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FD SC 410 > Exam Two > Flashcards

Exam Two Flashcards

1
Q

What is the 3C principle?

A

The 3C principle is the key to be a life long learner. You need to be motivated by compassion, competent by taking responsibility for your own learning, and do this all with good character

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2
Q

What are some reasons why lipids are important in the food industry?

A

Lipids are important for shelf life (lipid oxidation), oleogustus (taste of fat), and meat grading (marbling)

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3
Q

Which is more soluble in water a triglyceride or a monoglyceride?

A

A tryglyceride is less soluble in water. They become increasingly more polar as the number of fatty acid chains decrease

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4
Q

What is an example of a compound lipid?

A

One example of a compound lipid is a wac. It is a fatty acid ester of a long chain of alcohol. One exaample is caranuba wax which comes from the Copernicus cerifera tree

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5
Q

What are three important steps in sample prep when conducting lipid analysis?

A

Pre-drying the sample is important because the removal of moisture results in better extractability - water acts as a barrier and dilutes the solvent. Reducing particle size is important because it also leads to better extraction - higher surface area leads to more solvent/sample interactions. Conducting acid hydrolysis is important because it removes proteins and releases the fat

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6
Q

What are some characteristics of an ideal solvent to use in lipid analysis?

A

Some characteristics of an ideal solvent for lipid analysis are it’s cheap, unreactive with other components in the food, same polarity, nontoxic, non corrosive, leaves the lipid unchanged, non flammable, permeates the food well, not hygroscopic, and easily removed from sample

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7
Q

Compare and contrast petroleum ether and ethyl ether.

A

Both are common solvents used in lipid extraction. Ethyl ether is used because it has a low boiling point and is a pure compound. It is expensive, explosive, partially hygroscopic, and flammable however. Petroleum ether is cheap, less hygroscopic, and less flammable so it is used more often

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8
Q

List some advantages and disadvantages of using each lipid analysis technique.

A

Soaking: sample sits in the solvent and the fat permeates through the screen - A: quick process, D: process weakens overtime with old solvent. Rinsing: sample is in a cellulose casing and a solvent is poured over it - A: solvent is always fresh, D: channeling can occur (solvent will always take the path of least resistance).

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9
Q

List some advantages and disadvantages of multiple solvent lipid extraction methods.

A

Goldfish: sample is in casing and is exposed to solvent vapor - vapor condenses and fat is released - A: sample is always exposed to fresh solvent, D: channeling can occur. Soxhlet: uses a combination of soaking and rinsing - A: most accurate method, D: cannot run multiple samples at one time - operator must always watch. Soxtec: combination of soaking and rinsing - A: more than one sample can be run at once, D: soaking and rinsing doesn’t occur at the same time. Mojonnier: gravimetric technique used for heterogeneous samples - A: do not need to dry sample, D: discontinuous - constantly requires set up

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10
Q

Compare and contrast the Babcock method and the Gerber method.

A

Both methods measure the amount of fat in dairy products. The principle is using sulfuric acid to digest the protein and release fat, centrifuge then the fat will separate due to the density difference. The Gerber method is different because it uses amyl alcohol, simpler, faster, and charring does not occur

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11
Q

List instrumental methods for measuring fat.

A

Infrared: measures the absorbance of infrared energy by the fat. NMR: measures the total lipid content or the amount of saturated/unsaturated fats. Specific gravity: measures the amount of fat by the product’s specific gravity

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12
Q

What is the smoke point?

A

The smoke point is the point at which a fat smokes

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13
Q

What is the flash point?

A

The flash point is the point at which a fat flashes

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14
Q

What is the fire point?

A

The fire point is the point at which a fat becomes inflamed due to lipid decomposition

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15
Q

How does the amount of free fatty acids affect the smoke point, flash point, and fire point?

A

Free fatty acids increase oxidation so it lowers the smoke point, flash point, and fire point

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16
Q

What is a cold test?

A

A cold test assess the winterization of oil (when it first begins to crystallize) to measure the amount of saturation

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17
Q

What is the cloud point?

A

The cloud point measures when the oil begins to nucleate after heating which measures the amount of saturation

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18
Q

What is the iodine value?

A

The iodine value measured the amount of unsaturation. It is a titration that changes from colored to colorless

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19
Q

What is the saponification value?

A

The saponification value indicates the average molecular weight of a triglyceride - it measures the amount of sample that will saponify - short chains increase the saponifiability

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20
Q

How is free fatty acid content calculated?

A

See equation on slide 30 of Lipid Analysis

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21
Q

Why is measuring free fatty acid content important?

A

The amount of free fatty acids is important because it affects the aroma, quality, and tests for possible adulteration of the product.

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22
Q

What are the three general steps of lipid oxidation?

A

The three general steps of lipid oxidation are initiation, propagation, and termination.

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23
Q

What is the peroxide value?

A

The peroxide values measures the amount of primary oxidation products are present in the product

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24
Q

What is the TBARS test?

A

The TBARS test measures the amount of secondary oxidation products present in a product.

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25
Q

Why is conducting protein analysis important?

A

Protein analysis is important for nutrition, pricing, functional properties, beneficial biological activity, and quality control.

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26
Q

Why can measuring protein content by the percentage of nitrogen in a product be slightly inaccurate?

A

When measuring the amount of protein by the amount of nitrogen the results can be slightly inaccurate because of the non-protein nitrogen sources in foods such as steroids, sterols, alkaloids, theobromine, caffeine, nitrosamines, nitrates, and nitrites.

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27
Q

What are some methods for protein analysis?

A

Some methods for protein analysis are the Kjeldahl, Dumas, Infrared, Biuret, Lowry, anionic dye binding, Bradford dye binding, Bicinchoninic acid (BCA), and ultraviolet.

28
Q

Describe the Kjeldahl method. List advantages and disadvantages.

A

The Kjeldahl measures the amount of nitrogen. Its four main steps are digestion, neutralization, distillation, and titration. A: applicable to any food, accepted standard method, and cheap. D: overestimates the amount of protein, time consuming, dangerous, isn’t as accurate without the Kjeldahl factor

29
Q

What is the general Kjeldahl factor?

A

The general Kjeldahl factor is 16% Nitrogen or 6.25 grams of nitrogen per gram of protein.

30
Q

Describe the Dumas method. List advantages and disadvantages.

A

The Dumas method is based on nitrogen combustion. The amount of nitrogen is measured with gas chromatography. A: automated, quick, user friendly, holds multiple samples at one time, and no sample prep. D: must be calibrated within the range that you’re looking for, requires the Kjeldahl factor, and can be dangerous.

31
Q

Describe the infrared spectroscopy method for determining protein content. List advantages and disadvantages.

A

Proteins have many unique properties. The infrared spectroscopy method takes advantage of the unique property of having peptide bonds. It measures the absorbance of radiation by peptide bonds. A: quick and accurate D: requires calibration and sample prep.

32
Q

Describe the Bradford dye binding method. List advantages and disadvantages.

A

The Bradford dye binding method takes advantage of the fact that proteins are charged. The dye is negatively charged so it binds to the positively charged proteins and change the maximum absorbance from 465 nm to 595 nm. The amount of protein directly correlates with absorbance. A: accepted, D: sample must be in liquid form, standard curve must be made, possible detergents and reagents can affect results, and it only measures protein within a certain range

33
Q

Why are histidine, arginine, and lysine important amino acids for the Bradford dye binding method?

A

Histidine, lysine, and arginine are important amino acids for the Bardford dye binding method because they are all basic and polar which leads to the strongest binding between the amino acid and dye molecules.

34
Q

Describe the BCA method.

A

The BCA method is based on a protein’s peptide bonds. Cuprous ions react with BCA reagent to produce color and then it is spectrophotometrically measured.

35
Q

What is electrophoresis?

A

Electrophoresis is the separation of molecules using an electric field

36
Q

Which direction do molecules move during electrophoresis?

A

Molecules move from the cathode (-) to the anode (+)

37
Q

Describe the components of the buffer used for electrophoresis.

A

The sample buffer used in SDS PAGE consists of water, tris-HCl, glycerol, SDS, mercaptoethanol, and bromophenol blue. Each reagent in the sample buffer plays an important function. If any were left out the SDS PAGE would not be conducted correctly. The water is used for proper dilution and distillation. Since water is the bulk of the buffer, without it the components and the proteins would not be able to travel throughout the gel. The HCl lowers the pH of the gel; this allows a voltage gradient to form between the chloride ions and the glycine ions. Without HCl, the proteins would not be able to move through the gel. The glycerol is denser than water so it is used to weigh down the sample so it will not mix with the buffer. If the glycerol was removed the sample would also not be able to stay in the well. SDS is an anionic detergent used to make all of the proteins negatively charged through binding. Without SDS, migration would differentiate by charge as well. SDS damages the secondary structure. Mercaptoethanol changes the shape of the proteins so they’re all uniform; it breaks the covalent disulfide linkages and damages the tertiary structure. If the mercaptoethanol was removed migration would differentiate by shape. Without both the mercaptoethanol and the SDS, it would basically be native PAGE. The last component is bromophenol blue dye. It moves quicker than proteins through the gel so it can be used to monitor the process’ progress and the sample is visible in the gel. Without the bromophenol blue, you would not be able to see the proteins.

38
Q

How is the velocity of a protein traveling through an electric field calculated?

A

Velocity is calculated by multiplying the field strength by the molecular charge and divide by the friction factor

39
Q

What is PAGE?

A

PAGE is polyacrylamide gel electrophoresis. It separates the proteins by size

40
Q

What is the relationship between acrylamide concentration and pore size?

A

A higher concentration of acrylamide leads to smaller pores - more friction

41
Q

What is native PAGE?

A

Native PAGE is when the proteins’ size, charge, and shape are all different

42
Q

How can PAGE be used to determine molecular weight?

A

If you have a standard with a known molecular weight and known amount of bands then you can use the negative linear relationship between relatively mobility and log molecular weight to your advantage

43
Q

What is isoelectric focusing?

A

Isoelectric focusing is based only on the isoelectric point of the protein - not shape, size, and charge

44
Q

What is Kwashiorkor syndrome?

A

Kwashiorkor syndrome is a protein deficiency - frail appendages and distended belly

45
Q

What are ampholytes? What are they useful for?

A

Ampholytes are weak acids and bases that are bound to the gel during isoelectric focusing - they form a pH gradient from the top to the bottom of the gel

46
Q

In isoelectric focusing, which direction do the proteins travel? Is it more acidic or basic at which region?

A

Proteins travel from cathode (-) to anode (+). The cathode is more basic so it has more acidic ampholytes and the anode is acidic so it has more basic ampholytes

47
Q

What is 2D electrophoresis?

A

2D electrophoresis uses a combination of isoelectric focusing and SDS to help identify proteins

48
Q

Describe the different dyes that can be used for electrophoresis,

A

Coomassie brilliant blue is an older technique and can only bind to abundant proteins. Amido black can bind to low abundance proteins. Silver stain is 100x more senstive than coomassie and is used for low abundance. Western blot is used to find a specific protein

49
Q

What are the food science applications for electrophoresis?

A

Electrophoresis can be used to assess protein purity, check for adulterants and contaminants, develop a process foot print, and allow purification

50
Q

What is the difference between electrophoresis used for DNA and electrophoresis used for proteins?

A

DNA electrophoresis uses agar gels while protein electrophoresis uses polyacrylamide gels

51
Q

What is spectroscopy?

A

Spectroscopy uses the interaction between light and matter to gain information about a sample

52
Q

How many times is the sun bigger than the earth?

A

The sun is 109x bigger than the earth

53
Q

How is energy calculated?

A

Energy is calculated by multiplying planck’s constant by the frequency

54
Q

What is the relationship between frequency and wavelength?

A

Frequency has an inverse relationship with wavelength

55
Q

What types of energy do molecules have?

A

Molecules have rotational and vibrational energy

56
Q

What is emission spectroscopy?

A

Emission spectroscopy is when light energy is emitted

57
Q

What are the two carotenoids we get from food?

A

The two carotenoids we get from food are zeaxanthin and lutein

58
Q

What is absorbance spectroscopy?

A

Absorbance spectroscopy is measuring the absorbance of the sample to calculate the concentration

59
Q

What is Beer’s law?

A

Beer’s law calculates the relationship between concentration and absorbance. It is absorbance equals the molar extinction coefficient multiplied by the concentration of the solution and the path length of the cell

60
Q

Which is one amino acid that cannot fluoresce or absorb UV light?

A

Thiamin cannot fluoresce or absorb UV light

61
Q

What are some sample preparation steps when conduction spectroscopy?

A

The sample must be homogenized, in liquid form, possibly chemically modified, and a reference must be made

62
Q

What is an immunoassay?

A

An immunoassay is a very specific biochemical assay focused on detecting a certain macromolecule in a food product and or food contact surface

63
Q

What is an allergen?

A

An allergen is a protein that elicits an immune response

64
Q

What is an antigen?

A

An antigen is any molecule that can induce antibody formation “im vivo” within a living thing or an immune response

65
Q

What is an antibody?

A

An antibody is an immunoglobulin protein that is produced by activated B cells in response to an antigen

FD SC 410 (11 decks)

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