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70 Cards in this Set
- Front
- Back
What would be the effect onmoisture content determination if the particle size of the molecule is verylarge? Overestimate or underestimate? |
Underestimate of moisture. Large particles cant evaporate well because they are trapped inside of the food |
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What would be the effect onmoisture content determination if there is a high concentration of volatileflavor compounds present in the product? Overestimate or underestimate? |
Overestimate. Anything volatilemight be incorporated into the measure |
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What would be the effect onmoisture content determination if the sample undergoes sucrose hydrolysis? Overestimate or underestimate? |
Underestimate. Waterparticipating in reaction that hydrolyzes bond between glucose and sucrose.Some of the water is going to be reacting with the food (sucrose) and notevaporating (what you’re measuring) |
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What would be the effect onmoisture content determination if the samples were not placed in a dessicator after being removed from thedrying oven? Overestimate or underestimate? |
Overestimate. Presumably alreadydriven off all the water in drying oven, the humid air is going to replacewater back into sample. (Water going to move from high concentrationâ airâ tolowâ sample) |
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What moisture analysis method(s) is a method of choice to determinemoisture content on many low-moisture foods including dried fruits and vegetables, candies, chocolate, roasted coffee, oils and fats, & low-moisture food high in sugar/protein? |
Karl Fischer Titration |
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In what moisture analysis method(s) is I2 is reduced bySO2 in presenceof water and the endpoint of titration is reached when excess I2 present thatcannot react with water? |
Karl Fischer Titration |
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What is used tocalculate % moisture in the Karl Fischer Titration method? |
Volume of titrant |
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What are the 4 Oven Drying Methods? |
Forceddraft oven, Vacuumoven, Microwaveanalyzer, Rapidmoisture analyzer |
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In what moisture analysis method(s) is the sampleis heated to evaporate off water? |
Oven Drying Methods |
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What equals moisture content in oven drying methods? |
Weight loss |
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What is the calculation for % moisture with oven drying methods? |
((wet weight-dry weight)/(wet weight)) x 100 |
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What are 3 sources of error in Oven Drying Methods of moisture analysis? |
Particlesize, Volatilecompounds present, Lipidoxidation |
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In what moisture analysis method(s) is the sample is heated in toluene (an immiscible liquid), and the tolueneand water are co-distilled?
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Distillation (Refluxdistillation with toluene) |
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How is moisture found with the reflux distillation method? |
1. Collect mixture that distills off and 2. Measure volume of water removed |
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Why do the forced-air oven drying methods givedifferent results depending on temperature? |
Highertemperature would not only increase the amount of water driven off from thesample, but increase the likelihood of loss of non-moisture compounds. |
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What 2 moisture analysis methods are directmeasures of moisture loss, and will thus give more accurate results, especially for low moisture foods? |
Distillation method and Karl Fischer titration |
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What 2 moisture analysis methods are preferred for low-moisture foods? |
Distillation method and Karl Fischer titration |
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Regarding moisture content, experimentalerror will be inherently larger with ___ (distillation/oven) methods. |
Oven |
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What are 3 advantages of the reflux distillation method for moisture content? |
1. Good accuracy for low moisturefoods 2. Less thermal decomposition thanoven drying 3. Water is measured directly |
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What are 3 disadvantages of the reflux distillation method for moisture content? |
1. May be harder to measureaccurately the amount of water, 2. Emulsion formation, 3. Possible sample decomposition |
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What are 3 advantages of the Karl Fischer method for moisture content? |
1. Rapid (although one sample at atime), 2. Accurate (for low-moisture foods), 3. Uses no heat |
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What are 3 disadvantages of the Karl Fischer method for moisture content? |
1. Possibly incomplete moistureextraction, 2. Reaction of atmosphericmoisture/humidity, 3. Reaction of other food componentswith KF reactants |
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What are 3 physical methods of moisture analysis? |
1. Dielectricmethod, 2. Specificgravity (hydrometry), 3. Refractometry |
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What physical method of moisture analysis is basedon bending of light (i.e., refraction) as it hits surface of product? |
Refractometry |
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What is the equation for water activity (regarding vapor pressure)? |
(Vapor pressure above food sampleat defined temp)/ (Vaporpressure above pure water at defined temp) |
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What is ash? |
Inorganic residue remaining aftereither ignition or complete oxidation of organic matter |
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What ash analysis method principle is: Whensample is heated to high temperatures, all organic matter is incinerated,leaving inorganic material to be quantified gravimetrically |
Dry ashing, muffle furnace |
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What ash analysis method determines total ash content and is sometimes used as preparation for specific mineral analysis by Atomic Absorption Spectroscopy?
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Dry ashing, muffle furnace |
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What are 3 advantages to dry ashing? |
1. Requires little technician time, 2. Can analyze many samples at onetime, 3. Relatively safe |
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What are 3 disadvantages to dry ashing? |
1. Minerals can be hard to resolubilize, 2. Minerals can be volatilized, 3. Takes long time to get results |
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What are 3 sources of error in dry ashing? |
1. Samplenot representative, 2. Microelementcontamination, 3. Lossof sample in drying before ashing |
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What ash analysis method refers to oxidizing inorganicsubstances with acids and oxidizing agents, or their combination in liquid?
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Wet ashing
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When sample is heated to hightemperatures, all organic matter is incinerated, leaving inorganic material tobe quantified gravimetrically is the principle of ___ (wet/dry) ashing |
Dry |
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Organicmatter is vigorously oxidized using acids and oxidizing agents, leaving solubleinorganic matter is the principle of ___ (wet/dry) ashing
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Wet |
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Wet ashing typicallyuses a combination of ___ (acids/bases) and ___ (oxidizing/reducing) agents |
Acids, oxidizing |
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What are 3 advantages to wet ashing? |
1. Minerals stay in solution, 2. Little or no volatilization, 3. Short time |
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What are 3 disadvantages to wet ashing? |
1. Requires nearly constant operatorattention, 2. Handle small number of samples, 3. Can be extremely dangerous |
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Closed-vessel microwave digestionsystems and open-vessel microwave digestionsystems are ___ (wet/dry) digesters |
Wet |
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___ (Wet/Dry) digesters reachtemperature of 1200oC and use Quartzfiber crucibles |
Dry |
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What is the advantage to microwave ashing? |
Shorttime for ashing |
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What are 2 disadvantages to microwave ashing? |
1. High initial cost and maintenanceof equipment, 2. Limited number of samples can be ashed at one time |
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Whatmethod would be preferable for moisture analysis of ice cream? |
Karl Fischer (high sugar content) |
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What method would be preferable for moisture analysis of meat? |
Karl Fischer (high protein content) |
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What are 3 solvent extraction methods for lipid analysis? |
1. Pre-drying sample, 2. Particle size reduction, 3. Acid hydrolysis |
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With lipid analysis, ___ (ethyl ether/petroleum ether) is generally better solvent for fatand is more expensive |
Ethyl ether |
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With lipid analysis, ___ (ethyl ether/petroleum ether) is selective for more hydrophobiclipids and is cheaper
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Petroleum ether |
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What is the principle for solvent extraction methods of lipids? |
1. Fat is extracted withsolvent, 2. Fat content is measured by weightloss of sample or by weight of fat removed (i.e., gravimetric analysis); similar principle as used inoven drying methods for moisture analysis |
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The fat content on thenutritional facts label of foods is derived from what method? |
Gas chromotography |
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What is the equation for %protein from N content? |
%Nx 6.25 = % Protein |
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What is the main method of protein analysis? |
Kjeldahl method |
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What protein analysis method is recommended for foods used as sole source ofnourishment e.g., infant formula, foods for special dietaryconditions, and novel food products |
Amino acid analysis |
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What are 3 advantages to UV absorbance for protein analysis? |
1. Rapid, 2. Non-destructive, 3. Accurate |
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What are 3 disadvantages to UV absorbance for protein analysis? |
1. Accurate only for a pure protein, 2. Protein must be soluble, 3. Sample must be completelytransparent |
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What is the equation for determining total carbohydrate composition? |
100% - [% Moisture + % Ash + %Lipid + % Protein ] |
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What is a method for total carbohydrate analysis? |
Phenol-Sulfuric Acid Method |
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What is the principle for the Phenol-Sulfuric Acid method? |
Carbohydratesheated inthe presence of strongacid and high temp. first, undergohydrolysis to monosaccharides |
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What is the principle for Reducing Sugar Analysis? |
All based on reduction of Cu2+ions in alkaline solution to Cu+ ions by reducing sugars; Amountof Cu+ ions generated is then quantifiedto determineamount reducingsugars |
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What are 3 advantages to enzymatic methods for carb analysis? |
1. Usually specific for substancebeing measured, 2. Kits commercially available, 3. Generally have low detectionlimits |
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What are 3 disadvantages to enzymatic methods for carb analysis? |
1. May be interfering compoundspresent, 2. Not always 100% specific, 3. Not useful for measuring totalcarbohydrates, a class of carbohydrates, or all carbohydrates individually |
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What is the principle of the enzymatic method for starch analysis? |
Starch(gelatinized) is converted totally into D-glucose by enzymes specific forstarch*, and D-glucose is quantified enzymatically |
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What are 2 advantages to enzymatic methods for starch analysis? |
1. Commercial kits available, 2. Enzymes make the analysis veryspecific |
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What are 2 disadvantages to enzymatic methods for starch analysis? |
1. Amylases must be pure (no other enzymes present thatwould generate glucose or destroy peroxide) , 2. May not be quantitative forhigh-amylose starch or samples high in resistant starch |
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What is resistant starch? |
Starch that is: 1. Physically inaccessible toamylases; trapped in matrix, 2. Accessible but resistant tohydrolysis due to packing within the starch granule, 3. Retrograded starch; resistant todigestion |
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Resistantstarches behave like what? |
Fiber |
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What is the principle for the AOAC Method for Total DietaryFiber? |
1. Dried defatted sample is enzymatically digested with α-amylase, amyloglucosidase, and protease to remove starchand protein, 2. Soluble fiber is precipitated byadding ethanol, 3. Dried residue (i.e., soluble andinsoluble fiber) is corrected for ash and protein contents; Gravimetric analysis |
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Total dietary fiber is the sum of what 2 types of fiber? |
Soluble and insoluble fiber |
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What is 1 advantage to AOAC Method for Total DietaryFiber? |
Includes all fiber components,including resistant starch |
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What are 2 advantages to AOAC Method for Total Dietary Fiber? |
1. Very time consuming, 2. Overestimates fiber content infoods with high content of simple sugars, unless you first extract food with80% ethanol |
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T or F: Resistant starch may beclassified as dietary fiber |
True-- They are resistantto digestion |
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T or F: Like the simple sugars, solublefiber is soluble in 80% hot ethanol |
True |