The influence of olive tree fertilization on the phenols in virgin olive oils. A review

Abstract

The total phenols in virgin olive oil are highly dependent on cultivar, but also on ripening stage and other agronomic factors. The focus of most studies on agronomic factors has been irrigation, while fertilization has received less attention. Most of the fertilization works find that nitrogen over-fertilization leads to a decrease in phenol contents in virgin olive oil (VOO) and extra virgin olive oil (EVOO), under rain-fed or irrigation management. Ortho-diphenols also decrease with high doses of nitrogen, with no effect on secoiridoids. Phosphorous has a minor effect on irrigated trees; while the role of potassium is controversial, with a lack of trials with calcium and micro-nutrients. Due to the great impact of the fertilization on the phenol content and quality of VOO, new research is necessary with focus aimed at different cultivars and agronomic factors.

Olive Yield and Physicochemical Properties of Olives and Oil in Response to Nutrient Application under Rainfed Conditions

“…Although an adequate application of fertilizes can positively affect photosynthesis and whole-tree physiology, growth and olive yield [ 9 , 11 , 12 , 13 , 14 ], its effect on oil quality is scarce and inconsistent, especially under rainfed conditions [ 15 , 16 ]. Still, some trends can be highlighted.…”

“…Still, some trends can be highlighted. Regarding N, most studies indicate that N fertilization reduced the concentrations of phenolics in the oil, either under rainfed or irrigation management [ 15 , 16 , 17 ], indicating, according to the protein competition model, that phenylalanine preferentially flows into protein synthesis rather than toward synthesis of phenylpropanoids [ 15 ]. On the other hand, free fatty acids (FFAs) increased with N application, along with and a positive correlation with N in fruits [ 15 , 17 ].…”

“…Regarding P application, a minor influence on quality has been reported [ 16 ], although a decrease in polyphenols in response to high P fertilization was observed [ 18 ]. However, the effect of P on oil quality was mainly indirect, since high P availability increased N accumulation [ 15 , 16 ]. In addition, Erel et al [ 15 ] found no significant effects of P levels on FFAs.…”

“…In addition, Erel et al [ 15 ] found no significant effects of P levels on FFAs. Meanwhile, the role of K is more controversial [ 16 ]. K nutritional level had only a minor effect or no effect at all on oil quality traits such as polyphenols or fatty acids contents, probably because unlike N and P, K is not an intrinsic mineral in oil or in any organic tissue [ 15 , 18 ].…”