shelf life Flashcards
what does shelf life mean
The period in time when a product is considered acceptable
types of chemical, physical and biological changes in food of shelf/life
Enzymatic reactions, dehydration/re-hydration, chemical reactions – Millard browning, oxidation, and microbial growth
who controls the best before dates and use by dates
Food Standards Australia New Zealand: Standard 1.2.5
What do ‘used by dates’ and ‘best before dates’ mean
used by dates - Foods that must be eaten before a certain time for health or safety reasons - food cannot be legally sold after this date
best before dates - The food product is safe to consumer, but the producer cannot guarantee that it will meet the consumers expectations – it may be lacking in quality
Discuss the requirements needed for a ‘limiting criteria’ in the context of shelf life determination
Specific, quantifiable, constant impact to measure changes, identify either best before or use by date!
Characteristics need to be specific (a clear chemical, microbial or physical link needs to be made), quantifiable (need to have numbers), and have a constant impact on the product if we want to model changes in the criteria. We also need to be able to identify whether it is quality or safety concerns (best before or use by date). Determination of criteria may require preliminary trials.
how to define an acceptable limit for that criteria
acceptable limit - how bad can you let it get before it is considered unacceptable. a specific value (critical limit) needs to be identified - For food products with multiple applications the acceptable limits may be different depending on the use
factors affecting deterioration in food once brought from shop
affected by: storage conditions – temp, humidity, light exposure
Packaging – what happens once the packet is open
Product variation
what is direct testing
replication of the most likely storage conditions
Suitable for perishable foods with a short, expected shelf life
Minimal experimental design required
Accelerated shelf life studies
elevated temperatures to speed up chemical and biochemical reactions
Using modelling we are able to extrapolate the expected shelf life of the product
Suitable for products with a long expected shelf life
Requires a lot of planning and sampling
what is kinetics
The study of how reactions occur over time. Rate = change/time
what is the correct equation for 1st order relations
[Xt] = [Xo]e -kt (includes an e and doesn’t has a space between the k and t… the k and t are also where you would put squared number
what is the correct equation for 0 order reactions
[Xt] = [Xo] -k t (has a space between k and t and also has not e
Identify the differences between 0 and 1st order reactions
0 order reactions refer to linear line, the rate of the reaction is independent of the concentration of the reactant, useful for predications over a long period of time
1st order reaction refers to curved line dependant on the concentration of the reactant.
why is kinetics of shelf life reactions important
to use our understand of kinetics to predict shelf life of a product
