Lactic acid bacteria (LAB) are considered as the main biogenic amine (BA) producers in fermented foods. These compounds derive from amino acid decarboxylation through microbial activities and can cause toxic effects on humans, with symptoms (headache, heart palpitations, vomiting, diarrhea) depending also on individual sensitivity. Many studies have focused on the aminobiogenic potential of LAB associated with fermented foods, taking into consideration the conditions affecting BA accumulation and enzymes/genes involved in the biosynthetic mechanisms. This review describes in detail the different LAB (used as starter cultures to improve technological and sensorial properties, as well as those naturally occurring during ripening or in spontaneous fermentations) able to produce BAs in model or in real systems. The groups considered were enterococci, lactobacilli, streptococci, lactococci, pediococci, oenococci and, as minor producers, LAB belonging to Leuconostoc and Weissella genus. A deeper knowledge of this issue is important because decarboxylase activities are often related to strains rather than to species or genera. Moreover, this information can help to improve the selection of strains for further applications as starter or bioprotective cultures, in order to obtain high quality foods with reduced BA content.

The growing global consumption of avocados, associated with contents including bioactive compounds with numerous health-promoting properties, is producing a large amount of agro wastes around the world. Different management approaches are available for the recovery of bioactive compounds from wastes as potential ingredients for use in the production of functional foods and nutraceuticals. Lactic acid fermentation can be used to exploit nutritional potential and add value to agro wastes. In this study, fermentations with lactic acid bacteria were carried out in avocado leaves, and the total phenolic content and the antioxidant activity were determined by DPPH and FRAP assays from hydroalcoholic extracts obtained from fermented avocado leaves. Fifteen new phenolic compounds were identified for the first time in avocado leaves by HPLC-ESI-TOF-MS. L. plantarum CECT 748T and P. pentosaceus CECT 4695T showed the highest antioxidant activity. The sum of phenolic compounds was increased by 71, 62, 55 and 21% in fermentations with P. pentosaceus CECT 4695T, L. brevis CECT 5354, P. acidilactici CECT 5765T and L. plantarum CECT 9567, respectively, while it was reduced in the fermentation with L. plantarum 748T by 21% as demonstrated by HPLC-ESI-TOF-MS. Biotransformations induced by bacterial metabolism modified the phenolic compound profile of avocado leaves in a strain-specific-dependent manner. P. pentosaceus CECT 4695T significantly increased kaempferol, P. pentosaceus 4695T, L. brevis 5354 and L. plantarum 9567 increased rutin, and dihydro-p-coumaric acid was increased by the five selected lactic acid bacteria. Total flavonoids were highly increased after fermentations with the five selected lactic acid bacteria but flavonoid glucosides were decreased by L. plantarum 748T, which was related to its higher antioxidant activity. Our results suggest that lactic acid bacteria led the hydrolysis of compounds by enzymatic activity such as glycosidases or decarboxylase and the release of phenolics bound to the plant cell wall, thus improving their bioavailability.

The wide array of spontaneously fermented sausages of the Mediterranean area can represent a reservoir of microbial biodiversity and can be an important source of new technological and functional strains able to preserve product properties, counteracting the impoverishment of their organoleptic typical features due to the introduction of commercial starter cultures. We analysed 15 artisanal salamis from Italy, Spain, Croatia and Slovenia to evaluate the microbiota composition, through culture-dependent and culture-independent techniques (i.e., metagenomic analysis), chemical–physical features, biogenic amines and aroma profile. The final pH varied according to origin and procedures (e.g., higher pH in Italian samples due to long ripening and mold growth). Lactic acid bacteria (LAB) and coagulase-negative cocci (CNC) were the dominant population, with highest LAB counts in Croatian and Italian samples. Metagenomic analysis showed high variability in qualitative and quantitative microbial composition: among LAB, Latilactobacillus sakei was the dominant species, but Companilactobacillus spp. was present in high amounts (45–55% of the total ASVs) in some Spanish sausages. Among staphylococci, S. epidermidis, S. equorum, S. saprophyticus, S. succinus and S. xylosus were detected. As far as biogenic amines, tyramine was always present, while histamine was found only in two Spanish samples. These results can valorize the bacterial genetic heritage present in Mediterranean products, to find new candidates of autochthonous starter cultures or bioprotective agents.

Latilactobacillus sakei (L. sakei), widely used as a starter culture in fermented sausages, is a species adapted to meat environments. Its ability to survive for a long time in such products is due to the exploitation of different metabolic pathways to gain energy (hexose and pentose sugar fermentation, amino acids catabolism, etc.). Since L. sakei demonstrates high phenotypic and metabolic strain biodiversity, in this work, a metabolomic approach was used to compare five strains of different origins. They were cultivated in a defined medium with glucose or ribose at two concentrations, and analyzed through nuclear magnetic resonance (¹H-NMR) spectroscopy to monitor amino acid consumptions and accumulation of organic acids and aroma compounds. The results showed that all the strains were able to use arginine, especially when cultivated with ribose, while serine was consumed mainly in the presence of glucose. Aroma compounds (i.e., diacetyl and acetoin) were mainly accumulated in samples with ribose. These aspects are relevant for starter cultures selection, to confer specific features to fermented sausages, and to optimize the fermentations. Moreover, the use of ¹H-NMR allowed the fast identification of different classes of compounds (without derivatization or extraction procedures), providing a powerful tool to increase the knowledge of the metabolic diversity of L. sakei.

The work reports a case study describing how the competition wild microflora vs. starter cultures affects the final product characteristics. This study regards an industrial lot of Ventricina, an Italian long-ripened traditional fermented sausages, produced using starter cultures. After ripening, some relevant organoleptic defects (off-odour, crust formation) were observed. Therefore, analyses were carried out in the inner and outer sausage section to explain this phenomenon. Microbiological analyses indicated a high meat batter contamination and metagenomic analyses evidenced the inability of LAB starter cultures to lead the fermentation process. The results of this not controlled fermentation were the accumulation of high levels of biogenic amines (including histamine) and the formation of a volatile profile different if compared with similar products. Indeed, the volatilome analysis revealed unusually high amounts of molecules such as isovaleric acid, propanoic acid, 1-propanol, which can be responsible for off-odours. This study demonstrated that starter culture use needs to be modulated in relation to production parameters to avoid safety and organoleptic concerns.