Application of multi-functional lactic acid bacteria strains in a pilot scale feta cheese production

Abstract

Feta cheese is the most recognized Greek Protected Designation of Origin (PDO) product in the world. The addition of selected autochthonous lactic acid bacteria (LAB) strains to cheese milk as adjunct cultures is gaining more attention, since they can impact the nutritional, technological and sensory properties of cheeses, as well as improve the safety of the product. The aim of this study was to produce Feta cheese with enhanced quality and safety, and distinctive organoleptic characteristics by applying autochthonous lactic acid bacteria (LAB) with multi-functional properties as adjunct cultures. Feta cheeses were produced with the commercial lactococcal starter culture and the addition of 9 LAB strains (Lactococcus lactis SMX2 and SMX16, Levilactobacillus brevis SRX20, Lacticaseibacillus paracasei SRX10, Lactiplantibacillus plantarum FRX20 and FB1, Leuconostoc mesenteroides FMX3, FMX11, and FRX4, isolated from artisanal Greek cheeses) in different combinations to produce 13 cheese trials (12 Feta trials with the adjunct LAB isolates and the control trial). In addition, Feta cheese manufactured with FMX3 and SMX2 and control Feta cheese were artificially inoculated (4 log CFU/g) with Listeria monocytogenes (a cocktail of 4 acid or non-acid adapted strains). Cheese samples were monitored by microbiological and physicochemical analyses during ripening, and microbiological, physicochemical, molecular and sensory analyses during storage at 4°C. The results showed that after manufacture, the LAB population was ca. 9.0 log CFU/g at all samples, whereas during storage, their population declined to 6.5–7.0 log CFU/g. In the Listeria inoculated samples, Listeria was absent after 60 days (end of ripening) and after 90 days in the adjunct culture, and in the control trials, respectively. Moreover, the addition of selected strains, especially Lcb. paracasei SRX10, led to cheeses with desirable and distinctive organoleptic characteristics. Furthermore, randomly amplified polymorphic PCR (RAPD-PCR) molecular analysis confirmed that the multi-functional LAB strains were viable by the end of storage. Overall, the results of this study are promising for the use of autochthonous strains in various combinations with the commercial starter culture to satisfy industry requirements and consumer demands for traditional and high added value fermented products.

Dissecting the Genetic Basis of the Technological, Functional, and Safety Characteristics of Lacticaseibacillus paracasei SRX10

“…However, LAB tend to exhibit greater tolerance to these stresses, which makes them valuable contributors to the fermentation process and the preservation of various foods [ 53 ]. Here, we annotated several genes involved in survival under these harsh conditions ( Table 3 ), in agreement with previous data on the viability of the strain during yoghurt and feta cheese production [ 7 , 18 ]. Numerous studies have also identified these loci within the genome of the Lc.…”

“…In this study, whole-genome sequencing, annotation and comprehensive bioinformatic analyses were performed to provide deeper understanding of the functional, technological, and safety properties of Lc. paracasei SRX10, a multifunctional strain that has previously been employed as an adjunct culture in yoghurt and feta cheese production [ 7 , 18 ]. The genome of the strain consists of a chromosome with a length of 2.8 Mb and a GC content of 46.4%, coding for 2711 putative proteins.…”

“…Previously, we showed that lactic acid was produced in high concentrations in feta cheese fermented by Lc. paracasei SRX10 (16.3–22.0 mg/g), while citric acid and acetic acid were detected in lower quantities [ 18 ]. Lipid and protein degradation in the food matrix during production and ripening is known to determine the nature of the final product [ 59 , 60 ].…”

“…paracasei SRX10 exhibits favorable technological and functional properties, including tolerance to acidic pH and bile salts, susceptibility to common antibiotics, and the ability to produce β-galactosidase and exopolysaccharides [ 7 ]. Furthermore, the strain was successfully incorporated as an adjunct culture in the production of yogurt and feta cheese, with desirable and distinctive organoleptic characteristics [ 7 , 18 ]. The aim of this study was to explore the genetic basis of these properties using comprehensive bioinformatic analysis.…”