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PubMed2006

Growth of Listeria monocytogenes in egg salad and pasta salad formulated with mayonnaise of various pH and stored at refrigerated and abuse temperatures.

This study investigated and modeled the behavior of Listeria monocytogenes in egg salad and pasta salad as affected by mayonnaise pH (3.8, 4.2, 4.6, and 5.0) and storage temperature (4, 8, and 12 degrees C). At each storage temperature, L. monocytogenes was able to grow in both salads regardless of the mayonnaise pH. The lag-phase durations (LPD) of L. monocytogenes in egg salad ranged from 33 to 85, 15 to 50, and 0 to 19 h, and the growth rates (GR) ranged from 0.0187 to 0.0318, 0.0387 to 0.0512, and 0.0694 to 0.1003 log(10)cfu/h at 4, 8, and 12 degrees C, respectively. The LPD of L. monocytogenes in pasta salad ranged from 210 to 430, 49 to 131, and 21 to 103 h, and GR ranged from 0.0118 to 0.0350, 0.0153 to 0.0418, and 0.0453 to 0.0718 log(10)cfu/h at 4, 8, and 12 degrees C, respectively. The growth of L. monocytogenes was more rapid in egg salad than in pasta salad, indicating that a better growth environment for L. monocytogenes existed in egg salad. In both salads, the LPD decreased and the GR increased as the storage temperature increased. Mathematical models and response surface plots describing the LPD and GR of L. monocytogenes in both salads as affected by the mayonnaise pH and storage temperature were developed. The models confirmed that the growth of L. monocytogenes in egg salad and pasta salad was primarily promoted by higher storage temperatures and, secondarily, by higher mayonnaise pH. The conditions under which the models may be applied to estimate the growth of L. monocytogenes in both salads were identified.

Animals↗
PubMed2006

Role of yeast proliferation in the quality degradation of strawberries during refrigerated storage.

Quality changes of strawberries during storage can be caused both by microbiological and physiological processes. There is little known about the possible contribution of microbiological processes to the quality degradation of strawberries. In this study, quality of strawberries during storage was evaluated by analytical and sensorial analyses. It was the aim to investigate the influence of microbiological activity on the changes of different quality factors of strawberries during storage. During storage at 7 degrees C, quality was mainly determined by the odor and by visual defects. Regarding the odor, highly microbiologically contaminated late-season strawberries packaged in air at 7 degrees C became sensorially unacceptable due to the presence of high amounts of ethyl acetate. This could be attributed to the yeast proliferation: at yeast concentrations above 5.0 log cfu/g, an increase in ethanol was detected in the headspace of the strawberries. It was shown that ethanol was converted to ethyl acetate by strawberries resulting in an unacceptable odor. In an experiment with low microbiologically contaminated early-season strawberries, not reaching the above mentioned yeast counts, less ethyl acetate was detected which resulted in strawberries that were sensorially acceptable during the whole storage period (12 days). Strawberries packaged in modified atmosphere conditions showed a different quality pattern due to the effect of decreased O2-concentrations on both microbiological and physiological processes. This paper demonstrates that also microbiological processes on strawberries should be considered as they could play an important role in the sensorial quality when interacting with physiological processes.

Acetates↗
PubMed2006

Auto-refrigeration/brittle fracture analysis of existing olefins plants--translation of lessons learned to other processes.

This paper describes the use of process hazards analysis (PHA) techniques and "API 579 Recommended Practice for Fitness-for-Service, Assessment of Existing Equipment for Brittle Fracture" to evaluate existing olefins plants. It also examines some of the identified transient process excursions that can result in operations below vessel minimum allowable temperature (MAT), creating the potential for brittle fracture, and the methods of the evaluation are described. The importance of identifying transient process conditions and making materials-of-construction selections based on these conditions is emphasized. Translation of the typical findings and lessons learned to other processes handling light-liquid hydrocarbon materials in carbon steel equipment is discussed, as well as the importance of operator training and response.

Alkenes↗
PubMed2001

Quality control of refrigerated and cryopreserved semen using computer-assisted sperm analysis (CASA), viable staining and standardized fertilization in African catfish (Clarias gariepinus).

A new integrated approach including computer-assisted sperm analysis (CASA), viability staining and fertilization was used to study the quality of cryodiluents used in fish sperm cryopreservation. As an example the sperm quality of an African catfish, Clarias gariepinus (Burchell, 1822), was assessed by its fertilizing ability, motility and viability at day 0 (fresh), after 2 days' storage at 4 degreesC and after 2 days, 5 months and 10 months frozen at -196 degreesC using solutions containing dimethyl sulphoxide (DMSO) or glycerol as permeating cryoprotectants. Four of the best freezing solutions were used, namely, Steyn's extender (S1, S4) and Mounib's extender (M3, M4) associating 10% hen's egg yolk. Progressive sperm movement measured by CASA and expressed by the straight line velocity (VSL), the average path velocity (VAP) and the curvilinear velocity (VCL) was highly correlated with hatching rates obtained from fertilization using minimal sperm:egg ratios. After 2 days, the motility of spermatozoa frozen with DMSO and 10% egg yolk had deteriorated less than that of spermatozoa stored at 4 degreesC. Post-thaw hatching rates reflected the post-thaw sperm viability, which was cryodiluent dependent: 14.9+/-2.0% (S4), 17.0+/-4.2% (S1), 25.9+/-3.7% (M4) and 52.1+/-3.4% (M3) after 5 months of cryopreservation. The percent motility of 10-months-frozen spermatozoa was high in M3 (70.7+/-11.4%) and M4 (64.0+/-2.0%) cryoprotected sperm when measured between 5 and 20 sec after activation, but decreased rapidly to 24.3+/-8.3% (M3) and 23.0+/-9.0% (M4) between 21 and 35 sec after activation. Mounib's extender (M3, M4) provided the best cryoprotection to the spermatozoa for all post-thaw sperm quality measurements and at all freezing durations. Sperm motility was positively related to fertility. Our method will make it possible to develop even better extenders and cryoprotectants.

Animals↗
PubMed2000

Isolation and characterization of Carnobacterium, Lactococcus, and Enterococcus spp. from cooked, modified atmosphere packaged, refrigerated, poultry meat.

The microbiota of commercially produced, cooked and modified atmosphere packaged poultry meat was followed during storage at 3.5 degrees C for up to 7 weeks. The dominant microbiota consisted of Lactococcus raffinolactis (117 isolates), Carnobacterium divergens (61 isolates), Carnobacterium piscicola (11 isolates), Lactococcus garvieae (four isolates), Lactococcus lactis (one isolate) and Enterococcus faecalis (three isolates). All isolates were screened for production of bacteriocins. Only C. piscicola isolates produced an inhibitory substance active against other lactic acid bacteria and against several Listeria spp. Species-specific polymerase chain reaction (PCR) primers were used for the differentiation of Carnobacterium, L. raffinolactis, L. lactis, and L. garvieae strains associated with the modified atmosphere packaged poultry products. No false PCR products were observed with other closely related bacterial species.

Animals↗