Effects of Deaeration and Storage Temperature on Quality of Aseptically Packaged Guava Puree

Deaeration of aseptically packaged guava puree did not benefit either color or flavor stability but did aid in the retention of ascorbic acid during the first 6 months of storage. The reduction of headspace O₂ was greatest in the samples stored at 23°C followed by lesser decreases in samples stored at 10° and - 18°C. Sensory panel scores for color, Hunter color values, dissolved O₂, headspace O₂, and ascorbic acid were highly correlated with each other showing that color changes were related to O₂ consumption and ascorbic destruction.     

The elusive ettringite under the high‐vacuum SEM – a reflection based on natural samples,the use of Monte Carlo modelling of EDS analyses and an extension to the ettringite group minerals

Ettringite, Ca₆Al₂(SO₄)₃(OH)₁₂.26H₂O, or C₆A₃H₃₂ as it is known in cement chemistry notation, is a major phase of interest in cement science as an hydration product and in polluted soil treatment since its structure can accommodate with many hazardous cations. Beyond those anthropogenic features, ettringite is first of all a naturally occurring mineral (although rare). An example of its behaviour under the scanning electron microscope and during energy dispersive spectroscopy (EDS) qualitative analysis is presented, based on the study of natural ettringite crystals from the N'Chwaning mine in South Africa. Monte Carlo modelling of the electron‐matter interaction zone at various voltages is presented and confronted with actual, observed beam damage on crystals, which burst at the analysis spot. Finally, theoretical energy dispersive spectroscopy spectra for all the ettringite group minerals have been computed as well as Monte Carlo modelling of the electron‐matter interaction zone. The knowledge of the estimation of the size of this zone may thus be helpful for the understanding of energy dispersive spectroscopy analysis in cement pastes or ettringite‐remediated soils.     

Groundwater Quality Monitoring in Relation to On-site Sanitation in Developing Countries

Groundwater quality monitoring is considered to be an essential component of any sanitation programme where simultaneous groundwater abstraction and on-site waste disposal are proposed. The low priority currently accorded to monitoring programmes reflects inexperience of monitoring in general and consequent misconceptions about the content and benefits of groundwater quality monitoring.
The purpose of this paper is two-fold. Firstly to explain why groundwater quality monitoring is a requisite component of all pilot sanitation projects which involve on-site disposal of human excreta. Secondly, to demonstrate that it is not unrealistic to expect groundwater quality monitoring to be carried out in relation to all such pilot projects.
The resource constraints inherent in developing countries need not prohibit routine monitoring. However, it is important to define clearly the specific objectives of any monitoring programme and to design a sampling network appropriate to both these objectives and the site conditions. Monitoring must not be confused with initial assessment of prevailing conditions, nor with research studies, for which the aims, duration, technical complexity, and hence investment, are quite different.
Monitoring is a process which can evolve with increased investment to address various questions regarding the causes, nature and processes of groundwater contamination.     

EXPOSURE OF LISTERIA MONOCYTOGENES TO FOOD AND TEMPERATURE ABUSE USING A DIALYSIS TUBING CULTURE METHOD

Foodborne illnesses are often linked to foods that have been contaminated postprocessing and exposed to temperature abuse conditions prior to consumption. Limitations in methods to recover sufficient numbers of a target bacterium from an (inoculated) intentionally contaminated food can hinder genomic/proteomic analysis, and in conducting in vitro assays using the recovered cells. In this study, a dialysis tubing culture technique was developed to facilitate the recovery of high numbers of Listeria monocytogenes exposed to temperature abuse while in association with chocolate milk and frankfurter slurry. The impact of exposure to foods, followed by temperature abuse, on the virulence of L. monocytogenes was investigated using the Caco‐2 cell infection assay. The expression of groEL, associated with stress, was also determined. L. monocytogenes inoculated into brain–heart infusion (BHI) broth (control), chocolate milk or frankfurter slurry was held at 4C for 24 h to simulate short‐term exposure to each food. The L. monocytogenes‐contaminated food was then exposed to a series of temperature shifts to simulate temperature abuse. The final temperature of the abused BHI and chocolate milk was 30C, and the frankfurter slurry was 22C. The stress response gene, groEL, was only induced in the control cells (suspended in BHI) after they had been exposed to temperature abuse conditions. The expression of groEL was also evident in cells exposed to foods and temperature abuse conditions, suggesting that the foods used in this study were a stressful environment for the cells. This study showed that the exposure of L. monocytogenes to chocolate milk or frankfurter slurry, or temperature abuse has no impact on the virulence of L. monocytogenes as demonstrated using the Caco‐2 cell assay. However, the expression of groEL suggests that the foods evaluated can be stressful environments for L. monocytogenes despite its ability to grow or survive in those foods. The dialysis tubing culture technique developed is a simple and highly cost‐effective method for exposure of bacteria to food and the recovery of a large number of cells suitable for additional analysis.     

Conductivity Behavior of High-Silica Glasses with Varied Concentrations of Sodium Ions

The low-frequency conductivity of silica glasses containing 5% B₂O₃ and from 0.02 to 6.7% Na₂O is extrapolated to dc values and analyzed in terms of temperature and concentration dependence. The concentration dependence of the conductivity occurs exclusively in the activation enthalpy. This prevents an analysis of the number of ions participating in the conduction in all but one sample for which tracer diffusion data gave a correlation factor of unity in the Nernst-Einstein equation. The concentration dependence of the activation enthalpy was analyzed empirically. The activation enthalpy varies linearly with sodium-sodium separation or jump distance. This result suggests that, at low Na concentrations, the conducting ions execute several separate motions between nonequilibrium sites before reaching the nearest equivalent site. The empirical equation is shown to fit activation energy data for silica glasses containing from 0.06 to 40% Na₂O.