Accelerated Shelf life

This is an indirect method and attempts to predict the shelf life of a product without running a full length real time storage study. This kind of study is useful especially for new products and products having a long shelf life. The method involves storing the product under accelerated storage conditions like high temperature, agitation and humidity. As a result the end of shelf life is achieved quickly and the product is ready for sale in a relatively short period.

The results obtained from the accelerated studies are extrapolated to get the real time shelf life. However it has been proved that accelerated studies may under-predict or over-predict the real shelf life. Therefore when such studies are carried out it is generally recommended that a ‘conservative’ shelf life should be reported at first which can then be modified, once the real time shelf life data becomes available. Thus food manufactures are advised to run real time study along with accelerated study to arrive at an appropriate shelf life for their product.

During both types of studies the product is tested at periodic intervals to check when the spoilage begins. It is advisable to make a neat calendar schedule of the shelf life study plan with the sampling carried out at the beginning (zero day), at the end and between regular intervals. Selection of a season which would most likely harm the product should be chosen. In a country like India, the study should be started and run throughout the summer and rainy season. Any product that passes the study at these seasons will most likely pass the shelf life study done at any time throughout the year.

Processed Food Deterioration

The principal mechanisms involved in the deterioration of processed foods are as follows:

• Microbiological spoilage sometimes accompanied by pathogen development.
• Chemical and enzymatic activity causing lipid breakdown, color, odor, flavor, and texture changes.
• Moisture and/or other vapor migration producing changes in texture, water activity and flavor

Formulation and processing variables which affect these mechanisms and which can be used to control deterioration include: (1) moisture and water activity (2) pH; (3) heat treatments; (4) emulsifier systems; (5) preservatives and additives; and (6) packaging.

Principle of Accelerated Shelf Life Study?

Shelf-life studies can come in many different forms, including accelerated studies. In these studies, accelerated conditions (i.e. elevated temperature) are applied to eligible products to predict product shelf-life at typical storage conditions. This process is performed using the Q10 value. The Q10 value of a product is the temperature quotient for a 10°C temperature difference, as expressed in the equation below:

Typically, a Q10 value of 2 is used as an initial shelf-life estimate, but this may not represent the actual acceleration factor of a specific food product.  It is recommended that accelerated shelf-life studies be accompanied by a shelf-life study conducted under normal storage conditions in order to determine the actual Q10 value.  This approach allows for a more specific Q10 value and can be used for future accelerated shelf life studies on similar products.

The most prominent spoilage concern for products eligible for accelerated shelf-life studies is rancidity.  Rancidity is a chemical change in the product that occurs in a number of ways, depending on ingredients and packaging.

Limitation of accelerated shelf life studies:

• Accelerated stability studies are valid only when the breakdown depends on temperature.
• Accelerated stability studies are valid only the energy of activation is about 10 to 30 kcal / mol. In solution phase most reaction has heat of activation in the range of 10 to 30 k.cal / mole. if energy of activation is less than 10 kcal / mol its rate would be fast at room temperature .in such cases elevated temperature has little influence on the decomposition .if energy of activation is higher than 30 kcal / mol very high temperature are required to enhance the degradation . Reaction at such high temperature may not have any relevance, because they do not reflect ambient storage condition
• The result obtained for one set of condition for a preparation cannot be applied to other preparation of same food.
• Stability studies are meaningless when the product looses its physical integrity at higher temperature like coagulation of suspending agent, denaturation of proteins

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