Abstract
Shelf life can be simply defined as the duration of that the food remains acceptable for consumption. Determining shelf life of a product, thus, has become essential in quality control because consumer’s demands for safe and high quality products have increased. Accelerated shelf life testing (ASLT), which subjects the food to environments that are more severe than normal to speed up the deterioration process, has long been used in shelf life studies because it can help make decisions more quickly by minimizing time and it minimizes costs. The criterion used to determine shelf life can be the changes in either physical, chemical, biological or sensory characteristics.
 This study used sensory descriptive properties as the primary criteria to investigate the validity of using Accelerated Shelf Life Testing (ASLT) to determine shelf life of four extruded fortified blended foods (FBFs) compared to a real time model. The real-time environment was set at 300C and 65% relative humidity, based on the weather in Tanzania, the expected location of product use. The ASLT environment was at 500C and 70% relative humidity based on a Q factor of 2, which was equivalent to a one-week ASLT equals onemonth real time. The samples were evaluated for aroma and flavor by a highly trained descriptive panel for 3 time points in each shelf life model. Among the eighteen attributes tested, rancid and painty were the main sensory criteria to determine the shelf life of the products.
 The ASLT shelf life predictive model was consistent with the real time shelf life for three of the samples. However, it failed to predict the real time shelf life of the fourth similar sample. This affirms the essential use of real time modeling in shelf life study for a new product, even when an accelerated model has been developed for other similar products in the same category. ASLT testing can still be used, but only for early guidance or after validation.
Highlights
The quality of most foods and beverages decreases over time
The Accelerated shelf life testing (ASLT) shelf life predictive model was consistent with the real time shelf life for three of the samples. It failed to predict the real time shelf life of the fourth similar sample. This affirms the essential use of real time modeling in shelf life study for a new product, even when an accelerated model has been developed for other similar products in the same category
Labuza and Schmidl [2] took into account the variation in consumer perception of quality to define shelf life as “the duration of that period between the packing of a product and the end of consumer quality as determined by the percentage of consumers who are displeased by the product”; whereas, the Institute of Food Technologists (IFT) in the United States overlooked the fact that consumers might store the product at home for some time before consuming as they defined shelf life as “the period between the manufacture and the retail purchase of a food product, during which time the product is in a state of satisfactory quality in terms of nutritional value, taste, texture and appearance” [3]
Summary
The quality of most foods and beverages decreases over time. There are various definitions of shelf life in food technology literature reflecting different stand points. The microbiological characteristics are often the determining factors for its shelf life; no sensory data are needed [4]. The shelf lives of such foods become limited by changes in their sensory characteristics [5]. Sensory shelf-life estimation of foods has recently become increasingly important and resulted in a need for development and applications of new methodologies [6]. Et al [6] reported that the numbers of articles included in Scopus database including the words shelf-life and food in their title, abstract or keywords has increased 3 times from 2002 to 2011
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