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Lecture 5

FDSN 507 Midterm 1

Give three reasons why determining moisture content is needed. Affects food stability, if reduced lowers cost of transport, required for nutrition label calculations, comparison to other products.
Name three techniques which can be used for oven drying. Forced draft oven, vacuum oven, microwave analyzer, rapid moisture analyzer
Describe oven drying. A sample is heated to evaporate off water and the weight loss equals moisture content.
What should be considered when using oven drying methods? Predrying need, pans and covers, prevention of crust formation, decomposition of food
The ____ ____ technique should be used for preventing surface crust formation. sand pan
T or F: A vacuum oven drys the food product under increased pressure. False
To achieve reduced decomposition, a ____ oven should be used. vacuum
What is the disadvantage to microwave drying? Can only test single samples
T or F: Moisture analyzers provide a rapid method of drying. True
Infrared drying involves _____ of heat rather than conduction or convection with conventional ovens. penetration
Name three sources of error in oven drying. Volatiles present, hygroscopic sample, surface crust formation, splattering
_____ methods are based on the direct measurement of the amount of water removed from a food sample by _____. Distillation, evaporation
Distillation set ups must combine a food sample and ____ with ____ boiling point. solvent, high
What are the parameters for a distillation solvent? insoluble with water, higher boiling point than water, less dense than water, safe to use
What considerations should be made with a distillation? Emulsions occurring, water droplets sticking to side of container, decomposition of sample
T or F: Distillation is suitable for foods with high moisture content. False
What moisture removal technique should be used with herbs or spices? Distillation
Describe chemical reaction methods. A chemical reagent is added to the food which reacts with water to change the properties of the system; correlated to moisture content
Name two chemical reaction methods. Karl-Fisher titration, gas production model
T or F: Chemical reaction methods are used for low moisture foods. True
T or F: Chemical reaction methods require heat. False
Karl-Fisher reagent must be titrated with a _____ to determine KFR water (moisture) equivalence. standard
What can be used to standardize with the Karl-Fisher method? Water, water-in-methanol, sodium tartrate dihydrate
The dielectric method is based on the electrical properties of _____. water
The dielectric method is suitable for samples no more than ____to ____ percent moisture. 30-35
What two methods can be used to measure specific gravity? Hydrometer, pycnometer
What technique can be used to determine the concentration of a compound of interest? Refractive index
Describe infrared analysis. Absorption radiation at wavelength characteristic of OH stretch of water
Concentration of water is determined by ____ transmitted, inversely proportional to that that is absorbed. energy
Freezing point is a constant physical property of ____. milk
What method is used to measure freezing point? cyroscope
Define ash. Inorganic residue remaining after either ignition or complete oxidation of organic matter.
T or F: Ash is used for nutrition labeling calculations. True
How are samples prepared for ashing? Moisture removal
____ is often used a preparation technique for mineral analysis. Ashing
Dry ashing refers to the use of a ____ ____. muffle furnace
Name two advantages of dry ashing. Requires little time, can analyze many samples at once, no blanks needed
Name two disadvantages of dry ashing. Minerals hard to resolublize, mineral become volatile, takes a long time to get results
Describe wet ashing. Oxidizing organic substances with acids or oxidizing agents leaving inorganic matter.
T or F: Wet ashing is not used for ash. True
Name three advantages of wet ashing. Minerals stay in solution, little volatiles, short time
Name a disadvantage of wet ashing. Can only handle a small number of samples
Name an advantage to microwave ashing. Short time
Name two disadvantages to microwave ashing. High cost, only can handle a limited number of samples
Created by: goberoi



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