Survival and germination of clostridium perfringens spores during heating and cooling of ground pork

The effect of heating rate on the heat resistance, germination, and outgrowth of Clostridium perfringens spores during cooking of cured ground pork was investigated. Inoculated cured ground pork portions were heated from 20 to 75uC at a rate of 4, 8, or 12�C/h and then held at 75�C for 48 h. No significant differences (P > 0.05) in the heat resistance of C. perfringens spores were observed in cured ground pork heated at 4, 8, or 12�C/h. At heating rates of 8 and 12�C/h, no significant differences in the germination and outgrowth of spores were observed (P > 0.05). However, when pork was heated at 4�C/h, growth of C. perfringens occurred when the temperature of the product was between 44 and 56�C. In another set of experiments, the behavior of C. perfringens spores under temperature abuse conditions was studied in cured and noncured ground pork heated at 4uC/h and then cooled from 54.4 to 7.2�C within 20 h. Temperature abuse during cooling of noncured ground pork resulted in a 2.8-log CFU/g increase in C. perfringens. In cured ground pork, C. perfringens decreased by 1.1 log CFU/g during cooling from 54.4 to 36.3�C and then increased by 0.9 log CFU/g until the product reached 7.2�C. Even when the initial level of C. perfringens spores in cured ground pork was 5 log CFU/g, the final counts after abusive cooling did not exceed 3.4 log CFU/g. These results suggest that there is no risk associated with C. perfringens in cured pork products under the tested conditions. � International Association for Food Protection

Panchromatic Response in Solid-State Dye-Sensitized Solar Cells Containing Phosphorescent Energy Relay Dyes

Running relay: Incorporating an energy-relay dye (ERD) into the hole transporter of a dye-sensitized solar cell increased power-conversion efficiency by 29 % by extending light harvesting into the blue region. In the operating mechanism (see picture), absorption of red photons by the sensitizer transfers an electron into TiO2 and a hole into the electrolyte. Blue photons absorbed by the ERD are transferred by FRET to the sensitizer

Pore-Filling of Spiro-OMeTAD in Solid-State Dye Sensitized Solar Cells: Quantification, Mechanism, and Consequences for Device Performance

In this paper, the pore filling of spiro-OMeTAD (2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenylamine)9,9'-spirobifluorene) in mesoporous TiO2 film is quantified for the first time using XPS depth profiling and UV-Vis absorption spectroscopy. It is shown that spiro-OMeTAD can penetrate the entire depth of the film, and its concentration is constant throughout the film. We determine that in a 2.5-mu m-thick film, the volume of the pores is 60-65% filled. The pores become less filled when thicker films are used. Such filling fraction is much higher then the solution concentration because the excess solution on top of the film can act as a reservior during the spin coating process. Lastly, we demonstrate that by using a lower spin coating speed and higher spiro-OMeTAD solution concentration, we can increase the filling fraction and consequently the efficiency of the device