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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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