The Potential of Proteins for Producing Food Packaging Materials: A Review

The problems associated with obtaining conventional plastic materials and with their accumulation have led to a constant search for new materials derived from renewable sources. Materials made from proteins stand out among them all because of the many ways in which they can be modified enzymatically, chemically or physically, giving rise to materials with improved physicochemical properties that are adjustable to each specific application. This paper reviews the state of the art with regard to the use of proteins for the manufacture of packaging materials, including: the main protein sources that have been used; manufacturing methods (coating on conventional materials, thermoforming, extrusion), with special emphasis on materials made by extrusion; possible strategies for improving the physicochemical properties of the materials and the main future prospects and limitations of materials of this kind.     

Unsteady MHD free convection of a micropolar fluid between two parallel porous vertical walls with convection from the ambient

The present work is concerned with the unsteady free convection flow of an incompressible electrically conducting micropolar fluid, bounded by two parallel infinite porous vertical plates submitted to an external magnetic field and the thermal boundary condition of forced convection. The governing equations are solved using a numerical technique based on the electrical analogy, where only previous spatial discretization is necessary to obtain a stable and convergent solution with very low computational times. To solve the system of algebraic equations with time as continuous function, an electric circuit simulator is used. This method permits the direct visualization of the local and/or integrated transport variables (temperatures and velocities) at any point or section of the medium. Numerical results for temperature, velocity and microrotation are illustrated graphically.     

Preparation of quercetin glucuronides and characterization by HPLC–DAD–ESI/MS

Quercetin is the main flavonol in the human diet, and the most commonly used in studies of biological activity. The major circulating forms of quercetin found in the human plasma after consumption of food containing distinct quercetin glycosides are glucuronides and sulfates. In this work quercetin glucuronides have been obtained from green beans (quercetin 3-glucuronide) and by enzymic synthesis (quercetin 4′-glucuronide) using a modification of the method described by Plumb et al. (Methods in polyphenol analysis, The Royal Society of Chemistry, Cambridge, pp 187, 2003) so as to improve the original low yields of that methodology. The method finally optimised got yields of 19% in the preparation of quercetin 4′-glucuronide, which allows its further isolation for their use in biological assays. In addition, quercetin 3′-glucuronide, 3-glucuronide and a diglucuronide were synthesised with lower yields. The compounds prepared have been employed to perform assays in order to obtain data for their identification by HPLC coupled to photodiode array detection and tandem mass spectrometry. It was observed that the analysis by HPLC–ESI/MS/MS could allow the identification of different quercetin glucuronides based on the presence of some minor key MS² fragments.     

Hierarchical silicalite-1 structures based on pyrolized materials

The synthesis of silicalite-1 layers on pyrolyzed wood bodies with a desired shape was studied. The synthesis procedure is based in an “in situ” hydrothermal treatment of a precursor gel in which the support is immersed. Two different calcination methods were carried out, using a flow of air or N₂ and air. Samples were characterized by means of X-ray diffraction, thermogravimetric analyses and N₂ adsorption/desorption isotherms, revealing the existence of a micro/mesoporous hierarchical silicalite-1 structure.     

Expert system design for vacant parking space location using automatic learning and artificial vision

Multimedia Tools and Applications - Finding a free parking space nowadays is a recurring problem in increasingly crowded public parking lots. The present study offers a solution that is based on...     

Synthesis of Open Zeolite Structures from Mixtures of Tetramethylammonium and Benzylmethylalkylammonium Cations: A Step Towards Driving Aluminium Location in the Framework

Three bulky organic cations, benzylmethylpyrrolidinium (BMP), (S,S)-2-hydroxymethyl-1-benzyl-1-methylpyrrolidinium (BML) and benzylmethylhexamethyleniminium (BMH), were used in combination with the small cation tetramethylammonium (TMA) in the synthesis of zeolite materials. Two of them are distinguished by the number of carbon atoms forming the cyclic amine, which varies from 4 in BMP to 6 in BMH. In addition, a –CH₂–OH group has been introduced in the carbon atom belonging to the amine ring next to the nitrogen atom, to originate a chiral molecule, BML, the third SDA used in this work. It has been found that the combination of the small TMA with those three bulkier SDAs, promotes the crystallization of zeolite structures that contain cages and channels. BMP leads to the crystallization of the 10-ring zeolite ferrierite, where TMA is located inside the ferrierite cage. If the size of the N-cyclic amine moiety increases, the resulting cation cannot be accommodated in the relatively narrow 10-ring channels of ferrierite, and in these cases the zeolite MCM-22 crystallizes. This zeolite contains large cages whose cross section is delimited by a 12-ring, where both BMH and BML can be easily accommodated. In this system, cage-like, chlatrasil type structures often co-crystallize with the open structures, evidencing that an appropriate balance between TMA and the bulky SDA is required to achieve the crystallization of open-frameworks. When BMP is used, mixtures of structurally related ferrierite and cage-like RUB-10 are obtained if an excess of TMA is present in the synthesis gel, while MCM-22 crystallizes together with the structurally related cage-like MTN phase.     

Influence of homogenisation conditions and drying method on physicochemical properties of dehydrated emulsions containing different solid components

Dehydrated o/w emulsions containing sodium caseinate and lactose (sample 1), and gelatine, sucrose and maltodextrin (DE 10) (sample 2) were used to study the influence of homogenisation conditions – homogenisation pressure (15 and 70 MPa) and number of passes (1 and 2) – and the drying method – spray‐drying vs. freeze‐drying – on physicochemical parameters, including oil microencapsulation efficiency (ME), oil droplet size in reconstituted emulsions, water activity, glass transition temperature, powder bulk density and time for emulsion reconstitution in water. Results showed that small and uniform oil droplets attained with increased homogenisation pressure were not sufficient for high oil encapsulation. The permeability of the solid wall to the extraction solvent appeared to be the dominant factor, and this may increase with homogenisation pressure. With the exception of oil droplet size in sample 1 and ME in sample 2, the drying method exerted larger changes in the physicochemical parameters studied than the homogenisation pressure. For sample 2, significant changes in the ME were not observed between the freeze‐dried and spray‐dried samples, even though a great emulsion destabilisation was observed in the reconstituted emulsion of the latter.     

Counting pedestrians with a zenithal arrangement of depth cameras

Counting people is a basic operation in applications that include surveillance, marketing, services, and others. Recently, computer vision techniques have emerged as a non-intrusive, cost-effective, and reliable solution to the problem of counting pedestrians. In this article, we introduce a system capable of counting people using a cooperating network of depth cameras placed in zenithal position. In our method, we first detect people in each camera of the array separately. Then, we construct and consolidate tracklets based on their closeness and time stamp. Our experimental results show that the method permits to extend the narrow range of a single sensor to wider scenarios.     

Biomass Thermogravimetric Analysis: Uncertainty Determination Methodology and Sampling Maps Generation

The objective of this study was to develop a methodology for the determination of the maximum sampling error and confidence intervals of thermal properties obtained from thermogravimetric analysis (TG), including moisture, volatile matter, fixed carbon and ash content. The sampling procedure of the TG analysis was of particular interest and was conducted with care. The results of the present study were compared to those of a prompt analysis, and a correlation between the mean values and maximum sampling errors of the methods were not observed. In general, low and acceptable levels of uncertainty and error were obtained, demonstrating that the properties evaluated by TG analysis were representative of the overall fuel composition. The accurate determination of the thermal properties of biomass with precise confidence intervals is of particular interest in energetic biomass applications.