Hurdle technology in food preservation

Most of the food products in the market are preserved (i.e. retained its stability) based on more than one hurdle or preservation method. In order to determine the food stability, two questions need to be asked: what target attribute(s) needs to be achieved in the microbial, chemical, bio-chemical and physical changes; and what is the required time frame of stability? When considering stability, the microbial and chemical safety aspects must be considered first before sensory properties. The microbial stability and safety of the most traditional and novel foods is based on a combination of several preservation factors (called hurdles), and the microorganisms present in food are unable to overcome. This is illustrated by the so-called hurdle effect, first highlighted by Leistner (1978). The critical limits are being used by the industry when each hurdle such as heat treatment, water content, pH and storage temperature is applied alone. Fundamental based theoretical concepts of F-value (hurdle: heat treatment), water activity (hurdle: water content) and glass transition (hurdle: glassy state; depending on water, storage temperature, and structure) are the most successful in determining food stability during food processing and storage. These concepts (i.e. each hurdle) are usually applied to specific types of products, for examples F-value to canned foods (i.e. high moisture); and water activity and glass transition for dried and frozen foods. The F-value is based on commercial sterility, water activity by state of water (i.e. bound or free) and glass-rubber transition by structural mobility. However, more than 60 hurdles may involve in food preservation (Leistner 2000a). The details of the important hurdles used in establishing food stability are discussed in the IFT/FDA Report (2003) and Leistner (2007).