Antimicrobial effects of chitosans and chitooligosaccharides, upon Staphylococcus aureus and Escherichia coli, in food model systems

The objective of this study was to elucidate the controversial relationship between the molecular weight (MW) of chitosans and their antibacterial activity (upon different inoculum levels, at several concentrations). The influence of food components on the activity was also ascertained, as well as acceptance by a sensory panel. All the compounds tested exhibited antibacterial activity against Staphylococcus aureus and Escherichia coli. This activity was shown to be closely dependent on the inoculum level, MW and concentration used. Within 4h at 10(3) cells/mL, all five compounds, at every concentration (0.5%, 0.25% and 0.1%, w/v), proved to be bactericidal; for higher inocula, 0.1% (w/v) was only bacteriostatic; at 10(7) or 10(5) cells/mL, and independently of the inoculum level, 0.25% (w/v) of any chitooligosaccharide (COS) mixture was sufficient to reduce the E. coli initial population by at least 3 log cycles; COS never exhibited bactericidal action over S. aureus, unlike high and medium MW chitosans-which, at 0.5% (w/v), presented a bactericidal effect even against 10(7) cells/mL. When incorporated in liquid food matrices, medium and high MW chitosans maintained their activity, for both matrices and bacteria, although a slower activity was noticeable in milk; however, COS lost their activity upon both bacteria in milk after 4-8h. Furthermore, addition of chitosans to apple juice led to several unpleasant off-flavors, such as astringency and after taste--which increased in magnitude with MW.     

Has a non‐native cichlid of the genus Amatitlania (Actinopterygii,Cichlidae) adapted to the headwaters in Brazilian semi‐arid?

Several fish species from Central America and other regions have been introduced into Brazil. In this study, we evaluated the bioecological aspects of a non‐native cichlid of the genus Amatitlania (convict cichlid) and its possible establishment in high‐altitude forest enclaves of semi‐arid Northeastern Brazil. Specimens of Amatitlania nigrofasciata (Günther, 1867) were captured in a local stream displaying abiotic conditions like those of its natural range of distribution. The individuals collected were predominantly adult, insectivorous and displayed normal length–weight relationships, although we observed some phenotypical plasticity (variation in body depth, and a morphologically abnormal dorsal fin in three cases). Our results indicate that A. nigrofasciata has successfully colonized an Atlantic forest enclave in the Brazilian semi‐arid region, making it necessary to adopt measures to prevent the species from spreading to other water bodies in the surroundings.     

Linking Drought Indicators to Policy Actions in the Tagus Basin Drought Management Plan

One crucial aspect of drought management plans is to establish a link between basin drought state and management actions. Basin state is described by a drought indicator system that includes variables like precipitation, streamflow, reservoir inflow, reservoir storage and groundwater piezometric levels. Basin policy consists on a catalogue of management actions, ranging from enforcing demand reduction strategies to establishing priority of users to allocate scarce water or approving emergency works. In this paper, the methodology applied in the Tagus Basin Drought Management Plan to link operational drought indicators to policy actions in regulated water supply systems is presented. The methodology is based on the evaluation of the probability of not being able to satisfy system demands for a given time horizon. A simplified model of every water resources system in the basin was built to evaluate the threshold of reservoir volume that is required to overcome the drought situation without deficit. For each reservoir level, a set of policy actions is proposed with the goal of guaranteeing essential demands during drought conditions. The methodology was validated with a simulation of system behavior for 60 years of historic streamflow series, finding acceptable results in most systems.     

Interactive effects of abiotic,hydrological and anthropogenic factors on fish abundance and distribution in natural run‐of‐the‐river shallow lakes

Ecological processes in lowland rivers are mostly dominated by hydrology and its interactions with other environmental factors. Fish–habitat relationships in rivers are also influenced by human impacts. In this study, we describe patterns of abundance and distribution of fish species in a group of natural lowland river lakes along spatial anthropogenic and abiotic gradients when four hydrologically different summers are compared. We also describe the proportion of the total variances in fish species abundances that can be accounted for by selected abiotic (water conductivity), hydrological (water residence time) and human activity‐derived (total phosphorus (TP) concentration and NO₃:NH₄) variables. Consequently, our main purpose is to explore how abiotic and anthropogenic factors interact to affect fish abundance and distribution together with consistent results across different hydrological conditions. We conclude with a briefly discussion of some management implications. The anthropogenic impacts on water quality, the extreme hydrological variability and the fluctuating abiotic environment affected fish abundance and distribution. Pampa inland silverside Odontesthes bonariensis was benefited from a less human disturbed environment with higher water residence time and total salinity, whereas species as Cyphocharax voga, Parapimelodus valenciennis and Cyprinus carpio found these conditions largely disadvantageous. On the other hand, while most species showed stronger—either negative or positive—response to anthropogenic, hydrological or abiotic factors Oligosarcus jenynsii was only slightly affected. This paper identified the ecological function of a lowland river under its natural flow regime. There are not many opportunities to study unmodified rivers worldwide. Therefore, our findings may help in assessment programmes of fish communities in flow altered and human disturbed aquatic ecosystems. Copyright © 2008 John Wiley & Sons, Ltd.     

Initial appraisal of water quality of Lake Santa Ana,Mexico

Lake Santa Ana is located in the Mexican central plateau, a semiarid region characterized by low rainfall and high evaporation rates. Because of the area's climatic conditions, most of its few existing lakes and reservoirs are ephemeral, with significantly reduced surface areas during the dry season. Mexican authorities currently pay little or no attention to these special aquatic ecosystems. As a consequence, several of these waterbodies are severely degraded in regard to both water quantity and quality. As a result, this report describes Lake Santa Ana as a case study. Several water quality parameters, including physicochemical, microbiological and heavy metal concentrations, were measured at eight sampling sites in the lake, and four sites in the lake basin, in 2005. Some dissolved ions were also analysed in 2007 in the lake, and in a well located close to the lake, in order to evaluate possible interactions between groundwater and surface waters. These study results indicate that the lake does not have significant interactions with groundwater in the local aquifer. Most of the measured water quality parameters do not meet the international suggested standards for inland surface waters to sustain aquatic life, and preserve the habitat for both endemic and migratory waterfowl. Loss of aquatic habitats puts at risk the value of the central portion of Mexico as a migratory route for North American waterfowl species.     

Hydrogeographical Regionalisation: An Approach for Evaluating the Effects of Land Cover Change in Watersheds. A Case Study in the Cuitzeo Lake Watershed, Central Mexico

Efficient natural resources management, including continental water at watershed level, requires understanding the arrangement of landscape attributes in a region. The geographical analysis of landscape attributes is a useful approach to delineate relatively homogeneous watersheds or regions. This research was carried out in order to evaluate the effect of land cover through time on regionalisation modelling in the poorly-gauged Cuitzeo Lake Watershed, and to develop models to create two hydrogeographical regionalisations for the years 1975 and 2000. The inputs required by the regionalisation methodology were integrated in a GIS and validated before carrying out statistical regionalisation procedures (cluster analysis and PCA). GIS operations were done in Arc View 3.2 and statistical analyses in PC-ORD. Median Euclidean distances with mean distance linkage methods were used. A 75% of similarity was chosen as the threshold to generate regions. Importance rankings of regions were obtained using multicriteria evaluation methods. Based on the analysis, 38 of the 52 subwatersheds belonging to the Cuitzeo Lake Watershed were clustered; eight groups were defined in 1975 and nine in 2000. According to PCA, the strongest positive variables are associated to morphometric, geologic, land cover and soil attributes. Fourteen subwatersheds were never clustered. Four subwatersheds changed of cluster between 1975 and 2000. This change is explained because of rainfed agricultural parcel abandonment, and subsequent shrubland growth. This means that the hydrogeographical regionalisation is sensitive to land cover change processes. The methodological approach applied in this research is a low-cost and fast alternative for evaluating the impact of land cover and land use change on hydrogeographical regionalisation; in consequence, data and information generated during the analysis were made available to local authorities so that they can improve both water resources planning and their informational baseline for decision making and for development of environmental policies in the Cuitzeo Lake Watershed.     

Comparison of volatile components in raw and cooked green beans by GC-MS using dynamic headspace sampling and microwave desorption

 The effects of four culinary treatments (steaming and boiling in a covered pot, a pressure cooker or a microwave oven) on the volatile component profile of green beans were evaluated. Volatile compounds in raw and cooked beans were analysed by means of dynamic headspace sampling onto an adsorbent, followed by microwave desorption into a gas chromatograph equipped with a mass spectrometric detector. Twenty-seven compounds were identified, including alcohols, aldehydes, ketones, esters, terpenes, sulphur compounds and alkenes. All of the thermal treatments caused important changes in the volatile compound profile in particular an increase in carbonyl compounds and a decrease in alcohol compounds, most notably in the case of the covered pot. It is concluded that the change in aroma during the cooking of green beans depends on compounds from lipid oxidation as well as compounds from other types of reactions, for instance the Strecker degradation. Received: 8 March 1999 / Revised version: 23 April 1999     

The performance of forced convection greenhouse driers

An analytical study of the evaporation rate in two types of forced convection greenhouse driers, the single and the double chamber systems, is presented. A performance parameter defined to compare both driers and its dependence on the operational variables is studied introducing the concept of the characteristic function. The drying curve is calculated and a time scale change is introduced to reduce the curves obtained under different operational conditions to a single generalized drying curve. Simulation tests for red pepper are presented showing that the use of a double chamber drier improves the productivity by almost 90%.     

Spatial and Time Variability of Drought Based on SPI and RDI with Various Time Scales

The spatial and temporal variability of droughts were studied for the Northeast Algeria using SPI and RDI computed with monthly precipitation data from 123 rainfall stations and CFSR reanalysis monthly temperature data covering the period 1979–80 to 2013–14. The gridded temperature data was interpolated to all the locations having precipitation data, thus providing to compute SPI and RDI with the time scales of 3-, 6- and 12-month with the same observed rainfall data. Spatial and temporal patterns of droughts were obtained using Principal Component Analysis in S-Mode with Varimax rotation applied to both SPI and RDI. For all time scales of both indices, two principal components were retained identifying two sub-regions that are similar and coherent for all SPI and RDI time scales. Both components explained more than 70% and 74% of drought spatial variability of SPI and RDI, respectively. The identified sub-regions are similar and coherent for all SPI and RDI time scales. The Modified Mann-Kendall test was used to assess trends of the RPC scores, which have shown non-significant trends for decreasing drought occurrence and severity in both identified drought sub-regions and all time scales. Both indices have shown a coherent and similar behavior, however with RDI likely showing to identify more severe and moderate droughts in the southern and more arid sub-region which may be due to its ability to consider influences of global warming. Results for RDI are quite uniform relative to time scales and show smaller differences among the various climates when compared with SPI. Further assessments covering the NW and NE of Algeria using longer time series should be performed to better understand the behavior of both indices.     

Domestic refrigeration practices with emphasis on hygiene: analysis of a survey and consumer recommendations

A Web-enabled survey was conducted to improve knowledge of home refrigeration practices of French consumers (n = 809), with an emphasis on hygiene, and this information was used to establish recommendations. The survey targeted a convenience sample of working people. Analysis of the survey responses revealed that efforts should be directed toward improvement of microbiological control measures. Only 37% of respondents made sure the temperature in their refrigerator was 4 degrees C or below. Only 37% of respondents reported that they systematically wrapped food. Sponges, known to be frequently highly contaminated, were used by 89% of the respondents to clean their refrigerator, which indicates the need to recommend disinfection of sponges before they are used for cleaning. Twenty-seven percent of respondents used sodium hypochlorite (bleach), but it was applied without previous cleaning (21% of the users) or in the commercial concentrated form (7% of the users). The permanent presence of water condensation on the shelves was noted by 2% of respondents, suggesting imperfect closure of the door, with a consequence of higher energy consumption and water available for microbial circulation and growth. Thus, an important recommendation is to check the door gaskets and to ensure the tight closure of the door. Seventy percent of the respondents declared that they never put warm or hot food in the refrigerator. However, many people, when orally questioned, acknowledged that they leave dishes at ambient temperature overnight before putting them in the refrigerator. It therefore is essential to recommend that perishable food not be left for more than 2 h at ambient temperature.