The shelf-life limits of some of the factors mentioned in the definitions are defined at a laboratory level without the intervention of the consumer. For example, a central issue in declaring a food to be safe is that it must be free of pathogenic bacteria and this can be assessed by standard microbiological analysis. Another example is vitamin D-enriched milk, which must comply with a certain concentration measured in an analytical laboratory. In the shelf-life definitions the limit to sensory properties is

referred to as acceptable/unacceptable or desired or intended. These limits can be highly ambiguous if not thoroughly researched. Manufacturers who have to comply with food regulations and, more importantly, comply with quality standards, need practical and reliable methods to estimate the shelf lives of their products.