Lactic Acid Bacteria: Variability Due to Different Pork Breeds, Breeding Systems and Fermented Sausage Production Technology

Abstract

Changes in the ecology of the various lactic acid bacteria (LAB) species, which are involved in traditional fermented sausages, were investigated in the light of the use of different breeds of pork, each of which was raised in two different environments and processed using two different technologies. The semi-quantitative molecular method was applied in order to understand how the different species alternate over time, as well as their concentration ratios. A significant increase in LAB over the first days of fermentation characterized the trials where the starter culture wasn't added (T), reaching values of 10 7 -10 8 cfu g −1 . On the other hand, in the trials in which sausages were produced with starter addition, LAB counts had a less significant incremental jump from about 10 6 cfu g −1 (concentration of the inoculum) to 10 8 cfu g −1 . Lactobacillus sakei and Lb. curvatus were detected as the prevalent population in all the observed fermentations. Pediococcus pentosaceus, Lb. casei, Leuconostoc mesenteroides, Lactococcus garviae, and Lb. graminis also appeared, but their concentration ratios varied depending on the diverse experimental settings. The results of cluster analysis showed that a plantand breed-specific LAB ecology exists. In addition, it was also observed that the breeding system can influence the presence of certain LAB species.This phenomenon is directly proportional to the increase in temperature, in fact, the higher the temperature the more the selection pushes towards more acidifying species, with an increasingly more rapid inhibition, not only of the pathogenic and spoiling species, but also of the flavouring ones. On the other hand, sausages with longer maturation and ripening conducted at a lower temperature are characterized by low acidity and higher numbers of CNCPC resulting in a more aromatic product [12]. CNCPC participate in desirable reactions, such as lipolysis and proteolysis, which influence the aroma, besides being makers of the production and stabilization of colour, reducing nitrates in nitrite [13][14][15].LAB, therefore, play a primary role in fermented sausages production because they synthesize lactic acid, which causes the lowering of the pH value and the consequent inhibition of pathogenic bacteria and spoilage microorganisms [9,15,16]. Moreover, the acidity accelerates the reduction of the nitrite, and then the process of developing and fixing colour. Finally, LAB release substances, which affect the flavour profile, such as acetic acid, ethanol, acetoin, butanediol, and diacetyl, or having antimicrobial effect, such as bacteriocins [17][18][19].Over the last 20 years, LAB ecology has been studied by several authors, using both traditional and molecular microbiological techniques. Among them, polymerase chain reaction (PCR) and Denaturing Gradient Gel Electrophoresis (PCR-DGGE) have been extensively used both as a culture-dependent and a culture-independent method [5,[20][21][22][23][24]. High-throughput sequencing (HTS) techniques represent a relatively new approach i...

Low-Fat and High-Quality Fermented Sausages

“…During the ripening period, a significant increase in LAB and CNC count levels was observed, whereas a decrease in levels of undesirable microbial populations was detected. This is consistent with literature highlighting, once again, that useful lactic acid bacteria and CNC effectively contribute to the ripening process [ 73 , 74 , 75 ]. Moreover, data also showed that diverse spoilage bacteria, such as Brochothrix thermosphacta , Pseudomonas spp., and Coliforms persisted and were detectable until the advanced stage of ripening.…”

The Use of Less Conventional Meats or Meat with High pH Can Lead to the Growth of Undesirable Microorganisms during Natural Meat Fermentation

“…High abundance of Latl. sakei usually serves as a reassuring finding, as prevalence of this benign species is the usual state of affairs in well-performed meat fermentation processes [ 17 , 18 , 42 , 43 , 44 ]. In the present study, Latl.…”

“…curvatus became more persistent, as this species is known to prefer a higher pH than Latl. sakei [ 18 , 27 ]. This can be problematic since Latl.…”

“…In general, microbial communities are variable and difficult to predict, which is especially the case in natural fermentations [ 15 ]. Nonetheless, the consortia always consist of lactic acid bacteria (LAB) which drive acidification and coagulase-negative staphylococci (CNS) which contribute to colour and flavour formation [ 16 , 17 , 18 , 19 , 20 ]. Within the group of LAB, Latilactobacillus sakei (formerly known as Lactobacillus sakei ) and, to a lesser degree, Latilactobacillus curvatus (formerly known as Lactobacillus curvatus ) and Leuconostoc spp.…”

“…Within the group of LAB, Latilactobacillus sakei (formerly known as Lactobacillus sakei ) and, to a lesser degree, Latilactobacillus curvatus (formerly known as Lactobacillus curvatus ) and Leuconostoc spp. are most commonly encountered [ 16 , 17 , 18 ]. Whereas there are usually no specific quality or safety concerns associated with Latl.…”