Characterisation of Phenolic Compounds in Oils Produced from Frosted Olives.pdf
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1、ORIGINAL PAPER Characterisation of Phenolic Compounds in Oils Produced from Frosted Olives Claudia GuillaumeLeandro Ravetti Sonja Gwyn Received: 30 January 2009/Revised: 6 August 2009/Accepted: 14 October 2009/Published online: 6 November 2009 ? AOCS 2009 AbstractFrost is one of the most important w
2、eather related hazards for the Australian olive industry and it has caused signifi cant economic losses during the last decade. Its impact on oil quality was signifi cant in 2006 with more than 20% of Australian oil of that year being affected to some degree. Early frosts will normally affect the fr
3、uit leading to signifi cant changes in the chemical and orga- noleptic characteristics of the oils. The aim of this work was to study the effect of freeze damage on the phenolic composition and quality parameters of oils from three different varieties: Frantoio, Barnea and Picual. Quality chemical p
4、arameters showed signifi cant differences in oils produced from fruit that was frozen for 2 and 4 weeks. Those chemical parameters were not signifi cantly different in the oil produced from fruit immediately after being frosted. Nonetheless, the sensorial profi le and the poly- phenols showed signif
5、i cant changes even with oils pro- duced within a short time after the freezing event. Those changes became more evident with the oils produced at increasing time from the moment of fruit freezing. KeywordsLipid chemistry ? Lipid analysis Introduction Frost is one of the most important weather relat
6、ed hazards for the Australian olive industry and it has caused signifi - cant economic losses during the last decade. Its impact on oil quality was signifi cant in 2006 with more than 20% of Australian oil of that year being affected to some degree 1. Early frosts will normally affect the fruit lead
7、ing to sig- nifi cant changes in the chemical and organoleptic charac- teristics of the oils 2. Depending on the characteristics of the frost, the damaged fruit could turn a brownish colour and remain with an aqueous consistency or they could dehydrate remaining shrivelled until harvested. Oils pro-
8、 duced from frosted fruit develop organoleptic defects in the fi rst instance while basic chemical quality parameters are affected signifi cantly later after the frost event. Volatile and phenolic compounds are the substances mainly responsible for the fl avour of virgin olive oils and therefore wil
9、l affect the consumers acceptance of this product 3, 4. Studying the volatile and phenolic profi le of frosted oils should enable characterisation of these oils and manage their blends more effi ciently. Objectives The purpose of this project was to evaluate the evolution of the chemical parameters
10、and polyphenols profi le together with sensorial analysis in the most important varieties for the Australian olive industryFrantoio, Barnea and Pic- ualas a consequence of a freezing event. The study considered four treatments: before frost damage, immedi- ately after frost damage, 2 weeks after fro
11、st damage and 4 weeks after frost damage. This will allow description of the evolution in time before and after crushing of the most important quality parameters in (a) olive oils obtained from frosted fruit and (b) characterisation of the phenolic profi le associated with those oils in order to dev
12、elop an analytical system that assists both growers and trading companies to deal with this quality issue. C. Guillaume ( 143.72?E), in low areas of the property where frost damaged fruits had been observed in past years 1 Fruits from three different varieties (Picual, Barnea and Frantoio) with clea
13、rly different fatty acid, phenolic and organoleptic profi les 5 were processed in an experimental olive oil mill (Abencor?) before a frost damaging event, immediately after frost, 2 and 4 weeks after the frost occurred. All oil samples obtained were evaluated based on chemical quality parameters, or
14、gano- leptic parameters and phenolic profi le. Each treatment consisted of three repetitions and each sample from those repetitions was analysed in duplicate. Total samples analysed considering 3 varieties 9 4 treatments 9 3 rep- etitions 9 2 analysis: 72. Basic Quality Parameters Determination of f
15、ree fatty acids (AOCS Ca 5a-40), per- oxide value (AOCS Cd 8-53), UV coeffi cients: K232 and K270 (AOCS Ch 5-91) were carried out (AOCS, 2003). Results were expressed as percentage of oleic acid, meq O2/kg oil, and extinction at 232 and 270 nm, respectively. Induction Time Potential shelf life is ex
16、pressed as induction time. This parameter was measured with a 743 Rancimat (Metrohm secoiridoids derivatives (oleuropein, the aglycone of ligstroside, and their respective decarboxylated dialde- hyde derivatives); and the lignans (?)-1acetoxypinoresi- nol and pinoresinol. All these three classes hav
17、e potent antioxidant properties. Other important groups such as benzoic acid derivatives (vanillin and vanillic acid), fl av- ones (luteolin and apigenin) and cinnamic acid derivatives (p-coumaric acid, ferulic acid, caffeic acid) have been included, too 3. Phenolic components are related to the sta
18、bility of the oil and the benefi cial role in human health, due their antioxidant properties, but also have a strong relationship with the organoleptic characteristics of the oils (fl avour, aroma, bitterness and pungency), which differentiates between natural or virgin oils and refi ned oils 3. In
19、Fig. 1, the chromatograms clearly show the differ- ences between an oil produced before the frost event and J Am Oil Chem Soc (2010) 87:247254249 123 4 weeks after frost. The concentrations of most olive oil phenolic compounds were affected by the frost damage. The main group of phenols that remarka
20、bly decreases immediately after the freeze injuries is the secoiridoid derivatives (peaks 7, 8, 10, 14 and 16). This data is in accordance with other previous research 10. This signif- icant decrease in the concentration of this group of phenols continues when the oil is processed 2 and 4 weeks afte
21、r the frost event. The reduction of the bitterness and the shelf life of the oil are associated with this decrease as those com- pounds are strongly linked to those parameters. The mesocarp and epicarp tissue destruction caused by the ice crystals developing inside fruit cells would be the main fact
22、or triggering the oxidative degradation of those phe- nolic compounds listed above. The simple phenols such as hydroxytyrosol and tyrosol (peaks 1 and 2, respectively), which normally increase their concentration with time, show an opposite behaviour when the oil is produced from fruits affected by
23、frost. A signif- icant decrease in their concentration was observed as indicated in Tables 4 and 5. Physical damage of fruits by frost is known to lead to cellular destruction which would allow phenolic substrates to mix with PPO. Consequently, the decline in the total levels of these phenolic subst
24、ances could be a result of an enzymatic oxidation that is visually perceived with the browning of the olives. Benzoic acid derivatives, particularly vanillin, were the only components that signifi cantly increased (P0.005) as a percentage of total phenols with the frost damage. As shown in the Fig.
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