首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到10条相似文献,搜索用时 156 毫秒
1.
The optimal conditions of decontamination of field salad by treatment with warm water containing hydrogen peroxide were determined with the aid of a central composite design. It was the aim to improve the hygienic status while keeping the sensory quality at the highest level possible. Two series of experiments were performed to study the effects of the following parameters: temperature (45–50 °C), H2O2 (1–4%) and treatment time (60–210 s). In series 1 the effect on sensory properties and reduction of total aerobic counts was investigated. To determine sensory quality, treated samples stored at 4 °C for 7 days were subjected to evaluation by 15 panelists. Overall visual quality (OVQ), color, texture and odor correlated well with product acceptability (R2=0.934, 0.946, 0.945 and 0.956, respectively), and OVQ was the most sensitive criterion. An acceptability of 75% in OVQ was chosen as the limit and an acceptance area was defined to deduce permitted conditions for decontamination. Within that area a reduction of total counts by 2.64–3.22 and 1.9–3.48 log10 cfu/g was achieved after treatment and storage at 4 °C for 7 days, respectively. In series 2 field salad was inoculated with Listeria innocua and Salmonella Typhimurium and it was observed that within the area of acceptability a reduction of the numbers of the challenge organisms by 1.27–3.26 and 0.79–3.05 log10 cfu/g, respectively, was achieved immediately after treatment, and by 1.64–3.09 (L. innocua) and 1.1–2.63 log10 cfu/g (S. Typhimurium) after storage. The initial decontaminating effect on L. innocua and S. Typhimurium was sustained or even increased after storage, when the salad was treated below 48.9 °C for more than 68 s. Three independent experiments confirmed the reliability of the models of the count reduction of L. innocua and S. Typhimurium.  相似文献   

2.
The aim was to study spoilage during the refrigerated storage of cooked pork loin processed by the sous vide method. Samples were packaged under vacuum into polyamide-polypropylene pouches, cooked at an oven temperature/time of 70 °C/12 h, chilled at 3 °C and stored at 2 °C for 0, 5 or 10 weeks. Microbial (psychrotrophs, lactic acid bacteria, Enterobacteriaceae, moulds and yeasts), physical–chemical (pH, water activity, TBARS, acidity, L*a*b* colour, texture profile analysis and shear force) and sensory (appearance, odour, flavour, texture and acceptance) parameters were determined. The results showed that sensory spoilage preceded microbiological spoilage of sous vide pork loin. Counts bellow 1 log cfu/g of psychrotrophs, anaerobic psychrotrophs, Enterobacteriaceae and lactic acid bacteria were detected in any control week, while moderate counts (2–3 log cfu/g) of moulds and yeasts were found. Minor changes in water activity, lipid oxidation, CIELab colour, hardness, cohesiveness or gumminess were associated with spoilage of pork loin, only decreases of lactic acid, springiness and shear force were observed. The pork loin was unacceptable after 10 weeks. This loss of acceptance was mainly due to the deterioration of meaty flavour and odour, although the loss of appearance, juiciness and firmness also contributed. Moderate warmed-over and rancidity were detected. The sensory analysis was the most effective method for determining the shelf life of the sous vide pork-based dishes.  相似文献   

3.
We studied the effect of hot-water treatment at various time/temperature regimes to design a decontamination process which is consistent with the recommendation of the National Advisory Committee on Microbiological Criteria for Foods (NACMCF) to reduce pathogens on seeds by 5log cfu/g. Alfalfa, mung bean and radish seeds were inoculated by immersion with more than 107 cfu/g of enterobacteria (Salmonella Senftenberg W775, S. Bovismorbificans and Escherichia coli O157:H), dried and stored at 2 °C. The numbers of salmonellae and E. coli O157:H on these seeds remained unchanged during storage for 8 weeks. To achieve sprouting rates of more than 95%, time-temperature regimes were defined. The thermal treatment of contaminated mung bean (2–20 min for 55–80 °C), radish and alfalfa seeds 0.5–8 min (53–64 °C) reduced all pathogens by more than 5log cfu/g. For S. Senftenberg W775 on radish seeds, D values of 3.2, 1.9 and 0.6 min were determined for exposure at 53, 55 and 58 °C and a z value of 6.2 °C was calculated. For alfalfa seeds, the respective D values were 3.0, 1.6, and 0.4 min and the z value was the same as that determined for radish seeds.  相似文献   

4.
Carcasses, carcass portions and pieces of manufacturing beef were sampled by swabbing a 100 cm2 randomly selected site on each of 25 randomly selected product units at each of several stages of the meat production processes at a large beef packing plant. After skinning, aerobes were recovered from each sample, at log mean numbers of 1.86 log cfu cm−2; and coliforms and Escherichia coli were recovered from <15 of 25 samples at log total numbers of 3.27 and 3.16 log cfu 2500 cm−2. The numbers of bacteria recovered after preevisceration washing and spraying with 2% lactic acid solution were similar to the numbers recovered after skinning, and the numbers recovered from carcasses that had been eviscerated, split, vacuum/hot-water cleaned and trimmed were little different. However, the numbers of coliforms and E. coli were reduced by the washing of carcass sides; and pasteurizing followed by spraying with lactic acid reduced the numbers of aerobes to log mean numbers of 0.71 log cfu cm−2 and coliforms and E. coli to log total numbers of 1.28 and 0.30 log cfu 2500 cm−2, respectively. After cooling for 24 h, numbers of aerobes on carcass sides had increased to log mean numbers of 2.57 log cfu cm−2, and log total numbers of coliforms and E. coli had increased to 3.34 and 2.18 log cfu 2500 cm−2, respectively. Numbers had not increased after sides had been held for a further 12 h before breaking. Numbers of bacteria on forequarters increased during breaking operations on hanging sides and increased further after forequarters were dropped to conveyor belts. Numbers on hindquarters were little affected by those operations. Large numbers of bacteria were recovered from cleaned equipment that contacted forequarters. The numbers of bacteria on trimmings did not increase during conveying from breaking lines to bulk containers. The numbers of bacteria on manufacturing beef were less than the numbers on forequarters trimmings, but more than the numbers on hindquarters trimmings. The log mean numbers of bacteria in ground beef produced at the plant were 3.11 log cfu g−1, and the log total numbers of coliforms and E. coli were 1.84 and 1.30 log cfu 25 g−1, respectively. Similar numbers of bacteria were recovered from ground samples of manufacturing beef. It therefore appears that most of the E. coli as well as other bacteria in ground beef are deposited on the product during the initial operations for breaking forequarters. Thus, improvement of equipment cleaning rather than of production processes would be required to improve the microbiological condition of ground beef prepared at the plant. However, skinning, washing of dressed sides, pasteurizing and cooling are evidently critical control points in carcass production processes.  相似文献   

5.
The effects of freezing rate (in a cold room at –18°C and in an air-blast freezer at –50°C) and frozen storage (at –18°C for 0–12 months) on texture and the sensory quality of pineapple fruit slices of Smooth Cayenne and Red Spanish cultivars were examined. The texture of pineapple fruit slices was evaluated by sensory and instrumental measurements. Sensory texture was highly (P0.05) and positively correlated with overall fruit acceptability and appearance and negatively correlated with flavour in the two cultivars studied. Sensory analysis showed no significant differences (P0.05) in the appearance, colour, odour, texture, flavour and overall acceptability between the two varieties studied when frozen at different rates, as compared to the fresh product and after 1 year of frozen storage at –18°C. The two cultivars are suitable for freezing.  相似文献   

6.
Zusammenfassung Die Eignung eines chromogenenLimulus-Tests zur Bestimmung des Endotoxin-Gehalts in Eiprodukten wurde gepruft. Dabei zeigte die Analyse verschieden stark bakteriell belasteter Volleimassen eine deutliche Korrelation zwischen Endotoxin-Konzentration und Gesamtkeimzahl (6 x 104 cfu x ng–1 Endotoxin) Bowie der Anzahl vonEnterobacteriaceen (7x102 cfu x ng–1 Endotoxin). Vergleichbare Ergebnisse konnten auch mit Eigelb- und Eiweilßproben erzielt werden. Der Endotoxin-Nachweis wurde durch Hitzebehandlung (65 °C, 60 min) nicht beeinflußt. Endotoxinfreies steriles Volleimaterial hatte bis zu einer Konzentration im Testansatz von 10 mg x ml–1 keinen Einfluß auf das Mcßergebnis. Im vorliegenden Bericht wird eine miniaturisierte Version des Testverfahrens vorgestellt, die im Mikro titerplatten-System durchgeführt werden kann.
Determination of endotoxin in egg products with a miniaturized chromogenic Limulus test
Summary A chromogenicLimulus amoebocyte lysate assay was applied to monitor endotoxin concentration in egg products. Analysis of differently contaminated whole egg probes revealed a strong correlation of endotoxin concentration to total bacterial count 6 x 104 cfu x ng–1, where cfu=colony-forming unit) as well as to number ofEnterobacteriaceae (1 ng/7 x 102 cfu). Similar relations were also found for egg white and egg yolk probes. A significant influence of heat pretreatment of egg probes (65° C, 60 min) on endotoxin detection could be excluded. Up to a concentration of 10 mg x µl–1 endotoxin-free whole egg material did not interfere with the test system. A miniaturized version of the chromogenicLimulus test, which can be carried out in microtiter plates, is described.
  相似文献   

7.
The combined effect of thymol (0–300 ppm), carvacrol (0–300 ppm), and temperature (0–18 °C) on the quality of non conventional poultry patties packaged in air and modified atmosphere (MAP: 40% CO2; 30%O2; 30% N2) was investigated using a simplex centroid mixture design. The patties were monitored for microbiological (total viable count, Enterobacteriaceae, lactic acid bacteria, Pseudomonas spp.) physico-chemical (pH, colour) and sensory attributes. For the patties mixed with the antimicrobials and stored at low temperature (0–3 °C) a reduction of the cell load of about 1–1.5 log cfu/g was observed. The log reduction was lower at the end of storage time and decreased with the increase of the temperature. For the poultry patties packaged in MAP the higher log reduction for Pseudomonas spp. during all the storage time was observed. In both packaging atmospheres the combination of the essential oils and low temperature determined no modification for off-odour during the first 4 days of storage.  相似文献   

8.
Chlorine dioxide (ClO2), ozone, and thyme essential oil has been found to be effective in reducing pathogens, including Escherichia coli O157:H7, on selected produce. The efficacy of these sanitizers was evaluated, alone or through their sequential washing to achieve a 3 or more log reduction of mixed strains of E. coli O157:H7 on shredded lettuce and baby carrots. Samples sprinkle inoculated with mixed strains of E. coli O157:H7 were air-dried for 1 h at 22±2°C in a biosafety cabinet, stored at 4°C for 24 h, and then treated with different concentrations of disinfectants and exposure time. Sterile deionized water washing resulted in approximately 1log reduction ofE. coli O157:H7 after 10 min washing of lettuce and baby carrots. Gaseous treatments resulted in higher log reductions in comparison to aqueous washing. However, decolorization of lettuce leaves was observed during long exposure time. A logarithmic reduction of 1.48-1.97log10 cfu/g was obtained using aqueous ClO2 (10.0 mg/L for 10 min) ozonated water (9.7 mg/L for 10 min) or thyme oil suspension (1.0 mL/L for 5 min) on lettuce and baby carrots. Of the three sequential washing treatments used in this study, thyme oil followed by aqueous ClO2/ozonated water, or ozonated water/aqueous ClO2 were significantly (P<0.05) more effective in reducing E. coli O157:H7 (3.75 and 3.99log, and 3.83 and 4.34 log reduction) on lettuce and baby carrots, respectively. The results obtained from this study indicate that sequential washing treatments could achieve 3-4log reduction of E. coli O157:H7 on shredded lettuce and baby carrots.  相似文献   

9.
Caprine colostrums (6 batches) were subjected to heat (56°C for 60 min and 63°C for 30 min) and high-pressure (400 and 500 MPa for 10 min at 20°C) treatments at laboratory scale, and analyses of the main microbial groups and the extent of IgG denaturation (determined by immunodiffusion) were performed. Overall mean microbial values in raw colostrums were: total count, 5.55 log cfu/mL; Enterobacteriaceae, 2.64 log cfu/mL; lactococci, 5.41 log cfu/mL; lactobacilli, 2.34 log cfu/mL; and enterococci, 4.06 log cfu/mL. Neither Salmonella spp. nor Listeria monocytogenes were detected, whereas coagulase-positive staphylococci were found in various colostrum samples with an overall mean of 1.02 log cfu/mL. Heat and high-pressure treatments significantly reduced total count (1.47 log), lactococci (1.45 log), enterococci (2.47 log), and Enterobacteriaceae, whereas lactobacilli and coagulase-positive staphylococci counts were reduced to undetectable levels, but differences between technological treatments were not statistically significant. High-pressure treatments were as efficient in reducing the bacterial population as were heat pasteurization treatments: 95.50 and 96.93% for pressure treatments of 400 and 500 MPa, and 91.61 and 97.59% for heat treatments of 56°C for 60 min and 63°C for 30 min, respectively. All treatments assayed produced a reduction in colostrum IgG concentration (27.53, 23.58, 23.33, 22.09, and 17.06 mg/mL for raw, heat-treated at 56°C for 60 min or 63°C for 30 min, and pressure-treated at 400 and 500 MPa, respectively), but differences were only observed between raw colostrums and those pressure-treated at 500 MPa. This laboratory-scale study indicated that 20- to 30-mL volumes of goat colostrum could be heated and pressure-treated (400 MPa) to produce hygienic colostrum without affecting IgG concentration.  相似文献   

10.
Fresh-cut iceberg lettuce inoculated with Escherichia coli O157:H7 was submitted to chlorine washing (150 mg/mL) and modified atmosphere packaging on laboratory scale. Populations of E. coli O157:H7 were assessed in fresh-cut lettuce stored at 4, 8, 13 and 16 °C using 6–8 replicates in each analysis point in order to capture experimental variability. The pathogen was able to grow at temperatures ≥8 °C, although at low temperatures, growth data presented a high variability between replicates. Indeed, at 8 °C after 15 days, some replicates did not show growth while other replicates did present an increase. A growth primary model was fitted to the raw growth data to estimate lag time and maximum growth rate. The prediction and confidence bands for the fitted growth models were estimated based on Monte-Carlo method. The estimated maximum growth rates (log cfu/day) corresponded to 0.14 (95% CI: 0.06–0.31), 0.55 (95% CI: 0.17–1.20) and 1.43 (95% CI: 0.82–2.15) for 8, 13 and 16 °C, respectively. A square-root secondary model was satisfactorily derived from the estimated growth rates (R2 > 0.80; Bf = 0.97; Af = 1.46). Predictive models and data obtained in this study are intended to improve quantitative risk assessment studies for E. coli O157:H7 in leafy green products.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号