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Flashcards in sampling & mycotoxins Deck (44)
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1

What needs to be considered when sampling?

1. need to be representative (consider size, homogeneity)
2. prevent contamination
3. prevent degradation
4. prevent mixing and losing data

2

Are toxicants present in the same levels in parts of a food?

No; foods are heterogenous.
diff compositions of parts will affect

3

What parts of a food should be sampled?

edible portions (usually remove peel, dirt, shell, etc)
specific guidelines by CODEX ALIMENTARUS

4

1 quantity of food delivered at once, of the same type/packing/description is known as a ____. It may be further divided into ____ designated for ____.

lot; sublot
sampling

5

What is an "incremental sample?" Is it used directly as a sample?

quantity taken from single place in designated lot/sublot

No; combine with other incremental samples to form AGGREGATE SAMPLE

6

The final product of the sampling procedure is a:

laboratory sample

7

A sample is considered to be representative if:

it reflects the properties of interest of the lot from which it was taken

8

An aggregate sample is derived from _____, and considered to be:

combining incremental samples taken from lot/sublot
representative of that lot/sublot

9

What are the two methods of sampling?

systematic: take 1 increment per sublot (time or mass)
random: all parts of the entire lot have equal chance of being sampled

10

____ and ____ will determine the sampling method, and the ______

size of bulk food sample, heterogeneity
sample size

11

the (more/less) heterogenous the bulk food, the (higher/lower) the variability, and so the greater the sample size needed

more; higher

12

What are the sources of uncertainty? (3)

1. external operations (packing, shipping, storage of sample)
2. prep of lab sample (sub-sampling, prep and processing)
3. analysis (extraction, cleanup, derivativisation, evap, instrument)

13

How do we determine total uncertainty?

total uncertainty (Sres) is square root of sum of squares for each uncertainty source

14

the 3 necessary precautions during sampling:

1. sample traceability
2. avoid contamination
3. appropriate storage/transport

15

What is sample traceability and why is it important?

- properly identify sample with correct labelling
- contain info for records (tracking forms, origin, date of sample, source, etc)

- needed to LINK sample & results to the food/batch it came from
- prevent data/sample loss
- important info on label: what is to be analyzed, history of handling, etc

16

the 3 main sources of sample contamination:

1. from sampling container/equipment
2. from another sample (transferred)
3. exposure to environment (air, dust, etc)

17

How do you determine if a container is suitable?

1. INERT to matrix & analyte
2. gas permeable or impermeable (depend on situation)

18

True/False: plastic is a good container for samples used in analysis of POPs

False; will cause contamination (use glass instead, can rinse and recover)

19

Plastic is a good container for:

trace metal analysis samples

20

Can containers be reused?

yes; need to follow specific cleaning procedures with chemicals, high heat
(ideally use new ones each time, not always possible)

21

What happens during storage that might impact the results of analysis?

microbial spoilage, degradation
compounds disappear; new compounds might appear (not representative of original source)

22

compounds like PCBs have a high ____, so the sample would be less ____.

stability/half-life
time-sensitive

23

what parameters influence the chemistry and stability of toxicants? (4)

1. light -> photodegradation
2. temp -> thermal degradation
3. microbe activity -> microbial degradation, affect Aw, produce metabolites
4. pH -> denature, hydrolysis, etc

24

What can be done to extend storage life of sample? (4)

1. store @ low temp (refrigerate/freeze; be careful when thawing)
2. block light (keep in dark, use opaque container)
3. remove moisture (dry/free-dry)
4. add chem preservatives (alter pH, prevent microbes)

25

What are the issues with freezing and drying samples?

freezing: need to thaw again before analysis, time consuming
drying: need LOW TEMP for heat labile and volatile samples

26

What are mycotoxins?

toxins produced by molds/fungi; extremely toxic/carcinogenic

27

What are the main mycotoxin producing species? (3)

aspergillus, fusarium, penicillium

28

The main mycotoxin contaminated foods are:

cereals (wheat, corn, oats, etc) and peanuts

29

The fusarium species produce what types of toxins? What diseases are these implicated in?

fumonisins, zearalenones, trichothecenes
kashin-beck disease, mseleni joint disease

30

ochratoxins are produced by:
they cause:

penicillium, aspergillus
kidney damage (also possible carcinogen; group 2B)