Influence of the type of alkali on the processing of black ripe olives

Abstract

The darkening process of black ripe olives produces a high volume of wastewater that is phytotoxic due to its high sodium content. The substitution of NaOH by KOH to produce ripe olives was investigated at pilot plant scale with olives of the Hojiblanca, Manzanilla and Cacereña cultivars. No significant differences were observed in this step due to the type of alkali used, although a higher weight increase was found when using KOH instead of NaOH. Furthermore, the final canned product had a similar superficial color, firmness, content of bioactive substances and flavor regardless of the alkali used; the difference with the traditional product was a slightly lower content in Na and six times more K content. Moreover, the concentration of potassium ranged from 6200 to 7500 mg/L in the overall wastewater discharged during the oxidation process with KOH, therefore these solutions could be used as biofertilizer for agriculture purposes.