Food Engineering Flashcards
Give two foods that are pasteurized using high pressure.
Guacamole; deli meats
What are QUATs & what is their purpose?
Quaternary ammonium compounds; used as sanitizers
What is Biot’s Number and what are it’s units?
Ratio of heat transfer resistance inside of and at the surface of a body; dimensionless
In expressing units for vacuum in the English system, how many inches of mercury is the atmospheric pressure?
0
During the manufacture of ice cream, you discover that 1 liter of mix makes 2.0 liters of frozen ice cream. What’s your overrun percentage?
100%
What pH value is used to determine when a food is acid or low acid?
4.6
What is pH cutoff for high acid and low acid foods?
4.6
A retort temperature of 250 F is achieved with how many pounds of pressure per square inch?
15
What is the cutoff Reynold’s number for laminar flow in pipes?
2100
What are two factors critical for potato chis color and texture?
Free reducing sugars; Specific gravity (for absorption of oil, moisture loss during frying)
The ratio of two extensive properties of a homogeneous system is (a) an extensive property, (b) an intensive property, (c) a dimensionless quantity, or (d) none of the above?
(b) an intensive property
What is the average density of globular proteins?
~1400 kg/m3 or 1.4 g/cm3
What is the Reynolds number in a laminar flow?
What is the freezing point for most natural foods?
0 to -2 C
What is the temperature of triple point for water?
0.01°C.
What are the units for humidity?
1 lb water/ 1 lb air
1 Candela per square meter is equal to what?
1 lux
In brines, salt is measured with a salometer; what is 1° Salometer equal to?
1% of saturated NaCl solution (OR 0.265% salt = 1 degree salometer)
When convection predominates, where is the coldest spot in a can?
1/3 into can? (It can vary)
High-pressure processing of foods is often conducted in what pressure range?
100-800 Mpa
What is the saturation pressure of water at 100 °C
101.325 kPa or 1 atm.
The z-value you have calculated for your process is 18 degrees F. What is the z-value in degrees Celsius.
10C
What is the mean surface area of a Delicious apple?
140.13 cm2
How many BTU’s must be taken from a pound of water to change it from a pound of liquid water at 32°F to a pound of solid ice at 32°F?
144 BTU’s
What is the mean surface area of a Bartlett pear?
145.42 cm2
What is the minimum time and temperature required for batch or vat pasteurized milk?
145F (63 C) and 30 minutes
What are LTLT (low temp/long time) conditions in milk pasteurization?
145F for 30 minutes
What is an Intermediate Moisture Food?
20 - 40% moisture, Shelf stable, No rehydration needed, Combination of Low aw and additives
Given the gauge pressure in a retort is 100 kPa, what is the absolute pressure?
201.3 kPa
A metal container that is 2.6875 inches wide by 4 inches tall is known as what size container in the canning industry?
211 x 400
A 307 X 512 can has what diameter in inches?
3 7/16 inches
A product with a drying ratio of 5 yields 1 kg of dry product for every _______kg of water removed.
4 kg—drying ratio is the amount of fresh material needed to produce 1 kg of dried product
What is the freezing point for “freeze flow” formulated foods?
-5 to -15 C
What does 50 grain vinegar mean?
5% by weight
What is the mean surface area of an egg?
70.5 cm2
Water increases in volume by what amount as it turns to ice?
9% increase in volume
What is a psychrometric chart?
A graphical representation of properties for air-vapor mixtures.
What is a typical rheological property of a shear-thickening fluid?
A higher apparent viscosity at a higher shear rate
What is a subcooled liquid?
A liquid at the saturation pressure and a temperature below the saturation temperature.
What is a Bingham liquid?
A liquid that behaves similar to a Newtonian fluid at a stress greater than yield stress.
What is a typical rheological property of a shear-thinning fluid?
A lower apparent viscosity at a higher shear rate
What is thermal conductivity?
A measure of a material’s ability to transfer thermal energy.
What is syneresis?
A physico chemical process where water is expelled out of a gel or gel-like structure
To transfer cottage cheese from a vat to a tank, what type of pump should be used?
A positive displacement pump, the lobe type
What is the triple point?
A state where the three phases (solid, liquid and vapor) may all be present in equilibrium.
What is saturated vapor?
A substance occurs as a vapor at the saturation temperature and pressure.
What is a saturated liquid?
A substance occurs in a liquid state at its saturation temperature and pressure
What is a closed system?
A system that has no mass exchange with the surroundings
How are absolute pressure and gauge pressure related?
Absolute pressure = gauge pressure + atmospheric pressure
What is tempering with respect to flour milling?
Addition of water to raise moisture of wheat directly before milling
In cheese production most of the flavor is released during…
Aging
What thermal processing feature is essential for processing of food in glass containers?
Air overpressure
In SI system, what is the unit of magnetic field strength?
Ampere per meter
In SI system, what is the unit of current density?
Ampere per square meter
What is the permeate in UF?
Any substance not retained by the filter
What is a “food additive”?
Any substance that becomes part of a food product either directly or indirectly during some phase of processing, storage, or packaging.
What is reverse osmosis?
Applying pressure to exceed osmotic pressure of the solution
Explain the relationship between freezing rate, ice crystal size, and quality of frozen food products.
As the freezing rate increases, the crystal size decreases, and the product quality increases
How is water activity related to ERH?
aw = ERH/100
What is “double acting” baking powder?
Baking powder + 2 different acids, one which reacts at room temp, and one reacts at high temp.
What equation is used to describe mechanical energy balance for pumping?
Bernoulli equation.
The polysaccharides in oats that provide viscosity and filtration problems in the brewing industry are called?
Beta-glucans
A mild heat treatment to inactivate enzymes is called?
Blanching
What is the standard instrument worldwide for measuring the gelatinization properties and enzyme activity of flour?
Brabender amylogrpah
How may the seam tightness of a can be judged visually?
By the degree of wrinkling of the cover hook
In cheese making, the “cheddar” process involves: a. adding lactic acid to milk, b. adding rennet, c. turning and piling the curds, d.chopping the curds and adding salt
c. turning and piling the curds
What is the “method champenoise”?
Carbonation of wine by secondary fermentation in the bottle
Of processed cheese, processed cheese food and processed cheese spread, which has the most and which has the least water?
Cheese (most) and spread (least)
What acid in milk is fermented by bacteria to provide a source of diacetyl and volatile flavor compounds in fermented dairy products?
Citric acid
What is CIP?
Clean in place
The repirating burst associated with the fruit ripening process is called:
Climacteric rise
What is CUT?
Come up time in canning
What term describes the processing of a product, intended for room temperature storage, with the goal of preventing the growth of spoilage and pathogenic bacteria (although spores may be present)?
Commercial sterility
Name the isoentropic phase of refrigeration.
Compressor phase (compression)
What is the term for the change from a gas to a liquid?
Condensation
What are the units for thermal conductivity?
Conductivity (k) = J/msK or W/mK
What is the primary mechanism by which heat transfer occurs in a canned liquid?
Convection
What are the units for the convective heat transfer coefficient?
Convection (h) = J/m2K or W/m2K
What is the major reason that copper should not be used in food processing equipment, especially in dairy plants?
Copper acts as a strong oxidizing agent and promotes (catalyzes) oxidative rancidity
In SI system, what is the unit of electric charge density?
Coulomb per cubic meter
In SI system, what is the unit of electric flux density?
Coulomb per square meter
Which of the following are not part of a can’s double seam? coverhook; body hook; overlap; coverslip
coverslip
A maximum or minimum value for which a biological, chemical or physical parameter must be controlled by a CCP is what?
Critical limit
What is the name of the law that states “the total pressure of a mixed gas phase is equal to the sum of the partial pressures of the individual components”?
Dalton’s Law
Of the following, which method of food preservation will probably result in the greatest loss of vitamin A? A. Canning B. Refrigeration C. Freezing, D. Dehydration
D. Dehydration
Name the stage in fat processing where unwanted odors and flavors are removed.
Deodorizing
What type of fluid becomes more viscous when more force is applied to it?
Dilatant (shear thickening)
What is the rheological term for time-independent shear thickening?
Dilatency
Dehydration by contact with a heated surface of a revolving drum is called what?
Drum or roller drying
Why does extruded material puff when it leaves the extruder?
Due to pressure drop when exposed to the atmospheric pressure
What is the capacity of a material for taking recoverable deformation known as?
Elasticity
The HLB value is a number from 1 to 18 used to describe the effectiveness of what types of compounds?
Emulsifying agents
What is the 1st law of thermodynamics?
Energy can neither be created or destroyed
What is “oven Spring” that occurs during break baking?
Expansion of gas cells because of heat (oven spring is the rapid rise in bread loaf volume when placed in oven)
Name 2 encapsulation techniques?
Extrusion and spray drying
What is Newton’s second law of motion?
F = ma (force = mass x acceleration)
What are F values calculated at 250° F (121C) with a z value of 18F (10C) called?
F0
With regards to wheat flour processing, what are course particles of endosperm called?
Farina
Which federal authority approves frequencies used in the microwave and radio frequency heating of foods?
Federal Communications Commission (FCC)
What is aseptic processing?
Food and container are sterilized separately and then filled in a sterile environment.
What is the name of dQ/dt = -KA dT/dx?
Fourier’s law
What is another method/process for orange juice other than evaporation?
Freeze concentration
What is the processing difference between fresh pack and salt stock (genuine) pickles?
Fresh pack pickles are only marinated, whereas salt stock pickles are fermented.
What are the SI units of poise?
G/cm or pascals
Name 2 methods of irradiating foods.
Gamma rays, electron beam, also x-rays
What is the primary mechanism by which microwaves heat foods?
Generation of intermolecular friction caused by polar molecules attempting to oscillate at the frequency of the electrical field reversal (915 to 2450 MHz)
The unit for dose rate in ionizing radiation preservation is the ________________?
Gray
In the equation E=hv, what letter designates the “Planck constant”
h
What the term used to describe the level of calcium and magnesium salts in water?
Hardness
What packaging material has the highest moisture barrier?
HDPE
What is the name given to the volume of gas between the surface of the food product and the package?
Headspace
Why is wheat tempered before milling?
Helps to remove bran and reduces energy required in milling
A container that is absolutely impermeable to gases and vapors throughout its entirety is called?
Hermetic
Milk jugs are most commonly made of what polymer?
High Density Polyethylene
What part of the pasteurization controls the time?
Holding tube
What piece of equipment is used to uniformly disperse lipids in bovine mammary secretions?
Homogenizer
The major traditional preservative in beer is?
Hops
What is case hardening?
In drying, outer cells can collapse and form a water impenetrable layer that makes the product difficult to rehydrate.
Why is it necessary to pressure cool large diameter (401 or more) cans after low acid thermal processing?
In order to prevent buckling.
Where do you find the “greasy bag syndrome”?
In potato chips
Cloud stability in products like tomato and orange juice is favored by:
Inactivation of PME
What is the purpose to form agglomerations of powdered foods?
Increase hydration ration
If the temperature increases, what happens to the rate of heat transfer?
Increases
Give an example of a product made using “agglomeration”
Instant coffee, instant milk
What is the difference between intensive and extensive properties?
Intensive properties do not depend on the mass of a system.
Water hardness can be reduced using a water softening system; what is the principle used to reduce water hardness in these systems?
Ion exchange
The radura symbol indicates that a food has been treated by or with what food processing system?
Irradiation