MS- Ch 01

Slide 1: 

Food Processing Technology

Slide 2: 

Water Physical properties Density Viscosity Phase change Surface activity Rheology and texture

Slide 3: 

Density Mass/ volume of a compound at a specific T Solid- Bulk density- mass of solid/bulk volume Particle density/specific gravity SG: mass of liquid/mass of water Porosity: fraction of the volume that is taken by the air =Va/Vb = volume of air/volume of bulk sample

Slide 4: 

Viscosity Internal resistance to flow Viscous material: ketchup, cream, syrup, yoghurt Viscosity change in heating/cooling/concentration Newtonian and non-Newtonian fluids Emulsions, suspensions Concentrated solution of starches, pectins, gums, proteins,

Slide 5: 

Shear Force- Force that moves the liquid Shear rate- velocity gradient Unit: kg m-1 S-1 Unit: m2S-1 Absolute viscosity, μ Viscoelastic material: Viscous and elastic properties exhibited at the same time When a shear stress is removed the material never fully returns to its original shape and there is permanent deformation. Ex. Dough, cheese, gelled foods etc.

Slide 6: 

Surface activity Most foods- mixture of solid/liquid/gas; any two or three Phase boundary exists Dispersed phase- that containing small droplets/particles Continuous phase- in which particles are distributed Formation of droplets: due to surface tension and application of high energy to increase surface area

Slide 7: 

Colloidal Food System

Slide 8: 

Surface tension

Slide 9: 

Emulsions Surfactants: Chemicals that reduce the surface tension in the surface of liquid. Also known as emulsifying agent or detergents Using surfactants more and new surfaces can be formed more easily Naturally occurring surfactants in food: alcohols, phospholipids, proteins, etc. Ex. Using egg in cake batters Synthetics are more powerful

Slide 10: 

Surface active agents- polar at one end and non-polar at other end It reduces surface tension, also promote wetting Foams Two-phase systems which has gas bubbles dispersed in a liquid or a solid, separated from each other by a thin film Low surface tension Low vapor pressure

Slide 11: 

Phase Diagram and Triple Point of water

Slide 12: 

At its simplest, a phase can be just another term for solid, liquid or gas

Slide 13: 

Under the set of conditions at 1 in the diagram, the substance would be a solid because it falls into that area of the phase diagram. At 2, it would be a liquid; and at 3, it would be a vapor (a gas).

Slide 14: 

Moving from solid to liquid by changing the temperature

Slide 15: 

Moving from solid to liquid by changing the pressure

Slide 16: 

A particular temperature and pressure at which three different phases of one substance can coexist in equilibrium The temperature and pressure at which a substance can exist in equilibrium in the liquid, solid, and gaseous states. The triple point of pure water is at 0.01 degrees Celsius and 4.58 millimeters of mercury Triple Point

Slide 19: 

Hydrogen bonding

Slide 20: 

Ice, water, vapor

Slide 21: 

Hydrogen bonding (electric attraction) Ice Liquid

Slide 22: 

Moisture Content The amount of water present in the sample (moist) MC wet basis (MCwb) MC dry basis (MCdb)

Slide 23: 

Moisture Content and water activity 0.95- Pseudomonas, Bacillus, Clostridium perfringens and some yeasts inhibited 0.90- lower limit for bacterial growth 0.80- lower limit for most enzyme activity and growth of most fungi 0.20- maximum heat resistance of bacterial spores

Slide 25: 

Problem solution