Marangoni force-driven manipulation of photothermally-induced microbubbles.

The generation and manipulation of microbubbles by means of temperature gradients induced by low power laser radiation is presented. A laser beam (λ = 1064 nm) is divided into two equal parts and coupled to two multimode optical fibers. The opposite ends of each fiber are aligned and separated a distance D within an ethanol solution. Previously, silver nanoparticles were photo deposited on the optical fibers ends. Light absorption at the nanoparticles produces a thermal gradient capable of generating a microbubble at the optical fibers end in non-absorbent liquids. The theoretical and experimental studies carried out showed that by switching the thermal gradients, it is possible to generate forces in opposite directions, causing the migration of microbubbles from one fiber optic tip to another. Marangoni force induced by surface tension gradients in the bubble wall is the driving force behind the manipulation of microbubbles. We estimated a maximum Marangoni force of 400nN for a microbubble with a radius of 110 µm.

A comparison between E-beam irradiation and high pressure treatment for cold-smoked salmon sanitation: microbiological aspects.

The effectiveness of electron beam irradiation and high pressure treatment for the sanitation of cold-smoked salmon from two points of view, microbial safety and shelf-life extension, was compared. From the response of L. monocytogenes INIA H66a to irradiation, a D value of 0.51 kGy was calculated. For samples stored at 5 degrees C, 1.5 kGy would be sufficient to attain a Food Safety Objective (FSO) of 2 log(10)cfu/g L. monocytogenes for a 35-day shelf-life, whereas 3 kGy would be needed in the case of a temperature abuse (5 degrees C + 8 degrees C). Pressurization at 450 MPa for 5 min was considered to be an insufficient treatment, since the FSO of 2 log(10)cfu/g L. monocytogenes was only attained for a shelf-life of 21 days at 5 degrees C. However, treatment at 450 MPa for 10 min achieved this FSO for samples held during 35 days at 5 degrees C, or during 21 days under temperature abuse (5 degrees C+8 degrees C) conditions. Irradiation at 2 kGy kept the microbial population of smoked salmon below 6 log(10)cfu/g after 35 days at 5 degrees C, with negligible or very light changes in its odor. Pressurization at 450 MPa for 5 min also kept the microbial population below 6 log(10)cfu/g after 35 days at 5 degrees C and did not alter odor, but affected negatively the visual aspect of smoked salmon.

Destruction of Salmonella Senftenberg on the shells of intact eggs by thermoultrasonication.

The combined effect of ultrasonic waves and heat treatment applied simultaneously was evaluated on the survival of strains of Salmonella Senftenberg on shells of intact eggs. This combined process has a higher killing effect than heat treatment alone. The decimal reduction times (D-values) were decreased by 65.2 to 11.1% in the temperature range studied (57.8 to 67 degrees C). In contrast to the effect on Salmonella enterica serovar Enteritidis in a previous study, thermoultrasonication had no important advantage for elimination of Salmonella Senftenberg. However, because 52 degrees C is a nonlethal temperature for Salmonella Senftenberg, the conditions used for the elimination of Salmonella Enteritidis (52 degrees C for 12 min) in the previous study would be equivalent to ultrasonic treatment alone in the present study. This thermoultrasonication treatment may result in a 100-fold greater reduction of Salmonella Senftenberg than that achieved by common in-shell egg pasteurization (60 degrees C for 3.5 min).

Effect of thermoultrasonication on Salmonella enterica serovar Enteritidis in distilled water and intact shell eggs.

The combined effects of simultaneous application of ultrasonic waves and heat treatment (thermoultrasonication) on the survival of a strain of Salmonella enterica Enteritidis was studied in both distilled water and intentionally contaminated intact eggs immersed in water. Although minor differences were observed between parameters obtained for thermoultrasonic treatment of bacteria suspended in water and those attached to the shell egg, the thermoultrasonication effects were considered to be of the same level in the range of temperatures assayed (52 to 58 degrees C). This combined process presented a clearly higher killing effect than the heat treatment alone. It decreased the decimal reduction times (D-values) by 80 to 55%, respectively, in the range of temperatures for heat treatment when the organism was suspended in water, which means a 99.5% reduction (5D to >2D) of the original bacterial load versus a 90% reduction for the heat treatment alone. The practical implications of the phenomenon are discussed.

Development of an n-3 fatty acid and α-tocopherol enriched dry fermented sausage.

Five batches of "salchichon", which is a dry fermented Spanish sausage, were manufactured using backfat and meat enriched in polyunsaturated n-3 fatty acids and α-tocopherol. Raw materials were obtained from animals fed on diets of the same ingredients with the exception of the oil source [sunflower oil (batch control, C), linseed oil (L and LE), 1/1 (w/w) linseed and olive oil (LO and LOE)] and α-tocopherol quantity [20 mg/kg diet of α-tocopherol (C, L and LO) or 200 mg/kg diet of α-tocopherol (LOE and LE)]. A final product with a healthier polyunsaturated fatty acid n-6:n-3 ratio (< 4) was obtained from all linseed oil-enriched batches as compared with the control (12). The batches of sausages manufactured with backfat and meat from animals fed on diets enriched in α-tocopherol and linseed, or linseed and olive oil with or without α-tocopherol supplementation show a higher lipid oxidative stability than those of diets enriched in linseed oil without α-tocopherol supplementation. Sausages of dietary treatment C, LE, LO and LOE did not show differences in water, protein, fat and ash contents, a(w), pH, texture profile analysis and sensory features (odour, colour, texture, juiciness and taste quality). Sausages manufactured with material from animals fed on linseed oil-enriched diets and no added α-tocopherol (L) showed an unfavourable rancidity degree detected by both 2-thiobarbituric acid-reactive substances (TBARs) index and sensory panel.

Protective Effect of Broccoli, Onion, Carrot, and Licorice Extracts against Cytotoxicity of N-Nitrosamines Evaluated by 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium Bromide Assay.

The protective effect of nine fruit and vegetable aqueous (H(2)O) and ethanolic (EtOH) extracts against the cytotoxicity of N-nitrosodimethylamine (NDMA), N-nitrosopyrrolidine (NPYR), N-nitrosodibutylamine (NDBA), and N-nitrosopiperidine (NPIP) was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The fruit extracts under investigation did not show a protective effect against any N-nitrosamines tested. Four vegetable extracts exhibited a protective effect (to 100% of survival) and a stimulation of cellular proliferation (>100% of survival) in decreasing order against NDMA and NPYR: broccoli(EtOH) > onion(H2O) > carrot(EtOH) > onion(EtOH) > licorice(H2O). Decreasing orders against NDBA and NPIP were, respectively, broccoli(EtOH) > licorice(H2O) > carrot(EtOH) > onion(EtOH) and broccoli(EtOH) > carrot(EtOH) > licorice(H2O) > onion(EtOH). Thus, broccoli(EtOH) extract (19-20 mg/mL) showed greater protective effect and stimulation of cellular proliferation (160% of survival) against all N-nitrosamines studied than the other vegetable extracts tested.