Search

In olive orchards fungus Spilocea oleaginea Cast. causes olive leaf spot disease. Today it's safe to say that olive leaf spot is a significant and serious problem in almost all of our olive orchards, including those with organic production. It adversely affects fertility of infected trees, and its consecutive occurrence year-in year-out causes degradation of whole olive trees, particularly young ones. Olive leaf spot is readily controlled by copper fungicides. For effective olive protection, in one year is needed some of application. It was thought for long that olive leaf spot infection could be prevented by means of two treatments with copper preparations (September - October and March – April). The first treatment in fall, before the rains, is necessary, because the rainy period creates conditions for primary infections. This reduces the possibility of spring infections by 87% to 95%. For the purpose of protection of olives against olive leaf spot in organic production it is allowed to use only copper fungicides. Concentration of applied preparations must be strictly under control because of possible copper residues in olive fruits and subsequently in oil as well, which is restricted by law. In years with remarkably warm and rainy falls, one treatment with copper fungicides in fall surely is not enough. It is necessary to perform at least three treatments with copper fungicides. The treatments with copper fungicides are allowed up to 56 days prior to harvest. The law also provides the maximum allowed quantity of 0.40 mg Cu/kg in table olives and olive oils. With more treatments in fall it is certainly impossible to fully observe all the regulations. Otherwise, if one were to observe the regulations, there arises a question as to whether is it actually possible to adequately protect olive groves against this nasty and rising disease at all. The experiment was conducted in 2009. and 2010. in a 25-year-old olive orchard, to find out if a several fall applications with copper fungicides would cause a copper residues in olive oil. However, in bought year olive were treated 3 times in fall every 15 days with copper fungicides. The results of this research show that in the bought year in all semples no traces of copper were faund above permissible limit (0.13 - 0.26 mg/kg).

The evaluation of the influence of olive oil phenols on the stability of extra virgin olive oils by the determination of the oxidative stability index, the ABTS and DPPH radical test, and the quali-quantitative analysis of the phenolic compounds, plays a key role in the assessment of the overall olive oil quality. In this study virgin olive oils from selected autochthonous Croatian varieties were investigated in order to evaluate the contribution of their phenolic compounds on the oxidative stability. Two year researches were conducted on the monovarietal olive oils (Oblica, Lastovka, Levantinka, Drobnica, Mastrinka) obtained by the same technological processing system, centrifugal extraction into two phases. The olive fruits came from different groves in Dalmatia region, a central part of Croatian Adriatic coast. The polar extracts of olive oil samples were submitted to spectrophotometric analysis of total phenols and to liquid chromatographic determination of their quali-quantitative profile (HPLC-DAD/MSD). To obtain a complete description of oil samples, fatty acid composition, ultraviolet indices (K232, K270, and ΔK), free acidity degree and peroxide value were also determined according to the European Union methods 20 stated in Regulation 2568/91. Beside analyses mentioned above, researches are amplified by oxidative stability determination by Rancimat method, evaluation of antioxidant activity by DPPH and ABTS methods as well as antioxidant capacity (AOP). The evolution of the analytical parameters studied shows that certain groups of phenolic compounds (secoiridoides, flavones and lignans) have a higher antioxidant activity and antioxidant capacity than the total phenols. The results obtained in this study will contribute to better understanding of peculiar characteristics of local varieties of olive oil and set the basis for their characterization and evaluation.