Prevalent lactic acid bacteria in cider cellars and efficiency of Oenococcus oeni strains.Food Microbiol. 2012 Oct; 32(1):32-7.FM
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.