On the viability of five probiotic strains when immobilised on various polymers

The viability of probiotic bacteria in six food‐grade polymers, at two concentrations, was evaluated in order to predict their feasibility as materials for bacterium immobilisation. Alginate and whey proteins were the most adequate polymers, except for Lactobacillus acidophilus Ki and Lactobacillus casei 01 at 2% (m/v) alginate. Xanthan gum appeared to be a potential vector for three strains. L‐carrageenan was adequate for both Bifidobacterium strains, but not for Lactobacillus at 2% (m/v). Bifidobacterium strains were not negatively affected by cellulose acetate phthalate, while the opposite held for L. acidophilus strains. Chitosan was the poorest polymer for immobilisation of probiotic bacteria.     

VIABILITY OF BIFIDOBACTERIUM LA CTIS AND LACTOBACILL US ACIDOPHILUS IN MILK: SODIUM CHLORIDE CONCENTRATION AND STORAGE TEMPERATURE

The growth and viability of Bifidobacterium lactis and Lactobacillus acidophilus per se and for both strains as a coculture were studied in reconstituted skim milk so as to assess their dependence upon temperature (5, I0 and 15C), NaCl concentration (0, 0.51 and 1.03 mol L-'), and storage time (0–8 weeks). Cultures of B. lads exhibited no signijkant loss of viability either with increasing NaCl concentration or increasing storage temperature within the ranges studied On the other hand, viability of L. acidophilus decreased with increasing temperature and increasing NaCl concentration under similar conditions. When cocultured with L. acidophilus, B. lactis was signiJicantly less tolerant to higher NaCl levels and higher temperatures than when in pure culture, although rial numbers were still above the threshold required for commercial application. Coculturing with B. lactis had no detrimental effect on viability of L. acidophilus. A mechanistic model, which considers the behavior of the pure and mixed microbial populations is described by specijic death rates which vary with temperature following Arrhenius relationships) and NaCl levels following simple inhibition kinetics) in the milk medium. Activation energies for the death rates of B. lactis and L. acidophilus were 14 kcal mot' and 9–15 kcal mol-I, respectively.     

New chitosan formulation prevents grapevine powdery mildew infection and improves polyphenol content and free radical scavenging activity of grape and wine

Background and Aims: Chitosan, a chitin deacetylated derivative, is a biopolymer able to elicit the plant defence machinery against a variety of pathogens. In crop protection, it is successfully employed for its low toxicity, mainly against virus diseases. In this study, the efficacy of a new chitosan formulation (Kendal Cops^® (Kc)) was evaluated in grapevine against powdery mildew infection. Total polyphenol (TP) content and antiradical power of different grape tissues and of experimental wines produced from treated grapes were also assessed. Methods and Results: Field treatments with different Kc dilutions or with Kc alternated or mixed with fungicides, or with fungicides alone (penconazole and methyldinocap) were carried out in an experimental vineyard of the cv. Montepulciano d'Abruzzo. Kc was effective in controlling powdery mildew, particularly at the concentration of 0.1%, even under high disease pressure conditions. In this case, disease severity was 2.39% in treated grapes, compared with 87.5 and 0.92% in untreated and conventional fungicide‐treated grapevines, respectively. TP content, measured by Folin–Ciocalteau colorimetric assay, was significantly higher in all Kc‐treated grape tissues, compared with both untreated controls and fungicide‐treated grapes. A similar trend was reported with regard to the antioxidant activity, assessed by 2,2‐diphenyl‐1‐pycryl hydrazyl free radical scavenging test. Analysis of wines showed that both TPs and antiradical power were significantly higher in wines made from Kc‐treated grapes compared with fungicide‐treated ones. Conclusions: Kc not only protected grapevine from powdery mildew but also improved TP content and antioxidant activity in both grapes and wine. Significance of the Study: The possibility of using plant defence inducers in crop protection deserves particular attention because of their low environmental impact and of their ability to improve some quality traits of plant foodstuffs. Furthermore, in contrast to fungicides, they hardly select resistant pathogen strains and do not incur fitness costs for the plant.     

Effect of Lipid-Protein Interactions on Hydration Characteristics of Defatted Offal Protein Isolates

Water-protein interactions of rumen and lung protein isolates defatted by different solvents were studied by means of water sorption isotherms. Two isolation procedures were employed to obtain the isolates: (1) alkaline solubilization and isoelectric precipitation of proteins; and (2) SDS solubilization and FeCl₃ precipitation of proteins. Water monolayer values of the protein fraction showed a marked dependence on the dielectric constant of the solvent used for lipid extraction. In lung isolates they increased up to a peak when solvents of intermediate polarity were employed whereas in rumen isolates they were initially constant, decreasing with increase of polarity of solvent. Affinity of water to protein support, showed a more complex pattern and was dramatically affected by the isolation procedure used.     

HIGH PREVALENCE OF EXTENDED-SPECTRUM β-LACTAMASES ESCHERICHIA COLI AND VANCOMYCIN-RESISTANT ENTEROCOCCI ISOLATES FROM CHICKEN PRODUCTS. A PROBLEM OF PUBLIC HEALTH

Twenty-nine chicken products were acquired from different supermarkets in Portugal during September to December 2007 and were analyzed for extended-spectrum β-lactamases (ESBL) Escherichia coli and vancomycin-resistant enterococci (VRE). Cefotaxime-resistant E. coli isolates were recovered in 27 of 29 chicken samples representing 93% of the analyzed samples. The highest percentages of resistance (more than 50% of the isolates) were detected for ampicillin, nalidixic acid and tetracycline. VRE isolates were detected in 17 of 29 samples of chicken origin (59%) and were identified as Enterococcus durans (n  =  15) and E. faecium (n = 2) with the highest percentages of resistance being detected for erythromycin, tetracycline, ampicillin and ciprofloxacin. Seven E. durans and the two E. faecium isolates recovered from chicken wings, gizzard and skin show gelatinase activity.
The high rate of colonization of chicken products by these bacteria supports other studies suggesting that the food chain could be a source of ESBL and VRE colonization in humans representing a public health problem.

PRACTICAL APPLICATIONS

The data indicate that chicken products may be contaminated with a high prevalence of extended-spectrum β-lactamases Escherichia coli and vancomycin-resistant enterococci (VRE). It is important to mention that the isolates present a diversity of phenotypes of antimicrobial resistance, and half of the VRE isolates show also gelatinase activity, indicating that these animals may be a reservoir of bacteria showing virulence and increased resistance to antimicrobial agents, raising special concerns about their transmission to humans through the food chain.     

OPTIMIZING ELECTRON BEAM IRRADIATION OF "TOMMY ATKINS" MANGOES (MANGIFERA INDICA L.)

We determined the optimum irradiation treatment for decontamination of physiologically mature fresh “Tommy Atkins” mangoes, without detriment to the fruits' sensory and chemical properties. Mangoes were irradiated at 1.0, 1.5 and 3.1 kGy using a 10‐MeV linear accelerator (14‐kW LINAC, double beam mode). Mangoes were stored for 21 days at 12C and 62.7% relative humidity with nonirradiated fruits as controls. Dose distribution within the fruit was determined using Monte Carlo techniques. Irradiation did not affect the overall sensory quality of mangoes at doses up to 1.5 kGy. Only fruits irradiated at 3.1 kGy were unacceptable by the panelists. Irradiation at 3.1 kGy enhanced the fruit's aroma characteristics. Irradiation at all levels caused a significant (P ≤ 0.05) decrease (～50–70%) in ascorbic acid content by the end of storage. Mangoes irradiated at 1.5 and 3.1 kGy had slightly higher levels of phenolics than the control (27.4 and 18.3%, respectively). E‐beam irradiation of Tommy Atkins mangoes up to 3.0 kGy causes no detriment to the fruit's overall sensory and chemical quality.     

THERMODYNAMIC PROPERTIES OF BINARY LIQUID MIXTURES OF ETHANE AND ETHYLENE WITH METHANE AND THE RARE GASES

Two series of binary liquid mixtures containing either ethylene or ethane have been investigated, at one or more temperatures (usually at the triple-point temperature of the component with the higher melting-point). In the ethylene series liquid-vapour equilibrium and liquid density studies were carried out for mixtures with methane, krypton and xenon; the heats of mixing were also measured for the ethylene + krypton mixtures. In the ethane series, which comprised mixtures with methane, argon, krypton and xenon, all three properties were measured except for the ethane + methane and ethane + argon systems where the enthalpies of mixing were already known. The ethylene + ethane system was also investigated at 161.39 K.

The results have been used to estimate the thermodynamic excess functions G^E , V^E and H^E . The G^E values decrease, within each series, as one moves from the lighter to the heavier rare gas, the values being lower in the ethane series. For the ethane + xenon mixtures both G^E and H^E are negative, showing a weak attraction between the two molecules. The V^E values for the mixtures of hydrocarbons suggest the probable formation of interlocking structures between the two components.

The values of the thermodynamic excess functions have been interpreted in the light of the model of Frisch-Longuet Higgins-Widom for the liquid state.     

AUTOXIDATION OF PACKED ROASTED ALMONDS AS AFFECTED BY TWO PACKAGING FILMS

Peeled and unpeeled almonds of Romana and Pizzuta varieties of almonds were roasted and packed under vacuum conditions, using two films having different barrier effects against O₂. The almonds were stored for eight months at room temperature in the dark and, at regular intervals, were analyzed to study the progress in lipid oxidation. Results showed that almond oxidation strongly depended on packaging: the film with the highest barrier effect against O₂ was able to better preserve almonds. With reference to Romana almonds, peeled almonds were slightly more oxidized than unpeeled almonds especially in the last phase of the storage. In the case of Pizzuta almonds, the difference between peeled and unpeeled nuts was more evident. The results of chemical and instrumental analyses were confirmed by the judgements of the panel test, pointing out a more positive evaluation for the Romana variety of almonds.     

Strength and toughness of sintered plus forged T1 high speed steel

The stresses for macroscopic plastic flow and critical stages of fracture, fracture toughness and hardness of sintered plus forged T1 high speed steel were determined. The results are compared to similar data for sintered, sintered to closed porosity plus hot isostatically pressed and electroflux refined (EFR) alloys of comparable composition. EFR meltstock, with addition of 0.6 wt% Mo, was water-atomized in a 200 kg unit which incorporated ceramic filters and an argon shroud to ensure maximum cleanliness. The powder was sieved, <125 μm, vacuum annealed, blended, isostatically compacted and vacuum sintered and hot forged to produce a 300 kg billet. Mechanical properties were determined in four-point bending of heat-treated beam specimens. Most samples showed evidence of macroscopic plastic flow, up to ∼1%, beyond a stress of ∼1.8 GPa, σY. Using surface replica microscopy, crack nucleation was detected at stresses σN, between 0.5 and 0.9 σY, and subcritical short crack growth, at stresses generally larger than σY. Fracture, from crack nuclei associated (only) with fractured M6C carbides, took place at stresses, σF, in the range 1.4 to 3.0 GPa Macroscopic fracture toughness, KIC, was in the range 17–24 MPa m1/2 and, like σN and σF, appeared to depend sensitively on the tempering temperature. The most attractive combination of properties, for the overtempered, 580°C, structure at HV50 ∼750 appears to be: σY≈1.9 GPa, σF≈2.8 GPa, KIC≈23 MPa m1/2. These values are comparable to those for EFR aerospace quality T1 high speed steel. This revised version was published online in November 2006 with corrections to the Cover Date.