Procedures for determination and monitoring of shelf life

Direct shelf life determination requires batches of samples to be taken at significant stages in the development or modification  of the product. These  samples should be examined during storage, usually under controlled environmental conditions, until their quality becomes unacceptable. The time when this occurs is the maximum product shelf life, and therefore the determination necessarily requires at least this time to complete.  
 
Significant sampling stages within the programme of shelf life evaluation include:

1.  The successful experimental kitchen or pilot plant batch. At this stage it is possible to investigate formulation, process or packaging changes to improve the shelf life without the costs of factory time and material quantities.

2.  The successful full scale factory batch. This is the most important sampling stage.This will provide the data for the setting of shelf life and specification standards.

3.  The first continuous production trial. Examination of products should confirm the data from earlier samplings.
 
As part of an on-going surveillance system, samples should be taken at suitable intervals for storage trial. The sampling interval should typically be 20% of the shelf life which will provide samples of 6 different ages from fresh to full shelf life. For long life products more frequent intervals may be useful to detect any changes in storage performance (e. g. every two months for a two year shelf life Shelf life samples should be subjected to conditions effectively simulating the normal storage and distribution conditions the food is likely to encounter.Shelf life examination is done by employing appropriate methods of: sensory evaluation; chemical analysis and microbiological analysis.  
 
In sensory evaluation appearance, smell, texture and flavour being the main attributes to assess. Such assessments are frequently inexact as there may not be a suitable control sample with which to compare the stored samples, this being particularly so for new products. However, under appropriate test conditions using control sample it is possible to get a fair idea about the quality and acceptability of stored products.
 
Quantitative measurements, for example of colour, texture, viscosity and amount of water or oil separation should be included if they either closely relate to the sensory quality or can be used as reliable indicators of quality deterioration.
 
In addition to subjective assessments, other  tests may be necessary. These may include tin content of products in unlacquered cans, vitamin content where a claim is made. Microbiological examination of fresh and stored products is highly essential in order to determine whether they are safe for human consumption.