Protein And Fat Previous Tests Flashcards by Amirah El-Amin

Which of the following is false? Prior to fat analysis by solvent extraction such as the soxhlet or goldfish method, ________is a step likely used to prepare the sample for analysis:

a. Grinding the sample
b. Acid hydrolysis
c. Treatment with protease
d. Drying the sample
e. More than one of the above

C. Treatment with protease

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Compared to petroleum ether as a solvent for fat extraction, ethyl ether is

a. More expensive, more flammable, and more likely to form peroxides
b. Less expensive, less flammable, and less likely to form peroxides
c. More expensive, less flammable, and more likely to form peroxides
d. Less expensive, more flammable, and more likely to form peroxides
e. Less expensive, more flammable, and less likely to form peroxides

a. More expensive, more flammable, and more likely to form peroxides

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Compared to the soxhlet method for extraction, the goldfish method is

a. Semi continuous
b. Less prone to channeling
c. Faster
d. A continuous method
e. More than one of the above

e. More than one of the above ( Faster and continuous )

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The principal form of lipid in food is

a. Triglyceride
b. Trans fatty acids
c. Steroids
d. Fatty acid

a. Triglyceride

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Which of the following practical considerations must not be considered when drying?

a. Sample dimensions
b. High moisture samples
c. Volatilization of other food components
d. Whether or not to use petroleum ether or ethyl alcohol
e. Both a and b

d. Whether or not to use petroleum ether or ethyl alcohol

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Crude fat analysis in reality measures:

a. The total amount of fat and other non-polar constituents of food soluble in extraction solvent
b. Only fat present in food
c. All the polar compounds present in the food
d. The fatty acid composition of food
e. Only the triacylglycerols in food

a. The total amount of fat and other non-polar constituents of food soluble in extraction solvent

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Which solvent is commonly used to determine fat content in the food industry?

a. Ethyl alcohol
b. Hexane
c. Acetone
d. Benzene

b. Hexane

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Molecules that are made of one molecule of glycerol and three fatty acids are called:

a. Complex lipids
b. Fatty acid side chains
c. Trifattyacids
d. Triglycerides

d. Triglycerides

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Prior to fat analysis by solvent extraction such as the soxhlet or goldfish method _______ is a step commonly/likely used to prepare the sample for analysis

T or F : grinding the sample
T or F: acid hydrolysis
T or F: treatment with protease
T or F: drying the sample

True : grinding the sample
True: acid hydrolysis
False: treatment with protease
True: drying the sample

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Compared to ethyl ether as a solvent for fat extraction, petroleum ether is _______

T or F: less dangerous
T or F: less flammable
T or F: more likely to form peroxides

True: less dangerous
True: less flammable
False: more likely to form peroxides

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The difference between fats and oils is that fats are?

Fats are solid at room temperature and tend to be more saturated while oils are liquid at room temperature

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In which form are most lipids found?

a. Sterols
b. Phospholipids
c. Triglycerides
d. Monoglycerides

c. Triglycerides

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Which of the following is an example of fats?

a. Glyceryl trioleate
b. Vegetable ghee
c. Coconut oil
d. Groundnut oil

b. Vegetable ghee

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The importance of phospholipids as constituent of cell membrane is because they possess

a. Fatty acids
b. Both polar and nonpolar groups
c. Glycerol
d. Phosphoric acid

b. Both polar and nonpolar groups

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What is the main principle behind crude fat extraction?

a. Dissolving polar compounds in a non-polar solvent
b. Dissolving non-polar lipids in a non-polar solvent
c. Separating lipids based on their density
d. Precipitation of lipids with a chemical reagent

b. Dissolving non-polar lipids in a non-polar solvent

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Which of the following would be the most suitable type for a goldfish method fat extraction?

a. Fresh fruit
b. Dried plant tissue
c. Meat sample
d. Milk

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Which of the following is false about lipids?

a. They are either strongly hydrophobic or amphipathic
b. They are partially soluble in water
c. Extraction of lipids from tissues require organic solvents
d. They are insoluble in water

b. They are partially soluble in water

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What is the final step in a typical crude fat extraction procedure using a soxtec apparatus ?

a. Adding the sample to the thimble
b. Heating the solvent in the boiling flask
c. Condensing the solvent onto the sample
d. Evaporating the solvent to obtain the crude fat residue

d. Evaporating the solvent to obtain the crude fat residue

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Which solvent is most commonly used in a goldfish method fat extraction ?

a. Water
b. Ethanol
c. Hexane
d. Methanol

c. Hexane

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What is the primary limitation of crude fat extraction?

a. It can only extract a portion of the total fat
b. It is not suitable for liquid sample
c. It requires specialized equipment
d. It does not differentiate between different types of lipids

d. It does not differentiate between different types of lipids

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Why is the goldfish method considered a “continuous” extraction technique?

a. The solvent is constantly recycled through the sample
b. The sample is continuously stirred during extraction
c. The extraction process can be performed without interruption
d. The solvent is continuously added to the sample

a. The solvent is constantly recycled through the sample

Which statement best describes the relationship between the soxhlet and soxtec methods of fat analysis?

a. The soxtec method for fat analysis is different from the soxhlet method
b. The soxtec method is an automated version of the soxhlet method
c. The soxtec and soxhlet methods are in no way different from each other
d. The soxtec method is an approved method while the soxhlet method is not an approved method

b. The soxtec method is an automated version of the soxhlet method

A glycerol backbone with one or two fatty acids plus another group, possibly a phosphorus group, produces a:

a. Sterol
b. Trans fatty acid
c. Phosphoric acid group
d. Phospholipid

d. Phospholipid

James and Chris ordered sausage, egg, and cheese San who he’s with coffee for lunch. Which type of fat is commonly associated with these animal products?

a. Unsaturated
b. Essential fatty acids
c. Trans fat
d. Cholesterol

d. Cholesterol

What answer best defines lipids? a. Fats in our food b. Diverse class of molecules that are insoluble in water c. Long chains of carbon atoms bound to each other d. Saturated, Unsaturated, and Trans fats

b. Diverse class of molecules that are insoluble in water

What is the three-carbon “backbone” found in all triglycerides?

Glycerol

What are the functions of lipids in foods?

1) influence on texture 2) influence on flavor 3) influence on quality and functionality

A function of protein is to: a. Provide essential fatty acids b. Promote growth and repair of the body c. Participate in nervous system functioning d. Medium for temperature regulation

b. Promote growth and repair of the body

A bond between amino acids is called a(n): a. Acid bond b. Hydrogen bond c. Ionic bond d. Peptide bond

d. Peptide bond

Proteins are: a. Fatty acids b. Lipids c. Polypeptides d. Triglycerides

c. Polypeptides

In proximate analysis, what component contains nitrates? a. Carbs b. Fatty acids c. Minerals d. Proteins

d. Proteins

If we assume that the kjeldahl factor used to calculate crude protein from the total nitrogen content for soybean is 4.5. What percent nitrogen is present in soybean proteins? a. 16 b. 22 c. 28 d. 45

b. 22

In protein determination which of the following is not included in the digestion step a. Sulfuric acid b. Ammonia sulphate c. Anhydrous sodium sulfate d. Copper catalyst

b. Ammonia sulphate

The dumas method of protein analysis can be considered as a. Dry combustion method b. Low temperature method c. Wet chemistry method d. Insoluble nitrogen method

a. Dry combustion method

In the kjeldahl method concentrated sulfuric acid, copper sulfate, and potassium sulphate are used as a. Reducing agent, catalyst & boiling point enhancer b. Oxidizing agent, reducing agent & boiling point stabilizer c. Oxidizing agent, catalyst & boiling point enhancer d. None of the above

c. Oxidizing agent, catalyst & boiling point enhancer

Ammonia gas liberated during procedure can be titrated via a. Sulphuric acid in excess b. Boric acid in excess c. Hydrochloric acid in excess d. None of the above

Kjeldahl method, which acid is used in digestion step? a. Sulfuric acid b. Hydrochloric acid c. nitric acid d. None of this

a. Sulfuric acid

What is the purpose of using sulfuric acid in the kjeldahl method? a. To neutralize the sample b. To digest the sample and liberate nitrogen c. To act as a catalyst d. To act as an indicator

b. To digest the sample and liberate nitrogen

Which sentence is false about kjeldahl method? a. It is used to determination of nitrogen b. It is official method c. Sulfuric acid in digestion step d. It is also used to determination of moisture content

d. It is also used to determination of moisture content

What step is ammonium ions converted into ammonium gas? a. Digestion b. Distillation c. Titration d. Back titration

b. Distillation

What is the principle behind the kjeldahl method? a. The nitrogen in the sample is converted to ammonia which is then titrated b. The nitrogen in the sample is converted to nitrate which is then titrated c. The nitrogen in the sample is converted to nitrite which is then titrated d. The nitrogen in the sample is converted to ammonium sulfate which is then titrated

a. The nitrogen in the sample is converted to ammonia which is then titrated

What is the relationship between nitrogen content and protein content in the kjeldahl method? a. Nitrogen content is directly proportional to protein content b. Nitrogen content is inversely proportional to protein content c. Nitrogen content is not related to protein content d. Nitrogen content is proportional to the square of protein content

a. Nitrogen content is directly proportional to protein content

Which of the following is false? An advantage of the dumas method over the kjeldahl method is that the dumas method a. Is much faster b. Requires no hazardous chemicals c. Is easily automated to analyze many samples without technician attention d. Measures just protein nitrogen e. None of the above

d. Measures just protein nitrogen

You need to determine the protein content of samples for nutrition labeling. Which of the following would be acceptable for such an application? a. Kjeldahl method b. Near infrared c. Bicinchoinic acid method d. Dumas method e. More than one of the above

e. More than one of the above

The protein assay currently most commonly used for nutrition labeling is a. Kjeldahl b. An ionic dye binding c. Dumas d. Infrared method e absorbable at 280 nm

c. Dumas

Which of the following is a key step in the kjeldahl method? a. Oxidation of the sample with strong acid b. Reduction of the sample with strong base c. Distillation of the sample with strong acid d. Titration of the sample with strong base

a. Oxidation of the sample with strong acid

Which of the following is false? When using the kjeldahl or Dumas methods, the conversion factor between the measured nitrogen content and the calculated protein content ______ a. Is based on the fact that the average molecular weight of nitrogen relative to the MW of an amino acid is 16% b. Is typically 6.25 because 100/16=6.25 c. Takes into account protein nitrogen vs non protein nitrogen d. Is different for different foods, because of differences in their amino acid profiles of the proteins present e. None of the above

c. Takes into account protein nitrogen vs non protein nitrogen

Classification of Lipids

- simple : yields only 2 products - compound : yields 3 or more products - derived : produced by the breakdown of simple and compound lipids through hydrolysis

Main functions of lipids

- energy and maintain human health - texture of food - flavor of food

Fat analysis is important for:

- shelf life - product quality and functionality - Manufacturing specifications - nutrition labeling