Research Article: Influence of cultivar, irrigation, ripening stage, and annual variability on the oxidant/antioxidant systems of olives as determined by MDS-PTA

Date Published: April 18, 2019

Publisher: Public Library of Science

Author(s): Juan Antonio Sáinz, Inmaculada Garrido, Marcos Hernández, Alfonso Montaño, José Luis Llerena, Francisco Espinosa, Branislav T. Šiler.

http://doi.org/10.1371/journal.pone.0215540

Abstract

The phenolic composition and content of olive fruit are some of the attributes that determine oil quality. This composition depends on the olive variety, the cultivation system, and the fruit’s ripeness. This study considered two olive varieties (Manzanilla and Morisca), under two water regimes (irrigated and rainfed), harvested at three stages of maturation (S1, S2, and S3), over three consecutive campaigns (2011, 2012, and 2013). The accumulation of phenols in the fruit was found to depend only on the stage of ripeness, while the flavonoid and phenylpropanoid contents depended also on the variety and the water regime. Superoxide dismutase (SOD) activity was linked to O2- production, which in turn depended on water regime, variety, and stage of maturation (this last being a process involving ROS). The peroxidase (POX) activity seemed only to depend on ripeness, while polyphenol oxidase (PPO) activity varied from year to year as well as presenting a strong ripeness dependence that was in clear coherence with the levels of phenolic compounds that the olives accumulate. All these relationships between the variables and the factors conform a dataset with the structure of a multidimensional array that is difficult to interpret using conventional techniques of statistical analysis. This work takes a novel approach (MultiDimensional Scaling associated with a Partial Triadic Analysis, MDS-PTA) to the analysis of this type of data structure which allows its correct interpretation. The analysis showed that the state of maturation of the olives is the most clearly discriminating factor, far more so than the cultivar, water regime, or year. Thus, the phenols and the total antioxidant activity (FRAP) showed strong clustering, being closely related in all three years studied. The oxidant and antioxidant activities showed a certain tendency to cluster, although in these cases the year also had an influence as a factor, indicating that these parameters depend more on external factors and less on ripeness.

Partial Text

The virgin oils obtained from olives (Olea europaea, L.) are an important source of lipids in the Mediterranean diet. In recent years, numerous studies have shown evidence for their nutritional and therapeutic properties [1]. This quality depends on various factors, among which are the cultivar, growing technique, state of maturity at the time of harvest, environmental factors, and extraction technique [2–4]. During the ripening of the fruit, biochemical processes take place affecting the content of sugars, phenols, etc., and these processes lead to changes in texture, firmness, and colour, which in turn determine the nutritional and organoleptic quality of the fruit [5]. Alterations during ripening occur at the membrane level, and end in a process of programmed cell death. Softening of the fruit involves processes of cellular oxidation and peroxidation [6].

 

Source:

http://doi.org/10.1371/journal.pone.0215540

 

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