Peter J. Lillford

Potential food applications of high-pressure effects on ice-water transitions

Pressure depresses the freezing point of water and the melting point of ice, as well as enabling various high-density forms of ice to be obtained. These effects of pressure on the solid-liquid phase diagram of water have several potential applications in food technology, including pressure-assisted freezing, pressure-assisted thawing and non-frozen storage at low temperature (under pressure). Studies that have been published in these and in related areas are reviewed, and the potential applications and limitations are highlighted.

Phytochemistry: Heat-stable antifreeze protein from grass

We have discovered an antifreeze protein in an overwintering perennial ryegrass, Lolium perenne. The protein is stable at 100 °C and although it is a less effective antifreeze than proteins found in antarctic fish and insects, it is better at preventing ice recrystallization. This property enables grasses to tolerate ice formation in their tissues without being damaged, suggesting that the control of ice-crystal growth rather than the prevention of freezing may have evolved to be the critical factor in their survival at very low temperatures.

Heat-stable antifreeze protein from grass.

We have discovered an antifreeze protein in an overwintering perennial ryegrass, Lolium perenne. The protein is stable at 100 °C and although it is a less effective antifreeze than proteins found in antarctic fish and insects, it is better at preventing ice recrystallization. This property enables grasses to tolerate ice formation in their tissues without being damaged, suggesting that the control of ice-crystal growth rather than the prevention of freezing may have evolved to be the critical factor in their survival at very low temperatures.

The physico-chemical characterization of a boiling stable antifreeze protein from a perennial grass (Lolium perenne).

We have characterized a cold-induced, boiling stable antifreeze protein. This highly active ice recrystallization inhibition protein shows a much lower thermal hysteresis effect and displays binding behavior that is uncharacteristic of any AFP from fish or insects. Ice-binding studies show it binds to the (1 0 1 0) plane of ice and FTIR studies reveal that it has an unusual type of highly beta-sheeted secondary structure. Ice-binding studies of both glycosylated and nonglycosylated expressed forms indicate that it adsorbs to ice through the protein backbone. These results are discussed in light of the currently proposed mechanisms of AFP action.

Effect of Solutes and Matrix Structure on Water Mobility in Glycerol−Agar−Water Gel Systems: A Nuclear Magnetic Resonance Approach

Nuclear magnetic resonance spectroscopy (NMR) has been widely used to determine water molecular mobility in food systems. This study aimed to examine the effects of matrix structure and solutes on the dynamics of water molecules in model mixed systems, glycerol-agar-water gels, using low- and high-resolution NMR. Simple models to explain water relaxation rates and self-diffusion coefficients in mixed systems were developed using the experimental values obtained for the individual binary systems (glycerol-water solutions and agar-water gels). The spin-lattice relaxation of mixed systems was influenced by interactions of both glycerol and agar with water, while the spin-spin relaxation of mixed systems was dominated by the interaction of agar with water. Water diffusion was influenced by not only molecular interactions between all components but also the gel matrix structure. These models are able to differentiate the effect of solutes from that of matrix structure on water molecular dynamics.

Antifreeze Proteins: Their Structure, Binding and Use

Publisher Summary Antifreeze proteins (AFP) have been discovered in various fish, insect, and plant species. A great variety of protein structures are observed to modify ice crystal growth. Due to the variety in structure and distribution of AFPs across species, phyla, and kingdoms, their evolution remains a topic of research interest. Current theory suggests that AFPs were generated via convergent evolutions. During adaptation, different AFP molecules were produced in different species, leading to a natural diversity in molecular structure. Because of their earliest discovery, the molecular structure of AFPs from fish is studied most extensively. The antifreeze properties are dependent on the presence of the glycosylation in the molecule and differ from each other in structure and source but share the same physical characteristics. The basic requirement for an antifreeze molecule is the display of thermal hysteresis, a gap between the equilibrium melting point and the freezing point of the solution. A main area of interest in AFP research is the antifreezes ability to bind to an ice surface. The method of binding is not yet fully understood and several models are proposed. The increase in crystallographic structures of AFPs has led to advancements in the binding theories and postulated mechanism of action of these molecules. There has been great interest over the recent years regarding the commercial application of AFPs and their use in biotechnology, medicine, and frozen foods.

Food supply chains: Recent growth in global activity

Where does our food come from? The answer is from farms and fisheries, but as consumers in our developed urbanised society we know the reality is from a retail outlet. In other words; we shop.

Heat-stable antifreeze protein from grass: Phytochemistry

We have discovered an antifreeze protein in an overwintering perennial ryegrass, Lolium perenne. The protein is stable at 100 °C and although it is a less effective antifreeze than proteins found in antarctic fish and insects, it is better at preventing ice recrystallization. This property enables grasses to tolerate ice formation in their tissues without being damaged, suggesting that the control of ice-crystal growth rather than the prevention of freezing may have evolved to be the critical factor in their survival at very low temperatures.