125 research outputs found
The Chemistry of Olive Oil: an endless story
Because of their value, Olive oils, undergo to several attempts of adulteration and this improved the performances of analytical methods developed to check their authenticity. After the eve of the "Chemistry of indexes", the development of separation techniques greatly improved the knowledge of the composition of lipids; the earlier gas chromatographic separations of fatty acid, could last even more than 40 minutes and the evaluation of minor fatty acids were problematic, at Bologna University, their previous separation on silver nitrate silica gel TLC was applied in 1974–1975, in order to concentrate them and obtain a better chromatogram. The gas chromatographic evaluation of minor compounds was another interesting challenge, packed columns with apolar stationary phase, admit the separation of few peaks; in 1975, the use of a slightly more polar stationary phase (OV17) highlighted the presence of Δ-5-avenasterol in olive oils. 1981 is a milestone for olive oil analytical control: Regulation (CEE) 2568/91 made the use of capillary columns mandatory. Official analytical methods consider many parameters, enclosed sensory evaluation, that is not matter for chemists, however, chemists are moved by curiosity and several papers had been published on the relationship between the volatile compounds of head space of olive oil and sensory characteristics. Despite being one of the more studied food, olive oils' composition continues to give the chemists the possibility to discover new compounds, e.g. degradation products of sterols that leads to the standardization of the method for sterenes evaluation. From 1973 to nowadays, the laboratory performances greatly improved, nowadays it is possible to generate a huge number of data in a short time, then the problem is how to correctly interpretate them, surely chemometric and lipidomic greatly can help
Utjecaj skladištenja plodova masline u vrećama na kakvoću ulja i sastav hlapljivih sastojaka
The composition of olive oil volatile components depends on genetic factors, ripening grade of the fruit, fruit storage and processing conditions. Storage of olives in reticular or plastic bags is still a frequently used practice that has negative effects on oil quality, particularly on sensory characteristics. The changes of volatile compounds during this procedure were determined using headspace solid phase microextraction (HS-SPME). The method was optimised as regards sample conditioning and extraction time, and verified by testing the repeatability and linearity of the response. The main changes during fruit storage in bags are increase of methanol and ethanol concentration and decrease of 1-penten-3-one, trans-2-hexenal and cis-3-hexenyl acetate concentration. The changes in plastic bags are more evident and significant differences between the two types of storage are established.Sastav hlapljivih sastojaka maslinovog ulja ovisi o genetičkim faktorima, stupnju zrelosti plodova i njihovu skladištenju te uvjetima preradbe. Još uvijek se često primjenjuje skladištenje maslina u mrežastim ili plastičnim vrećama, što negativno utječe na kakvoću ulja, osobito na senzorska svojstva. Promjene hlapljivih sastojaka tijekom ovoga postupka utvrđene su primjenom mikroekstrakcije na čvrstoj fazi u natprostoru (HS-SPME). Metoda je optimirana s obzirom na kondicioniranje uzorka i vrijeme ekstrakcije, te provjerena utvrđivanjem ponovljivosti i linearnosti odgovora. Glavne su promjene tijekom skladištenja plodova u vrećama povećanje koncentracije metanola i etanola, te smanjenje koncentracije 1-penten-3-ona, trans-2-heksenala te cis-3-heksenil acetata. Promjene u plastičnim vrećama više su izražene, a uočene su i bitne razlike između dvaju načina skladištenja
Caratteristiche di qualit\ue0 e purezza degli oli d\u2019oliva tra necessit\ue0 di standardizzazione e variabilit\ue0 naturale
Abstract. The improvement of the agricultural surface
devoted to olive oil production, highlighted the
strong influence of environmental conditions on the oil
composition. In the meantime, the establishment of
shared rules and standard of composition is mandatory
to improve the worldwide trade of olive oils. Rules
are established as Regulations that means mandatory
rules (laws) within European Union, while outside UE,
the Trade Standard by International Olive Council is
the reference standard and at worldwide level, the
Codex Alimentarius (established by FAO-OMS) is the
World Trade Organization reference. The number of
members of these three levels of international organization
is different and an hard work is to find an
acceptable compromised between countries quite different
in terms of agricultural scenarios, environmental
conditions, economic conditions and social organization.
Standards relate to quality and purity characteristics,
this classification is very important because
while quality is a ranking parameter, purity is a cutting
limit, this means that it is necessary to be very careful
in admitting any exception in limits. The environmental
differences between \u201ctraditional\u201d geographic area
of olive cultivation, that\u2019s to say the Mediterranean
basin and new areas of cultivation, mainly located in
the South Hemisphere, in some cases strongly influence
the oil composition, even in some characteristics
whose limits are an important borderline to defend
olive oil purity. Nevertheless, it\u2019s an evidence that
some authentic olive oils exist , that for some parameters
exceed the established limits; the very hard issue
is that these parameters are purity parameters and
that the modification of a limit can open the door to
faked oils. Linolenic acid content is an important parameter
to highlight the admixtures with soybean oil,
however, in some areas, the content of linolenic acid of authent ic ol ive oi ls exceeded the Codex
Alimentarius limit; no agreement had been reached
between main producing countries and new producing
ones and nowadays the Codex Standard has no limit
for this acid. Campesterol and \u394-7 Stigmastenol, too,
are very useful to highlight the presence of several
seed oils (the former) and Compositae oils (the latter),
but some cultivar in some geographical areas where
the presence of olive in the agricultural landscape is
rather recent, present concentration of these sterols
higher than the established limit (respectively 4,0%
and 0,5%). In all these cases, the problem is not to
expel from the market some production of genuine
oils, in the meantime not leave any space to possible
frauds. A solution had been to build some so called
\u201cdecisional trees\u201d, that are based on the principle of
admit selected \u201canomalies\u201d for one limit, in the meantime
making the other more strictly, with the aim to
avoid any possibility that the derogation of one limit
can make faked oils not possible to b e distinguished
by authentic ones. In this review, some of these cases
will be described and critically discussed-
Biochemical and nutritional traits of sea bass (Dicentrachus labrax) from different rearing systems.
Farmed European sea bass (Dicentrarchus labrax), sampled from three different culture systems (intensive in sea-cages, intensive in land-based basins and extensive in lagoon and storage basins of salt-work), of the Northern, Central and Southern Italy, were analyzed with the aim to employ nutritional trait to describe and to distinguish the "origin" of the product. Lipid and fatty acid profile, strongly affected by the feeding history and environmental factors, responsible of the nu- tritional and perceived quality of fish product, are proposed as marker of origin
Microwave assisted saponification (MAS) followed by on-line liquid chromatography (LC)-gas chromatography (GC) for high-throughput and high-sensitivity determination of mineral oil in different cereal-based foodstuffs
A high throughput, high-sensitivity procedure, involving simultaneous microwave-assisted extraction (MAS) and unsaponifiable extraction, followed by on-line liquid chromatography (LC)-gas chromatography (GC), has been optimised for rapid and efficient extraction and analytical determination of mineral oil saturated hydrocarbons (MOSH) and mineral oil aromatic hydrocarbons (MOAH) in cereal-based products of different composition. MAS has the advantage of eliminating fat before LC-GC analysis, allowing an increase in the amount of sample extract injected, and hence in sensitivity. The proposed method gave practically quantitative recoveries and good repeatability. Among the different cereal-based products analysed (dry semolina and egg pasta, bread, biscuits, and cakes), egg pasta packed in direct contact with recycled paperboard had on average the highest total MOSH level (15.9mgkg(-1)), followed by cakes (10.4mgkg(-1)) and bread (7.5mgkg(-1)). About 50% of the pasta and bread samples and 20% of the biscuits and cake samples had detectable MOAH amounts. The highest concentrations were found in an egg pasta in direct contact with recycled paperboard (3.6mgkg(-1)) and in a milk bread (3.6mgkg(-1))
HOMOGENEITY OF COMPOSITION OF VIRGIN OLIVE OIL FROM WEST ISTRIA - AN EXAMPLE OF THE LECCINO VARIETY
New isobaric lignans from refined olive oils as quality markers for virgin olive oils.
Herein we describe the influence of olive oil refining processes on the lignan profile. The detection of new
isobaric lignans is suggested to reveal frauds in commercial extra-Virgin Olive Oils. We analyzed five
commercial olive oils by HPLC-DAD-TOF/MS to evaluate their lignan content and detected, for the first
time, some isobaric forms of natural (+)-pinoresinol and (+)-1-acetoxypinoresinol. Then we analyzed
partially and fully-refined oils from Italy, Tunisia and Spain. The isobaric forms occur only during the
bleaching step of the refining process and remain unaltered after the final deodorizing step. Molecular
dynamic simulation helped to identify the most probable chemical structures corresponding to these
new isobars with data in agreement with the chromatographic findings. The total lignan amounts in commercial
olive oils was close to 2 mg/L. Detection of these new lignans can be used as marker of undeclared
refining procedures in commercial extra-virgin and/or Virgin Olive Oils
Toward a definition of blueprint of virgin olive oil by comprehensive two-dimensional gas chromatography
Evaluation of hydrocarbon contaminants in olives and virgin olive oils from Tunisia
The present paper investigated on the presence of some hydrocarbon contaminants, namely polycyclic
aromatic hydrocarbons (PAHs), mineral oil hydrocarbons (MOH) comprising saturated (MOSH) and aromatic
(MOAH) compounds, and polyolefin oligomeric saturated hydrocarbons (POSH) in olives and
extra virgin olive oils from Tunisia. Olive fruits were collected in sites exposed to different environmental
contamination, and the oil extracted both by physical mean (using an Abencor extractor) and with
solvent (using microwave assisted extraction, MAE). Analytical determination was performed by SPE
cleanup on silica cartridge followed by spectrofluorometric detection, for PAH, and on-line HPLC-GC-FID
for MOH and POSH. Oils extracted from olives by physical mean, as well as extra virgin olive oils from the
market, had PAH levels never exceeding the EU legal limits. All olive samples showed similar MOSH
profiles, but not clear correlation between the variable contamination levels and considered sources of
contamination, was evidenced. The average MOSH content in oil extracted from olives by solvent
(11.1 mg/kg) was about four time higher than in oil extracted by physical mean (2.6 mg/kg). MOSH in
extra virgin oil from the market ranged from 10.3 to 38.0 mg/kg, while MOAH were not detected. The
higher MOSH levels found in oils from the market evidenced an important contribution due to oil
processing and/or packaging. Two of the samples were clearly contaminated with polyolefin oligomeric
hydrocarbons (POSH) migrated from the plastic cap
Molecularly Imprinted Polymer as Selective Sorbent for the Extraction of Zearalenone in Edible Vegetable Oils
A method based on the selective extraction of zearalenone (ZON) from edible vegetable oils using molecularly imprinted polymer (MIP) has been developed and validated. Ultra-high-pressure liquid chromatography coupled with a fluorescence detection system was employed for the detection of zearalenone. The method was applied to the analysis of zearalenone in maize oil samples spiked at four concentration levels within the maximum permitted amount specified by the European Commission Regulation (EC) No. 1126/2007. As a result, the proposed methodology provided high recoveries (>72%) with good linearity (R2 > 0.999) in the range of 10-2000 μg/kg and a repeatability relative standard deviation below 1.8%. These findings meet the analytical performance criteria specified by the European Commission Regulation No. 401/2006 and reveal that the proposed methodology can be successfully applied for monitoring zearalenone at trace levels in different edible vegetable oils. A comparison of MIP behavior with the ones of QuEChERS and liquid-liquid extraction was also performed, showing higher extraction rates and precision of MIP. Finally, the evolution of ZON contamination during the maize oil refining process was also investigated, demonstrating how the process is unable to completely remove (60%) ZON from oil samples
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