Efficacy of yeast starters to drive and improve Picual, Manzanilla and Kalamàta table olive fermentation.

BACKGROUND: Table olive fermentation is an unpredictable process and frequently performed using traditional practices often inadequate to obtain products with acceptable quality and safety standards. In the present study, the efficacy of selected yeast strains as starters to drive fermentations of green and black table olives by the Greek method was investigated. Pilot-scale production by spontaneous fermentation as a control, olives started with previously selected Saccharomyces cerevisiae strains and fermentation driven by commercial S. cerevisiae baker's yeast strain were carried out for each of Manzanilla, Picual and Kalamàta table olive cultivars. RESULTS: Time of fermentation was significantly shortened to 40 days to complete the transformation process for all three tested cultivars. Inoculated table olives were enhanced in their organoleptic and nutritional properties in comparison with corresponding samples obtained by spontaneous fermentation. The use of starters was also able to improve safety traits of table olives in terms of biogenic amine reduction as well as absence of undesired microorganisms at the end of the process. CONCLUSIONS: Autochthonous, but also non-autochthonous, yeasts can be used to start and control table olive fermentations and can significantly improve quality and safety aspects of table olives produced by many smallholder farmers. © 2018 Society of Chemical Industry.

The molecular characterization of 16 new sequence variants of Hop stunt viroid reveals the existence of invariable regions and a conserved hammerhead-like structure on the viroid molecule.

At present isolates of Hop stunt viroid (HSVd) are divided into five groups: three major groups (plum-type, hop-type and citrus-type) each containing isolates from only a limited number of isolation hosts and two minor groups that were presumed to derive from recombination events between members of the main groups. In this work we present the characterization of 16 new sequence variants of HSVd obtained from four Mediterranean countries (Cyprus, Greece, Morocco and Turkey) where this viroid had not previously been described. Molecular variability comparisons considering the totality of the sequence variants characterized so far revealed that most of the variability is found in the pathogenic and variable domains of the viroid molecule whereas both the terminal right (T(R)) and left (T(L)) domains are regions of low or no variability, respectively, suggesting the existence of constraints limiting the heterogeneity of the sequence variants. Phylogenetic analyses revealed that sequence variants belonging to the two minor recombinant subgroups are more frequent than previously thought. When the cruciform structure alternative to the typical rod-like conformation was considered it was observed that the upper part of this structure (hairpin I) was strictly conserved whereas in the lower part a reduced variability was found. The existence of a covariation in this lower part was notable. Interestingly, a hammerhead-like sequence was found within the T(R) domain of HSVd and it was strictly conserved in all the sequence variants. The evolutionary implications of the presence of this motif on the HSVd are discussed.