Requirements cryoprotective effects

Sucrose and sorbitol are commonly used in frozen surimi processing. However, sucrose imparts a sweet taste to surimi products, which is undesirable to the consumer (Sych et al., 1990 Auh et al., 1999 Sultanbawa and Li-Chan, 2001). Thus, the use of other cryoprotectants to reduce sweetness but exhibit the equivalent cryoprotective effect is required. Auh et al. (1999) used highly concentrated branched oligosaccharide mixture (HBOS) as cryoprotectant in fish protein. An addition of HBOS resulted in the remainder Ca -ATPase activity of actomyosin extracted from Alaska pollock after freeze-thawing the best stabilization effect of HBOS was observed at a concentration of 8%. Sych et al. (1990) studied the cryoprotective effects of lactitol dehydrate, polydextrose, and palitinit at 8% (w/w) in cod surimi in comparison with an industrial control (sucrose/sorbitol, 1 1). The... 

Vemuri et al.17 looked at the effects of various cryoprotectants, freezing rates, and buffer systems on the shelf-life of lyophilized recombinant alphar antitrypsin (rAAT). Alpharantitrypsin (AAT) is labile in solution therefore, a more stable presentation was required. A competitive ELISA was used to measure total AAT in a sample. The AAT in the sample competed with HRP-labeled AAT for binding to the specific antibody. A stable formulation containing lactose as a cryoprotectant was found that maintained the protein s specific activity. 

The concentrated salt solution may denature the proteins (9-17, 169-177). Whereas experiments with isolated muscle protein preparations cannot exclude the effects of salts such as NaCl or KC1 (since they are required to solubilize the proteins), denaturation during frozen storage has been decreased or prevented completely when an efficient cryoprotectant such as sodium glutamate or glucose was added (66,67,82,93,145-150). Hence, the effect of salts may not be of primary importance, though they may contribute. 

In preparation for bone marrow transplantation, autologous hemopoietic stem cells are normally frozen in liquid nitrogen after harvesting. However, a cryoprotective agent is required, and dimethylsulfoxide is normally used. During and immediately after stem cell infusion, many adverse effects, which may be severe or life-threatening, have been reported. They include hypotension and hjrpertension, anaphylactic reactions, and cardiac and respiratory failure, all possibly due to dimethylsulfoxide, hemolysis induced by cryopreservation and thawing, and fluid overload. 

The book by Douzou on cryobiochemistry provides an excellent discussion of the types of solvents that are suitable for low-temperature studies. The need for investigating the effects of low temperatures on various solvents other than water was for cryoprotection of the dissolved proteins and the requirement for optically transparent samples. Samples even as thin as around 0.1 cm polycrystalline ice do not transmit light well however, if glycerol is added to about 60-75% (v/v), a clear glass is formed at about 200 K. 

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