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Essid I.,National Agronomic Institute of Tunisia | Essid I.,Research Unity Food and Science Technologies UR 04 AGR02 | Hassouna M.,Research Unity Food and Science Technologies UR 04 AGR02
Food Control | Year: 2013

In this study, a selected starter culture of Lactobacillus plantarum and Staphylococcus xylosus was used for the manufacture of a traditional Tunisian dry fermented sausage. Changes of microbiological, biochemical, sensorial and textural characteristics during the ripening of sausages were investigated.Counts of lactic acid bacteria and staphylococci were significantly higher in inoculated sausages than in control ones. Moreover, the acidifying activity of the selective L. plantarum strains improved the hygienic quality of fermented sausages by reducing counts of Enterobacteriaceae. Both a significant decrease in pH and a significant increase in nitrite contents were observed in inoculated sausages compared to control ones. The loss of moisture during the ripening of sausages was not affected by the use of starters. Proteolysis and lipolysis were observed both in control and in inoculated sausages; however, these activities during ripening could be due to the activity of starter culture enzymes or the activity of meat endogenous enzymes. The Factorial Discriminative Analyze (FDA) of sensorial parameters (aroma, color, taste and firmness) discriminate clearly inoculated sausages from non-inoculated ones. In fact, inoculated sausages showed a more intensive red color, related to the production of nitrosomyoglobin pigment, and an acid flavor. Finally, textural parameters of sausages were not affected by the use of the selective starters. © 2013 Elsevier Ltd. Source

Hiddink J.G.,Bangor University | Ben Rais Lasram F.,National Agronomic Institute of Tunisia | Cantrill J.,Bangor University | Davies A.J.,Bangor University
Global Change Biology | Year: 2012

Species need to move to keep pace with changing climates, but we do not know if species can move at the required speed. Spread rates of native species may underestimate how fast species can move, we therefore assessed how fast Lessepsian species (marine non-native species that invaded the Mediterranean from the Red Sea through the Suez Canal) can spread to give a 'best-case' assessment of the effects of climate change on marine biodiversity. We show that about 20% of Lessepsian species could not spread fast enough to keep pace with climate change in about 20% of the global seas and this suggests that climate change may lead to biodiversity loss. The velocity of climate change on the seabed is much lower than at the sea surface, and as a result of this the proportion of species that keep pace with climate change at the seabed was much larger than at the sea surface. This suggests that locations at depth could act as refuges for slow dispersing species. Our analysis compared different estimates of the spreading abilities of marine species and showed that the estimate of spread rates strongly affects the predicted effect of climate change on biodiversity. Providing more accurate estimates of the spreading ability of marine species should therefore have priority if we want to predict the effect of climate change on marine biodiversity. This study is a first approximation of the potential scale and distribution of global marine biodiversity loss and can provide benchmark estimates of the spread rates that species could achieve in colonizing suitable habitat. Assisted colonization may be required to maintain biodiversity in the most strongly affected areas. © 2012 Blackwell Publishing Ltd. Source

Guettaya I.,National Agronomic Institute of Tunisia | El Ouni M.R.,National Agronomic Institute of Tunisia | Moss R.E.S.,Polytechnic University of Mozambique
Soil Dynamics and Earthquake Engineering | Year: 2013

This paper presents a case study of liquefaction potential assessment for the foundation of an earth dam in Tunisia. An emphasis was made on the exploration of geotechnical conditions and the interpretation of field tests (SPT and CPT) and the results were collected before and after soil densification using the vibrocompaction technique. The assessment of soil liquefaction triggering was made using deterministic and probabilistic simplified procedures. The results indicate that before vibrocompaction the studied area was prone to the liquefaction hazard. However, after vibrocompaction a significant improvement of the soil resistance reduced the liquefaction potential of the sandy foundation soil. The SPT resistance values increased on average from 12 to 25 blow counts/0.3. m, and the CPT resistance increased on average from 8. MPa to 14. MPa. Before vibrocompaction, the factor of safety (FS) against liquefaction fell below 1.0, which means that the soil is susceptible for liquefaction. After vibrocompaction the values of FS exceed the unit which justified the liquefaction mitigation efforts in dam foundation.© 2013. Source

Slimen I.B.,Preparatory Institute for Scientific and Technical Studies | Slimen I.B.,National Agronomic Institute of Tunisia | Najar T.,Preparatory Institute for Scientific and Technical Studies | Najar T.,National Agronomic Institute of Tunisia | And 4 more authors.
International Journal of Hyperthermia | Year: 2014

In recent years there has been enormous interest in researching oxidative stress. Reactive oxygen species (ROS) are derived from the metabolism of oxygen as by-products of cell respiration, and are continuously produced in all aerobic organisms. Oxidative stress occurs as a consequence of an imbalance between ROS production and the available antioxidant defence against them. Nowadays, a variety of diseases and degenerative processes such as cancer, Alzheimer's and autoimmune diseases are mediated by oxidative stress. Heat stress was suggested to be an environmental factor responsible for stimulating ROS production because of similarities in responses observed following heat stress compared with that occurring following exposure to oxidative stress. This manuscript describes the main mitochondrial sources of ROS and the antioxidant defences involved to prevent oxidative damage in all the mitochondrial compartments. It also deals with discussions concerning the cytotoxic effect of heat stress, mitochondrial heat-induced alterations, as well as heat shock protein (HSP) expression as a defence mechanism. © 2014 Informa UK Ltd. Source

Zghibi A.,National Agronomic Institute of Tunisia | Zouhri L.,Polytechnic Institute of LaSalle Beauvais | Tarhouni J.,National Agronomic Institute of Tunisia | Kouzana L.,Minerals Resources and Environement Laboratory
Hydrological Processes | Year: 2013

The groundwater of the Korba plain represents major water resources in Tunisia. The Plio-Quaternary unconfined aquifer of the Cap-Bon (north-east Tunisia) is subject to the intensive agricultural activities and high groundwater pumping rates due to the increasing of the groundwater extraction. The degradation of the groundwater quality is characterized by the salinization phenomena. Groundwater were sampled and analysed for physic-chemical parameters: Ca2+, Mg2+, Na+, K+, Cl-, SO4 2-, HCO3 -, NO3 -, pH, electrical conductivity (EC), and the temperature (T°). The hydrochemical analysis is coupled with the calculation of the saturation indexes (SI gypsum, SI halite, SI calcite and SI dolomite), ionic derivation and with the ion correlations compared to chloride concentrations: Na+/ Cl-, Ca2+/ Cl- and Mg2+/ Cl- ratios. Seawater fractions in the groundwater were calculated using the chloride concentration. Those processes can be used as indicators of seawater intrusion progression. EC methods were also conducted to obtain new informations on the spatial scales and dynamics of the fresh water-seawater interface of coastal groundwater exchange. The mixing zone between freshwater and saltwater was clearly observed from the EC profile in the investigated area where a strong increase in EC with depth was observed, corresponding to the freshwater and saltwater interface. Results of hydrochemical study revealed the presence of direct cation exchange linked to seawater intrusion and dissolution processes associated with cations exchange. These results, together with EC investigation, indicated that the groundwater is affected by seawater intrusion and is still major actor as a source of salinization of the groundwater in Korba coastal plain. Further isotopic and hydrological investigations will be necessary to identify and more understood the underlying mechanisms. © 2012 John Wiley & Sons, Ltd. Source

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