ABSTRACT
High pressure technology is the outcome of demand for better quality control of biomaterials. It is hoped that the technology will demonstrate advantages over conventional thermal treatments in terms of processing time, end-product acceptability attributes, ice-crystal tissue damage, etc. The present treatise deals with the effect of high hydrostatic pressure on the rubber-to-glass transformation of biomaterials with potential industrial interest in confectionery formulations. Early studies in pressure-induced functionality were based on the classical free volume theory which in conjunction with the Ferry-Stratton equation was unable to rationalize the pressure dependence of mechanical properties at constant temperature. Incorporation of the correct pressure dependence of the compressibility coefcient led to the Fillers-Moonan-Tschoegl equation, which followed the combined thermorheologically and piezorheologically simple behaviour of amorphous synthetic polymers. Work in this laboratory demonstrated the utility of the sophisticated “synthetic polymer approach” in the time-temperature superposition of mechanical functions of biomaterials undergoing vitrication. Nevertheless, the time-temperature-pressure equivalence of synthetic materials is not operational in the glass-like behaviour of high sugar systems in the presence of gelatin or gelling polysaccharides. This deviation from the “normal” course is discussed in terms of the irreversible destabilization of intermolecular aggregates (mainly) in polysaccharide networks following pressure-induced vitrication.
