Olive Oil Quality Research Articles

The Effect of Harvesting Time on Olive Fruits and Oils Quality Parameters of Tortiglione and Dritta Olive Cultivars

AbstractDespite the fact that Italy holds the most important olives heritage in the world, with about 800 cultivars, most of them are still underestimated, in particular those from Abruzzo, a region located in the center of the peninsula. The aim of this work is to study the changes in quality parameters of olive fruits and related oils of two autochthonous Abruzzo olive cultivars, Tortiglione and Dritta during ripening (from September to November 2017). Both cultivar and ripening time affect the chemical parameters of olive fruits. Results highlight an increasing trend of the oil content with final values, based on fresh matter, of 38.7 ± 0.3% and 38.1 ± 0.9% for Tortiglione and Dritta, respectively. Olive oils chemical composition is also affected by ripening time and cultivar, with Tortiglione oils resulting generally richer than Dritta oils; on the first sampling time (30th of October) values for total phenolic content, antioxidant activity, and chlorophylls are 803.8 ± 68.2 mg gallic acid equivalent kg−1, 2.7 ± 0.5 mmol trolox equivalent kg−1, and 30.8 ± 1.6 mg pheophytin a kg−1, respectively. Tocopherols seem to be more affected by ripening time than by cultivar, in particular for Dritta.Practical Application: The results on Abruzzo minor olive cultivars indicate that olive fruits and olive oil composition are strongly influenced by both cultivar and ripening time, giving rational indications about the optimal cultivar specific harvesting time and opening interesting opportunities for olive oil producers in a perspective of sustainable production to obtain high quality fruits and oils. The research provides detailed information about Tortiglione and Dritta olive cultivar, useful in the global context of revaluation of Italian minor olive varieties.

Attitudes towards Olive Oil Usage, Domestic Storage, and Knowledge of Quality: A Consumers' Survey in Greece.

Consumption of unbranded olive oil obtained in bulk has previously been reported to be very high in Greece, underlining the need to investigate knowledge regarding its health attributes and storage practices, two areas that can affect oil quality. This study aimed to investigate Greek consumers’ use and choice of olive oil, their knowledge about its quality, as well as domestic storage practices of olive oil. A cross-sectional survey was conducted in a representative sample of 857 Greek households that consume olive oil, using a previously validated questionnaire. Most participating households use olive oil produced by themselves or by their extended family or friends (60.3%), and only 27.4% purchase branded olive oil, while 57% reported using extra virgin olive oil (EVOO). Only 38.4% of the respondents reported optimal domestic storage practices to maintain olive oil quality, with a significant greater percentage of non-producers group compared to olive oil producers. In all areas of Greece, the higher the knowledge of olive oil quality, the higher the probability of consumers selecting EVOO and perceiving olive oil price as low. The present survey highlights the need to heighten consumers’ knowledge of olive oil attributes and correct storage practices and awareness about branded EVOO and its superior quality.

Simple fluorescence imaging to identify the purity of olive oil: an activity in an optics course

The current pandemic era demands distance learning, including physics experiments on the topic of optics. One of the optical phenomena that needs to be explained in optic courses is fluorescence. This study offers a simple home experiment regarding the application of fluorescence, namely to identify the purity of olive oil using simple fluorescence imaging. This fluorescence imaging experiment used a 532 nm green laser as a beam source and a smartphone camera as an image capture detector. Olive oil samples were mixed with mineral oil to obtain various variations of olive oil purity. When the sample was induced with a laser, the laser beam path changed colour to orange due to fluorescence phenomena. This fluorescence effect was then captured in the form of images. Fluorescence intensity converted from the Grey value of the laser beam path image. The experimental results show a linear relationship between fluorescence intensity and olive oil purity with a determination coefficient R 2 = 0.98. This experiment can be an offer to explain the application of fluorescence with activities carried out independently by tertiary-level physics students in their respective homes. This fluorescent imaging procedure can also be related in terms of its application in olive oil quality control.

Modification of 13-hydroperoxide lyase expression in olive affects plant growth and results in altered volatile profile

The C6 aldehydes, alcohols, and the corresponding esters are the most important compounds of virgin olive oil aroma. These C6 volatile compounds are synthesized via the 13-hydroperoxide lyase (13-HPL) branch of the lipoxygenase pathway. In this investigation, a functional analysis of the olive (Olea europaea L.) 13-HPL gene by its overexpression and silencing in olive transgenic lines was carried out. With this aim, sense and RNAi constructs of the olive 13-HPL gene were generated and used for the transformation of embryogenic olive cultures. Leaves from overexpressing lines showed a slight increase in 13-HPL gene expression, whereas RNAi lines exhibited a strong decrease in their transcript levels. Quantification of 13-HPL activity in two overexpressing and two RNAi lines showed a positive correlation with levels of transcripts. Interestingly, RNAi lines showed a high decrease in the content of C6 volatiles linked to a strong increase of C5 volatile compounds, altering the volatile profile in the leaves. In addition, the silencing of the 13-HPL gene severely affected plant growth and development. This investigation demonstrates the role of the 13-HPL gene in the biogenesis of olive volatile compounds and constitutes a functional genomics study in olive related to virgin olive oil quality.

Effects of deficit irrigation on ‘Koroneiki’ olive tree growth, physiology and olive oil quality at different harvest dates

Agricultural water demand in the Mediterranean region is expected to increase due to climate change. The application of deficit irrigation practices may improve the efficiency of water use in orchards, by accounting for changes in environmental conditions and in the tree growth. The main goal of this study was to improve our understanding on the effect of deficit irrigation on physiology, morphology, yield, and oil quality of ‘Koroneiki’ olive trees. The effect of two deficit irrigation treatments and three harvest dates on olive yield and oil quality were investigated in a 17-year old, low-density ‘Koroneiki’ orchard in Cyprus, during a high crop load year. For the sustained deficit irrigation (SDI) treatment 70% ETc was applied over the irrigated period, while the regulated deficit irrigation (RDI) consisted of 70% ETc during water-stress sensitive growth stages (shoot growth, flowering, bud initiation) and 35% ETc during water-stress tolerant growth stages (pit hardening, oil accumulation). Environmental conditions and volumetric soil water content of the 70-cm rootzone were monitored. A Kc of 0.37 was derived for the irrigated period from daily water balance computations, excluding rain days. No significant effects of the two irrigation treatments were found on morphology, physiology, fruit yield and oil quality. Midday stem water potential reached − 4 MPa in September as a result of increasing fruit load. Leaf conductance ranged between 65 and 228 mmol m-2s-1, with highest values obtained under high soil water conditions and a vapour pressure deficit of 3.6kPa. Yields were approximately 9tonsha-1 in both irrigation treatments while water productivity was 1.4 and 1.0 kg oil m-3 irrigation water in SDI and RDI, respectively. Maximum phenolic content was found in early December, reaching on average 202 mg kg-1 oil in both irrigation treatments. Overall, irrigation water use in RDI was 32% less than in SDI, whereas oil quality was only affected by the harvest date.

Quality of veiled olive oil: Role of turbidity components

This study investigated the effects of water and content of solid particles, taken together as well as separately, on stability of veiled olive oil. The following oil samples were obtained through four different separation treatments: veiled, filtered, ‘solid-only’, and ‘water-only’. Changes in chemical, microbial, and sensory characteristics were evaluated during storage (240 days). A significant effect of hydrolysis was shown in veiled and ‘water only’ oils; in ‘solid-only’ oils, a slow increase of phenols was observed. A notable microbial activity, with resulting formation of volatile metabolites and sensory defects, was observed in veiled samples. Filtered oils underwent less significant changes.

How Did Sheep Save the Day? The Role of Dry Stone Wall Heritage and Agropastorality in Historical Landscape Preservation. A Case-Study of the Town of Cres Olive Grove

The dry stone wall landscape surrounding the town of Cres is a unique cultural landscape; it is one of the largest well-preserved historical olive groves in the Croatian Adriatic, while simultaneously serving as pasture for sheep. Still, there are currently no studies that capture this landscape as a multifunctional whole or which acknowledge its relevance within the current multidisciplinary discussions. The aim of this paper is to clarify past and current circumstances surrounding and affecting it. The study focuses on two main pillars of landscape preservation: (1) dry stone wall structures and (2) agro-pastoral practices; giving an overview of its historical formation and current management and trends. The goal is to establish knowledge that can be used as a foundation for the management of this area and present a good practice example for the preservation of historical landscapes in the Mediterranean region. The research involved combined desk and fieldwork: cartographic data analysis, literature analysis, GIS elaboration, terrestrial and aerial photographs and observations, followed by interviews with local informants. Continuous investing in the production of quality olive oil and the evolution of the landscape into a multifunctional agro-pastoral-touristic space is what enabled its preservation. This multifunctionality can only be matched by a diversity of scientific studies and this study aimed at providing the first step—a foundation for the identification of the values of the Cres landscape, with the scope of better precising further planning and management.

Effect of degree of ripening on the quality of virgin olive oils produced in Longnan, China

AbstractThe main purpose of this work was to study the effect of different ripening degree (0–7) on quality of two monovarietal olive oils (Arbequina and Arbosana) produced in Longnan region, located in the northwest of China, Gansu province. The qualitative characteristics of oils are evaluated by analysis of the principal quality parameters and chemical composition, such as: free acidity, peroxide value, K232, K270, oxidative stability, fatty acid composition, total phenols, flavonoids content and flavor profile. The maximum oil yields were obtained for both varieties at a ripening degree of 7 (13.26% and 23.59%). The Arbequina and Arbosana oils contained oleic acid (ranged 53.16%–58.92% and 66.30%–74.30%, respectively) and linoleic acid (ranged 15.51%–18.77% and 7.25%–9.45%), respectively. The ratio of MUFA/PUFA ranged from 2.93 to 3.77 and 6.73 to 9.84, respectively. The ratio of 18:1/18:2 presented ranges of 2.84–3.79 and 7.02–9.94, respectively. A significant relationship was observed between the total polyphenols (83.48–140.53 and 118.32–230.00 mg GAE⋅kg−1), flavonoids (0.43–9.00 and 10.20–5.51 mg RE⋅kg−1) and the oxidative stability. E–Nose could effectively identify and distinguish between different varieties and ripening degree of olive oil, especially that change in the W1W (sulfur‐organic) sensor. A principal component analysis showed that the particular effect of ripening degree in the cultivars olive oils.

Water Addition During Oil Extraction Affects on Virgin Olive Oil Ethanol Content, Quality and Composition

AbstractEthanol is the alcoholic precursor of fatty acid ethyl esters (FAEEs) in virgin olive oil (VOO). Because of its miscibility, water addition during oil extraction may affect oil ethanol content and then, the FAEEs synthesis during oil storage. In this work, the effect of water addition on VOO ethanol content and composition is studied. Water addition at two extraction systems (two and three phases) is compared and for vertical centrifuge, water addition at different temperatures is assayed. Ethanol content, quality parameters, and healthy components are determined in the oils. Results indicate three phase system gives oils with a 25% lower ethanol content than two phases. Ethanol reduction because of water addition is more important for three phases system (≈14%). For vertical centrifugation, ethanol is lowered as water dose and temperature increase. In general, water addition for any of the extraction steps analyzed reduces the oil ethanol concentration but other aspects such as fruity intensity and phenol content are also lowered.Practical applications: Virgin olive oil final ethanol content, and then its FAEEs concentration, does not only depend on the health and conservation status of olives, but also on the extraction system used and the amount of water added to the extraction process. The knowledge of the impact on ethanol content of water addition during oil extraction can be useful for olive oil legislators in order to keep the approved limits of FAEEs or to modify them. For oil producers, results can help to reduce the oil ethanol content and then FAEEs synthesis during virgin olive oil storage.

Non-destructive Fluorescence Spectroscopy as a Tool for Discriminating Between Olive Oils According to Agronomic Practices and for Assessing Quality Parameters

A non-destructive fluorescence method combined with chemometric algorithms has been developed for discriminating between olive oils. The excitation-emission matrices (EEMs) of two olive oil varieties (Arbosana and Oliana) from two crop seasons, which had undergone two different irrigation treatments (control irrigation strategy and regulated deficit irrigation (RDI)), were recorded. EEMs were analysed using parallel factor analysis (PARAFAC), followed by linear discriminant analysis (LDA) incorporating three PARAFAC components. This analysis was able to discriminate between olive oils according to crop season (100% of predictions in the validation set were correct) and variety (100% of predictions were correct). Moreover, good discrimination (80% of correct predictions) was also achieved when examining olive oils belonging to the same variety but submitted to two different irrigation treatments. Further, the olive oil quality parameters obtained using conventional methods were compared with those obtained using unfolded partial least squares (U-PLS). Good correlation coefficients were obtained for Rancimat hours (r = 0.87), K270 (r = 0.75) and total polyphenol content (r = 0.94).

Automatic System for the Detection of Defects on Olive Fruits in an Oil Mill

The ripeness and sanitary state of olive fruits are key factors in the final quality of the virgin olive oil (VOO) obtained. Since even a small number of damaged fruits may significantly impact the final quality of the produced VOO, the olive inspection in the oil mill reception area or in the first stages of the productive process is of great interest. This paper proposes and validates an automatic defect detection system that utilizes infrared images, acquired under regular operating conditions of an olive oil mill, for the detection of defects on individual fruits. First, the image processing algorithm extracts the fruits based on the iterative application of the active contour technique assisted with mathematical morphology operations. Second, the defect detection is performed on the segmented olives using a decision tree based on region descriptors. The final assessment of the algorithm suggests that it works effectively with a high detection rate, which makes it suitable for the VOO industry.

Comparison of four classification statistical methods for characterising virgin olive oil quality during storage up to 18 months

This study examines the ability of fluorescence spectroscopy for monitoring the quality of 70 Moroccan virgin olive oils belonging to three varieties and originating from three regions of Morocco. By applying principal component analysis and factorial discriminant analysis to the emission spectra acquired after excitation wavelengths set at 270, 290, and 430 nm, a clear differentiation between samples according to their storage time was observed. The obtained results were confirmed following the application of four multivariate classification methods: partial least squares regression, principal component regression, support vector machine, and multiple linear regression on the emission spectra. The best prediction model of storage time was obtained by applying partial least squares regression since a coefficient of determination (R2) and a root mean square error of prediction (RMSEP) of 0.98 and 24.85 days were observed, respectively. The prediction of the chemical parameters allowed to obtain excellent validation models with R2 ranging between 0.98 and 0.99 for free acidity, peroxide value, chlorophyll level, k232, and k270.

Cold Storage and Temperature Management of Olive Fruit: The Impact on Fruit Physiology and Olive Oil Quality—A Review

Cold storage of olive fruit has been the subject of study for over more than 50 years. From the 1990s on, an increasing amount of knowledge is build-up about the impact of the conservation on the physiological response of the fruit as well as on the quality of the extracted oil therefrom. This review offers a comprehensive synopsis of this research, discusses the most important influential factors and summarizes the results on the influence of the studied parameters on both the fruit and the oil. Currently, changing climatic conditions, new harvesting techniques and a more demanding consumer market are triggering the need to broaden this strict focus on conservation. A more dynamic view on the effects of temperature from the moment the fruit is harvested up to the oil extraction process, reveals the necessity to manage this crucial influential factor more diversely. An overview of how this management can take form is structured through a focus on the different phases of the postharvest processing and the widely different harvesting scales. Future prospects of research are presented based on the actual state of the art of cold storage research as well as on the necessities that come forward from a broader fruit temperature management perspective.

Evolution of Extra Virgin Olive Oil Quality under Different Storage Conditions.

The extent and conditions of storage may affect the stability and quality of extra virgin olive oil (EVOO). This study aimed at evaluating the effects of different storage conditions (ambient, 4 °C and −18 °C temperatures, and argon headspace) on three EVOOs (low, medium, and high phenols) over 18 and 36 months, analyzing the main metabolites at six time points. The results showed that low temperatures are able to maintain all three EVOOs within the legal limits established by the current EU regulations for most compounds up to 36 months. Oleocanthal, squalene, and total phenols were affected by storage temperatures more than other compounds and degradation of squalene and α-tocopherol was inhibited only by low temperatures. The best temperature for 3-year conservation was 4 °C, but −18 °C represented the optimum temperature to preserve the organoleptic properties. The present study provided new insights that should guide EVOO manufacturers and traders to apply the most efficient storage methods to maintain the characteristics of the freshly extracted oils for a long conservation time.

Response of Oil Production and Quality to Hedgerow Design in Super-High-Density Olive cv. Arbequina Orchards

An analysis is presented of the response of olive oil production and quality parameters, viz. fatty acids (palmitic, oleic and linoleic acids), phenolic compounds and oxidative stability to hedgerow spacing and orientation in 1-m wide super-high-density orchards of cv. Arbequina. Data reveal strong linear relationships between concentrations of fatty acids and internal irradiance within hedgerows, positive for palmitic and linoleic but negative for oleic acid. The result is a significant vertical trend in oil composition within hedgerows, but small to negligible differences in oil harvested from them in totality. The explanation is found in the small ranges and strongly correlated responses of individual fatty acids that together comprise 98% of oil mass. Phenolic compounds respond more widely and to higher levels of irradiance than fatty acids and did show increases in NS hedgerows grown at wide row spacing. Oxidative stability shows a similar trend in phenolic compounds. A simulation study that extended the known responses to 2-m wide hedgerows showed that the linkage between fatty acid profiles was maintained with no resultant differences in the oil composition of the total simulated oil harvest. Based on the current understanding of internal irradiance within olive hedgerows, there seems to be little opportunity to manage oil quality by orchard structure.

Study of the Evolution of Pigments from Freshly Pressed to 'On-the-Shelf' Extra-Virgin Olive Oils by Means of Near-UV Visible Spectroscopy.

Spectroscopic non-destructive methods have high potentialities as fast, cheap and easy-to-be-used approaches to address olive oil quality and authenticity. Based on previous research where near-UV Visible spectroscopy was used to investigate extra-virgin olive oils (EVOOs) and their main pigments’ content (i.e., β-carotene, lutein, pheophytin a and pheophytin b), we have implemented the spectral deconvolution method in order to follow the EVOO’s life, from ‘freshly pressed’ to ‘on-the-shelf’ EVOO samples at different storage time. In the first part of the manuscript, the new implemented deconvolution spectroscopic method aimed to quantify two additional pigments, namely chlorophyll a and chlorophyll b, is described and tested on ‘ad hoc’ samples with known concentrations of chlorophylls. The effect of light exposure and acidification was investigated to test the reliability and robustness of the spectral deconvolution. In the second part of the work, this approach was used to study the kinetic of pigments’ degradation in several monocultivar fresh EVOO samples under optimal storage’s conditions. The results here reported show that this spectroscopic deconvolution approach is a good method to study fresh EVOOs too; moreover, the proposed method revealed to be sensitive to detect eventual stresses of olive oil samples stored in not-good conditions.

Zeytinyağı üretim aşamalarının zeytinyağının fizikokimyasal özellikleri ve fenolik bileşenleri üzerine etkisi

Aims: In this study, it was aimed to investigate the effect of industrial-scale continuous extraction process stages (crushing, malaxation and decantation) on physicochemical (oil contents, L*, a*, b*, free acidity, peroxide values) and bioactive properties (total phenolic content, antioxidant activity and phenolic compounds) of olive oil. Methods and Results: The samples of olive, olive paste after crushing and malaxation, and olive oil after decantation, which were obtained from olive oil factory, were used for analyses. The highest oil (56.80%) and the lowest total phenolic (160.70 mg L-1) contents were determined after malaxation process at 35°C for 20 min. The free fatty acid value of olive oil increased from 1.68% to 2.46%, but the peroxide value of oil decreased from 12.5 meq O2 kg-1 to 1.5 meq O2 kg-1 after decanter. The L*, a* and b* values of olive oils were determined between 73.82 and 82.04, -12.60 and -3.71, 14.22 and 45.78, respectively. Moreover, phenolic compounds were not significantly affected from industrial oil extraction process (p> 0.05). The minimum oleic acid (68.58%), and the maximum linoleic acid (11.57%) and palmitic acid (14.66%) concentrations were observed in olive oil obtained from malaxed olive paste. Conclusions: The results of oil yield, fatty acid composition and total phenolic content of samples showed significant differences after the malaxation process. Significance and Impact of the Study: It has been determined that the malaxation process is the extraction stage which significantly affects the quality of olive oil.

Elevated Temperatures Negatively Affect Olive Productive Cycle and Oil Quality

Climate change, with elevated temperatures throughout the year, affects many stages of the reproductive growth and development of olives as well as oil quality at harvest. Although olive (Olea europaea L.) is well adapted to the environmental conditions of the Mediterranean Basin, agricultural techniques and breeding through selection programs will have to adapt to these climate change, threatening to worsen in the near future. Defining the pathways controlling high fruit productivity and oil quantity and quality, despite elevated temperatures and sub-optimal growing conditions, is important for coping with current and predicted climate changes. As breeding programs aiming to address these crucial changes may take several decades, an urgent need to designate specific olive cultivars that are more resistant to high temperatures emerges.

Influence of Olive Maturity and Season on the Quality of Virgin Olive Oils from the Area Assigned to the Protected Designation of Origin of “Aceite de la Alcarria” (Spain)

This work aimed to assess the influence of olive maturity and oil season on the potential quality of monovarietal virgin olive oils from the area assigned to the Protected Designation of Origin of “Aceite de la Alcarria” (Spain), analysing the regulated physicochemical quality and sensory parameters, the stability parameters and composition of fatty acids, sterols and triterpenic dialcohols. To complete the study, we also characterised the coupage olive oils made in the oil mills located in the PDO area (real quality). The main variety grown in La Alcarria is Castellana, whose oils are characterised by a high content of palmitic acid (14.27% with olives in veraison, 13.81% with ripe olives), a low content of linoleic acid (5.03% with olives in veraison, 5.98% with ripe olives) and a total phenol content higher than the rest of varieties grown in the area (between 350 and 500 mg of caffeic acid/kg depending on the season considered), which is reflected in higher oxidative stability values (induction time of 50.65 h at 100 °C). In addition, they have a sterol content below that established by the regulations (<1000 mg/kg). The olive oils produced using olives in veraison presented a lower level of acidity and peroxide index, more intense fruitiness, an absence of defects in all the samples and higher oxidative stability, compared to those produced using ripe olives, and thus early harvest of the olives is recommended. It was also found that the season affects the physicochemical composition of the oils, although these changes tend to be of little significance, with the characteristics of the variety being maintained, regardless of the harvesting season analysed. The coupage virgin olive oils produced in the mills registered under the PDO of Aceite de la Alcarria, representative of their real quality, showed, as expected, similar values to those observed in the monovarietal virgin olive oils produced using the Castellana variety, which is clearly predominant in the study area. The characterization of oils from local varieties allows one to obtain a greater variability in terms of the sensory notes of extra virgin olive oil.

Identification and Quantification of Olive Oil Quality Parameters Using an Electronic Nose

An electronic nose (EN), which is a kind of chemical sensors, was employed to check olive oil quality parameters. Fifty samples of olive oil, covering the four quality categories extra virgin, virgin, ordinary virgin and lampante, were gathered from different Palestinian cities. The samples were analysed chemically using routine tests and signals for each chemical were obtained using EN. Each signal acquisition represents the concentration of certain chemical constituents. Partial least squares (PLS) models were used to analyse both chemical and EN data. The results demonstrate that the EN was capable of modelling the acidity parameter with a good performance. The correlation coefficients of the PLS-1 model for acidity were 0.87 and 0.88 for calibration and validation sets, respectively. Furthermore, the values of the standard error of performance to standard deviation (RPD) for acidity were 2.61 and 2.68 for the calibration and the validation sets, respectively. It was found that two principal components (PCs) in the PLS-1 scores plot model explained 86% and 5% of EN and acidity variance, respectively. PLS-1 scores plot showed a high performance in classifying olive oil samples according to quality categories. The results demonstrated that EN can predict/model acidity with good precision. Additionally, EN was able to discriminate between diverse olive oil quality categories.