Technological characteristics of yeast strains and their potential as starter adjuncts in Greek-style black olive fermentation

Abstract

The technological properties of Debaryomyces hansenii (15 strains) and Torulaspora delbrueckii (32 strains) isolated from Greek-style black olives under conditions typical for black olive fermentation were studied. Furthermore, the killer character of the strains was assessed as well as their antimicrobial action against food-borne pathogens. All strains could grow at 15°C and low pH (2.5), whereas the majority of the strains were able to grow at 10% (w/v) NaCl, assimilated D-galacturonic acid, and showed lipolytic activity. Only 33% of D. hansenii and 9% of T. delbrueckii strains could hydrolyse 1% (w/v) oleuropein. A large majority of the strains tolerated 0.3% (w/v) bile salts, which in correlation with acid resistance indicates probiotic potential. Cross-reactions between culture filtrates of D. hansenii and T. delbrueckii and 56 yeast strains isolated during spontaneous Greek-style black olive fermentation were conducted. Focusing on their lytic activity, 17 mycogenic strains were selected. Culture filtrates of the mycogenic strains inhibited strains of L. monocytogenes, B. cereus and S. typhimurium. The active substance was heat resistant (stable after heating at 100°C for 10 min) as well as stable over a pH range from 4.0 to 6.5. The possible inhibition of undesirable yeast contaminants and food-borne pathogens in situ on fermented olives as well as the probiotic potential of strains used as starter adjuncts would contribute to the improvement of quality of the fermented product.

Yeast Ecology of Fermented Table Olives: A Tool for Biotechnological Applications

“…Strong lipase activity, as well as, weak activity have been detected both in vitro in some yeast species. The former has been reported in Candida boidinii, D. hansenii and T. delbrueckii while the latter only in P. membranifaciens [34,35]. Those authors have emphasized the change of the free fatty acids composition of olives in the presence of yeast populations in contrast with sterile conditions, indicating that lipases produced by these microorganisms modify the characteristics of fruit lipids and therefore its organoleptic characteristics.…”

“…Yeasts with β-glucosidase activity are also good candidates, because they can be used for the hydrolysis of oleuropein, removing the natural bitterness present in brined olives and thus, avoiding the placement of olives into large amounts of water [3,35]. However, limited data are available in the literature about the contribution of these species on table olive fermentation pro cess [7,17,34].…”

“…The probiotic potential of yeasts isolated from fermented table olives has been documented to some extent [8,35]. In particular, Psani & Kotzekidou, [35] found Torulaspora delbrueckii and Debaryomyces hansenii strains to be quite tolerant in high bile salt concentrations and low pH values.…”

“…In particular, Psani & Kotzekidou, [35] found Torulaspora delbrueckii and Debaryomyces hansenii strains to be quite tolerant in high bile salt concentrations and low pH values. Moreover, the fact that the inoculation of these strains were able to inhibit food borne pathogens such as Listeria monocytogenes, Bacillus cereus and Salmonella typhimurium is remarkable.…”

Azeitonas de mesa no Brasil: mercado, tecnologia e aspectos legais

“…O processo fermentativo é lento, devido ao longo período de difusão dos compostos solúveis e da lenta solubilização da oleuropeína na salmoura (HURTADO et al, 2008). A hidrólise da oleuropeína é atribuída ao pH ácido e à atividade da β-Glucosidase produzida pelas leveduras, principal micro-organismo presente na fermentação (PSANI & KOTZEKIDOU, 2006). Quando todos os substratos fermentáveis, como os açúcares, se esgotam, o processo é finalizado com duração média de 8 a 12 meses (CARDOSO et al, 2010).…”