Selection of Leuconostoc strains isolated from artisanal Serrano Catarinense cheese for use as adjuncts in cheese manufacture

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

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.

Characterization of Probiotic Properties of Lacticaseibacillus paracasei L2 Isolated from a Traditional Fermented Food "Lben"

Lben is a dairy fermented food that is largely consumed in Tunisia for its numerous health benefits that are related to the existence of probiotics. Lactic Acid Bacteria (LAB) are well known for their beneficial probiotic properties for humans, especially when administered in adequate amounts. The aim of this study was to isolate and investigate the probiotics properties of Lacticaseibacillus paracasei L2 from Lben. The isolated strain was identified by 16S r-RNA gene sequences and MALDI- TOF MS. To evaluate the probiotic potential of the isolated bacterium, in vitro tests were performed, including adhesion ability to HCT-116 cells, survival in acid and bile salt conditions, lysozyme resistance, biofilm formation, hemolytic activity, antioxidant activity, and antimicrobial activity. Our results revealed that the selected Lacticaseibacillus paracasei L2 strain expressed a high adherence to HCT-116 cells (45.03%), survived under acidic conditions (pH3), and showed a resistance to bile salts. The strain was considered as safe (α-hemolysis). L. paracasei L2 showed a high biofilm-formation ability (OD 570 > 1.7) after 24 h of incubation. It also demonstrated an important antioxidant activity in the range of 85.31% for the intact cells. However, an antimicrobial activity against pathogens, namely Staphylococcus aureus, was detected with an IZ that was above 19 mm. In conjunction with the results obtained and the technological properties of Lacticaseibacillus paracasei L2 (proteolytic property, autolytic activity, acidifying activity, and EPS production), this strain may be used as a probiotic for manufacturing fermented foods.

Artisanal Brazilian Cheeses-History, Marketing, Technological and Microbiological Aspects

This review focused on the historical, marketing, technological, and microbiological characteristics of artisanal Brazilian cheese. Brazilian cheese production was introduced and developed from the influence of immigrants considering the combination of climate, races of the animals, quality and specificity of milk, technological cheese-making processes and environmental microbiology, among other factors. It resulted in cheese products with specific physicochemical, microbiological, and sensory quality, which represent the heritage and identities of the different Brazilian regions. The production of artisanal cheese increased in many Brazilian regions, mainly in the southeast, especially due to the traditional production and innovative development of new varieties of cheese. The microbiological quality and safety of raw-milk artisanal cheese continues to be a concern and many studies have been focusing on this matter. Special attention needs to be given to the cheeses produced by raw milk, since numerous reports raised concerns related to their microbiological safety. This fact requires attention and the implementation of strict hygiene practices on the production and commercialization, besides appropriate governmental regulations and control. However, more studies on the relationship between technological processes and microbiological properties, which results in a superior culinary quality and safety of artisanal Brazilian cheeses, are needed.

Attenuated Lactococcus lactis and Surface Bacteria as Tools for Conditioning the Microbiota and Driving the Ripening of Semisoft Caciotta Cheese

This study aimed at establishing the effects of attenuated starters and surface bacteria on various features of caciotta cheese. The cheese undergoes a ripening period during which the house microbiota contaminates the surface. Conventional cheese (the control cheese [CC]) is made using only primary starters. Primary starters and attenuated (i.e., unable to grow and synthesize lactic acid) Lactococcus lactis (Lc. lactis) subsp. lactis were used to produce caciotta cheese without (ATT cheese) or with an inoculum of surface bacteria: (i) Leuconostoc lactis (Le. lactis) (LL cheese), (ii) Vibrio casei (VC cheese), (iii) Staphylococcus equorum (SE cheese), (iv) Brochothrix thermosphacta (BX cheese), and (v) a mixture of all four (MIX cheese). Attenuated Lc. lactis increased microbial diversity during cheese ripening. At the core, attenuated starter mainly increased indigenous lactococci and Lactobacillus delbrueckii group bacteria. At the surface, the main effect was on Macrococcus caseolyticus Autochthonous Le. lactis strains took advantage of the attenuated starter, becoming dominant. Adjunct Le. lactis positively affected Lactobacillus sakei group bacteria on the LL cheese surface. Adjunct V. casei, S. equorum, and B. thermosphacta did not become dominant. Surfaces of VC, SE, and BX cheeses mainly harbored Staphylococcus succinus Peptidase activities were higher in cheeses made with attenuated starter than in CC, which had the lowest concentration of free amino acids. Based on the enzymatic activities of adjunct Le. lactis, LL and MIX cheeses exhibited the highest glutamate dehydrogenase, cystathionine-γ-lyase, and esterase activities. As shown by multivariate statistical analyses, LL and MIX cheeses showed the highest similarity for microbiological and biochemical features. LL and MIX cheeses received the highest scores for overall sensory acceptability.IMPORTANCE This study provides in-depth knowledge of the effects of attenuated starters and surface bacterial strains on the microbiota and related metabolic activities during cheese ripening. The use of attenuated Lc. lactis strongly impacted the microbiota assembly of caciotta cheese. This led to improved biochemical and sensory features compared to conventional cheese. Among surface bacterial strains, Le. lactis played a key role in the metabolic activities involved in cheese ripening. This resulted in an improvement of the sensory quality of caciotta cheese. The use of attenuated lactic acid bacteria and the surface adjunct Le. lactis could be a useful biotechnology to improve the flavor formation of caciotta cheese.