Shelf Life and Accelerated Shelf Life Testing

Shelf life is defined as “the period of time during which the food product will remain safe; be certain to retain desired sensory, chemical, physical, microbiological and functional characteristics; and comply with any label declaration of nutritional data when stored under the recommended conditions” by IFST [1]. 
Shelf life is vital for food products because it informs consumers about the time period in which the food product is acceptable in terms of its safety and quality. The shelf life of food is affected by three factors: food product characteristics (aw, pH, enzymes, reactive compound concentrations, perishability), packaging properties (water vapor transfer, light transmission, package/product interactions, surface area: volume ratio), distribution and storage conditions (temperature, humidity) [2]. 
There are several testing methods to determine the shelf life of food products. One of these methods is accelerated shelf-life testing (ASLT). ASLT is used to shorten the time required to estimate a shelf life, which otherwise can take an unrealistically long time to determine. It is based on exposing the food product to one or more of the enhanced extrinsic factors like temperature, humidity compared to standard conditions and accelerating the rate of the selected deteriorative reaction(s) such as lipid oxidation, color change, nutritional loss, microbial spoilage [2]. ASLT can be applied to dehydrated products, frozen foods, canned foods, oxygen-sensitive products, oxygen-absorbing package, and long-duration spaceflight foods [2]. To perform ASLT, the following procedures should be adopted [2,3]: 

1. Determination of the microbiological safety and quality parameters of the selected food product. 
2. Selection of the critical deteriorative reactions that will cause quality loss 
3. Selection of the most cost-effective packaging material 
4. Selection of the extrinsic factors that are to be accelerated 
5. Determination of the duration and frequency in which the product must be held at the selected extrinsic factor 
6. Calculation of the number of samples to be stored at each test condition 
7. Construction of shelf life plots with each test storage condition 
8. Estimation of the shelf life under normal storage conditions by extrapolation using the data obtained from ASLT. 

Even though ASLT is a very useful tool in shelf life estimation, it is prone to potential problems and theoretical errors. Therefore, ASLT results should always be confirmed by conducting shelf-life tests under actual conditions. After establishing a relationship between ASLT and actual shelf life, ASLT can be used for that food product safely [2].

1. IFST (1993). Shelf Life of Foods: Guidelines for Its Determination and Prediction. Institute of Food Science and Technology, London. 

2. Robertson, G. L. (2012). Shelf Life of Foods. Food Packaging: Principles and Practice (3rd ed.) (pp. 329-365). Boca Raton, FL: CRC Press. 

3. Phimolsiripol, Y., & Suppakul, P. (2016). Techniques in Shelf Life Evaluation of Food Products. Reference Module in Food Science. (pp. 1-8).