FOOD 2400 Lecture Notes - Glycerol, Supersaturation, Hydrophile
8 Nov 2012
School
Department
Course
Professor
Document Summary
List some unique chemical and physical properties of water and ice. High specific heat, large difference in density b/w water and ice. High melting and boiling temperature, surface tension, capillary action, high heat of transition. Describe some interaction of water with other molecules. Water binding/hydration depends on substances hydrophilic nature, considering salt, composition, ph and temp. Water holding capacity - eg gels of pectin and starch - syneresis. Water activity is the relationship between water content and perishability. Not the same as water content - simply an indicator of how much water is available to reactions and microbial growth. Sorption isotherm is a plot of aw vs water content. Explain the 3 regions represented in a sorption isotherm. A) adsorption of a monomolecular (langmuir) layer - most strongly absorbed, not freezable- almost part of the solid. B) adsorption of additional layers of water - multilayer and bonded to itself.
