CO₂ processing and hydration of fruit and vegetable tissues by clathrate hydrate formation

Investigation of crystal growth of CO2 hydrate in aqueous fructose solution for the potential application in carbonated solid foods

CO₂ hydrate is applicable to solid carbonated foods. The hydrate crystal morphology, which represents the crystal size and shape, is an important characteristic that changes the texture of foods. We report an observational study of the crystal growth of CO₂ hydrate in aqueous fructose solution. The difference between the phase equilibrium temperature and the experimental temperature, ΔT_sub, is applied as an index of the driving force. Experiments were performed at ΔT_sub range of 0.9 K to 5.4 K. At all ΔT_sub, initial crystal formed at the gas-solution interface and grew along the interface. After covering the interface, the crystals grew in the liquid phase The individual crystals were identified as polyhedral with facets (ΔT_sub = 0.9 K), skeletal crystals (ΔT_sub = 2.0 K) and dendrites (ΔT_sub = 3.0 K and 5.4 K). Based on these results, the potential effect of gas hydrate morphology on texture of foods has been discussed.

Fast diffraction-enhanced imaging using continuous sample rotation and analyzer crystal scanning

Diffraction-enhanced imaging (DEI) has high sensitivity and a wide dynamic range of density and thus can be used for fine imaging of biological and organic samples that include large differences in density. A fast DEI method composed of continuous fast sample rotations and slow analyzer crystal scanning was developed to shorten the measurement period. Fine sectional images of a biological sample were successfully obtained within a half measurement period of the conventional step-scanning method while keeping the same exposure time. In addition, a fine three-dimensional image of a rat tail was obtained with a 375 s measurement period.

An Optical Microscope Study of the Morphology of Xenon Hydrate Crystals: Exploring New Approaches to Cryopreservation

One of the possible approaches to a new method of cryopreservation seems to be the controlled formation of a multitude of small crystals in an object, which, due to their size, will not damage cellular structures. Managing the crystal formation, given the stochastic nature of the process, is an extremely difficult task. Theoretically, it is simplified if there is a sufficient number of changeable physical parameters, affecting the process. From this point of view, the use of ice-like gas hydrates for the purposes of cryopreservation seems to be a promising option. We investigated the process of growth of xenon gas hydrates via standard microscopy under different conditions using the specialized optical cell for observation at elevated pressures. The formation of crystals was observed in the system “supercooled liquid–xenon–water vapor” at negative, near-zero and positive values of temperature, and pressure of xenon up to 8 atmospheres. The morphology of xenon hydrate crystals observed in the experiments was analyzed and classified into five categories. The influence of physical conditions on the predominant crystal morphology was also studied. We found no evidence that the possible damaging effect of hydrate crystals should be less severe than of ice crystals.

Storage of Methane Gas in the Form of Clathrates in the Presence of Natural Bioadditives

Methane (CH₄) and carbon dioxide (CO₂), the important greenhouse gases, are capable of forming clathrate hydrates under some suitable thermodynamic conditions. The gas storage capacity of these materials is high, and therefore they are often useful in gas storage applications. Certain expensive and toxic chemicals are employed to accelerate/decelerate the process. In this study, we report rapid (∼30-50 min) and effective (∼80%) methane hydrate conversion in the presence of three naturally occurring additives such as dry powders from Nelumbo nucifera (Indian lotus), Piper betle (betel), and Azadirachta indica (neem), at lower concentrations (0.5 wt %). Obtained results were carefully compared with the well-known kinetic promoter (sodium dodecyl sulfate). All the biomaterials are equally good kinetic promoters for methane hydrates, although the required subcooling is significantly large. However, no hydrate formation is observed with CO₂ gas.