The aim of this study was to investigate the inactivation of nonpathogenic Escherichia coli in nutrient broth and milk through the use of either ultrasound (US) alone or US combined with nisin (US + nisin) treatments. The E. coli cells were treated at 0 to 55°C, 242.04 to 968.16 W/cm for 0 to 15 min. The results showed that the inactivation of E. coli by US and US + nisin increased when the temperature, US power density, and treatment time were increased. The inactivation kinetics of E. coli in nutrient broth by US and US + nisin both conformed to linear models. The largest reductions of 2.89 and 2.93 log cycles by US and US + nisin, respectively, were achieved at 968.16 W/cm and at 25°C for 15 min. The suspension media of the E. coli cells influenced the inactivation effect of US, while the growth phases of E. coli cells did not affect their resistance to US. Under all experiment conditions of this study, the differences between US and US + nisin in their respective inactivation effects on E. coli were not obvious. The results suggested that nisin had either no effect at all or a weak synergistic effect with US and that the E. coli cells were inactivated mainly by US, thus indicating that the inactivation of E. coli by US is an "all or nothing" event.

Engineering properties are of great importance for Cassia tora L. seeds in aspects of harvesting, handling mechanical design and product processing. The effect of moisture content (7, 10, 13, 16 and 19%) (wet basis) on the properties: physical (length, width, bulk and true density, porosity, thousand seeds mass, coefficient of static friction and angle of repose), mechanical (hardness, fragmentation energy and failure deformations), and thermal (specific heat, thermal conductivity and thermal diffusivity), were systematically studied. As the moisture contents increase from 7 to 19%, the length (L) increased from 4.52 to 5.87 mm, the thickness (T) from 2.51 to 3.21 mm and the width (W) from 2.36 to 3.02 mm, respectively. The bulk and true density of Cassia tora L. seeds decreased from 775.83 to 654.17 kg/m3 and from 1295.21 to 1154.72 kg/m3, respectively, with the moisture content raised from 7 to 19%. The thermal conductivity of Cassia tora L. seeds meal was found to be 0.068–0.098 W m−1 K−1, 0.078–0.112 W m−1 K−1, 0.089–0.125 W m−1 K−1, 0.098–0.136 W m−1 K−1, 0.108–0.148 W m−1 K−1, 0.119–0.159 W m−1 K−1, respectively, at 25 °C, 45 °C, 65 °C, 85 °C, 105 °C and 125 °C in moisture ranges of 7–19%. The thermal diffusivity was found to decrease from 5.21 × 10–8 to 4.53 × 10–8 m2/s, from 5.75 × 10–8 to 4.91 × 10–8 m2/s, from 6.11 × 10–8 to 5.17 × 10–8 m2/s, from 6.52 × 10–8 to 5.36 × 10–8 m2/s, from 7.17 × 10–8 to 5.77 × 10–8 m2/s, from 7.36 × 10–8 to 5.84 × 10–8 m2/s, respectively, at 25 °C, 45 °C, 65 °C, 85 °C, 105 °C and 125 °C in moisture ranges of 7–19%. The results suggested that physical properties exhibited linear relationships with moisture content using the regression model, while mechanical properties showed a second-order polynomial relationship with moisture content. Furthermore, significant variation existed in thermal properties because of differentiate moisture content and temperature. These data and rules are also useful for high efficiency machines design and mechanisms development.

No abstract

Engineering properties are of great importance for Cassia tora seeds in aspects of harvesting, handling mechanical design and product processing. The effect of moisture content on the physical, mechanical and thermal properties of Cassia seeds was systematically investigated in this study. Specifically, physical properties (length, width, bulk and true density, porosity, thousand seeds mass, coefficient of static friction and angle of repose), mechanical properties (hardness, fragmentation energy and failure deformations), as well as thermal properties(specific heat, thermal conductivity and thermal diffusivity), were systematically studied under five levels of moisture content (7 %, 10 %, 13 %, 16 % and 19 %) (wet basis). As the moisture contents increase from 7 % to 19 % (w.b.), the length (L) increased from 4.52 to 5.87 mm, the thickness (T) from 2.51 to 3.51 mm and the width (W) from 2.36 to 3.02 mm, respectively. The bulk density and true density of Cassia tora seeds decreased from 775.83 to 654.17 kg/m3 and from 1295.21 to 1154.72 kg/m3, respectively, with the moisture content raised from 7% to 19% (w.b.). The thermal conductivity of Cassia tora seeds meal was found to be 0.068- 0.098 W·m-1·K-1, 0.078- 0.112 W·m-1·K-1, 0.089- 0.125 W·m-1·K-1, 0.098- 0.136 W·m-1·K-1, 0.108- 0.148 W·m-1·K-1, 0.119- 0.159 W·m-1·K-1, respectively, at 25 °C, 45 °C, 65 °C, 85 °C, 105 °C and 125 °C in moisture ranges of 7 %- 19 %. The thermal diffusivity was found to decrease from 5.21×10-8 to 4.53×10-8 m2/s, from 5.75×10-8 to 4.91×10-8 m2/s, from 6.11×10-8 to 5.17×10-8 m2/s, from 6.52×10-8 to 5.36×10-8 m2/s, from 7.17×10-8 to 5.77×10-8 m2/s, from 7.36×10-8 to 5.84×10-8 m2/s, respectively, at 25 °C, 45 °C, 65 °C, 85 °C, 105 °C and 125 °C in moisture ranges of 7 %- 19 %. The results suggested that physical properties exhibited linear relationships with moisture content using the regression model, while mechanical properties showed a second-order polynomial relationship with moisture content. Furthermore, significant variation existed in thermal properties because of differentiate moisture content and temperature. These data and rules are also useful for high efficiency machines design and mechanisms development.