N. Soultos

Chitosan effects on quality properties of Greek style fresh pork sausages.

The effect of chitosan (0.5% and 1%) added individually or in combination with nitrites (150ppm) on microbiological (Total Viable Counts, Lactic acid bacteria, Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae, yeasts and moulds), physicochemical-chemical (pH, chemical composition, lipid oxidation) and sensory properties of fresh pork sausages stored at 4°C for 28 days was investigated. Chitosan addition resulted in significant (p<0.05) inhibition of microbial growth, while nitrites did not seem to protect sausages from microbial spoilage. A gradual reduction of nitrites was observed till the end of storage, when nitrites were almost depleted in all nitrite containing samples. The rate of lipid oxidation in fresh pork sausages was significantly decreased (p<0.05) by addition of increasing levels of chitosan, while samples containing both chitosan and nitrites showed the lowest malondialdehyde (MDA) values, indicating a synergistic antioxidative effect. Consequently, the samples containing the combination of nitrites and chitosan at any level deteriorated less rapidly and were judged as more acceptable than all the other samples.

Physicochemical, microbiological and sensory attributes for the characterization of Greek traditional sausages.

Physicochemical, microbiological and sensory analyses were performed on 67 samples of Greek traditional sausages. The following physicochemical attributes were recorded: moisture 49.17%±7.05, protein 17.62%±2.67, fat 29.74%±8.02 and ash content 2.99%±0.55, moisture/protein ratio 2.83±0.5. pH value 5.48±0.49, water activity (a(w)) 0.959±0.015, total grill losses 12.81%±5.27 and fat grill losses 9.64%±4.36. The microbial counts, expressed as log(10)cfu/g, were for aerobic plate count 8.22±0.5, lactic acid bacteria 7.45±0.66, Brochothrix thermosphacta 7.02±1.21, pseudomonads 6.88±1.33 and yeasts 5.39±1.03. Mean sensory scores, on a five-point hedonic scale, were 4.46±0.63 for appearance, 4.14±0.63 for firmness, 3.80±0.97 for flavour and 4.12±0.52 for overall quality. The discriminant analysis have shown that, based on their pH and a(w) values, 74.6% of sausages were classified as easily perishable, 19.4% as perishable and 5.9% as shelf-stable. Also, 4.4% of sausages had fat content less than 15%, 23.8% from 15 to 25%, 46.2% from 25 to 35% and 25.3% more than 35%. Principal component analysis has shown that the first two components (PC1 PC2) account for 44.1% of the total variance. PC1 was related to water activity, ash, moisture and fat content, flavour, Br. thermosphacta and pseudomonads count, and to a lesser extent to cross section quality. PC2 was related to aerobic plate count, lactic acid bacteria and moisture content.

Presence of Listeria and Salmonella spp. in retail chicken in Northern Ireland

Aims: Retail packs of fresh chicken in Northern Ireland were sampled to determine the frequency with which they were contaminated with Salmonella and Listeria spp.

The effect of dietary oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage.

The effect of dietary supplementation with oregano essential oil on microbial growth of rabbit carcasses during refrigerated storage was investigated. A total of 45 weaned rabbits were separated into three equal groups with three subgroups each. One group was given the basal diet and served as control and the other two groups were administered diets supplemented with oregano essential oil at levels of 100 and 200mg/kg diet, respectively (OR100 and OR200 groups). Total viable counts, Pseudomonas spp., lactic acid bacteria, Brochothrix thermosphacta, Enterobacteriaceae and yeast and mould counts, as well as off-odours and appearance of slime were all assessed on rabbit carcasses stored at 3±1°C for 12 days. The results showed that performance parameters were not affected (p>0.05) whereas the dietary supplementation with oregano essential oil resulted in lower (p<0.05) average microbial counts on the carcasses, compared to controls, throughout storage. Dietary supplementation with oregano essential oil at 200mg/kg was more effective in inhibiting microbial growth compared with 100mg/kg. Sensory evaluation scores indicated that the carcasses obtained from OR100 and OR200 groups gave a noticeable putrid odour after days 8 and 10, respectively, whereas the control carcasses developed off-odours after the 6th day of storage. Slime formation in the controls was observed after day 6, while the OR100 and OR200 groups were just beginning to show slime after days 8 and 10, respectively.

Antibiotic resistance of Salmonella spp. and Listeria spp. isolates from traditionally made fresh sausages in Greece.

Sixty-five samples of traditionally made fresh sausages obtained from retail shops and butcher shops in northern Greece were screened for the presence of Salmonella spp. and Listeria spp. Salmonella spp. were found in 20% of the samples tested (54% Salmonella typhimurium and 46% Salmonella enteritidis). The prevalence of Listeria spp. in the samples was 26% (12% Listeria monocytogenes, 76% Listeria innocua, and 12% Listeria welshimeri). Nine of 13 Salmonella isolates were found to be resistant to ampicillin and 4 of 13 showed intermediate sensitivity; 1 of 13 was found to be resistant to chloramphenicol and 1 of 13 to tetracycline. Two strains of Salmonella typhimurum were multiresistant (resistant to ampicillin, chloramphenicol, and norfloxacin). All Listeria isolates were sensitive to the antibacterial agents tested that are commonly used for the treatment of human listeriosis.

Prevalence and Antimicrobial Resistance of Listeria monocytogenes Isolated in Chicken Slaughterhouses in Northern Greece

This study was conducted to determine the prevalence and antimicrobial resistance of Listeria monocytogenes recovered from chicken carcasses in slaughterhouses in Northern Greece. A total of 100 poultry samples (300 carcasses) were examined for Listeria spp. The samples were neck skin taken from four different slaughterhouses in Northern Greece. Forty samples were also taken from the environment of the slaughterhouses. Identification of L. monocytogenes was carried out by PCR and fingerprinting of the isolates by random amplified polymorphic DNA. L. monocytogenes strains isolated from chicken carcasses and from the environment of the slaughterhouses were also examined for antibiotic resistance. Fifty-five isolates of L. monocytogenes were tested for susceptibility to 20 antibiotics using the disk diffusion method. Listeria spp. were present in 99 of the poultry samples tested (99%), and 38 yielded L monocytogenes (38%). L. monocytogenes was also isolated in 80% of samples from the environment of a certain slaughterhouse, while the other slaughterhouses were found to be contaminated only with Listeria spp. All isolates were resistant to nalidixic acid and oxolinic acid, the majority of them to clindamycin, and only a few to tetracycline and oxytetracycline, whereas they were found to be susceptible to all other antimicrobials. The results of this study demonstrate a high prevalence of L. monocytogenes contamination in chicken carcasses, and all isolates were found to be sensitive to the antimicrobials most commonly used to treat human listeriosis.

Campylobacter in small ruminants at slaughter: Prevalence, pulsotypes and antibiotic resistance

The present study aimed to address the prevalence, pulsotypes, and antimicrobial susceptibility patterns of Campylobacter species present in sheep and goat carcasses at slaughter. In total, 851 samples were collected (343 meat surfaces, 282 ileum contents, 226 liver surfaces) and 835 Campylobacter isolates were detected in 274 out of 343 carcasses (116 kids, 110 lambs, 63 goats and 54 sheep). The contamination rates per carcass category were 78.4% for kids, 94.5% for lambs, 63.5% for goats, and 72.2% for sheep. On average, 30% of the intestinal content samples and more than 70% of carcass and liver surfaces yielded the presence of campylobacters. Multiplex-PCR and RFLP analysis identified Campylobacter coli as the most prevalent species (76.2%) followed by Campylobacter jejuni (21.4%), albeit 2.4% of selected colonies yielded the concurrent presence of both these species. Macrorestriction profiling by pulsed-field gel electrophoresis (PFGE) was applied in order to characterise a subset of isolates. SmaI-PFGE successfully clustered 222 isolates in 82 SmaI-PFGE types indicating high heterogeneity among the campylobacter isolates (67 types among 174C. coli isolates and 15 types among 48C. jejuni isolates). No carcass-type (lamb, kid, sheep, and goat) specific PFGE clusters were recognised since there was a general overlapping of PFGE patterns regarding ovine and caprine isolates. Multiple pulsotypes were simultaneously present on single carcasses in the majority of tested animals. PFGE provided data regarding the potential routes of meat and liver contamination such as spillage of faecal material and cross-contamination during slaughter. Antimicrobial susceptibility patterns of Campylobacter isolates (n=240), determined by disk diffusion method, revealed resistance to tetracycline (47.9%) followed by streptomycin (22.9%) and ciprofloxacin along with nalidixic acid (18.3%). Isolates exhibited low resistance to erythromycin (2.5%) and were susceptible to gentamicin. The findings of the present study confirm the contamination of sheep and goats at slaughter with thermophilic campylobacters and underline their potential input in the epidemiology of human campylobacteriosis.

Effect of chitosan treatments on quality parameters of fresh refrigerated swordfish (Xiphias gladius) steaks stored in air and under vacuum conditions.

The present study examined the effect of chitosan (1.0% w/v) in combination with packaging on the shelf-life of fresh swordfish steaks. Treatments included the following: A (untreated, control samples stored in air), A-CH (treated with chitosan 1.0% w/v, stored in air), VP (untreated, stored under vacuum packaging) and VP-CH (treated with chitosan, stored under vacuum packaging). VP-CH significantly affected Total Viable Counts (TVC), Pseudomonas spp., H(2)S-producing bacteria (including Shewanella putrefaciens), lactic acid bacteria and Enterobacteriaceae. Production of TMA-N and TVB-N for A-CH, VP and VP-CH swordfish samples was significantly lower than for control (A) samples at day 8 of storage. Histamine formation for all treatments was low. A-CH and VP-CH resulted in significantly lower levels of putrescine, cadaverine and tyramine (day 8) as compared to A and VP swordfish samples. Results of this study indicate that the shelf-life of swordfish steaks can be extended using, either aerobic or vacuum packaging and in combination with chitosan, by approximately 4 (A-CH), 8 (VP) and 12 (VP-CH) days. Swordfish steaks treated with chitosan and stored under VP were sensorially acceptable up to 17days. The presence of chitosan (A-CH and VP-CH) did not negatively influence the taste of cooked swordfish.

Isolation of methicillin-resistant Staphylococcus spp. from ready-to-eat fish products.

A hundred samples from ready‐to‐eat (RTE) fish products were examined for the presence and antimicrobial susceptibility of Staphylococcus spp. Staphylococci were isolated from 43% of these samples (n = 100). The identified species in the samples were Staphylococcus aureus (7%), Staphylococcus epidermidis (13%), Staphylococcus xylosus (12%), Staphylococcus sciuri (4%), Staphylococcus warneri (3%), Staphylococcus saprophyticus (2%), Staphylococcus schleiferi (1%) and Staphylococcus auricularis (1%). Two Staph. aureus (MRSA) isolates, three Staph. epidermidis (MRSE), five Staph. xylosus, four Staph. sciuri, one Staph. schleiferi and one Staph. saprophyticus isolates were resistant to oxacillin and all of them carried the mecA gene. The two MRSA isolates belonged to the spa types t316 (ST359) and t548 (ST5) and none of them was able to produce enterotoxins. Pulsed field gel electrophoresis for Staph. aureus and Staph. epidermidis isolates revealed 6 and 11 distinct PFGE types, respectively, reflecting diversity. The presence of methicillin‐resistant staphylococci, especially MRSA and MRSE, in RTE fish products may constitute a potential health risk for consumers.

Lactic acid bacteria from chicken carcasses with inhibitory activity against Salmonella spp. and Listeria monocytogenes.

This study was conducted to isolate psychrotrophic lactic acid bacteria (LAB) from chicken carcasses with inhibitory activity against strains of Salmonella spp. and Listeria monocytogenes. A total of 100 broiler samples were examined for the presence of LAB. Ninety-two LAB isolates that showed antimicrobial effects against Salmonella spp. and L. monocytogenes were further analysed to examine their LAB (Gram-positive, catalase negative, oxidase negative) and psychrotrophic characteristics (ability to grow at 7 °C). Fifty isolates were further selected and identified initially using standard biochemical tests in miniature (Micro-kits API CH 50) and then by sequencing of the 16s-23s rRNA gene boundary region (Intergenic Spacer Region). By molecular identification, these isolates were classified into 5 different LAB species: Lactobacillus salivarius, Lactobacillus reuteri, Lactobacillus johnsonii, Pediococcus acidilactici, and Lactobacillus paralimentarius. None of the isolates produced tyramine or histamine.