Functional and quality characteristics of the red blood cell fraction from biopreserved porcine blood as influenced by high pressure processing

The effects of high hydrostatic pressure (HHP) processing, at 400 MPa for 15 min at 20 °C, on the microbiological and functional characteristics of the red blood cell (RBC) fraction obtained from porcine blood, previously preserved by means of lactic acid bacteria (LAB) was studied. Biopreservation was achieved by incubation of inulin-enriched blood inoculated with a LAB strain (Enterococcus raffinosus PS99) for 72 h at 5 °C. Results showed that incubation of blood with added E. raffinosus followed by HHP treatment reduced the levels of contaminant coliforms, proteolytic, hemolytic bacteria, and Pseudomonas spp. on RCB. Color parameters, protein solubility, foaming and emulsifying properties, as well as texture and water holding capacity of heat-induced gels from RBC were not seriously damaged by the combined treatments. This is a new approach to process and preserve animal blood fractions for the development of functional and/or nutritional food ingredients with added value.     

The effects of high hydrostatic pressure at subzero temperature on the quality of ready-to-eat cured beef carpaccio

We compared the application of high hydrostatic pressure (HHP) on unfrozen carpaccio (HHP at 20°C) and on previously-frozen carpaccio (HHP at -30°C). HHP at 20°C changed the color. The pressure increase from 400 to 650MPa and the time increment from 1 to 5min at 400MPa increased L* and b*. a* decreased only with 650MPa for 5min at 20°C. The prior freezing of the carpaccio and the HHP at -30°C minimized the effect of the HHP on the color and did not change the shear force, but increased expressible moisture as compared to the untreated carpaccio. HHP at 20°C was more effective in reducing the counts of microorganisms (aerobic total count at 30°C, Enterobacteriaceae, psychrotrophs viable at 6.5°C and lactic acid bacteria) than HHP at -30o C. With HHP at 20°C, we observed a significant effect of pressure and time on the reduction of the counts.     

Preservation of porcine blood quality by means of lactic acid bacteria

The capacity of 12 lactic acid bacteria (LAB) strains to preserve porcine blood during storage was evaluated. A general ability of LAB to prevent blood's hemolysis and to maintain the functional properties of plasma was observed. Two strains, PS99 (Enterococcus raffinosus) and TA43 (Lactobacillus reuteri), were selected for studies at 5°C according to their antibacterial activity in blood stored at 15°C. After 144h at 5°C, lower counts of coliforms, Pseudomonas spp., proteolytic and hemolytic bacteria were obtained in blood containing either PS99 or TA43 as compared to the non-inoculated blood. When inulin (2%) was added to blood, higher inhibition values were obtained and Enterococcus raffinosus (PS99) showed the best abilities for blood preservation. On the basis of these results it seems worthwhile to supplement blood with inulin and to inoculate it with an active LAB strain to avoid undesirable changes during chill storage, especially useful to prevent the effects of a cold-chain breakdown.     

Destruction of Escherichia coli and salmonellae on mutton carcases by treatment with hot water

Laboratory experiments showed that the surface tissues of beef and mutton samples were not permanently discoloured to an objectionable extent by treatment with water at 80° C or 10 sec. This treatment destroyed more than 99% of the numbers of E. coli and salmonellae inoculated on the beef samples and more than 99·9% of the same organisms inoculated on the exterior surfaces of tissue taken from sheep carcases. Immersion in water at 80°C for 10 sec of whole sheep carcases taken off the end of the slaughter line in a commercial abattoir destroyed c. 99% of the contaminating coliform organisms and c. 96% of the total number of aerobic bacteria initially present on the surface tissues. The application of such a treatment to sheep carcases in abattoirs should substantially reduce any salmonella contamination on the meat and may improve storage life. Although initially discoloured to a depth of 0·5 mm by the treatment, sheep carcases heated at 80°C for 10 sec almost completely regained their normal appearance within a few hours during subsequent chilled storage at 1-4°C.     

Microbiological stabilization of Aloe vera (Aloe barbadensis Miller) gel by high hydrostatic pressure treatment

The effect of high hydrostatic pressure (HHP) treatment (300, 400 and 500MPa for 1 and 3min at 20°C) on the microbiological shelf-life and microbiota composition of Aloe vera gel during 90days of storage at 4°C was investigated. Aerobic mesophilic and psychrotrophic bacteria, as well as moulds and yeasts, were enumerated after HHP treatment and through cold storage. Randomly selected isolates from the count plates were identified by standard methods and the API identification system. Results showed that HHP treatment at or over 400MPa for 3min were effective to keep the microbial counts to undetectable levels during the whole storage period, and consequently the microbiological shelf-life of A. vera gel was extended for more than 90days at 4°C. The microbiota in the untreated A. vera gel was dominated by Gram-negative bacteria (mostly Rahnella aquatilis) and yeasts (mostly Rhodotorula mucilaginosa). In contrast, Gram-positive bacteria tentatively identified as Arthrobacter spp. and Micrococcus/Kocuria spp. were the predominant microorganisms in samples pressurized at 300MPa for 1 and 3min, while Bacillus megaterium predominating in samples treated at 400MPa for 1min. At 400MPa for 3min and above, the microbial growth was completely suppressed during at least 90days; however, viable spore-formers were detected by enrichment.     

High pressure and freezing temperature effect on quality and microbial inactivation of cured pork carpaccio

The effects of high hydrostatic pressure (HHP: 0, 400, and 600 MPa) and freezing temperature (-15° vs. -35°C) were evaluated on the quality and microbial inactivation of cured pork carpaccio. Samples treated with HHP resulted in lighter and yellower color, higher Chroma, shear force, scores for pink color, cooked and gel appearance, incidence of iridescence, lower scores for brightness and raw meat appearance and lower levels of lactic acid bacteria and psychrotrophs during shelf life compared with untreated samples (P<0.05). Treating carpaccio at -35°C resulted in a darker color and a more tender carpaccio with a higher rating for crumbliness and lower rating for fibrousness and chewiness compared with -15°C (P<0.05). While HHP is effective in microbial inactivation and shelf life extension of pork carpaccio, product quality may be decreased due to lower tenderness and poorer appearance. However, HHP in combination with low freezing temperature can be used successfully to deliver high quality pork carpaccio with extended shelf life to the ready-to-eat market.     

Effects on the development of blown pack spoilage of the initial numbers of Clostridium estertheticum spores and Leuconostoc mesenteroides on vacuum packed beef

Beef steaks were inoculated with Clostridium estertheticum spores and Leuconostoc mesenteroides cells at all combinations of numbers of 0, 10, 100 or 1000/cm(2) for each organism. After vacuum packaging the steaks were stored at 4, 1, or -1.5°C. Pack volumes were determined by water displacement at suitable intervals. Irrespective of L. mesenteroides numbers, for packs containing meat inoculated with 0, 10, 100 or 1000 spores/cm(2), 60, 16, 3 and 1 of 60 packs did not swell. The times of onset of swelling were twice as long at -1.5 as at 4°C, but they were not affected by the inoculated numbers of L. mesenteroides. Rates of pack swelling increased with increasing storage temperature and number of spores, but decreased with increasing numbers of inoculated L. mesenteroides. Lactic acid bacteria can apparently prevent development of blown pack spoilage of vacuum packs containing meat contaminated with low numbers of C. estertheticum.     

Effect of refrigerated and frozen storage on the survival of Campylobacter jejuni in cooked chicken meat breast

This experimental work aimed to examine the survivability of Campylobacter jejuni in cooked chicken breast under several conditions: storage for 1, 3, and 7 d at refrigerated temperatures (4 °C) and for 20 d at frozen temperatures (-18 °C). In addition, storage at ambient temperature (26 to 28 °C) was involved. Chicken samples were inoculated with a mixed culture of C. jejuni strains (ATCC: 29428 and 33219) of known concentrations (50 and 500 CFU/g). Bacterial cells were recovered and enumerated using standard procedure (Preston method). Bacteria were not detected in the majority of samples stored at ambient temperature. Refrigeration reduced survivals in 95, 90, and 77.5% for samples inoculated with 500 CFU/g and kept for 1, 3, and 7 d, respectively. The maximum reduction reached 1 log(10) cycle for all refrigeration durations. It was observed that bacteria died in 17.5% of samples kept for 7 d at 4 °C. However, survivors in samples inoculated with 50 CFU/g were not detected in 50, 65, and 55% of samples kept for 1, 3, and 7 d, respectively. Freezing rendered survivors not detectable in 70% of samples inoculated with 50 CFU/g, while survived viable counts were reduced in 92.5% of samples inoculated with 500 CFU/g. These findings suggested that C. jejuni could be killed or just sublethally injured with or without reduction in viable counts under the investigated storage temperatures, which may indicate the ability of this bacterium to survive in chicken meat stored under refrigerated and frozen conditions.     

Antimicrobial properties of salt (NaCl) used for the preservation of natural casings

The antimicrobial properties of salt (NaCl) used for the preservation of natural casings were studied by investigating the survival of six bacterial species in natural casings at different water activity (aw) levels. Individual sheep casings were inoculated with ca. 10(5) colony-forming units (cfu) g(-1) of Escherichia coli, Salmonella typhimurium, Listeria monocytogenes, Staphylococcus aureus, Clostridium perfringens and 10(2)cfu g(-1) of E. coli O157:H7. The casings were stored at 20+/-1.5 degrees C in different brines and dry salt, giving aw-levels of 0.90 aw, 0.87aw, 0.85 aw, 0.83 aw and 0.75 aw. Samples were taken at day 1, 3, 6, 8, 13, 20, 27 and 30 after inoculation and the number of bacteria present was determined. Based on survival curves, death rates (day(-1)) were calculated to quantify the reduction in log10 cfu g(-1) per day. The influence of aw on death rates was higher for Gram-negative bacteria than for Gram-positive bacteria. The death rates were overall higher for Gram-negatives than for Gram-positives. No clear reduction in the survival of C. perfringens in relation to any aw level was observed in this study. These results indicate that the antimicrobial properties of salt used for the preservation of natural casings are sufficient to reduce the bacterial contamination (except for Clostridium spores) well below acceptable levels at a water activity level of 0.85 or lower during a 30-day storage period.     

Influence of prior growth conditions, pressure treatment parameters, and recovery conditions on the inactivation and recovery of Listeria monocytogenes, Escherichia coli, and Salmonella Typhimurium in turkey meat

The relatively high prevalence of Listeria monocytogenes, Escherichia coli O157:H7, and Salmonella enterica serovar Typhimurium in various food products is of great concern to the food industry. The objective of this study was to determine the pressure-inactivation of the pathogens in a representative food model as affected by prior growth temperature, physiological age of the culture, pressure level and treatment temperature. The effect of post-treatment conditions (incubation temperature and gas atmosphere) on the bacterial recovery was also determined. The pathogens being studied were inoculated into sterile turkey breast meat to a final level of ca. 3 logCFU/g and then grown to two stages, the early stage (representative of exponential phase) and late stage (representative of stationary phase), at 15, 25, 35, and 40 °C. Turkey meat samples were pressure-treated at 400 and 600 MPa for 2 min at initial sample temperatures of 4, 20 and 40 °C. Following treatment, bacterial counts in the samples were determined aerobically or anaerobically at incubation temperatures of 15, 25, 35, and 40 °C. Pressure inactivation of the bacterial pathogens increased as a function of the pressure levels and treatment temperatures. Generally speaking, early stage cells were more resistant than late stage cells (P<0.05). The incubation gas atmosphere did not affect bacterial recovery. Bacteria grown at 15-35 °C underwent higher population reductions than those grown at 40 °C. With regard to recovery temperatures, low temperatures promoted greater recovery of injured early and late stage cells than higher temperatures (P<0.05). This study indicates the importance of environmental conditions to which bacteria are exposed prior to pressure treatment and recovery conditions of the bacteria after pressure treatment when considering the adequacy of pressure treatments to enhance the microbiological safety of foods.     

Survival of Escherichia coli O157:H7 and Campylobacter jejuni in bottled purified drinking water under different storage conditions

Survival of Escherichia coli O157:H7 and Campylobacter jejuni that were separately inoculated into bottled purified drinking water was investigated during storage at 22, 4, and -18 °C for 5, 7, and 2 days, respectively. Two inoculation levels were used, 1 and 10 CFU/ml (10(2) and 10(3) CFU/100 ml). In samples inoculated with 10(2) CFU/100 ml, C. jejuni was not detectable (>2-log reduction) after storage under the conditions specified above. E. coli O157:H7 was detected on nonselective and selective media at log reductions of 1.08 to 1.25 after storage at 22 °C, 1.19 to 1.56 after storage at 4 °C, and 1.54 to 1.98 after storage at -18 °C. When the higher inoculation level of 10(3) CFU/100 ml was used, C. jejuni was able to survive at 22 and 4 °C, with 2.25- and 2.17-log reductions, respectively, observed on nonselective media. At these higher inoculation levels, E. coli O157:H7 was detectable at 22, 4, and -18 °C, with log reductions of 0.76, 0.97, and 1.21, respectively, achieved on nonselective media. Additionally, E. coli O157:H7 showed significant differences in culturability (P<0.05) on the nonselective and selective culture media under the different storage conditions, with storage at -18 °C for 2 days being the treatment most inhibiting. The percentage of sublethal injury of E. coli O157:H7 ranged from ～33 to 75%, indicating that microbial examination of bottled water must be done carefully, otherwise false-negative results or underestimation of bacterial numbers could pose a health risk when low levels of pathogens are present.     

High pressure inactivation of Salmonella on Jalapeño and Serrano peppers destined for direct consumption or as ingredients in Mexican salsa and guacamole

In summer of 2008, the United States witnessed one of the largest multi-state salmonellosis outbreak linked to the consumption of Jalape?o and Serrano peppers tainted with Salmonella enterica serovar Saintpaul. The first objective of this study was to assess the application of high hydrostatic pressure (HHP) to decontaminate Jalape?o and Serrano peppers from this pathogen. Jalape?o and Serrano peppers were inoculated with a five-strain cocktail of Salmonella to a final level of ca. ~6 log CFU/g and subsequently pressure-treated in the un-wetted, wetted (briefly dipped in water) or soaked (immersed in water for 30 min) state at 300-500 MPa for 2 min at 20°C. The extent of pressure inactivation increased as a function of the pressure level and in the order of soaked>wetted>un-wetted state achieving population reductions ranging from 1.1 to 6.6 log CFU/g. Overall, pressure treatment at 400-450 MPa (soaked) or 450-500 MPa (wetted) for 2 min at 20°C rendered Salmonella undetectable. Since salsa and guacamole are two examples of widely consumed Mexican dishes that incorporate raw Jalape?o and Serrano peppers, we subsequently investigated the pressure-inactivation of Salmonella in salsa and guacamole, originating from contaminated peppers used as ingredients. The storage time (0, 12 or 24 h) of the condiments prior to HHP as well as the pH (3.8-5.3) and the type of acidulants (vinegar and lemon juice) used all influenced the extent of Salmonella inactivation by HHP. This study demonstrates the dual efficacy of HHP to decontaminate fresh chile peppers destined for direct consumption and minimally process condiments possibly contaminated with raw peppers to enhance their microbiological safety.     

USE of HYDROSTATIC PRESSIJRE to PRODUCE HIGH QUALITY and SAFE FRESH PORK SAUSAGE

The effects of high hydrostatic pressure (HHP) on the survival of microor ganisms and quality changes of fresh pork sausages were investigated. Pork sausage inoculated with Listeria monocytogenes at 1O⁷ CFU/gram was prepared and subjected to HHP at 414 and 552 MPa, at treatment temperatures of 25 and SOC. for various time intervals to examine pressure effects on inactivation of bacteria. At a pressure of 414 MPa and SOC for 2 min, the microorganisms in fresh pork sausages were completely inactivated. Partial discoloration of meat was observed after 10 min of pressurization above 414 MPa at either temperature.
The effect of HHP treatment on the physical and rheological properties of sausage was also studied. the sausages increased infirinness with an increase in the pressure applied. the pressure-treated sausages were generally lighter in color as compared with the heat-treated sausages.
The optimal pressure/temperature/time conditions that resulted in minimum quality changes with microbiologically safe fresh pork sausages was 414 MPa and SOC for 2 min.     

Production of salami from ostrich meat with strains of Lactobacillus sake, Lactobacillus curvatus and Micrococcus sp

The aim of this study was to produce Italian-type salami from ostrich meat using different combinations of Lactobacillus sake, Lactobacillus curvatus and Micrococcus sp., and to compare the sensory characteristics of these products to that of salami produced with glucono-delta-lactone (GdL). Meat inoculated with starter cultures was fermented for four days (20-22 °C, 97-99% RH) and ripened for a further 11 days (16-18 °C, 40-60% RH). Cell counts of lactic acid bacteria and micrococci, and changes in pH were determined daily during fermentation. According to texture and sensory evaluation, the best salami was produced by a starter culture containing L. curvatus DF 38 and Micrococcus sp. MC 50.     

Inactivation of Escherichia coli and Listeria innocua in kiwifruit and pineapple juices by high hydrostatic pressure

Escherichia coli and Listeria innocua in kiwifruit and pineapple juices were exposed to high hydrostatic pressure (HHP) at 300 MPa for 5 min. Both bacteria showed equal resistance to HHP. Using low (0 degrees C) or sub-zero (-10 degrees C) temperatures instead of room temperature (20 degrees C) during pressurization did not change the effectiveness of HHP treatment on both bacteria in studied juices. Pulse pressure treatment (multiple pulses for a total holding time of 5 min at 300 MPa) instead of continuous (single pulse) treatment had no significant (p>0.05) effect on the microbial inactivation in kiwifruit juice; however, in pineapple juice pulse treatment, especially after 5 pulses, increased the inactivation significantly (p<0.05) for both bacteria. Following storage of pressure-treated (350 MPa, 20 degrees C for 60 s x 5 pulses) juices at 4, 20 and 37 degrees C up to 3 weeks, the level of microbial inactivation further increased and no injury recovery of the bacteria were detected. This work has shown that HHP treatment can be used to inactivate E. coli and L. innocua in kiwifruit and pineapple juices at lower pressure values at room temperature than the conditions used in commercial applications (>400 MPa). However, storage period and temperature should carefully be optimized to increase the safety of HHP treated fruit juices.     

Temperature effect on nitrogen removal performance and bacterial community in culture of marine anammox bacteria derived from sea-based waste disposal site

Anaerobic ammonium oxidation (anammox) bacteria have been detected in variety of marine environment in recent years, however, there have been only a few studies on their characteristics in the culture. The aim of this study is to reveal the effect of temperature on nitrogen removal ability and bacterial community in a culture of marine anammox bacteria (MAAOB). The MAAOB were cultured from the sediment of a sea-based waste disposal site at the North Port of Osaka Bay in Japan. The maximum nitrogen removal rate (NRR) was observed at 25°C in the MAAOB culture, and it decreased both at below 20°C and over 33°C. The activation energy of the MAAOB culture was calculated to be 54.6 kJ mol(-1) in the 5°C to 30°C range. No significant change in bacterial community according with temperature (5-37°C) was confirmed in the results of polymerase chain reaction and denaturing gradient gel electrophoresis (PCR-DGGE). Meanwhile, a number of bacteria related to the oxidation-reduction reaction of sulfur were confirmed and it is speculated that they involved in the activity of MAAOB and nitrogen removal ability in the culture.     

超高压处理对冷藏鲈鱼片细菌群落结构的影响

为研究超高压处理对冷藏鲈鱼片贮藏期间细菌菌群结构的影响,以压力250 MPa,时间9 min的超高压条件处理鲈鱼片,并以0.1 MPa处理样品为对照组。将处理后的样品置于4℃冰箱中贮藏,分别在0,3,6,9,11,13,15 d进行总挥发性盐基氮(TVB-N)与微生物指标(细菌总数、希瓦氏菌数、假单胞菌数和嗜冷菌数)测定,并作相关性分析,评价超高压处理对冷藏鲈鱼片品质的影响。随后分别提取两组样品在贮藏前期、中期、中后期与末期4个阶段的宏基因组,通过高通量测序技术分析冷藏鲈鱼肉不同阶段的细菌菌群。结果表明,样品经超高压处理,其TVB-N值、细菌总数、假单胞菌数、希瓦氏菌数和嗜冷菌数等指标的上升速度明显缓于对照组。相关性分析表明,TVB-N值与微生物指标可作为鲜度评价指标,用于分析鲈鱼片超高压处理后贮藏期间的品质变化。高通量测序结果表明,对照组与处理组样品在贮藏前期的主要细菌有芽孢杆菌属、大洋芽孢杆菌属与乳球菌属;在贮藏中后期与末期两个阶段,超高压处理组与对照组的菌相组成呈显著差异,优势腐败菌种类不同,对照组在中后期的主要细菌为假单胞菌属,超高压处理组在中后期的主要细菌为嗜冷菌属,对照组末期主要腐败菌为嗜冷菌属、假单胞菌属、希瓦氏菌属和气单胞菌属,超高压处理组末期主要腐败菌为嗜冷菌数、假单胞菌属与耶尔森氏菌属。可见,超高压处理在抑制TVB-N值与微生物指标升高的同时,也对其贮藏期间的菌相组成产生明显的影响,使嗜冷菌与希瓦氏菌的生长受到抑制。     

Survival of Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes on inoculated walnut kernels during storage

The survival of single strains or cocktails of Salmonella, Escherichia coli O157:H7, and Listeria monocytogenes was evaluated on walnut kernels. Kernels were separately inoculated with an aqueous preparation of the pathogens at 3 to 10 log CFU/g, dried for 7 days, and then stored at 23°C for 3 weeks to more than 1 year. A rapid decrease of 1 to greater than 4 log CFU/g was observed as the inoculum dried. In some cases, the time of storage at 23°C did not influence bacterial levels, and in other cases the calculated rates of decline for Salmonella (0.05 to 0.35 log CFU/g per month) and E. coli O157:H7 (0.21 to 0.86 log CFU/g per month) overlapped and were both lower than the range of calculated declines for L. monocytogenes (1.1 to 1.3 log CFU/g per month). In a separate study, kernels were inoculated with Salmonella Enteritidis PT 30 at 4.2 log CFU/g, dried (final level, 1.9 log CFU/g), and stored at -20, 4, and 23°C for 1 year. Salmonella Enteritidis PT 30 declined at a rate of 0.10 log CFU/g per month at 23°C; storage time did not significantly affect levels on kernels stored at -20 or 4°C. These results indicate the long-term viability of Salmonella, E. coli O157:H7, and L. monocytogenes on walnut kernels and support inclusion of these organisms in hazard assessments.     

Influence of oxygen exclusion and temperature on pathogenic bacteria levels and sensory characteristics of packed ostrich steaks throughout refrigerated storage

Ostrich steaks (290) were obtained from Iliofibularis muscles. For microbiological and pH determinations, samples were inoculated with Listeria monocytogenes NCTC 11994 (80 steaks) or Escherichia coli ATCC 12806 (80), then air- or vacuum-packed and stored at either 4±1°C or 10±1°C. Analyses were carried out on days 0, 3, 6 and 9 of storage. For sensory evaluation, samples (130) were air- or vacuum-packed and stored at 4±1°C or at 10±1°C. Sensory attributes (odour, colour, drip loss, texture and general acceptability) were scored by six untrained judges using an unstructured nine-point hedonic scale on eleven sampling days (0, 3, 6, 9, 12, 15, 18, 21, 24, 27 and 30). Increases in microbial counts (log(10)cfu/g) were observed throughout storage in all groups of samples for both L. monocytogenes (from 6.39±0.43-6.62±0.32 at day 0 to 8.87±0.19-9.64±0.43 at day 9) and E. coli (from 5.57±0.15-5.68-0.40 to 7.79±0.96-9.64±0.17). Gas atmosphere influenced microbial counts from day 3 of storage with lower (P<0.05) values observed in vacuum- than in air-packed samples at 10°C (L. monocytogenes) or at 4 and 10°C (E. coli). Storage temperature significantly influenced bacterial counts throughout storage, especially in air-packed samples. Lower pH values in vacuum- than in air-packed samples were observed from day 6. Both effects (gas atmosphere and temperature) influenced the hedonic scores, with higher values assigned to vacuum-packed samples for most attributes (with the exception of drip loss) and sampling days. A marked influence of storage temperature on sensorial scores was obtained in air-packaged ostrich steaks. The shelf-life (time until the average general acceptability score fell below 5) was 6 (air-packed samples), 9 (vacuum-packed, 10°C), or 12 days (vacuum-packed, 4°C). The results being reported here suggest the importance of both oxygen exclusion and storage at low temperatures to reduce microbiological risks and improve the acceptability of ostrich meat. However, the short shelf-life of this product highlights the need to keep the time between slaughter and sale to a minimum.