Polyphenol changes during fermentation of naturally black olives

Area of Science:

• Food Science
• Analytical Chemistry
• Agricultural Science

Background:

• Phenolic compounds in olives are crucial for their health benefits and sensory properties.
• Natural fermentation is a traditional method for processing olives, significantly altering their chemical composition.
• Understanding the evolution of these compounds during fermentation is key to optimizing quality.

Purpose of the Study:

• To investigate the dynamic changes in phenolic compounds during the natural fermentation of black olives.
• To identify key phenolic transformations and their relationship with color changes.
• To analyze the impact of fermentation on both the olive fruit and its oil phase.

Main Methods:

• High-performance liquid chromatography (HPLC) was used to identify and quantify phenolic compounds.
• Spectrophotometric analysis was employed to assess color changes.
• Olfactory and gustatory analyses were performed to evaluate sensory attributes.
• Fermentation was conducted under controlled aerobic and anaerobic conditions.

Main Results:

• Key anthocyanins (cyanidin 3-rutinoside, cyanidin 3-glucoside) were present in fresh olives but absent after one month.
• Fruit color varied based on fermentation conditions (aerobic vs. anaerobic) due to anthocyanin polymerization.
• Initial polyphenols in olive juice included hydroxytyrosol-4-beta-glucoside, oleuropein, and verbascoside; hydroxytyrosol dominated after 12 months.
• Initial oil phase compounds like dialdehydic elenolic acid derivatives were replaced by hydroxytyrosol, tyrosol, and their acetates.

Conclusions:

• Natural black olive fermentation involves significant phenolic compound evolution, primarily through acid hydrolysis.
• Changes in anthocyanins and polyphenols directly influence the final color and composition of fermented olives.
• The study provides novel insights into the biochemical processes governing phenolic changes during olive fermentation.