Experimental Foods Exam 1

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Pure water freezes at

0 degrees Celsius

water changes structure from solid to a gas at?

540 Calories

how many calories are removed when water is changed to ice?

80

in colloidal dispersions, the __________________ phase extends throughout the system, surrounding all parts of the other phase

continuous phase

which is true about water activity?

converting free water to bound water decreases the Aw value

a supersaturated solution is?

important in the product of candies

colligative properties depend on the ___________ of solute particles in a given amount of solvent and not the nature of the solute

number

colligative properties depend on the _________ of solute particles in a given amount of solvent and ____________ of the solute

number; not the nature

which represent the physical properties and structures of water?

polar nature, hydrogen bonds

a sol is a kind of colloidal dispersion of

solid dispersed in liquid

what do colligative properties depend on?

the # of solute particles in a given amount of solvent

what is latent heat?

the amount of energy in calories per gram absorbed as a substance that undergoes a change in state

1 mole of a non-volatile ionizing solute will raise the boiling point of 1 liter of water by?

0.52 degrees C

what Aw range represents yeast and mold spoilage?

0.75-0.9

all foods have a water activity less than?

1

what is the specific heat of water?

1 cal/g/C

which results in the highest freezing point when added to 1 L of water?

1 g of sugar

which result in the highest boiling point when added to 1 L of water?

1 gram of salt 1 gram of sugar plus 0.5 gram of salt

what size particles must a solution have to be to be considered coarse?

1000 nm

the boiling point of water is ______ and its freezing point is ________

212 F, 32 F

all colloidal systems have _______ phases, known as the ______________

2; continuous phase and discontinuous phase

boiling point drops 1 degree F for every _______ foot increase

500

what are examples of bound water?

NaCl vitamin carbs emulsifiers

the way the positive and negative charges on a water molecule are concentrated is called?

a dipole

adsorption is when?

a dry food is placed in a wet environment

there is a cup of water, and you need to dissolve a substance in the water, which of these things could be used to create a solution?

a polar molecule

which one of these substances is classified as a "food dispersion"?

a solution, a suspension, an emulsion, and a colloid

which of the following statements is false?

a true solution contains more solute than the solvent can dissolve is considered unsaturated

which of the following i an unsaturated solution?

a true solution that contains less solute than the solvent can dissolve at a given temperature

one mole of which of the following will raise the boiling point of 1 L of water the most?

calcium chloride

what food product is made using the process of a supersaturated solution?

candies/fudge

which of the following is/are a colloidal dispersion?

casein gelatin protein albumen

starch granules in cold water is an example of a?

coarse suspension

in a true solution, dissolved sugar will?

decrease the vapor pressure

adding salt to water will _________ the freezing point and ____________ the boiling point

decrease; increase

in a true solution the dissolved/ionized susbtances will _______________ the vapor pressure of a solution, which will require ________ heat for the vapor pressure to overcome atmospheric pressure to reach the boiling point

decrease; more

adding solutes that dissolve or ionize ______________ the vapor pressure of the solution

decreases

as the percentage of water in a food is "bound", the water activity?

decreases

how do volatile solutes affect the boiling point of water?

decreases boiling point

the addition of solutes to water does what to the freezing point?

decreases the amount of time to freeze

how can you control Aw?

dehydration concentration addition of humectants freezing

____________ is when a wet food is placed in a dry environment

desorption

what are the two phases of a colloidal system?

discontinuous and continuous

what are true characteristics of water molecule?

easy form H bonds and ionic interactions with other/food molecules have a high specif heat

salad dressing is what type of colloidal dispersion?

emulsion

to change the state of water you must add or remove high amount of ?

energy

boiling point is when the pressure of the steam is __________ that of the atmosphere

equal to

which of the following are a type of colloidal dispersion?

foam and gels

which of the following is not an example of a colloidal dispersion? whipped cream foam yogurt fog marshmallow salad dressing

fog

freezing can be damaging to food systems due to?

formation of ice crystals (especially large crystals) concentration of soluble solids concentration of gasses (ie: oxygen) intermittent thawing (poor temperature control)

in which form of water is water activity measured?

free water

water activity can be measured from?

free water

all of the following states of water are below 100 degrees C except?

gas

a suspensoid (colloidal dispersion) is a mixture of?

gas in a solid

custard is an example of ____________, which is a colloidal dispersion

gel

what are two non-ionizing properties?

glucose, water

all of the following are examples of emulsions except? milk ice cream butter mayo

gravy

an example of sol would be

gravy

which of the following is an example of a sol?

gravy

what is a sol?

gravy starch

Aw is a value directly correlated with _____________ and chemical reactions

growth of microorganisms

Aw is a value directly correlated with

growth of microorganisms and chemical reactions

water that contains calcium and magnesium sulfates is referred to as?

hard water

When is heat released in heat of fusion?

heat is released when a liquid is transformed into a solid

heat energy absorbed in the conversion of water into steam is known as?

heat of vaporization

what is true about the structure of water?

hydrogen atoms are joined to the oxygen atom by two bonds that form an angle of almost 105 degrees water is a dipole

what type of interaction is surface tension?

hydrogen bonding

which of the following is true about water activity?

increase in moisture increases water activity

water activity lower than 0.9?

inhibit bacterial growth

what is true about latent heat?

it does not cause a rise in temperature

water activity is important in food service because?

it helps to predict shelf life

which of the following is true about vapor pressure?

it increases with increasing temperature

water is an unique substance because it has a high specific heat. What does this mean?

it takes more energy to heat water into steam compared to other substances

which is NOT a type of colloidal dispersion?

jello

gel colloidal dispersion is a ________, dispersed in a __________

liquid; solid

any food substance added to water will ________________ water activity, so all foods have a water activity ___________

lower; less than 1.0

which one of the following is an example of suspensoid?

marshmallow

which of the following is not a reason why freezing can be damaging to food systems?

melting and re-freezing

which of the following food products can one expect to have the lowest water activity?

milk powder

an example of a colloid is?

milk protein egg white protein gelatin protein pectin polysaccharide

water acts as a dispersing medium or solvent for all of these except? solubility mixtures hydration emulsion gels

mixtures

the relationship of water activity with __________ controls the shelf life of foods?

moisture

what occurs in a solution that has both water and salt dissolved in the water?

more energy is required for boiling point to be reached

in a water molecule oxygen has a partially ___________ charge, while the 2 hydrogens have partially _______ charge

negative; positive

which of the following statements are true regarding colloidal dispersions?

never truly dissolve in a solvent

colligative properties depend on the ___________ of solute particles in a given amount of solvent

number

colligative properties depend on the _______________ of solute particles in a given amount of solvent and ________________ of the solute

number/ not the nature

which of these examples demonstrates the activity of free water?

oranges and watermelon

the __________ concentrates the electrons of the oxygen atom away from the hydrogen atoms on a water molecule?

orientation

food dispersions are classified by their?

particle size

water contains intramolecular ________ bonds

polar covalent

the behavior of water molecules is strongly influenced by its?

polarity

the hydrogen atoms in water provide a ____________ content

positive

the 2 hydrogen atoms on water are partially ____________, while the one oxygen atom on water is partially __________________

positive; negative

addition of a substance to water will change the BP by?

raising the BP to 0.52 degrees C

in a true solution dissolved or ironized substances will _______ the vapor pressure of a solution, which means need ___________ heat for the vapor pressure to overcome atmospheric pressure and boil

reduce; more

which of the following foods do not contain a large amount of water?

rice

addition of these types of solutes will lower the freezing point by disrupting structure

salt and sugar

water activity and its relationship with moisture content help to predict?

shelf life

which one is the solid dispersed in a liquid?

sol

which colloidal dispersion is a solid dispersed in a liquid?

sol colloidal dispersion

what are examples of colloidal dispersions?

sol, gel, foam, suspensoid, emulsion

which of the following are types of colloidal dispersions?

sol, suspensoid, emulsion, gel

what is the colloidal dispersion of sol?

solid dispersed in a liquid

latent heat of fusion is temperature that remains constant as

solid turns to liquid

colloidal systems may be any combination of ______, -____, or __________ as longg as the particle size of one phase is within the dimensions of a colloidal

solid, liquid, gas

in a sol, the ___________ is the dispersed phase while the ___________ is the continuous phase

solid; liquid

which one is not the aspect for water acting as a dispersion medium or solvent?

sols

colligative properties depend on the number of __________ particles in a given amount of _____________ and not the nature of the ___________

solute; solvent; solute

________________ are homogeneous mixtures in which ____________ particles are small enough to dissolve within the _______________

solutions; solute; solvent

the plot of data for the resorption or desorption of water is called a

sorption isotherm

the difference between latent heat and specific heat is?

specific heat is the amount of heat needed to raise the temp. of water and latent heat is the amount of energy absorbed when water changes states

which of the following is not a colloidal dispersion?

starch mixture

which of the following is not a colligative property of water? static pressure mass fluidity boiling point/freezing point osmotic pressure

static pressure mass fluidity

what is not an example of a colloidal dispersion in a discontinuous phase?

sugar

what is an example of a true solution?

sugar dissolved in water

which is not a colligative property of water?

surface tension

marshmallow belongs to which colloidal dispersion type?

suspensoid colloidal dispersion

what is latent heat of fusion?

temperature remains constant as solid turns to liquid

triple point is the __________ and ____________ of the three phases are at equilibrium

temperature; pressure

what is the moisture sorption isotherm?

the relationship between moisture content and water activity at constant pressure and temperature it provides a record of water activity of a particular food it is an S-shaped curve when plotted on a graph

which of the following statements is completely true about dispersions?

the solvent in saturated solutions can dissolve increasing proportions of the solute as the temp. rises, which is known as a supersaturated solution

what is the triple point?

the temperature and pressure at which three phase (liquid, ice, and vapor) coexist at equilibrium

which is true of water activity?

the value is directly correlated to the growth of microorganisms and chemical reactions it is the amount of "free" water available the value decreases as the percentage of water in a food is "bound" changing from its "free" state all foods have a water activity less than 1

water activity is equal to the VP of a food divided by?

the vapor pressure of pure water

true solutions is the most stable because?

they are the smallest in particle size

what is the most stable type of dispersion?

true solution

which of the following dispersions has the smallest particle size and be characterized as the most stable of the three types of dispersions?

true solution

which type of dispersion contains the smallest particle size?

true solution

food dispersions are substances that are combined in several different ways. Combination of solvent and a solute can result in?

true solution and colloidal dispersion

what are the different types of dispersions?

true solution, colloidal dispersions, and course suspensions

which is the most stable of the three types of dispersions?

true solutions

which type of dispersion(s) is/are characterized as the most stable?

true solutions

which type of food dispersion is the most stable?

true solutions

combining a solvent and a solute results in either

true solutions colloidal dispersions coarse suspensions

dispersions are a combination between a solvent and a solute that can vary according to particle size. rank the types of dispersions according to particle size from smallest to largest

true solutions, colloidal dispersions, coarse suspensions

one gram of molecular weight of salt will have _______ as great as effect on the boiling point of a salt solution as will a gram of molecular weight of sugar

twice

___________________ influences the temperature at which boiling of a liquid occurs

vapor pressure

what are colligative properties to consider?

vapor pressure freezing point boiling point osmotic pressure

which are colligative properties of water?

vapor pressure (depression) boiling point (elevation) freezing point (depression) osmotic pressure (elevation)

what is an example of a colligative property?

vapor pressure and boiling point

what happens when a solute is added to solvent to form a solution?

vapor pressure decreases boiling point increases melting point decreases freezing point decreases

water activity of foods is measured by?

vapor pressure of food

these are all examples of colloidal dispersions except? proteins pectin starches gums vitamins

vitamins

which of the following is NOT a characteristic of water activity?

water activity represents the amount of water bound to salts, vitamins, carbohydrates and other solids in a food

which of the following is not true about water?

water is not a good solvent

freezing can be damaging to food systems for all of the following except? formation of ice crystals concentrations of soluble solids alters product macro nutrient content concentration of gases intermittent thawing

alters product macronutrient content

which of the following statements about colloidal dispersions is true?

an example of a colloid is a pectin

hydrogen bonds...

are relatively weak and they result in innumerable clusters of water molecules

what is not a part of colligative properties?

atmosphere pressure

boiling point is the temperature at which vapor pressure just exceeds

atmospheric pressure

the freezing point is not affected by?

atmospheric pressure

why is sodium chloride sprinkled on icy roads during the winter?

because the addition of sodium chloride lowers the freezing point of water making it more difficult for it to freeze

there is an inverse relationship between?

boiling point temperature and vapor pressure

how can water in foods stop being controlled?

by removing humectants


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