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We investigated the impact of chitosan and oregano essential oil (EO) individually or in combination on the quality of eel fillets in vacuum packaging (VP) and stored under refrigeration (...

The present study examined the effect of natural antimicrobials: Chitosan, thyme oil and their combination, on the shelf- life of smoked eel fillets stored under vacuum packaging (VP) at 4°C. Based on sensory odor data smoked eel fillets had a shelf- life of 35 (control), 42 (thyme treated and >49 (thyme, chitosan-thyme treated) days. The thiobarbituric acid value (TBA) value of the control eel sample was significantly higher than the chitosan-thyme-treated eel samples. The use of chitosan singly, or in combination with thyme oil reduced lipid oxidation (TBA) of the smoked eel samples. A trimethylamine nitrogen (TMA-N) value of 10 mg N/100 g, could be suggested as an indication of smoked eel spoilage initiation. Control and treated eel reached total volatile basic nitrogen (TVB-N) values of 13.1-31.5 mg N/100 g below the maximum permissible level of TVB-N in fish and fishery products. Eel samples reached the value of 7.0 log cfu/g (Total Plate Count,TPC) on days 35 (smoked) and 42 (thyme treated), whereas both chitosan and chitosan-thyme treated eel samples never reached this limit value. Results of our study show thyme or chitosan (singly, or in combination) inhibit the growth of mesophilic bacteria and extend the shelf- life of smoked eel. Deanship of Scientific Research at King Saud University

In this study, we examined the antimicrobial effects of citrus extract (Citrox(®)) and chitosan on lactic acid bacteria (LAB) and the pathogens Escherichia coli O157:H7 and Salmonella enterica on turkey meat during storage under vacuum packaging (VP) at 4 and 10 °C. We also examined the effects of Citrox and chitosan on pathogen contamination in tryptic soy broth (TSB). Chitosan alone or in combination with Citrox inhibited the growth of endogenous LAB in turkey meat, whereas citrus extract did not cause a major reduction in bacterial density. Citrus extract combined with chitosan yielded the lowest mesophilic total viable counts (TVCs), irrespective of temperature, showing major declines in all treated turkey samples from days 0-21 of storage. The shelf-lives of untreated, Citrox-treated, and chitosan and Citrox/chitosan-treated samples (as determined by TVC and sensory data) were 13, 17, and >21 days, respectively, at 4 °C for VP turkey. The addition of Citrox was more effective against S. enterica than E. coli in turkey, causing reductions of >0.5 and 2 log cfu/g at 4 and 10 °C, respectively, after 21 days of storage. Interestingly, the addition of chitosan had a significant inhibitory effect on E. coli at 4 °C and S. enterica at 10 °C as compared with the control (inoculated samples) resulting in dramatic reductions in E. coli (2 log) and S. enterica (5 log) cell counts on day 21. Of all the treatments examined, citrus extract in combination with chitosan showed an additive inhibitory effect against both pathogens, reducing E. coli and S. enterica populations, by approximately 2.7 or 4.5 and 2.2 or 5.6 log cfu/g, respectively, at 4 and 10 °C on day 21 of storage.

Controlling spoilage of the popular ethnic marinated beef “Shawarma” is crucial to achieve high quality, extend shelf-life, reduce food waste and meet the need of the globalized supply chain. Active essential oil (EO) components (thymol and carvacrol) were added at 0.4% and 0.8% (w/w) to preserve marinated beef, stored under aerobic or vacuum packaging. Microbiological and sensory (odor) parameters were assessed during 21 days at 4 °C. The treatments with higher EO concentration achieved higher antimicrobial activity than the lower ones and significantly reduced the mesophilic total viable count (TVC), lactic acid bacteria (LAB), Brochothrix thermosphacta, Pseudomonas spp., total coliforms, Escherichia coli, yeasts and molds. The higher EO concentration extended the microbiological shelf-life by 6 days, as judged by TVC and compared to the controls (aerobic and vacuum packaging) but was unacceptable sensorially. The lower EO concentration increased the microbiological shelf-life by 3 days and the sensorial shelf-life by 9 and > 12 days, under aerobic and vacuum conditions, respectively.

The study aimed to determine D and z-values of Escherichia coli O157:H7 strains and Salmonella spp. in camel lean meat burger (CM) and camel meat burger with hump fat (CMF). Two E. coli O157:H7 strains, S. Typhimurium and S. Copenhagen were mixed individually with CM and CMF samples, placed in sterile pouches and exposed to water bath heat treatment at 55, 57.5, 60, 62.5, 65, 67.5 °C for different time intervals. The D-values of E. coli O157:H7 161-84 in CM burgers at 60, 62.5, 65, 67.5 °C were 53.5, 20.1, 8.3, and 3.0 s, respectively, while the values in CMF samples were 76.0, 25.9, 9.9 and 4.1 s, respectively. The D-values of S. Typhimurium in CM burgers at 55, 57.5, 60, 62.5 °C were 349.2, 70.5, 18.4 and 6.7 s, respectively, while the values in CMF were 512.1, 77.1, 21.1 and 8.4 s, respectively. There was a significant (P

The present study evaluated the use of nisin, natamycin and/or their combination as antimicrobial treatments to improve the shelf-life of Galotyri cheese. Samples were treated with nisin [N1 (100 IU/g), N2 (200 IU/g)], natamycin [NA1 (0.01% w/w), NA2 (0.02% w/w)] and their combinations N1-NA1, N1-NA2, N2-NA1 and N2-NA2. A Galotyri control (N0) cheese sample was also tested (absence of nisin or natamycin). Single N1, N2 treatments reduced lactobacilli and lactococci populations, but their effect was less pronounced, as compared to the combined nisin-natamycin treatments between days 14 and 28 of storage. Yeast populations in natamycin-treated Galotyri cheese samples or those additionally treated with nisin were significantly suppressed throughout the entire period of storage. Control N0 or N1, N2 treated samples received significantly lower acceptability scores, as compared to either natamycin or natamycin-nisin treated samples. Natamycin, added either singly or in combination with nisin, efficiently suppressed fungal growth in the Galotyri cheese. The observed shelf life of Galotyri, based on overall acceptability data, was the longest for N1-NA1, N1-NA2, N2-NA1 and N2-NA2 cheese samples (>28 days) followed by the N1, N2 treated samples (18-19 days) whereas for the control N0 a shelf-life of 14-15 days was attained.

In this study fresh turkey meat was packaged under vacuum and stored at 2 °C. The following lots were used: T (control); stored under vacuum packaging (VP), T-RO; stored under VP, treated with rosemary oil 0.25% v/w, T-CH; stored under VP, treated with chitosan 1.5% w/v, and T-CH-RO; stored under VP, treated with chitosan 1.5% w/v and rosemary oil 0.25% v/w. Of the microbial microflora species examined, irrespective of treatment, lactic acid bacteria (LAB) constituted the most abundant group. Interestingly, total plate counts (TPCs) and LAB counts, exceeding the limit value of 7 log cfu/g, in T and T-RO turkey samples coincided with low taste scores (5 and 6, respectively) on days 12 and 18 of storage. The shelf-life was approximately 10, 17–18 and > 21 days for the control (T), T-RO, T-CH and T-CH-RO turkey samples, respectively. Thus, a shelf-life extension of 7–8 and > 11 days was obtained for T-RO and T-CH, and T-CH-RO turkey samples, respectively. The presence of chitosan in T-CH and T-CH-RO samples did not negatively influence the taste of cooked turkey meat.

The qualitative and quantitative profile of biogenic amines (BA) in 50 samples of dry fermented sausages sold in Greek retail markets were determined by HPLC. Putrescine, cadaverine, tryptamine, β-phenylethylamine spermidine, spermine were analysed by UV detection after pre-column derivatization with benzoyl chloride, whereas tyramine and histamine were analysed by fluorescence detection after post-column derivatization with o-phthaldialdehyde (OPA). With the exception of spermidine and spermine a wide variation of BA levels was observed among the samples. Of the BA examined, tyramine, putrescine, histamine and cadaverine showed high concentrations ranging from: 0 to 510 mg/kg (median: 197.7 mg/kg), 0 to 505 mg/kg (median: 96.5mg/kg), 0 to 515 mg/kg (median: 7.0mg/kg) and 0 to 690 mg/kg (median: 3.6 mg/kg), respectively. The histamine content of 28% of the samples exceeded the toxicity limit of 100mg/kg set for histamine in some fish species. Levels of tryptamine and β-phenyl-ethylamine never exceeded 50 and 29 mg/kg, respectively. Results of the present study suggest that the amounts of BA in dry fermented sausages, sold in Greek retail markets, may pose a potential health risk for sensitive individuals or for those undergoing classical monoamine oxidase inhibiting (MAOI) drug therapy.

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., H2S-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 17 days. The presence of chitosan (A-CH and VP-CH) did not negatively influence the taste of cooked swordfish.

In the present study, natural antimicrobials chitosan and thyme, and their combination, were evaluated for their effect on the shelf life of a ready-to-cook (RTC) chicken-pepper kebab (skewer) stored under modified atmosphere packaging (MAP) conditions at 4 +/- 0.5 degrees C for 14 days. The following treatments were examined: control samples stored under aerobic packaging (A), samples stored under MAP (M), samples treated with 1.5% chitosan (vol/wt) and stored under MAP (M-CH), samples treated with 0.2% thyme essential oil (vol/wt) (M-T), and samples treated with 1.5% chitosan (vol/wt) and 0.2% thyme essential oil (vol/wt) and stored under MAP (M-CH-T). Treatment M-CH-T significantly affected aerobic plate counts and counts of lactic acid bacteria. Pseudomonas spp., Brochothrix thermosphacta, Enterobacteriaceae, and yeasts and molds during the entire storage period. Similarly, lipid oxidation of the RTC product was retarded (M-CH-T treatment) during storage, whereas redness was maintained in M-T. M-CH, and M-CH-T samples. Based primarily on sensory data (taste attribute), M-CH and M-T treatments extended RTC product shelf life by 6 clays, whereas M-CH-T treatment resulted in a product with a shelf life of 14 days that maintained acceptable sensory characteristics (shelf life of the control was 6 days). Journal of Food Protection

The present study examined the effect of natural antimicrobials: chitosan, thyme and their combination, on the shelf-life of a Ready to Cook (RTC) chicken-pepper kebab (skewer) stored under aerobic conditions at 4 +/- 0.5 degrees C for a period of 12 days. Treatments examined in the present study were the following: A (control samples, untreated), A-CH (chitosan: 1.5% v/w), A-T (thyme essential oil; 0.2% v/w) and A-CH-T (chitosan; 1.5% v/w and thyme essential oil; 0.2% v/w). The shelf-life of the samples was determined using both microbiological and sensory analyses. Among the microorganisms examined, pseudomonads were the most resistant group towards the combined application of chitosan and thyme oil (ca. 1.5 log cycle reduction) while Lactic acid bacteria (LAB), Brochothrix thermosphacta and Enterobacteriaceae were the most sensitive to the combined action of these two agents (2-3 log cycle reduction). Yeasts-moulds were also part of the natural microbial association of the RTC product, with A-CH-T treatment suppressing effectively their growth during the entire period of storage. Treatments A-CH and A-CH-T resulted in lower pH values as compared to the control (A) samples. Of the treatments examined in the present study, A-CH-T, gave a "spicy", desirable and pleasant (organoleptically acceptable) RTC product. Based primarily on sensory data (taste attribute) A-CH, A-T and A-CH-T treatments extended the product's shelf-life by ca. 4 and 6 days, respectively, as compared to the control sample. (C) 2009 Elsevier Ltd. All rights reserved. Food Microbiology

The present study examined the effect of natural antimicrobials: Ethylenediaminetetraacetate (EDTA), lysozyme, rosemary and oregano oil and their combinations, on the shelf-life of semi cooked coated chicken fillets stored under vacuum packaging (VP), at 4 ± 0.5 °C for a period of 18 days. The treatments of semi cooked coated chicken fillets examined in the present study were the following: Air-packaged (A, control samples), vacuum-packaged (VP), VP with EDTA–lysozyme solution 1.50% w/w, (VP + EL), VP with rosemary oil 0.20% v/w, (VP + R), VP with oregano oil 0.20% v/w, (VP + O), VP with EDTA–lysozyme solution and rosemary oil (VP + EL + R) and finally VP with EDTA–lysozyme and oregano oil (VP + EL + O). The shelf-life of the samples was determined using both microbiological and sensory analyses. Among the antimicrobial combinations examined in the present study, the treatments VP + EL + R and VP + EL + O were the most effective against the growth of Gram-negative, Gram-positive bacteria, and to a lesser extent on yeasts. Based on both microbiological (TVC data) and sensory (taste attribute) analyses, treatments: VP and VP + O gave a shelf life extension of 6 days, whereas treatments VP + EL + R and VP + EL + O produced a shelf-life extension of 7–8 days, as compared to the control samples. Industrial Relevance The present research has highlighted the use of natural antimicrobial treatment combinations, including: EDTA, lysozyme, rosemary and oregano oil and their combinations, in the extension of shelf-life of semi cooked coated chicken fillets stored under vacuum packaging at 4 °C for a period of 18 days. Establishing, the determination of the shelf-life of fresh poultry and products represents a challenge for food companies as poultry meat has a short shelf-life, which causes substantial practical problems for its distribution. Therefore, knowledge of natural preservatives, that can be used as alternatives to chemical additives, that could extend the products' shelf life can have an important economic feedback by reducing losses attributed to spoilage and by allowing the products to reach distant and new markets. This study has shown that combinations of natural antimicrobials can extend the shelf-life of the product.

The present study evaluated the effect of thyme essential oil and packaging on fresh Mediterranean swordfish fillets during storage at 4 °C. Treatments in the present study included the following: air (A), modified atmosphere packaging (M), air with thyme oil (AT) and MAP with thyme oil (MT). Of the physicochemical parameters examined, TBA values for A and M swordfish samples were variable, indicative of no specific oxidative rancidity trend, whereas MT treatment inhibited lipid oxidation in swordfish samples during storage. On the basis of microbiological and sensory data, TMA-N and TVB-N limit values of acceptability for Mediterranean swordfish, of ca. 3.72 and 24.5 mg N/100 g, for the initiation of fresh Mediterranean swordfish spoilage, may be proposed. Of the treatments used in the present study, MT and M were the most effective for the inhibition of pseudomonads and H 2 S-producing bacteria in swordfish. Lactic acid bacteria and Enterobacteriaceae (to a lesser extent) were also found to be part of the natural microbial flora of swordfish, irrespective of packaging treatment. Based primarily on sensory data, the shelf-lives of fresh refrigerated Mediterranean swordfish were 8 and 13 days under aerobic and MAP conditions, respectively. Addition of 0.1% thyme essential oil extended the product’s shelf-life under aerobic conditions by 5 days, whereas the combination of MAP and thyme oil resulted in a significant shelf-life extension of the swordfish fillets, i.e. by approximately 7½ days, according to sensory data, as compared to the control sample.

The present work evaluated the effect of modified atmosphere packaging (MAP) on quality characteristics and shelf-life extension of the whey cheese ''Myzithra Kalathaki'' using microbiological, chemical and sensory analyses. Myzithra cheese was packaged in four different atmospheres: vacuum, 20% CO2/80% N-2 (M-1), 40% CO2/60% N-2 (M-2) and 60% CO2/40% N-2 (M-3); identical cheese samples were packaged in air, taken as controls. All cheese samples were kept under refrigeration (4 +/- 0.5 degrees C) for 45 days. Of the four atmospheres, the M-2 and M-3 gas mixtures were the most effective for inhibiting growth of aerobic microflora and psychrotrophs in cheese samples until days 40 and 33 of refrigerated storage, respectively. Lactic acid bacteria (LAB) were part of the cheese microflora becoming dominant toward the end of the storage period regardless of packaging conditions. Enterobacteriaeceae were also part of the cheese microflora being effectively inhibited after day 35 of storage. Molds and yeasts were also totally inhibited by MAP (M-2 and M-3) gas mixtures throughout the entire storage period. Of the chemical quality indices determined, lipid oxidation varied below 0.005 absorbance at 532 nm for all treatments, except control samples for which absorbance values of 0.02 were recorded after 35 days of storage. Lipolysis did not vary significantly with type of packaging treatment while proteolysis values showed and increasing trend up to day 25 of storage and then decreased toward the end of the storage period. Sensory evaluation (odour and taste) showed that Myzithra cheese packaged under MAP (M-2 and M-3) retained good sensory characteristics for 30 days of storage while control samples were sensorily unacceptable after 10-12 days of storage. (C) 2007 Swiss Society of Food Science and Technology. Published by Elsevier Ltd. All rights reserved. Lwt-Food Science and Technology

The present work evaluated the effect of air, vacuum and modified atmosphere packaging (MAP) on the shelf-life of chilled Mediterranean swordfish (Xiphias gladius). Fresh swordfish slices were stored in air, under vacuum and MAP (40%/30%/30%, CO(2)/N(2)/O(2)) under refrigeration (4 degrees C) for a period of 16 days. Of the three treatments used (vacuum, MAP and air), both MAP and vacuum packaging (VP) were the most effective for inhibiting growth of aerobic microflora in swordfish samples until days 9-10 of refrigerated storage. Of the microbial species determined, both Pseudomonas spp. and H(2)S-producing bacteria (including Shewanella putrefaciens) were dominant in swordfish samples stored in air, whereas growth of these species was partly inhibited under VP and MAP conditions. Lactic acid bacteria (LAB) and Enterobacteriaceae were also found to be members of the final swordfish microbial flora, irrespective of packaging conditions throughout the entire storage period. Of the chemical freshness indices determined, thiobarbituric acid (TBA) values were variable in swordfish samples, indicative of no specific oxidative rancidity trend. Trimethylamine nitrogen (TMA-N) values of swordfish samples stored in air, under VP and MAP exceeded the limit value of 5mgN/100g fish muscle after days 7, 8-9 and 11 days of storage, respectively. In a similar trend, total volatile basic nitrogen (TVB-N) for swordfish samples stored in air, under VP and MAP exceeded the limit value of 25mgN/100g fish muscle after 7-8, 10 and 12 days of storage, respectively. Sensory analyses (odor and taste attributes) indicated a shelf-life of ca. 7 days for air, 9 days for VP and 11-12 days for the MA-packaged swordfish samples.

The present study evaluated the use of nisin as an antimicrobial treatment for shelf-life extension of Galotyri, a Greek soft acid-curd cheese, stored aerobically under refrigeration for a period of 42 days. Three different treatments were tested: N0, control sample with no nisin added; N1, 50 IU g −1 nisin; and N2, 150 IU g −1 nisin, the latter two treatments added post-production to the Galotyri cheese. Of all microorganisms enumerated, lactobacilli, lactococci and yeasts were the groups that prevailed in cheese samples, irrespective of antimicrobial treatment. Based primarily on sensory evaluation (appearance and taste) and a microbiological acceptability limit for yeasts (5 log cfu g −1 ), the use of nisin treatments extended the shelf-life of fresh Galotyri cheese stored at 4 °C by ca. 7 days (N1) and 21 days (N2) with cheese maintaining good sensory characteristics.

The combined effect of oregano essential oil (0.1% and 1% w/w) and modified atmosphere packaging (MAP) (30% CO2/70% N2 and 70% CO2/30% N2) on shelf-life extension of fresh chicken meat stored at 4 degrees C was investigated. The parameters that were monitored were: microbiological (TVC, Pseudomonas spp., lactic acid bacteria (LAB), yeasts, Brochothrix thermosphacta and Enterobacteriaceae), physico-chemical (pH, TBA, color) and sensory (odor and taste) attributes. Microbial populations were reduced by 1-5 log cfu/g for a given sampling day, with the more pronounced effect being achieved by the combination of MAP and oregano essential oil. TBA values for all treatments remained lower than 1 mg malondialdehyde (MDA) kg(-1) throughout the 25-day storage period. pH values varied between 6.4 (day 0) and 5.9 (day 25). The values of the color parameters L*, a* and b* were not considerably affected by oregano oil or by MAP. Finally, sensory analysis showed that oregano oil at a concentration of 1% imparted a very strong taste to the product for which reason these lots of samples were not scored. On the basis of sensory evaluation a shelf-life extension of breast chicken meat by ca. 3-4 days for samples containing 0.1% oregano oil, 2-3 days for samples under MAP and 5-6 days for samples under MAP containing 0.1% of oregano oil was attained. Thus oregano oil and MAP exhibited an additive preservation effect.

“Anthotryros” cheese was packaged under vacuum (VP) or modified atmosphere (MAP) and stored at 4 or 12 °C. MAP mixtures were 30%/70% CO2/N2 (M1) or 70%/30% CO2/N2 (M2), while VP was taken as the control sample. Microbiological results showed that M1 and M2 delayed microbial growth compared with VP samples. Of the two modified atmospheres, gas mixture M1 was the most effective for inhibition of growth of mesophilic bacteria. Based primarily on sensory evaluation, the use of both MAP conditions extended the shelf-life of fresh Anthotyros cheese stored at 4 °C by ca. 10 days (M1) or 20 days (M2) compared with VP, and by ca. 2 days (M1) and 4 days (M2) at 12 °C, with cheese maintaining good sensory characteristics.

The present work evaluated the possible role of volatile amines as indicator(s) of poultry meat spoilage. Fresh chicken meat (breast fillet) was packaged in four different atmospheres: air (A), vacuum (VP) and two modified atmospheres (MAs), namely M1, 30%/65%/5% (CO2/N2/O2) and M2, 65%/30%/5% (CO2/N2/O2). All chicken samples were kept under refrigeration (4 ± 0.5 °C) for a period of 15 days. Of the four treatments, the VP and M1 and M2 gas mixtures were the most effective for delaying the development of aerobic spoilage microbial flora. Pseudomonas spp. in chicken samples stored under M2 gas mixture and VP were significantly lower than all the other samples after 15 days of storage. Of the remaining bacterial species examined, lactic acid bacteria (LAB), Brochothrix thermosphacta, were dominant in the microbial association of both aerobically- and MA-packaged chicken, while yeasts contributed to a much lesser extent in the final microbial flora of chicken meat. On the basis of microbiological data (TVC), shelf-life extensions of 2, 4 and 9-10 days were achieved by VP and M1 and M2 gas mixtures. Results of the present work showed that the limit of sensory acceptability (a score of 6) was reached for the aerobically, vacuum-packaged and M1 gas mixture chicken samples approximately on days 6-7 and 9-10, respectively. Based on sensory (taste) analysis and with regard to chicken spoilage and freshness, TMA-N and TVB-N limit values of acceptability, namely 10.0 mg N/100 g and 40 mg N/100 g for chicken samples stored in air, may be proposed as the upper limit values for spoilage initiation of fresh chicken meat stored aerobically. Interestingly, the M2 gas mixture sample did not reach these limit values throughout the 15 day storage period. The formation of volatile amines during chill storage of chicken meat, under the packaging conditions examined in the present study, seemed to be in good agreement with the increase in microbiological count (TVC) and sensory taste score except for the M2 gas mixture.

Changes in volatile profiles of whole pasteurized milk stored under fluorescent light at 4 °C, packaged in different containers were monitored for a period of 7 days in a study designed to differentiate between light-induced oxidative and purely autoxidative effects related to packaging material. Changes in volatiles were measured using solid-phase microextraction-gas chromatography/mass spectroscopy, while microbiological and sensory analyses were used to assess milk quality. Two distinct patterns of milk flavour deterioration were observed. In light-exposed samples, a light-induced oxidation mechanism prevailed while in light-protected samples, an autoxidation mechanism was apparent. Under both conditions, the concentration of selected odorous compounds increased with storage time. Microbiological data correlated poorly with both sensory and GC/MS data. Sensory data correlated well with selected volatile compounds pointing to dimethyl disulphide, pentanal, hexanal and heptanal as potential markers of fresh milk quality. Based on sensory analysis, the optimal shelf life of the whole pasteurized milk used in this study was approximately 5 days.

This study evaluated survival of Listeria spp. (four-strain mixture of Listeria innocua plus a non-virulent Listeria monocytogenes strain) and Escherichia coli O157:H7 strain ATCC 43888 during fermentation and ripening of Greek dry sausages formulated from meat and pork fat trimmings previously inoculated with ca. 6 log cfu g −1 of the target bacteria and then irradiated in frozen (−25 °C) blocks at doses of 0 (control), 2 or 4 kGy. Irradiation of the trimmings at 2 kGy reduced initial contamination of the sausage batter with Listeria and E. coli O157:H7 by 1.3 and 2.0 log cfu g −1 , respectively, while the corresponding reductions at 4 kGy were 2.4 and 5.5 log cfu g −1 , respectively. In fact, E. coli O157:H7 was eliminated by 4 kGy at formulation (day 0) as compared to 7 and 21 days of ripening in samples treated at 2 and 0 kGy, respectively. Despite the fact that irradiation assisted in faster declines of listeriae during fermentation, these bacteria showed a strong tailing during ripening, which was more pronounced in sausages irradiated at 4 kGy. As a consequence, survival of Listeria in 28-day sausages irradiated at 2 or 4 kGy was ca. 2 log cfu g −1 and similar ( P > 0.05) to that in non-irradiated samples. Irradiation showed promise for controlling E. coli O157:H7 and, to a lesser extent, L. monocytogenes in fermented sausages.

The effect of ozonation in aqueous solution (O3 concentration=1 mg/l, time of ozonation: 60 and 90 min) on the shelf-life of shucked, vacuum-packaged mussels, stored under refrigeration was studied by monitoring the microbiological, chemical and sensory changes occurring in mussel samples, for a period of 12 days. Non-ozonated vacuum-packaged mussels served as the control sample. Ozonation affected populations of bacteria namely, aerobic plate count (APC) (0.7–2.1 log cycle reduction), Pseudomonas spp. (0.5–1.1 log cycle reduction) and H2S-producing bacteria (1.1–2.5 log cycle reduction), Brochothrix thermosphacta (0.3–1.4 log cycle reduction), lactic acid bacteria (0.3–0.8 log cycle reduction) and Enterobacteriaceae (0.5–1.5 log cycle reduction). The effect of ozonation was more pronounced at the longer time of ozonation. Of the chemical indicators of spoilage monitored, trimethylamine values of all mussel samples remained relatively low throughout the entire storage period, attaining values of 7.5, 6.0 and 6.4 mg N/100 g for the control and ozonated for 60 and 90 min samples, respectively, on day 12 of storage. Total volatile basic nitrogen (TVB-N) values similarly remained relatively low (⩽20 mg N/100 g) until day 6 of storage, and increased to 31.9, 24.2 and 26.9 mg N/100 g mussel meat for the control and ozonated for 60 and 90 min samples, respectively, on day 12 of storage. Initial TBA values were surprisingly high (30–35 mg MA/kg) and decreased to 23.0, 21.7 and 13.3 mg MA/kg mussel meat on day 12 of storage for the control and the ozonated for 60 and 90 min samples, respectively. Sensory evaluation (odor, taste and texture) of cooked mussels showed a good correlation with bacterial populations. On the basis of sensory analyses, a shelf-life of 12 days was obtained for vacuum-packaged mussels ozonated for 90 min as compared to a shelf-life of 9 days for the control sample.

Galotyri is a traditional Greek soft acid-curd cheese, which is made from ewes’ or goats’ milk and is consumed fresh. Because cheese processing may allow Listeria monocytogenes post-process contamination, this study evaluated survival of the pathogen in fresh cheese during storage. Portions (0.5 kg) of two commercial types ( −1 of a five-strain cocktail of L. monocytogenes and stored aerobically at 4°C and 12°C. After 3 days, average declines of pathogen's populations (PALCAM agar) were 1.3–1.6 and 3.7–4.6 log cfu g −1 in cheese samples for the low and high inocula, respectively. These declines were independent ( P >0.05) of the cheese type or the storage temperature. From day 3, however, declines shifted to small or minimal to result in 1.4–1.8 log cfu g −1 of survivors at 28 days of storage of all cheeses at 4°C, indicating a strong “tailing” independent of initial level of contamination. Low (1.2–1.7 log cfu g −1 ) survival of L. monocytogenes also occurred in cheeses at 12°C for 14 days, which were prone to surface yeast spoilage. When ca. 3 log cfu g −1 of L. monocytogenes were inoculated in laboratory scale prepared Galotyri of pH ≅4.4 and ≅3% salt, the pathogen died off at 14 and 21 days at 12°C and 4°C, respectively, in artisan type cheeses fermented with the natural starter. In contrast, the pathogen survived for 28 days in cheeses fermented with the industrial starter. These results indicate that L. monocytogenes cannot grow but may survive during retail storage of Galotyri despite its low pH of or slightly below 4.0. Although contamination of Galotyri with L. monocytogenes may be expected low ( −1 ) in practice, that long-term survival of the pathogen in commercial cheeses was shown to be unaffected by the artificial contamination level (3 or 7 logs) and the storage temperature (4°C or 12°C), which should be a concern.

The effect of gutting and filleting on the formation of biogenic amines and its relation to microbiological and sensory attributes in ice-stored sea bass (Dicentrarchus labrax) was studied. Pseudomonads, H2S-producing bacteria, Brochothrix thermosphacta and to a lesser extent Enterobacteriaceae were the dominant micro-organisms in whole, gutted and filleted sea bass. Higher populations (P Finally, no histamine was present in both whole and gutted sea bass, whereas interestingly, for filleted sea bass samples, levels of histamine increased after day 9 of storage but remained low (

The effect of gamma irradiation (1 and 3 kGy) on the shelf-life of salted, vacuum-packaged sea bream ( Sparus aurata ) fillets stored under refrigeration was studied by monitoring the microbiological, chemical and organoleptic changes occurring in fish samples. Non-irradiated, salted, vacuum-packaged fish served as control samples. Irradiation affected populations of bacteria, namely, Pseudomonas spp., H 2 S-producing bacteria, Brochothrix thermosphacta , Enterobacteriaceae and lactic acid bacteria. The effect was more pronounced at the higher dose (3 kGy) applied. Of the chemical indicators of spoilage, trimethylamine (TMA) values of non-irradiated, salted sea bream increased slowly to 8.87 mg N (100 g) −1 flesh (whereas for irradiated, salted samples significantly lower values were obtained, reaching a final TMA value of 6.17 and 4.52 mg N (100 g) −1 flesh at 1 and 3 kGy, respectively (day 42). Total volatile base nitrogen values increased slowly attaining a value of 60.52 mg N (100 g) −1 for non-irradiated, salted sea bream during refrigerated storage whereas for irradiated fish, lower values of 48.13 and 37.21 mg N (100 g) −1 muscle were recorded at 1 and 3 kGy, respectively (day 42). Thiobarbituric acid values for irradiated, salted sea bream samples were higher than respective non-irradiated (salted) fish, and increased slowly until day 28 of storage reaching final values of 1.01 (non-irradiated, salted), 2.15 (1 kGy) and 3.26 mg malonaldehyde kg −1 flesh (3 kGy), respectively (day 42). Sensory evaluation (taste) showed a reasonably good correlation with bacterial populations. On the basis of sensorial evaluation, a shelf-life of 27–28 days was obtained for vacuum-packaged, salted sea bream irradiated at 1 or 3 kGy, compared to a shelf-life of 14–15 days for the non-irradiated, salted sample.

Chemical and sensory changes in low fat (15 g kg(-1)) pasteurized milk stored under fluorescent light at 4degreesC in 500 mL bottles made of (a) multilayer pigmented [HDPE (high-density polyethylene) +20g kg(-1) TiO2/HDPE + 40g kg(-1) carbon black/HDPE + 20g kg(-1) TiO2], (b) monolayer pigmented [HDPE + 20g kg(-1) TiO2], (c) clear PET (polyethylene terephthalate) and (d) pigmented [PET + 20 g kg(-1) TiO2] were monitored for a period of 7 days. Milk packaged in coated paperboard cartons and stored under the same experimental conditions served as the "control" sample. Data were obtained for lipid oxidation, vitamin A and riboflavin content, microbial growth and sensory attributes (odour and taste). Results showed good protection of milk packaged in all packaging materials with regard to microbiological and chemical parameters assessed over the 7-day test period. Vitamin A losses recorded were 11% for multilayer and monolayer pigmented HDPE and pigmented PET bottles vs. 16% for the paperboard cartons and 31% for the clear PET bottles after 7 days of storage. Respective losses for riboflavin were 28% for the multilayer pigmented HDPE bottle and the paperboard carton, 30% for the monolayer pigmented HDPE bottle, 33% for the pigmented PET bottle and 40% for the clear PET bottle. Based on sensory analysis the shelf life of low fat (15 g kg-1) pasteurized milk is approximately 5 days. The best overall protection for the product was provided by the multilayer followed by the monolayer TiO2-pigmented HDPE bottle. Such packaging materials are recently emerging in the fresh milk packaging market. (C) 2003 Elsevier Ltd. All rights reserved. International Dairy Journal

The effect of filleting on microbiological, chemical, and sensory properties of aquacultured freshwater trout (Onchorynchus mykiss) stored in ice was studied. Pseudomonads, H2S-producing bacteria (including Shewanella putrefaciens) and Brochothrix thermosphacta were the dominant bacteria while, Enterobacteriaceae in lower counts were also found in the spoilage microflora of whole ungutted and filleted trout over an 18-day storage period in ice. Bacterial counts of whole ungutted trout were always lower than those obtained for filleted trout samples. Mesophilic counts for filleted and ungutted fish exceeded 7 log cfu/cm2 after 10 and 18 days of ice storage, respectively. Of the chemical indicators of spoilage, trimethylamine (TMA) values of ungutted trout increased very slowly whereas for filleted samples higher values were obtained reaching a final value of 4.29 and 6.38 mg N/100 g, respectively (day 18). Total volatile basic nitrogen (TVB-N) values showed no significant increase for whole ungutted trout during storage reaching a value of 20.16 mg N/100 g (day 18) whereas for filleted fish a respective value of 26.06 mg N/100 g was recorded. Thiobarbituric acid (TBA) values of ungutted trout increased very slowly whereas for filleted samples higher values were obtained reaching a final value of 16.21 and 19.41 μg MA/g, respectively (day 18). Of the chemical indices used, none proved useful means of monitoring early freshness for ungutted and filleted trout freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 6 days for the ungutted trout, a grade A for a further 3 days and a grade B for an additional 6 days, after which trout was graded as C (unfit). Acceptability scores for odor, taste and texture of cooked ungutted and filleted trout decreased with time of storage. Results of this study indicated that the shelf-life of whole ungutted and filleted trout stored in ice as determined by sensorial and microbiological data is 15–16 and 10–12 days, respectively.

Post-processing contamination and growth of Listeria monocytogenes in whey cheeses stored under refrigeration is an important safety concern. This study evaluated commercially available nisin (Nisaplin ® ) as a biopreservative to control L. monocytogenes introduced post-processing on Anthotyros, a traditional Greek whey cheese, stored at 4°C in vacuum packages for up to 45 days. The whey used (pH 6.5–6.7) was from Feta cheese manufacture, and it was subjected either to natural acidification (pH 5.3, readjusted to 6.2 with 10% NaOH) prior to heating, or to direct acidification (pH 6.0–6.2) at 80°C with 10% citric acid. Nisin was added either to the whey (100 or 500 IU g −1 ) prior to heating, or to the cheese (500 IU g −1 ) prior to packaging, also inoculated with ca. 10 4 cfu g −1 of L. monocytogenes strain Scott A. In cheese samples without nisin, L. monocytogenes (PALCAM agar) exceeded 7 log cfu g −1 after the first 10 days of storage, irrespective of the whey acidification method. All nisin treatments had an immediate lethal effect (0.7–2.2 log reduction) on L. monocytogenes populations at inoculation (day 0), which was more pronounced with 500 IU g −1 added to the whey. This treatment also suppressed L. monocytogenes growth below the inoculation level for 30 and 45 days in naturally and directly acidified samples, respectively. All other treatments had weak antilisterial effects. Nisin reversed the natural spoilage flora of Anthotyros cheese from Gram-positive to Gram-negative, and this ecological alteration was far more pronounced in the most effective antilisterial treatments.

The advantages of micellar cloud point extraction combined with a surfactant-assisted separation in a HPLC system are presented as a method for the effective separation and determination of nine biogenic amines in fish substrates. Benzoyl derivatives of the amines are extracted inside the micelles of a non-ionic surfactant, Triton X-114, and separated with gradient elution micellar liquid chromatography. Quantification was performed by measuring the UV absorbance of the benzene ring at 254 nm. Detection limits of the nine biogenic amines were in the vicinity of 0.01 mg l(-1) which are approximately 10 times lower than those of the conventional method (HPLC-UV) and 100 times lower than those of micellar electrokinetic capillary chromatography. The correlation coefficients of determinations were 0.9911-0.9996. The method was applied for the determination of putrescine, cadaverine, agmatine, tyramine, tryptamine, phenylethylamine, spermine, spermidine and histamine in trout samples. Recovery of the proposed method ranged from 95 to 103.5%.

The effect of gutting on microbiological, chemical, and sensory properties of aqua-cultured sea bass ( Dicentrarchus labrax ) stored in ice was studied. Pseudomonads and H 2 S-producing bacteria (including Shewanella putrefaciens ) were the dominant bacteria at the end of the 16-day storage period in ice for both whole ungutted and gutted sea bass. Brochothrix thermosphacta and Enterobacteriaceae were also found in the spoilage microflora of ungutted and gutted sea bass but their counts were always less than those of Pseudomonads and H 2 S-producing bacteria. Bacterial counts of whole ungutted sea bass were always higher than those obtained for gutted sea bass samples. Mesophilic counts for gutted and ungutted fish exceeded 7 log cfu g −1 after 9 and 15 days of ice storage, respectively. Of the chemical indicators of spoilage, TMA values of ungutted sea bass increased very slowly whereas for gutted samples higher values were obtained reaching a final value of 0.73 and 4.39 mg N 100 g −1 , respectively (day 16). TVB-N values showed no significant increase for whole ungutted sea bass during storage reaching a value of 27.7 mg N 100 g −1 (day 16) whereas for gutted fish 36.9 mg N 100 g −1 was recorded. TBA values remained low for ungutted sea bass samples until day 16 of storage, whereas for gutted fish were variable. Of the chemical indices used, none proved useful means of monitoring early ungutted and gutted sea bass freshness in ice. Sensory assessment using the EC freshness scale gave a grade E for up to 5 days for the ungutted sea bass, a grade A for a further 2 days and a grade B for an additional 4 days, after which sea bass was graded as C (unfit). Gutted sea bass was given a grade E for up to 3 days, a grade A for the 4–7th days, and a grade B for the 8–10th days of storage, whereas on day 11 it was graded as unfit. Acceptability scores for odor, taste and texture of cooked ungutted and gutted sea bass decreased with time of storage. Results of this study indicate that the shelf-life of whole ungutted and gutted sea bass stored in ice as determined by the overall acceptability sensory scores and microbiological data is 13 and 8 days, respectively.

The effect of gamma irradiation on the natural microflora of whole salted vacuum-packaged trout at 4 and 10°C was studied. In addition, the effectiveness of gamma irradiation in controlling Listeria monocytogenes inoculated into trout was investigated. Irradiation at doses of 0.5 and 2 kGy affected populations of bacteria, namely, Pseudomonas spp., Brochothrix thermosfacta, lactic acid bacteria, H 2 S-producing bacteria typical of Shewanella putrefaciens, and Enterobacteriaceae, at both 4 and 10°C. This effect was more pronounced at the higher dose (2 kGy) and the lower temperature (4°C). Pseudomonads, H 2 S-producing bacteria typical of S. putrefaciens, and Enterobacteriaceae showed higher sensitivity to gamma irradiation than did the rest of the microbial species. Sensory evaluation did not show a good correlation with bacterial populations. On the basis of sensory odor scores, a shelf life of 28 days (2 kGy, 4°C) was obtained for salted vacuum-packaged freshwater trout, compared with a shelf life of 7 days for the unirradiated sample. Under the same conditions, the growth of L. monocytogenes inoculated into the samples was suppressed by 2 log cycles after irradiation (2 kGy) and storage for up to 18 days at 4°C. L'effet d'une irradiation gamma sur la microflore naturelle et sur Listeria monocytogenes dans des truites entieres salees conditionnees sous vide a 4 et 10°C est etudie. Le traitement affecte la microflore naturelle, principalement a des doses elevees (2 kGy) et a temperature faible (4°C). L'evaluation sensorielle ne montre pas une bonne correlation avec les populations bacteriennes. En se basant sur les resultats d'evaluation des odeurs, la duree de conservation du produit passe de 7 a 28 jours a 4°C pour les truites irradiees a 2kGy.