Biomedical subjects

M E López-Caballero

Publications and source records attributed to M E López-Caballero.

4 recordsLinked to original sources

PubMed2001

Growth and metabolic activity of Shewanella putrefaciens maintained under different CO2 and O2 concentrations.

Growth, trimethylamine (TMA), off-odour and biogenic amine production by a strain of Shewanella putrefaciens isolated from spoiled hake (Merlucius merluccius L.) and cultured in a model system, were tested under four different gas compositions (60% CO2/40% O2, 60% CO2/15% O2/25% N2, 40% CO2/60% O2, 40% CO2/40% O2/20% N2) and under air. After 3 weeks of incubation, the control (air) batch showed the highest microbial counts (> 9 log cfu/ml) and TMA concentrations (45 mg N-TMA/100 ml), and strong putrid off-odours were detected from day 15. High amounts of putrescine and cadaverine were produced in this batch, but histamine increased only slightly. Batches under controlled atmospheres showed reduced growth, TMA, off-odour and biogenic amine production. The 40% CO2/60% O2 mixture had the strongest inhibitory effect on bacterial growth, while the 60% CO2/15% O2/25% N2 mixture was less effective. Putrescine and histamine production was lowest in S. putrefaciens under the 40% CO2/60% O2 mixture. However, the level of histamine in S. putrefaciens was higher under 40% CO2/40% O2/20% N2 than when the bacteria was incubated in air. Under the gas mixtures, there was a similar decrease in the production of cadaverine and agmatine by S. putrefaciens, irrespective of the gas concentrations. The production of 2-phenylethylamine appeared to be inhibited under any atmospheric condition.

Animals↗

PubMed2000

Extension of the shelf life of prawns (Penaeus japonicus) by vacuum packaging and high-pressure treatment.

The present study has investigated the application of high pressures (200 and 400 MPa) in chilled prawn tails, both conventionally stored (air) and vacuum packaged. Vacuum packaging and high-pressure treatment did extend the shelf life of the prawn samples, although it did affect muscle color very slightly, giving it a whiter appearance. The viable shelf life of 1 week for the air-stored samples was extended to 21 days in the vacuum-packed samples, 28 days in the samples treated at 200 MPa, and 35 days in the samples pressurized at 400 MPa. Vacuum packaging checked the onset of blackening, whereas high-pressure treatment aggravated the problem. From a microbiological point of view, batches conventionally stored reached about 6 log CFU/g or even higher at 14 days. Similar figures were reached in total number of bacteria in vacuum-packed samples and in pressurized at 200-MPa samples at 21 days. When samples were pressurized at 400 MPa, total numbers of bacteria were below 5.5 log CFU/g at 35 days of storage. Consequently, a combination of vacuum packaging and high-pressure treatment would appear to be beneficial in prolonging freshness and preventing spotting.

Animals↗

PubMed2000

Oyster preservation by high-pressure treatment.

The purpose of this study was to analyze the effect of 10-min continuous pressure and pulsed pressure in two 5-min steps (400 MPa at 7 degrees C) on the microbial flora, total volatile bases, pH, and texture of purified and unpurified oysters. High-pressure treatment reduced the number of all the target microorganisms (total viable count, H2S-producing microorganisms, lactic acid bacteria, Brochothrix thermosphacta, and coliforms), in some cases by around 5-log units. The difference between the counts in the control and the pressurized oysters remained stable throughout 41 days of storage at 2 degrees C. No Salmonella spp. were detected in either the control batch or the pressurized batches during this storage period. Deterioration of the oyster was accompanied by increased total volatile bases, mainly in the nonpressurized samples. The pH was practically constant in the pressurized oysters and fell slightly in unpressurized samples. As for mechanical properties, shear strength values were higher in pressurized than in unpressurized oysters. Step-pulse pressurizing (400 MPa at 7 degrees C in two 5-min pulses) produced no apparent advantages over continuous pressurizing based on any of the indices used.

Animals↗

PubMed1999

Microbiological changes in pressurized, prepackaged sliced cooked ham.

This was a study of the influence of high-pressure conditions (200 and 400 MPa, 5 and 20 min, 7 degrees C) on microbiological quality and water-binding properties of vacuum-prepackaged sliced cooked ham and how this affects microbiological changes during chilled storage (2 degrees C). Pressurization caused a degree of microbiological inactivation, which increased with pressure level and processing time. Pressurization at 400 MPa significantly reduced the total viable count and lactic acid bacteria to the extent that after 20 min no Enterobacteriaceae, Baird Parker flora, or Brochothrix thermosphacta were detected throughout any of the chilled storage periods studied. In general, gram-positive flora was more resistant to pressure than gram-negative flora. The fact that high pressure (400 MPa) causes considerable inactivation of microorganisms could be used to prolong the shelf life of vacuum-prepackaged sliced cooked ham.

Animals↗