Biogenic Amines Content of Four Types of "Pecorino" Cheese Manufactured in Tuscany

Biogenic amines content of four types of Tuscan ewes' milk "pecorino" cheese was evaluated using HPLC-UV analysis. All cheeses were manufactured in the same dairy factory with different combinations of milk (raw or pasteurized) and type of ripening. Total biogenic amines and tyramine levels of a raw milk "pecorino" ripened five months, partly in a traditional cave, were significantly higher than those of a pasteurized milk "pecorino" with a similar ripening; and of a two months raw milk "pecorino" ripened in the dairy plant. No statistical significant difference was found when comparing total biogenic amines and tyramine contents of the same five month ripened raw milk "pecorino" with a pasteurized milk "pecorino" ripened six months, partly in a traditional "fossa." In raw milk cave-ripened and "fossa"-ripened cheeses, total biogenic amines exceeded 1000 mg/kg. In cheeses manufactured with raw milk and/or in particular ripening environments, specific hygienic cares are needed to limit biogenic amines form..

Qualitative and quantitative evaluation of biogenic amines in vitro production by bacteria isolated from ewes' milk cheeses

Studying the production of biogenic amines (BA) by cheese microbiota is important, because high BA concentrations in food represent a health risk for consumers. Qualitative screening with differential media and HPLC quantification were used to investigate the production of 8 BA (2-phenylethylamine, cadaverine, histamine, putrescine, spermidine, spermine, tryptamine, and tyramine) by 72 isolates from curd and cheese samples manufactured with raw and pasteurised ewes' milk. Enterobacteriaceae showed good putrescine and cadaverine production, both for number of positive isolates and for concentrations produced (average: 341 and 785 micrograms/ml, respectively). Among Enterobacteriaceae data are provided on BA formation by Pantoea conspicua, previously not isolated from food samples. All enterococci formed tyramine, often in high amounts (average: 1608 micrograms/ml), and many produced notable 2-phenylethylamine, putrescine, and cadaverine concentrations (average: 184, 121, and 146 micrograms/ml, respectively). BA formation by lactobacilli was overall extremely limited, with the notable exception of high tyramine concentrations produced by 1 Lactobacillus paracasei (800 micrograms/ml) and 2 Lactobacillus curvatus (> 1700 micrograms/ml), all isolated from pasteurised milk samples. Thus, undesired and technologically useful microorganisms both play a role in BA accumulation in cheeses

Prevalence, phenotypic and genetic diversity of Campylobacter in poultry fresh meat and poultry products on retail sale in Tuscany (Italy)

In this study, the prevalence of Campylobacter spp. in poultry fresh meat and ready‑to‑cook products was evaluated. Seventy‑three samples were collected at retail level from supermarkets and discount stores, obtaining 61.6% positivity. Of 133 Campylobacter isolates, 86 strains (Campylobacter coli, 58.1% and Campylobacter jejuni, 41.9%) were selected for characterisation on the basis of their SmaI and kpnI pulsed field gel‑electrophoresis (PFGE) profiles, to exclude clonal replicates. Campylobacters resulted highly resistant to tetracycline, ciprofloxacin, and nalidixic acid (79.1%, 72.1% and 65.1%, respectively); 50% of C. coli and 13.9% of C. jejuni were resistant to ciprofloxacin and erythromycin, the most important antimicrobials for human campylobacteriosis therapy. Five C. coli were resistant to 5/7 of the tested antimicrobials. HS4c was the prevailing C. jejuni serotype group (22.3%), whereas 8 other serotypes were identified in low percentages. SmaI and kpnI profiles showed a wide variability. The survey showed a high Campylobacter contamination of poultry meat and poultry products at retail level in Tuscany, Italy. A wide strains’ heterogeneity and a remarkable level of strains’ antimicrobial resistance have been reported, confirming the need for an improvement of specific preventive measures along the production chain

Microbiological and physicochemical profile of traditional <i>Salsicda toscana</i> during storage

The aim of this study was to evaluate the evolution during refrigerated storage of the main microbiological and physicochemical parameters of a traditional Italian fresh sausage, salsiccia toscana. The following parameters were analyzed at Days 0, 6 and 9 of storage: total aerobic mesophilic and psychrotrophic counts, Brochothrix thermosphacta, lactic acid bacteria, Pseudomonadaceae, Enterobacteriaceae, Escherichia coli, Micrococcaceae, yeasts and moulds, Salmonella spp., Listeria monocytogenes; pH, Aw, moisture, protein, total lipids, ash, fatty acid composition, Thiobarbituric Acid Reactive Substances, colour measurement. The results revealed a statistically significant increase in the main microbiological parameters between Days 0 and 9 of refrigerated storage, with total bacterial counts exceeding 107 CFU/g after nine days and Brochothrix thermosphacta representing the main spoilage microorganism. Among physicochemical parameters, discolouration was noted during the time of storage, with a significantly paler colour on the surface of sausages with casings after nine days of storage. Considering that the initial bacterial counts were higher than 105 CFU/g for Brochothrix thermosphacta, Pseudomonadaceae, lactic acid bacteria and Enterobacteriaceae, and that the product is traditionally purchased loose without any packaging, it is fundamental to improve the good manufacturing practices, particularly measures to control processing temperatures

Staphylococcus aureus growth and enterotoxin production in Italian caciotta cheese

To evaluate growth and enterotoxin production of Staphylococcus aureus in raw milk caciotta, an Italian soft cheese, experimental cheesemaking trials were carried out with and without a commercial starter. Two different inocula of selected enterotoxinproducing S. aureus strains were tested: high (mean value 5.03 log CFU/mL of milk) and low (mean value 3.22 log CFU/mL of milk). Uninoculated cheeses with milk containing 2.15 log CFU/mL mean value of coagulase-positive staphylococci were also examined. With higher inocul a coagulase-positive staphylococci counts reached 7.57 log CFU/g without starter and had significantly higher values after the acidification phase than those with starter (below 6.5 log CFU/g). Using an enzyme immunoassay, enterotoxins were detected in cheeses both without and with starter, but the latter showed significantly lower photometrical absorbance values than the former. In low inoculum and uninoculated cheeses without starter, coagulase-positive staphylococci maximum values were between 5 and 6 log CFU/g, without enterotoxin production. To enhance the safety of this cheese it is fundamental to strictly prevent coagulase-positive staphylococci contamination and multiplication, particularly at the primary production level, and to correctly acidify the curd by starter cultures, which can substantially limit total coagulase-positive staphylococci increase

Lactobacillus plantarum and Streptococcus thermophilus as starter cultures for a donkey milk fermented beverage

Donkey milk is recently gaining attention due to its nutraceutical properties. Its low casein content does not allow caseification, so the production of a fermented milk would represent an alternative way to increase donkey milk shelf life. The aim of this study was to investigate the possibility of employing selected Streptococcus thermophilus and Lactobacillus plantarum isolates for the production of a novel donkey milk fermented beverage. Lysozyme resistance and the ability to acidify donkey milk were chosen as main selection parameters. Different fermented beverages (C1–C9) were produced, each with a specific combination of isolates, and stored at refrigerated conditions for 35 days. The pH values and viability of the isolates were weekly assessed. In addition, sensory analysis was performed. Both S. thermophilus and L. plantarum showed a high degree of resistance to lysozyme with a Minimum Bactericidal Concentration &gt; 6.4 mg/mL for 100% of S. thermophilus and 96% of L. plantarum. S. thermophilus and L. plantarum showed the ability to acidify donkey milk in 24 h at 37 °C, with an average ΔpH value of 2.91 ± 0.16 and 1.78 ± 0.66, respectively. Four L. plantarum and two S. thermophilus were chosen for the production of fermented milks. Those containing the association S. thermophilus/L. plantarum (C1–C4) reached a pH lower than 4.5 after 18 h of fermentation and showed microbial loads higher than 7.00 log cfu/mL until the end of the storage period. Moreover, comparing the microbial loads of samples containing both species and those containing S. thermophilus alone (C5), we highlighted the ability of L. plantarum to stimulate S. thermophilus replication. This boosted replication of S. thermophilus allowed to reach an appropriate pH in a time frame fitting the production schedule. This was not observed for samples containing a single species (C5–C9). Thus, L. plantarum strains seem to be good candidates in the production of a novel type of fermented milk, not only for their probiotic potential, but also for the enhancing effect on S. thermophilus growth

Acute Delta Hepatitis in Italy spanning three decades (1991–2019): Evidence for the effectiveness of the hepatitis B vaccination campaign

Updated incidence data of acute Delta virus hepatitis (HDV) are lacking worldwide. Our aim was to evaluate incidence of and risk factors for acute HDV in Italy after the introduction of the compulsory vaccination against hepatitis B virus (HBV) in 1991. Data were obtained from the National Surveillance System of acute viral hepatitis (SEIEVA). Independent predictors of HDV were assessed by logistic-regression analysis. The incidence of acute HDV per 1-million population declined from 3.2 cases in 1987 to 0.04 in 2019, parallel to that of acute HBV per 100,000 from 10.0 to 0.39 cases during the same period. The median age of cases increased from 27 years in the decade 1991-1999 to 44 years in the decade 2010-2019 (p &lt; .001). Over the same period, the male/female ratio decreased from 3.8 to 2.1, the proportion of coinfections increased from 55% to 75% (p = .003) and that of HBsAg positive acute hepatitis tested for by IgM anti-HDV linearly decreased from 50.1% to 34.1% (p &lt; .001). People born abroad accounted for 24.6% of cases in 2004-2010 and 32.1% in 2011-2019. In the period 2010-2019, risky sexual behaviour (O.R. 4.2; 95%CI: 1.4-12.8) was the sole independent predictor of acute HDV; conversely intravenous drug use was no longer associated (O.R. 1.25; 95%CI: 0.15-10.22) with this. In conclusion, HBV vaccination was an effective measure to control acute HDV. Intravenous drug use is no longer an efficient mode of HDV spread. Testing for IgM-anti HDV is a grey area requiring alert. Acute HDV in foreigners should be monitored in the years to come

Screening of biogenic amines production by bacteria isolated from "pecorino" cheese

Biogenic amines (BA) are naturally present in many foods and beverages, especially fermented ones. Due to their toxicity, high levels of BAs in food can be a health risk. In cheese the most abundant amine is tyramine (TYR) which is the main cause of the so-called “cheese reaction”. BAs presence in food is mainly caused by aminoacids decarboxylating bacteria. Aim of the study is toevaluate BAs in vitro production by bacteria isolated from a medium-ripened “pecorino” cheese.Materials and Methods: 72 strains of potential BAs producers (Enterococci (Ec), Enterobacteriaceae (Eb) and mesophilic lactobacilli (Lb)) were isolated during the cheesemaking and the ripening phases of a “pecorino” cheese, manufactured in a dairy factory in Tuscany. Ec (34) and Lb (28) were identified by PCR [1,2,3,4], Eb (10) were identified by API 20E kit (Biomérieux). After 72h incubation in a decarboxylase broth added with 1% w/v of the precursor aminoacids, the production of 7 BAs (triptamine, 2-phenylethylamine (2PHE), putrescine (PUT), cadaverine (CAD), histamine, TYR, spermidine, spermine) was quantified on the acid extract of the cultural medium by HPLC analysis as described in a previous study [5]. All the strain tested produced BAs although in varying degrees. Overall our data on BAs production by the different microbial groups agree with previous studies [6,7,8,9]. Eb were confirmed as good PUT and CAD producers, both for number of decarboxylating strains (100% and 90% respectively) and for BAs concentrations (on average 341 and 785 µg/ml, respectively). All Ec strains produced TYR, with very high mean amounts (1608µg/ml), and many of them gave not negligible 2PHE, PUT and CAD production (on average 184, 121 and 146 µg/ml, respectively). These data agree with Ladero et al. [10] hypothesis that TYR production is genomic trait of E. faecium and E. faecalis species. On the other hand the same Authors speculated that PUT is a genomic trait of E. faecalis, while in our study 50% of the tested strains of this species showed no detectable PUT production. Indeed, other Authors reported PUT-negative strains of E. faecalis [6,9,11]. Strains that produce high amounts of BAs, although with a low prevalence, when growing to high cell counts can substantially contribute to BAs formation [9]. In view of this, it is noteworthy that, although our data confirm that Lb are overall not good BA producers, few Lb strains, isolated from pasteurized milk cheeses, produced very high amounts of TYR (810, 1766 and 1959 µg/ml). BA presence in cheeses is not solely associated with undesired bacterial groups (Eb, Ec), but technologically useful microorganisms, like Lb, could play a role in TYR accumulation in ripened cheeses, especially considering the high Lb loads reached and maintained throughout the ripening period