Leuconostoc gelidum Is the Major Species Responsible for the Spoilage of Cooked Sausage Packaged in a Modified Atmosphere, and Hop Extract Is the Best Inhibitor Tested.

Cooked sausages packaged in a modified atmosphere (MAP: 20% CO2, 70% N2, <0.2% O2) with evident yellow stains were analyzed. The aims of this work were to study the microbial cause of the spoilage and to evaluate different antimicrobial compounds to prevent it. Leuconostoc gelidum was identified as the primary cause of the yellow coating in spoiled cooked sausage, as confirmed by its intentional inoculation on slices of unspoiled sausage. Leuconostoc gelidum was the main bacteria responsible for the yellow coating in spoiled cooked sausage, as confirmed by its intentional inoculation on slices of unspoiled sausage. The yellow color was also evident during growth in the model system containing cooked sausage extract, but the colonies on MRS agar appeared white, demonstrating that the food substrate stimulated the production of the yellow pigment. The spoilage was also characterized by different volatile compounds, including ketones, ethanol, acetic acid, and ethyl acetate, found in the spoiled cooked sausage packages. These compounds explained the activity of Leuc. gelidum because they are typical of heterofermentative LAB, cultivated either on food substrates or in artificial broths. Leuc. gelidum also produced slight swelling in the spoiled packages. The efficacy of different antimicrobials was assessed in model systems composed of cooked sausage extract with the antimicrobials added at food product concentrations. The data showed that sodium lactate, sodium acetate, and a combination of sodium lactate and sodium diacetate could only slow the growth of the spoiler-they could not stop it from occurring. Conversely, hop extract inhibited Leuc. gelidum, showing a minimal inhibitory concentration (MIC) of approximately 0.008 mg CAE/mL in synthetic broth and 4 mg CAE/kg in cooked sausage slices. Adding hop extract at the MIC did not allow Leuc. gelidum growth and did not change the sensorial characteristics of the cooked sausages. To our knowledge, this is the first report of the antimicrobial activities of hop extracts against Leuc. gelidum either in vitro or in vivo.

Microbial and Physico-Chemical Characterization of Cold Smoked Sea Bass (Dicentrarchus labrax), a New Product of Fishery.

The aim of this study was to investigate the microbial and physico-chemical characteristics of cold smoked sea bass (CSSB), a novel italian fish product. The microbiological analyses showed the presence of bacterial contamination from the raw material, the environment, and the production process. The microbial spoilage population was dominated by lactic acid bacteria (LAB) associated with Gram-negative fermenting bacteria, including Photobacterium phosphoreum and psychrotrophic Enterobacteriaceae. Brochotrix thermospacta and Aeromonas spp. were also present; in contrast, mould and yeast were not detected (<2 CFU/g). High levels (6-7 log CFU/g) of LAB and total bacteria count (TBC) were observed from day 45 of storage; however, their presence does not seem to have influenced the total volatile basic nitrogen (TVB-N), which always remained below 35 mg N/100 g. Consequently, the product is acceptable until day 60 of storage, considering that the malonaldehyde index (TBARS) was lower than 6.5 nmol/g. Pathogenic bacteria such as Salmonella spp. and Listeria monocytogenes were not detected. Currently, there is a growing demand for seafood due to its high quality and nutritional value. Cold smoked sea bass offers a source of macro- and micronutrients essential for the proper functioning of the human body. It is also rich in protein and omega-3 fatty acids. The WHO and FAO evaluated the benefits and risks and concluded that there is convincing evidence of health benefits from fish consumption, such as a reduction in the risk of heart failure and improved neurodevelopment in infants and young children when fish is consumed by the mother before and during pregnancy. The CSSB analysed in this study demonstrated to have health benefits due to long-chain omega-3 PUFAs and other nutrients, such as proteins, minerals, and vitamin D, which are sometimes difficult to obtain from other sources. The results show that CSSB has a high nutritional value and excellent microbial quality.

Lactobacilli, a Weapon to Counteract Pathogens through the Inhibition of Their Virulence Factors.

To date, several studies have reported an alarming increase in pathogen resistance to current antibiotic therapies and treatments. Therefore, the search for effective alternatives to counter their spread and the onset of infections is becoming increasingly important. In this regard, microorganisms of the former Lactobacillus genus have demonstrated the ability to reduce the virulence of pathogens. In addition to the production of bioactive substances, self- and coaggregation, and substrate competition, lactobacilli influence gene expression by downregulating genes associated with the virulence of pathogens. As demonstrated in many in vivo and in vitro trials, lactobacilli counteract and inhibit various virulence factors that favor pathogens, including the production of toxins, biofilm formation, host cell adhesion and invasion, and downregulation of virulence genes linked to quorum sensing. The aim of this review is to summarize current studies on the inhibition of pathogen virulence by lactobacilli, an important microbial group well known in the industrial and medical fields for their technological and probiotic properties that benefit human hosts with the potential to provide an important aid in the fight against pathogens besides use of the current therapies. Further research could lead to the identification of new strains that, in addition to alleviating adverse effects, could improve the efficacy of antibiotic therapies or play an important preventive role by reducing the onset of pathogen infections if regularly taken.

Microbial Characterization of Retail Cocoa Powders and Chocolate Bars of Five Brands Sold in Italian Supermarkets.

A microbial characterization of cocoa powder and chocolate bars of three batches of five different brands sold in Italian markets was performed. The results showed a variable microbial population consisting of mesophilic and thermophilic spore formation in both types of products. The chocolate bars were also contaminated with molds of environmental origin. Bacillus spp. and Geobacillus spp. were found in both products. The chocolate bars were also contaminated by molds belonging to the genera Penicillium and Cladosporium. The sporogenous strains mainly originate from the raw materials, i.e., cocoa beans, as the heat treatments involved (roasting of the beans and conching of the chocolate) are not sufficient to reach commercial sterility. Furthermore, the identified spore-forming species have often been isolated from cocoa beans. The molds isolated from chocolate seem to have an origin strictly linked to the final phases of production (environment and packaging). However, the level of contaminants is limited (<2 log CFU/g); the molds do not develop in both products due to their low Aw (<0.6) and do not affect the safety of the products. However, a case of mold development in chocolate bars was observed. Among the isolated molds, only Penicillium lanosocoeruleum demonstrated a high xero-tolerance and grew under some conditions on chocolate bars. Its growth could be explained by a cocoa butter bloom accompanied by the presence of humidity originating from the bloom or acquired during packaging.