Uses of olive solutions for agricultural purposes: their chemical characteristics

two main types of commercial table olives are the Spanish-style green and the Californian-style black olives respectively. A high volume of contaminated wastewaters is generated during processing of table olives that constitute a big environmental problem for factories. Among them, the washing waters of green olives (1) and the acidified preservation solution of black olives (2) contain high amount of substances with antimicrobial activity against plant pathogens (3).The chemical characteristics of 70 samples of washing waters generated in 9 table olive factories during the season 2014/2015 were analyzed. Some of these olive solutions were also acidified with nitric acid, stored for months at room temperature, concentrated 10 fold under vacuum and adjusted their pH up to 5 units with potassium hydroxide. The mean concentration of sugars (glucose, fructose and mannitol) in these washing waters was 50 mM, and phenolic compounds (hydroxytyrosol, tyrosol, hydroxytyrosol 1-glucoside and hydroxytyrosol 4-glucoside) accounted for 12 mM. The content in acetic acid and ethanol was lower than 0.1 %. The concentrated solutions were also rich in minerals such as nitrogen and potassium, the percentage of them being higher than 3 %. Therefore, these solutions could also comply with the legal requirements for liquid organic-mineral fertilizer.This work was supported by grant P12-AGR-1123 from Junta de Andalucía and the European Union FEDER fundsPeer Reviewe