Maria Francesca Iulietto

Meat spoilage: a critical review of a neglected alteration due to ropy slime producing bacteria

The shelf-life of a product is the period of time during which the food retains its qualitative characteristics. Bacteria associated with meat spoilage produce unattractive odours and flavours, discolouration, gas and slime. There are several neglected alterations that deserve more attention from food business operators and competent authorities. Ropy slime is a typical alteration of the surface of vacuum and modified atmosphere packed cooked meat products, that causes major economic losses due to the increasingly sophisticated consumer requirements. This is a review article that aims at raising awareness of an old problem of new concern, in the light of new advances and trends for understanding the aetiology of the phenomenon, the origins of contamination and the prevention measures.

Evolution under different storage conditions of anomalous blue coloration of Mozzarella cheese intentionally contaminated with a pigment-producing strain of Pseudomonas fluorescens.

Several widespread occurrences of anomalous blue coloration of Mozzarella cheese have been recorded in the United States and some European countries. Official laboratory analysis and health authorities have linked the occurrences to contamination of the processing water with strains of Pseudomonas fluorescens, although several experts questioned how to unequivocally link the blue color to the presence of the microorganism. To establish a method to determine whether a given Pseudomonas spp. strain is responsible for the defect and study the evolution of the coloration under different storage conditions, we developed an in vitro system for the evaluation of blue coloration of Mozzarella cheese intentionally contaminated with strains of P. fluorescens. The purpose of the system was to determine whether P.fluorescens strains, isolated from Mozzarella cheese with anomalous blue coloration, were able to reproduce the blue coloration under controlled experimental conditions. Thirty-six trials of experimental inoculation of Mozzarella cheese in different preservation liquids were conducted using various suspensions of P.fluorescens (P. fluorescens ATCC 13525, P.fluorescens CFBP 3150, and P. fluorescens 349 field strain isolated from blue-colored Mozzarella cheese) at different concentrations and incubated at different temperatures. Growth curves of all tested P.fluorescens strains demonstrated that after 3 d of incubation the concentration was generally >10(6) cfu/g of Mozzarella cheese incubated in either tryptic soy broth (control) or conditioning brine. Prolonged incubation for 5 d at either 20 °C or 8 °C led to concentrations up to 10(9) cfu/g of Mozzarella cheese incubated in tryptic soy broth and up to 10(8) cfu/g of Mozzarella cheese incubated in preservation liquid. All Mozzarella cheeses inoculated with the field strain of P. fluorescens, except those opened 1h after packaging and stored at 8 °C, showed the characteristic anomalous blue coloration, which appeared from 1 to 72 h after opening the packaging, and was proportional to colony count, duration of storage, and storage temperature. With the proposed system, which enabled a larger number of samples to be analyzed under controlled experimental conditions and a large amount of data to be generated in a short time, we described precisely how and under which conditions the presence of P. fluorescens in Mozzarella cheese is responsible for the anomalous blue coloration. The system will help producers intercept contaminated batches and help consumers avoid the conditions under which the defect can appear.

Growth inhibition of selected microorganisms by an association of dairy starter cultures and probiotics

Several growth curves for selected pathogens and hygiene indicators alone and vs selected dairy starter cultures (LAB) and commercial probiotics have been performed. All strains for LAB and commercial probiotics were inoculated as pure cultures into skim milk to get an initial cocci:bacilli:enterocci ratio of 2:1:1 and a concentration of approx 107 cfu mL–1 until challenge vs selected pathogens and hygiene indicators. Selected pathogens came from the collection of the Laboratorio di Ispezione degli Alimenti di O.A. or were reference strains (Escherichia coli, CSH26 K12, Staphylococcus aureus, 27R, Salmonella Derby 27, Pseudomonas fluorescens ATCC 13525, Listeria innocua ATCC 33090). Each strain was inoculated into skim milk to get an initial concentration of approx 106 cfu mL–1. Growth curves in skim milk for the following challenges were studied: i) sterility control; ii) association LAB; iii) association of LAB vs each selected pathogen or hygiene indicator; iv) selected pathogen or hygiene indicator alone. The challenges were carried out in BHI broth and in skim milk at 37°C. The highest reduction was observed in milk but in general the association of LAB and the probiotic was able to limit the growth of pathogens and hygiene indicators.

Effect of a novel starter culture and specific ripening conditions on microbiological characteristics of nitrate-free dry-cured pork sausages

Abstract This study evaluated the effect of a ‘formulation of selected dairy starter cultures and commercial probiotics’, associated with ‘specific ripening conditions’ in the production of nitrite and nitrate-free, low-acid, fermented pork sausage, produced in a small-scale plant in Umbria (Italy), and their effect on microbiological, physico-chemical and sensorial properties of the products. The following conditions were investigated throughout the experiment: (i) the use of the ‘formulation of selected dairy starter cultures and commercial probiotics’ vs no starter; (ii) the use of ‘specific ripening conditions’ vs ‘classic ripening conditions’; (iii) the use of nitrate vs nitrite and nitrate-free sausages. Sensory properties were improved and pathogen control was greater in salami to which a ‘formulation of selected dairy starter cultures and commercial probiotics’ had been added, especially under ‘specific ripening conditions’. The proposed formulation, together with the specific ripening conditions, greatly inhibited the growth of undesirable microbiota, reduced the isolation rate of pathogens and preserved the acceptability of the salami.

Fate of selected pathogens in spiked «SALAME NOSTRANO» produced without added nitrates following the application of NONIT™ technology

This study evaluated the effect of a novel formulation for starter culture associated with specific ripening conditions (NoNit™ technology) vs. a commercial» starter on the fate of selected pathogens and hygiene indicators during the fermentation and ripening of experimentally spiked salame nostrano (Italian dry sausage). Selected strains of Staphylococcus aureus 27R, Escherichia coli CSH26 K 12, Listeria innocua ATCC 33090 and Salmonella Derby 27 were inoculated into salami batter and challenged with two formulations of starter cultures (a commercial formulation and the NoNit™ formulation, consisting of Lactococcus lactis ssp. lactis, strain 340; L. lactis ssp. lactis, strain 16; Lactobacillus casei ssp. casei, strain 208 and Enterococcus faecium strain 614) with ripening at a low temperature. The proposed technology (NoNit™) performed better than the commercial formulation and limited the growth of spiked Escherichia coli, Staphylococcus aureus (including the production of enterotoxin), Salmonella Derby and Listeria innocua, yet maintained the basic product appearance and texture.

Noise assessment in slaughterhouses by means of a smartphone app

Regulation (EC) No. 1099/2009 on the protection of animals at the time of killing establishes an obligation to spare animals any avoidable suffering or stress prior to their slaughter. Although it has been pointed out that stressors also include noise, which can cause suffering and affect the quality of the meat, current legislation does not set a limit for environmental noise in slaughterhouses. This study was conducted in three slaughterhouses in central Italy to assess the environmental acoustic level using a smartphone app. The selected, medium-sized slaughterhouses for pigs and cattle were subjected to measurements using a sound-level meter (Noise Meter for iOS) during working hours at the unloading area and lairage, along the chute to the restraining pen, at the time of stunning and at the slaughter hall. For the bovine lines the average values expressed in dB ranged from 76.33 (SD 2.08) to 93.00 (SD 2.14) for abattoir 1, from 75.00 (SD 1.87) to 92.33 (SD 4.89) for abattoir 2 and from 75.67 (SD 7.09) to 88.83 (SD 4.79) for abattoir 3. For the pig lines the average values expressed in dB ranged from 77.50 (SD 3.11) to 100.33 (SD 1.53) for abattoir 1, from 83.00 (SD 2.00) to 99.75 (SD 2.63) for abattoir 2 and from 71.20 (SD 6.49) to 99.50 (SD 1.31) for abattoir 3. Data show that the pig slaughter line was always noisier than the cattle line and the slaughter hall always showed the highest values (i.e. 100 dB), when compared to the unloading area (i.e. 79 dB).

Analysis of the causes of the seizure and destruction of carcasses and organs in a slaughterhouse in central Italy in the 2010-2016 period

Meat safety and hygiene are fundamental issues for producers and endusers. To achieve these goals, the inspection of carcasses and organs at slaughter is critical. The results of post-mortem inspection are the basis for planning preventive measures against consumer risks and for limiting economic losses. In this retrospective study, the causes of the seizure and destruction of carcasses and organs were analysed at a slaughterhouse in central Italy from 2010 to 2016. 436,646 slaughtered animals were taken into consideration, for a total of 61,799 seizures (73.29% pigs, 23.87% cattle, 2.77% sheep and 0.07% horses). The organs or groups of organs that most frequently showed lesions in pigs were liver (72.38%), heart (10.77%) and pluck (10.20%); in cattle, lungs (64.86%), liver (31.20%) and stomachs (11.63%); in sheep, liver (77.15%), pluck (18.70%) and lung (3.80%); in horses, liver (75.56%), kidney (68.89%) and lung (31.11%). Among the diagnoses, parasitic diseases of the liver (ascariasis and distomatosis) were especially frequent in all species, followed by pericarditis and polyserositis in pigs and diseases affecting the respiratory system in cattle. The data obtained show that postmortem inspection is of fundamental importance for limiting risks for the consumer and ensuring meat safety. It is also evident, even more than ten years after the coming into force of the so-called hygiene package regulations, that the slaughterhouse can still act as an epidemiological observatory to provide the data needed for the development of plans for the control and eradication of the most frequent diseases in the area.

Inhibition of Listeria monocytogenes by a formulation of selected dairy starter cultures and probiotics in an in vitro model

Abstract Three strains of lactic acid bacteria (LAB) and a commercial probiotic were selected to evaluate their in vitro activity towards Listeria monocytogenes. The strains Lactococcus lactis ssp. lactis, strain 340, L. lactis ssp. lactis, strain 16; Lactobacillus casei ssp. casei, strain 208 and Enterococcus faecium UBEF-41 were inoculated into skim milk and brain heart infusion broth (BHI) to get an initial Lactococcus: Lactobacillus: E. faecium UBEF-41 ratio of 2:1:1 and a concentration of approximately 7 log cfu mL−1 until challenge vs. pathogen. L. monocytogenes ATCC 7644 was also inoculated in same media to get approximately 4 log cfu mL−1. Growth curves in skim milk and BHI at 4, 10 and 30 °C, respectively were studied for: (i) LAB formulation; (ii) L. monocytogenes and (iii) LAB vs. L. monocytogenes. When challenged with LAB, at 30 °C in milk, L. monocytogenes was not detectable after day-3 and in BHI it decreased below log cfu mL−1 after day-5. At 10 and 4 °C, in both media, L. monocytogenes counts were always significantly lower (p < .001) than the counts of L. monocytogenes alone from day-2 for milk at 4 °C and BHI at 10 °C and from day-7 for BHI at 4 °C and milk at 10 °C. In conclusion, the proposed formulation was able to limit L. monocytogenes in vitro growth, even at refrigeration temperature.

The assessment of consumer sensitivity to animal welfare: An application of Rasch Model

The sensitivity has become a mass phenomenon, still in expansion. The Euro-pean Commission, during last decade, carried out several surveys on food quality and animal welfare. This research, using data from a survey conducted on 320, respondents and applying the Rasch model on 14 selected questions (items), wants to develop a measure that appears representative of a latent variable defined as ‘Sensitivity towards Animal Welfare’. The ability to measure the individual level of this ‘Sensitivity’ therefore represents an interesting and important result, especially if there are correlations between this variable and other variables characterizing the opinions and habits of individuals, both in general and in relation to consumer decisions.

Prevalence and characterisation of shigatoxigenic Escherichia coli isolated from beef cattle fed with prebiotics

Ten Holstein Friesian calves were divided into two groups of five: one group was given prebiotics in their food, while the other group served as the control group. Every two weeks from birth up to 18 months, samples of feces were taken from the rectal ampulla to determine the concentration of E. coli. At each sampling session, three aliquots per sample were collected. The arithmetic mean was calculated and all values (converted into logs) were analysed with GraphPad InStat for analysis of variance, followed by the Tukey-Kramer test. A total of 69 E. coli strains were detected, 29 (42.03%) from treated animals and 40 (57.97%) from the control group. The isolates were analysed by PCR for the presence of the stx-1, stx-2, hly and eae genes and by the Kirby Bauer test for susceptibility to the most commonly used antimicrobials in cattle breeding. Hierarchical clustering of the isolates was done using Ward’s method. Thirty samples were positive for the stx-1 gene, 18 for stx- 2, 12 for both stx-1 and stx-2, 8 for hly, and 10 for eae. 4.3% were resistant to sulfamides, 8.6% to tetracycline, 1.4% to gentamicin, 94.6% to cephalothin, 2.8% to chloramphenicol, 13% to ampicillin, 13% to amoxicillin/clavulanic acid, 7.2% to sulphonamides, 4.3% to ceftriaxone, 5.7% to nalidixic acid, 34.7% to ticarcillin, 88.5% to erythromycin, and 5.7% to streptomycin. The isolates from the samples taken from day 210 to day 300 were grouped into a single cluster. Bacteriological examinations showed a reduction in the concentration of E. coli in the feces of the treated animals compared to the control group. The presence of strains with shigatoxigenic Escherichia coli virulence profiles and the reduction of these in the treated animal group demonstrated that diet can play an important role in reducing E. coli prevalence in cattle.