Purees freeze-thawing

Freeze-thaw resistance + Pure polymer cements absorb essentially no water [82]... 

Alvarez, M. D., Canet, W. (2001b). Rheological properties of frozen vegetable purees. Effect of freeze-thaw cycles and thawing conditions. Fur. Food Res. Technol., 213, 30-37. 

Figure 2 Decay of viability of microbial cultures as a function of the number offreeze-thaw cycles in the cryocycler. Viable cells (CFU/ml) in cultures derived from one of the soils (first light bar in each cycle set) were compared to pure cultures of P. chlororaphis (grey, second bar in each cycle set) or E. coli (black, third bar in each cycle set). In this series of experiments only the soil culture survived 48 freeze-thaw cycles. Error bars represent standard deviations.

Freeze-thaw cycles are rough on library plates too. If the seal on every well isn t perfect and if the plates aren t immediately transferred to a dessicator upon removal from the freezer, water from condensation can get into the DMSO solutions, changing concentrations and perhaps accelerating hydrolysis. What isn t always appreciated is that even though pure DMSO freezes at 18°C, mixtures of DMSO and water can remain liquid even below —70°C. Putting thawed-out plates containing such mixtures back into a freezer at —20°C will not cause them to re-freeze, and compound degradation will probably be accelerated. 

In this chapter, only a few of the most common forms of physical and chemical deterioration of concrete wiU be mentioned (effects of freeze-thaw cycles, acid solutions, pure water, sulfates and aUcaH aggregate reactions). Other forms of deterioration, such as the action of certain aggressive liquids, while important in specific cases, wiU not be dealt with. For more details, the reader is referred to the classic Hterature on degradation of concrete, which has formed the source of usefiil information for many decades [1, 2]. Modern reference texts and standards rely for a large part on these classic sources [3, 4]. 

However, the activity of the pure FNR can be recovered when diluted prpeparations of the enzyme are frozen and thawn several times in Tris/ HCl buffer or phosphate buffer. This recovery of activity is partially inhibited in the presence of 20% glycerol in the freezing-thawing mixture (table 1). 

The pure presence of biofilms alone may already cause detrimental effects on constructional materials. They may cause clogging of porous systems or form a slimy layer on the surface. The high water content retained in the EPS matrix of biohlms may increase the water content of porous materials resulting in an increased risk of a freeze-thaw attack. 

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