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Improve table olive products using osmotic pre-treatment, natural herb extracts.

Olive-based products are prominent in the Mediterranean diet. But the fermentation of olives relies on the use of high-salt brine.

It's commercially challenging to the olive processing industry to create reduced-salt products that also have an extended shelf life, and which offer alternative sensory characteristics tailored to the preferences of different consumer populations, such as those in the Orient.

Greek scientists tried to limit salt uptake during olive fermentation by using an osmotic dehydration pre-treatment. Their goal was to enrich table olives with natural bioactive compounds, during the post-processing stage, in order to develop new olive products that would have superior sensory and nutritional characteristics.

The researchers found that the osmotic pre-treatment of green olives, in combination with the use of essential oils and antioxidant extracts, can lead to salt-reduced table olives with superior nutritional and sensory characteristics.

They used a 70% glucose-containing syrup as an osmotic treatment for green table olives before they were fermented. The scientists monitored osmotic dehydration for water activity, water loss and solids gain.

The investigators fermented the olives with 10% salt for two months and then pasteurized them, while monitoring brine acidity and microbial growth. Pasteurized products were packed in low-salt solutions enriched with bioactive compounds (antioxidants and essential oils) extracted from different herbs--rosemary, dittany, and ginseng--and stored at 25 C.

The main extracted or distilled bioactive compounds were identified using high-performance liquid chromatography with diode-array detection and liquid chromatography-mass spectrometry analyses. The loss of water and gains in solids content in the olives increased with the increasing time of osmosis. Overnight osmosis resulted in a decrease in water activity from 0.965 to 0.941.

The osmotic pre-treatment of olives favored fermentation, as lactic acid bacteria were the dominant microbial population. An analysis of overall sensory quality, salt perception, phenolic content and microbial growth during storage confirmed the absence of pathogens.

The spoilage growth rates indicated that the olives had a shelf life of approximately two years. The salt content of the final product was 12% lower than that of conventional table olives.

Further information. Petros S. Taoukis, Department of Chemical Engineering, National Technical University of Athens, Heroon Polytechniou 9, 15780 Zografou, Greece; phone: +302107723171; email:

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Publication:Emerging Food R&D Report
Date:Apr 1, 2016
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