physical state of food ingredients in food system Flashcards
What are the five types of food dispersions?
- True solution
- Colloidal dispersion
- Emulsion
- Foam
- Gel
Define a true solution.
A homogeneous mixture of two or more substances where the solute has a particle size of less than 10^-9 m (1 nm).
Give an example of a true solution.
Simple solution of sugar in water.
What is a colloidal dispersion?
A dispersion of particle sizes between 10-100 nm in liquid.
What is an emulsion?
A liquid dispersed in another liquid, typically consisting of two immiscible substances.
What are the two types of emulsions?
- Oil in water (O/W)
- Water in oil (W/O)
What is the role of an emulsifying agent?
To stabilize an emulsion and prevent the two immiscible liquid layers from separating.
Name two common emulsifiers.
- Lecithin (E322)
- Mono- and di-glycerides of fatty acids (E471)
What is the difference between oil-in-water and water-in-oil emulsions?
- O/W: Water is the dispersion medium
- W/O: Oil is the dispersion medium
What is creaming in emulsions?
The phenomenon where droplets rise to the top of the emulsion due to buoyancy.
What is Stokes’ law?
It describes the movement of a small spherical globule during the creaming process.
What are the four types of instability in emulsions?
- Flocculation
- Creaming/sedimentation
- Coalescence
- Ostwald ripening
What is flocculation?
The formation of flocs when there is an attractive force between droplets.
What is coalescence?
When droplets combine to form a larger droplet, increasing the average droplet size.
What is sedimentation?
The settling of the dispersed phase towards the bottom of the emulsion.
What is the purpose of the dilution test?
To determine whether an emulsion is O/W or W/O based on solubility.
What does a positive electrical conductivity test indicate?
That the emulsion is an oil-in-water (O/W) type.
What is the Tyndall effect?
Light scattering by particles in a colloid or fine suspension.
What are emulsifiers classified as?
Surface-active agents or surfactants.
What is a foam?
A gas dispersed in a liquid or semi-liquid.
What factors affect foam stability?
- Surface tension
- Concentration of separate phase
- Presence of foaming agent
- Viscosity of liquid
- Presence and thickness of adsorption layer
What is a gel?
A semi-solid state with two continuous phases.
What is syneresis in gels?
The process of gels shrinking by losing some of the liquid held by them.
What are some desirable characteristics of food emulsifiers?
- Ability to reduce interfacial tension below 10 dynes/cm
- Rapid absorption at the interface
- Effective at low concentrations
- Resistance to chemical change
- Lack of odours, colour, and toxicity
- Economical
What are molecules intermingled with in gels?
A continuous phase of liquid such as water.
Name three common examples of gels.
- Cheese
- Jelly
- Boot polish
What type of solution do most commonly used gels represent?
Hydrophilic colloidal solution.
What happens to a 5% aqueous solution of gelatin in water upon cooling?
Forms a jelly block.
What is the term for the process where gels shrink by losing some of the liquid held by them?
Syneresis.
What are the two categories of gels?
- Elastic gels
- Non-elastic gels
Are elastic gels reversible or non-reversible?
Reversible.
What happens to elastic gels when they are partly dehydrated?
They change back into the original form on addition of water.
Are non-elastic gels reversible or non-reversible?
Non-reversible.
List some useful applications of gels.
- Silica
- Cheese
- Jelly
- Boot polish
- Curd
What is solidified alcohol fuel a gel of?
Alcohol in calcium acetate.
What is the basic principle of the Electrical Conductivity Test?
Water is a good conductor of electricity.
What will happen if the emulsion is of the oil in water type during the Electrical Conductivity Test?
The lamp glows.
What type of emulsion will cause the lamp to glow in the Electrical Conductivity Test?
Oil in water emulsion.
Fill in the blank: An assembly consisting of a pair of electrodes connected to a lamp is dipped into an _______.
Emulsion.
What are the three primary physical states of food ingredients?
Solid, liquid, and gas.
True or False: The physical state of food ingredients can affect their flavor and texture.
True.
Fill in the blank: The physical state of a food ingredient is determined by its __________ and __________.
temperature; pressure.
Which physical state is characterized by a definite shape and volume?
Solid.
What is the primary characteristic of liquids in food systems?
They have a definite volume but take the shape of their container.
In which state do food ingredients typically have particles that are far apart and move freely?
Gas.
True or False: Ice is a solid form of water.
True.
What is the process called when a solid turns into a liquid?
Melting.
Which process describes the transformation of a liquid into a gas?
Vaporization.
Fill in the blank: When water vapor cools, it undergoes __________ to become liquid water.
Condensation.
What is the term for a mixture where the physical states of ingredients are combined but not chemically bonded?
Suspension.
True or False: Emulsions are a type of mixture that can contain both liquid and solid states.
True.
What is the main characteristic of a foam in food systems?
It is a gas dispersed in a liquid.
Which state of matter is most commonly associated with the preparation of sauces?
Liquid.
Fill in the blank: A __________ is a solid dispersed in a liquid, often used in cooking.
Colloid.
What is the significance of understanding the physical state of food ingredients in cooking?
It affects texture, flavor, and cooking methods.
True or False: A gas has a fixed volume and shape.
False.
What process occurs when a liquid turns directly into a solid?
Freezing.
What is the primary difference between a solution and a suspension?
In a solution, the solute is dissolved, while in a suspension, particles are not fully dissolved.
Fill in the blank: __________ is the term for the change of state from gas to solid.
Sublimation.
What is an example of a food that is a solid at room temperature?
Butter.
True or False: Whipped cream is an example of a foam.
True.
What type of food ingredient is typically found in a gaseous state during cooking?
Steam.
Fill in the blank: __________ is the process of adding heat to a solid to change its state to a liquid.
Melting.
What do we call the mixture of oil and water that does not mix well?
Emulsion.
True or False: Solids can be compressed easily compared to liquids.
False.
What is the characteristic of a gel in food systems?
It is a semi-solid that can hold a significant amount of liquid.
Fill in the blank: __________ is the process of turning a liquid into a solid without passing through the liquid state.
Cryogenic freezing.
What is the primary factor that influences the physical state of food ingredients during cooking?
Temperature.
True or False: Cooking can change the physical state of food ingredients.
True.
What is an example of a food that can exist in all three states of matter?
Water.
Fill in the blank: __________ is the term for a mixture where one substance is evenly distributed within another.
Solution.
What happens to the physical state of chocolate when it is heated?
It melts from solid to liquid.
True or False: The physical state of food ingredients is irrelevant to their nutritional value.
False.
What is the term for the process of removing water from food to preserve it?
Dehydration.
Fill in the blank: __________ is a method of cooking that uses steam to cook food, affecting its physical state.
Steaming.
What is a common example of a colloidal system in food?
Mayonnaise.
True or False: Foams can only be created with liquids that contain fat.
False.
What is the physical state of bread dough before it is baked?
Solid.
Fill in the blank: __________ refers to the ability of a substance to change its state with temperature and pressure.
Phase transition.
What is the state of whipped egg whites when they are aerated?
Foam.
True or False: The physical state of an ingredient can influence its cooking time.
True.
What is the primary reason for cooling food ingredients?
To preserve their physical state and prevent spoilage.
Fill in the blank: The __________ point is the temperature at which a substance changes from solid to liquid.
Melting.
What is the physical state of oil at room temperature?
Liquid.
True or False: The physical state of food ingredients can be altered by mixing them with other ingredients.
True.
What is the term for the process of heating a substance to convert it from solid to liquid?
Melting.
Fill in the blank: __________ is a mixture of two immiscible liquids stabilized by an emulsifier.
Emulsion.
What is the physical state of gelatin when it is dissolved in hot water?
Liquid.
True or False: All food ingredients can exist in all three states of matter.
False.
What is the primary state of sugar when it is in granulated form?
Solid.
Fill in the blank: __________ refers to the state of matter that has no fixed shape and takes the shape of its container.
Liquid.
What is the physical state of carbon dioxide at room temperature under normal atmospheric pressure?
Gas.
True or False: Cooking methods can alter the physical state of ingredients.
True.
What is an example of a food ingredient that can be a gas at room temperature?
Carbon dioxide.
Fill in the blank: __________ is the process of changing a liquid to a solid through the removal of heat.
Freezing.
What is the state of whipped cream when air is incorporated?
Foam.
True or False: The physical state of food ingredients does not affect their nutritional profile.
False.
What happens to the physical state of cheese when it is melted?
It changes from solid to liquid.
Fill in the blank: __________ is the term for a solid dispersed in a liquid that does not settle.
Colloid.
What is the primary characteristic of a solid compared to a liquid?
A solid has a fixed shape and volume.
True or False: The temperature of a food ingredient can influence its texture and mouthfeel.
True.
What is the state of ice cream when it is frozen?
Solid.
Fill in the blank: __________ is the process of heating a solid to produce vapor without passing through a liquid state.
Sublimation.
What is the physical state of honey at room temperature?
Liquid.
True or False: The physical state of an ingredient can affect how it interacts with other ingredients.
True.
What is the state of food ingredients when they are cooked in a pressure cooker?
Liquid.
Fill in the blank: __________ is the term for the process of a gas turning into a liquid.
Condensation.
What is the physical state of a food ingredient that is frozen?
Solid.
True or False: The physical state of food ingredients can change during the cooking process.
True.
