Storage of mechanically harvested Manzanilla olives under controlled atmospheres

Abstract

The mechanical harvesting of Manzanilla fruit destined for Spanish-style green table olives has never been developed on an industrial scale because of the brown spots formed on the bruised areas during olive transportation from the groves to the olive factories. In this study, the use of several inert atmospheres to preserve mechanically harvested olives was investigated. Nitrogen, argon and nitrogen spiked with SO2 (0.01–0.05%) prevented the formation of brown spots on the bruised areas for at least 6h but the browning reactions rapidly progressed after the inert atmosphere was released. Olives were also immersed in several chemical solutions (0.5% ascorbic acid, 0.3% NaOH, 0.05% SO2, and 1% glycerol) before and after the postharvest storage in nitrogen with the aim of reducing oxygen diffusion into the fruit. Only the use of glycerol as a coating layer before the nitrogen atmosphere showed slightly good results. Moreover, it has been demonstrated that the browning reactions in bruised olives were developed due to the oxidation of oleuropein without the requirement of any previous hydrolysis reactions of this polyphenol. The decrease in oleuropein and increase in darkening of the bruised areas of olives preserved in nitrogen and re-exposed to air was also caused by enzymatic reactions.