Heat And Mass Transfer In Vitrification Of Bio-And-Food Materials

Vitrification (glass formation) is an advanced technique for low temperature preservation of biological cells and tissues, and cold storage of food materials as well; however, it is quite difficult to vitrify those aqueous systems. This paper discusses heat and mass transport and cell injury during freezing and thawing; analyses three main methods of cryopreservation and concludes that vitrification is the unique mechanism among these methods; reviews and investigates glass formation kinetics of single component system and complex aqueous solution system, and methods of determining critical cooling rate V-cc for vitrification during cooling and critical warming rate V-cw for preventing devitrification during warming; develops a new technique of ultra-rapid cooling; researches the heat transfer performance of small samples quenching into subcooled liquid nitrogen, in which the critical heat flux can be enhanced to 2x10(6) W/m(2) and the cooling rate can be increased to 1.2x10(4) Ws; invents a new technique - "cryomicroscopy-DSC (differential scanning calorimetry) system" to measure accurately the partial glass transition temperature T-g', as well as discusses its applications in cold storage of foods.