Citrate increases glass transition temperature of vitrified sucrose preparations.

The aim of this study was to investigate the effect of sodium citrate on the properties of dried amorphous sucrose glasses. Addition of sodium citrate to a sucrose solution followed by freeze-drying or convective drying resulted in a glass transition temperature (Tg) that was higher than the well-studied sucrose Tg. This result was obtained either at reduced water content of the analysed sample or by removal of water during Modulated DSC analysis. After removal of the remaining water ( < 3.5% w/w), a Tg of approximately 105 degrees C was obtained at a mass ratio of sodium citrate to sucrose of 0.3. FTIR analysis showed a similar increase in Tg as was found with Modulated DSC analysis. The Tg values were derived from breaks in the vibrational frequency vs. temperature plots in the OH stretching and bending regions. Elevated average strength of hydrogen bonding in the sucrose/citrate glass was concluded from the downshift of the OH stretching band of 25 cm(-1) and from the reduced wavenumber temperature coefficient (WTC). The antisymmetric carboxylate stretch of citrate sensed the glass transition of the mixture, from which we conclude that citrate interacts with the sucrose OH via its carboxylate groups.

High-oxygen and high-carbon dioxide containing atmospheres inhibit growth of food associated moulds.

AIMS: The objective of this study was to determine the relationship between the growth of three foodborne fungi and high-oxygen modified atmosphere. METHODS AND RESULTS: Petri dishes were incubated in a series of connected flasks, which were placed in a climatized room and flushed continuously with the desired gas atmosphere. A combination of 80% oxygen and 20% carbon dioxide resulted in reduced growth of Rhizopus stolonifer, Botrytis cinerea and Penicillium discolor compared with ambient atmosphere conditions. Combining 80% oxygen and 20% carbon dioxide at 10 degrees C arrested growth of B. cinerea for 17 d while an elevated carbon dioxide concentration only inhibited growth up to 11 d. In addition, the peroxidase activity was doubled at 80% oxygen and decreased when 10% carbon dioxide was present. IMPACT OF THE STUDY: This study demonstrates the potential use of elevated oxygen levels in a modified atmosphere to inhibit food-associated mould growth.