Aug 31, 2026 - Foods
The microbiology of shelf life – what actually happens during the best-before period?
A food product is produced, packaged and given a best-before date (BBD). But what actually happens between production and the expiry of the BBD? Microbiologically, time does not stand still: depending on the product and storage conditions, existing microorganisms can multiply, remain stable, or die off.
The BBD describes the period during which a food product should retain its specific characteristics under appropriate storage – it is therefore not equivalent to an expiration date. For microbiological shelf life, various factors are decisive, including temperature, pH value, water activity (aw value), salt and sugar content, preservatives, packaging, production process, initial microbial load and storage duration.
Particularly relevant: Listeria monocytogenes
An example of the importance of storage conditions is Listeria monocytogenes. The pathogen can multiply even under refrigerated conditions and is therefore particularly relevant for certain ready-to-eat foods. A test immediately after production therefore does not automatically indicate how the product will develop microbiologically until the end of its shelf life.
This is where shelf-life studies, storage studies and, if applicable, challenge tests come into play. Under defined conditions, these investigate whether and how relevant microorganisms can develop during the intended shelf life. Among other things, this allows assessment of whether and how quickly growth begins and how strongly the microorganisms subsequently multiply.
A sound shelf-life assessment therefore takes into account the interaction of product formulation, production process, microbiological characteristics, packaging and storage conditions. The EU Regulation (EC) No 2073/2005 also takes these factors into account when assessing microbiological shelf life.
The BAV Institute supports manufacturers in the microbiological assessment of foods and questions relating to shelf life. With targeted analyses, storage studies and further microbiological tests, we help to evaluate product stability on a sound basis and to ensure product safety throughout the entire shelf life.
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