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food toxicants and analysis > sampling & mycotoxins > Flashcards

sampling & mycotoxins Flashcards

1
Q

What needs to be considered when sampling?

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

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

A

No; foods are heterogenous.

diff compositions of parts will affect

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3
Q

What parts of a food should be sampled?

A 
edible portions (usually remove peel, dirt, shell, etc)
specific guidelines by CODEX ALIMENTARUS
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4
Q

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 ____.

A

lot; sublot

sampling

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5
Q

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

A

quantity taken from single place in designated lot/sublot

No; combine with other incremental samples to form AGGREGATE SAMPLE

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6
Q

The final product of the sampling procedure is a:

A

laboratory sample

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7
Q

A sample is considered to be representative if:

A

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

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8
Q

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

A

combining incremental samples taken from lot/sublot

representative of that lot/sublot

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9
Q

What are the two methods of sampling?

A

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

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10
Q

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

A

size of bulk food sample, heterogeneity

sample size

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11
Q

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

A

more; higher

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12
Q

What are the sources of uncertainty? (3)

A
  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)
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13
Q

How do we determine total uncertainty?

A

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

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14
Q

the 3 necessary precautions during sampling:

A
  1. sample traceability
  2. avoid contamination
  3. appropriate storage/transport
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15
Q

What is sample traceability and why is it important?

A
  • 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
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16
Q

the 3 main sources of sample contamination:

A
  1. from sampling container/equipment
  2. from another sample (transferred)
  3. exposure to environment (air, dust, etc)
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17
Q

How do you determine if a container is suitable?

A
  1. INERT to matrix & analyte

2. gas permeable or impermeable (depend on situation)

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18
Q

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

A

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

19
Q

Plastic is a good container for:

A

trace metal analysis samples

20
Q

Can containers be reused?

A

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

21
Q

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

A

microbial spoilage, degradation

compounds disappear; new compounds might appear (not representative of original source)

22
Q

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

A

stability/half-life

time-sensitive

23
Q

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

A
  1. light -> photodegradation
  2. temp -> thermal degradation
  3. microbe activity -> microbial degradation, affect Aw, produce metabolites
  4. pH -> denature, hydrolysis, etc
24
Q

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

A
  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
Q

What are the issues with freezing and drying samples?

A

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

26
Q

What are mycotoxins?

A

toxins produced by molds/fungi; extremely toxic/carcinogenic

27
Q

What are the main mycotoxin producing species? (3)

A

aspergillus, fusarium, penicillium

28
Q

The main mycotoxin contaminated foods are:

A

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

29
Q

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

A

fumonisins, zearalenones, trichothecenes

kashin-beck disease, mseleni joint disease

30
Q

ochratoxins are produced by:

they cause:

A 
penicillium, aspergillus
kidney damage (also possible carcinogen; group 2B)
31
Q

which of the mycotoxins is a certain carcinogen?

What produces them, and what are the types?

A

Aflatoxins
produce by aspergillus
types: B1, B2, G1, G2, M (metabolite)

32
Q

What effects can aflatoxins have on human health? (6)

A 
liver cancer
reye's syndrome
childhood cirrhosis (liver bleeding)
chronic gastritis
kwashiorkor
respiratory syndromes
33
Q

The most commonly detected mycotoxin in canada is:

A

deoxynivalenol (a trichothecene)

34
Q

What is the ML for aflatoxins in food and animal feed (canada)?

A

food: 15 ppb

animal feed: 20 ppb

35
Q

What methods of analysis can be used for mycotoxins? (3)

A

HPLC-FLUO
HPLC-MS/MS
ELISA

36
Q

The ____ property of some mycotoxins allows for the use of HPLC coupled to _____.

A

fluorescent

FLUO

37
Q

true/false: ELISA analysis method requires more preparation steps than HPLC methods for mycotoxins

A

False; doesn’t require cleanup and concentration, can analyze directly after extraction

38
Q

What method is used to extract mycotoxins? (2)

A

SPE

Solvent extraction

39
Q

The 3 types of ELISA:

A

direct
indirect competitive
“sandwich” capture assay

40
Q

What are the pros and cons of ELISA?

A

pros: easy, fast, less preparation
cons: higher LOD (may be too close to reg limit)
* sensitivity/selectivity varies

41
Q

The ___ the sample, the more likely it is representative.

A

larger

42
Q

What is a particular concern when sampling for mycotoxins?

A

non-homogenous toxin distribution (toxin could be concentrated in select area)

43
Q

Sample size will vary depending on ____ for mycotoxins.

A

lot size

regulations in place for determining minimum sample size

44
Q

How are samples collected from grains for mycotoxin analysis?

A

taken from boxcar with PROBE (hollow tube, extend deep to take from all levels)
take incremental samples
various probing patterns possible - 7 probe, 9 probe, etc - distributed over area of boxcar
aggregated into 1 sample

food toxicants and analysis (11 decks)

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