The trade-off between taxi time and fuel consumption in airport ground movement

Environmental impact is a very important agenda item in many sectors nowadays, which the air transportation sector is also trying to reduce as much as possible. One area which has remained relatively unexplored in this context is the ground movement problem for aircraft on the airport’s surface. Aircraft have to be routed from a gate to a runway and vice versa and it is still unknown whether fuel burn and environmental impact reductions will best result from purely minimising the taxi times or whether it is also important to avoid multiple acceleration phases. This paper presents a newly developed multi-objective approach for analysing the trade-off between taxi time and fuel consumption during taxiing. The approach consists of a combination of a graph-based routing algorithm and a population adaptive immune algorithm to discover different speed profiles of aircraft. Analysis with data from a European hub airport has highlighted the impressive performance of the new approach. Furthermore, it is shown that the trade-off between taxi time and fuel consumption is very sensitive to the fuel-related objective function which is used

Active Whey Protein Edible Films and Coatings Incorporating Lactobacillus buchneri for Penicillium nordicum Control in Cheese

Fungal contamination of food is responsible for health issues and food waste. In this work, the incorporation of a lactic acid bacteria (LAB) with antifungal properties (Lactobacillus buchneri UTAD104) into whey protein-based films and coatings was tested for the control of an ochratoxigenic fungi (Penicillium nordicum) in a cheese matrix. The incorporation of L. buchneri cells resulted in thicker films with less luminosity than control films and colour alteration. Nevertheless, cells inclusion did not alter moisture content, water vapour permeability, mechanical properties, hydrophobicity and chemical structure of the films. Whey protein films were able to maintain the viability of L. buchneri UTAD104 cells in 105 CFU/mL after 30 days of storage at 25 \textdegreeC. When applied in cheese, films and coatings containing L. buchneri cells prevented fungal contamination for at least 30 days, while control cheeses with films and coatings either without LAB or with Lactobacillus casei UM3 (a strain without antifungal ability) showed fungal contamination during that period. Ochratoxin A was not found in cheeses treated with films and coatings containing L. buchneri UTAD104. Results showed that the inclusion of a LAB with antifungal properties in edible films and coatings can help to reduce or eliminate P. nordicum contamination in cheeses.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UIDB/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte. Ana Guimarães received support through grant SFRH/BD/103245/2014 from the Portuguese FCT.info:eu-repo/semantics/publishedVersio

Impact of milk protein type on the viability and storage stability of microencapsulated Lactobacillus acidophilus using spray drying

Three different milk proteins — skim milk powder (SMP), sodium caseinate (SC) and whey protein concentrate (WPC) — were tested for their ability to stabilize microencapsulated L. acidophilus produced using spray drying. Maltodextrin (MD) was used as the primary wall material in all samples, milk protein as the secondary wall material (7:3 MD/milk protein ratio) and the simple sugars, d-glucose and trehalose were used as tertiary wall materials (8:2:2 MD/protein/sugar ratio) combinations of all wall materials were tested for their ability to enhance the microbial and techno-functional stability of microencapsulated powders. Of the optional secondary wall materials, WPC improved L. acidophilus viability, up to 70 % during drying; SMP enhanced stability by up to 59 % and SC up to 6 %. Lactose and whey protein content enhanced thermoprotection; this is possibly due to their ability to depress the glass transition and melting temperatures and to release antioxidants. The resultant L. acidophilus powders were stored for 90 days at 4 °C, 25 °C and 35 °C and the loss of viability calculated. The highest survival rates were obtained at 4 °C, inactivation rates for storage were dependent on the carrier wall material and the SMP/d-glucose powders had the lowest inactivation rates (0.013 day−1) whilst the highest was observed for the control containing only MD (0.041 day−1) and the SC-based system (0.030 day−1). Further increase in storage temperature (25 °C and 35 °C) was accompanied by increase of the inactivation rates of L. acidophilus that followed Arrhenius kinetics. In general, SMP-based formulations exhibited the highest temperature dependency whilst WPC the lowest. d-Glucose addition improved the storage stability of the probiotic powders although it was accompanied by an increase of the residual moisture, water activity and hygroscopicity, and a reduction of the glass transition temperature in the tested systems

Drying colloidal systems: laboratory models for a wide range of applications

The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art

Encapsulation of Lactobacillus rhamnosus GG in microparticles: Influence of casein to whey protein ratio on bacterial survival during digestion

International audienceEncapsulation of Lactobacillus rhamnosus GG in various microparticles made of only milk proteins (casein, native whey and/or denatured whey proteins) was done. The microparticles obtained were rather similar in shape (mostly round) and size (around 60 mu m) whatever the formulation but the obtained gel presented different elasticity (varying between 61 and 96 Pa). An original equipment involving a granulo-morphometer coupled to a thermostated reactor was developed and validated to visualize in situ the microparticles during digestion. Although the initial particles were similar, their disintegration in simulated gastric media was totally different and characterized by two stages. An initial decrease in particle size more or less quick depending on the protein composition was followed by a stable phase characterized by the particle size and shape retention. At the end of gastric digestion, a significant amount of intact particles was still noticeable for each formulation. Nevertheless, the formulation containing a mix of casein and denatured whey presented the best bacterial survival (99%) and encapsulation rate (97%) in comparison with formulations containing either only casein or casein and native whey or casein in mixture with native and denatured whey proteins. Industrial relevance: This paper is part of a global project entitled ``Structured dairy matrices to enhance probiotic efficiency''. The entire project will provide milk structured matrices allowing the stabilization and the vectorization of Lactobacillus rhamnosus GG (LGG). This project will consist of four main axes: milk constituent's interactions with LGG, stabilization process implementation, and structural and functional characterization of the matrices obtained. The scientific objective is to propose models connecting process parameters, matrix structure (from an atomic, molecular to a macro scale) and their functionality. This implies the in-depth study of interactions between milk components and probiotic strain. For this purpose, the use of genetically modified strain of LGG will allow the identification of biomolecules interacting with milk matrices. The industrial aims are to optimize and control the processes to suit the needs of industrial criterions: encapsulation rate, gastric resistance, intestinal release, storage in the final food...

High-throughput screening approach to evaluate the adhesive properties of bacteria to milk biomolecules

International audienceAdhesive interactions between bacteria and food have been increasingly studied in the last decades for probiotic bacteria especially in order to improve their protection and to help with biopreservation. The new approach described here has been designed to screen quickly a hundred of strains for their affinity differences for a given range of biomolecules. This method involves three steps: the biomolecules of interest are immobilized on microplates; the strains are then incubated on these microplates and non-adherent strains are removed by successive washes. Culture medium is then added and bacterial growth monitored through optical density measurements. The correlation between the time at which bacterial growth starts on the immobilized biomolecules and bacterial affinity for these biomolecules was first established. The method was then validated using the model strain Lactobacillus rhamnosus GG and three mutant strains lacking surface components involved in adhesion. The affinity of these strains was estimated for six dairy biomolecules. The method demonstrated that bacterial affinity can highly vary between different milk biomolecules. Affinity differences were mainly due to the presence or absence of bacterial surface biomolecules such as pili and exopolysaccharides. These findings may help with the understanding of the behavior of bacteria when incorporated into dairy foods

Food Matrix Design for Effective Lactic Acid Bacteria Delivery

International audienceThe range of foods featuring lactic acid bacteria (LAB) with potential associated health benefits has expanded over the years from traditional dairy products to meat, cereals, vegetables and fruits, chocolate, etc. All these new carriers need to be compared for their efficacy to protect, carry, and deliver LAB, but because of their profusion and the diversity of methods this remains difficult. This review points out the advantages and disadvantages of the main food matrix types, and an additional distinction between dairy and nondairy foods is made. The food matrix impact on LAB viability during food manufacturing, storage, and digestion is also discussed. The authors propose an ideal hypothetical food matrix that includes structural and physicochemical characteristics such as pH, water activity, and buffering capacities, all of which need to be taken into account when performing LAB food matrix design. Guidelines are finally provided to optimize food matrix design in terms of effective LAB delivery