Article
To read the full-text of this research, you can request a copy directly from the authors.

Abstract

Nutritional and healthy values are well known properties of virgin olive oil (VOO). The product quality, in terms of belonging to a specific quality grade (extra virgin, virgin, lampante), is defined by a set of chemical-physical and sensory measurements. According to the official regulation of the European Union (EU Reg. 1348/2013)the free acidity is the first parameter that has to be determined by analysts; it gives information about the quality of the olives used to produce the VOO as well as the hydrolytic state of VOO just produced and stored. The official procedure is based on an acid-base titration that needs to be carried out in a chemical laboratory. In this paper a portable battery-operated electronic system to measure olive oil free acidity is presented: the system can be used for quick “in situ” tests in a production environment (olive oil mills or packaging centers)by people without particular training. The working principle of the system is based on the creation of an emulsion between oil and a hydroalcoholic solution: the free acidity is estimated on the value of the emulsion electrical conductance. The proposed system has been calibrated and in-house validated showing good results in terms of limit of detection and quantification, precision and accuracy. Moreover, a good correlation (R ²adj = 0.97)with free acidity data obtained applying the official method on 30 olive oil samples belonging to different commercial categories (extra virgin, virgin and lampante olive oil)has been evidenced.

No full-text available

Request Full-text Paper PDF

To read the full-text of this research,
you can request a copy directly from the authors.

... The working principle is based on the measurement of the electrical characteristics of an emulsion between a suitable reagent and the olive oil sample. The work represents a continuation of the research line presented in [23], where the battery-operated portable sensor system was presented for the first time and its ability to estimate the free acidity was validated on a set of 30 fresh olive oil samples. In the current work, tests have been carried out on a set of 40 virgin olive oils, composed of both fresh and oxidized samples. ...
... In the case of a portable sensor system for in-the-field measurements, the operative temperature cannot be considered constant, thus a compensation algorithm has been developed to calculate the emulsion electrical conductance at the target temperature of 23.5 • C (G m,23.5 • C ) from the emulsion electrical conductance at the environmental temperature (G m,T ) and the value of the environmental temperature (T). The calculation of G m,23.5 • C can be made with the following equation [23]: ...
... Before each measurement, the sensor vial and the electrodes were washed using distilled water and dried before performing the measurement. At the end of the Reprinted with permission from Ref. [23]. 2022 Elsevier. ...
Article
Full-text available
Virgin olive oil quality is assessed by chemical as well as sensory analysis. Two of the most important parameters that define the quality of virgin olive oils are the free acidity and the peroxide index. These chemical parameters are usually determined by manual titration procedures that must be carried out in a laboratory by trained personnel. In this paper, a portable sensor system to support the quality grade assessment of virgin olive oil is presented. The system is battery operated and characterized by small dimensions, light weight and quick measurement response (about 30 s). The working principle is based on the measurement of the electrical conductance of an emulsion between a chemical reagent and the olive oil sample. Two different chemical reagents have been investigated: (1) a hydro-alcoholic solution (HAS), made of 60% ethanol and 40% distilled water; (2) 100% distilled water (DW). Tests have been carried out on a set of 40 olive oil samples. The results have shown how, for most of the fresh virgin olive oil samples (31 samples out of 40), the free acidity can be estimated with good accuracy from the electrical conductance of the emulsion using HAS as the reagent. In the case of the full set of samples, the emulsion electrical conductance, using HAS as the reagent, is a function of both the sample free acidity as well as the compounds produced by oil oxidation, and a compensation method based on the measured electrical conductance, using DW as the reagent, has been introduced to improve the accuracy in the estimated free acidity. Tests have also been carried out on the full set of samples, using a k-nearest neighbors algorithm, to demonstrate the feasibility of olive oil classification according to the quality grade. The results have shown how measurements carried out using only the HAS reagent provide better classification accuracy than measurements carried out using both the HAS and DW reagents. The proposed system can be a low-cost alternative to standard laboratory analyses to evaluate the quality grade of virgin olive oil.
... The %FFA of samples stored at C4 (30 ± 2 • C) and C5 (40 ± 2 • C) conditions, both in darkness, increased beginning after 6 months, reaching a statistically higher value (p < 0.05) of 0.32 % of oleic acid in the C5 condition compared to all other storage conditions. The increase in %FFA at higher temperatures might be due to higher hydrolytic activity of lipase enzymes on triacylglycerols that remain in the oil after extraction [5], which could be further influenced by the moisture levels in the oil [30]. In all conditions, the %FFA did not reach 0.8%, the maximum allowed by IOC for EVOO category [2], and were lower than those reported by Ayton et al. [5] when olive oil was stored at 37 • C without oxygen in darkness. ...
... β-scission of the C9-C10 linkage would then form an olefin, which would then form the compound (Z)-3nonenal [8], followed by isomerization to yield (E)-2-nonenal [44]. In light condition (C2) (E)-2-nonenal could be formed from the decomposition of 10-hydroperoxylinoleic acid [30]. ...
... β-scission of the C9-C10 linkage would then form an olefin, which would then form the compound (Z)-3-nonenal [8], followed by isomerization to yield (E)-2-nonenal [44]. In light condition (C2) (E)-2-nonenal could be formed from the decomposition of 10-hydroperoxylinoleic acid [30]. ...
Article
Full-text available
Commercialization of extra virgin olive oil (EVOO) requires a best before date recommended at up to 24 months after bottling, stored under specific conditions. Thus, it is expected that the product retains its chemical properties and preserves its ‘extra virgin’ category. However, inadequate storage conditions could alter the properties of EVOO. In this study, Arbequina EVOO was exposed to five storage conditions for up to one year to study the effects on the quality of the oil and the compounds responsible for flavor. Every 15 or 30 days, samples from each storage condition were analyzed, determining physicochemical parameters, the profiles of phenols, volatile compounds, α-tocopherol, and antioxidant capacity. Principal component analysis was utilized to better elucidate the relationships between the composition of EVOOs and the storage conditions. EVOOs stored at −23 and 23 °C in darkness and 23 °C with light, differed from the oils stored at 30 and 40 °C in darkness. The former was associated with a higher quantity of non-oxidized phenolic compounds and the latter with higher elenolic acid, oxidized oleuropein, and ligstroside derivatives, which also increased with storage time. (E)-2-nonenal (detected at trace levels in fresh oil) was selected as a marker of the degradation of Arbequina EVOO quality over time, with significant linear regressions identified for the storage conditions at 30 and 40 °C. Therefore, early oxidation in EVOO could be monitored by measuring (E)-2-nonenal levels.
... The %FFA of samples stored at C4 (30 ± 2 °C) and C5 (40 ± 2 °C) conditions, both in darkness, increased beginning after six months, reaching a statistically higher value of 0.32 % of oleic acid in C5 condition compared to all other storage conditions. The increase in %FFA at higher temperatures might be due to higher hydrolytic activity of lipase enzymes on triacylglycerols that remain in the oil after extraction [5], which could be further influenced by the moisture levels in the oil [32]. In all conditions, the %FFA did not reach 0.8%, the maximum allowed by IOC for EVOO category [2], and were lower than those reported by Ayton et al. [5] when olive oil was stored at 37 °C without oxygen in darkness. ...
... β-scission of the C9-C10 linkage would then form an olefin which would then form the compound Z-3-nonenal [8], followed by isomerization to yield E-2-nonenal [46]. In light condition (C2) E-2-Nonenal could be formed from the decomposition of 10-hydroperoxylinoleic acid [32]. ...
Preprint
Commercialization of extra virgin olive oil (EVOO) requires a best before date recom-mended at up to 24 months after bottling, stored under specific conditions. Thus, it is expected that the product retains its chemical properties and preserves its ‘extra virgin’ category. However, in-adequate storage conditions could alter the properties of EVOO. In this study, Arbequina EVOO was exposed to five storage conditions for up to one year to study the effects on the quality of the oil and the compounds responsible for flavor. Every 15 or 30 days, samples from each storage condition were analyzed determining physicochemical parameters, the profiles of phenols, volatile compounds, α-tocopherol and antioxidant capacity. Principal component analysis was utilized to better elucidate the relationships between composition of EVOOs and the storage conditions. EVOOs stored at -23 and 23 °C in darkness and 23 °C with light, differed from the oils stored at 30 and 40 °C in darkness. The former were associated with higher quantity of non-oxidized phenolic compounds and the latter with higher elenolic acid, oxidized oleuropein and ligstroside derivatives, which also increased with storage time. E-2-Nonenal (detected at trace levels in fresh oil) was selected as a marker of the degradation of Arbequina EVOO quality over time, with significant linear regressions identified for the storage conditions at 30 and 40 °C. Therefore, early oxidation in EVOO could be monitored by measuring E2-Nonenal levels.
... [17] Furthermore, specific olive (oil) applications concern the on-line evaluation of the oil content of olives during olive processing [18] and the measurement of olive oil acidity. [19] However, the application of handheld NIRS for distinction of EVOO from lower grade counterparts has not been done before. Considering those all, this kind of technology may also be promising as a rapid screening technique for the distinction of olive oil grades. ...
... L* (r = 0.21), b* (r = −0. 19), and moisture content (r = −0.27) (p < 0.05). ...
Article
Full-text available
Miniaturization of analytical technology has paved the way for in‐situ screening of foods. In the current study, the spectral features of olive oils are examined by handheld near‐infrared spectroscopy to explore the technology's capabilities to distinguish extra virgin olive oil (EVOO) from lower grade oils. Eighty EVOO, forty refined olive oil (ROO), and ten pomace olive oil (POO) samples are analysed for their spectral and compositional features. The latter included analysis of the fatty acids (FAs), the chlorophylls and carotenoids, chromatic coordinates and moisture contents. The 1350–1570 nm wavelength range appeared most suitable for distinction of the oils. One‐class classification models with three different classifiers are subsequently estimated using this range, and their quantitative performance is assessed from probabilistic data. Soft independent modeling of class analogies models appears to predict the identity of the oils with a high success rate. Compared to the other oils, POO comprises a significantly higher and lower proportion of polyunsaturated and monounsaturated FAs, respectively. Higher contents of chlorophylls, carotenoids, and moisture are noted for EVOO. The relevant spectral information for distinction of the oils correlates strongly with the degree of unsaturation of the oils as well as their levels of chlorophylls, carotenoids, and moisture. Practical Applications: The findings of this study demonstrate that the handheld NIRS technique is promising for future rapid screening of olive oil grades. The statistical methods used and the robust validation procedure will help potential users to select the optimal strategy for multivariate data analysis. In addition, the exploration of correlations with compositional characteristics provides insight into the handheld NIRS working mechanism in regard to EVOO authentication.
... The determination of the free acidity of olive oil is considered to be the first parameter to study for the evaluation of its quality and its hydrolysis state (Grossi et al., 2019). The determination of the acidity of the oil was based on a titration of free fatty acids with a solution of potassium hydroxide in the presence of a colored indicator. ...
Article
Full-text available
The consumer necessity for a good quality of olive oil in terms of its lipid and phenolic profiles is demanded to preserve a good health and to co mbat illnesses. The conformity of olive oil with the International Olive Council standards requires the determination of certain chemical parameters including free acidity, saponification and peroxide indices. Our study was based on a comparat ive evaluation of chemical quality indices and extraction of phenolic compounds from d ifferent samples of olive oil of different durations of storage, from different regions of Algeria and with different preparations. The most recent olive oil sample presented the least acidity (1.88%) and saponification index (185.32 mg of KOH/g of o il). However, the sample conserved for five years revealed the highest quantities of total phenolics (0.56 ± 0.02 mg GA E/g o il) an d flavonoids (0.174 ± 0.019 mg CE/g o il). Different results were collected comparing samples of olive oil fro m different regions fro m Algeria. Acid ity percentages were ranged fro m 0.7 to 3.1%, pero xide index fro m 8 to 53meqO2/Kg of oil and saponification number fro m 166.61 to 201.11 mg KOH/g of o il. Yields of phenolic extraction results revealed percentages from 0.11 to 0.24%. The traditionally prepared olive oil presented the best quality with an acidity of 1.01% and a saponification nu mber of 187.10 ± 13. 68 mg KOH/g o il. Whereas, the industrially prepared one exh ibited the lower number of pero xide with 8.30 ± 2.88 meqO2/ kg oil. The quality of olive oil was influenced by time, geographical region and mode of extraction. Conserved olive oils may be destined for the manufacture of soaps or the extraction of phenolic compounds.
... Schematic of the circuit for the measurement of the emulsion electrical conductance[13]. ...
Article
Full-text available
Olive oil quality is normally assessed by chemical analysis as well as sensory analysis to detect the presence of organoleptic defects. Two of the most important parameters that define the quality of olive oil are the free acidity and the peroxide index. These chemical parameters are usually determinated by manual titration procedures that must be carried out in a laboratory by trained personnel. In this paper, a portable sensor system to evaluate the quality grade of olive oil is presented. The system is battery operated and characterized by small dimensions, a light weight and quick measurement response. The working principle is based on the measurement of the electrical conductance of an emulsion between a hydro-alcoholic solution and the olive oil sample. Tests have been carried out on a set of 17 olive oil samples. The results have shown how for fresh olive oil samples, the olive oil’s free acidity can be estimated from the electrical conductance of the emulsion. In the case of oxidized olive oil, the measured electrical conductance is also the function of the oxidation level, and a conductance threshold can be set to discriminate between extra virgin olive oils and lower-quality grade oils. The proposed system can be a low-cost alternative to standard laboratory analysis to evaluate the quality grade of olive oil.
... There are also other analytical parameters of great importance for the classification, characterisation and control of virgin olive oil quality, frequently quantified before storage, among them: acidity coefficient [76], bitter taste coefficient (K 225 ) [77] and oleic acid-linoleic acid ratio [78]. ...
Article
Full-text available
Electrochemical sensors, sensor arrays and biosensors, alongside chemometric instruments, have progressed remarkably of late, being used on a wide scale in the qualitative and quantitative evaluation of olive oil. Olive oil is a natural product of significant importance, since it is a rich source of bioactive compounds with nutritional and therapeutic properties, and its quality is important both for consumers and for distributors. This review aims at analysing the progress reported in the literature regarding the use of devices based on electrochemical (bio)sensors to evaluate the bioactive compounds in olive oil. The main advantages and limitations of these approaches on construction technique, analysed compounds, calculus models, as well as results obtained, are discussed in view of estimation of future progress related to achieving a portable, practical and rapid miniature device for analysing the quality of virgin olive oil (VOO) at different stages in the manufacturing process.
... In recent years a strong increase in the adoption of mobile sensor systems was reported in different fields of application, such as: quality assessment of olive oil [4][5][6], electronic noses for food quality determination [7], characterization of tomato paste [8], determination of solid fat content in vegetable oils and fats [9], characterization and production control of ice-creams [10,11], environmental monitoring [12][13][14], particulate concentration measurement [15], toxic volatile organic compound detection [16], microbial analysis [17][18][19][20], corrosion detection in metal structures [21][22][23], control of industrial processes [24][25][26], characterization of saline solutions [27] and forensic analysis [28]. Moreover, the large diffusion of smart mobile phones (smartphones) that integrate powerful microprocessors with high processing capability, wireless communication protocols and a rich sensor set, makes the smartphone an optimal platform for sensing applications [29][30][31]. ...
Article
Full-text available
Wireless sensor network nodes and mobile devices are normally powered by batteries that, when depleted, must be recharged or replaced. This poses important problems, in particular for sensor nodes that are placed in inaccessible areas or biomedical sensors implanted in the human body where the battery replacement is very impractical. Moreover, the depleted battery must be properly disposed of in accordance with national and international regulations to prevent environmental pollution. A very interesting alternative to power mobile devices is energy harvesting where energy sources naturally present in the environment (such as sunlight, thermal gradients and vibrations) are scavenged to provide the power supply for sensor nodes and mobile systems. Since the presence of these energy sources is discontinuous in nature, electronic systems powered by energy harvesting must include a power management system and a storage device to store the scavenged energy. In this paper, the main strategies to design a wireless mobile sensor system powered by energy harvesting are reviewed and different sensor systems powered by such energy sources are presented.
... Although the quality parameters could not be compared with extra virgin oil [59], and the high acidity could impact on sensory characteristics of oil, such as flavor, the collateral characteristics make it still a very valuable oil. These oil benefits encourage the chemical industries versus the optimization of extraction process in order to accomplish the quality of the product [39]. ...
Article
Full-text available
Although hemp seed (HS) oil is characterized by more than 80% polyunsaturated fatty acids (PUFAs), a very high ω-6-to-ω-3 ratio is not a popular commodity. The aim of this work was to provide useful data about the bioactive components and cannabidiolic acid content in thirteen different commercial hemp seed oils. The investigated HS oils showed a good ω-6/ω-3 ratio, ranging from 1.71 to 2.27, massively differed in their chlorophylls (0.041–2.64 µg/g) and carotenoids contents (0.29–1.73 µg/g), as well as in total phenols (22.1–160.8 mg Gallic Acid Equivalents (GAE)/g) and tocopherols (3.47–13.25 mg/100 g). Since the high content of PUFAs in HS oils, photo-oxidative stability was investigated by determining the Thiobarbituric Acid Reactive Substances (TBARS) assay and extinction coefficient K232 and K270 after the photo-oxidative test. The percentage of increase in K232 and K270 ranged from 1.2 to 8.5% and from 3.7 to 26.0%, respectively, indicating good oxidative stability, but TBARS showed a 1.5- to 2.5-fold increase in oxidative behavior when compared to the initial values. Therefore, the diversity in bioactive compounds in HS oils, and their high nutritional value, suggest the need for a disciplinary booklet that well defines agronomic and post-harvest management conditions for achieving a good food objective.
Article
Extra-virgin olive oil (EVOO) is an important imported commercial product in China. This study comprehensively evaluated the quality of EVOOs imported from different countries into China based on chemical parameters and sensory attributes. Multivariate statistics were used to authenticate their geographical origins. 71.8% of the oils failed to meet the current official standards at inland and abroad established for commercial EVOO category. Pyropheophytin, defect attributes, peroxide value, and K270 were above the limits in 32%, 24%, 23%, and 5% of the failed samples respectively, while free acidity, K232 and delta K were above the limits in 4%. Fatty acids and delta ECN42 were beyond the limits in 2% of the failed samples. Linear discriminant analysis (LDA) and orthogonal partial least squares discriminant analysis (OPLS-DA) based on fatty acids and triacyglycerols succeeded in identifying the origin of olive oils. 3.5% of the total might be mislabelled the geographical origin. The main quality problems of the analyzed oils include oxidation, counterfeiting with refined oils and origin fraud. Considering the results and the fact that most EVOOs in China are imported from other countries, chemometrics combined with critical quality attributes should be an ideal way of EVOO quality control, protecting consumers from frauds.
Chapter
Optical spectroscopy can cover the wavelength region from 200 nm to greater than 25 μm, with near-infrared (NIR) occupying a small portion of this range. NIR instruments, with adequate performance for food analysis, are available at the price point of a good laptop and are the size of a computer mouse. A trained analytical chemist understands the concepts of representative sampling, as well as detection limits. In making a spectroscopic measurement in foods, both concepts are crucial. Much of the use of NIR spectroscopy in the food area is on complicated matrices. Although food systems are the bulk of NIR spectroscopy practices, food applications that involve handheld or portable devices are much less common in the literature. NIR spectroscopy has been used as a tool to predict quality parameters as well as classify various fruits. NIR spectroscopy has been used in several applications related to sweeteners and sugar products.
Article
Full-text available
Olive oil is a natural product that is used in various fields, such as medicine, cosmetics and nutrition. It is a food product that is characterized by the multitude of its properties and its economic value. For this reason, it has been adulterated by other vegetable oils which are cheaper and whose properties are similar to those of olive oil and for more the profit. In literature study, there are a lot of works about this oil for determinate and evaluate this authenticity by different ways and techniques. FRIR coupled with Chemometrics has many special advantages because it is having an important characteristic about your manipulation and results. The aim for this review is to evaluate the capacity and the reliability for each method used in the examiner quality of this oil, and to determinate its advantages and disadvantages.
Article
Full-text available
Electrical impedance spectroscopy (EIS), in which a sinusoidal test voltage or current is applied to the sample under test to measure its impedance over a suitable frequency range, is a powerful technique to investigate the electrical properties of a large variety of materials. In practice, the measured impedance spectra, usually fitted with an equivalent electrical model, represent an electrical fingerprint of the sample providing an insight into its properties and behavior. EIS is used in a broad range of applications as a quick and easily automated technique to characterize solid, liquid, semiliquid, organic as well as inorganic materials. This paper presents an updated review of EIS main implementations and applications.
Article
Full-text available
Quality grading of Atlantic salmon (Salmo salar) is currently a task performed manually by human operators. To stay competitive in an increasingly global market, it becomes necessary to take advantage of technology to improve productivity and profitability. The Norwegian salmon industry sees the need to automate quality grading, in order to reduce tedious manual labor and to increase product consistency and production flexibility. A machine vision system for external 3D imaging in color, with a 360° scanning cross-section, has been developed for the purpose of quality grading of Atlantic salmon. The two primary causes of downgraded salmon are deformities and wounds. Two classifiers were developed, based on 3D geometric features and color information, to handle each of these primary causes of downgrading. These classifiers are able to detect deformities and wounds, with discrimination efficiencies of 86% and 89% respectively. This work shows that 3D machine vision can enable real-time automatic quality grading of Atlantic salmon. Many of the methods employed are general enough to translate to other species of fish or similar applications with minor modifications.
Article
Full-text available
Under the alternating electrical excitation, biological tissues produce a complex electrical impedance which depends on tissue composition, structures, health status, and applied signal frequency, and hence the bioelectrical impedance methods can be utilized for noninvasive tissue characterization. As the impedance responses of these tissue parameters vary with frequencies of the applied signal, the impedance analysis conducted over a wide frequency band provides more information about the tissue interiors which help us to better understand the biological tissues anatomy, physiology, and pathology. Over past few decades, a number of impedance based noninvasive tissue characterization techniques such as bioelectrical impedance analysis (BIA), electrical impedance spectroscopy (EIS), electrical impedance plethysmography (IPG), impedance cardiography (ICG), and electrical impedance tomography (EIT) have been proposed and a lot of research works have been conducted on these methods for noninvasive tissue characterization and disease diagnosis. In this paper BIA, EIS, IPG, ICG, and EIT techniques and their applications in different fields have been reviewed and technical perspective of these impedance methods has been presented. The working principles, applications, merits, and demerits of these methods has been discussed in detail along with their other technical issues followed by present status and future trends.
Article
Full-text available
Virgin olive oil is an important ingredient of the Mediterranean diet highly appreciated for its beneficial health effects due to the presence of mono-unsaturated fatty acids and antioxidant properties. The olive oil quality is defined by many parameters, among which acidity and peroxide index and according to international regulations, these two determinations are carried out in laboratory environment, by means of manual titration. This kind of method, however, cannot be used on oil production sites, where, instead, it would be desirable to know the main characteristics of the oil for proper product classification. In this paper a new technique to measure olive oil acidity by electrical conductance is presented that allows for fast, costeffective and on-site measurements. Such a technique has been validated with a set of 55 olive oil samples. Two different oil emulsions have been used and compared for the measurements: based on a hydro-alcoholic solution (60% ethanol 40% distilled water) and distilled water, respectively. The data show that the electrical conductance of the emulsion with hydro-alcoholic solution is a strong function of the olive oil acidity, that can be estimated with good accuracy (R2 = 0.9308). The experiments with distilled water, instead, exhibit no significant correlation between oil acidity and emulsion conductance that, however, is found to provide information about peroxide index, polyphenols content and filtration technique. Furthermore, using both types of emulsions to compensate for conductance variations other than free fatty acids the accuracy in acidity determination can be improved reaching R2 = 0.9786.
Article
Full-text available
Bioimpedance analysis is a noninvasive, low cost and a commonly used approach for body composition measurements and assessment of clinical condition. There are a variety of methods applied for interpretation of measured bioimpedance data and a wide range of utilizations of bioimpedance in body composition estimation and evaluation of clinical status. This paper reviews the main concepts of bioimpedance measurement techniques including the frequency based, the allocation based, bioimpedance vector analysis and the real time bioimpedance analysis systems. Commonly used prediction equations for body composition assessment and influence of anthropometric measurements, gender, ethnic groups, postures, measurements protocols and electrode artifacts in estimated values are also discussed. In addition, this paper also contributes to the deliberations of bioimpedance analysis assessment of abnormal loss in lean body mass and unbalanced shift in body fluids and to the summary of diagnostic usage in different kinds of conditions such as cardiac, pulmonary, renal, and neural and infection diseases.
Article
Full-text available
Sine wave signals are widely used in electronic applications such as digital oscilloscopes calibration, speech analysis and electrochemical sensors. In particular, impedance based microbial biosensors detect bacterial concentration by stimulating the sample with a sinusoidal test signal and measuring its electrical characteristics. Thus, for reliable microbial biosensing, fast and accurate sine wave analysis is mandatory. Many algorithms for the estimation of sinusoidal parameters exist that provide accurate estimate but are based on time consuming iterative procedures and/or need good starting values for the sine parameters. In this paper a linear non iterative algorithm based on the least squares method is presented that allows sinusoidal voltages analysis in a fast and efficient manner. The algorithm has been tested either with simulation analysis either with real impedances and the results proved to be accurate enough for reliable bacterial concentration measurement.
Article
Full-text available
A new method for determining acid values in vegetable oils has been developed for a nontitration pH-metric technique with a reagent consisting of 0.20 M triethanolamine in a 1∶1 solution of water and isopropanol. The emulsive properties of this reagent provide rapid (within a minute) and quantitative extraction of free fatty acids from an oil into the solvent phase. Acid values were determined by measuring conditional pH of the emulsified reagent in a pH-meter with an aqueous reference electrode. Three different applications of this technique are discussed.
Article
Full-text available
Electrical impedance measurements were used to characterize changes in intracellular and extracellular resistance as well as changes in the condition of membranes during ripening of nectarines (Prunus persica [L.] Batsch cv Fantasia). These measurements were related to changes in fruit texture assessed by flesh firmness and apparent juice content. An electrical model indicated that, during ripening (d 1-5) of freshly harvested fruit, the resistance of the cell wall and vacuole declined by 60 and 26%, respectively, and the capacitance of the membranes decreased by 9%. Accurate modeling of the impedance data required an additional resistance component. This resistance, which declined by 63% during ripening, was thought to be associated with either the cytoplasmic or membrane resistance. Changes in tissue resistance measured using low frequencies of alternating current were closely related to flesh firmness. After storage at 0[deg]C for 8 weeks, the nectarines developed a woolly (dry) texture during ripening at 20[deg]C. The main difference between these chilling-injured nectarines and fruit ripened immediately after harvest was the resistance of the cell wall, which was higher in woolly tissue (4435 [omega] after 5 d at 20[deg]C) than in nonwoolly tissue (2911 [omega] after 5 d at 20[deg]C). The results are discussed in relation to physiological changes that occur during the ripening and development of chilling injury in nectarine fruit.
Article
Full-text available
Among vegetable oils, virgin olive oil (VOO) has nutritional and sensory characteristics that to make it unique and a basic component of the Mediterranean diet. The importance of VOO is mainly attributed both to its high content of oleic acid a balanced contribution quantity of polyunsaturated fatty acids and its richness in phenolic compounds, which act as natural antioxidants and may contribute to the prevention of several human diseases. The polar phenolic compounds of VOO belong to different classes: phenolic acids, phenyl ethyl alcohols, hydroxy-isochromans, flavonoids, lignans and secoiridoids. This latter family of compounds is characteristic of Oleaceae plants and secoiridoids are the main compounds of the phenolic fraction. Many agronomical and technological factors can affect the presence of phenols in VOO. Its shelf life is higher than other vegetable oils, mainly due to the presence of phenolic molecules having a catechol group, such as hydroxytyrosol and its secoiridoid derivatives. Several assays have been used to establish the antioxidant activity of these isolated phenolic compounds. Typical sensory gustative properties of VOO, such as bitterness and pungency, have been attributed to secoiridoid molecules. Considering the importance of the phenolic fraction of VOO, high performance analytical methods have been developed to characterize its complex phenolic pattern. The aim of this review is to realize a survey on phenolic compounds of virgin olive oils bearing in mind their chemical-analytical, healthy and sensory aspects. In particular, starting from the basic studies, the results of researches developed in the last ten years will be focused.
Article
Statistical and artificial intelligence learning algorithms such as Principal Component Analysis (PCA) and Support Vector Machine (SVM) are widely used in many meat quality assessment applications to classify and predict the freshness of beef meat. This paper presents the implementation of the PCA and SVM algorithms on an embedded system based on a Digital Signal Processor (DSP). A dataset of eighty-one hue, saturation, and intensity (HSI) beef meat images was used. The PCA is used as a projection and prediction model where the SVM is used for the classification and identification of the beef meat. Results obtained from PCA projection model on a desktop system using Matlab software show the projection of three groups which represent the degree of beef meat freshness during the days of cold storage. A perfect prediction of the new unknown samples was obtained by PCA prediction model. A successful rate 100% of classification and identification was obtained by SVM. The PCA and SVM methods were implemented on the C6678 multi-core DSP. The implementation results of these algorithms were similar as those obtained by Matlab software. The processing time of the algorithms measured on the embedded system was lower compared to the desktop system. The embedded platforms based on DSP as portable tools can be used to predict or identify the sample beef meat freshness anywhere and in real-time.
Article
The main chemical and physical parameters of veiled and filtered virgin olive oils (VOOs) that are linked to its health and sensory properties, such as phenolic and volatile compounds, were evaluated during a four-month simulated shelf life at room temperature during which the oils were exposed to diffused light for 12 h per day. The specific settings of the vertical centrifuge used to treat the four industrial VOO samples extracted in different Mediterranean areas determined the “veiling” stabilization and reduced the formation of deposits at the bottom of the oil bottles. Cryo-SEM of the veiled oils showed the presence of micro-dispersed water particles that did not contain apparent vegetable fragments. By the end of the storage period, the changes in the quality parameters showed no negative effects on the oxidative stability of the veiled oils compared to the filtered oils. A higher phenolic concentration of Tunisian, Spanish, Greek and Italian veiled VOOs (50.8, 110.1, 389.6 and 389.4 mg/kg, respectively) was detected at the end of storage period compared to filtered samples (20.1, 83.2, 196.1 and 209.6 mg/kg, respectively).
Article
The effects of a cooling treatment of olive paste were studied to evaluate the impact of six Italian cultivars on the phenolic and volatile compounds of extra virgin olive oil (EVOO) strictly related to its health and sensory quality. The EVOOs, extracted using a continuous industrial system (2.5 ton/h), exhibited a significant increase in phenolic composition of Frantoio, Gentile, Leccino and San Felice cultivars. Significant modifications of the volatile profiles were obtained; the sum of aldehydes, mainly represented by the concentration of (E)-2-hexenal, showed increases for all the cultivar processed, while the sum of alcohols and esters appeared to be more affected by the genetic origin of the olive cultivars and their varying enzyme specific activities related to the lipoxygenase pathway.
Article
Most Metalworking Fluids (MWFs), widely used for cooling and lubrication, consist of oils diluted in water in concentration ranging from 1% to 10%. To guarantee good performance and reliability of both machines and processes, oil concentration should be maintained (approximately) constant, hence also measured at regular intervals to compensate for significant deviations from the optimal value. The official technique to measure oil concentration in MWFs is titration with 0.5M HCl solution and endpoint detection obtained measuring the sample pH. Such a method is accurate and substantially insensitive to sample contamination, but must be carried out in a laboratory, while fast, inexpensive and in-situ measurements would be desirable for effective process and machine control. This paper presents a system to measure oil concentration in MWFs that is new in that: a) titration is made automatic using a stepper motor; b) the end-point is detected by means of electrical conductance measurements. Experimental results show a very good correlation (R² = 0.9793) between the oil concentrations of prepared solutions and those measured with the proposed technique, while the presented system is suitable for in-situ operation within working environment.
Article
The quality of virgin olive oils is assessed through the determination of several analytical parameters, whose values must be within the ranges established by the different institutions involved. In addition to official methods, there is a strong need for simple, rapid, and environmentally friendly techniques for the quality control of virgin olive oils and for addressing the challenging task of determining geographical origin and detecting adulterants. Towards this purpose, some of the most interesting applications based on optical spectroscopic techniques, on the measurement of electrical characteristics and on the use of instruments equipped with electronic chemical sensors, including also other promising techniques are herein discussed. These techniques, adequately coupled to an appropriate statistical approach, appear to be promising for assessment of several quality-related parameters. The prediction of sensory attributes and of the oxidative status of virgin olive oils have also been reviewed by adopting these selected techniques, which are also considered to be potentially appropriate solutions for identification of the geographical origin of virgin olive oils and to assess their adulteration with cheaper oils. Overall, the techniques discussed are promising and cutting-edge approaches for the establishment of useful portable instruments for in-situ monitoring of the quality of virgin olive oils.
Article
In order to evaluate the reliability and the practical use of the electrical impedance spectroscopy method applied in the area of salt resistance, electrical impedance spectra were compared in the leaves of halophyte plants cultivated under different growth conditions (biotope versus controlled conditions, hydroponic versus sand system cultures) and different salt stress conditions. The kinetic of impedance parameters was also monitored under short term salinity. The spectra of electrical impedance of leaves under biotope and laboratory conditions showed difference in the electrical response of Cakile maritima in the biotope and laboratory conditions. The response of electrical impedance parameters to salinity was also different in the hydroponic system when compared to the soil one, indicating more stressful conditions in solution culture. The amplitude of the curves of impedance spectrometry decreased when plants were stressed comparatively to their controls, with the highest electrical resistance in the presence of 50 and 100 mM while the lowest value was at 400 mM NaCl. The electrical resistance increased at an early stage after the application of salt stress reaching maximal value 180 min later, before it rapidly declined thereafter. The observed peak can translate a signal, that the plant could have received, which triggers a cascade of metabolic reactions allowing the plant to regain its hydro-ionic balance. In conclusion, electrical impedance spectroscopy can be used to quickly compare different growth conditions as well as different salinity treatments. This method can also separate between the osmotic and the ionic phases of the response to salt stress.
Article
The inhibitive effect of ultrafiltrated oil palm fronds (OPF) lignins on the corrosion of mild steel in 0.5 M HCl solution has been investigated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PP) and weight loss measurement. The presence of smaller lignin fractions reduces remarkably the corrosion rate of mild steel. The highest corrosion inhibition efficiency for all ultrafiltrated lignins were attained at maximum concentration of 500 ppm (IEP.Soda: 87 % > IEP.Organosolv: 83 % > IEP.Kraft: 81 %). The results from this corrosion test clearly reveal that all ultrafiltrated lignins behaved as a mixed-type inhibitor with predominant anodic (organosolv lignin) or cathodic (alkaline lignin) effectiveness. It was deduced that the inhibition process was spontaneous and the inhibitors were mainly physically adsorbed onto the mild steel surface.
Article
The present paper deals with the adsorption and inhibitory effects of the pyridine derivatives, namely 2-amino-6-(2,4-dihydroxyphenyl)-4-(4-methoxyphenyl)nicotinonitrile (ADP) and 2-amino-4-(4-methoxyphenyl)-6-phenylnicotinonitrile (AMP) on N80 steel corrosion in 15% HCl. Among the studied compounds, ADP showed the inhibition efficiency of 90.24% at 200 mg/L. The corrosion study was performed by gravimetric, electrochemical impedance spectroscopy (EIS), Tafel polarization, scanning electron microscopy (SEM), scanning electrochemical microscopy (SECM) and energy-dispersive X-ray spectroscopy (EDX) techniques. The Langmuir isotherm model showed the best fit. The quantum chemical study was used to support the experimental results. 2015 Elsevier Ltd. All rights reserved.
Article
This paper evaluates the performance of the current analytical methods (standard and widely used otherwise) that are used in olive oil for determining fatty acids, triacylglycerols, mono and di acylglycerols, waxes, sterols, alkyl esters, erytrodiol and uvaol, tocopherols, pigments, volatiles and phenols. Other indexes that are commonly used, such as free acidity and peroxide value, are also discussed in relation to their actual utility assessing quality and safety and their possible alternatives. The methods have been grouped based on their applications: (i) purity and authenticity; (ii) sensory quality control; and (iii) unifying methods for different applications. The speed of the analysis, advantages and disadvantages, and multiple quality parameters are assessed. Sample pre-treatment, physicochemical and data analysis, and evaluation of the results have been taken into consideration. Solutions based on new chromatographic methods or spectroscopic analysis and their analytical characteristics are also presented.
Article
The present research investigated the correlations between capacitance and water content of extra virgin olive oils (EVOO). A commercial capacitor probe for radio applications and an LCR meter were used for electric tests in the frequency range from 500 Hz to 512 kHz. Seventeen samples of different EVOO with a moisture content ranging from 178 to 1321 mg/kg oil were selected for study. To assess the influence of moisture only, the oil with the maximum water content was filtered down to 288 mg/kg oil and five samples with intermediate water contents were prepared and submitted to electrical measurements. Subsequently, the capacitance of all 17 EVOO samples was measured at selected frequencies.Water content and capacitance for filtered oil were linearly correlated, showing R2 values up to 0.959 and a root mean square error (RMSE) of 48 mg/kg oil at 2 kHz. When the main oil composition together with the moisture changed, the trend was always linear, but the correlation (R2) decreased to 0.818 with an RMSE value of 123 mg/kg oil (at 8 kHz), so that the system remains suitable for screening of water content. Strong correspondences between capacitance and impedance suggest that these measurements can be carried out with very simple instruments for measuring voltage and current. Some novel linear correlations also emerged between water content, capacitance and fatty acid composition.
Article
For the impedance measurement system for plant tissues, a stable current source, the magnitude of which may be affected by the capacity of the operational amplifier, loading and high-frequency noise. Hence, this application note describes the use of a second-generation current conveyor (CCII) to improve the electrical circuit, plus a voltage buffer is used to significantly reduce the loading effect. A personal computer is integrated with LabVIEW software for data collection, analysis and processing. This forms a highly-effective measurement system which improves the portability of the measurement instrument. Within the frequency range 100Hz–1MHz, two groups of precision resistance-capacitance are adopted: 49.98kΩ, 1.01nF; 49.98kΩ, 9.8nF to execute the measurement simulation. The results of simulation measurement show that all the errors are within 5%, and the relative standard deviation within 0.30%, and these confirm that the system is highly accurate and precise in this implementation. Carrot is chosen as the target object for practical evaluation, for which the electrical impedance spectrum is a circular arc with its circular center below the real axis. Results for carrot are presented.
Article
Electrical characterization of products is gaining increasing interest in the food industry for quality monitoring and control. In particular, this is the case in the ice-cream industry, where machines dedicated to store ice-cream mixes are programmed “ad hoc” for different groups of products. To this purpose, the present work shows that essential product classification (discrimination between milk based and fruit based ice-cream mixes) can be done by means of a technique based on the measurements of non-linear response in the electrical behavior of the electrode-electrolyte interface. The addition of pH measurements allows to further reach the three parts classification occasionally required for advanced applications. The proposed idea is validated by means of measurements on 21 ice-cream mixes, different for producers and composition.
Article
The objective of analytical method validation is to ensure that every future measurement in routine analysis will be close enough to the unknown true value for the content of the analyte in the sample. Classical approaches to validation only check performance against reference values, but this does not reflect the needs of consumers. A holistic approach to validation also takes into account the expected proportion of acceptable results lying inside predefined acceptability intervals.In this article, we give a detailed step-by-step guide to analytical method validation, considering the most relevant procedures for checking the quality parameters of analytical methods. Using a holistic approach, we also explain the estimation of measurement uncertainty and accuracy profiles, which we discuss in terms of accreditation requirements and predefined acceptability limits.
Article
Reliable analytical data are a prerequisite for correct interpretation of toxicological findings in the evaluation of scientific studies, as well as in daily routine work. Unreliable analytical data might not only be contested in court, but could also lead to unjustified legal consequences for the defendant or to wrong treatment of the patient. Therefore, new analytical methods to be used in forensic and/or clinical toxicology require careful method development and thorough validation of the final method. This is especially true in the context of quality management and accreditation, which have become matters of increasing relevance in analytical toxicology in recent years. In this paper, important considerations in analytical method validation will be discussed which may be used as guidance by scientists wishing to develop and validate analytical methods.
Article
A chemometric method has been developed for the determination of acidity and peroxide index in edible oils of different types and origins by using near infrared spectroscopy (NIR) measurements. Different methods for selecting the calibration set, after an hierarchical cluster analysis, were applied. After discrimination of olive oils from maize, seed and sunflower, the prediction capabilities of partial least squares (PLS) multivariate calibration of NIR data were evaluated. Several preprocessing alternatives (first derivative, multiplicative scatter correction, vector normalization, constant offset elimination, mean centering and standard normal variate) were investigated by using the root mean square error of validation (RMSEV) and prediction (RMSEP), as control parameters. Under the best conditions studied, the validation set provides RMSEP values of 0.034 and 0.037% (w/w) for acidity in (I) olive oil group and (II) sunflower, seed and maize oils group. RMSEP values for peroxide in both sample groups, expressed as mequiv.O2 kg(-1), were, respectively 1.87 and 0.79. The limit of detection of the methodology developed was 0.03% for acidity in both groups of edible oils (I and II), and 0.9 and 0.8 mequiv.O2 kg(-1) for peroxide in the olive oil and other edible oils groups, respectively. In fact, the methodology developed is proposed for direct acidity quantification and for the screening of peroxide index in edible oils, requiring less than 30 s per sample without any previous treatment.
amending Regulation (EEC) No 2568/91 on the characteristics of olive oil and olive-residue oil and on the relevant methods of analysis
Commission Implementing Regulation (EU) No 1348/2013 of 16 December 2013 amending Regulation (EEC) No 2568/91 on the characteristics of olive oil and olive-residue oil and on the relevant methods of analysis.
  • M Grossi
Commission Regulation (EEC) No 2568/91 of 11 July 1991 on the characteristics of olive oil M. Grossi, et al. Food Control 104 (2019) 208-216
  • M Grossi
M. Grossi, et al. Food Control 104 (2019) 208-216