Leccino cultivar olive fruits with phenolic and volatile compounds by adding olive leaves (2.5%) during industrial-scale production were investigated. Furthermore, the influence of the addition of leaves on the oil quality, composition, and oxidative stability during storage for 6 and 12 months was studied. A slight negative impact on the oil quality after processing with leaves was determined. The addition of leaves had no influence on the total saturated, monounsaturated, and polyunsaturated fatty acids in oils, while it influenced increases in total phenolic compounds (+29.55%), total secoiridoids (+29.43%), chlorophylls (+47.59%), and the oil stability index (+18.70%), and their higher values were also determined in the stored oils. The addition of leaves increased C5 volatiles (+10.50%) but decreased C6 volatiles (-10.48%). The intensity of most of the positive sensory characteristics increased in fresh oils obtained with leaves, and the established improvements were also maintained in the stored oils. The extractability of olive paste was positively affected by the addition of olive leaves, which increased the oil yield (+27.17%). The obtained results significantly contribute to the knowledge about the possibilities of enriching olive oils with bioactive compounds.

Compositional Changes in the Extra Virgin Olive Oil Used as a Medium for Cheese Preservation.

The influence of semi-hard (C1), hard (C2), and soft whey cheese (C3) immersed in extra virgin olive oil (EVOO) on its oxidative and hydrolytic parameters, fatty acids, and phenolic composition during two months of simultaneous storage was investigated. Accelerated hydrolytic and oxidative degradation was noted in EVOO stored with the immersed cheese compared to control oil. Oxidation indicator (K232), myristic (C 14:0), and trans-oleic fatty acid (C18:1t) exceeded the prescribed limit for the EVOO category in oils stored with immersed C1 and C2, which indicated that standard analytical parameters are ineffective as tools to examine the declared quality and authenticity of such topping oils. The noted changes in fatty acid profile were primarily prescribed to the migration of fats. C1 and C2 influenced a comparable reduction in EVOO total identified phenolic content (-92.1% and -93.5%, respectively), despite having a different content of total proteins and moisture, whereas C3 influenced a slightly lower reduction (-85.0%). Besides the protein profile, other cheese compounds (e.g., moisture, carbohydrates) have been shown to have a considerable role in the development of the EVOO phenolic profile. Finally, compositional changes in EVOO used as a medium for cheese preservation are under significant influence of the cheese's chemical composition.

Effect of Different Watering Regimes on Olive Oil Quality and Composition of Coratina Cultivar Olives Grown on Karst Soil in Croatia.

Croatian islands are olive growing areas characterized by poor conditions for olive trees because of karst soil and a precipitation deficiency. Under these conditions, irrigation is a very important factor for constant olive oil production. This paper aims to investigate the effects of different watering regimes on quantity, sensory and chemical quality and composition of Coratina cv. olive oil obtained from trees grown on ameliorate karst soil during two harvesting years. Olive trees were subjected to rainfed conditions and three different irrigation treatments (T1-deficit irrigation representing the usual producer's practice, T2-regulated deficit irrigation in respect to phenological stages, T3-full irrigation). Irrigation treatments increased oil yield compared to rainfed conditions (T1 + 58%, T2 + 66% and T3 + 74%, representing average values for both studied years). All olive oil samples were of extra quality. Irrigation led to a decrease in carotenoids, volatiles, polyunsaturated fatty acids and linolenic acid contents, with no difference found among irrigation treatments. Total phenols and secoiridoids concentration was not affected by irrigation, indicating that similar oil quality could be achieved with less demand on the water supply. Obtained results could help producers to define a suitable irrigation management in particular conditions of ameliorate karst.

Comparative Study of Volatile Compounds and Sensory Characteristics of Dalmatian Monovarietal Virgin Olive Oils.

Volatile compounds are chemical species responsible for the distinctive aroma of virgin olive oil. Monovarietal olive oils have a peculiar composition of volatiles, some of which are varietal descriptors. In this paper, the total phenolic content (TPC), fatty acid composition, volatile compounds, and sensory profile of monovarietal olive oils from four Dalmatian most common olive cultivars-Oblica, Lastovka, Levantinka, and Krvavica-were studied. The volatile composition of olive oils was analyzed using headspace solid-phase microextraction with gas chromatography/mass spectrometry. The highest mean TPC value was measured in Oblica and Krvavica oils (around 438 mg/kg). The difference among cultivars for fatty acids composition was detected for C16:1, C17:0, C18:1, C18:2, and the ratio C18:1/C18:2. Krvavica oils showed clear differences in fatty acid composition compared to oils from other cultivars. The most prevalent volatile compound in all oils was C6 aldehyde E-2-hexenal, with the highest value detected in Levantinka oils (75.89%), followed by Lastovka (55.27%) and Oblica (54.86%). Oblica oils had the highest value of Z-3-hexen-1-ol, which influenced its characteristic banana fruitiness, detected only in this oil. Lastovka oils had the highest amount of several volatiles (heptanal, Z-2-heptenal, hexanal, hexyl acetate), with a unique woody sensation and the highest astringency among all studied cultivars. Levantinka oils had the highest level of almond fruitiness, while Krvavica oils had the highest level of grass fruitiness.

Fruit quality and volatile compound composition of processing tomato as affected by fertilisation practices and arbuscular mycorrhizal fungi application.

The effects of different fertilisation treatments with arbuscular mycorrhizal fungi (AMF) inoculation on AMF root colonisation, fruit yield, nutrient and total phenol contents, volatile compound composition, and sensory attributes of tomato (Solanum lycopersicum L.) were investigated. Mineral, organic, and mineral + organic fertiliser application positively affected tomato yield (35%-50%) and phosphorus concentration (24%-29%) compared with controls. AMF application had a significant impact on the total nitrogen (+9%), manganese (+12%), and hydrophilic phenol (+8%) contents in the fruit. Volatile compounds were affected by the interactive effects of fertilisation and AMF application. The response of tomato fruit sensory quality indicators was relatively modest, with only a few sensory characteristics affected to a lesser extent. Although tomato showed susceptibility to field-native AMF, particular combinations of fertilisation and AMF inoculation were more effective at improving the quality parameters of tomatoes under field conditions applied in this study.

Olive Fruit Refrigeration during Prolonged Storage Preserves the Quality of Virgin Olive Oil Extracted Therefrom.

With the aim to investigate the influence of post-harvest olive fruit storage temperatures on virgin olive oil production parameters, composition and quality, Istarska bjelica (IB) and Rosinjola (RO) fruits were stored for seven days at room temperature (RT), +4 °C and -20 °C prior to oil production. Lower temperatures delayed post-harvest maturation of IB fruits. Theoretical oil content did not change depending on the storage temperature, while the highest oil yield and extractability index were obtained after storage at RT. Chlorophylls decreased in IB-RT and in IB-20. A decrease in the sensory quality of oils was detected after fruit storage at RT and -20 °C, while the refrigeration temperature of +4 °C preserved it. Regarding the content of fatty acid ethyl esters, an increase was observed in IB-RT oils. Storage at RT increased the content of waxes, while the lower temperatures partially suppressed this phenomenon. In oils of both cultivars, storage at +4 °C preserved the concentration of most phenolic compounds at a level more similar to that of the fresh oil when compared to the other two treatments. In the production conditions, when prolonged fruit storage is necessary, refrigeration seems to be the most suitable option.

Modification of the Sensory Profile and Volatile Aroma Compounds of Tomato Fruits by the Scion × Rootstock Interactive Effect.

Sensory quality is of increasing importance to consumer decisions in choosing a product, and it is certainly an important factor in repurchasing in terms of meeting the necessary aroma quality and taste properties. To better understand the effects of rootstocks and scions on fruit quality, the sensory profile and volatile aroma composition of the fruits of hydroponically grown tomato plants were evaluated. Experiments were established using the tomato cultivars Clarabella and Estatio as scions during two spring-summer seasons. In both experiments, the scion plants were self-grafted or grafted onto rootstocks of cultivars Arnold, Buffon, Emperador, and Maxifort, with the exception that in experiment 1, the Estatio scion was not grafted onto Buffon. The scions and rootstocks caused differences in observed sensory properties in both experiments. For most of the sensory traits, interaction effects between scion and rootstock were observed. Compared to those obtained from self-grafted Clarabella, the fruits obtained from Clarabella grafted onto Buffon in the first experiment and Clarabella grafted onto Arnold in the second experiment were sweeter by one measurement unit. The contents of seven aldehydes, six alcohols, five terpenes and two ketones were determined. A lower accumulation of total aldehydes, 22-45%, due to lower amounts of pentanal, (E)-2-heptanal and (E,E)-2,4-decadienal, was found in the fruits from plants where Estatio was rootstock compared with the other rootstocks treatments. Clarabella as a rootstock increased (Z)-3-hexenal + (E)-2-hexenal accumulation from 35 to 65%. Grafting Clarabella onto the tested rootstocks led to a change in the composition of volatile compounds, while differences between the combinations with Estatio as a scion were generally not recorded. Fruits from self-grafted Clarabella had higher (Z)-3-hexenal + (E)-2-hexenal concentrations than did fruits from Clarabella grafted onto Arnold (for 54%) and Emperador (for 68%), and in the second experiment, grafting onto all commercial rootstocks reduced (Z)-3-hexenal + (E)-2-hexenal concentrations, from 25 to 74%, compared to those from self-grafted Clarabella. Higher (+)-2-carene and (-)-caryophyllene oxide concentrations were attained in plants in which Clarabella was grafted onto Maxifort (by 56%) and plants in which Estatio was grafted onto Arnold (by 36%) compared to self-grafted plants. This study showed the possibility of altering the composition of volatile aroma compounds and sensory properties of tomato fruits by the use of grafting techniques.

Alignment and Proficiency of Virgin Olive Oil Sensory Panels: The OLEUM Approach.

A set of 334 commercial virgin olive oil (VOO) samples were evaluated by six sensory panels during the H2020 OLEUM project. Sensory data were elaborated with two main objectives: (i) to classify and characterize samples in order to use them for possible correlations with physical-chemical data and (ii) to monitor and improve the performance of panels. After revision of the IOC guidelines in 2018, this work represents the first published attempt to verify some of the recommended quality control tools to increase harmonization among panels. Specifically, a new "decision tree" scheme was developed, and some IOC quality control procedures were applied. The adoption of these tools allowed for reliable classification of 289 of 334 VOOs; for the remaining 45, misalignments between panels of first (on the category, 21 cases) or second type (on the main perceived defect, 24 cases) occurred. In these cases, a "formative reassessment" was necessary. At the end, 329 of 334 VOOs (98.5%) were classified, thus confirming the effectiveness of this approach to achieve a better proficiency. The panels showed good performance, but the need to adopt new reference materials that are stable and reproducible to improve the panel's skills and agreement also emerged.

Inter-Varietal Diversity of Typical Volatile and Phenolic Profiles of Croatian Extra Virgin Olive Oils as Revealed by GC-IT-MS and UPLC-DAD Analysis.

Despite having an interesting native olive gene pool and a rapidly emerging olive oil industry, monovarietal extra virgin olive oils (EVOO) from Croatia are relatively unexplored. To investigate the inter-varietal diversity of typical volatile and phenolic profiles of Croatian EVOO, 93 samples from six olive (Olea europaea L.) varieties were subjected to gas chromatography-ion trap mass spectrometry (GC-IT-MS) and ultra-performance liquid chromatography with diode array detection (UPLC-DAD), respectively. Quantitative descriptive sensory analysis was also performed. Analysis of variance extracted many relevant exclusive or partial discriminators between monovarietal EVOOs among the identified volatile compounds and phenols. Successful differentiation model with a 100% correct classification was built by linear discriminant analysis, while the most typical volatiles for each monovarietal EVOO were confirmed by partial least squares discriminant analysis. Diverse typical sensory attributes among the EVOOs were tentatively ascribed to the variations in the composition of volatiles and phenols. It was proven that the approach that comprises GC-IT-MS and UPLC-DAD analysis may provide additional objective information about varietal origin and typicity which successfully complement those obtained by sensory analysis. The approach was characterized as universal in nature, with a significant potential to contribute in strengthening the varietal identities and position on the market of monovarietal and Protected Denomination of Origin (PDO) EVOO.

Towards understanding the varietal typicity of virgin olive oil by correlating sensory and compositional analysis data: a case study.

To investigate if the anecdotal varietal typicity concepts for two monovarietal virgin olive oils (VOO) can be scientifically supported and explained, VOO samples were sorted according to typicity grade and related to sensory and compositional data for volatiles and phenols. Clear inter-varietal, as well as intra-varietal boundaries between more and less typical samples were established by univariate and multivariate statistics. A variety-typical complex odor was related to a complex VOO volatile composition with relatively high amounts of lipoxygenase-derived compounds, accompanied by hydrocarbons, terpenes, and benzenoids. A simpler odor, described mostly as green and typical for the other monovarietal VOO, coincided with the lower amounts of the same volatiles. The intensity of bitterness and pungency was mostly in correlation with the amount of major phenols. Two monovarietal VOOs were clearly distinguished with respect to their variety-typical expression of pungency: the one described as gradually increasing was tentatively related to pinoresinol, while the other, described as immediately strong and burning, was assumed to originate mainly from p-HPEA-EDA. Intra-varietal typicity grades correlated with hedonic liking, as well as with general VOO positive sensory attributes related to key volatiles and phenols.

Complex interactive effects of ripening degree, malaxation duration and temperature on Oblica cv. virgin olive oil phenols, volatiles and sensory quality.

The interactive effects of ripening degree, malaxation duration and temperature on Oblica cv. (Olea europaea L.) virgin olive oil phenols, volatiles, and sensory quality were investigated. Olives were picked at three ripening degrees with International Olive Council indices of 0.68, 2.48 and 4.10, and processed by malaxation at 22 and 30°C, and at both temperatures for 30 and 60min. Ripening exhibited the strongest effect, and malaxation duration the weakest. Phenols were generally found to decrease during ripening; however 3,4-DHPEA-EDA and p-HPEA-EDA increased. Similar behaviour was observed for (E)-2-hexenal. Higher malaxation temperature induced an increase in particular important phenols and C6 alcohols, while C6 aldehydes mostly decreased. Interactions between the factors were established, mostly between ripening degree and malaxation temperature: the effect of the latter was most pronounced for ripe olives, especially for 3,4-DHPEA-EDA, p-HPEA-EDA and C6 volatiles. Sensory attributes were generally in agreement with the chemical composition.

Influence of filtration on volatile compounds and sensory profile of virgin olive oils.

The influence of filtration through a hydrophilic cotton layer on volatile compounds, sensory characteristics and colour of two monovarietal oils was investigated in this study. Volatiles were evaluated using headspace solid-phase microextraction-gas chromatography. After the filtration of Buza oils only a slight increase in total alcohols was noticed. In filtered Crna oils a significant decrease of total alcohols and slight changes in total aldehydes, total ketones and total C5 volatile compounds concentration were detected. No significant influence on the sensory scores of oils, but some slight changes in sensorial profiles were noted (slightly higher intensities of sensory characteristics apple and grass, and higher values of the lightness L(∗) in filtered samples). The results point to unequal filtration impact on different monovarietal oils and could be useful in developing targeted technologies for specific monovarietal oils quality improvement.