Responses of Living Organisms to Freezing and Drying: Potential Applications in Food Technology

Abstract

Many sugars are involved in the preservation of living organisms. Under thermal or hydric stress conditions, spores, yeasts, and microscopic animals accumulate trehalose, whereas pollen, plant seeds, and resurrection plants synthesize sucrose and oligosaccharides such as raffinose and stachyose. These solutes also have proved to provide stabilization of dried or frozen labile biomolecules in vitro and have potential technological applications for the preservation of special food ingredients, which is obviously of enormous economical importance. The protectants promote the formation of amorphous, glassy systems, inhibit crystallization, and influence the kinetics of reactions responsible for deterioration during storage. There is evidence, however, that the maintenance of a glassy structure is not the only factor controlling biomolecule stability. Anhydrobiotic engineering aims to confer desiccation tolerance on otherwise sensitive living organisms by adopting the strategies of anhydrobiosis, and a large number of genes with a potential role in drought tolerance have been described. Other nature-based methods to protect biomolecules in frozen environments are the manipulation of ice-nucleating agents (INAs) (present in several microorganisms and lichen species) and antifreeze components (characteristic of some Antarctic fish). The former catalyze ice formation at relative warm subfreezing temperatures, and antifreeze polymers act by surface interactions. Cryo and dehydropreservation of biomolecules, which is of technological value, is frequently developed on an empirical basis. In this chapter, how the physical and chemical mechanisms by which anhydrobiotic organisms can tolerate extreme conditions may allow establishing stabilization protocols on a scientific basis is shown.