Effect of Agronomical Factors and Storage Conditions on the Tocopherol Content of Oblica and Leccino Virgin Olive Oils

Evolution of Extra Virgin Olive Oil Quality under Different Storage Conditions

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

Influence of Thermal Processing on Oil Contents, Bioactive Properties of Melon Seed and Oils

The oil content and the fatty acid composition of roasted and unroasted melon seed and oils were determined. The oil contents of roasted melon seeds changed between 26.4% (Type 12) and 38.7% (Type 4). In general, oil contents of roasted melon seeds were found higher than that of unroasted seeds that could be due to the evaporation of water during roasting processes which consequently lead to increased concentrations of other seed components including oils. Saturated fatty acid contents of unroasted melon seed samples change between 13.5% (Type 6) and 17.1% (Type 20). In addition, polyunsaturated fatty acids of unroasted melon seed oils ranged from 51.9% (Type 13) to 70.2% (Type 6). Palmitic acid contents of roasted seed oils varied between 7.8% (Type 5) and 15.1% (Type 17). In addition, the oleic acid contents ranged from 15.4% (Type 10) to 37.7% (Type17). Also, linoleic acid contents were found between 34.7% (Type 17) and 70.3% (Type 6). Saturated fatty acid contents of roasted melon seed oils ranged from 13.5% (Type 6) to 16.7% (Type 13). The major tocopherols in both roasted and unroasted melon seed oils were α-tocopherol, ɣ-tocopherol and δ-tocopherols. Melon seed oils are rich in linoleic, oleic acids and ɣ-tocopherol.

An evaluation of bioactive compounds, fatty acid composition and oil quality of chia (Salvia hispanica L.) seed roasted at different temperatures

The effect of roasting of chia seed at different temperatures (90, 120, 150 and 180 °C) on bioactive constituents in extracts and on the quality of oil was evaluated. At higher temperatures, crude protein and ash contents increased, whereas total phenolic, flavonoid, carotenoid, and antioxidant activities decreased. The predominant phenolic constituents were myrcetin, and rosmarinic, 3, 4-dihydroxybenzoic, caffeic, and gallic acids, which all decreased with increasing temperatures. Notably, myrcetin content ranged from 75.59 mg/100 g (at 100 °C) to 85.49 mg/100 g (for control). Tocopherols (ɣ and α type) were predominant nutrients and their levels ranged from 654.86 mg/100 g (at 180 °C) to 698.32 mg/100 g (for control). Concentrations of linolenic (59.84%), linoleic (20.57%), and oleic (10.09%) acids from unroasted chia seeds were higher than those from roasted ones. This study revealed that chia seeds should be heated at temperatures below or equal to 90 °C in order to preserve their nutrient profile.

Effect of sonication process of terebinth (Pistacia terebinthus L.) fruits on antioxidant activity, phenolic compounds, fatty acids and tocopherol contents

The current study investigated the impact of sonication process on antioxidant activity, phenolic compounds, total phenolic, total flavonoid, oil contents, fatty acids profile, and tocopherols of terebinth (Pistacia terebinthus) fruits. The highest antioxidant activity (87.32%), total phenolic (251.25 mg/100 g) and flavonoid (3413.72 mg/100 g) contents were observed in terebinth fruits sonicated for 30 min. The oil contents of terebinth increased from 38.93% (control) to 42.60% (sonicated for 15 min) after sonication process. The quercetin and catechin were the chief phenolic compounds in P. terebinthus extracts and their values were increased from 129.09 to 467.28 mg/100 g (quercetin) and from 5.58 to 21.33 mg/100 g (catechin) in fruits sonicated for 30 min. The major fatty acids of terebinth fruit oil were oleic (48.02-49.15%), linoleic (22.28-23.48%) and palmitic (22.10-23.67%) and sonication processes did not affect the quantities of these fatty acids. γ-Tocopherol was the most abundant isomer with the value of 63.95-122.03 mg/100 g in terebinth fruit oil. It could be concluded that pre-sonication for 30 min was more suitable for enhancing the antioxidants and phenolic compounds of P. terebinthus fruit.

Genotype-dependent regulation of vitamin E biosynthesis in olive fruits as revealed through metabolic and transcriptional profiles

Vitamin E is a general term used to describe a group of eight lipophilic compounds known as tocochromanols. These vitamin E variants are chemically categorised into two classes formed by α-, β-, γ- and δ- tocopherols and tocotrienols isoforms, respectively. The present study describes the concurrent regulation of genes and metabolites orchestrating vitamin E biosynthesis in olive drupes of five distinctive Greek olive cultivars. A combination of analytical, biochemical and molecular approaches was employed in order to carry out comparative analyses, including real-time RT-qPCR for gene expression levels and HPLC analysis of metabolite content. Findings indicated that tocochromanol levels and composition, oil content, gene expression levels as well as total antioxidant activity were highly dependent on cultivar and, to a lesser extent, on fruit developmental stage. Specifically, cultivars 'Kalokairida' and 'Lianolia Kerkyras' demonstrated the highest vitamin E content. The latter possessed high tocochromanol content combined with highest overall antioxidant activity in all developmental stages, concomitant with the up-regulation expression profile of HPPD. The genotypic imprint versus the temporal contribution to vitamin E levels, as well as the potential link to lipid peroxidation amelioration, are discussed.

Differentiation Between Unfiltered and Filtered Oblica and Leccino cv. Virgin Olive Oils

The quality parameters, a variety of microcomponents, and the sensory characteristics of Oblica and Leccino cv. virgin olive oils (VOOs) were evaluated before and after filtration process adopted in order to estimate the individual varietal compositional changes. The dynamics of the formation of hydrolytic and oxidative changes in unfiltered (UF) and filtered (F) oils was asses by comparing level of free fatty acids (FFA), peroxide value (PV), and spectrophotometric indices periodically during 1 year of oil storage. An analysis of phenolics, tocopherols, and fatty acids was determined by chromatographic (HPLC and GC) and spectrometric methods, oxidative stability by Rancimat method while sensory analyses of obtained olive oils were performed by a trained professional panel. Single monovarietal VOO loses phenols in different rate with the applied filtration. Total secoiridoids decreases significantly in "Oblica" VOOs while no changes in their concentrations were found between unfiltered and filtered "Leccino" oils. Intensity of desired sensory properties decreases with filtration. In "Leccino" VOOs decrease of oxidative stability was more pronounced. After 12 months of storage, filtered "Leccino" VOOs had significantly lower FFA values than observed for the unfiltered counterparts. Further, there were no significant changes in PV and K²⁷⁰ values between unfiltered and filtered oils of both studied varietal oils. Storage time influenced more studied quality parameters than filtration, during which PV of unfiltered oils faster deteriorate. The highest changes between stored and corresponding fresh samples were exhibited in unfiltered "Oblica" VOOs. PRACTICAL APPLICATION: Quality enhancement of olive oil is constantly being done professionally and scientifically. The information provided in this study can be used in the industry of olive oil for improve the phenolic content, oxidative stability, and the sensory quality of virgin olive oils. The findings of stability test could be guidelines for mindful leading of the oil finishing up to bottling.

Effects of Cold-Press and Soxhlet Extraction Systems on Antioxidant Activity, Total Phenol Contents, Fatty Acids, and Tocopherol Contents of Walnut Kernel Oils

In this study, physico-chemical properties, fatty acid composition, and tocopherol contents of several walnut kernel oils obtained through cold-press and Soxhlet extractions were investigated. The acidity, peroxide, and unsaponifiable matter of oil samples extracted in the Soxhlet system were found higher. Total phenol contents of the oils obtained in cold press and Soxhlet extraction systems were 121.9 mg GAE/100g (Kaman-2) and 154.6 mg GAE/ 100g (Büyükoba), and between 135.9 mg GAE/100g (Kaman-2) and 163.8 mg GAE/100g (Büyükoba), respectively (p < 0.05). In addition, antioxidant activity valuesof walnut oils obtained in cold press and Soxhlet extractions varied between 17.3% (Kaman-2) and 19.7% (Kaman-5), and between 18.4% (Kaman-2) and 23.8% (Büyükoba), respectively (p < 0.05). Linoleic acid contents of the oil samples extracted in cold-press varied between 55.19% (Kaman-5) and 56.71% (Kaman-2), while that extracted from Soxhlet extraction system varied between 54.47% (Kaman-2) and 55.93% (Büyükoba). ɣ-Tocopherol contents of walnut oils extracted in cold press and Soxhlet extraction ranged between 9.41 mg/100g (Büyükoba) and 10.83 mg/100g (Kaman-2), and 8.76 mg/100g (Kaman-5) and 9.33 mg/100g (Kaman-2), respectively, and were statistically significant (p < 0.05).

Influence of the feed pipe position of an industrial scale two-phase decanter on extraction efficiency and chemical-sensory characteristics of virgin olive oil

BACKGROUND

Nowadays, olive oil extraction is basically achieved by means of two-phase decanters, which allow a reduction of water consumption and the leaching of phenolic compounds. Despite this, most of the working settings derive from studies carried out on three-phase decanters. Hence, the aim of the present study was to assess the influence of two-phase decanter feed pipe position (FP) on the extraction efficiency and chemical-sensory characteristics of virgin olive oil. Three different positions were considered: at 825 mm (FP1), 610 mm (FP2) and 520 mm (FP3) from the outlet of the oily phase.

RESULTS

Position FP3 allowed the highest oil recovery (up to 10%), the lowest percentage of oil in the olive pomace and, in general, a regular trend in terms of oil extraction efficiency. However, the oily must that came out of the decanter was not completely clean in terms of residual content of solid sediment and water. The feeding position partially affected the profile of antioxidant compounds.

CONCLUSION

In two-phase decanters, loading the olive paste close to the outlet of the oily phase is recommended to increase the extraction efficiency without jeopardizing the chemical-sensory characteristics of virgin olive oil. © 2018 Society of Chemical Industry.

The Effect of Solvent Type and Roasting Processes on Physico-Chemical Properties of Tigernut (Cyperus esculentus L.) Tuber Oil

In this study, physico-chemical properties of raw and roasted tigernut oils extracted by two different solvents were determined. Peroxide values of raw and roasted tigernut oils extracted by petroleum ether and n-hexane solvents changed between 0.83 and 0.91 meqO₂/100g to 1.57 and 1.63 meqO₂/100g, respectively. While oleic acid contents of raw tigernut oils extracted by petroleum ether and n-hexane are determined as 66.83 and 67.47%, oleic acid contents of roasted tigernut oils extracted by petroleum ether and n-hexane were determined as 67.08 and 68.16%, respectively. The highest δ-tocopherol content was found in raw tigernut oil extracted by petroleum ether (54.91 mg/100g), while the lowest level is determined in roasted tigernut oil by n-hexane (50.77 mg/100g). As a result, the fatty acid profiles of roasted tigernut oil extracted by n-hexane were higher compared to results of raw tigernut oils extracted by petroleum ether (p < 0.05).

Pecan walnut (Carya illinoinensis (Wangenh.) K. Koch) oil quality and phenolic compounds as affected by microwave and conventional roasting

In this study, the effects of conventional and microwave roasting on phenolic compounds, free acidity, peroxide value, fatty acid composition and tocopherol content of pecan walnut kernel and oil was investigated. The oil content of pecan kernels was 73.78% for microwave oven roasted at 720 W and 73.56% for conventional oven roasted at 110 °C. The highest free fatty acid content (0.50%) and the lowest peroxide value (2.48 meq O2/kg) were observed during microwave roasting at 720 W. The fatty acid profiles and tocopherol contents of pecan kernel oils did not show significant differences compared to raw samples. Roasting process in microwave oven at 720 W caused the reduction of some phenolic compounds, while the content of gallic acid exhibited a significant increase.

The effect of drying temperatures on antioxidant activity, phenolic compounds, fatty acid composition and tocopherol contents in citrus seed and oils

In this study, the effect of drying temperature on antioxidant activity, phenolic compounds, fatty acid composition and tocopherol content of citrus seeds and oils were studied. Kinnow mandarin seed, dried at 60 °C, exhibited the highest antioxidant activity. Orlendo orange seed had the maximum total phenolic content and α-tocopherol content, with a value of 63.349 mg/100 g and 28.085 mg/g (control samples), respectively. The antioxidant activity of Orlendo orange seed (63.349%) was higher than seeds of Eureka lemon (55.819%) and Kinnow mandarin (28.015%), while the highest total phenolic content was found in seeds of Kinnow mandarin, followed by Orlendo orange and Eureka lemon (113.132). 1.2-Dihydroxybenzene (13.171), kaempferol (10.780), (+)-catechin (9.341) and isorhamnetin (7.592) in mg/100 g were the major phenolic compounds found in Kinnow mandarin. Among the unsaturated fatty acids, linoleic acid was the most abundant acid in all oils, which varied from 44.4% (dried at 80 °C) to 46.1% (dried at 70 °C), from 39.0% (dried at 60 °C) to 40.0% (dried at 70 °C). The total phenolic content, antioxidant activity and phenolic compounds of citrus seeds and tocopherol content of seed oils were significantly affected by drying process and varied depending on the drying temperature.

Effect of harvest time on physico-chemical properties and bioactive compounds of pulp and seeds of grape varieties

In this study, physicochemical properties and bioactive compounds of three grape varieties (Cardinal, Müşküle and Razaki) harvested at the three different harvest times (on time, one and two weeks earlier) were investigated. The highest antioxidant activity, total phenolic and flavonoid contents were observed in Razaki pulp and these were 82.854%, 127.422 mg/100 g, 3.873 mg/g, respectively. The contents of bioactive compounds in grape seeds were found higher than those in pulps. Similarly, seed of Razaki had higher antioxidant activity (91.267%) and total phenolic content (477.500 mg/100 g) when compared to results of other varieties. The key phenolic compounds of all grape variety and seeds were gallic acid, 3,4-dihydroxybenzoic acid, (+)-catechin ve 1,2-dihydroxybenzene. The oil content of grape seeds ranged from 8.50% (Razaki harvested one week ago) to 19.024% (Müşküle harvested one week ago). The main fatty acids of grapeseed oils were linoleic, oleic and palmitic acids. In addition, the oil of Razaki seeds was rich in tocopherols when compared to the other varieties.