The characterisation of lactic acid bacteria during the fermentation of an artisan Serbian sausage (Petrovská Klobása)

Bacteriobiota and Chemical Changes during the Ripening of Traditional Fermented "Pirot 'Ironed' Sausage"

"Pirot 'ironed' sausage" (Pis) is a traditional, fermented sausage, made from different types of meat (beef and chevon), without additives or starter cultures. The physical-chemical properties (pH, water activity, fats, moisture, and protein contents) were examined in the initial meat batter stuffing and during ripening. Total bacterial diversity was examined at different time points using both culturable (traditional) and non-culturable (NGS sequencing) approaches. During the ripening, a decrease in pH value, a_w, and moisture content was observed, as well as an increase in protein and fat content. At least a two-fold significant decrease was noted for colorimetric values during the ripening period. The dominance of Proteobacteria and Firmicutes was observed in the non-culturable approach in all studied samples. During the ripening process, an increase in Firmicutes (from 33.5% to 63.5%) with a decrease in Proteobacteria (from 65.4% to 22.3%) was observed. The bacterial genera that were dominant throughout the ripening process were Lactobacillus, Photobacterium, Leuconostoc, Weissella, and Lactococcus, while Carnobacterium, Brochothrix, and Acinetobacter were found also, but in negligible abundance. Among the culturable bacteria, Latilactobacillus sakei (Lactobacillus sakei) and Leuconostoc mesenteoides were present in all stages of ripening.

The survival rate and efficiency of non-encapsulated and encapsulated native starter cultures to improve the quality of artisanal game meat sausages

This study addresses the application of native, multiple strain starter cultures for standardization of game meat sausages production. The designed starter cultures consisting of two indigenous Lactobacillus sakei and one Leuconostoc mesenteroides strains. These strains were used in both, the encapsulated and non-encapsulated form, in the game meat dough, individually or in combination, with eight treatments in total. Microbiological and physicochemical characteristics of the sausages were monitored throughout the manufacturing process, while sensory properties, biogenic amine content, and volatile compounds were evaluated in the final products. As revealed by rep-PCR, native starter cultures, encapsulated or non-encapsulated, had survived the whole sausage production process; however, to varying degrees. The application of indigenous decarboxylase negative Lb. sakei strains significantly (P < 0.05) reduced tyramine content, rapidly decreased pH and promoted the number reduction of Enterobacteriaceae and elimination of E. coli, L. monocytogenes and coliforms in ready-to-eat products. A total of 84 volatile compounds were identified by SPME-GC-MS in the eight treatment batches of game meat sausages, with only minor differences between the treatments. No significant differences in sensory traits (P > 0.05) between tested treatments were found, although treatment with the Lb. sakei strains received the highest scores for the sensory traits including cross-section, odour, hardness, aroma, and overall acceptability. Combination of multi-strain Lb. sakei starter cultures resulted in growth prevention of undesirable microbiota, reduction of tyramine content and increased the acceptability parameters of full-ripened sausages, which make them good candidates for industrial as well as artisanal application.

The Influence of Meat Batter Composition and Sausage Diameter on Microbiota and Sensory Traits of Artisanal Wild Boar Meat Sausages

In this study, the influence of meat batter composition and sausage diameter on the development of microbiota and sensory traits of traditional, spontaneously fermented wild boar meat sausages are evaluated. This research also demonstrates how principal component analysis (PCA) can be used to relate product sensory properties to particular microbial genotype and to select potential starter or adjunct culture. Generally, similar microbiological results were obtained in all types of products. The undesirable microbiota was either not detected at any sausage production stage or its number decreased below the detection limit in ripened sausages. The low growth rate of lactic acid bacteria (LAB) was consistent with the obtained pH and slow acidification rate. Although no differences in the composition of LAB species were noticed between sausage types (50S=50% wild boar meat in small casing, 50L=50% wild boar meat in large casing, 100S=100% wild boar meat in small casing), a clear separation based on LAB genotypes could be observed. Upon quantitative descriptive analysis, significant differences in sensory attributes between sausage types were established. According to the PCA, the overall acceptability traits of sausages are closely linked to one Leuconostoc mesenteroides genotype (LM_4). Of all tested technological properties, LM_4 strains showed remarkable acidification ability, lowering the pH from pH=5.41 to 3.74, and pronounced proteolytic activity on skimmed milk as well as antagonistic activity against Staphylococcus aureus (DSM 20231) and Brochothrix thermosphacta (LMG 17208). Lipolytic and haemolytic activities were not detected, and all analyzed strains were susceptible to tested antibiotics and possessed no biogenic amine genes.

Antibiotic resistance of lactic acid bacteria isolated from dry-fermented sausages

Dry-fermented sausages are meat products highly valued by many consumers. Manufacturing process involves fermentation driven by natural microbiota or intentionally added starter cultures and further drying. The most relevant fermentative microbiota is lactic acid bacteria (LAB) such as Lactobacillus, Pediococcus and Enterococcus, producing mainly lactate and contributing to product preservation. The great diversity of LAB in dry-fermented sausages is linked to manufacturing practices. Indigenous starters development is considered to be a very promising field, because it allows for high sanitary and sensorial quality of sausage production. LAB have a long history of safe use in fermented food, however, since they are present in human gastrointestinal tract, and are also intentionally added to the diet, concerns have been raised about the antimicrobial resistance in these beneficial bacteria. In fact, the food chain has been recognized as one of the key routes of antimicrobial resistance transmission from animal to human bacterial populations. The World Health Organization 2014 report on global surveillance of antimicrobial resistance reveals that this issue is no longer a future prediction, since evidences establish a link between the antimicrobial drugs use in food-producing animals and the emergence of resistance among common pathogens. This poses a risk to the treatment of nosocomial and community-acquired infections. This review describes the possible sources and transmission routes of antibiotic resistant LAB of dry-fermented sausages, presenting LAB antibiotic resistance profile and related genetic determinants. Whenever LAB are used as starters in dry-fermented sausages processing, safety concerns regarding antimicrobial resistance should be addressed since antibiotic resistant genes could be mobilized and transferred to other bacteria.

Lactic acid bacterial population dynamics during fermentation and storage of Thai fermented sausage according to restriction fragment length polymorphism analysis

This study applied restriction fragment length polymorphism (RFLP) analysis to identify the lactic acid bacteria (LAB) isolated from "mum" Thai fermented sausages during fermentation and storage. A total of 630 lactic acid bacteria were isolated from the sausages prepared using 2 methods. In Method 1, after stuffing, the sausages were stored at 30 °C for 14 days. In Method 2, after stuffing and storage at 30 °C for 3 days, the sausages were vacuum-packed and stored at 4 °C until Day 28. The sausages were sampled on Days 0, 3, 14, and 28 for analyses. The 16S rDNA was amplified and digested using restriction enzymes. Of the restriction enzymes evaluated, Dde I displayed the highest discrimination capacity. The LAB were classified and 7 species were identified For Methods 1 and 2, during fermentation, the Lactobacillus sakei and Lactobacillus plantarum species were dominant. For Method 2, the proportion of Leuconostoc mesenteroides markedly increased during storage, until L. sakei and Ln. mesenteroides represented the dominant species. The identification of LAB in the sausage samples could facilitate the selection of appropriate microorganisms for candidate starter cultures for future controlled mum production.

Bacterial ecology of PDO Coppa and Pancetta Piacentina at the end of ripening and after MAP storage of sliced product

The objective of this study was to evaluate the microbiota of two typical Italian PDO delicatessens Coppa and Pancetta Piacentina, produced in Piacenza area (Italy). Classical and molecular approaches were employed, in order to acquire knowledge on their bacterial ecology and its evolution after slicing and MAP storing; thus, the biodiversity of characteristic bacterial community, already present or introduced during such procedures, was studied in both full ripened and sliced samples from two producers (A and B) of the PDO district, packaged under MAP and stored at 2 and 8 °C for 30 days. The microbiota of the two kinds of Italian delicatessen demonstrated peculiar differences, particularly regarding the staphylococci and lactic acid bacteria (LAB) ratio. Moreover, some species within these two groups appeared to be linked to the kind of product: Leuconostoc, Lactobacillus versmoldensis and Staphylococcus saprophyticus were found only in Pancetta while Lactobacillus pentosus, Staphylococcus equorum, Staphylococcus xylosus, Staphylococcus sciuri and Macrococcus caseolyticus occurred only in Coppa. Also, both delicatessens from producer A were richer in LAB compared to those of producer B and the opposite applied for staphylococci. Interestingly, Tetragenococcus halophilus was detectable in all the samples and its presence in the sausage environment has been reported only for Capocollo. Storage did not substantially modify the microbiota composition, the only changes being the relative abundance of same sequences; S. xylosus was prevalent before slicing process and S. equorum at the end of MAP storage at both 2 °C and 8 °C. Concerning microbial contamination during the slicing process, our results suggest that the adopted procedures assure high hygienic quality standard of these typical products, with exception of a contamination by Psychrobacter psychrophilus in Coppa B. The possible origin of species rarely or never reported in the sausage environment and detected in this study is discussed.