Water and Glycerol as Plasticizers Affect Mechanical and Water Vapor Barrier Properties of an Edible Wheat Gluten Film

Glycerol improved film extensibility but reduced film puncture strength, elasticity, and water vapor barrier properties. The plasticizing effect of water was highly temperature dependent. During hydration of gluten film, a sharp decrease in puncture strength, elasticity, and an increase of extensibility and water vapor transmission rate were observed at 5, 30 and 50°C for respective water contents of 30 (0,8 a_w,), 15 (0,7 a_w) and 5% (0,4 a_w). This was related to disruptive water-polymer hydrogen bonding and glass-to-rubber transition.     

EFFECT OF HOST DEFENSE CHEMICALS ON CLONAL DISTRIBUTION AND PERFORMANCE OF DIFFERENT GENOTYPES OF THE CEREAL APHID <Emphasis Type="Italic">Sitobion avenae</Emphasis>

Five microsatellite loci were used to study the genetic variability and population structure of Sitobion avenae (Hemiptera: Aphididae) on some of its host plants. Individuals were collected in Chile from different cultivated and wild Poaceae. Forty-four multilocus genotypes were found among the 1052 aphids analyzed, of which four represented nearly 90% of the sample. No specialist genotypes were found, although some preferred hosts endowed with chemical defenses, i.e., hydroxamic acids (Hx), while others preferred comparatively undefended hosts. Performances of some predominant and some rare genotypes were evaluated on plants differing in their Hx levels. Significant differences in performance were found among clones, the two most common genotypes showing no differences in performance among all hosts tested, and the rare genotypes showing enhanced performance on the host with highest Hx level. A hypothesis is proposed whereby the appearance of rarer genotypes is in part related to the presence of Hx.     

Edible composite films of wheat gluten and lipids: water vapour permeability and other physical properties

Edible composite films comprised of wheat gluten as the structural matrix and various concentrations of different lipids as the moisture barrier component were tested for water vapour permeability, dispersion in water, opacity and mechanical properties. the effects of lipids on the functional properties of gluten-based composite films depended on the lipid characteristics and on the interactions between the lipid and the protein structural matrix. Beeswax, a solid and highly hydrophobic lipid, was the most effective lipid for improving moisture barrier properties of films; but these films were opaque, weak and disintegrated easily in water. Combining wheat gluten proteins with a diacetyl tartaric ester of monoglycerides reduced water vapour permeability, increased strength and maintained transparency.     

Management of a pool of self-service cars

This paper deals with the problem of self-service cars arising in large companies where cars are at the employees' disposal to travel between different company sites. This problem also occurs in some big cities where electric cars are available for customers to make local journeys. The employee (or the customer) uses the car to travel from one site to another, and leaves it there so that other employees (or customers) can use it. This customer will use another car to travel to another site, if necessary. In this paper, we restrict ourselves to the case where the random variables which generate car requirements in a given site are independent identically distributed (i.i.d.) random variables, and we study the behaviour of the system according to a balancing strategy.     

Edible Wheat Gluten Films: Influence of the Main Process Variables on Film Properties using Response Surface Methodology

An edible wheat gluten film was developed and effects of gluten concentration, ethanol concentration (ET) and pH of the film-forming solution on various film properties were evaluated using Response Surface Methodology. pH and ethanol concentration had strong interactive effects on film opacity, water solubility and water vapor permeability. A simultaneous variation of ethanol concentration and pH between 32.5% ET, pH 4 and 45% ET, pH 2 resulted in homogeneous and transparent film with relatively low water solubility. The lowest water vapor permeability would be expected with 20% ethanol concentration and pH 6. Mechanical properties were mainly affected by gluten concentration and pH. The most resistant film was obtained at high gluten concentration (12.5%) and pH 5.     

UPLC MS/MS Quantification of Primary Metabolites of Benzo[a]pyrene and Fluoranthene Produced In Vitro by Sole (Solea solea) Liver Microsomal Activation

Biotransformation pathways of PAHs in a flat fish, Solea solea, living in nurseries close to coastal areas and estuaries constitute a great challenge for the environmental risk. Among PAHs, Fluoranthene (Fluo) has a different chemical structure than benzo[a]pyrene (BaP), and can influence its biotransformation pathways and genotoxic potential. The aim of this study was to bring some response elements about the in vitro metabolic activation of Fluo and BaP by sole liver microsomes. The quantification of several primary metabolites of BaP and Fluo produced in vitro, following a sole liver microsomal activation, was conducted using a sensitive analytical UPLC MS/MS method.

Four types of BaP metabolites (dihydrodiols, diones, OH-BaP, and 7,8-dihydro-epoxide), and three types of Fluo metabolites (2,3-dihydrodiol, 2,3-dione, and sum of OH-Fluo) were quantified. The concentration for which the metabolite production was maximal was of 40 μM and 100 μM for BaP and Fluo, respectively. The biotransformation rate was higher for Fluo (9.97%) than for BaP (6.69%).Whatever the PAH, dihydrodiols and phenols were the major metabolites produced accounting for, respectively, 50% and 30–40% for BaP, and 40 and 60% for Fluo. Despite some differences in conformation, both PAHs seem to be activated by similar pathways and the diol-epoxide appears as a predominant one.     

Water vapour permeability of edible bilayer films of wheat gluten and lipids

Various formulations and methods of fabricating edible bilayer films consisting of wheat gluten as a structural layer and a thin lipid layer as a moisture barrier were investigated and examined for water vapour permeability. Solid lipids such as beeswax or paraffin wax deposited in a molten state onto the base film were the most effective water vapour barriers. A film consisting of wheat gluten, glycerol and diacetyl tartaric ester of monoglyceride as one layer, and beeswax as the other yielded a water vapour permeability of 0.0048 g mm m⁻² mmHg⁻¹ 24h⁻¹, which was less than that obtained with low density polyethylene.     

Functional Properties of Myofibrillar Protein-based Biopackaging as Affected by Film Thickness

Fish myofibrillar protein-based biopackagings were developed from a film-forming solution cast on plates. Film thickness was modulated by variations in “apparent thickness” of the cast solution to evaluate effects on the main functional properties. The thickness variations seemed to have no influence on optical properties (apparent opacity) or on percent solubility in water. Study of mechanical properties revealed that elongation at break and relaxation coefficient were not dependent on film thickness, while force at break was directly proportional to film thickness. This could be interpreted by variations in the number of potential intermolecular interactions in the films. Analysis of water vapor transport showed that the biopackaging did not behave as an ideal material according to Fick's and Henry's laws.     

Grapevine fruit set: Physiology of the abscission zone

Effects of ethylene and of 'anti-ethylene' compounds on the floral pedicel abscission zone in grapevines were analysed via a laboratory model consisting of isolated flowers held in Petri dishes. Our model permitted precise determination of abscission and enabled us to test a range of physiologically-active compounds including ethylene precursors, and antagonists of ethylene action. For example, a precursor of ethylene, 1-aminocyclopropane-l-carboxylic acid, had the same effect as ethylene in promoting abscission. Conversely, an inhibition of ethylene action by silver thiosulfate or an inhibition of ethylene synthesis by amino-oxyacetic acid both strongly inhibited abscission zone function. The same type of effect can be obtained by increasing the proportion of auxin with regard to ethylene. The abscission zone of the isolated flower pedicel of grapevine conforms to the classic model of hormone-mediated operation of a pre-existing abscission zone. Our definition of hormone regulation holds practical implications for viticulture and offers new possibilities for controlling berry drop.