Oxidative Stability Of Olive Oil Research Articles

Maximising olive oil by‐products

Maximising olive oil by‐products

Improving the oxidative stability of virgin olive oil using microformulated vitamin-C.

This study aims to improve the oxidative stability of olive oil using microformulated vitamin‐C (Vit‐C). The microemulsion containing 10,000 µg/ml Vit‐C with a droplet size of 1,000 ± 68 nm was first prepared. Free radical scavenging of olive oil and olive oil containing blank microemulsion, different amounts of formulated Vit‐C (100–500 µg/ml), and TBHQ (100 and 200 µg/ml as a standard antioxidant) was around 90% during 21 days of incubation at 60°C. The oxidative stability of the mentioned samples during incubation was investigated using the rancimat test, and their quality criteria analysis was studied by peroxide and the acid values. Results showed that the sample's acid value containing 500 µg/ml of Vit‐C did not show significant differences (p < .05) with samples containing TBHQ. However, samples containing TBHQ's peroxide value were significant (p < .05) lower than samples containing 500 µg/ml of Vit‐C. Furthermore, the induction time of samples containing 500 µg/ml of Vit‐C was significantly (p < .05) higher than other treatments during incubation. Thus, the prepared microemulsion could be used as a natural antioxidant in the oil industry instead of harmful synthetic TBHQ.

Zeytinyağının Bazı Fiziko-Kimyasal Özellikleri Üzerine, Ticari Antioksidan ve Esansiyel Yağ Bileşenlerinin Etkilerinin Belirlenmesi

Bu çalışmada, 60oC de birkaç baharat esansiyel yağının ve bazı bileşenlerin % 0.1 seviyesinde, zeytinyağının oksidatif stabilitesi üzerindeki antioksidan aktivitesi belirlenmiştir. Araştırma sonuçlarına göre, zeytinyağına farklı ilaveler ile yağın serbest yağ asitliği değerleri, birinci haftadan dördüncü haftaya kadar sırasıyla % 1.61-2.01, % 1.81-2.17, % 1.67-2.23, %1.79-2.62 arasında değişmiştir. Peroksit sayısı değerleri, birinci haftadan dördüncü haftaya kadar sırasıyla 11.98-15.10 meq O2/kg, 15.48-19.64 meq O2/kg, 18.22-27.50 meq O2/kg, 18.70-39.60 meq O2/kg arasında değişmiştir. Viskozite değerleri, 39.90-55.45 m.Pas, 53.35-59.60 m.Pas, 33.10-54.70 m.Pas, 34.00-50.80 m.Pas arasında değişmiştir. Araştırmanın ilk haftasında yağın peroksit değerleri 11.98 meq O2 / kg ile 15.10 meq O2 / kg (p <0.05) arasında değişmiştir. En zayıf etki, sater yağında belirlenmiştir. Thujene en yüksek antioksidan etkiyi göstermiş olup, ardından okaliptol, ocimene, mersin beyazı, BHA (bütillenmiş hidroksianisol) ve rezene izlemiştir. Zeytinyağlarının yağ asidi bileşimleri, esansansiyal yağlardan (% 0.1) ve buna karşılık gelen bazı bileşenlerden (% 0.01) kısmen etkilenmiştir. Zeytin yağının toplam yağ asidi miktarı % 96,86 ile% 99,99 arasında değişmiştir. En çok etkilenen yağ asitleri linoleik asit, ardından oleik ve linolenik asitler olmuştur.

A Kinetic‐Thermodynamic Study of the Effect of the Cultivar/Total Phenols on the Oxidative Stability of Olive Oils

AbstractPhysicochemical parameters, total phenols contents (TPC), and oxidative stabilities at 120–160 °C were evaluated for two monovarietal (Arbequina and Cobrançosa cultivars, cvs.) and one blend extra‐virgin olive oil, confirming the label quality grade and allowing grouping them according to the different TPC (TPC = 88 ± 7, 112 ± 6 and 144 ± 4 mg CAE/kg, for cv. Arbequina, blend and cv. Cobrançosa oils, respectively). The lipid oxidation rate increased with the decrease of the TPC, being Cobrançosa oils (higher TPC) more thermally stable. Kinetic‐thermodynamic parameters were determined using the activated complex/transition‐state theory and the values did not significantly differ for Cobrançosa and blend oils, which had the highest TPC, suggesting a hypothetically threshold saturation of the beneficial effect. Cobrançosa oils had a significant more negative temperature coefficient, higher temperature acceleration factor, greater activation energy and frequency factor, higher positive enthalpy of activation, lower negative entropy of activation, and greater positive Gibbs free energy of activation, probably due to the higher TPC. The results confirmed that lipid oxidation was a nonspontaneous, endothermic, and endergonic process with activated formed complexes structurally more ordered than the reactants. A negative deviation from the Arrhenius behavior was observed for all oils being the super‐Arrhenius behavior more marked for Arbequina oils that had the lowest TPC. Finally, the kinetic‐thermodynamic parameters allowed classifying oils according to the binomial olive cultivar/total phenols level, being the temperature acceleration factor and the Gibbs free energy of activation at 160 °C the most powerful discriminating parameters.

Change in some quality parameters and oxidative stability of olive oils with regard to ultrasound pretreatment, depitting and water addition

Ultrasound pretreatment with different times (0, 4, 8, 10 min) on olive paste previous malaxation of olive oil extraction along with depitting and water application procedures were studied. The effects of these procedures on oil yield, quality parameters and oxidative stability have been studied. Therefore, the olive oil yield increase with increasing time of ultrasound treatment. On the other hand, the application of ultrasound did not adversely affect the quality characteristics, as well as the antioxidant activity, when comparing with untreated paste. Furthermore, the oxidative stability data, we can conclude that ultrasound treatment can affect the olive oil oxidative stability. This study could provide useful information for industry to produce olive oil with high yield and quality.

EFFECTS OF FİLTRATİON PROCESS AND STORAGE TİME ON THE CHEMİCAL CHANGES AND SENSORY PROPERTİES OF OLİVE OİL EXTRACTED FROM TURKİSH USLU CULTİVAR

Upper Mesopotamia is a part of Turkish territory is the homeland of the olive tree with a wide range genetic resource. This is the first report on chemical composition and oxidative stability of olive oil extracted from Uslu cultivar grown locally in a small amount. In this research, a Turkish olive cultivar named as “Uslu” locally grown in Akhisar was used for production of monocultivar extra virgin olive oil by using Mobile Olive Oil Processing Unit”. Olive oil samples were bottled before and after filtration and stored up to 24 months. Some chemical properties such as free fatty acid content, peroxide value, moisture content, UV absorbance value, minor and major components (fatty acid composition, tocopherols, total phenol compounds and phenolic composition), were determined during storage for 24 months. Chemical parameters such as free fatty acid, peroxide value except UV absorption values of both filtered and unfiltered “Uslu” olive oil samples were in agreement with the trade standards of International Olive Council (IOC). Color values of EVOO changed from green to yellow while UV absorbance values altered during storage. Very low free fatty acidy (0.2%) values which are unusual for commercial olive oils in Turkey were obtained for filtered and unfiltered samples. A slight increase was seen for unfiltered sample at the end of storage. Filtration had no detectable effect on fatty acid profile. Filtered sample had higher total phenols (407.64±4.051 ppm) and α-tocopherol (237 and 123.31 ppm) contents than unfiltered ones and their contents decreased approximately 50% at the end of storage. Luteolin was the most abundant phenolic compound and its concentration decreased from 268.65±5.428 to 93.57±0.541ppm during storage. It seemed effect of filtration was more obvious on total phenolic contents. This study was good practice for producing premium extra virgin olive oil by using Mobile Olive Oil Processing Unit. The results obtained in this study showed that Uslu olive oils has a unique chemical composition and a good oxidative stability with high tocopherols and phenolics contents that are uncommon in most of the commercial olive oils.

Determination of the oxidative stability of olive oil using an integrated system based on dielectric spectroscopy and computer vision

During storage, olive oil may suffer degradation leading to an inferior quality level when purchased and consumed. Oxidative stability is one of the most important parameters for maintaining the quality of olive oil, which affects its acceptability and market value. The current methods of predicting the oxidative stability of edible oils are costly and time-consuming. The aim of the present research is to demonstrate the use of dielectric spectroscopy integrated with computer vision for determining the oxidative stability index (OSI) of olive oil. The most effective features were selected from the extracted dielectric and visual features for each olive oil sample. Three machine learning techniques were employed to process the raw data to develop an oxidative stability prediction algorithm, including artificial neural network (ANN), support vector machine (SVM) and multiple linear regression (MLR). The predictive models showed a great agreement with the results obtained by the Rancimat instrument that was used as a reference method. The best result for modelling the oxidative stability of olive oil was obtained using SVM technique with the R-value of 0.979. It can be concluded that this new approach may be utilized as a perfect replacement for quicker and cheaper assessment of olive oil oxidation.

The oxidative stability of flavoured virgin olive oil: the effect of the water activity of rosemary

Flavoured olive oil gained has importance in terms of its sensorial properties and oxidative stability in recent years. However, the water activity level of the flavouring agent can be important for oxidative stability. Therefore, the aim of this study was to determine the effect of the water activity of rosemary, which was used as a flavouring agent, on the oxidative stability of olive oil. For this purpose, rosemary samples were adjusted to different levels of water activity (0.17, 0.24 and 0.44) and used for the aromatization of virgin olive oils. At the end of the aromatization, the olive oil samples were exposed to an accelerated oxidation test at 60 °C for 28 days. The peroxide, p-anisidine, TOTOX (total oxidation index), free fatty acid, chlorophyll, carotenoid and specific extinction values of the samples were determined. According to the results, the oxidation of olive oils is limited by decreased water activity values in the rosemary samples. Moreover, unflavoured oils were identified as being more sensitive to oxidation when compared to flavoured oils. Additionally, storage time had important effect on all of the analysed parameters. The present research showed that the water activity of rosemary, when used as condiment, affected the oxidative stability and carotenoid content of virgin olive oil. Using rosemary with a low water activity value to flavour olive oil was more effective in terms of oxidative stability. These findings implied that the oxidation of flavoured olive oil could be decreased by decreasing the water content of the condiment used.

Development, characterization and application of hydroxypropylmethylcellulose films enriched with cypress seed extract.

The phenolic profile of cypress seed extract (CSE) was investigated by means of liquid chromatography with photodiode array and electrospray ionisation mass spectrometric detection (LC/PDA/ESI-MS). The total phenolic (TP) and flavonoid (TF) contents as well as the antioxidant capacity of CSE were determined. The effects of CSE concentration (0.1, 0.3, 0.5, 1, and 2% (w/v)) on the functional properties of hydroxypropylmethylcellulose (HPMC) films were studied. Results showed that CSE presents a good antioxidant capacity due to its high phenolic/flavonoid contents and particularly the presence of bi-flavonoid compounds including cupressuflavone and amentoflavone derivatives. The incorporation of CSE in HPMC films led to a significant decrease in their water vapor permeability (WVP) and enhanced their mechanical strength. The lowest WVP value, the greatest opacity and the highest antioxidant capacity were obtained with the highest CSE concentration. HPMC films with and without CSE were applied on virgin olive oil to study their effect on the oxidative stability of olive oil during accelerated storage by periodically analyzing changes in FTIR spectra and peroxide values. HPMC-2% CSE films were the most effective in lowering light transmission, and consequently decreasing peroxide formation and delaying oxidation of olive oil.

Chemical characterization and oxidative stability of olive oils extracted from olive trees of Southern Brazil

Abstract: The objective of this work was to characterize the chemical composition of olive (Olea europaea) oils produced in Southern of Brazil and correlate it with oxidative stability. Olive oils from the Arbequina, Coratina, Frantoio and Koroneiki cultivars were evaluated. A completely randomized experimental design was used, in a uniform arrangement, with three replicates. Acidity value, peroxide index, specific absorption, tocopherol content, phenolic compound content, carotenoid content, chlorophyll content, fatty acid profile, and oxidative stability were determined. The oils from the Coratina and Frantoio cultivars were classified as extra virgin-oils. The olive oil from the Coratina cultivar showed the highest levels of pigments, followed by the oil from Koroneiki. The oil from the Coratina cultivar also presents higher contents of phenolic compounds (1,725.5 mg kg-1) and tocopherols (437.8 mg kg-1). The major fatty acid in all samples is oleic acid.

Effect of unsaponifiable matter extracted from Pistacia khinjuk fruit oil on the oxidative stability of olive oil.

The present study was carried out to investigate the improvement of oxidative stability of refined olive oil using various concentrations of unsaponifiable matters extracted from Pistacia khinjuk fruit oil (UFO). For further elucidation of UFO antioxidative power, tertbutylhydroquinone (TBHQ) was used in an olive oil sample, too. Oxidative stability of olive oil samples without and with different levels of UFO (50, 100, 250, 500, 750 and 1000 ppm) and TBHQ (100 ppm) were studied via evaluation of conjugated diene value, carbonyl value, oil/oxidative stability index, acid value and total tocopherol (TT) contents through 8h thermal process at 170°C. Results obtained by oxidative stability assays revealed that the highest antioxidative activity of olive oil was obtained by 100ppm of UFO, followed using 100, 250, 500, 750, and 1000ppm of UFO and 100ppm TBHQ, respectively. Evaluation of the relationship between oxidative stability indexes and TT changes indicated a strong correlation (R2=0.9718) between mean relative resistance to oxidation and relative resistance to TT reduction during thermal process. By promotion of relative resistance to TT reduction, olive oil samples' relative resistance to oxidation was enhanced exponentially; implying importance of TT in promotion of oxidative stability of edible oils. The results obtained in this study showed that UFO has higher antioxidative activity compared to TBHQ; thus UFO can be considered as a natural antioxidant with ideal antioxidative activity.

Antioxidant properties of whole-cell Spirulina (Arthrospira platensis) powder expressed in olive oil under accelerated storage conditions

The antioxidant activity of whole-cell Spirulina (Arthrospira platensis) powder was assessed in olive oil at different concentrations of 0.5, 1.0, and 1.5% during accelerated storage. Also, antioxidant activity of Spirulina was compared with that of α-tocopherol and butylated hydroxytoluene (BHT). Spirulina samples exhibited lower primary, secondary, and total oxidation products than the control. In comparison with control (16.94 days), induction periods of various concentrations of Spirulina samples ranged from 19.09 to 20.71 days, indicating that different concentrations of Spirulina can improve the oxidative stability of olive oil. Furthermore, different concentrations of Spirulina improved olive oil stability up to between 12.69 and 22.24%. Spirulina samples can be efficient in their antioxidant activities as a result of the protective effects of bioactive components which are gradually released from Spirulina alga into the olive oil during storage. Among the antioxidants evaluated in this study, BHT showed the highest antioxidant activity, while α-tocopherol exhibited a poorer performance than Spirulina. In conclusion, Spirulina has noticeable antioxidant potential and therefore can be used in olive oil.

Oxidative stability of olive oil during the thermal process: Effect of Pistacia khinjuk fruit oil

ABSTRACTThe oxidative stability of refined olive oil with incorporated Pistacia khinjuk fruit oil (PKFO; 0.5%, 1%, 2%, 5%, and 10%) during thermal processing at 170ºC for 8 h was evaluated. The conjugated diene values, carbonyl values, acid values, oil/oxidative stability indices, and total tocopherol content were measured during thermal processing. Olive oil containing 0.5% PKFO was identified as the most oxidative stable oil followed by oils containing 100 ppm TBHQ and 1, 5, 10, and 2% PKFO. No significant difference between samples of olive oil containing 100 ppm TBHQ and 1% PKFO was observed. Thus, it was concluded that PKFO at levels lower than 1% could provide stronger antioxidation activity in comparison with TBHQ (the strongest syntactic antioxidant used in the food industry). Moreover, reduction in tocopherol compounds during thermal processing was higher in olive oil containing TBHQ as compared to those in pure olive oil.

Effect of Opuntia ficus-indica flowers maceration on quality and on heat stability of olive oil.

This study was focused on the evaluation of the quality and the oxidative stability of olive oil added with Opuntia ficus-indica flowers. Two different amounts of O. ficus-indica flowers were considered 5 and 15% (w/w). The olive oils were evaluated towards their quality, fatty acids profile, total phenol contents and thermal properties by differential scanning calorimetry. The oxidative stability was also monitored by employing the Rancimat and the oven test based on accelerating the oxidation process during storage. The addition of O. ficus-indica flowers induced an increase in free acidity values and a variation in fatty acids profile of olive oils but values remained under the limits required for an extra-virgin olive oil. The obtained olive oils were nutritionally enriched due to the increase in their phenols content. The oxidative stability was generally improved, mainly in olive oil enriched with 5% Opuntia ficus-indica flowers. These findings proved that this enriched olive oil could be considered as a product with a greater added value.

Improving oxidative stability of olive oil: Incorporation of Spirulina and evaluation of its synergism with citric acid

The effects of different Spirulina concentrations used alone and in combination with citric acid on the oxidative stability of olive oil were assessed. The amounts of primary and secondary oxidation products produced in Spirulina samples were lower than that of the control. The improved oxidative stability indices of Spirulina samples with and without citric acid were in the range of 85.20–94.47% and 258.10–260.21%, respectively. In comparison with the control, Spirulina samples manifested significantly higher carotenoid and chlorophyll contents at the beginning and end of the storage period. The presence of these bioactive compounds results from the presence of Spirulina in the medium and can thus retard the oxidation of olive oil. A higher oxidative stability was reached using BHT in comparison with Spirulina samples. Furthermore, no synergistic action was observed in possible connections between citric acid and Spirulina. In conclusion, Spirulina can enhance oxidative stability and improve the shelf life of olive oil.

Alterations in monovarietal, blended and aromatized Portuguese virgin olive oils under four storage conditions for 12 months

Though olive oil is a perishable product, there is not a European regulation for maximum consumption time after production, in part because its durability depends on the storage conditions. The main objectives of this study were to compare the influence of the type of storage on changes of Portuguese virgin olive oils and to verify whether the addition of Catostylus tagi could increase the oxidative stability of olive oil. Over 12 months, the conservation status of monovarietal and blended olive oils in four contexts possible to be used by the consumer was monitored. The analyzed parameters were chlorophyll content, free acidity, peroxide value, specific extinction coefficients at 232 and 270 nm and delta K. Spaced determinations of iodine index and total tocopherol contents complemented the study. Results showed that at Mediterranean temperatures and normal storage procedure, the mean time to reach maximum peroxides value was 12–13 months. At artificial light storage, C. tagi was effective in reducing peroxides evolution by 11 %.

The Effect of Storage Time on the Composition of the Olive and Sunflower Oils

The effect of storage time on the composition of the olive and sunflower oils has been investigated. It were studied parameters like free fatty acids (FFA), anisidine value (AV), iodine value (IV), saponification number (SN) and identification of the molecular structure through FT-IR method. During storage (48 months) an increasing in the values of parameters FFA and AV took place that measures the oxidative degradation of oils. The oxidative stability of olive oil stored at room temperature was less than of sunflower oil. Also, significant differences were found among the olive oil and sunflower oil during storage period.

Prediction of various chemical parameters of olive oils with Fourier transform infrared spectroscopy

Vibrational spectroscopic techniques offer advantages such as rapid and accurate measurements with minimum sample preparation and waste generation. In this study, it was aimed at determining some important quality parameters (oxidative stability, colour pigments, fatty acid profile and phenolic composition) of olive oils by Fourier transform infrared spectroscopy as one of the vibrational spectroscopic methods. Partial least square calibration models were constructed in order to reveal any correlation between quality parameters and spectral data. Regression coefficients for developed models showed that oxidative stability (0.99), chlorophyll content (0.98), some major fatty acids (palmitic (0.87), oleic (0.94), and linoleic acids (0.97), saturated (0.91), monounsaturated (0.94) and polyunsaturated fatty acids (0.97)), hydroxytyrosol as a phenolic compound (0.97) and total phenolic content (0.99) were predicted successfully. Variable influence on the projection values indicated that palmitic, vanillic and cinnamic acids and hydroxytyrosol are the most significant contributors to oxidative stability of olive oils.

Effect of Olive Oil Phenolic Compounds and Maltodextrins on the Physical Properties and Oxidative Stability of Olive Oil O/W Emulsions

The aim of this work was to study the physical properties and oxidative stability of model olive oil-in-water (o/w) emulsions stabilised by β-lactoglobulin (BLG), enriched with olive phenolic compounds, namely oleuropein, tyrosol and hydroxytyrosol, and added with maltodextrins (MD 7.5–9.9) in different concentrations to modify the viscosity of the continuous water phase. Emulsions were characterized for their viscosity, droplet size distribution, microstructure and interfacial protein coverage. The oxidative stability was monitored by means of hydroperoxides, hexanal and nonanal contents as indices of primary and secondary oxidation products, respectively. At high concentrations, MD increased significantly the viscosity of the emulsions; conversely, the addition of olive phenolic compounds did not show any significant effect on it. Both MD and phenolic compounds resulted to affect both the droplet size and the bigger to smaller particles ratio, with phenolic compounds generally improving the dispersion degree. A delay in the decomposition of hydroperoxides was observed as a consequence of MD addition, which also resulted to affect the efficiency of the phenolic compounds among the different systems. However, the highest protection towards oxidations was obtained when hydroxytyrosol was added. MD effect was related not only to the higher viscosity of the emulsions but also to complex interactions that occurred among the different components of the system.

Quantitation of Metals During the Extraction of Virgin Olive Oil from Olives Using ICP‐MS after Microwave‐assisted Acid Digestion

AbstractTrace metals such as Cu and Fe have negative effects on the oxidative stability of olive oils, and consequently, their concentrations are used as quality criterion. Also, maximum levels are established for heavy metals (As and Pb) in olive oils due to their high toxicity. Olive fruits can be contaminated with these metals from soil and air and from the use of pesticides or fertilizers, with the potential contamination of virgin olive oil (VOO) during its extraction from the fruits. This work presents two goals: (a) to optimize an analytical method for the determination of metals in raw olive fruits using an Abencor system; (b) to carry out a preliminary study of the fate of the metals during VOO extraction. The selected metals were quantified in raw olive fruits, and in the olive pomace and VOO obtained after their processing. The metal determination was performed by inductively coupled plasma‐mass spectrometry after microwave‐assisted acid digestion with HNO3/H2O2. The results showed that most of the metals (at least 90 %) present in the olive fruits were retained by the olive pomace, so obtaining high‐quality VOO from the point of view of its metal content.