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Olive leaves as by-products of olive farming are rich natural source of bioactive compounds with antioxidant properties. In this study, the efficiency of the natural maceration of fresh and steam blanched olive leaves in refined rapeseed oil was investigated, as well as the effect of degree of leaf fragmentation (whole, cut, ground) and maceration time on transfer of bioactive compounds (polyphenols) and pigments (chlorophylls) in oil. In oils obtained by maceration, changes of total phenolic compounds and total chlorophylls were determined spectrophotometrically. The effect of these oil preparation procedures on oil quality indicators was also investigated through free fatty acid content and spectrophotometric indices. The content of total phenols and chlorophylls increased in oils obtained by maceration of fresh and steam blanched olive leaves, and were in statistically significant correlation with leaf fragmentation degree. The highest content of total phenols was achieved in oils with whole fresh leaves (220.4 mg/kg) after seven days of maceration while the chlorophylls transfer to oils was the most efficient when ground steam blanched leaves were macerated for 28 days (79.10 mg/kg). Maceration of olive leaves slightly deteriorated the quality of refined rapeseed oil, equally in oils with fresh and steam blanched olive leaves. This simple preparation procedure can be efficiently used for enrichment of refined oils with natural antioxidants.

The aim of this study was to compare quality changes and compositional characteristics (fatty acids, total phenols, sensory profile) during 12 months storage of Buža and Istarska bjelica cv. virgin olive oils clarified by filtration at an industrial scale (filter press equipped with cellulose filters) and those clarified by natural sedimentation and decantation, as well as the influence of filtration of virgin olive oils on sterols and triterpene dialcohols composition. There were no significant differences in hydrolytic deterioration and sensory scores during the whole storage period between filtered and naturally sedimented oil samples. After 6 months, natural sedimentation was more favorable as regards delaying of oxidative deterioration, while filtration provided a more stable sensory profile. As regards total phenols the impact of the clarifying procedure was dependent on cultivar and fruit ripeness degree and it was more emphasized than the impact of storage. Filtration slightly affected the fatty acids composition, but natural sedimentation and decantation had no effect on it. Nevertheless, filtration did not compromise the confirmation of virgin olive oil authenticity according to the fatty acid composition, as well as according to sterols and triterpene dialcohols.

The interactive effects of ripening degree, malaxation duration and temperature on Oblica cv. (Olea europaea L.) virgin olive oil phenols, volatiles, and sensory quality were investigated. Olives were picked at three ripening degrees with International Olive Council indices of 0.68, 2.48 and 4.10, and processed by malaxation at 22 and 30 °C, and at both temperatures for 30 and 60 min. Ripening exhibited the strongest effect, and malaxation duration the weakest. Phenols were generally found to decrease during ripening; however 3,4-DHPEA-EDA and p-HPEA-EDA increased. Similar behaviour was observed for (E)-2-hexenal. Higher malaxation temperature induced an increase in particular important phenols and C6 alcohols, while C6 aldehydes mostly decreased. Interactions between the factors were established, mostly between ripening degree and malaxation temperature: the effect of the latter was most pronounced for ripe olives, especially for 3,4-DHPEA-EDA, p-HPEA-EDA and C6 volatiles. Sensory attributes were generally in agreement with the chemical composition.

Six monocultivar virgin olive oils (VOOs) produced from five autochthonous (Buza, Buza Puntoza, Istarska Bjelica, Porecka Rosulja, and Rosinjola) and one referent cultivar (Leccino), were investigated. The mass fractions of orthodiphenols (ORT) and tocopherols (TOC) were analysed by VIS spectroscopy and HPLC. The radical-scavenging capacity was evaluated by electron spin resonance spectroscopy (ESR) using galvinoxyl free radical and the DPPH test. Results revealed a high level of total TOC in VOOs of Buza Puntoza (243 mg kg(-1)) and Porecka Rosulja (325 mg kg-1). VOOs contained in 100 g from 79% (Istarska Bjelica) to 261% (Porecka Rosulja) of recommended daily allowance of a-tocopherol. The mass fraction of ORT in Istarska Bjelica and Rosinjola was > 250 mg kg-1 (on average 30-40% higher in comparison to other studied cultivars). Istarska Bjelica and Porecka Rosulja showed the highest antioxidant capacity in both methods of measurement. The highest capacity to inhibit protein carbonylation (PC) in response to oxidative stress (54-56%) was displayed by Buza Puntoza, Leccino, and Buza. High level of positive linear correlation between ORT mass fraction and radical-scavenging capacity measured by DPPH test (r=0.768), as well as strong negative correlation between PC inhibition and mass fraction of ORT (r=-0.697), were observed.

The influence of agronomical factors (two growing areas and four harvest periods) and storage conditions of virgin olive oils (room temperature, +4 and −20 °C) on tocopherols was investigated on two cultivars having significantly different tocopherol content (Oblica 269–443 mg/kg, Leccino 403–784 mg/kg). α-Tocopherol accounted for 97 % of total tocopherols and its content decreased during ripening of both cultivars. In a warmer growing area both cultivars gained a higher γ-tocopherol content while only Leccino showed a higher content of α-tocopherol. After 12 months of storage α-tocopherol content decreased by up to 27 %. Lower storage temperatures did not always contribute to the higher stability of α-tocopherol compared to room temperature.

The influence of the phenolic content in olive paste of cv. Buža increased by the addition of an aqueous solution of phenolic extract of freeze-dried olive pulp (cv. Istarska bjelica) on the final products of the lipoxygenase pathway in oil was studied. Increases by 12, 38, and 56% for ripe fruits (maturity index = 4.0) and by 38% for unripe fruits (maturity index = 1.2) were examined. Phenols in the olive paste were determined according to the HPLC method, whereas volatiles in oil were determined according to SPME-GC-MS. A significant negative effect on Z-3-hexenal and E-2-hexen-1-ol (Tukey’s test, p < 0.05) was found for ripe fruits (average decreases of 55 and 60%, respectively), but not for the unripe sample. Positive effects in both ripening levels were found for Z-3-hexenyl acetate (average increase of 68% for ripe and a double increase for unripe fruits) and total C5 compounds (average increase of 32% for ripe and an increase of 30% for unripe fruits).

The aim of this investigation was to determine the impact of fruit ripening on chemical and sensorial changes in monovarietal olive oils obtained from two important olive cultivars grown in Croatia, Buža and Crna. In Buža oils peroxide value, K232 and K270 increased during ripening, while no differences among three ripening stages in Crna oils were observed. Oils of both cultivars at the later ripening stages had higher free acidity level and lower sensory score followed by mild loss in almost all positive sensory characteristics. Total phenols and antioxidant capacity decreased in Buža oils during fruit ripening, while in Crna oils reached maximum level in purple stage and then progressively decreased in the black ripening stage. Oleic acid level slightly increased during ripening in both cultivar oils. Linoleic acid decreased in Buža oils obtained from black fruits while palmitic acid decreased in Crna oils during ripening. In both monovarietal oils chlorophyll and carotenoids concentrations decreased during ripening. The two cultivars had different course of total aldehydes, total esters and total ketones during ripening, while total alcohols were the highest in oils from purple ripening stage and then decreased as ripening progress. Practical applications: During the ripening, the chemical composition of olive fruit changes influencing the quality grade, oxidative stability, sensory characteristics and nutritional value of the obtained products. The cultivars characterized by a similar trend of ripening process could have different course of chemical and sensorial changes in oil during fruit ripening. Therefore, knowledge about these changes is important for determination of proper harvest time of single cultivar to achieve optimum of its potential regarding desirable characteristics of obtained oil.

The influence of filtration through a hydrophilic cotton layer on volatile compounds, sensory characteristics and colour of two monovarietal oils was investigated in this study. Volatiles were evaluated using headspace solid-phase microextraction-gas chromatography. After the filtration of Buža oils only a slight increase in total alcohols was noticed. In filtered Črna oils a significant decrease of total alcohols and slight changes in total aldehydes, total ketones and total C5 volatile compounds concentration were detected. No significant influence on the sensory scores of oils, but some slight changes in sensorial profiles were noted (slightly higher intensities of sensory characteristics apple and grass, and higher values of the lightness L(∗) in filtered samples). The results point to unequal filtration impact on different monovarietal oils and could be useful in developing targeted technologies for specific monovarietal oils quality improvement.

In order to evaluate the role of intrinsic characteristics of olive cultivars on dynamics of oil quality parameters changes related to the olive fruit fly (Bactrocera oleae (Gmelin)) attack, two specific olive cultivars were compared, Istarska bjelica and Buža. I. bjelica is characterised by late ripening, a lower flesh/stone mass ratio and higher oleic/linoleic ratio, the total phenols content and oil mass fraction compared to Buža. Oil samples were obtained at two harvesting dates, from fruit lots with 0, 25, 50, 75 and 100% of infestation degree, expressed by mass. Oil and water content in olive paste, as well as total phenols, fatty acids composition and standard chemical and sensorial oil quality parameters were determined. At equal maturity level, the cultivar with a higher oil (24 ± 1% vs. 16 ± 1%) and lower water content (54 ± 2% vs. 61 ± 4%) was more susceptible to hydrolytic degradation, while the one with the lower total phenols content (231 ± 32 vs. 575 ± 124 mg/kg) and oleic/linoleic fatty acid ratio (5.7 vs. 9.1) was more liable to oxidative deterioration of oil. Lower susceptibility to negative flavours formation could be related to the absence of ripening induced by fly attack and less favourable environment for larvae growth (higher total phenols content, lower water content and flesh/stone mass ratio). Practical applications: Understanding the impact of olive fly attack is the basis of scientific and practical interest in the production of olives and olive oil. Different intrinsic characteristics of olive cultivars could lead to different susceptibility to oil quality deterioration caused by olive fly attack, which opens a possibility to adjust and minimise pesticide treatments. Knowledge about this topic could contribute to the reduction of costs of olive pests control, as well as to the improvement of quality and food safety concept in olive oil production.

Three methods, most frequently used in hydrophilic phenols extraction from virgin olive oils (liquid–liquid, solid-phase with C18 and solid phase with diol-bound sorbents), were applied on virgin olive oils enriched with 2.0–10.0 mg/kg of phospholipids (granular de-oiled soy lecithin). Phospholipids addition significantly decreased the total phenols concentration determined colorimetrically. Liquid–liquid extraction showed the best repeatability and recovery, and the lowest decrease of total phenols extracted in the presence of phospholipids. Extraction rate declined with the increase of phospholipids concentration, but showed a kind of saturation behaviour. Addition of phospholipids (5 g/kg) to various commercial extra virgin olive oils resulted in a different degree of total phenols decrease (from 1% to 45%), probably because of different affinity of phospholipids toward different classes of phenolic compounds. During prolonged contact time between phenols and phospholipids (60-days storage), oxidation monitored by K270 and a decrease of total phenols concentration proceeded more rapidly in the presence of phospholipids.

In order to study the influence of some polar compounds, naturally present in virgin olive oils, on the volatiles release, the volatiles-free olive oil matrix was enriched with free fatty acids (FFA) (concentration range from 0.35 to 1.40 g/100 g), sterols (1.0 - 2.5 g/kg) and phospholipids (1.6 - 6.0 g/kg). Sixteen standards of virgin olive oil aroma compounds were dissolved in thus obtained olive oil matrices. Volatiles compounds were analyzed by headspace solid phase microextraction with DVB/CAR/PDMS fiber and gas chromatography with flame ionization detection. Evaluation of the data by statistical analysis revealed that FFA, sterols and phospholipids, in concentration ranges considered in this study, generally did not significantly influence the determination of virgin olive oil volatiles. The most important changes occurred in the release of the three alcohols (Z-2-penten-1-ol, 1-hexanol and E-3-hexen-1-ol) and 3-methylbutyl acetate which slightly decreased upon the increase of FFA concentration.

Immediately after extraction from olive fruits, virgin olive oil is a turbid juice with suspended particles of plant tissue and vegetable water droplets, which can deteriorate their quality by facilitating hydrolysis or oxidation of oil. Recently, filtration becomes a standard virgin olive oils production step with the aim of faster product finalisation and shelf-life extension. Filtration of olive oil could influence changes in antioxidant compounds such as phenols, tocopherols, and pigments, as well as volatile substances responsible for pleasant virgin olive oil aroma. In this work the changes of these minor compounds and fatty acids in relation to different filtration systems applied to virgin olive oil are discussed. In addition, influences of several agronomic and technological factors on composition of active compounds of virgin olive oil are reviewed. Moreover, analytical techniques for determination of virgin olive oil active components are pointed out.

This paper describes a method suitable for the analysis of diglycerides (DG) in cheese. The method, also suitable for other foods, is essentially based upon the solid-phase extraction (SPE) of DG followed by capillary gas chromatographic analysis with a polar stationary phase (TAP). SPE is applied to avoid the column overloading caused by triglycerides; however, SPE is able to catalyse isomerization from the 1,2-form to the 1,3-form. This introduces an error into the results, as the two forms have different origins and are produced at different stages of ripening. A comparison between the use of silica and diol phases was made and it was seen that no isomerization occurred when the diol phase was used. Repeatability and recovery trials were carried out and the coefficient of variation (relative standard error) of the former trial was approximately 10%. Finally, it is demonstrated that it is possible to re-use the SPE cartridge at least four times.

Seafood has been acknowledged as an integral part of a healthy diet, especially due to its polyunsaturated fatty acid content. The aim of this study was to investigate the contribution of canned oily fish to the daily fatty acid intake in the representative sample of Croatian adults. Consumption data were obtained through the National Food Consumption Survey, while the fatty acid profile of different canned products (tuna, sardine and mackerel) was determined using gas chromatography. The average canned fish consumption of 36.64 g/day was registered in only 4% of examinees. The analysed canned products highly varied in their n-3 fatty acids share. The n- 3/n-6 ratio ranged from 0.09 (canned tuna in oil) to 1.33 (canned tuna with vegetables). Judging by the average daily consumption and mass ratio of PUFAs in canned fish products, when consuming sardine in oil, Croatian consumers attain 130.3% of the recommended EPA + DHA intake ; when consuming tuna in oil, sardine with vegetables, mackerel in oil and tuna with vegetables, the resulting percentages are 60.4, 43.0, 25.9 and 3.8, respectively.