Isolation and characterization of ice structuring proteins from cold-acclimated winter wheat grass extract for recrystallization inhibition in frozen foods

Antifreeze proteins have shown a great potential in improving the quality of frozen foods, and the isolation of proteins from natural sources that are readily available is deemed to be important. The raw leaf apoplastic extract from cold-acclimated winter wheat grass ( Triticum aestivum ) containing recrystallization inhibition (RI) proteins was screened for proteolytic and lipolytic activity, and a heat-stable RI protein was isolated. The enzymes detected could be easily removed by heat treatment without any loss in the RI activity. The RI protein was isolated after heat treatment of the raw extract, alcohol precipitation and separation on a size exclusion chromatographic column. Circular dichroism indicated that the RI protein was mainly β-sheet and random coil, and these structures were preserved up to 75C. After trypsin digestion, mass fingerprinting and sequencing of the digests revealed that the protein belongs to the thaumatin-like protein group

Effect of Aging and Ice Structuring Proteins on the Morphology of Frozen Hydrated Gluten Networks

The present investigation constitutes an attempt to rationalize the effect of aging and ice structuring proteins (ISPs) on the network morphology of frozen hydrated gluten. In doing so, it employs differential scanning calorimetry, time-domain NMR, dynamic oscillation on shear, creep testing, and electron microscopy. Experimentation and first principles modeling allows identification and description of the processes of ice formation and recrystallization in molecular terms. It is demonstrated that in the absence of a readily discernible glass transition temperature in gluten−ice composites, the approach of considering the melting point and aging at constant or fluctuating temperature conditions in the vicinity of this point can provide a valid index of functional quality. A theoretical framework supporting the concept of capillary confined frozen water in the gluten matrix was advanced, and it was found that ISPs were effective in controlling recrystallization both within these confines and within ice in the bulk