Frozen gelatinized systems

Glass Transition Temperatures in Frozen Gelatinized Systems.314... 

In the present chapter the effect of sucrose and hydrocolloids (xanthan gum, guar gum, and sodium alginate) on (i) Tg of the freezeconcentrated matrix (7 ), (ii) amylose and amylopectin retrogradation, and (iii) rheological behavior of the system, are analyzed in gelatinized water-starch formulations frozen at different rates and stored at — 18°C. Besides, the importance of Tg as a parameter related to texture quality of starch-sucrose-hydrocolloids-based foods during frozen storage is discussed. 

Before summarizing the reactions generally occurring in proteins irradiated at low temperatures, it is instructive to review some of the major observations that have been made for certain representative proteins. Those selected for illustration are myoglobin, ribonuclease (RNase), the myofibrillar proteins myosin and actomysin, and gelatin. Wherever possible, comparisons will be made between results for fluid and frozen systems. 

Other studies included the investigation of the stabilizing effect of sorbitol on hen egg white lysozyme and the use of the self-diffusion coefficient, D, to follow the solution and aggregative properties of lysozyme at different pH, temperature, and protein and salt concentrations. The properties of frozen ovalbumin solutions were studied by NMR relaxation spectroscopy. It is known that the functional properties of muscle proteins are affected by protein interactions with ions, and NMR was used to assess protein/water, protein/salt, and protein/protein interactions in myofibrillar protein solutions. Previous X-ray and NMR studies on collagen and peptides were reviewed by Mayo and, more recently, such types of system were characterized by high-resolution H and C NMR. °0 The structure, hydration state, and nature of the interactions between water and gelatin were determined by time domain NMR. ... 

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