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ABSTRACT: Malolactic fermentation (MLF) is an important step in cider production in order to allowing for improvement of microbiological stability and organoleptic characteristics of cider. Induction of this fermentation by using starter cultures enables a better control over this bioprocess, but although it is a common practice in winemaking, starters specifically focussed for cider MLF are not yet commercially available. Proper starter cultures need to present the ability to degrade l-malic acid conferring pleasing sensory characteristics while avoiding toxicological risks. In this work, lactic acid bacteria (LAB) were first isolated from MLF industrial cider samples, obtained in a cellar in the main cider-producing region of Spain, Asturias. Isolates, identified by molecular tools, belonged to the Lactobacillus brevis and Oenococcus oeni species. After a phylogenetic analysis, representative strains of both identified species were evaluated in order to determine their fermentation capacity, showing O. oeni the best behaviour in this cider fermentation, as previously demonstrated for wine in the literature. Consequently, and with the aim to test the influence at strain level, selection of O. oeni isolates as starters for cider fermentation has been undergone. In order to check the influence of geography over biodiversity, O. oeni strains from six different industrial cellars representing the distinct producing areas in the region (located in a ratio of 30 km) were analyzed by using a specific RAPD method. In this way, isolates were typed in five distinct groups, mainly corresponding to each producing area. All strains isolated from the same cellar showed the same RAPD profile revealing the significance of geographical origin in the indigenous cider LAB. Molecular tools were applied to reject those isolates exhibiting presence of genes related to organoleptic spoilage (exopolysaccharides and acrolein production) or food safety (biogenic amine production), as key selection criteria. Representative strains of each of the five O. oeni RAPD groups were tested as pure cultures to evaluate their technological utility for cider production. Experimental data of malic acid degradation and cell concentration obtained were fitted to previously selected kinetic models aimed to optimization and prediction of bioprocess performance. Four strains revealed as suitable potential starter cultures for conducting MLF in cider production.
Food Microbiology 10/2012; 32(1):32-7. · 3.41 Impact Factor
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ABSTRACT: A deeper knowledge on the complex microbial ecology of malolactic fermentation (MLF) in spontaneous cider production is essential to understand the cider making process, thus, applicable to develop adequate malolactic starters. Trends in food fermentation focussed on the isolation of proper wild-type strains from traditional products to be used as starter cultures, with the aim of conducting industrial production processes without losing their unique flavour and product characteristics. A mixed inoculum consisted of samples taken from the four main areas of the most traditional cider making region in Spain was used to carry out MLF under controlled laboratory conditions. A culture-based approach was used to investigate the diversity of lactic acid bacteria (LAB) by molecular tools. By monitoring MLF, population dynamics involved in the fermentation process were assessed. Interactions of different microorganisms adapted to a common environment, competition and resistance during the process, give rise to dominant species showing selective advantages. The main aim of this work was the identification of dominant species during the process in order to obtain potential starter cultures with a clear industrial utility. The fermentative capacity of a representative strain belonging to each isolated species, after analysis of interspecific polymorphisms in 16S rRNA sequencing of 84 isolates, was compared. Molecular characterization for the presence of gene coding for exopolysaccharide production (dps gene amplification), acrolein production (pdu gene amplification) and biogenic amine production (tyrdc, hdc and odc genes amplification) was carried out to verify the suitability of the selected strains.
Food Research International. 01/2010;
Journal of Biotechnology - J BIOTECHNOL. 01/2007; 131(2).