Stability studies on pharmaceuticals were covered in an earlier article. Foods constitute another important area and are essential for sustenance of human and animal life. The present article covers some of the physico-chemical changes that take place in foods resulting in their deterioration.
Used by date Vs Best before date
Today superstores are flooded with large variety of synthetic foods to cater to the choice and taste of consumers. Such foods bear labels which mention date of manufacture, use by date or best before date. Use by date and best before date are not well understood and often confuse the consumer.
Best before date is mentioned on food articles which deteriorate outwardly affecting consumer acceptance but without affecting consumer health and safety. Foods with a shelf life of a minimum of two years are not required to display a best before date.
Use by date is a time limit set by the manufacturer for consumption of the food items for reasons of consumer health and safety.
Physical, chemical and microbiological studies are required to be conducted on several batches of finished products and contamination factors established also in relation to packaging and storage condition variations before deciding on the above described dates.
Factors responsible for processed food deterioration
The main factors which lead to deterioration of processed foods are:
- Moisture gain or loss producing changes in texture, hardness, microbial growth and colouration
- Chemical and enzymatic activity resulting in colour, odour and texture changes
- Microbiological spoilage
Role of water activity
Water activity refers to the amount of free water present in a product that is available for microbial growth. The gain or loss of moisture depends on factors such as hygroscopicity of the product, temperature and relative humidity. In packaged foods the changes are relatively lower.
Microbiological deterioration and possibility of growth of pathogens is dependent on the availability of moisture, pH of media, temperature and presence of required nutrients. Shelf life can be extended by exercising control on these conditions. Inoculation with various spoilage organisms and observing growth of pathogens can help control such harmful bacterial growth
Oxidation of lipids results in product before deterioration and can be prevented by conducting accelerated stability tests.
Degree of unsaturation in fats leads to higher degradation due to increased reactivity.
Lipase enzymes cleave fatty acids from triglycerides and the free fatty acids add to the odour and bitter taste thereby making the food unacceptable.
Photo- oxidation reactions during storage can result in the formation of hydroperoxides which break down to peroxides. The peroxide value can be estimated in a fat or oil by quantitating the aldehydes which helps estimate the extent of fat or oil degradation. The aldehyde n-hexanal can be estimated at low concentration levels using GC – Headspace technique.
Stability of cosmetic products for safety of use and factors governing their degradation will be discussed in subsequent article.
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