Abstract
The control of the spontaneous fermentation process of un-debittered Moroccan Picholine green olives was undertaken basing the inoculation with two lactobacilli strains ( Lactobacillus plantarum S175 and Lactobacillus pentosus S100). These strains, previously selected in our laboratory for their oleuropein-degrading capacity, were inoculated in olives brined at 5% of NaCl, and then incubated at 30 AaC. The physico-chemical parameters (pH, free acidity, reducing sugars, sodium chloride, oleuropein and its hydrolysis products), and the microbiological parameters (mesophilic aerobic bacteria, coliforms, Staphylococcus , lactic acid bacteria and yeasts and moulds), were regularly analyzed during the fermentation time. The results obtained showed the effectiveness of the lactic acid bacteria strains to develop suitable oleuropein biodegradation and controlled lactic fermentation processes more than the un-inoculated olives (control). This result was confirmed by the rapid elimination of coliforms and staphylococcus, the accumulation of hydroxytyrosol as a result of oleuropein biodegradation, and a drastic reduction in spoiled olives with good quality fermented olives.
Highlights
The natural lactic fermentation of green olives is a complex process
The lactic acid bacteria (LAB) and yeasts considered as beneficial microorganisms are highly desired to assure the fermentation process of olives which leads to their transformation to edible products, in comparison to the role played by undesirable microbiota, composed of enterobacteria, Bacillus and moulds, known for their involvement in various olive spoilages (Fernández-Diez et al, 1985, Garrido-Fernández et al, 1997, Arroyo-López et al, 2012, Hurtado et al, 2012).The control of the natural olive fermentation process with selected LAB strains is of great importance to reduce olive spoilage and to improve the organoleptic properties of the end product
The assays were carried out as follows:: un-inoculated control,: olives inoculated with L. plantarum S175 and: olives inoculated with L. pentosus S100
Summary
The natural lactic fermentation of green olives is a complex process. It is mainly based on a spontaneous fermentation characterized by its long duration and frequently associated with high spoilage incidence in olives, and leads to an end product with varying quality (Fernandez-Diez et al, 1985). Green olives are not edible without the elimination of bitterness, due to their natural polyphenols, mainly oleuropein This polyphenol is known for its antimicrobial activity against various microorganisms, LAB (Juven B. et al, 1968, Fleming and Etchells, 1967, Fleming et al, 1973, Furneri et al, 2002, Ruiz-Barba et al, 1990, Ruiz-Barba et al, 1991, Ruiz-Barba et al, 1993, Landete et al, 2008, Medina et al, 2009, Rodríguez et al, 2009) which is highly desired to assure the natural lactic fermentation of green olives. The main LAB involved in this process is composed of L. plantarum, L. pentosus, L. brevis, Leuconostoc and Pediococcus (Durán Quintana et al, 1997, Rodríguez et al, 2009) Among these species Lactobacillus plantarum and L. pentosus were reported as effective starters to allow for a controlled fermentation of table olives (Lamzira et al, 2005, Marsilio et al, 2005, Panagou et al, 2008, Sabatini et al, 2008, Servili et al, 2006, Hurtado et al, 2012)
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