Vpliv izbranih tehnoloških postopkov na kemijske in senzorične značilnosti slovenskih deviških oljčnih olj

• Main Author: Bučar-Miklavčič, Milena
• Other Authors: Golob, Terezija
• Format: Doctoral or Postdoctoral Thesis
• Language: Slovenian
• Published: M. Bučar-Miklavčič 2019
• Subjects: deviško oljčno olje; analizne metode; senzorične značilnosti; skladiščenje; filtracija; namakanje; virgin olive oil; sensory analyses; sensory properties; analytical methods; shelf-life; filtration; irrigation; info:eu-repo/classification/udc/664.33:634.63:543.2/.9; DML
• Online Access: https://repozitorij.uni-lj.si/IzpisGradiva.php?id=113288; https://repozitorij.uni-lj.si/Dokument.php?id=125335&dn=; https://plus.si.cobiss.net/opac7/bib/5143416?lang=sl

V raziskavi smo proučevali vpliv skladiščenja oljčnega olja na vsebnost biofenolov, alkilnih estrov in senzorične značilnosti svežega, eno in dve leti staranega oljčnega olja. Ugotovili smo značilno zastopane sekoiridoidne spojine DMO-AgL-dA, DML-Agl-dA, L-Agl-dA pri sorti 'Istrska belica', pri sorti 'Leccino' DMO-AgL-dA in pri sorti 'Maurino' DMO-Agl-dA, O-Agl-A. Razlike v vsebnosti skupnih biofenolov ter vsebnosti derivatov olevropeina in ligstrozida med olji sorte 'Istrska belica' in olji drugih sort so statistično značilne (ztotal= -5,049, ptotal <0,005 zsec = -4,063, psec <0,005). Vsebnosti so se zelo razlikovale glede na sorto ter glede na letnik pridelave. S statističnim testom Wilcoxon–Mann–Whitney smo pokazali, da so razlike med intenzivnostjo grenkobe in pikantnosti v oljih sorte 'Istrska belica' v primerjavi z drugimi sortami, statistično značilne (zgrenkoba =-3,111, pgrenkoba= 0,002 zpikantnost = -3,688, ppikantnost < 0,005). Analizirali smo 168 vzorcev olj in rezultati so potrdili korelacijo med vsebnostjo alkilnih estrov maščobnih kislin in senzoričnimi napakami. S pomočjo Spearman rank koeficienta smo dokazali šibke, a statistično značilne korelacije za opisnik pregreto in vsebnost alkilnih estrov maščobnih kislin (rs=0,3906) ter za senzorični opisnik žarko in vsebnost alkilnih estrov maščobnih kislin (rs=0,2995). V drugem sklopu raziskav smo proučevali vpliv filtracije na kakovost in obstojnost oljčnega olja. Iz rezultatov maščobnokislinske sestave, tokoferolov in biofenolov je razvidna le razlika med sortami, ni opaznih razlik med nefiltriranimi in filtriranimi olji kot tudi ne med svežimi in po šestih mesecih hranjenja na sobni temperaturi. Opazne razlike pa smo ugotovili v senzorični oceni in večji vsebnosti tirozola in hidroksitirozola v nefiltriranih oljih.V tretjem sklopu smo izvedli prvi namakalni poskus za oljke, da bi proučili sušni stres pri sorti 'Istrska belica', kjer smo poleg dinamike porabe vode, ugotavljali tudi velikost pridelka (kg/ha) in vsebnost olja v plodovih (%) ter maščobnokislinsko sestavo, vsebnost biofenolov ter senzorične značilnosti. Z analizami v letu 2014 smo potrdili, da lahko z namakanjem od 30 % potencialne evapotranspiracije (ETp) do 40 % ETp zagotovimo dovolj visoko vsebnost biofenolov in hkrati vplivamo na ugodno razmerje med biofenoli olevropeinskega in ligstrozidnega izvora. The study examined the effects of olive oil storage on the content of biophenols, alkyl esters and sensory characteristics of fresh and one and two years of stored olive oils. Monitoring of the biophenolic composition of fresh oil revealed that some secoiridoid compounds are more abundant in certain varieties, in particular DMO-AgL-dA, DML-Agl-dA, L-Agl-dA in the cv. ‘Istrska belica’, DMO-AgL-dA in the cv. 'Leccino' and DMO-Agl-dA and O-Agl-A in the cv. 'Maurino '.The statistical test showed that differences in the content of total biophenols and the content of oleuropine and ligstroside derivatives between cv. ‘Istrska belica’ and other varieties were statistically significant (ztotal = -5.049, ptotal <0.005 zsec = -4.063, psc <0.005). The values differred according to the variety and the crop year. With the Wilcoxon-Mann-Whitney statistical test, the differences between the degree of bitterness and pungency in olive oils in the ‘Istrska belica’ variety were statistically significant (zbitterness = -3,111, pbitterness = 0,002, zpungency = -3,688, p <0.005). 168 samples of oils were analyzed, and the results confirmed the correlation between the content of fatty acid alkyl esters and the detected sensory defects. With the statistical test Spearman rank corr., we have shown that correlations are weak, but statistically significant for the sensory descriptor of heated and alkyl esters of fatty acids (rs = 0.3906) and for the sensory descriptions of the rancidity and alkyl esters of fatty acids (rs = 0.2995). In the second series of studies the influence of filtration on the quality and stability of olive oil was studied. The stability of olive oil depends primarily on the content of antioxidants (biophenols and tocopherols) and fatty acid composition, while sensory score is very important for monitoring the quality. From the results of the monitoring of the fatty acid composition and the content of tocopherols and biophenols, only the difference between cultivars is evident, there are no noticeable differences between unfiltered and filtered oils, as well as between fresh and 6 months old oils stored at room temperature. Significant differences were found in the sensory scores and in the levels of tyrosol and hydroxythyrosol, both were higher in unfiltered oils. In the third series of studies we carried out the first irrigation experiment for olives to study the drought stress in the cv. ‘Istrska belica’. In addition to the dynamics of water consumption, the crop quantity (kg/ha), the content of oil in the olive drupes (wt. %) and the fatty acid composition, the content and composition of biophenols in oil samples were determined.