Effect of Foliar Fertilization for Olive Trees on the Bioactive Compounds, Purity and Organoleptic Attributes of Olive Oils

Abstract

his investigation was carried out during two seasons 2014 and 2015 at farm located EL-Nobarya, EL-Behera governorate, Egypt, to study the influence of foliar fertilization with soluation of potassium and magnesium sulphate at ratios of 3 and 5% and 0.5 and 1.5%, respectively, on the organolyptic attributes, purity, overall quality index, stability, bioactive compounds (tocopherols, pigments, polyphenols and diortho phenols) and phenolic compounds of Koronaki olive oil under the environmental condition. The results were as follows : the spraying with potassium and magnesium sulphate at ratios of 5% and 1.5% foliar fertilization, respectively, gave the highest positive attribute (fruity) of olive oil, follwed by 3 and 0.5%, respectively compared with the control samples in seasons 2014 and 2015, while the defect properties of olive oil were equal to zero in both treated (foliar fertilized) and untreated (control) samples during two seasons under study. Results showed that the lowest parameters for K232 and K270 nm. of olive oil were obtained when olive trees were foliar fertilization by potassium and magnesium sulphate at different concentrations in two seasons compared with control samples, while Δk recorded slight increase as a result of all previous treatments. Oleuropein, ellagic and E-vanillic phenolic compounds recorded high content compared to other phenolic compounds in the control samples while ellagic compound decreased compared with the control samples during two seasons.. Commonly, most phenolic compounds increased as a result of all folair fertilization under study. Foliar fertilization with solution of potassium and magnesium sulphate at all concentrations caused a high increment in Epi-catechin and cinamic compounds in season 2015, whilst these compounds decreased in seasons 2014 compared to control samples. But it caused decrease in carotonoids content in two seasons and also in chlorophylls content in season 2014 only. On the other hand, it caused increase in total tocopherol in two seasons with a higher value (5%) for foliar fertilization. Therefore, folair fertilization by potassium and magnesium sulphate at different concentrations caused increment in di-o-phenols of olive oil compared to the control samples during two seasons..

Effect of Combined Sulfur and Nitrogen Foliar Supply on Olive Oil Volatile Compounds and Sensory Attributes

“…In addition to genotype, different chemical environments can cause differences in the enzymatic activity. The levels of available nutrients and their translocation in the plant can significantly affect olive oil quality, so the application of foliar fertilizers can be used to optimize the chemical composition of olive oil and enrich it with beneficial phytochemicals [12]. Nitrogen (N) is a widely used fertilizer.…”

“…Both resulted in a higher concentration of volatile compounds in general. Atta et al [12] reported that foliar application of magnesium (Mg) and K sulfate resulted in higher intensity of olive fruity attribute, but also positively affecting other desirable sensory attributes. Regni et al [28] found that N foliar fertilization did not cause any change in the sensory attributes of oil.…”

Inorganic and organic foliar fertilization in olives

“…Magnesium deficiencies can be overcome with MgSO 4 0.5-3%, while MgO solutions were found to ameliorate the yield and oil quality (Gavalas, 1978;Zouari et al 2014;Tekaya et al 2016;Atta, Mohamed 2017). The results also indicated that foliar application with MgSO 4 , especially at 1.5%, improved the vegetative growth, fruit set, yield, fruit and oil quality of 'Koroneiki' olives (Mahmoud et al 2017).…”

“…Moreover, the K spray application frequency affects the Fe and Zn concentrations in olive stems and leaves (Saykhul et al 2014). A positive effect was observed with foliar KNO 3 applications on the salinity tolerance (Larbi et al 2019) and, furthermore, the K 2 SO 4 application improved the freezing tolerance and oil quality (Petridis et al 2012;Atta, Mohamed 2017;Saadati et al 2020).…”