PRELIM PHYSSCIB

This process occurs when fluids molecules are attracted to the solid surface and begin to adhere to it.                                                                                                                                                              

• adsorption

• absorption

• adhesion

• cohesion

The important components of all food materials do water play are:

• all of the choices

• chemical

• physical properties

• biochemical properties

This process occurs when the same molecules are already present on the solid surface and are escaping from the surface by being attracted to the fluid phase.                                                                     

• flidity

• absorption

• adsorption

• desorption

When is a food sample comes into equilibrium with the atmosphere surrounding it?                    

• boundary surface at the interface between solid food material and fluid atmosphere (liquid or gas).          

• when the water activity in the food sample becomes equal to the relative humidity of the atmosphere surrounding it.

• when the food sample is placed in cool environment

• all of the choices

The physical characteristics of surface boundary are Roughness, Smoothness and ________.                                                                    

• softness

• porosity

• sharpness

• fluidics

The adsorption and desorption processes in food occur on the boundary surface at the interface between the solid food material and fluid atmosphere (liquid or gas). Such boundary condition in a mass transfer is known as ______.                                                 

• Food-Environment Boundary

• Water Equilibrium

• Relative Humidity

• Solid-Fluid Boundary Surfaces

What is Adsorption Equilibrium?     

• Water molecules within the solid food will be attracted to the surface, and freely escape into the gaseous phase once they reach the surface.                     

• A state in which molecules are leaving the surface in a desorption process, while other molecules are attaching themselves to the surface in an adsorption process.

• This results in a net decrease in volume of the solid-water aggregate.

When does molecular adsorption occur?   

• When the distance between the water molecule and the cell wall becomes small enough, the force of attraction is large enough to draw the water molecules into the cell wall.    

• During the adsorption, gaseous molecules will be attracted to the solid surface and begin diffusion to the interior surface once the surface becomes saturated with the gas molecules. 

• Due to electronic and Van Der Waals’ attraction, but mostly due to hydrogen bonding in the case of water in the food.

• all of the cases

What are nonporous surfaces?              

• State in which molecules are leaving the surface in a desorption process.         

• Microscopically flat and smooth down to the molecular level.                                          

• Occurs when water molecules adhere in the cell walls of food material.

• a surface in which outside molecules cant penetrate to the body

It plays a decisive role in dictating the physical properties, quality and microbial, chemical and biochemical degradation of the food material.

• carbon

• water

• oxygen

• carbohydrates