Accurate flow cytometric monitoring of Escherichia coli subpopulations on solid food treated with high pressure carbon dioxide.

AIMS: Evaluation of flow cytometry coupled with viability markers to monitor the inactivation of Escherichia coli cells spiked on solid food following High Pressure Carbon Dioxide (HPCD), a mild processing technology. METHODS AND RESULTS: Flow cytometry (FCM) coupled with SYBR-Green I and Propidium Iodide was applied to monitor the effect of HPCD treatment on E. coli cells spiked on fresh cut carrots, therefore mimicking contamination of food products by faecal coliforms. FCM allowed to distinguish E. coli cells from carrot debris and natural flora, to evaluate the reduction of total cells, and to quantify viable and dead cells based on their membrane integrity after HPCD treatment. The comparison of FCM results with conventional cultivation methods revealed that HPCD treatments performed at 120 bar, 22 or 35°C for 5 min disrupted 43 and 53% of bacterial cells, respectively, and produced a large percentage of partially permeabilized (96·5 and 98%) cells. CONCLUSIONS: Although treatments at 22°C for 10 min and at 35°C for 7 min were sufficient to inhibit the ability of all E. coli cells to replicate with an inactivation of 8 Log, FCM analysis showed that the inactivation of intact cells was only 2-2·5 Log. A fraction of HPCD-treated cells maintained their metabolic activity and re-growth capacity, indicating that the treatment induces a transitory Viable But Not Cultivable (VNBC) state. SIGNIFICANCE AND IMPACT OF THE STUDY: Under stress conditions many pathogens enter in a VBNC state, thus escaping detection by traditional cultivation methods. We provide the first evaluation of HPCD-mediated bacterial inactivation on fresh food using FCM coupled with viability markers, which should assist in the prevention of food-associated health risks.

Effects of dense phase carbon dioxide pasteurization on the physical and quality attributes of a red grapefruit juice.

Red grapefruit juice was treated with continuous dense phase carbon dioxide (DPCD) equipment to inactivate yeasts and molds and total aerobic microorganisms. A central composite design was used with pressure (13.8, 24.1, and 34.5 MPa) and residence time (5, 7, and 9 min) as variables at constant temperature (40 degrees C), and CO(2) level (5.7%) after experimentally measuring CO(2) solubility in the juice. Five log reduction for yeasts and molds and total aerobic microorganisms occurred at 34.5 MPa and 7 min of treatment. A storage study was performed on the fresh juice DPCD treated at these conditions. degrees Brix, pH, titratable acidity (TA), pectinesterase (PE) inactivation, cloud, color, hue tint and color density, total phenolics, antioxidant capacity, and ascorbic acid were measured after the treatment and during 6 wk storage at 4 degrees C. During storage, the DPCD-treated juice showed no growth of total aerobic microorganisms and yeasts and molds. Cloud increased (91%) while percent PE inactivation was partial (69.17%). No significant (alpha= 0.05) differences were detected between treated and untreated samples for degrees Brix, pH, and TA. Treated juice had higher lightness and redness and lower yellowness. No significant differences (alpha= 0.05) were detected for the hue tint values while the color density value was higher for the treated samples compared to the untreated. The treatment and the storage did not affect the total phenolic content of the juice. Slight differences were detected for the ascorbic acid content and the antioxidant capacity. The experimental results showed evidence that the treatment can maintain the physical and quality attributes of the juice, extending its shelf life and safety.

Measurement of high-pressure carbon dioxide solubility in orange juice, apple juice, and model liquid foods.

An experimental system to measure the carbon dioxide (CO(2)) solubility in liquids at different pressures was designed and tested. Pressure and temperature were controlled in the system, and the design assured an accurate measurement of solubility. Experimental measurements of CO(2) solubility were performed in pure water, model solutions (ascorbic acid-sugars-water, citric acid-sugars-water), and in commercial orange juice (OJ) and apple juice (AJ), as a function of pressure (7.58 to 15.86 MPa) at constant temperature (40 degrees C). Aspen simulation software was used to predict the solubility in simple cases. All experimental results and predictions from simulations were compared with literature data. Measurements of CO(2) solubility in pure water were not significantly different than the literature. CO(2) solubility (g/100 g of liquid) results in the model liquids and in the juices were lower than for pure water, due to the presence of solutes. The software simulation was able to predict the CO(2) solubility in the model systems at low pressures.

Microbial inactivation kinetics during high-pressure carbon dioxide treatment: nonlinear model for the combined effect of temperature and pressure in apple juice.

Isobaric and isothermal semi-logarithmic survival curves of natural microflora in apple juice treated with high-pressure carbon dioxide at 7, 13, and 16 MPa pressures and 35, 50, and 60 degrees C temperatures were fitted with a nonlinear equation to find the values of the coefficient b(P), b(T), n(P), and n(T). Profiles of the model parameters were obtained as a function of pressure and temperature. The model fitted with good agreement(R(2) > 0.945), the survival curves. An empirical equation was proposed to describe the combined effects of pressure and temperature. The equation, derived from a power law model, was written in the form: log(10) S(t) = -log(e) [C(0)+C(1) x exp (K(T) x (T-T(C))-C(2) x exp (K(P) x (P-P(C))) x t (C(3)xT(2)+C(4)xT+C(5)). The proposed model fitted the experimental data well. At 7 MPa and 50 and 60 degrees C, 13 MPa and 35 and 60 degrees C, 16 MPa and 35 degrees C, the model provided (log)10 reduction residual values (observed value-fitted value) lower than 0.284 showing a good agreement between the experimental and the predicted survival levels.

Lengthening of the mandible by distraction osteogenesis: experimental work in rabbits.

The purpose of this experimental work was to lengthen the mandible in rabbits by means of distraction osteogenesis. The excellent results on the lengthening of the extremities with the Ilizarov technique and the unpredictable results in the mobilization of the facial bones by means of osteotomies and grafts are reasons for the application of the gradual distraction method in mandibular lengthening. Bone lengthening was first performed in 1905; but Ilizarov rekindled interest in 1951 when he induced bone neoformation in the extremities by the distraction technique using multiplanar wires and external circular fixators. We lengthened the mandible in 12 New Zealand adult rabbits using different mountings of the Ilizarov apparatus by means of two fixation techniques: transfixion and nontransfixion. In the transfixion group (6 rabbits), the two wires were passed through both mandibular rami. In this group, a 2-cm lengthening was obtained. In the nontransfixion group (6 rabbits), only one mandibular ramus was included with the transfixion wires. In this group, 1-cm lengthening was achieved. Unilateral lengthening was obtained with the nontransfixion technique and the lengthening of both rami with the transfixion technique. The results were evaluated by clinical periodic postoperative radiographs and histological studies of newly formed bone and surrounding soft tissues (masticatory muscles, arteries, and so on). The results demonstrated that lengthening of the mandible is obtained by means of a mature and normal new bone that is produced in the osteotomized area.

[Effects of cigarette smoking on the caliber of the small airways in healthy young smokers]. / Effetti del fumo di sigaretta sul calibro delle piccole vie aeree in giovani sani fumatori.

Although many studies have demonstrated the deleterious effect of cigarette smoking on lung function, nevertheless, a relative minority of smokers develop significative functional impairment. In this study we examined the ventilatory function in a group (n = 18) of young healthy smokers and in a control group of non smokers (n = 8). The two groups didn't show significative differences in spirometric tests. However in smokers the indexes of small airways calibre (FEF50 and FEF25) were slightly lower than for non smokers.