Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

5) FDSC 300 > Lecture 3- Sample Preparation > Flashcards

Lecture 3- Sample Preparation Flashcards

1
Q

What is the flow od food analysis?

A

Sampling–> preprocessing–> processing–> testing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why do we sample pre-treatement and sample processing?

A

Reducing sample size
Homogeous
Preventing changes in samples
Avoiding matrix interference during analysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is coning and quatering?

A

Gather the material into a cone –> flatten –> divide in half–> divide in quarters –> pick a quarter–> Repeat until you have a Sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

How do you reduce sample a sample?

A

Depend on physical size: blenders for solid and coning and quartering for powdered sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Which smaples are usually heterogenous?

A

Samples obtained

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What causes heterogeneneity?

A

Variations in the properties of differnet units within the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How can you homogenize?

A

Grinders, mixers, blenders

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do you choose the device to homogenize?

A

Depends on the composition of the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What do you use to homogenize a high fat high moisture food?

A

knife blades

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What do you use to homogenize low fat low

A

grinder or mills

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the reasons that we sould lose a sample?

A
  1. Losses as dust or particulates
  2. Losses through volatilization
  3. Losses due to adsorption
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

How do you stop the loss of a sample due to vessel?

A

Make sure the vesel is clean

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why would you lose a sample to dust/particles

A

Ashing –> dust get elsewhere
Ariflow –> due to changes in temp
Breathing –> dust goes places

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

How to reduce loss to dust

A

Never open the door of a hot furnace
Use plug of glass or quartz wool to collect particulates with combustion
Ash/ finely ground –> cover
Add reagaents slowly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

How to do you lose sample to volatilization?

A

During heating
Decreases in water during grinding solid during local heating
Elements may be volatile

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Whatis blanching

A

Exposing a food to high heat via boiling water or steam fora short time

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How do you migitate loss through volatilation

A

Use properly sealing vessel for wet ashing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Why would we have loss of sample due to adsorption?

A

Absorption of molecule to plastic or glass containers

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Poly phenyloxidase

A

Add acid, stop oxidation (browning) or fruits

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

How do you migitate loss to absorption

A

Use pretreated glassware with a hydrated layer

Soak new glassware overnight with dilute nitric or hydrochoric acid

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are some changes that can occur in samples over time?

A 
Enzymatic inactivation
Lipid oxidation
Microbila growth
Physical change
Contamination
22
Q

What happens during enzymatic degradation?

A

Enzyme may degrade the food components being analyzed

23
Q

How do you migitate enzymatic degradation?

A

Heat denaturation
Sotrage in freezer
pH
Adding reducing agents to prevent oxidative enzymes

24
Q

How do you wet ash?

A

Acid and boiling

25
Q

lipid oxidation

A

Unstaruated lipids are sensitive to oxidative degradation

Exposure t light can accelerate lipid peroxidation

26
Q

How do you migitate lpid oxidation?

A

Storing under nitrogen or vacuum

Use anti-oxidant

27
Q

What changes do microbial growth cause?

A

Microbial contamination
Degrade food components
Introduce foreign components

28
Q

How do you mitigate microbial growth?

A

Addition of preservative
Low Temperature storage
Freeze drying
Storage under modified atmosphere

29
Q

What happens with physical change?

A

Drying
Fluctuating storage temperature
Fluctuatin gas pressure

30
Q

How do you mitigate physical changes?

A

Storage in air tight humidity controlled containers

Maintain temperature

31
Q

What are some sources of contamination?

A 
Airborne
Reagent
Glassware
Facilities
Cross-contamination
32
Q

Why is is important to reduce matrix interference?

A

Matrix components interfere with assay –> pigments interfering with colorimetric assay for reducing sugars

33
Q

Examples of getting rid of the matrix

A

dry ashing, wet ashing,

34
Q

How can sample preparation be performed?

A
  1. Extractoin of target analytes

2. Removal of itnerfering substances

35
Q

What are the methods of extraction of analytes?

A

Digestion
Solvent extraction
Sorbent extraction
Membrane Extraction

36
Q

Contamination from ICP-MS

A

Wash equipment with acid to wash away contaminants

37
Q

What is digestion?

A

Microwve, UV photolysis

38
Q

What is solvent extraction?

A

Pressurized liquid extraction
Supercritical fluid extraction -> lq, CO2
Microwave assisted extraction
Solvent Assisted Flavour evaporation-> minor components
Liquid phase microextraction

39
Q

What is sorbent extraction?

A 
Solid phase extraction
Dispersive solid phase extraction
Matrix solid phase dispersion
Solid phase microextraction
Solidphase dynamic extraction
Stir Bar Sorptive Extraction
Headspace Sorptive extraction
Solid Phase aroma concentration extraction
40
Q

What is membrane extraction?

A

Dialysis

Membrane extraction witha sorbent interface

41
Q

What is a standard curve?

A

Independent -> X

Dependent -> Y

42
Q

What is the point of making a standard curve?

A

To find the relationship between a independent and dependent variable through their slope

43
Q

What is the lineary regression of a standard curve?

A

y=ax+b

44
Q

What are confidence bands?

A

Define statistical uncertaincty of the regression line

45
Q

What is the corrleation coefficient?

A

Defines how well the data fits toa straight line

46
Q

What is outliner data?

A

Data point that is far outside the norm for a variable or population

  • increase error variance
  • reduce the power of a statistical test
  • decrease normality
47
Q

What is the upper limit equation?

A

X+1.96*σ/√ n

48
Q

What is σ?

A

The std. dev of the population

49
Q

How do you determine outlier Data?

A 
Q test
Qvalue=
𝑋2−𝑋1/𝑊
X1= outliner value
X2= next closets value to X1
W total spread of all value obtained by substracting the lowest value from the highest value
50
Q

What does outlier data tell you?

A

Says that the experiemtn is not well done

Due to errors in data ( human error, etc)

51
Q

What are some other forms of error?

A

Sampling error
Intentional misrepressentation of sample
Instrument/assay condition failure
Legitimate cases

52
Q

Coefficient of Regression

A

Determine how accruate the line is

5) FDSC 300 (14 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions