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1.
The effects of essential oils on the shelf life of sardine (Sardina pilchardus) fillets in cold storage were assessed at 4–6°C. The oils were sprayed on the fillets as well as with the addition of absorbent food pads that also contained essential oils. Sardine fillets were divided into eight test groups. Group A: fillets stored without treatment (control group); Group B: fillets packaged with food pads (without the addition of essential oils); Group C: Rosemary oil sprayed onto food pads (10 ml of 1.5% RO); Group D: Black seed oil sprayed onto the food pads (10 ml of 1.5%BSO); Group E: Rosemary oil sprayed onto both sides of the sardine fillets (10 ml of 1.5%RO); Group F: Black seed oil sprayed onto both sides of sardine fillets (10 ml of 1.5% BO); Group G: Rosemary oil sprayed onto both sides of the sardine fillets (10 ml of 1.5% RO) and on the food pads (+10 ml of 1.5% RO); and Group H: Black seed oil sprayed onto the sardine fillets and the food pads (10 ml of 1.5% BSO onto both sides of fillets +10 ml of 1.5% BSO onto food pads). Tests were carried out at days 0, 3, 5 and 7. When compared to the control group, food pads containing rosemary and black seed oils extended the shelf life of sardine fillets by approximately 2 days at 4–6°C. Group A and B exceeded the limit of consumption on day 3, and Group C and D exceeded this microbiological limit after day 5. RO and BSO both exhibited the same antimicrobial effects on the shelf life of sardine fillets. Groups E, F, G and H prolonged the microbiological threshold by 7 days compared to the control. However, Group G and H had 1–1.5 log lower TVC load than Group E and F. Food pads containing antimicrobial essential oils may be used to extend the shelf life of fresh fish, however, further investigations are needed to determine safety standards.  相似文献   

2.
The biosynthesis of volatile compounds in plants is affected by environmental conditions. Lactones are considered to be peach‐like aroma volatiles; however, no enzymes or genes associated with their biosynthesis have been characterized. White‐fleshed (cv. Hujingmilu) and yellow‐fleshed (cv. Jinxiu) melting peach (Prunus persica L. Batsch) fruit were used as materials in two successive seasons and responses measured to four different temperature treatments. Five major lactones accumulated during postharvest peach fruit ripening at 20 °C. Peach fruit at 5 °C, which induces chilling injury (CI), had the lowest lactone content during subsequent shelf life after removal, while 0 °C and a low‐temperature conditioning (LTC) treatment alleviated development of CI and maintained significantly higher lactone contents. Expression of PpACX1 and activity of acyl‐CoA oxidase (ACX) with C16‐CoA tended to increase during postharvest ripening both at 20 °C and during shelf life after removal from cold storage when no CI was developed. There was a positive correlation between ACX and lactones in peach fruit postharvest. Changes in lactone production in response to temperatures are suggested to be a consequence of altered expression of PpACX1 and long‐chain ACX activity.  相似文献   

3.
Temperature variation affects the growth, maturation and distribution of fish species due to increasing constraints on physiological functions therefore, the aim of the present study is to evaluate effect of temperature on thermal tolerance and standard metabolic rate (SMR) of gilthead seabream (Sparus aurata). For this purpose, tolerable temperature ranges of juvenile gilthead seabream acclimated at 15, 20, 25, and 30 °C for 30 days were estimated using dynamic and static thermal methodologies. The SMRs of the fish were also determined based on oxygen consumption rate (OCR). The dynamic and static thermal tolerance zones of gilthead seabream were calculated as 737 °C2 and 500 °C2, respectively, with a resistance zone area of 155.5 °C2. The SMR of the fish at the above acclimation temperatures (AT) was determined as 138, 257, 510, and 797 mg O2 h−1 kg−1, respectively and were significantly different (P < 0.01, n = 10). The temperature quotient (Q10) in relation to the SMR of the fish was calculated as 3.45, 3.91, and 2.44 for acclimation temperature ranges of 15–20, 20–25, and 25–30 °C, respectively. The fact that the SMR increased with rising temperatures and then decreased gradually after 25 °C indicates that the temperature preference of juvenile gilthead seabream lies between 25 and 30 °C. This study shows that gilthead seabream tolerates a relatively narrow temperature range, and consequently, a low capacity for acclimatisation to survive in aquatic systems characterised by temperature variations.  相似文献   

4.
Aims: To determine the efficacy of X‐ray processes in inactivating L. monocytogenes levels in smoked catfish during storage at 5°C and to determine the effects of X‐ray doses on controlling the growth of spoilage bacteria on smoked catfish during storage at 5°C for up to 5 weeks. Methods and Results: Smoked catfish fillets inoculated with L. monocytogenes were treated with 0·0–2·0 kGy X‐ray and stored at 5°C for 5 weeks. The negative controls (uninoculated/untreated) and uninoculated samples treated with the lowest (0·1 kGy) and highest (2·0 kGy) doses were stored at 5°C and tested for psychrotrophs count during the 5 weeks of storage. The initial L. monocytogenes population on smoked catfish was significantly (P < 0·05) reduced to undetectable level by a treatment of 1·0 kGy or higher. The initial psychrotrophs count on smoked catfish was significantly reduced from 4·7 CFU g?1 to below the detectable level by a treatment with 2·0 kGy. Conclusions: Smoked catfish treated with 2·0 kGy X‐ray had no detectable L. monocytogenes throughout 35 days of storage at 5°C. A treatment with 2·0 kGy X‐ray also kept the levels of psychrotrophs in the smoked catfish within the acceptable level until 35 days. Significance and Impact of the Study: The results of this investigation indicate that X‐ray at 2·0 kGy can eliminate L. monocytogenes and extend the shelf life of smoked catfish stored at refrigeration temperature.  相似文献   

5.
Aims: The aim of the study was to evaluate the behaviour of Listeria monocytogenes in the conditioning liquid of packaged water buffalo mozzarella cheese (WBMC). Methods and Results: The conditioning liquid was contaminated with L. monocytogenes, and the contaminated samples were stored at four different storage temperatures: 5 and 10°C for 22 days; 20°C for 9 days; 20°C for 3 days and then at 5°C for 6 days. The results showed that L. monocytogenes concentration decreased when contaminated samples were stored at 5°C. When WBMC was stored at 20°C and at 10°C, L. monocytogenes started to grow after a lag phase of 3 and 10 days, respectively. When samples were stored at variable temperature conditions, L. monocytogenes numbers showed a lag phase of 5 days. Conclusions: Use of a conditioning liquid characterized by acidity and a correct storage temperature is able to counteract pathogen replication during shelf life. A high concentration of lactic acid bacteria was associated with effective control of L. monocytogenes but the role of lactic acid bacteria in WBMC conditioning liquid requires further investigation. Significance and Impact of the Study: According to European regulations, food producers should be able to justify decision‐making on the shelf life assigned to their products, taking into account reasonable storage conditions and use by consumers. The results of the trial yielded information for producers of WBMC and similar cheeses for decision‐making on product shelf life.  相似文献   

6.
In the production of ethanol from lignocellulosic material, pretreatment of the raw material before enzymatic hydrolysis and fermentation is essential to obtain high overall yields of sugar and ethanol. Two‐step steam pretreatment results in higher ethanol yields from softwood than the standard one‐step pretreatment process. However, the difficulty with separation and washing of the material at high pressure between the two pretreatment steps is a major drawback. In this study, a new one‐step pretreatment procedure was investigated, in which the time‐temperature profile was varied during pretreatment. The efficiency of pretreatment was assessed by performing simultaneous saccharification and fermentation on the pretreated slurries. Pretreatment of SO2‐impregnated softwood performed by varying the temperature (190–226°C), the residence time (5–10 min), and the mode of temperature increase (linear or stepwise), resulted in recovery of about 90% of the mannose and glucose present in the raw material. The highest ethanol yield, 75% of theoretical based on the glucan and mannan content of the raw material, was obtained at pretreatment conditions of 190°C for 12 min. Similar ethanol yields were achieved when running the pretreatment as one‐step (190–200°C), two levels of temperature, at shorter residence time (7 min), which results in lower capital costs for the process. © 2010 American Institute of Chemical Engineers Biotechnol. Prog., 2010  相似文献   

7.
A high pressure (200 bar) CO2–H2O process was developed for pretreating lignocellulosic biomass at high‐solid contents, while minimizing chemical inputs. Hardwood was pretreated at 20 and 40 (wt.%) solids. Switchgrass, corn stover, big bluestem, and mixed perennial grasses (a co‐culture of big bluestem and switchgrass) were pretreated at 40 (wt.%) solids. Operating temperatures ranged from 150 to 250°C, and residence times from 20 s to 60 min. At these conditions a biphasic mixture of an H2O‐rich liquid (hydrothermal) phase and a CO2‐rich supercritical phase coexist. Following pretreatment, samples were then enzymatically hydrolyzed. Total yields, defined as the fraction of the theoretical maximum, were determined for glucose, hemicellulose sugars, and two degradation products: furfural and 5‐hydroxymethylfurfural. Response surfaces of yield as a function of temperature and residence time were compared for different moisture contents and biomass species. Pretreatment at 170°C for 60 min gave glucose yields of 77%, 73%, and 68% for 20 and 40 (wt.%) solids mixed hardwood and mixed perennial grasses, respectively. Pretreatment at 160°C for 60 min gave glucan to glucose yields of 81% for switchgrass and 85% for corn stover. Biotechnol. Bioeng. 2010;107: 451–460. © 2010 Wiley Periodicals, Inc.  相似文献   

8.
We studied the demand‐feeding behaviour was studied of gilthead seabream (Sparus aurata, L.) reared under either constant (25 ± 0.5°C, 12 : 12 L : D, control group) or natural (experimental group) temperature and photoperiod conditions during a period from winter to summer. Hourly demand‐feeding activity profiles were recorded using self‐feeding devices; these profiles showed that control group behaved entirely as a diurnal species, exhibiting no nightly activity and decreased demand rates in winter months. The experimental group did exhibit nightly activity (in incomplete darkness); this group also showed reduced demand rates in winter months, accompanied by a demand peak shift towards evening/night hours that followed the day's temperature peak of colder months.  相似文献   

9.
10.
We have attempted to improve the viability of cereal mesophyll protoplasts by pretreatment of leaves with dl-α-difluoromethylarginine (DFMA), a specific `suicide' inhibitor of the enzyme (arginine decarboxylase) responsible for their osmotically induced putrescine accumulation. Leaf pretreatment with DFMA before a 6 hour osmotic shock caused a 45% decrease of putrescine and a 2-fold increase of spermine titer. After 136 hours of osmotic stress, putrescine titer in DFMA-pretreated leaves increased by only 50%, but spermidine and spermine titers increased dramatically by 3.2- and 6-fold, respectively. These increases in higher polyamines could account for the reduced chlorophyll loss and enhanced ability of pretreated leaves to incorporate tritiated thymidine, uridine, and leucine into macromolecules. Pretreatment with DFMA significantly improved the overall viability of the protoplasts isolated from these leaves. The results support the view that the osmotically induced rise in putrescine and blockage of its conversion to higher polyamines may contribute to the lack of sustained cell division in cereal mesophyll protoplasts, although other undefined factors must also play a major role.  相似文献   

11.
Benzo(a)pyrene [B(a)P] treatment of gilthead seabream, 25 mg/kg, i.p. for 5 consecutive days, did not cause any significant changes in ethylmorphine N-demethylase and aniline 4-hydroxylase activities of liver microsomes. The same treatment did not alter the liver microsomal cytochrome b5 content, NADH-cytochrome b5 reductase and NADPH-cytochrome P450 reductase activities. However, benzo(a)pyrene treatment caused a 2–3-fold increase in 7-ethoxyresorufin O-deethylase (7-EROD) activity of gilthead seabream liver microsomes. Although, upon treatment, total cytochrome P450 content of liver microsomes increased about 1.7-fold in 1990 fall, no such increase was observed in spring 1991. However, a new cytochrome P450 with an apparent Mr of 58,000 was observed on SDS-PAGE of liver microsomes obtained from benzo(a)pyrene treated gilthead seabream. Besides, in vitro addition of 0.2 × 10−6 M benzo(a)pyrene to the incubation mixture inhibited 7-ethoxyresorufin O-deethylase activity by 93%. Gilthead seabream liver microsomal 7-ethoxyresorufin O-deethylase activity was characterized with respect to substrate concentration, amount of enzyme, type of buffer used, incubation period and temperature.  相似文献   

12.
The infective juveniles (IJs) of Steinernema carpocapsae‘All’ were osmotically stressed by a mixture of ionic (fortified artificial seawater) and non‐ionic (3.2 mol/L glycerol) solutions to establish a method for osmotic storage of entomopathogenic nematodes. Seven combinations (termed solution A to G) with different proportions of these two solutions were tested, with sterile extra pure water (sepH2O, termed solution H) as a control. The mortality of the IJs at a concentration of 5 × 105 IJ/mL in the solutions A to G, and H were 13.2%, 16.2%, 16.7%, 13.5%, 25.2%, 31.6%, 44.6%, and 1.0%, respectively, after 21 days storage at 25°C. Most of the IJs shrunk and stopped motility after 6–9 hours incubation at 25°C in solutions A to D. Based on the results, solutions A to D and H were chosen to further test the osmotic survival of the IJs at different IJ concentrations (5 × 105, 2.5 × 105, 2 000 IJ/mL) and incubation temperature (30°C, 25°C, 10°C). The resulting IJs were exposed to a high temperature assay (45°C for 4 h, HTA). Osmotically stressed IJs showed improved heat tolerance. The mortality of the IJs increased with the increasing concentrations of the test IJs and the storage temperatures after exposing to the HTA. More than 88.4%, 62.3% or 2.4% of the treated IJs died at the above three IJ concentrations, respectively. At the three IJ concentrations (2 000 IJs/mL, 2.5 × 105 IJs/mL or 5 × 105 IJs/mL), the highest mortality was recorded in solution D (11.6%, 85.9% or 98.0%, respectively), and the lowest mortality in solution B (2. 4%, 62.3% or 86.6%, respectively). No untreated IJs survived after the heat treatment. During 42 days storage at 10°C, the IJs mortality in the solutions A to D and H were 7.19%, 5.97%, 4.41%, 4.34%, and 4.34% respectively, and showed no significant differences. In conclusion, osmotic treatment of the IJs of S. carpocapsae‘All’ in a mixture of ionic and non‐ionic solutions enhances the heat tolerance. The mortality of the IJs after HTA increased with the increasing concentrations of the test IJs and the storage temperatures after exposure to the HTA. The result is promising for the osmotic storage of the entomopathogenic nematodes.  相似文献   

13.
Because conventional approaches for evaluating sugar release from the coupled operations of pretreatment and enzymatic hydrolysis are extremely time and material intensive, high throughput (HT) pretreatment and enzymatic hydrolysis systems have become vital for screening large numbers of lignocellulosic biomass samples to identify feedstocks and/or processing conditions that significantly improve performance and lower costs. Because dilute acid pretreatment offers many important advantages in rendering biomass highly susceptible to subsequent enzymatic hydrolysis, a high throughput pretreatment and co‐hydrolysis (HTPH) approach was extended to employ dilute acid as a tool to screen for enhanced performance. First, a single‐step neutralization and buffering method was developed to allow effective enzymatic hydrolysis of the whole pretreated slurry. Switchgrass and poplar were then pretreated with 0.5% and 1% acid loadings at a 5% solids concentration, the resulting slurry conditioned with the buffering approach, and the entire mixture enzymatically hydrolyzed. The resulting sugar yields demonstrated that single‐step neutralizing and buffering was capable of adjusting the pH as needed for enzymatic saccharification, as well as overcoming enzyme inhibition by compounds released in pretreatment. In addition, the effects of pretreatment conditions and biomass types on susceptibility of pretreated substrates to enzymatic conversion were clearly discernible, demonstrating the method to be a useful extension of HTPH systems. Biotechnol. Bioeng. 2013; 110: 754–762. © 2012 Wiley Periodicals, Inc.  相似文献   

14.
Bioformulation that supports the inoculant under storage condition and on application to field is of prime importance for agroindustry. Pseudomonas strain EKi having biocontrol activity against Macrophomina phaseolina was used in the study. EKi cells were pretreated by carbon starvation, osmotic stress (NaCl), and freeze drying conditions, and talc-based bioformulation was developed. Combined pretreatment with carbon starvation and osmotic stress was given to Pseudomonas cells. Bioformulation of untreated, freeze dried (FD), carbon starved, osmotic stressed, and combined pre-treated cells showed 50.36, 44.76, 45.95, 34.82, and 27.27% reduction in CFU counts after 6 months of storage. The osmotic stressed cells showed one over-expressed protein (11.5 kDa) in common with carbon starved cells responsible for its better shelf life. The plant growth promotory activity of bioformulations was determined taking Cicer arietinum as a test crop in M. phaseolina infested field. Carbon starved + osmotic stressed cells showed maximum enhancement of dry weight (272.56%) followed by osmotic stressed (230.74%), untreated (155.70%), FD (88.93%), and carbon starved (59.34%) cells over uninoculated control. Carbon starved + osmotic stressed, osmotic stressed, untreated, FD, and carbon starved cells showed 156.60, 100, 75, 40, and 16.67% reduction of charcoal rot disease over uninoculated control. The results clearly showed that combined pretreatment by carbon starvation and osmotic stress provides the bacteria potential of rapid adaptation to different environment conditions.  相似文献   

15.
Aims: To investigate the antimicrobial spectrum of Lactococcus piscium CNCM I‐4031 and its protective effect in cooked and peeled shrimp against Brochothrix thermosphacta. Methods and Results: Sixteen pathogenic and spoiling bacteria were inhibited in Elliker, but not in shrimp juice agar plates. In shrimp packed under modified atmosphere and stored at 8°C, B. thermosphacta (103 CFU g?1) was inhibited by 4·1 log CFU g?1 when co‐inoculated with L. piscium (106 CFU g?1). Brochothrix thermosphacta spoiled the product after 11 days, with the emission of strong butter/caramel off‐odours. In co‐culture with L. piscium, sensory shelf‐life was extended by at least 10 days. The inhibition was partially explained by a drop in pH from 6·6 to 5·6. The physicochemical composition of shrimp and shrimp juice was established to identify the inhibition mechanisms involved. Conclusion: Lactococcus piscium CNCM I‐4031 has a wide antimicrobial spectrum. The strain inhibits B. thermosphacta in shrimp and significantly prolongs sensory shelf‐life. Significance and Impact of the Study: Lactococcus piscium CNCM I‐4031 is shown to be a promising agent for improving shrimp quality and may be tested against pathogens and in other food matrices. Knowledge of the physicochemical composition of shrimp and shrimp juice will allow the development of a chemically defined model medium for determining the inhibition mechanisms involved.  相似文献   

16.
Sugarcane bagasses from three experimental sugarcane hybrids and a mill‐reference sample were used to compare the efficiency and mode of action of acid and alkaline sulfite pretreatment processes. Varied chemical loads and reaction temperatures were used to prepare samples with distinguished characteristics regarding xylan and lignin removals, as well as sulfonation levels of residual lignins. The pretreatment with low sulfite loads (5%) under acidic conditions (pH 2) provided maximum glucose yield of 70% during enzymatic hydrolysis with cellulases (10 FPU/g) and β‐glucosidases (20 UI/g bagasse). In this case, glucan enzymatic conversion from pretreated materials was mostly associated with extensive xylan removal (70–100%) and partial delignification occurred during the pretreatment. The use of low sulfite loads under acidic conditions required pretreatment temperatures of 160°C. In contrast, at a lower pretreatment temperature (120°C), alkaline sulfite process achieved similar glucan digestibility, but required a higher sulfite load (7.5%). Residual xylans from acid pretreated materials were almost completely hydrolysed by commercial enzymes, contrasting with relatively lower xylan to xylose conversions observed in alkaline pretreated samples. Efficient xylan removal during acid sulfite pretreatment and during enzymatic digestion can be useful to enhance glucan accessibility and digestibility by cellulases. Alkaline sulfite process also provided substrates with high glucan digestibility, mainly associated with delignification and sulfonation of residual lignins. The results demonstrate that temperature, pH, and sulfite can be combined for reducing lignocellulose recalcitrance and achieve similar glucan conversion rates in the alkaline and acid sulfite pretreated bagasses. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:944–951, 2018  相似文献   

17.
Limited shelf life of entomopathogenic nematodes severely restricts their use in biological control programs. In a series of experiments, the dehydration and rehydration response of Heterorhabditis bacteriophora infective juveniles (IJs) was investigated under a range of glycerol concentrations, temperatures and incubation periods. Based on the outcome of these initial studies, nematodes dehydrated using the optimal process were formulated in alginate granules to understand how these nematodes would undergo survival formulation in a model carrier. The highest rate of osmotically arrested IJs occurred in the 22% glycerol solution (98.06%). IJ recovery was considerably improved when dehydration was processed at 10% glycerol solution and 15°C. By trapping IJs in calcium alginate, depending on the adjuvants, the survival rate of IJs differed significantly. IJ state (dehydrated or non-dehydrated) and the addition of formaldehyde had a profound effect on IJ viability, though the severity of the effect varied was dependent on whether the IJs were alginate formulated. Among different formulations, the highest viability (84.18%) was observed where dehydrated IJs were formulated in alginate granules containing formaldehyde. The results showed that the concentration of osmotic solution not only determines the percentage of dehydrated IJs but also affect their subsequent recovery in an aqueous environment. Overall, the results indicate that the shelf life of formulated IJs is significantly affected by combination effects of a broad range of factors. Then understanding the interactive mode of actions of involved factors in formulation play a critical role in developing and introducing more efficient formulations.  相似文献   

18.
When formaldehyde-treated 131I-albumin was injected into mice, the total liver radioactivity did not change significantly from 5 minutes to 60 minutes after injection. There was a progressive increase with time in the amount of radioactivity associated with liver particles which could be released by osmotic shock; the quantity of material tightly bound to particles, but not releasable by osmotic shock, did not change. At five minutes after injection the liver particles did not release acid-soluble radioactivity into the medium when incubated at 37°. These particles contain the injected protein in osmotically releasable form not associated with proteolytic enzymes and therefore correspond to phagosomes. At 10, 30 or 60 minutes after injection, the particles degraded the protein at similar rates but the activity ceased after 90 minutes incubation when only 50 to 60% of the osmotically releasable material was hydrolyzed. This cessation of activity was shown to be due to a thermal disruption of the particles during incubation.  相似文献   

19.
Sugarcane bagasse was subjected to steam pretreatment impregnated with hydrogen peroxide. Analyses were performed using 23 factorial designs and enzymatic hydrolysis was performed at two different solid concentrations and with washed and unwashed material to evaluate the importance of this step for obtaining high cellulose conversion. Similar cellulose conversion were obtained at different conditions of pretreatment and hydrolysis. When the cellulose was hydrolyzed using the pretreated material in the most severe conditions of the experimental design (210°C, 15 min and 1.0% hydrogen peroxide), and using 2% (w/w) water‐insoluble solids (WIS), and 15 FPU/g WIS, the cellulose conversion was 86.9%. In contrast, at a milder pretreatment condition (190°C, 15 min and 0.2% hydrogen peroxide) and industrially more realistic conditions of hydrolysis (10% WIS and 10 FPU/g WIS), the cellulose conversion reached 82.2%. The step of washing the pretreated material was very important to obtain high concentrations of fermentable sugars. © 2012 American Institute of Chemical Engineers Biotechnol. Prog., 2012  相似文献   

20.
Six new microsatellite loci were isolated and characterized in 32 individuals from a farm population of gilthead seabream (Sparus aurata). Expected heterozygosity at all loci was high, ranging from 0.835 to 0.958 with between 10 and 27 alleles per locus. A multiplex polymerase chain reaction protocol was developed using four of the loci. Cross‐species amplification of the loci was tested in six species of the Sparidae family and four loci were successfully amplified in two or more related species.  相似文献   

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