NFS386H1 Lecture Notes - Lecture 2: Ice Crystals, Crystal Growth, Freezer Burn
28 Nov 2013
School
Department
Course
Professor
Document Summary
As a constituent of food (part of other foods) Differences in structures implications for food quality (freezing affects quality attributes) Availability of water in a food system (for chemical reactions) implications for food quality (e. g. raising keeps for long time; water not available for reactions) Amount of water available for chemical reactions (e. g. microbial growth) Ice has an ordered hexagonal structure: crystal lattice structure. The structure of liquid water is described by the mixture model: water retains some hexagonal structure but is more disordered. Density of water > density of ice: nucleation, initiation of ice crystal formation, crystal growth, increase in the size of the ice crystal. The size of ice crystals depends on the rate of cooling. As the rate of cooling increases: number of nuclei increases, decreased size of crystals because of more nuclei. Large crystals solute moved to regions outside crystal, more concentrated in. Freeze concentration: as water freezes, solutes are concentrated in unfrozen zones. certain regions.
