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Evaluation of measurement uncertainty for the methods of analysis used to assess the characteristics of olive oil and olive-pomace oil from commission regulations EEC 2568/91 and EC 1989/2003
Erika Bešter, Milena Bučar-Miklavčič, Bojan Butinar, Vasilij Valenčič, 2007, izvirni znanstveni članek

Opis: Metrology has been present in our scientific knowledge for a long time, but mostly in physical measurements. Chemical measurement can be defined as a comparison of a quantity of measurand and relating it to a unit (e.g. mol/kg).When expressing a result of a measurement, the problem of traceability, validation and the measurement uncertainty (MU) evaluation must be challenged. It is well known that MU is a parameter associated with the result of a measurement that characterizes the dispersion of the values that could reasonably be attributed to the measurand. The EEC document 2568/91 with its annexes gives the methods of analysis to assess the characteristics of olive oils and olive-pomace oils with given limits. The EC document 1989/2003 gives the scheme, the algorithm, the pathway, the decision tree to differentiate between various types of olive oils using the particular determinations based on limits. The major lack of these EC methods is the non-existence of validation parameters, which are crucial in determining the MU (and in accreditation of a laboratory). There are several ways of evaluating (better term than calculating) the MU: with model equation, with use of a certified reference material (CRM) and with participation in a proficiency testing (PT) scheme. MU for a method of analysis is inherent to a laboratory and can serve as a tool for 'measuring' the quality of a laboratory. Unfortunately, there are practically no CRM's in the olive oil testing field. The only way to achieve a usable MU is through participation in PT schemes.
Najdeno v: osebi
Ključne besede: CRM, EEC 2568/91, EC 1989/2003, metrology, olive oil, PT scheme
Objavljeno: 10.07.2015; Ogledov: 1782; Prenosov: 15
URL Polno besedilo (0,00 KB)

Evaluation of the acidity in samples of virgin olive oil for the 1995-2005 period and correlation between the collected data and the performed sensory analysis
Erika Bešter, Milena Bučar-Miklavčič, Bojan Butinar, Vasilij Valenčič, 2007, izvirni znanstveni članek

Opis: The acidity and organoleptic characteristics of virgin olive oil produced in Slovenian Istra were studied. The acidity of 4,871 samples of virgin olive oils was determined for the 1995-2005 period. 135 samples produced in crop year 2002/2003 with acidity below 0.2% (w/w) and 291 samples of crop year 2005/2006 were sensory evaluated. According to sensory evaluation in crop year 2002/2003, 128 out of 135 samples were classified as extra virgin olive oils, while 7 samples did not reach the specified requirements. In crop year 2005/2006, it was established that 71.5% of the analysed samples complied with extra virgin category, 24.4% with virgin and 4.1% with lampante. Time of harvest, storage conditions before processing, and time from picking to processing all influenced the oil quality, whereas olive cultivars did not. Chemical and sensory analyses were performed according to the Commission Regulation (EEC) No 2568/91 and added annexes.
Najdeno v: osebi
Ključne besede: olive oil acidity, grading of oil, harvest, storage, processing, sensory analysis
Objavljeno: 10.07.2015; Ogledov: 1991; Prenosov: 10
URL Polno besedilo (0,00 KB)

Karotenoidi v oljčnem olju
Erika Bešter, Milena Bučar-Miklavčič, Vasilij Valenčič, Bojan Butinar, 2007, pregledni znanstveni članek

Opis: The pigments profile of virgin olive oil is determined by the pigments initially present in the fruits and their derivatives formed during the extraction process. The presence of other carotenoids or chlorophyll pigments at levels other than that associated with the extraction process indicate that oil has been adulterated or the extraction process was incorrect. The yellow pigments in olive oil are carotenoids and the green pigments are chlorophyll pigments. The amount of carotenoids in oil depends on variety, maturation index, treating of olive fruits before extraction, extraction process, and oil treating. Carotenes as well as xantophylls were identified in virgin olive oils. Lutein is usually the predominating compound in the carotenoid fraction of pigments, followed by B-carotene. The rest of carotenoid fraction are minor xantophylls, such as 5,6-epoxides, 5,8-epoxides or furanoids, and xantophyll esters. Cis-isomeres are also formed during the extraction process. The vitamin activity of cis-isomeres is lower as the activity of trans-isomeres. Pigment profile of olive oil is a useful tool for variety classification and authenticity determination. Carotenoids can act as antioxidants or prooxidants. Their antioxidant/prooxidant activity depend on concentration, solvent, and free radicals structure, presence of other antioxidants, metals and oxygen. The antioxidant activity of carotenoids has not been satisfactory explained as yet. There are three possible mechanisms of carotenoids antioxidant activity. Carotenoids are singlet oxygen quenchers and free radical scavengers and they act as light filters. Findings about carotenoids activity in vitro should not be translated to activity in biological systems. Carotenoids are an important part of human diet because of their antioxidant activity and some of them are also provitamins A. Carotenoids probably prevent some diseases, such as cardiovascular diseases and certain cancers, but can in certain circumstances increase the risk of disease.
Najdeno v: osebi
Ključne besede: oljčno olje, karotenoidi, antioksidanti
Objavljeno: 10.07.2015; Ogledov: 2208; Prenosov: 15
URL Polno besedilo (0,00 KB)

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