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TOPIC 2: FACTOR AFFECTING QUALITY AND SHELF LIFE - Coggle Diagram
TOPIC 2: FACTOR AFFECTING QUALITY AND SHELF LIFE
DEFINITION
The Institute of Food Science and Technology (IFST) Guidelines (1993) provides a definition of shelf life: ‘shelf life is the period of time during which the food product will remain safe or be certain to retain desired sensory, chemical, physical and microbiological characteristicsnand comply with any label declaration of nutritional data.’
This definition encapsulates most perspectives and leaves some flexibility, i.e. ‘desired ... characteristics’, in assigning product shelf life. This is essential because once safety considerations have been met, quality is generally a commercial consideration dependent upon the companies' marketing strategy.
FACTORS AFFECTING PRODUCT QUALITY AND SHELF LIFE
For many foods, the product shelf life is limited by specific or ‘key’ attributes that can be predicted at the time of product development. This is either on the basis of experience of similar products or observations of them, or from a consideration of:
the make-up of the product (intrinsic factors)
the environment that it will encounter during its life (extrinsic factors)
the ‘shelf life limiting processes’ that this combination of intrinsic and extrinsic factors is likely to result in
Intrinsic factors are the properties resulting from the make-up of the final product and include
the following:
• water activity (Aw) (available water)
• pH/ total acidity; type of acid
• natural microflora and surviving microbiological counts in final product
• availability of oxygen
• redox potential (Eh)
• natural biochemistry/chemistry of the product
• added preservatives, e.g. salt, spices, antioxidants
• product formulation
• packaging interactions, e.g. tin pickup, migration
Selection of raw materials is important for controlling intrinsic factors, since subsequent processing can rarely compensate for poor-quality raw materials. Extrinsic factors are a result of the environment that the product encounters during life andinclude the following:
• time–temperature profile during processing
• temperature control during storage and distribution
• relative humidity (RH) during storage and distribution
• exposure to light (UV and IR) during storage and distribution
• composition of gas atmosphere within packaging
• consumer handling
SHELF LIFE STUDY
The interactions of intrinsic and extrinsic factors affect the likelihood of reactions or processes affectin shelf life. For ease of discussion, these shelf life limiting reactions or processes can be classified as: chemical/biochemical, microbiological and physical.
CHEMICAL/BIOCHEMICAL PROCESSES
OXIDATION
A number of chemical components of food react with oxygen affecting the colour, flavour, nutritional status and occasionally the physical characteristics of foods.
ENZYME ACTIVITY
Fruits and vegetables are living commodities and their rate of respiration affects shelf life
The greater the rate of respiration, the shorter the shelf life
Immature products such as peas and beans, have much higher respiration rates and shorter shelf life than products that are mature storage organs, such as potatoes and onions
MICROBIOLOGICAL PROCESS
EXAMPLES WHERE PACKAGING IS KEY TO MAINTAINING MICROBIOLOGICAL SHELF LIFE
Heat processing that kills microorganisms is a widely used means of achieving safe products and extending shelf life
In canning, food is filled into a container that is hermetically sealed and sterilised at 121◦C
The size and shape of the container is important.
Retort pouches are flat in shape so processing
time can be reduced compared to a conventional cylindrical can and the reduced processing time
generally results in improved taste and texture
PHYSICAL AND PHYSIO-CHEMICAL PROCESS
PHYSICAL DAMAGE
The formulation of the product must be sufficient to tolerate such shocks or extended periods of vibration, e.g. emulsions must be stable enough to withstand vibration and the packaging must be able to withstand and protect against such forces.
INSECT DAMAGE
Insect infestation can occur at any point after manufacture, e.g. extended storage periods or during shipment.
MOISTURE MIGRATION
Hygroscopic foods require protection from moisture take-up, which in dry products such as breakfast cereals and biscuits causes loss of texture, particularly crispness.
BARRIER TO ODOUR PICK UP
Chocolate products because of the high fat content and sometimes bland flavour, if inadequately wrapped and stored next to strong smelling chemicals, such as cleaning fluids, or in shops close to strongly flavoured sweets, such as poorly wrapped mints, can result in unacceptable flavour pick-up
FLAVOUR SCALPING
If a chemical compound present in the food has a high affinity for the packaging material, it will tend to be absorbed into or adsorbed onto the packaging until equilibrium concentrations have been established in food and packaging.
FLAVOUR SCALPING
If a chemical compound present in the food has a high affinity for the packaging material, it will tend to be absorbed into or adsorbed onto the packaging until equilibrium concentrations have been established in food and packaging.
MIGRATION FROM PACKAGING TO FOODS
MIGRATION FROM PLASTIC PACKAGING
A typical modern plastic packaging material may comprise many different constituents, which all have the potential to result in safety and/or quality problems if the material is poorly designed or there are errors in the manufacturing procedure.
All polymers contain small quantities of residual monomers left unreacted from the polymerisation reaction.
Adhesives used to seal packaging can also be a source of migrating constituents. Common types of adhesive for use in food packaging are hot melt, pressure sensitive, cold seal, water based, solvent-based, solvent-free, acrylics and polyurethane
MIGRATION FROM OTHER PACKAGING MATERIALS
Paper and board has been used to package food products for many years.
A number of taint problems in foods have been attributed to paper and board
Chlorophenols can be responsible for antiseptic taint.
Migration from can lacquers into canned foods has been another area of concern over recent years. The migrants considered to pose the greatest health concern are the monomers bisphenolA and bisphenol-F, and their diglycidyl ethers, known as BADGE and BFDGE, respectively.
FACTORS AFFECTING MIGRATION FROM FOOD CONTACT MATERIALS
the quantity of available potential migrants in the packaging material itself is of paramount importance
The degree of contact between food and packaging also has a direct influence on migration, and in cases where particular problems have been encountered
PACKAGING SELECTION TO AVOID MIGRATION AND PACKAGING
The potential for taints can be evaluated by considering three questions
• the composition of the packaging material – is it optimize to minimise the quantity of potential migrating components that are available to migrate into food?
• what is the probability that any available migrating components might migrate into the food – this will depend on the composition of the food, which determines the affinity of migrants for the food matrix.
• what impact is the migrating compound likely to have on the product? This is influenced by how strongly flavoured the product is.
METHODS FOR MONITORING MIGRATION
Sensory assessment - a panel assesses a product to determine whether contact with the packaging has affected sensory properties.
• Advantages - the relative ease with which a panel can be assembled and trained
• Disadvantages - the inability to diagnose identified problems.
Chromatographic method - used to identify differences between a suspect packaging sample and a reference sample.
REFERENCES
Brown, H., Williams, J., & Kirwan, M. (2011). Packaged product quality and Shelf Life. Food and Beverage Packaging Technology, 59–83.
https://doi.org/10.1002/9781444392180.ch3
Anon. (2013). Home. Bhaskaracharya College of Applied Sciences. Retrieved January 5, 2023, from
https://bcas.du.ac.in/