Characteristics of the growth of table olive yeasts at low temperature

The behaviour of Picchia anomala, Picchia membranaefaciens, Pichia minuta, Saccharomyces cerevisiae, Candida diddensii, Candida famata y Debaryomyces hansenii, isolated form olive fermentations at low temperature was studied. The response, growth rate, at increasing time intervals, was studied by means of a General Linear Model (GLM) repeated measures, paying special attention to interactions. The most vigorous yeasts in YMGP were P. anomala, C. diddensii, y Deb. hansenii, who were able to grow at 7ºC and 8% salt. In brine, in addition to the main effects, the interactions salt-yeast, time-pH, time-yeast-species were also significant. P. membranaefaciens showed greater salt tolerance in brine than in YMPG. S. cerevisiae, P. minuta and C. famata were inhibited of both pH 3,5 and pH 4 at 7ºC. A sinergistic effect of salt and pH can inhibit yeast growth at 7ºC.Se ha estudiado el comportamiento de Picchia anomala, Picchia membranaefaciens, Pichia minuta, Saccharomyces cerevisiae, Candida diddensii, Candida famata y Debaryomyces Hansenii a bajas temperaturas. La respuesta, crecimiento relativo determinado a diferentes intervalos de tiempo, se ha estudiado mediante el modelo lineal general (GLM) con medidas repetidas, prestándose especial atención a las interacciones. Las levaduras más resistentes en medio YMGP fueron P. anomala, C. diddensii, y Deb. hansenii que crecieron a 7ºC incluso al 8% de sal. En salmueras, además de los efectos principales, fueron también significativas las interacciones, concentración de sal-especie de levadura, tiempo-pH, tiempo-especie de levadura, tiempo-sal-pH y tiempo-sal-especie de levadura. P. membranaefaciens mostró mayor tolerancia a la sal en la salmuera que en YMGP. S. cerevisiae, P. membranaefaciens y C. famata se inhibieron a 7ºC tanto a pH 3,5 como 4, con independencia de los niveles de sal. Combinaciones adecuadas de pH y sal pueden inhibir el crecimiento a 7ºC.Los autores desean expresar su gratitud a la CICYT (AGL2000-1539-CO2-01) y a la Unión Europea (FAIR-97-9526) por la financiación parcial de esta investigación.Peer reviewe

Use of molecular methods for the identification of yeast associated with table olives

A molecular approach is used for the identification of yeast isolated from table olives. Our results validate those obtained in the past by the classical biochemical methodology. Yeast were isolated from both aerobically and anaerobically processed black table olives and also from canned seasoned green table olives. Molecular identification methodology used included restriction pattern analysis of both PCRamplified 5.8S rRNA gene and internal transcribed spacers ITS1 and ITS2. For some species, sequence analysis of the 26S rRNA gene was necessary. These techniques allowed the identification of three yeast species (Issatchenkia occidentalis, Geotrichum candidum and Hanseniaspora guilliermondii) which had not been described previously in table olives. Saccharomyces cerevisiae and Candida boidinii were the most frequent species in green seasoned olives and processed black olives, respectively. The molecular study of total DNA variability among the S. cerevisiae strains isolated indicates a quite heterogeneous population, with at least four different restriction patterns.Peer reviewe

Preservation in brine of green or turning colour olives

10 páginas, 7 tablas.[ES] La conservación de aceitunas en salmuera, sin tratamiento previo con una solución de hidróxido sódico, da lugar a una fermentación de características relativamente diversas. El desarrollo de microorganismos depende de la materia prima (variedades), flora adherida a ésta, y condiciones físico-químicas. La presencia de levaduras se observa en todos los casos, aunque sólo algunas especies se encuentran de forma sistemática. El desarrollo de bacterias lácticas (cocos y lactobacilos) está influenciado por la variedad y la concentración de sal (no crecen por encima del 8%). La presencia inicial de bacterias Gram-negativas así como la contaminación con otros gérmenes capaces de causar alteraciones se controla bien mediante la corrección del pH inicial de la salmuera con acético a valores en torno a 4.2 unidades. Cuando la conservación se hace a niveles elevados de acidez acética, láctica o de ambas, el crecimiento de gérmenes prácticamente se inhibe. La aplicación del sistema aeróbico puede ser útil, en ciertos casos, para evitar el arrugado.[EN] Preservation of olives in brine, without sodium hidroxide treatment, leads to a fermentative process, which characteristics are diverse. The growth of microorganisms depends on the raw material (cultivars) microflora adhered to the exterior olive surface, and physico-chemical conditions. The presence of yeasts is always observed, although only a few species are systematically found. Lactic acid bacteria (cocci and lactobacilli) depends on the cultivar and the NaCI concentration (a level over 8% is inhibitory for them). The presence of Gram-negative bacteria and other spoiling germs are effectively prevented by the initial correction of brines with acetic acid up to a pH level of aprox. 4.2. Preservation by high concentrations of acetic, lactic or both acids prevents the growth of practically any microorganism. When preservation is carried set by the aerobic system, shrivelling of fruits is avoided in send sensitive cultivars.Peer reviewe

Fermentation profiles of Manzanilla-Aloreña cracked green table olives in different chloride salt mixtures

NaCl plays an important role in table olive processing affecting the flavour and microbiological stability of the final product. However, consumers demand foods low in sodium, which makes necessary to decrease levels of this mineral in fruits. In this work, the effects of diverse mixtures of NaCl, CaCl2 and KCl on the fermentation profiles of cracked directly brined Manzanilla-Aloreña olives, were studied by means of response surface methodology based in a simplex lattice mixture design with constrains. All salt combinations led to lactic acid processes. The growth of Enterobacteriaceae populations was always limited and partially inhibited by the presence of CaCl2. Only time to reach half maximum populations and decline rates of yeasts, which were higher as concentrations of NaCl or KCl increased, were affected, and correspondingly modelled, as a function of salt mixtures. However, lactic acid bacteria growth parameters could not be related to initial environmental conditions. They had a longer lag phase, slower growth and higher population levels than yeasts. Overall, the presence of CaCl2 led to a slower Enterobacteriaceae and lactic acid bacteria growth than the traditional NaCl brine but to higher yeast activity. The presence of CaCl2 in the fermentation brines also led to higher water activity, lower pH and combined acidity as well as a faster acidification while NaCl and KCl had fairly similar behaviours. Apparently, NaCl may be substituted in diverse proportions with KCl or CaCl2 without substantially disturbing water activity or the usual fermentation profiles while producing olives with lower salt content.This work was supported by the Spanish Government (project AGL-2006-03540/ALI, partially financed by European regional development funds, ERDF), and Junta de Andalucía (through financial support to group AGR-125). J. Bautista-Gallego also thanks an I3P fellowships from CSIC.Peer reviewe

Use of a D-optimal mixture design to estimate the effects of diverse chloride salts on the growth parameters of Lactobacillus pentosus

The effects of NaCl, KCl, CaCl2, and MgCl2 and their mixtures on the ionic strength (IS) of the medium and the growth parameters of Lactobacillus pentosus were studied by means of a D-optimal mixture experimental design with constrains (total salt concentration ≤ 9.0%, wt/vol) and the generalized z-value. The IS was linearly related to the concentrations of the diverse salts and its increase, for similar concentrations of salts, followed the order MgCl2 > CaCl2 > NaCl > KCl. Within the experimental region, the lag phase duration (λ) was mainly affected by NaCl and CaCl2 and the interaction KCl with MgCl2. The maximum specific growth rate (μmax) decreased as NaCl (the highest effect), CaCl2, and MgCl2 increased (regardless of the presence or not of previous NaCl); low KCl concentrations had a stimulating effect on μmax, but its overall effect showed a similar trend to the other salts. The maximum population reached (Nmax) was the least affected parameter and decreased as NaCl and CaCl2 concentrations increased regardless of the presence of the other salts. The equations that expressed the growth parameters as a function of the diverse chloride salts, within the limits assayed, were developed and the corresponding z- and harmonic Z-values were estimated.This work was supported by the Spanish Government (projects AGL-2003-00779 and AGL-2006-03540/ALI), and Junta de Andalucía (through financial support to group AGR-125).Peer reviewe

Evolution of endoglucanase activity in olives during ripening and storage and its relationship with cellulolytic microorganisms

[EN] Cellulolytic enzymes are responsible for many of the changes associated with the ripening process in olive fruits (Olea europaea). Evolution of endoglucanase activity (EC 3.2.1.4.) was studied in olives during their ripening and softening, both on the tree and after being picked and stored, and was related to the presence of microorganisms. The time course of cellulolytic activity was measured for four stages of ripeness (green, turning colour, black and ripe black) and was related to the total number of cellulolytic bacteria. The increases in activity during ripening and storage gave an indication of how normal flora influences during the olive ripening process.[DE] Die cellulolytischenEnzyme sind für viele Veränderungen während des Reifens der Olive verantwortlich. Es wurde daher die Aktivität der Enzyme während der Entwicklung der Olive bei der Reifung und dem Weichwerden studiert, und zwar am Baum, nach der Ernte und nach dem Lagern, was auch in Beziehung zu der Gegenwart von Mikroorganismen steht. Es wurde die cellulolytische Aktivitätsentwicklung während der vier Reife-Zustände (grün, farbenwechselnd, schwarz und zartes schwarz) studiert und auf die Gesamtzahl der cellulolytischen Bakterien bezogen. Der Aktivitäts-Zuwachs während des Reifens und Lagerns gibt einen Hinweis, wie die normale Flora auf das Reifen der Oliven einwirkt.Peer reviewe

Instability profile of fresh packed “seasoned” Manzanilla-Aloreña table olives

The shelf life of cracked “seasoned” Manzanilla-Aloreña table olives is short; containers may swell and the fruits become progressively brownish. Respiration of cracked fruits continued for a period longer than 48 h after picking and the carbon dioxide produced may be an initial cause of spoilage. As processing progressed, the microbial loads in the olives increased due to successive washings and, together with the microbial load from the added ingredients, led to relatively high viable counts of yeasts and LAB at packing. During shelf life, this microflora showed an increase in viable counts which could also eventually lead to swelling spoilage. This behaviour was favoured by the presence of residual fermentable substrates and a decrease in potassium sorbate over time in both brine and flesh. At the same time, colour darkened, titratable acidity increased and pH decreased. The application of two additional washings to the cracked olives before packing was favourable because fermentable material and polyphenols were removed; however, fruits with as low as possible respiration rates, stronger washing treatments, ingredients with low or no microbial viable counts and higher preservative concentrations would be necessary to achieve complete stabilization of the product.This work was supported by the Spanish Government (AGL2003-00779 and AGL2006-03540/ALI, partially financed from European regional development funds, ERDF), Junta de Andalucía (through financial support to group AGR-125), and EU (TDC-Olive, FOOD CP 2004 505524).Peer reviewe