Single and Multiple Inoculum of Lactiplantibacillus plantarum Strains in Table Olive Lab-Scale Fermentations

Barbara Lanza,Barbara Bonvini,Martina Cellini,Sara Di Marco,Miriam Zago,Flavio Tidona,Martina Bacceli,Nicola Simone,Giuseppina Di Loreto

doi:10.3390/fermentation6040126

Abstract

In order to improve the olives’ quality, and to reduce the de-bittering time during the table olive fermentation process, it is necessary to pilot the fermentation by inoculating the brine with selected cultures of microorganisms. Some probiotic tests, such as resistance/sensitivity to antibiotics, bile salt hydrolase (BSH) activity, growth at acidic pH, an auto-aggregation assay, and a test of the production of exopolysaccharides, were carried out in order to screen 35 oleuropeinolytic Lactiplantibacillus plantarum subsp. plantarum strains to be used in guided fermentations of table olives. On the basis of the technological and probiotic screening, we analyzed the progress of three different lab-scale fermentations of Olea europaea L. Itrana cv. olives inoculated with spontaneous, single, and multiple starters: jar A was left to ferment spontaneously; jar B was inoculated with a strongly oleuropeinolytic strain (L. plantarum B1); jar C was inoculated with a multiple inoculum (L. plantarum B1 + L. plantarum B51 + L. plantarum B124). The following parameters were monitored during the fermentation: pH, titratable acidity, NaCl concentration, the degradation of bio-phenols, and the enrichment rate of hydroxytyrosol and tyrosol in the olive’s flesh, oil and brine. The degradation of secoiridoid glucosides appeared to be faster in the inoculated jars than in the spontaneously-fermented jar. The production of hydroxytyrosol and ligstroside aglycons was high. This indicated a complete degradation of the oleuropein and a partial degradation of the ligstroside. The multiple inoculum ensured a complete debittering, and could give probiotic traits. The presence of L. plantarum B1 and B124 as a fermentation starter guarantees an optimal trend of de-bittering and fermentation variables, thus ensuring the production of a better final product. L. plantarum B51 could be considered to be a promising probiotic candidate for obtaining probiotic food of completely vegetable origin.

Highlights

Today, table olives, the most widespread traditional product of the Mediterranean area, are considered to be becoming a functional food
Erythromycin, tetracycline and chloramphenicol; four lactobacilli were resistant to gentamicin
One of the most important aspects of the improvement of the quality of table olives concerns the quality of the fermentation, which can be implemented through the use of starter cultures of lactic acid bacteria (LAB), selected according to their specific technological properties, capable of starting and driving the fermentation by taking over from the indigenous microflora that are already present on the drupes [32]

Summary

Introduction

Table olives, the most widespread traditional product of the Mediterranean area, are considered to be becoming a functional food. The scientific community has focused its attention on fermented foods, recognizing their important role as vehicles of probiotic microorganisms [3]. Table olives represent a valid source of probiotics, mainly lactic acid bacteria (LAB) [4,5,6,7] and yeasts [8,9]. These microorganisms play an important role during fermentation, and they are responsible for the acidification of the brine and for the development of the organoleptic characteristics, respectively. The use of starter cultures with β-glucosidase positive strains was extensively applied to reduce the debittering time and to control the fermentation process [10,11,12]

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