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Debittering of black dry-salted olives

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Abstract

The objective of this work was to investigate the debittering process of dry-salted olives. Fruits of the Manzanilla cultivar were put into layers of coarse salt and their physicochemical and microbiological parameters were assessed during the dehydration step. A correlation between the content in salt of the olive juice and the ratio salt/olives was found: the lower the ratio, the higher the concentration of salt in the dry-salted olives. The population of lactic acid bacteria on the olive surface was not significant while yeasts, molds and Enterobacteriaceae were the predominant microbiota. In addition, the analyses of phenolic compounds in the olive flesh revealed that most of them disappeared during the dehydration process, in particular the bitter glucoside oleuropein. Likewise, freshly harvested olives were pasteurized and submitted for dehydration but in this case the degradation of oleuropein and the rest of polyphenols did not occur. All these findings suggest that olive debitter during the dry-salting process due to the enzymatic oxidation of oleuropein in the olive flesh resulting in no leaching of the phenolic glucoside in the generated brine.

Practical applications: This is the first report focusing on the debittering process of dry-salted olives. An enzymatic pathway for oleuropein degradation has been found, and it opens up the possibility to optimize this reaction taking into consideration the variables involved such as phenolic compounds, oxidative enzyme, and oxygen. The ratio salt/olives must be as low as 0.4 to reach a high concentration of salt in the juice of dehydrated olives needed for the chemical and microbial stability of the product.

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