sampling & mycotoxins Flashcards
What needs to be considered when sampling?
- need to be representative (consider size, homogeneity)
- prevent contamination
- prevent degradation
- prevent mixing and losing data
Are toxicants present in the same levels in parts of a food?
No; foods are heterogenous.
diff compositions of parts will affect
What parts of a food should be sampled?
edible portions (usually remove peel, dirt, shell, etc) specific guidelines by CODEX ALIMENTARUS
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
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
The final product of the sampling procedure is a:
laboratory sample
A sample is considered to be representative if:
it reflects the properties of interest of the lot from which it was taken
An aggregate sample is derived from _____, and considered to be:
combining incremental samples taken from lot/sublot
representative of that lot/sublot
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
____ and ____ will determine the sampling method, and the ______
size of bulk food sample, heterogeneity
sample size
the (more/less) heterogenous the bulk food, the (higher/lower) the variability, and so the greater the sample size needed
more; higher
What are the sources of uncertainty? (3)
- external operations (packing, shipping, storage of sample)
- prep of lab sample (sub-sampling, prep and processing)
- analysis (extraction, cleanup, derivativisation, evap, instrument)
How do we determine total uncertainty?
total uncertainty (Sres) is square root of sum of squares for each uncertainty source
the 3 necessary precautions during sampling:
- sample traceability
- avoid contamination
- appropriate storage/transport
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
the 3 main sources of sample contamination:
- from sampling container/equipment
- from another sample (transferred)
- exposure to environment (air, dust, etc)
How do you determine if a container is suitable?
- INERT to matrix & analyte
2. gas permeable or impermeable (depend on situation)
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)
Plastic is a good container for:
trace metal analysis samples
Can containers be reused?
yes; need to follow specific cleaning procedures with chemicals, high heat
(ideally use new ones each time, not always possible)
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)
compounds like PCBs have a high ____, so the sample would be less ____.
stability/half-life
time-sensitive
what parameters influence the chemistry and stability of toxicants? (4)
- light -> photodegradation
- temp -> thermal degradation
- microbe activity -> microbial degradation, affect Aw, produce metabolites
- pH -> denature, hydrolysis, etc
What can be done to extend storage life of sample? (4)
- store @ low temp (refrigerate/freeze; be careful when thawing)
- block light (keep in dark, use opaque container)
- remove moisture (dry/free-dry)
- add chem preservatives (alter pH, prevent microbes)
