Rancimat Induction Time Research Articles

Antioxidant potential of olive leaf (<i>Olea europaea</i> L.) sustainable extracts evaluated <i>in vitro</i> and minced beef meat

In this work, by using water steam only, two antioxidant extracts were obtained from olive leaves (Olea europaea L.), a by-product of olive oil chain. Olive leaf extracts (OLEs) were tested as such (water extract: WE) and partially purified with ethyl acetate (ethyl acetate [EA] extract). Total phenols were 7.4 mg/mL and 3.8 mg/mL in WE and EA final solutions, respectively, evidencing a different composition by high-performance liquid chromatography analysis. Both extracts were evaluated in vitro in comparison to pure hydroxytyrosol (Hy). A 2,2-diphenyl-1-picrylhydrazyl (DPPH) EC50 of 57.6, 76.5, and 39.7 µg/mL and a ferric reducing antioxidant power EC50 of 84.8, 69.9, 41.2 µg/mL were determined for WE, EA, and Hy solution, respectively. The Rancimat induction time determined at 120°C in a lard sample with 200-ppm total phenol equivalent addition of WE, EA, and Hy was 8.92 h, 12.74 h, and 7.27 h, respectively (vs. 2.24 h for lard only). Extracts were added at the same dose (200 ppm) to minced beef patties that were put in closed containers under controlled air headspace composition (NA, natural air; HOA, modified air with 80% O2; and 20% N2) and stored at 4°C up to 10 days. Extracts showed significant effectiveness in contrasting decrease of O2 level in containers as well as pH and color changes of patties. A significant increase (expressed as mg of malondialdehyde MDA/kg; thiobarbituric acid-reactive substance (TBARS) assay was conducted in control samples at an interval of 0–10 days (from 0.52 to 0.78 mg of MDA/kg in NA samples; and from 0.55 to 1.31 mg of MDA/kg in HOA samples), while minimal changes were observed in treated samples. These findings suggest a potential use of OLEs for maintaining quality and oxidative stability of beef patties during storage.

Improving the oxidation stability of high-oleic sunflower oil with composite antioxidants

This study aimed to search for the optimum antioxidant mixture for improvement of the stability of high-oleic sunflower oil. Seven antioxidants including vitamin E, phytic acid, antioxidant of bamboo leaves, rosemary extract, tea polyphenols, ascorbyl palmitate (AP) as well as tea polyphenol palmitate (TPP) were used. Peroxide value, free radicals and Rancimat induction time results all proved that TPP was the best single antioxidant. Therefore, TPP was selected to mix with other antioxidants to form composite antioxidants. The combination of TPP and AP revealed the best antioxidant efficiency among the composite antioxidants comprised of two and three constituents in the oil. By optimizing the mixture proportions, the best antioxidant activity could be achieved when combining 480 mg/kg TPP with 40 mg/kg AP. The high-oleic sunflower oil sample (containing 480 mg/kg TPP and 40 mg/kg AP) had 1.96-fold longer shelf life (prediction by Rancimat method) compared with the blank sample.

Effects of different antioxidants and their combinations on the oxidative stability of DHA algae oil and walnut oil.

Through monitoring Rancimat induction time (RIT), peroxide value (POV), and thiobarbituric acid‐reactive substances (TBARS) of docosahexaenoic acid (DHA) algae oil and walnut oil during accelerated storage, the effects of the single and the combinations of seven kinds of antioxidants involving ascorbyl palmitate (AP), phytic acid (PA), vitamin E (VE), antioxidant of bamboo leaves (AOB), rosemary extract, tea polyphenols (TP), and tea polyphenol palmitate (TPP) against lipid oxidation were evaluated. RIT, POV, and TBARS results showed that the DHA algae oil sample containing 600 mg/kg TPP revealed the strongest stability and the walnut oil sample containing 450 mg/kg TPP and 100 mg/kg TP revealed the strongest stability. Then, the shelf lives of two oils were predicted from the extrapolation of the linear regression model between Log RIT and temperature. Our results indicated that the optimal antioxidant could prolong the shelf lives of DHA algae oil and walnut oil by 2.31‐ and 7.74‐fold, respectively.

Exceptional long-term durability of Coratina monovarietal extra virgin olive oil evaluated through chemical parameters and oxidative stability test

Coratina is a very popular olive cultivar, native of the Apulian region (Italy), but today worldwide cultivated and appreciated. In the present study, durability of Coratina monovarietal extra virgin olive oils (CMOO), produced in the Molise region (Southern Italy), was investigated up to 6-years storage in metal tin cans, under room temperature and darkness. Durability was considered the storage time in which an oil remained food grade. Yearly, the free fatty acids, peroxide value, K232 and K270 indices, fatty acid composition, diacylglycerols, phenolic profile and Rancimat induction time at 130 °C were determined on the oil. Free fatty acids and peroxide value increased linearly over time but never surpassing the European limits set for the EVOO category. Conversely, K232 and K270 exceeded the EVOO limits after five and four years, respectively. A linear decrease of phenolic compounds was observed with direct effect on the oil oxidative stability measured by Rancimat test. In conclusion, despite some signs of aging, the CMOO highlighted a remarkable long durability being food-grade up to 6-years.

Effects of gallic acid alkyl esters and their combinations with other antioxidants on oxidative stability of DHA algae oil

The most effective composite antioxidants for DHA algae oil were optimized by combining the selected gallic acid (GA) alkyl ester with other commonly used antioxidants. Results of Rancimat induction time, peroxide value, thiobarbituric acid-reactive substances, and free radical generation indicated that octyl gallate (OG) was the best one in DHA algae oil among GA alkyl esters with various chain lengths. Therefore, OG was used to combine other antioxidants (antioxidant of bamboo leaves, rosemary extract, tea polyphenols, tea polyphenol palmitate (TPP), ascorbyl palmitate, vitamin E, phytic acid and phospholipid) for further improving the oxidative stability of DHA algae oil. The combination of OG + TPP showed the best antioxidant effect among the composite antioxidants of two and three components. Through optimization of mixture ratio, the combination of 53.20 mg/kg OG + 360 mg/kg TPP demonstrated the best antioxidant capacity, which prolonged the shelf life of DHA algae oil by 4.24 folds.

Inhibitory Activity on the Formation of Reactive Carbonyl Species in Edible Oil by Synthetic Polyphenol Antioxidants.

Food lipids play an important role in food quality, and their attributes contribute to texture, flavor, and nutrition. However, high-temperature processing leads to lipid peroxidation, degradation, and the formation of reactive carbonyl species (RCS), such as acrolein (ACR), glyoxal (GO), and methylglyoxal (MGO). We investigated the changes in the peroxidation value (POV), Rancimat induction time, formation and total amount of RCS, and inhibitory effects of synthetic polyphenol antioxidants on ACR/GO/MGO in plant oils during heating processing through an accelerated oxidation test using Rancimat. With increasing temperature and heating time, the amounts of ACR, GO, and MGO in oil increased and the level of ACR was about several times higher than that of GO and MGO. We also found that some amounts of ACR, GO, and MGO were produced at the initial stage before reaching the peak value of POV, even before oil oxidative rancidity, and the common antioxidant butyl hydroxyanisole (BHA)/butylated hydroxytoluene (BHT) could not remove them once they were generated. This is first time to purify PG-ACR-MGO and elucidate the structure based on analysis of their high resolution mass spectrometry and 1H, 13C, and two-dimensional nuclear magnetic resonance. We further found that PG rather than BHT and BHA efficiently trapped ACR, OG, and MGO to form adducts in oil and roasted beef burgers with corn oil. Additionally, after incubation at 80 °C, the trapping order of PG was as follows: ACR, MGO, and GO, and the adduct of PG-ACR was formed within 1 min; after 10 min, PG-MGO was generated; and three adducts formed at 15 min. However, PG could not trap ACR, GO, or MGO to form adducts at room temperature. This study provided novel knowledge to advance our understanding of the ability of synthetic polyphenol antioxidants to scavenge RCS simultaneously, such as ACR, MGO, and GO. Our findings demonstrated that PG, as an inhibitor of RCS, is suitable for medium- and high-temperature food processing but not for normal-temperature storage.

Improving the oxidative stability and lengthening the shelf life of DHA algae oil with composite antioxidants

Based on various antioxidant mechanisms, four kinds of antioxidants including ascorbyl palmitate (AP), vitamin E (VE), phytic acid (PA) and one of the polyphenols (antioxidant of bamboo leaves, tea polyphenol palmitate or tea polyphenols (TP)) were used in combination to improve oxidative stability of docosahexaenoic acid (DHA) algae oil. To achieve the best effect, the formulations and mixture ratios of the antioxidant combinations were optimized. The effects were monitored by peroxide value, thiobarbituric acid-reactive substances, acid value, free radicals, Rancimat induction time and fatty acid composition of DHA algae oil undergoing accelerated storage. Finally, the DHA algae oil containing 80 mg/kg AP, 80 mg/kg VE, 40 mg/kg PA and 80 mg/kg TP had the highest oxidative stability. Furthermore, the shelf life of DHA algae oil containing the optimum composite antioxidant was predicted by using accelerated shelf life testing coupled with Arrhenius model, which was 3.80-fold longer than the control sample.

Improving oxidative stability of flaxseed oil with a mixture of antioxidants

The optimum combination of antioxidants used for stabilization of flaxseed oil and extension of its shelf life was examined. To achieve this goal, based on different antioxidant mechanisms, a combination of four types of antioxidants including tocopherol, ascorbyl palmitate (AP), phytic acid (PA), and a source of polyphenol (antioxidant of bamboo leaves (AOB), rosemary extract (RE), tea polyphenols extract (TP), and tea polyphenol palmitate (TPP)) were added to flaxseed oil. The effects were monitored using peroxide value (POV), thiobarbituric acid‐reactive substances (TBARS), free radicals, and Rancimat induction time (RIT) of flaxseed oil during accelerated storage. Flaxseed oil containing 80 mg/kg tocopherol, 40 mg/kg AP, 40 mg/kg PA, and 240 mg/kg TPP was found to be more stable to oxidation than other samples and had 3.22‐fold longer shelf life than that of the control flaxseed oil. PRACTICAL APPLICATIONS: Due to its high concentration of alpha‐linolenic acid, flaxseed oil is prone to oxidation. To improve the oxidative stability of flaxseed oil and prolonging its shelf life, the optimum formulation and ratio of mixtures of antioxidants with different antioxidant mechanisms were studied. Our results indicated that the flaxseed oil containing 80 mg/kg tocopherol, 40 mg/kg AP, 40 mg/kg PA, and 240 mg/kg TPP was very stable to oxidation. And the shelf life of the flaxseed oil containing this optimum mixture of antioxidants was 3.22‐fold longer than that of the control flaxseed oil. Therefore, adding the optimum mixture of antioxidants will help to produce the flaxseed oil products with better oxidative stability for commercial development.

Date seed oil as a potential natural additive to improve oxidative stability of edible vegetable oils

Scientists warn against the dangers of frying food in oil as it release toxic chemicals linked to cancer and heart disease. The negative effects of synthetic antioxidants lead to searching for a substitute with natural recourses. In the present study, fruits of three date palm cultivars; 'Hayani', 'Sewi' and 'Sakouti', were collected at mature stage and date seeds were used for oil extraction. Chemical properties of the oil as well as rancimate measurements were measured to determine the oxidative stability of the oil. Different levels (5, 10. 15 %) of date seed oil were added to crude soybean oil and the oxidative stability for the mixer were then compared to the commercial soybean oil with BHT additive. Pit powder oil content ranged from 8.2-10.6.'Sewi' had the highest total phenols content of phenolic compounds that 183.92 mg among cultivars, while carotenoids content were varied (33.5- 88.5 mg/kg).The fatty acid compositions of all the cultivars were very similar. Rancimat measurements for all cultivars' oil were higher than that of crude soybean oil. Date seed oil addition at different level to soybean crude oil increased the rancimat induction time. Treatment of 'Sewi' oil at 15 % was the best treatment among cultivars and was higher than that of the synthetic BHT effect. The results suggested that the seeds from the examined date cultivars as by product are good source of oil with high quality that may efficiency used as a natural additive to promote the oxidative stability of other vegetable oil.

Improved oxidative stability of peanut oil through addition of finger millet (Eleusine coracana) seed coat polyphenols

AbstractThe effect of polyphenols from finger millet seed coat (FMSC) on the oxidative stability of refined peanut oil (RPO) and unrefined peanut oil (UPO), at different concentrations and storage conditions was compared with butylated hydroxytoluene (BHT). A significant dose‐dependent reduction of oxidation in RPO compared with UPO was observed. FMSC polyphenols at 800 ppm inhibited oxidation equivalent to BHT (200 ppm), while at 1000 ppm, FMSC effectively reduced the peroxide value (5.1 ± 0.3 and 9.5 ± 0.5 meq/kg oil), acid value (0.97 ± 0.3 and 1.16 ± 0.4 KOH/g), and Thiobarbituric acid reactive species (TBARS) (18.08 ± 0.39 and 20.32 ± 0.56 mg MDA/kg) in RPO and UPO, respectively, during regular storage (RS; 28 ± 5°C, 7 weeks). Oxidative deterioration was higher in terms of all parameters in the oils during accelerated conditions (AS; 65 ± 5°C, 6 days). The Rancimat induction time confirmed the stability of both RPO and UPO in the presence of polyphenols. Regular storage up to 7 weeks and accelerated storage (AS) up to 3rd day (equivalent to 3 months) were achieved with FMSC polyphenols (1,000 ppm), confirming its potential as a natural antioxidant in vegetable oils.Practical applicationsPeanut oil contains high levels of PUFA that are susceptible to lipid oxidation leading to rancidity and off flavors. The food industry relies largely on synthetic antioxidants such as butylated hydroxytoluene (BHT), butylated hydroquinone (BHQ) and tert‐butyl hydro quinine (TBHQ) to inhibit deterioration caused by fats; however synthetic compounds have shown toxic effects. The study demonstrates the ability of finger millet polyphenols in delaying oxidation in both refined and unrefined peanut oils. Millet polyphenols as potential antioxidants in lipid food systems have the added advantage of providing food safety while maintain quality.

Solubility and Antioxidant Potential of a Pyrogallol Derivative for Biodiesel Additive.

Biodiesel is a renewable plant-based fuel as an alternative for fossil diesel fuel which has many advantages. However, its high content of unsaturated fatty acid causes an oxidation instability during storage. Numerous additives have been used and developed to overcome this problem such as the application of phenolic compound-based antioxidants. Pyrogallol is reported to be one of the best phenolic antioxidants for biodiesel. Unfortunately, pyrogallol has a low solubility in oil solution. In this research, pyrogallol solubility is increased by preparing a pyrogallol derivative through a reaction between pyrogallol and methyl linoleate in the presence of radical 2,2-diphenyl-1-picrylhydrazyl (DPPH). The spectrophotometric method was used for solubility test. Antioxidant potential was examined using acid value determination during a four-week storage period as well as the Rancimat test to see its performance under accelerated oxidation conditions. The reaction produced a molecule which has a molecular weight of 418 g/mol, representing pyrogallol derivative which has a new C–O covalent bond with methyl linoleate. The result was confirmed by using nuclear magnetic resonance (1H-NMR, 13C-NMR, and 2D-HMQC) resulting in a molecular structure of methyl (10E,12E)-9-(2,6-dihydroxyphenoxy)octadeca-10,12-dienoate and its isomer methyl (9E,11E)-13-(2,6-dihydroxyphenoxy)octadeca-9,11-dienoate with a yield of 12.86% and selectivity of 21.05% on the basis of pyrogallol. Compared to pyrogallol, tert-butylhydroquinone (TBHQ), and gallic acid, the pyrogallol derivative has the highest solubility and acid value stability in palm oil biodiesel. The Rancimat induction time (IP) result of the pyrogallol derivative is higher than the biodiesel and is above the accelerated oxidation test American Society for Testing and Materials (ASTM) D 6751 standard.

Extra virgin olive oil jam enriched with cocoa bean husk extract rich in theobromine and phenols.

Cocoa bean husk extract (CBHE) was obtained by thermal treatment at 170 °C for 30 min. The CBHE was added to a virgin olive oil jam in a freeze-dried form or encapsulated. Phenols, theobromine, and antioxidant activity were determined over 28 days in both jams and compared to a control jam. Total phenols, epicatechin, and theobromine were higher in the water fraction of the jam with non-encapsulated extract (J-CBHE) at day 28: 1140, 19.14 and 70 ppm, respectively. For the oil fraction of J-CBHE, total phenols, epicatechin, and theobromine contents were 120, 2.54, and 0.13 ppm at day 28, respectively. The oil content in jam with the non-encapsulated extract showed the best Rancimat induction time, with a 32% increase compared to the control, keeping for longer without becoming rancid. Nevertheless, the jam with encapsulated extract showed the best retention of bioactive compounds during the storage time.

Design of microparticles of chia seed oil by using the electrostatic layer-by-layer deposition technique

This study deals with the physicochemical characterization of powdered chia oil microparticles produced from mono and bi-layered emulsions using modified sunflower lecithins (Deoiled (DL); Phosphatidylcholine-enriched fraction (PC)), chitosan, and maltodextrin as wall materials. The powders were stored (20 ± 2 °C, RH 33%, 120d) and characterized by their moisture content, aw, ω-3 content (1H NMR), microencapsulation efficiency of oil (%ME) and ω-3 PUFAs (%MEω-3), microstructure, dispersibility, color, and oxidative stability (Rancimat induction time (ti); Peroxide value (PV)). The %ME were > 84% and %MEω-3 > 89% in all cases, recording systems with DL higher values than those with PC. The bi-layered systems presented higher ti, lower PV and higher %remaining ω-3 than the monolayer ones and the bulk oil. Bi-layered microparticles with modified sunflower lecithins were efficient to protect chia oil against oxidative deterioration, being suitable delivery systems of ω-3 fatty acids from this oil for functional food development.

Oxidative stability and the chemical composition of market cold‐pressed linseed oil

Oxidative stability and minor components of market linseed oils were evaluated. The oils were investigated for their primary and secondary oxidation products, fatty acid composition and pigment content, and samples were also examined for their scavenging of 1, 1‐ diphenyl‐2‐picrylhydrazyl (DPPH) and total phenolic content. Rancimat and pressure differential scanning calorimetry were used to assess oxidative stability. The analysed oils were of good quality, meeting the requirements of the Codex Alimentarius standard. Linseed oils were characterised by 45–65% content of α‐linolenic acid. The TEAC equivalent of linseed oils ranged from 1.25 to 1.42 mM of Trolox kg−1 oil, and FAE ranged from 60.25 to 115.12 mg of ferulic acid 100 g−1 oil. The correlation between linseed oil oxidative stability as measured by the Rancimat and PDSC methods was low (r = 0.55). Based on the obtained results of oxidative stability and the content of chemical compounds, principal components analysis was conducted. PCA indicated that none of the chemical compounds correlated strongly with the oxidative stability of linseed oils as determined by the Rancimat method. However, in the case of the PDSC method, the content of primary and secondary products of oxidation had the strongest impact on the oxidative stability of linseed oils. The correlation coefficients describing the impact of different chemical compounds on induction time using the Rancimat and PDSC tests were between −0.43 to 0.45 and −0.82 to 0.72, respectively.Practical applications: The results show that linseed oils available on the market were of differing but good quality. Results of oxidative stability tests demonstrate that Rancimat and pressure differential scanning calorimetry (PDSC) methods should not be used interchangeably for assessing linseed oil oxidative stability (r = 0.55). The initial degree of oxidation had the greatest impact on the oxidative stability of linseed oil, but none of the measured quality parameters showed a high correlation with the Rancimat induction time. Principal component analysis verified the designated correlations between induction times in the Rancimat and PDSC tests and quality features. PCA also confirmed differences between the examined linseed oils.Market linseed oils are examined to their oxidative stability using Rancimat and pressure differential scanning calorimetry, and their chemical composition. The influence of selected discriminants on the oxidative stability of linseed oil is determined.

Phytochemistry and Agro-Industrial Potential of Native Oilseeds from West Africa: African Grape (Lannea microcarpa), Marula (Sclerocarya birrea), and Butter Tree (Pentadesma butyracea)

Ethnobotanical investigations on local oilseed species in Burkina Faso revealed that oils from tree oilseeds are frequently used for food, cosmetics and traditional medicine by local people. To test the bio-preservative capacity, the effect of the oilseed extracts on the stabilization of Shea butter was evaluated. Levels of bioactive phyto-components were evaluated through several methods. Some aspects of the quality of oilcakes were evaluated based on their inhibitory capacity on the endogenous digestive enzymes of cattle. For fat stabilizing quality, the extract from Lannea microcarpa Engl. & K. Krause has showed the largest increase (91.47%) in the Rancimat induction time (TIR) of Shea butter. Using DPPH and FRAP methods for prevention or scavenging of free radicals, the results evidenced the highest activity with extracts of L. microcarpa. With respect to the feed quality of the oilcakes, the IC50 obtained with α-amylase and trypsin have showed that the ethanolic extracts of Pentadesma butyracea Sabine (1824) is less toxic for cattle. These results suggest that phenolic compounds extracted from these native oilseeds, especially those of Lannea microcarpa, can be used as biological antioxidants for bio-preservation of edible fats. In addition, the by-products of the oil-extraction can be valorized as nontoxic and protein-rich oilcakes for livestock feed.

New formulations of sunflower based bio-lubricants with high oleic acid content – VOSOLUB project

VOSOLUB project is a demonstration project supported by Executive Agency for Small and Medium-sized Enterprises (EASME) that aims at testing under real operating conditions new formulations of sunflower-based biolubricants with high oleic acid content. These biolubricant formulations (including hydraulic fluids, greases, and neat oil metal-working fluids) will be tested in three European demonstrating sites. Their technical performance will be evaluated and compared to corresponding mineral lubricants ones. In order to cover the demand for the sunflower base oil, a European SMEs network will be established to ensure the supply of the base at a competitive market price. Results presented concerns the base oil quality confirmed to be in accordance with the specification required, in particular on Free Fatty acid content, Phosphorus content, rancimat induction time and oleic acid content (ITERG). The oil characteristics specific for lubricant application analyzed by BfB Oil Research under normalized methods, match with lubricant specifications requirement such as viscosity, cold & hot properties, surface properties, anti-oxidant properties and thermal stability, anti-wear and EP properties, anti-corrosion properties Performance of the new biolubricant have been assessed by formulators and TEKNIKER First results on the use of new lubricant on real condition for rail Grease (produced by RS CLARE and tested with Sheffield Supertram), Hydraulic oil (produced by BRUGAROLAS) and cutting oil (produced by MOTUL TECH and tested with innovative machining, turning) are described.

Long-term storage stability of biodiesel and biodiesel blends

Longer-term storage stability of biodiesel and blends was studied in experiments simulating up to one year for 100% biodiesel (B100) and three years for blends. Aging was simulated by holding samples at 43°C to accelerate oxidation (ASTM D4625). Biodiesels were treated with antioxidants before and after aging, with continued aging after antioxidant treatment. Treating aged biodiesel was effective at restoring stability; however, antioxidant effectiveness was decreased relative to fresh biodiesel. Blends were prepared at B5 (5vol.%) and B20 (20vol.%) with biodiesel having either 3- or 6-hour Rancimat induction time and low or high polyunsaturated ester content with two diesels produced from hydrocracked or hydrotreated feedstocks. All B5s were stable for the entire storage time regardless of B100 induction time. B20s were unstable if prepared from high polyunsaturated ester biodiesel with a 3-hour induction time. Base diesel stability had considerable effect on blend stability. All but the lowest-stability B20s remained within specification, indicating that long-term storage of biodiesel blends is possible if the biodiesel has high oxidative stability and storage conditions are clean. Induction time decreases indicated loss of stability (consumption of antioxidant) prior to blend degradation; therefore, induction time monitoring is recommended for predicting quality changes during storage.

Determination of the oxidative stability of hazelnut oils by PDSC and Rancimat methods

The present study was conducted to determine the oxidative stability of hazelnut oil and compare it with more common and previously tested olive oil and rapeseed oil. The oxidative stability was determined by means of two independent methods, pressure differential scanning calorimetry (PDSC), and oxidative stability index (OSI) using TA Instruments DSC and Metrohm Rancimat equipment, respectively. Both the PDSC and Rancimat devices were set at five different isothermal temperatures in the range of 100–140 °C. The times to reach peak maximum (τ max) obtained from PDSC exotherms were statistically related with the Rancimat induction times (τ on) to obtain correlation coefficient >0.99 within linear relation. Based on the Arrhenius equation and activated complex theory, activation energies (E a), pre-exponential factors (Z), and specific rate constants (k) for studied oils oxidations were calculated. To the best of our knowledge, this is the first study dealing with oxidative stability of hazelnut oil using PDSC technique. According to the results obtained, PDSC seems to be useful and quick method for kinetic analysis of lipid oxidation in hazelnut oil.

Effect of containers on the quality of Chemlali olive oil during storage.

This study is undertaken to determine the storage stability of Chemlali extra-virgin olive oil (EVOO) in different containers such as clear and dark glass bottles, polyethylene (PE) and tin containers. The different oil samples were stored under light at room temperature. Quality parameters monitored during a 6-month-storage period included: acidity, peroxide value (PV), spectrophotometric indices (K232 and K270), chlorophyll and carotene pigments, fatty acids and sterol compositions, total phenols, Rancimat induction time as well as sensory evaluation. Tin containers and dark glass bottles recorded the lowest oxidation values. In addition, oil packed in tin containers and dark glass bottles showed better physicochemical and organoleptic characteristics than that stored in clear glass bottles and PE containers. A significant decrease (p < 0.05) in the antioxidant contents (carotenes, chlorophylls and total phenols) was observed in the oil stored in the clear glass bottles and PE containers. Such results proved that the storage of oil in tin containers and dark glass bottles appeared most adequate, and showed a gradual loss of quality during storage, especially in PE containers and clear glass bottles. This study has shown that the best packaging materials for the commercial packing of Chemlali extra-virgin olive oil are tin containers and dark glass bottles.

Heat-oxidation stability of palm oil blended with extra virgin olive oil

Rancimat induction time of palm oil (PO), several extra virgin olive oils (EV) and their binary blends have been determined at three different temperatures (120, 130 and 140°C). Analytical composition and oxidation stability of PO/EV blends were found to be a linear combination of the oil partners. Induction time of pure PO was always higher than those of EV oils and blends, in which induction time increased proportionally with the percentage of PO. However, induction time of 80% PO blend was similar to that of pure PO. Fatty acid composition appeared to be the most important factor affecting heat-oxidation stability and a saturated/unsaturated ratio near 1 was the optimally stable composition. Conversely, total phenols had a zero or negative role on the oxidative stability of the blends. Finally, in heat-oxidised oils significant losses of polyunsaturated fatty acids and formation of short-chain fatty acids were recorded.