Evaluation of lactic acid bacteria and yeast diversity in traditional white pickled and fresh soft cheeses from the mountain regions of Serbia and lowland regions of Croatia

Highlights

• Indigenous microbiota of 18 artisanal cheeses from Serbia and Croatia was determined.

• LAB and yeast species were identified by using traditional and molecular methods.

• High diversity of LAB and yeast populations were found.

• Impact on starter culture development for traditional cheeses with defined properties

• Implementation in controlled production of artisanal cheeses with geographical origin

Abstract

The goal of this study was the characterisation of indigenous lactic acid bacteria (LAB) and yeasts isolated from nine white pickled (BG) and nine fresh soft (ZG) artisanal cheeses collected in Serbia and Croatia. While LAB were present in all of the cheeses collected, yeasts were found in all BG cheeses but only in three ZG cheese samples. High LAB and yeast species diversity was determined (average H′_L = 0.4 and H′_Y = 0.8, respectively). The predominant LAB species in white pickled (BG) cheeses were Lactococcus lactis, Lactobacillus plantarum, and Leuconostoc mesenteroides, while in fresh soft (ZG) cheeses the most dominant LAB species were L. lactis, Enterococcus faecalis, and Leuconostoc pseudomesenteroides. Among the 20 yeast species found, Debaryomyces hansenii, Candida zeylanoides, and Torulaspora delbrueckii were found to be predominant in BG cheeses, while Yarrowia lipolytica was predominant in ZG cheeses. The characterisation of metabolic and technological potentials revealed that 53.4% of LAB isolates produced antimicrobial compounds, 44.3% of LAB strains showed proteolytic activity, while most of the yeast species possessed either lipolytic or proteolytic activity. In conclusion, the results obtained in this study showed that the composition of LAB and yeast populations in white pickled and fresh soft cheeses is region specific. The knowledge gained in this study could eventually be used to select region specific LAB and yeast strains for the production of white pickled and fresh soft artisanal cheeses with geographically specific origins under controlled conditions.

Introduction

The Western Balkan Countries (WBC) constitute a distinct geographical region in Europe with long experience in the production of traditional dairy foods by spontaneous or controlled fermentation of cow's, ewe's and goat's milk. In this region, various spontaneously fermented dairy products, such as white pickled and fresh soft cheeses, are manufactured in households without the use of commercial starter cultures. Most of these products are made from unpasteurised milk and the composition of the “natural starter” depends solely on the microbiota present in the raw milk or in the local environment. These microorganisms contribute to preservation, flavour, aroma and texture, determining unique product characteristics.

Preliminary characterisation of the dominant microbiota in these artisanal dairy products revealed that they contain a considerable diversity of lactic acid bacteria (LAB) and yeasts. LAB isolated from autochthonous cheeses have considerable genetic, metabolic and technological potential: good milk protein coagulation, accelerated acidification, production of proteinases, exopolysaccharides, aroma and taste precursors, as well as health-promoting properties (Topisirovic et al., 2006). The dominant LAB are represented by various lactobacillus species: leuconostocs, enterococci, Streptococcus thermophilus and Lactococcus lactis (Randazzo et al., 2002, Terzic-Vidojevic et al., 2007, Nikolic et al., 2008, Jokovic et al., 2008, Chebeňová-Turcovská et al., 2011). Yeast species usually represent secondary microbiota in dairy products and among them Kluyveromyces marxianus, Debaryomyces hansenii and Saccharomyces cerevisiae are usually found to be predominant (Frolich-Wyder, 2003, Chebeňová-Turcovská et al., 2011). Moreover, recent studies have indicated that food borne yeasts D. hansenii and Yarrowia lipolytica could successfully be used as part of starter cultures for cheese manufacturing, enhancing flavour development during cheese maturation (Ferreira and Viljoen, 2003, Sørensen et al., 2011).

Considering the significant role of autochthonous microbiota in the determination of the main features of a cheese, the goal of this study was the identification and characterisation of LAB and yeasts associated with the production of artisanal white pickled and fresh soft cheeses traditionally performed in rural households in the mountain regions of Serbia and lowland regions of Croatia. To our knowledge, this is the most complete study highlighting the phenotypic and genotypic diversity of LAB and natural yeast isolates from traditional cheeses in Serbia and Croatia.