Biomedical subjects

Maher Trigui

Publications and source records attributed to Maher Trigui.

3 recordsLinked to original sources

PubMed2004

Rheological behavior of WPI dispersion as a function of pH and protein concentration.

Physical and flow properties of proteins can provide information necessary for the optimal design of unit processes and quality control of the manufacturing process and final products. Therefore, the purpose of this investigation was to characterize the rheological behavior of a whey protein isolate (WPI) (BiPRO) dispersion as a function of pH and protein concentration. A rotational viscometer was used to determine the apparent viscosity, shear rate, and shear stress of WPI dispersions. Both the consistency index (k) and the flow behavior index (n) were sensitive to changes in pH and protein concentration. Mathematical relations obtained from experimental values of k and n allowed the determination of a model for apparent viscosity (eta) of WPI dispersions as a function of pH and protein concentration. At 5 and 10% BiPRO, whatever the pH, the rheological behavior appeared to be a newtonian fluid, while at 20% BiPRO, the rheological behavior appeared to be a nonnewtonian pseudoplastic fluid. Furthermore, at 20% Bipro, the apparent viscosity presented an increase in viscosity from 5.6 to 5.4, followed by a decrease from pH 5.4 to 5.0 at all shear rates. The highest viscosity was obtained at 20% pH 5.4, with an approximate value of 0.25 Pa.s, 10 times higher than the one obtained at 5 and 10% BiPRO.

Analysis of Variance↗

PubMed2003

Compost convective airflow under passive aeration.

For composting, passive aeration can save energy costs while being just as efficient as forced or active aeration. Passive aeration requires the proper design of aeration ducts, and thus, the proper prediction of the convective airflow rates created by the temperature differential between the compost and the ambient air. To establish such relationship, the temperature and convective air flow regimes of composts were investigated using three bulking agents (wood shavings, hay and straw), each at three moisture contents (MC-60%, 65% and 70%) spanning the normal values. All bulking agent and aeration treatments were aerated in duplicate under passive and active regimes. Laboratory vessels of 105 L were used for all treatments. Passive aeration treatments produced temperatures above 57 degrees C, as did the treatments actively aerated at 4 mg of air s(-1) kg(-1) of initial dry compost material. Compost MC had an effect only on the peak compost temperature, occurring between day 2 and 6. After 6 days of composting, MC no longer had any effect on temperature regime because of the loss of moisture by each mixture. A relationship was established between the Grasholf number (Gr-ratio of buoyancy to viscous forces) and the convective airflow rates, to size the aeration ducts for passive aeration. In general, convective airflow rates ranged from 1.5 to 0.7 mg of dry air s(-1) kg(-1) of initial compost dry matter, from day 0 to day 20, respectively, and for all compost treatments. This airflow rate sizes the aeration ducts installed under compost piles for passive aeration. As compared to straw where airflow rate dropped over a given level of Gr, wood shavings and hay were found to be more effective as bulking agents, as their airflow rate increased constantly with Gr.

Air Movements↗

PubMed2002

Effect of carbon source on compost nitrogen and carbon losses.

The effect of C source on N losses by volatilization during composting was measured using four bulking agents, each at three humidity levels and composted in duplicate under passive and active aeration. The bulking agents were pine shavings alone and corrected with soybean, chopped grass hay alone and corrected with urea, long (unchopped) wheat straw and chopped oat straw. The readily available C of each bulking agent was determined by analyzing for BOD5. In 105 l laboratory vessels, the bulking agents were mixed with liquid swine manure and tap water for a C/N of 20 and three humidity levels of 60%, 65% and 70%. While being aerated actively or passively, the mixtures were composted for 21 days. Their initial and final C and N contents were measured to conduct a mass balance analysis and calculate C and N losses. C and N losses were compared to bulking agent BOD5. N losses were compared to C losses. The humidity level and aeration regime had no effect on C and N losses but the N losses were correlated to C losses and only the C losses could be correlated to the BOD5 of the bulking agent. Thus, the N losses are related not only to the availability of C but also to the extent of composting. A relationship established between N and C losses indicated that 85% of the initial total N of the compost was available for microbial degradation and that 70% of the available C was lost as CO2 during the immobilization process.

Air Movements↗