lecture 2 Flashcards
what are the steps in analysis
- sampling (sample selection)
- sample preperation
- preform assay
- calculate and interpet results
what is a sampling plan and why is needed?
A sampling plan is a predetermined procedure for how selection, withdrawal, transportation and preperation of samples will be done. This is needed to ensure the results from the lab are a good representation of the population
what is the point of sampling in attribute plans?
It is done to decide if something is acceptble based on the presence or absence of a characterisic. It is a qualative analysis. Basically is it there or no, and it will either be conforming or non-conforming
what is the point of sampling in variable plans?
This is done to measure quantatitevly the amount of a substance. That measurement will then be compared with an acceptable value.
what are the type of sampling plans, and what makes them distinct from each other
- single sampling plans: only one sample will allow u to accept/reject,
- double sampling plans: same as single but this time 2 samples are taken
- multiple sampling plans: use more than 2 sample to reach a conclusion
- sequential sampling plans: won’t know how many samples u will have to take until in the moment, you take one sample and then analysi and decide if to reject, accept or take another sample
in drying which type of water are you removing?
free water is evaporated
what are the types of drying and explain each briefly
- sun drying: explained in the title, but not used in lab as not very practical as it takes a long time and requires the correct conditions
- oven drying: done at temperatures 60-65 degrees so must not be a heat sensitive sample
- vaccum oven drying: uses vaccum to allow moisture to evaporate at a lower temperature than usual
- microwave drying: electrogmanetic radiations create the heat that allows for the removal of moisture
- freeze drying: is a two step process where the product is frozen and then the ice is removed by sublimation
what are advantages of vaccum oven drying?
- higher drying rate
- lower drying temperature
- oxygen deficient processing enviorment
- maintains quality and nutritional value, specifically of dried fruits and veggies
why is microwave drying a good drying technique?
it is a faster process, that produces a better quality of dried material and does so at a lower cost
how do microwaves generate heat?
- microwaves enter the food: electromagentic waves create an electric field that changes direction rapidly
- molecules move: water and polar molecules rotate and vibrate to align with the changing electric field
- friction creates heat: molecules rubbing against each other generate heat, cooking the food
what is the efficiency of microwave heat dependent on?
the amount of water in the food. As water molecules are responsive to the electric fields generated by microwaves.
explain freeze drying (lyophilisation) in more detail)
- the food product will be froze
- ice is removed via sublimation: a vaccum pump will pull air out of the chamber, the water in the food will sublimate which means the ice is converted from solide to water vapor and then the water will be removed from the product.
what are the main advantages of freeze drying?
- preservation of unstable food samples
- safe drying for thermosensitive compounds
why do lipids prevent protien extraction?
lipids form a coating around protien molecules which creates a barrier that blocks the protien from interacting with extraction buffers or solevents making it harder to isolate protiens
how is defatting done?
using a solvent
how is lipid oxidation protection done?
- storing under nitrogen or vaccum
- antixidants as long as they don’t interfere with the analysis
- controlling storage conditions (dark)
- low temperature storage
which lipids are senstive to oxidative degradation?
unsaturated fatty acids (double bonds)
why would u wanna inactivate enzymes and how is it done?
u wanna inactivate because they may degrade the food components you are looking at. In terms of how its done, depends on the nature of the food but some ways include:
- heat treatment
- freezer storage
- changing pH
- salting out
- adding reducing agents for oxidative enzymes
how is microbial inhibition done?
- freezing
- drying
- chemical presevatives
- combo of methods
- what is the difference between health canada, canadian food inspection agency and agriculture food canada in terms of role?
- health canada: sets standards for nutritional quality and saftey
- CFIA: enforces health and saftey standards set by health canada
- AAFC: supports canadian agriculture, helping them understand regulatory requirments
what are the techniques of sample extraction?
- solid-liquid extraction
- liquid-liquid extraction
explain solid-liquid extraction (SLE)
is a separation process where specific compounds are extracted from a solid material by dissolving them into a liquid solvent. They are seperated using filtration or centrifugation and can be sped up by using microwave or ultrasound
explain liquid-liquid extraction
is a seperation process where a compound is transferred from one liquid phase to another liquid phased based on its differing solubilities in two immiscible liquids. An emulsion must be formed to promote transfer and allow the layers to settle
describe the polarity of chlorphyll a, b, beta-carotene, flavanoids
- flavanoids are polar
- beta-caratone is non polar
- chorphyl b is more polar than cholorphyl a because of its structure, both are not extremly polar tho
