Evaluation of food quality

A common practice employed to evaluate the shelf life of a given food product is to determine changes in selected quality characteristics over a period of time. One may consider quality of a food as a gross measure of the food deterioration occurring in food item. However, it should be recognized that the term quality is meant to encompass 

several quality attributes or characteristics. From a consumer's standpoint, the sensory expectations derived from the presence (or  absence) of desirable (or undesirable) characteristics of a given food determine the quality of a product. Therefore a food product noted for its high quality has more of the desirable characteristics.
 
Empirical or analytical techniques may be used to quantify the quality attributes of food. For example, enumeration of microbes or determination of chemical components of a product are analytical techniques, whereas the human subjects to monitor changes in the magnitudes of quality characteristics constitute empirical techniques.