Stabilization of aroma compounds through sorption-release by packaging polymers

Plastic packaging materials are often associated to aroma losses and to a decrease of the organoleptic quality of foods. This work defines situations where, on the contrary, plastics play a regulating role on the concentration of reactive aroma compounds in foods. These systems can be described by a two step mechanism; first, aroma is sorbed in the polymer, while the fraction in solution degrades quickly; in a second step, as the concentration is close to zero in the solution, the polymer liberates progressively the sorbed aroma back to the food. A simple numerical model is proposed, describing competitive processes of aroma degradation in solution and sorption by a polymer in contact with a homogeneous aqueous food. The classical limonene/low density polyethylene (LDPE) system is studied experimentally for the validation of the model: in an acidic medium, limonene both degrades quickly and is sorbed quickly, with a large solubility in LDPE. To define which aroma packaging systems could also display this interesting behavior, all types of possible interactions, using thermodynamic and kinetic parameters describing most practical situations, are simulated. For that purpose, 35 values of reference diffusion coefficients and 35 partition coefficients of usual aroma compounds between polymers and water have been measured and combined with the few available data from literature. The situations where polymers regulate the aroma concentration in food correspond to large partition coefficients (above 10), large diffusion coefficients (>10(-9) cm2 x s(-1)), and large degradation constants.     

Matching avrami indices achieves similar hardnesses in palm oil-based fats

This study demonstrates how chemically interesterified hydrogenated palm oil (IHPO) and partially hydrogenated palm oil (PHPO) can be structured to have similar mechanical properties. Crystallization of IHPO at 30 degrees C for 24 h yielded a fat with a solid fat content (SFC) of 45% and a yield force of 51.5 N. On the other hand, PHPO had a SFC of 50% and a yield force of 44 N when crystallized under the same conditions. The result was opposite from what would be expected from the SFC point of view, thus suggesting that the microstructure of the fat plays a key role in determining mechanical properties. By matching crystallization behavior using the Avrami index as a guide, microstructures and material hardness were successfully matched. These results suggest that the dynamics of structure formation was a key factor influencing the macroscopic mechanical properties of palm oil-based fats.     

The application of remote-sensing data to monitoring and modelling of soil erosion

This paper gives a brief synthesis of the information obtainable from remote-sensing data and how it can be related to two significant functions of catchment hydrology, namely, the processes of production and transfer. After presenting examples of the type of information that can be derived from remote sensing (characterisation of soil surface by different wavelengths, temporal changes of surface states, incision and geometry of possible water pathways on the surface, etc.), we examine how this information can provide parameters for input into runoff and erosion models. Finally, we assess the progress in assimilating remote-sensing data into deterministic models of storm runoff.     

The Promoter of the Tnt1A Retrotransposon: A Biomarker to Monitor Ozone but not Formaldehyde and Benzene Pollution

Open top chambers (OTCs) are useful tools to assess the impact of atmospheric pollutants on plants in the natural environment. We have previously reported that, in tomato plants, the LTR-GUS construct derived from the Tnt1A promoter of tobacco was activated by a realistic level of ozone pollution. In this study, we used OTCs to fumigate tomato plants with benzene or formaldehyde in order to assess the impact of these pollutants on plant growth and development and evaluate the usefulness of the LTR-GUS construct as a biomarker in plants. Whereas the LTR-GUS construct could be used as an efficient biomarker of realistic levels of ozone pollution, it is to a lesser extent applicable to formaldehyde. Indeed, only unrealistic concentration of pollutant activated the construct though important injuries were observed at a lower concentration. For benzene, no activation could be demonstrated, however, we did not notice any visual impact on plant growth and health for this pollutant.     

Quantification of beta casein in milk and cheese using an optical immunosensor

beta-Casein was quantified in milk and cheese, using an optical immunosensor, based on surface plasmon resonance (SPR) measurement. The assay consists of a two-step sandwich strategy, with two anti-beta-casein antibodies directed against each extremity of the casein. This strategy permits only native beta-casein to be quantified and not its degradation products. The calibration curve was obtained with a reference milk powder of known beta-casein concentration. The analysis time per sample was less than 10 minutes. The antibody-coated surface could be used for more than 250 determinations. The detection limit was established at 85 ng x mL(-)(1) and the intra- and inter-assay variation coefficients were 2.6 and 6.2% respectively. The method was applied to raw milk to quantify intact beta-casein, with no pretreatment of the sample. A second application was realized with cheese, to follow the proteolysis of beta-casein during ripening.     

Severe modifications in source-sink ratio influence the susceptibility of bananas to crown rot and its phenolics content

Banana susceptibility to crown rot is influenced by many biotic and abiotic preharvest factors, which include source-sink (So-Si) ratio modifications through trimming of leaves and fruit. Banana plant's resistance to biotic stress has been previously correlated to its phenolic content; it is hypothesized that the crown's phenolic content may influence the fruit's susceptibility. The aim of this work was to investigate the influence of severe So-Si ratio modifications, via the removal of leaves and fruit, and the involvement of phenolics in the fruit's susceptibility to crown rot. Fruit susceptibility was evaluated 13 days postinoculation (13 dpi) with Colletotrichum musae. Banana crowns obtained on the day of harvest before inoculation (dhbi) and 13 dpi were analysed for changes in phenolics using GC-MS, HPLC, and LC-MS devices. Severe So-Si ratio modifications had a significant effect (p <.001) on susceptibility, fruits of low So-Si ratio being most susceptible. It also significantly influenced (p < .001) some tree and fruit characteristics. The less susceptible (S−) crowns had higher amounts of phenolics compared to the more susceptible (S+) ones. Catecholamines were identified as the major phenolics in banana crown, notably dopamine compared to norepinephrine and normetanephrine. Hydroxycinnamic acids (ferulic acid and its derivatives) were significantly accumulated (p <.001) the dhbi in S− crowns compared to S+ crowns, but decreased 13 dpi. Phenolics have a possible role in the biochemical defence of banana crown and could be used by producers as a chemical criterion for estimation of the level of banana's susceptibility to crown rot.     

How does forest fragmentation affect tree communities? A critical case study in the biodiversity hotspot of New Caledonia

Context

The biodiversity hotspot for conservation of New Caledonia has facing high levels of forest fragmentation. Remnant forests are critical for biodiversity conservation and can help in understanding how does forest fragmentation affect tree communities.

Objective

Determine the effect of habitat configuration and availability on tree communities.

Methods

We mapped forest in a 60 km² landscape and sampled 93 tree communities in 52 forest fragments following stratified random sampling. At each sampling point, we inventoried all trees with a diameter at breast height ≥10 cm within a radius of 10 m. We then analysed the response of the composition, the structure and the richness of tree communities to the fragment size and isolation, distance from the edge, as well as the topographical position.

Results

Our results showed that the distance from the forest edge was the variable that explained the greatest observed variance in tree assemblages. We observed a decrease in the abundance and richness of animal-dispersed trees as well as a decrease in the abundance of large trees with increasing proximity to forest edges. Near forest edges we found a shift in species composition with a dominance of stress-tolerant pioneer species.

Conclusions

Edge-effects are likely to be the main processes that affect remnant forest tree communities after about a century of forest fragmentation. It results in retrogressive successions at the edges leading to a dominance of stress-tolerant species. The vegetation surrounding fragments should be protected to promote the long process of forest extension and subsequently reduce edge-effects.

     

Acceptance of Innovation and Pathways to Transition Towards More Sustainable Food Systems

The main driver of agricultural systems of the twentieth century was yield. Awareness of the limits of the planet and the impacts of agriculture triggered the realization that new objectives have to be part of the food systems agenda. The development of new models of agriculture including environmental and sustainability dimensions implies a new view on the process of innovation and a better balance between the paradigms of innovation. Systemic lock-ins are keeping the agricultural and food systems on less relevant pathways. Acknowledgement of the relevance of alternative systems of production such as organic farming and a shift from a linear model of innovation diffusion to the building up of new partnerships of innovation are key enablers of a transition.     

A minimal model of the variability of marine ecosystems

In marine ecology, population abundance time series often reveal patterns, such as decadal pseudo-cycles, on scales that make them difficult to mathematically characterize by means of conventional models based on functional responses. We propose here a simple non-deterministic model based on three strong ecological constraints, without any use of functional responses or external factors: (i) mass balance constraints between flows and biomass, (ii) a satiation constraint relating inflows and biomass and (iii) an inertia principle restricting the variation of populations of a given species according to its lifespan. This model reproduces in a robust manner observed patterns of variability and can be used to question the relevance of other modelling approaches of ecosystem dynamics with regard to determinism, constraints and stochasticity. Referring to a non-deterministic model without any functional relationships and environmental or anthropogenic forcing can help in avoiding misleading advice based on the belief that we can explain the causes of observed patterns, which may simply result from basic structural constraints within which the ecosystem functions.     

Qualitative modelling and indicators of exploited ecosystems

Implementing ecosystem-based fisheries management requires indicators and models that address the impacts of fishing across entire ecological communities. However, the complexity of many ecosystems presents a challenge to analysis, especially if reliant on quantification because of the onerous task of precisely measuring or estimating numerous parameters. We present qualitative modelling as a complementary approach to quantitative methods. Qualitative modelling clarifies how community structure alone affects dynamics, here of exploited populations. We build an array of models that describe different ecosystems with different harvesting practices, and analyse them to predict responses to various perturbations. This approach demonstrates the utility of qualitative modelling as a means to identify and interpret community-level indicators for systems that are at or near equilibrium, and for those that are frequently perturbed away from equilibrium. Examining the interaction of ecological and socio-economic variables associated with commercial fisheries provides an understanding of the main feedbacks that drive and regulate exploited ecosystems. The method is particularly useful for systems where the basic relationships between variables are understood but where precise or detailed data are lacking.