Shelf life
22 important questions on Shelf life
What are temperature conditions to determine shelf life?
- Storage at room temperature
- Refrigerated storage: often microbiological food safety
Shelf life - 'Use by', what do you know?
- Often for products that need be stored between 0-6C
- When shelf life is less then 5 days
- Raw meat/fish, pre-cut vegetables
Shelf life - 'Best before', what do you know?
- Determined based on quality deterioration, not related to food safety
- coffee, canned, sterilised, frozen
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What can be External or Internal cause be of decay?
- External cause: Microorganisms
- Internal cause: Chemical reactions ( enzyme catalysis)
Cause: Off-flavor, Discooloration, textural change, loss of nutritional value
What is the definition of Shelf life and its critical factors ?
- Shelf life is the time during which a food remains acceptable for consumption
- Interplay between food, consumer and demands( legal, commercial)
- Critical factors: formulation, processing, packaging, storage
What are different Modes of food deterioration ?
- Microbiological changes
- Chemical changes
- Physical changes
Food deterioration: What are the possible physical(T) changes?
- Physical damage: bruising or breaking products
- Freeze/chilling injury
- Moisture transfer: e.g. Soggy cookies
- Mass transfer of food components:e.g. Sugar or fa crystallisation on chocolate
Food deterioration: What are the possible chemical(pH, oxygen, light) changes?
- Enzymatic action: Enzymatic browning when cutting fruit
- Oxidative reactions: e.g. Lipid oxidation
- Non enzymatic browning: e.g. Maillard reactions (bitter odour)
Food deterioration: What are the possible microbiological(T, pH) changes?
- Bacteria, moulds, yeasts, viruses, parasites (safety problems, undesirable sensory changes)
By what is Shelf life of food determined and influenced ?
- Determined by (bio)chemical, microbiological, physical changes
- Influenced by: Environmental conditions ( packaging, temperature, relative humidity, light)
How to measure Shelf life?
- Choose indicator for Quality deterioration(e.g. Color, oil separation)
- Measure Q-indicator as af function of storage time(> 6 time point)
- Set or obey limits ( legal limits for microorganisms)
- Determine end of shelf life
What are main messages 'Gura Case'?
- The mechanisms by which food spoils are often well known
- The biochemistry, chemistry and microbiology of food provide much of the root on which our current understanding of food spoilage and deterioration is based.
- Intrinsic and extrinsic factor influence how a food spoils
When is shelf life predictions possible?
- If microbial behaviour is known
- If reactions leading to quality loss are known
- If important conditions (pH, O2, RH) are as function of strorag condition
Then shelf life can be predicted by mathematical models
How to determine shelf life for real life situations?
- Conditions tha mimic those the product is likely to experience during strorage, distribution, retail display and consumer use
- Different conditions :
- Optimum
- Typical/average
- Worst case storage
How to Accelerated shelf life testing(ASLT)?
- Increased temperature
- Rule of thumb: retain rate increases 2-4 times for every 10C temperature increase
- Usually following Arrhenius/Q10 model
What is danger of extrapolation?
- When ASLT some reactions may be more prominent at higher temperature than at lower, or the other way around
Why it is important to control external conditions?
- Temperature as such has large influence
- Varying temperature in the food chai has a large impact on resulting quality
- Non-isothermal kinetics becomes very important, manly for microbial and chemical reactions
What type of testing can you use for shelf-life?
- Analytical test(product-oriented): difference discrimination tests
- Qualitative test, for example descriptive analysis
- Hedonic test (consumer-oriented): preference and acceptability test
- Defining Faulure criteria
Sensorial shelf life influenced by?
- Chemical, biochemical and microbial changes causing flavour changes
- Physical and biochemical changes causing texture changes
- Diffusion causing texture changes
- (sensorial shelf life is difficult to model)
What to know about empirical modelling of shelf life?
- Product do not fail exactly at same time
- You create ;probability model
- Failure time: when consumption becomes unacceptable
- Life of a product: when product performs satisfactorily
What does the Weibull model?
- Describe failure times that is shelf life
- It calculates the probability of a products failure by (threshold) parameters
What theme beyond measuring and modelling in shelf life?
- the consumer handling and use is a important shelf life influencing factor
- Must be done to improve consumer handeling and use of food
- Shelf life is determined on commercial circumstance, may be longer based on technological consideration alone.
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